103in Morane-Saulnier A.1 guide

The beginning – introduction

Stories have beginnings, middles, and ends and this one is no different. So I’ll begin at the beginning since it seems appropriate.

The beginning is basically to do with a fellow reaching out to discuss servos for a Fokker V.25, a failed entrant into the German 1918 fighter competition. It’s only when (nearly two years later) we took a side jaunt into a model he’d bought 2nd hand (this, necessarily, meaning a model someone else built) that we get to the purpose of this article.

With ‘this’ being the gorgeous Balsa USA Morane-Saulnier A.1, which at 103in wingspan, is a majestic thing of beauty. And not just in the air but on the ground, also!

Thing is, the BUSA Morane-Saulnier A.1 model he bought was in dire need of servos because the last guy had been flying it with old school analog servos. Which ones? Doesn’t really matter.

What does matter is this . . . while they worked fine on the workbench, during the very first flight he came to hold the opinion they simply had to go. They didn’t meet his expectations.

So he called for my opinion, but in all honesty, he didn’t need it. Why not? Simple, because he already knew what to get. Essentially, he just wanted confirmation (and to yak a little bit and catch up as we’re both queer for old cars). In fact, he and his Dad, John (below) have matching MGB sports cars!

As to which servos? Same as for his Fokker V.25 build (and as close to a universal recommendation for a +100in scale model as I make). We’re speaking of our DS360DLHV standard class servo (more later) also usually equipped with a PDRS25-25T alloy servo arm.

And if this were all there is to the story you could stop reading right here. Your loss if you do because, I know you checked in to learn about a cantilever-wing French parasol fighter, and here I am yapping about some Dutch Fokker V.25, but if you roll with me, you’ll discover an interesting prelude to your Morane-Saulnier A.1 build . . . trust me.

And it’s not like there’s any rush, especially if you’re still at the box of balsa and plans stage of things.

Fokker V.25

So in case you’re unaware (and I’ve been a modeler +50 years and had never even heard of the V.25, so no shame in not knowing), the V.25 was last in a series of low-wing cantilever-wing monoplane Fokker fighter designs. In fact, it was actually one of several Fokkers entered into the 1918 trials.

Major point being, these were plywood-covered wing experiments a mere 15 years since Orville and Wilbur had showed the world powered flight was possible. And while Wright brothers had used a strut and wire braced open-structure, with warping as the means of roll-control, by 1918 designers were experimenting with stressed skins and using ailerons! Think Glenn Curtis invented ailerons? Think again – maybe follow this link when you have time.

Anyway, these aircraft were created by the German, Reinhold Platz, for Dutchman Anthony Fokker’s eponymous aircraft company, Fokker. And as a further bit of trivia to do with this particular series, they began with the mid-wing V.17 evolved it to the low-wing V.25, then skipped the V.26 before iterating further and arriving at the V.27, These, all cantilever wing monoplanes, used a mix of D.7 and D.8 fuselages because, why reinvent the wheel?

And the last version looked nothing like the first!

Frankly, the evolution of aircraft was astonishing at this point in time. For example, the V.25 took a mere two weeks to go from concept to flight! Anyway, if you’re wondering, with regard to the V.25, we’re talking about an aircraft, which looked something like this!

So what’s this Fokker V.25 got to do with a Morane-Saulnier A.1, which is such a well known WWI parasol fighter, Balsa USA kitted it?

Not much, other than they’re both cantilever-wing monoplanes from an era when strut-braces and flying-wires (think Dr.1 and Sopwith Camel) were how designers kept the crates from falling apart under the stresses of flight. Point being, cantilever monoplane plays a role in all this because WWI had supercharged the state of the aircraft designer’s art and we (humanity) were making great leaps and strides.

What else plays a role? Well, Bob and Tina Patton (pictured above) are pivotal because if it weren’t for Bob’s Fokker V.25 models (he has two), then Whit wouldn’t have begun building one. And absent ‘that’ event, then maybe there’s never an outreach to ProModeler for servos to begin with!

Whit? Who’s he, and where does he come into this? Well, he’s the fellow who got the ball rolling by buying a 2nd hand Morane-Saulnier A.1 at an estate sale. His surname is Philbrick, and he’s a retired jarhead residing in the Volunteer state.

No, not that this especially matters but it’s because of his ongoing love affair with the Fokker V.25 (Bob’s fault, remember), that just after Thanksgiving 2022, he bought his first set of DS360 servos from us. Point being, later, when he picked up the Morane-Saulnier from an estate, he reached out to me once again for servos.

Servos! And at last, we’re getting to the crux of the matter, this BUSA model and the avionics for getting it into the air. But avionics, distinct from just the servos.

Before we get into that, join me in another birdwalk. This time regarding sources of information. Things like Wikipedia, various websites, and forums like RCU and RCSB for delving into the past.

Delving into the past

By now, maybe, you’re just a ‘little’ bit curious about the Fokker V.25, and if you are, then there’s something of a problem. This is because these things were being created more than 100 years ago.

I’m talking about the dark ages. Back when we had no Internet. Also predating social media like Facebook, with which to keep each other apprised these days.

And while back then many barely had electricity (and indoor toilets were scarce in many places), photography was surprisingly developed. This, because George Eastman had already founded his company, Kodak (1888).

In fact, since 1914 Kodak was synonymous with snapshot photography, so we’re talking about a far cry from the Civil War techniques using glass plates and chemicals! But while we had easy photography back then, what was missing was photograph distribution.

And today, with the Internet, distribution is what we have in spades! Hence the popularity of Facebook and Instagram, plus forums and articles like this, which without photos would be a rather dry wall of text.

Wikipedia

So this is the one and only V.25 photo I’ve found. And yes, looks like what Bob modeled. Moreover, while I’m sure there are other photos, this is what I turned up after a little bit of online trolling.

And as is often the case, I found it on Wikipedia and promptly stole it (yes, with proper attribution, I’m an honest thief).

Attribution

Speaking of attribution, we have several folks to whom we gratefully acknowledge their help with photos.

Will Paris

To begin, Will Paris of Balsa USA who shared several photos of highly detailed competitive Morane-Saulnier A.1 models. The one above, of the A.1 tracking the runway being an example. Ditto this one showing the forward fuselage. Note the oil streak details. Gorgeous, agreed? I share these for the inspiration.

Whit Philbrick

Workshop and flying field photos by Whit Philbrick, examples being equipment installation.

John Philbrick

And we especially have Whit’s father, John W. Philbrick (the fellow with the maroon MGB) whose flying photographs are unsurpassed in their quality and superb composition. This high speed pass being a great example of one of John’s lovely photos we’re using (Whit’s model being readily IDed due to the #11 on the fuselage).

Allen Whitaker

We gratefully acknowledge Allen Whitaker, who graciously allowed us to share his construction photos from within his RCSB build thread. These we use for the purpose of helping the novice builder.

Our shared idea being expressly to show how model building is ‘not’ some black art reserved for the cognoscenti blessed with special skills and talents. Instead, it’s something fun and completely open and approachable to all because the techniques of model building are easy to learn. This one of several examples to come.

Denny Friesel (RIP, 2022)

Then there’s Denny Friesel, who photos of Allen’s model at the flying field we used. Both this one showing the very beginning of a take off roll, plus a nice one of Allen’s model in the pit area. He kindly allowed us to use them, which we also gratefully acknowledge.

Patrick Van Surell

To access 1,964 different original French plans, just click this link and near the bottom of the page you’ll see these three links;

• Caudron (349 plans)
• Levasseur (200 plans)
• Morane Saulnier (1,411 plans)

And if these links go dead in future, then instead surf to;

• https://www.memoiredeshommes.sga.defense.gouv.fr/

And then surf these menus;

• Accueil (Welcome)
• Arts et sciences militaires (Military Arts and Sciences)
• Plans
• Plans de constructeurs aéronautiques sur des appareils civils et militaires (XXe siècle) – (Aircraft manufacturers’ plans for civil and military aircraft (20th century))

. . . I suspect Patrick sharing these may be of great value to some!

So circling back to Wikipedia and the Fokker V.25, despite the proliferation of still photography, it seems we’re downright lucky to have much information at all. In fact, if you consult Wikipedia, the V.25 entry is actually about the V.17 which is a mid-wing aircraft and the information about the V.25 (he low-wing version), is essentially just a V.17 footnote in what is a very, very sparse listing.

Point being, without Wikipedia, I found information to be rather slim pickings. So Wikipedia is an important resource. Yes, there are other resources, but while none are as consistently reliable as Wikipedia, they’re there if you look around.

Curious about Wikipedia? Seems there are three types of users. I came across this brief article and am sharing it because I found it fascinating.

• Going down a Wikipedia rabbit hole? Science says you’re one of these three types

Speaking of Wikipedia, this is their entry for the Morane-Saulnier A.1.

And back to the various cantilever wing Fokker aircraft; a one-off resource is a Russian site with information about the derivation of these fantastic aircraft. Basically, the detailed history of what happened in going to V.25 from the V.17.

And as they tell it, it’s a fascinating story in its own right. In fact, this is where I learned Reinhold Platz was the actual builder/designer. Yes, the same same Platz largely credited with designing the innovative Fokker D.VII fighter!

That he, a talented German, worked for Anthony Fokker, a Dutchman seems like a small detail. But remember, this is 1918, which means he’s designing aircraft intended for use in war and war accelerated demand!

Anyway, this link’s to a nifty Russian website (in English language) discussing the V.25.

• Flying Machines

Anyway, after the V.25 I found nothing about a V.26 (but it’s safe to presume it existed because the next one I found information about in the series is an aircraft listed as a V.27). And as it turns out the V.27 is yet another cantilever wing aircraft.

However, this one, and totally unlike the mid-wing V.17, and low wing V.25 is yet again different. The V.27 is in a parasol configuration.

A parasol? Yes, parasol, e.g. a sun stopper. Parasol is the French word for the lightweight umbrella ladies used when strolling to protect them from the sun (as opposed to rain). Same basic function, totally different duty. So from the derivation it’s reasonable to infer a parasol is a high wing configuration. And as this photo of the Fokker V.27 makes evident, both it and the Morane-Saulnier A.1 are parasols.

So the Fokker V.27 being a parasol configuration finally brings us back around to the subject of this guide; the Morane-Saulnier A.1. And as is evident, while we may detour through discovery of various online resource such that it may take a while to get there, there’s actually a method to my madness and we’re back on track.

Reason for all this? Anyone reading is interested in cantilever parasol aircraft of this vintage. Figuring someone reading this may choose to build a model of the Fokker V.27 aircraft. If so, a prominent feature is the ginormous spinner, which you’ll have to deal with, but which also assures you of being the only one at the field with one of these. Oh, and take note of the small fairings immediately aft (mounted on the fuselage). Point being, if you do, kindly remember to share photos with us!

Meanwhile, reflecting on Platz, I’m thinking his genius may have predated computational studies and wind tunnels, but he had an elegant and intuitive grasp of aerodynamics, agreed? Anyway, and also evident in the above is Platz and Fokker were onto ‘something’.

Aerodynamics and visibility

The ‘something’ is better visibility for the pilot because compared to looking down whilst piloting a V.25 (and being unable to see the ground), with the parasol wing being mounted above the pilot means the wing’s no longer obstructing the downward view. Important for ground attack and observation roles.

Speaking of seeing the ground whilst flying, I still remember how, after I sold Li’l Bit (our 1956 Cessna 172) and bought Sweet-E (our 1954 Beechcraft E-35 Bonanza), I had a feeling of loss. Simply put, I missed looking straight down to watch the world go by!

So eyeball the strut bracing arrangement of the V.27 once again. Could Clyde Cessna have been taking notes 35 years later when dreaming up my early vintage 172?

Thus, Fokker like the Morane-Saulnier aircraft were very much at the forefront of advancing the state of the art. After all, look again at the low-wing V.25, ignore the boxy fuselage and focus instead on its tapered wing panels.

Take note how it’s equipped with ailerons versus wing warping, which the Wright’s jealously protected with patent. Point being, if you can ignore the tip tanks, nose wheel, and V-tail (and squint really hard), do you realize how very much the V.25 wing configuration resembles my decades newer Beechcraft Bonanza?

Makes me wonder if Walter Beech was also studying Mr. Platz, who incidentally, only passed away in 1966. This, after seeing aircraft development through WWII and civilian development such that the Bonanza design was already almost 20 years old!

And can you imagine his thoughts on the space program and the race to the moon? What would he make of SpaceX and Elon Musk? Anyway, I digress!

So back to Wikipedia on last time; while they’re not a charity by any definition, Wikipedia are nevertheless on my yearly ‘give’ list. This, because I use their resource with surprising regularity and while it may be free for all to use, it’s not free to operate.

So in support of their efforts, I donate a small sum occasionally. If you find yourself using Wikipedia, consider joining me with a small gift as well. And toward that aim, this link goes to their donate page. Like if you’re feeling generous, even $5 helps.

Speaking of online resources, next up is a forum I’d like to bring to your attention, RC Scale Builder, or RCSB

RC Scale Builder – a forum

So circling back to the Fokker V.25 yet again, Whit’s got a build-thread on RCSB about his model. And if RCSB is a new one on you, it’s the acronym for RC Scale Builder, which is an online forum created by freelance software engineer, Mike Chilson. This makes him a hired gun (sometimes for really famous companies).

So Mike, like pretty much anyone doing work for Elon Musk, is another of those driven detail-oriented can-do kind of guys. One, who in his spare time (what little he has), is into RC model airplanes just like us.

Specifically, reduced scale replicas of full-scale or 1:1 aircraft . . . just like the ones I’ve been banging on about. So what recommends the RCSB forum is it’s totally unlike the major forums (where food fights occur with some regularity). It’s more collegial. Much more so.

The best things in life are free

It’s said the best things in life are free. There’s even a song about it. Me? Maybe because I’m old enough, I realize there’s no such thing as a free lunch (TANSTAAFL). So I give to Wikipedia.

Know what else isn’t free? Forums. Do you know why you can use them for ‘free’? It’s because you are the product. Yes, your words and thoughts are bundled and sold.

They’re sold to advertisers and data brokers, and they’re sold for training AI systems. Did you even realize this is the price of using free websites? In effect, you’re an employee of the forum – and – haven’t realized it because you’ve not being remunerated for it. Heads up!

Anyway, RCSB is ‘free’, also – but – only up to a point. This is because taking a page from drug dealers (who gives you a little taste and once you’re hooked, reel you in), Mike’s does the same thing (and in pretty much the same way). There’s a reason.

It’s to do with a) hosting RCSB costing real money, and b) scale types being a tiny minority of the modeling population. What’s important about this last detail is with a significantly smaller user base, there’s less appeal to advertisers. Point being, what works for larger outfits doesn’t work quite as well for RCSB.

So Mike took the bull by the horns and solved this issue by adopting a hybrid business model with some advertising but also a subscription. This sees folks (that would be you and me) pony up what amounts to lunch money after five posts. Worth it? I think so else I’m not running my mouth about it!

Point being, after 5-posts (presuming you like the place enough to bother posting), then you’ll need to reach into your wallet like everybody else to support it because everybody has to eat, capisci? So how much are we talking about for a yearly RCSB-subscription?

Honestly? Just enough to a) keep out the riff-raff, and b) keep the spammers from spoiling a really nice thing. And if this sounds like me making another recommendation alongside donating to Wikipedia, it’s because I am. Go join RCSB. Do it now . . . here’s the link:

• RCScaleBuilder.com

Best part? You’re not a product because Mike doesn’t sell your data. So why all the love for RCSB? Simple, because he also gave his permission for us to swipe photos off his website for this article! See what I mean about nothing in life being free?

So one last forum I want to bring to your attention. This one for small scale plastic models. Non-flying ones, at that!

WW1AircraftModels

So in trolling for V.25 and Morane-Saulnier A.1 info I came across an interesting post in a forum dedicated to plastic models. And it dawned on me these guys are just as into model aircraft as we are (folks flying the giant scale RC versions).

And they’re a good resource, hence my purpose in sharing the contact details. So the V.25 specific thread I came across has very nice photos of the model and interestingly, the color scheme depicted is theoretical, e.g. as if it had entered production. Here are a few other resources.

Morane-Saulnier resources

• Wikipedia Morane-Saulnier A.1
• Old Reinbeck’s Morane-Saulnier A-1
• Fantasy of Flight’s Morane-Saulnier A-1

Have noticed I’ve shared several links? I do that a lot and when you click one, it opens in its own browser tab. It’s a convenience for not losing your place within ‘this’ article!

The middle – building

So the middle of this article is dedicated to build photos contributed by Allen Whitaker. They’re some of many which follow along as he details putting one of these lovely Balsa USA models into the air.

The purpose of sharing is to demonstrate how easy it actually is to build your own model instead of limiting yourself to imported ARF models (I’ve seen photos of ten guys at the flying field all with the exact same model). Whatever.

Stabs

So the first step in construction involves taping the plans down on a workbench (make sure it’s flat). And by way of a tip, an inexpensive hollow core door purchased at a home improvement store works great. Set it on sawhorses and you’re ready to go!

ProTip: doors, which are cosmetically damaged such that building isn’t affected, but are discounted, are even better!

Next, cover the plans with wax paper (so the parts aren’t glued permanently) and get started with cutting bits of stock, and pinning down same, then gluing them together! Beginning with the tail feathers is time-honored advice in both modeling and full scale.

So bit by bit, using a Zona saw, a fine quality toothed saw, you begin cutting bits of strip stock to shape matching the plans. Then you glue the ends together and pin them down to dry. before you know it, a horizontal stab lays before you. Then the individual elevators. Next comes thee vertical fin and the moveable part of it, the rudder itself.

Note; gussets (little triangular bits) added where span and cord-wise oriented pieces meet. These add a heck of a lot of strength without discernible weight.

With the stabs completed, you have a choice, begin working on the fuselage or go for the wings? Allen went for wings next, so let’s stay in the flow of his build.

Wing panels

First thing he did was select the correct cross section for the wing spars and began pinning them down. The spars resist most of the bending moment of the structure. Depending on the model, spars may be balsa or spruce, a slightly heavier but immensely stronger species of wood used in aircraft building (both model and full scale).

After the bottom spars, the next move is to place ribs. Be careful to set them perpendicular to the workbench before gluing. Some use small squares to help.

Note how in the photo, Allen has fitted the outer part of the wing tube (red), typically made of cardboard but occasionally made of fiberglass. Also, a smaller diameter alloy tube for aft wing alignment, plus another (brown, medium size) for routing servo extension leads.

So with this photo we get a better sense of scale. Note the rib in the foreground, the one laying across the spars i preparation for being glued in place.

Look carefully and take special note how he has pinned shims beneath the aft spar. This detail undoubtedly covered in the excellent BUSA instruction manual (BUSA = Balsa USA).

Refer back the previous photo to see this detail better. The purpose of these shims is to account for added sheeting of balsa of the same thickness as the shim stock.

So now I’ve skipped a bunch of photos. My aim isn’t to replace the build thread on RCSB, it’s to give you a taste because I’m in if not in cahoots with Mike on this one, in close alignment.

Look, any idiot can assemble a ARF form prefabbed components. And plenty of imports offer you this but in the USA, our companies are more into satisfying the urges of the ruggedly individualistic, folks for whom owning another me-to model is less than satisfying.

These are the class of folks who turn to building from plans, kits, and sketching out their own designs. This guide is for giving you a taste of how easy it actually is to build. This isn’t rocket science!

Anyway, in this next photo we have the left and right wing panels assembled as a whole. They’re held together, joined, with an alloy tube slipped within the red outer tubes. Note where the tube for the leads end – where aileron servos will be fitted, later.

Note; this large diameter wing joiner, a piece of aluminum tube is what carries the weight of the entire model’s structure. A smaller tube, aft nearer the trailing edge helps, but principally serves in alignment to keep the two panels properly oriented.

Note in the above photo the bits of wood at the wing tips. Specifically where the wood shaping the wing tip remains proud of the perimeter pieces. This still needs to be sanded to shape.

For this, a sanding block (a piece of wood, alloy, or plastic fitted with sandpaper, perhaps 120-grit), will do the job quickly and easily. A few quick swipes, perhaps followed up with a different sanding block fitted with 180-grit paper to smooth further will put paid to the offending edge of wood.

Fuselage

The next step is the fuselage. It begins similarly to the stabs and the wing panels but here, the long strips aren’t called spars but longerons, instead. Longerons carry the principal loads of the fuselage and depending on the model may be made of balsa, or a harder wood called spruce, instead.

In this next photo we see the different color wood, which is harder and is the forward part of the fuselage of the model where the firewall will attach. Note how the longerons are pinned to the plans just like spars for wings are pinned to the plans.

Also, eyeball the small square, which the good builder always has at hand. The purpose of the square is for aligning parts before gluing.

Now we see how a fuselage side comes together as uprights and diagonal pieces are fitted to the longerons. And when completed, another side is built directly on top of this one merely separated by wax paper once again!

Note above how two hardware store clamps are used together to extend the reach beyond what either can do. Also how wood clothes pins have been reversed to make wider opening jaws. Ingenuity like this is what distinguishes an experienced builder from the rookie. yet once exposed to the idea, novice builders quickly adopt these techniques into their own workflow.

Join me in snooping a bit further. Two types of CA, thick gap filling in green, pink for thin. And another tool for building, the plastic triangle is joined by the Zona saw (with the wood handle), plus a flexible plastic ruler, rubber bands, pins, etc. Note the sanding blocks at the far end (yellow, red, blue demoting different grits).

Finally, note the tool for transferring angles to cut bits of wood directly in front of where the builder stands whilst working. And guess what, working on a model doesn’t have to be a lonely pastime as the shop dog is a time honored companion.

In this photo, note the cutout in the plywood gussets for the crosspieces which will be used to join the two identical fuselage sides.

Now we skip forward once again, the sides have been joined with cross pieces and half-moon formers are added to flesh out the box of the fuselage. Note the notches in these for square longerons yet to be added.

Let’s snoop a bit further; what other tools and adhesives do you see? The yellow tip on a bottle of epoxy, a 2-part adhesive, can just be seen to the left. A pair of scissors, and X-Acto handle sporting a #11 blade, even a T-handle alloy sanding bar at the far right.

This next step sees the fuselage in better perspective. The firewall has been carefully fitted within the uprights and cross pieces at the forward fuselage.

Note how well the builder has fit these piece such that no gaps show. The lighter colored wood is balsa, the slightly brown is something harder, likely spruce.

And the plywood making up the firewall? This is composed of layers of birch. Plywood for aircraft building is very much like the plywood used in home building. But birch-ply is finer grade of wood than is used for roofing and floors, it’s almost exactly like what’s used for fine quality cabinets.

Plywood also implies a whole made up of layers with the grain of each oriented cross ways to adjoining layers, thus giving it strength.

Engine fitting

So now we see why all this strength is called for, it’s time for fitting an engine. In this instance, a single-cylinder thumper by Zenoah.

Comprised of a two-piece crankshaft with ball bearing supported forged crank and rod, this 62cc powerhouse sports magneto ignition and is super reliable. I have one just like it.

Note the automatic center punch, an Allen key, and the template the builder used for transferring marks for drilling for the engine bolts for securing it to the firewall.

What can’t be seen is the spring starter on the backside. This to aid in hand propping the engine. 1/2-3/4 wind backward and let ‘er rip!

Once again clamps come into use. These bar-type clamps use a pistol grip to tighten them and I have several in my workshop as well.

And take note of the neat job of using triangle stock to add lightweight but strong reinforcement to the plywood box supporting the engine to the firewall. What I especially notice is how well the joints are cut such that you can’t see the joints.

This, tight joints, is the mark of a true craftsman.

Landing gear

So the next step in building the Morane-Saulnier involves soldering up the landing gear and cabane struts for supporting the wing center section at the fuselage. This involves pre-bent segments of music wire, which after aligning together and wrapping the joints with copper wire receive solder. This, to make them into a one piece assembly because once it cools, the solder acts like glue for metal with the copper wire wrapping the segments together acting like rebar in concrete.

Tools needed include a 100-200W soldering iron, flux paste, 60/40 solder, and a little bit of effort. YouTube videos aplenty show you how – but – nothing beats giving it a go. This is one of MANY examples to be found regarding soldering music wire.

Best part? If you screw up, just apply heat and disassemble. Didn’t get all the solder off? Heat again and wipe it off. Then have another go at it. I own a Weller W201 solder iron, which I have had for decades.

Once aligned, and after applying flux, putting the heat to the joint and adding solder to make these joints permanent works as if they had been glued together. Both cabane struts for mounting the wing and landing gear struts for supporting the model on the ground are made up this way.

Seems tricky until you do it once and then after that it’s duck soup!

So now it’s time to dry fit the model together. Yes, I’ve skipped a bunch of photos but by now you’re getting the gist of this. Just take your time and follow the instruction manual. And if you join RCSB, you’ll find the source of all these photos and se the steps I’ve skipped.

So what’s left? Not really all that much, covering and then installing the avionics. First up, the covering.

Covering – iron on fabric, or silk-and-dope

While some will resort to a film covering like MonoKote or UltraCoat, the shiny look is really not quite right. A better solution is to either use iron-on fabric, or a do a genuine silk-and-dope job.

If the latter results in a wrinkled brow and a huh? Then review this brief article where I touch on how to do this kind of high end work.

• Silk and dope – demystifying modeling’s classic finish!

Anyway, most folks will resort to iron on fabric, either pre-painted or raw, which needs painting. Which one? Doesn’t matter, pick ’em!

Allen resorted to prepainted silver Solartex but he could also have used SIG Koveral fabric, dress lining from Jo-Anne’s Fabrics, or the Stits process. The last three being similar and what I term as raw.

Raw as in unfinished fabric. This is where first you brush on heat activated adhesive, and then tack the cloth down around the perimeter before heating the fabric to shrink it down. Then paint.

First up were the stabs.

The wings weer done separately and set aside.

Last came the fuselage

Next came a final test fit the engine and cowl. Allen’s basically at the stage of an ARF, and nearly ready for final assembly and avionics!

Last part of building is matching the silver paint on the fuselage!

And the pay off? Once assembled and test flown, it’s a lazy day on any given summer weekend. One where yours is likely the only Morane-Saulnier at the event. This means that in a sea of ARFs, everybody has been stopping by to check out your work.

You’ll be imbued with a sense of pride at a job well done. Honestly? The feeling is one, which no ARF on the planet can give you. It’s an unmatched sense of self-sufficiency for building it yourself. Priceless.

An ARF version

So you’re you’re hot for Morane-Saulnier A.1 and a) you don’t have the time to build one, and b) you’ve looked around and there aren’t any for sale nearby. Well, you’re in luck because as it turns out there’s a solution offered by an East Asian import model builder.

The famous Vietnamese company Seagull Models has something, which may interest you. Yes, we’re talking about an ARF. One which by pure coincidence is offered at the exact same 1/3-scale, 103in wingspan, as the BUSA model.

Moreover, they project it to weigh between 25-30 pounds, and it’s since it’s basically the same-same model (without as much work), you can figure to use the same engine and avionics as the one you put together from BUSA.

Some will say it’s wrong to mention it, and obviously, I disagree because I’m not here to judge. Each and every one of us is a big boy. By this meaning we each make our own calculations when it comes to balancing between work and family life, and between time and money.

Saying, a) its existence isn’t a state secret, b) not my call.

One thing is certain, the Seagull Models 1/3-scale model of the Morane-Saulnier A.1 is a handsome and viable alternative to building your own. Or put another way . . . to each their own!

The end – avionics

So moving on, and we’re circling back around to Whit. You’ll recall he didn’t build his BUSA Morane-Saulnier A.1, he got it from an estate sale. He too short circuited the entire build process. And nothing wrong with that, either because I’ve bought lots of airplanes others have built, bet you have also. Anyway, while the builder is unknown, Whit says he did a good job.

He chosen a Zenoah GT-80 twin to power his model. If you’re unfamiliar with the engine, it’s a smooth running powerhouse (much smoother than the very well regarded Zenoah G-62, which is another great power source).

This 80cc twin may be just about perfect for the model power-wise (despite the increased displacement, output is similar to the 62cc single due to the added ring drag of the extra cylinder). However, there’s a huge advantage, which is it’s a much smoother source of power. This, due to being a boxer configuration twin (boxer meaning opposed cylinders). So the plugs fire at the same time and in perfect opposition thus counteracting the vibrations found in singles. Airframes and avionics last longer than with singles.

Anyway, I am a fan of the GT-80 engine despite it being a) a bit on the porky side, and b) rather less powerful than newer designs from the likes of DLE and Desert Aircraft. This, for one principal reason, because of it’s self-contained magneto-ignition. No module battery to maintain is nice. That, and available spring starter mounted on the aft shaft which means you hand start it more easily. Win-win!

So this is Whit’s model of the Morane-Saulnier assembled within his shop. And yes, it’s big enough to fill up a room!

Avionics

Up next are the tools needed to do the servo installation job. This included a small Phillips to remove the old servo mounting screws. When it came to installation, he needed a couple of Allen drivers.

A 2mm for installing the servos to the rails with the supplied Allen head #2 screws (and the servo arm to the splined shaft). He also used a 2.5mm Allen for snugging the radial screw (the one for taking up backlash between arm and spline shaft). That’s it!

Servo installation

And by the way, there’s a right and wrong way to install servo mounting hardware. And based on how often I see it done wrong, I put together a guide showing the right way. It’s a brief read.

• Servo installation done right!

So unlike servo installation, one of the nice things about a scale model is there’s no right or wrong way to finish it off. You can keep it simple, or you can go whole hog.

This lovely example has a highly detailed dummy engine and scale prop. If anything shows what’s possible, this one does so.

Moving along . . . so after removing the old analog servos, screwing down the new digital servos in their place took less time than it takes to drink down a Coke.

Next, after installing new servos in the fuselage (for the tail feathers and throttle), it was time to go back and fly. Assembly is something of a two-man job.

This, because the mass of one wing panel will definitely tip the aircraft over on its landing gear! The alternative is to rig up something to help hold it but easier by far to ask a pal to lend a hand.

Note the protective covers on the prop blades, pretty nice!

And in flight, as this photo by Whit’s Dad, John shows, what you end up with an awesome looking aircraft.

The end . . . but a beginning

A few bits of housekeeping before wrapping this up. Selecting 360oz-in seems like overkill unless you realize 360oz-in is both true and a lie, at the same time. Reason is it depends on the input voltage.

Packs and switches

Study this chart, it’s divided by 5 voltages for a reason. And every ProModeler servo discloses these details so you may bring your judgement to bear.

• 1st column corresponds to a 4-cell NiCd or NiMH pack. Old school chemistry, so 1.2V/cell X 4 cells = 4.8V, or a nominally 5V.
• 2nd column corresponds to a 5-cell pack; so 1.2V/cell x 5 = 6V
• 3rd column is a 2S pack with 3.3V cells, so 3.3V/cell X 2 = 6.6V
• 4th column is again a 2S pack, but LiIon at 3.7V/cell X 2 = 7.4V
• 5th column is synthetic sources, BECs relying on FETs (fast switches to make the juice). Usually these max out at 8.4V. Added to which, a 2S LiPo coming off charge will see 8.4V, also.

What’s important about columns 1-4 is these are nominal voltages. What this means is when you see this value with the voltmeter, then stop flying and put the pack on charge.

For example, the A123 pack (3rd column) will be around 7.15V coming off charge and drift down as you use it until you get the 6.6V when it’s time to recharge.

So the very first thing to decide when equipping your model with servos is . . . what chemistry do you plan to use? Unless you’re flying 3D and want everything a servo can give, then because they’re easier to live with, we guide our scale customers to A123 type battery packs. These are the middle column voltage-wise.

Learn more with this brief article:

• On the batteries John prefers using

While we offer battery packs, so do others. What recommends our is we have them built with more than a single lead. So we offer them with dual DuPont connectors (in the hobby trade called JR, Hitec, or Futaba, but all based on the same 0.1in pitch design) as well as dual XT30 and dual EC3 packs.

This example is dual DuPont.

Here’s what’s in it for you having 2 DuPont leads (JR-type) leads.

First, this enables use of DUAL switches for safety. Useful because the odds of both failing on the same flight are astronomical.

And second thing in it for you is now the model can draw 2X as much current from the battery pack as with a single lead. This is because each DuPont connector is rated at 3.5A, continuous.

So with two connectors, this means you can draw 7A without heat build up. And the switches we offer? Rated a lot higher than that!

For example, this illuminated rocker switch is available with DuPont connectors (universal, what’s called a JR-type connector). This, with 20AWG silicone jacketed wire.

We also offer the same switch with 16AWG leads. But instead of JR-type connectors, it has XT30 connectors. Ditto a version with the EC3 connectors.

We also offer you a toggle switch. This is equipped with a condom (not really, but same idea). And it’s considered waterproof as a consequence. So these have the same connectors, XT30 as well as EC3 so depending on your avionics choices, you’re in tall cotton.

These are rated at 15A and are a good solution for some of us.

Note: nominal voltage for our A123 is 6.6V and when you see this with the voltmeter, stop flying and recharge the pack. Anyway, for this model with DS360DLHV all around a matching DS90DLHV for the throttle, the B2S4000 battery setup is good for 8-10 flights, easy!

Servo Selection

We’ll offer servos using the metric of good, better, and best. So let’s get down to it, the main event . . . servo guidance for the Morane-Saulnier model.

Good – DS180 to DS270

Some guys will opt for our DS180DLHV servos, or maybe DS270DLHV. I think either would be a fine selection with a lightweight build (think 17-19lbs. Figure a lightweight engine, perhaps an OS or Saito 120 four stroke. Modest turn of speed. Sport use, nothing crazy.

At this weight the model is an absolute kite that lands at a walking speed. Save money and use a DS90DLHV for the throttle (and choke if you like), plus PDRS101 servo arms everywhere except throttle, where you’ll select a PDRS105, instead.

• 5) DS180DLHV or DS270DLHV
• 1) DS90DLHV
• 5) PDRS101 heavy duty fiber-filled servo arms
• 1) PDRS105 heavy duty fiber-filled servo arms
• 2) EX20AWG36 – 36in extension, ailerons
• 2) EX20AWG6 – receiver –> mate up aileron to receiver
• 2) Y-harness – for aileron extensions
• 2) Capacitors – for aileron extensions

So you see the last two items and wonder, what is Beech up to now? Simple, whenever extensions go beyond 30in you should add capacitance.

Adding capacitance

This is true for all servos . . . any and every brand. Learn more here:

• Why and when to add capacitance

Meanwhile, I just threw some servo models numbers at you and operating under the assumption you’re unfamiliar with our parts nomenclature, it’s surprisingly straightforward and easy to suss out;

So a DS180DLHV breaks down as a 180oz-in digital servo with an iron core 3-pole motor, that accepts up to 8.4V.

And if 180oz-in sounds familiar, it’s because many, many, many servos output in a range of 160-180oz-in. And, I also said 270oz-in.

Competing servos

Examples includes several very well knows servos from other high end makers like Hitec and Spektrum (plus others). Perhaps the most famous being the Hitec HS-645MG, which begat the digital version at 6V, the equally famous HS-5645MG, and their newer iteration of that servo, the 8.4V D645MW (133, 168, and 180oz-in respectively).

And pitching 160oz-in for the Spektrum lineup is their well regarded A6380. And note; while we can measure 160, 168, and 180oz-in within the lab, when mounted within a model it’s ‘extremely’ unlikely you, or anyone else on this planet can discern a performance difference between these.

Point being, these servos are collectively within the same ballpark. Also, while Hitec still sell it, I really only mention the old analog HS-645MG as a point of familiar reference as pretty much any digital servo bitch slaps that unit in terms of holding torque, which is what really counts.

And note, bit stronger, in the 270oz-in range, the Spektrum A6320 is a near peer of both ProModeler DS270DLHV and DS255BLHV. All three are standard class metal gear servos with ours bookending theirs in terms of speed and killing it in terms of build quality and price (our opinion of course, but if you review the matchUP article the close up photos will help you form your own concurring opinion).

This brings up how these fine quality competitors compare to ProModeler servos. While diving in is beyond the scope of this Mister Mulligan article, to learn more, just review these matchUP articles.

• Hitec D645MW vs DS180DLHV
• Spektrum A6320 vs DS270DLHV
• Spektrum A6320 vs DS255BLHV

Better – DS360 and DS415

Heavier, call it 20-24lbs? Then this is where I’ll guide you to our DS360DLHV, instead. Perhaps DS415BLHV if you appreciate the finer things in life like brushless motors.

Yes, still using DS90DLHV for throttle. Now I’ll advise you use to use alloy PDRS25-25T servo arms for the flight controls, and still using the heavy duty PDRS105 polymer servo arm for throttle.

• 5) DS360DLHV or DS415BLHV
• 1) DS90DLHV
• 5) PDRS25-25T heavy duty fiber-filled servo arms
• 1) PDRS105 heavy duty fiber-filled servo arms
• 2) EX20AWG36 – 36in extension, ailerons
• 2) EX20AWG6 – receiver –> mate up ailerons to receiver
• 2) Y-harness – for aileron extensions
• 2) Capacitors – for aileron extensions

So now maybe you noticed the BL within the parts number and realized one of these alternatives sports a brushless motor. These are better.

Not to insult you, but if you don’t know jack about servo motors, then this motor article will bring you up to speed lickity split and it frees you of friends and fellow club member who may, or may not, actually know what they’re talking about but have strong opinions.

They say knowledge is power so read this article and you will know which side of your bread is buttered when it comes to selecting servos. Or at least you’ll ‘know’ which type of servo motor best suits you, and why.

• About RC servo motors

Best – DS505

So let’s say you’re power mad so you opt for a lot of ponies (think Moki’s 150 radial). Or maybe one of those UMS 9-cylinder radial engines has caught your fancy, or even the enduring appeal of the Saito quality does it for you.

No, it’s not a Gnome Rotary, but it looks and sounds great. Add to it, due to the mass of the engine, now the model goes well north of 30lbs, say 28-35lbs, or even more.

So the old saying with power comes responsibility comes to mind. Saying a fair bit of weight and high performance means you may be better off with an all-alloy case servo like our brushless motor equipped DS505BLHV.

Yes, I’m saying 500oz-in . . . have I gone crazy? Maybe, let’s see. This is the equipment list in terms of best servos and arms.

• 5) DS505DLHV
• 1) DS90DLHV
• 5) PDRS25-25T heavy duty fiber-filled servo arms
• 1) PDRS105 heavy duty fiber-filled servo arms
• 2) EX20AWG36 – 48in extension, ailerons
• 4) EX20AWG6 – receiver –> mate up aileron to receiver
• 2) Y-harness – for aileron extensions
• 2) Capacitors – for aileron extensions

So let me explain my thinking before you decide I’m out in left field.

Rationale

Reason for guiding you to an all-alloy servo is our good and better servos feature hybrid cases. Examples are our DL-series and BLS0 which are, a) quite a lovely set of well made servos, and b) something of a bargain, and at the same time, c) suffer from a malady of all plastic-case servos upon being heavily loaded. Eventually they suffer from the case top stretching at the output shaft bearing.

Key phrase in the above is a lot of load. Fly a Morane-Saulnier at 19-20lbs and it may take 20 years to develop. Fly a 1/5 Mustang with DA-85, or this model at 25-28lbs and it may happens in a one to three seasons.

What?!? I’m admitting to a design defect? Nope. Admitting to nothing of the sort. More like explaining what the limits are. Let’s delve a bit deeper so you may better understand what’s going on.

Look, I’m keenly aware I am giving advice – but – it’s on you to do what’s best for you. So because I know more about servos than my customers, I can give you the straight skinny the other servos guys don’t.

What will you decide to do? Dunno, that’s on you. My job is give you enough info to make the best decision for you, not tell you what to do (plenty of folks on Facebook and the forums perfectly willing to tell you what to do, we’re not one of them).

So your decision . . . yours alone! Here’s what you need to know, about which the other guys stay shtum maybe in order to sell servos.

Limits

Basically, servos with plastic cases, when heavily loaded repeatedly, eventually exhibit stretch deformation. And this eventually also leads to slight movement at the output shaft (perceived as slop).

And not just ProModeler, but any and every servo model and brand, when made with a plastic case top, will do it over time. Believe me, plenty will offer up polymer case servos – far – beyond the point at which ProModeler will, in good conscience, stop and switch to alloy.

Here’s is what nobody tells you, which you need to know . . .

• the larger the model,
• the heavier it is,
• the harder it’s flown,
• the longer the servo arms, and
• the larger the control surfaces

. . . then the quicker it happens. Not a matter of opinion, it’s physics!

Remember, plastic comes from the Greek plastikos which means flow. So it stands to reason when it flows, it changes shape. And this changing in shape in engineering is termed stretch deformation.

The servos in this next photo range from 160oz-in to 624oz-in. All have plastic tops. Specifically, an engineering polymer composed of nylon and fiber fill (can’t speak to theirs but ours is glass-filled 6,6 and this is the kind of stuff Glock uses for handgun frames). Theirs will be similar.

It’s used in servos for pretty much the exact same reason Glock and Smith & Wesson use it, because it’s light, tough and impact resistant.

Solving stretch deformation with alloy

So is there a solution to stretch deformation? Well, funny you should ask, because yes, there is. And it’s found in an all-alloy case servo. More money, of course. This is why the DS505BLHV is the servo we’ve ranked ‘best’ for heavy Morane-Saulnier builds, like ones with 10lnb radial engines, capisci?

Anyway, hybrid servos top out in a DL-series with the DS360DLHV and with our sweet DS415BLHV in a BLS0 series. However, once our servos go much north of 400oz-in, we switch to all-alloy construction. As exemplified in a BLS1 like our DS505BLHV servo.

Why do others offer plastic case servos going +600oz-in? No offense but you need to ask them. Our line in the sand is our DS415BLHV servo outputting 415oz-in. More powerful than that and we only put our reputation on the line with alloy cases.

Remember, this is going to be your call, we’re a) not going to tell you what to do, and b) we operate on the assumption you’re reading this to learn, not for pablum that’ll make you feel good about yourself.

Bottom line? We’re engineers, not salesmen. And if you want someone to hold your hand, ask your wife or boyfriend, not us. We’re telling you what we feel you need to know, but the decision is yours!

Want to know more about the DS505BLHV servo? Best way to get to know that servo – in my opinion – is seeing what happens when they get destroyed and returned to us for R&R service (repair & rebuild).

This article does a nice job of it with the side benefit of showing how to put a servo back together if you ever take one apart!

• On rebuilding damaged DS505s

Back to stretch deformation

Anyway, back in the day with Futaba servos with plastic gears and no bearings in the tops, I built several large gas powered models to include a Nosen DGA-6 Mister Mulligan and P-51 Mustang so I feel entitled to share my 2¢ on how I’ve actually purchased a set of aftermarket case tops to add bearings to servos delivered without. Yes, once upon a time, upgrading your servos was a thing!

And the very purpose of this was to address case deformation at the output shaft. So I’m not bringing up something new engineering-wise to the world of modeling, we know how to solve this . . . to a point.

Thing is, they soon got sloppy once again. And this time I blamed the gears. And note; this from long before I got into the servo business.

Anyway, I still remember my surprise coming across them a few years back (I don’t throw anything away). There they were packed away and as I handled them, I noticed something (because I know more about servos these days).

Basically, now, with fresh eyes due to years of servo experience under my belt, I was shocked at realizing their sloppiness wasn’t so much the gears as I’d assumed but due to case stretch deformation ‘despite’ the added bearing. And yes, some gear wear but the proximate cause was the case stretching at the output shaft bearing seat.

Added to which, I could feel movement within the gear train. This attributable to deformation at the pocket where the gear shafts seat.

Two different issues. Let me explain.

Gearshaft pocket deformation

In one instance a weakness of the polymer case construction is stretch deformation where the bearing is fitted. The second instance is deformation at the gear shaft pockets.

Unlike near peer competitors (defined as similar torque and pricing), we add bushing reinforcement at the gear shafts within our plastic case servos. How? By doing what’s called an insert mold process.

This is where bronze bushings are placed in the mold before the injection of the molten nylon 6,6 material. That’s what the shiny bronze bits in this next photo are about.

These bushings serve as reinforcements for the gearshaft pockets. The idea is to preclude the stretching that results in gear play and accelerated wear. More cheaply made servos don’t give you this protection.

Note; in the above photo the gear shafts themselves are the same diameter, the near ones looking larger are an artifact of perspective.

Point being, what you get with a ProModeler hybrid case servo (as a result of our reinforcing the case with bushings) is nearly the durability of an alloy case servo for less money. Just as durable at the gear shaft pockets of an alloy-servo – but – because we don’t have the room to also add a bushing for the output shaft bearing pocket in polymer, an alloy case is still better.

The bushings solves the pocket wear issue (stretch deformation at the gear shafts) for all users, while the alloy case solves the stretch deformation issue for heavy load application, also. Like I said, this is engineering tasked with solving for two different issues.

Operative in the above being ‘nearly‘ and ‘heavy load applications‘.

Combining use-cases

Anyway, I think for most folks the DS360 or DS415 will be plenty enough servo torque-wise for the Morane-Saulnier model. But I would be strategic on where I might use them depending no how heavy the model turns out. Especially if you like flying it fast at times.

This, because just as we learned as little kids when we stuck out hand out the wind to fly it up and down whilst changing angle of attack, there’s a lot more force at 65mph than a 25mph. Same holds with our models, compounded by larger control surfaces.

Point being, on rudder, ailerons, and flaps these surfaces would likely be fine with DLS or BLS0 servos. They would likely experience a long service life. And I’d certainly do this if money were tight.

So mixing and matching becomes a use-case of selecting servos from the better-group ‘and’ the best-group. Or put another way, a savvy user combining the better use-case and the best use-case to customize the servo selection to suit your own particular needs.

I’d also sleep fine using hybrid case servos (hybrid being the term we use for servos where there’s an alloy finned center case and plastic is used for the upper and lower servo sections) as long as I were using 1″ long servo arms like PDRS25-25T. Longer than that with a heavy model and I’d reassess what I was thinking. Consider yourself warned.

Please refer back to my list of conditions where case wear is accelerated. Take note that long servo arms is on the list for bad juju when added to hybrid case servos.

Anyway, I’d be totally fine using hybrid case servos with one-inch long servos arms, like below, rather less so with anything longer.

Servo arms in greater detail

If, for example, I felt the need for a longer arm, perhaps PDRS40-25T, (basically 1-1/2in) or longer (we go out to 60mm, or 2-3/8in), then I would definitely switch to all-alloy servo construction. Especially on elevator when the model is fast because of a powerful engine. And in particular when it’s also a ‘heavy’ model (north of 20lbs).

Why? Simple, it’s because of the added leverage of the longer servo arm compounded by greater mass and higher airspeed. Let me explain. I’ll use a little bit of grade school math, nothing too arduous.

Remember, the servo has a torque rating but you can (your model can, actually) feed force back into the servo. How? Well, there you are flying along fat, dumb, and happy.

It enters your mind to perform a loop, maybe a big 200ft diameter loop. And maybe you didn’t cut power soon enough so on the backside, the speed builds up pretty good. Means as the model rounds out, the G-loads begin to build.

True even if you don’t touch elevator to further tighten up the loop. But especially true if you do tighten the loop, like if you miscalculate altitude and as the model nears the ground you pull up more.

Like I once saw the elevator stick of a transmitter literally bent by the application of force as a panicked modeler tried to save his model from the dreaded figure-9. You know, the one where the maneuver ends about 1 foot below grade. I kid you not.

Anyway, pulling so hard didn’t help and the model splattered like a watermelon falling off the bed of a pickup going 60mph. Engine ended up more than 100yds downrange torn to Hell and back because it bounced on the asphalt the whole way before coming to a stop. Dude cried.

And of course, we all ‘know’ to cut power on the backside of the loop to keep speed from building up but raise your hand if you’ve never ever done it, not once. So in the real world (humans, feet of clay, etc.) we sometimes get a bit distracted/careless whatever. So if we forget and don’t close the throttle enough, the airspeed builds.

Then here’s what happens; as the model transitions from straight down (3 o’clock position) to horizontal (6 o’clock) and into a climb, the G-forces get strong. Like a couple of G is normal but when carrying too much speed, the model may see 3 or even 4Gs, briefly.

So do the math, 20lb model, at 2Gs means it’s experiencing gravity at 40lbs of force at the bottom of a loop (20lbs x 2G = 40lbs). Now say you’re using a 40mm servo arm (this is about 1-1/2 inches, major point being it’s longer than the arm for which servos are rated, by definition, a 1 inch long arm).

So using a 1-1/2in arm means output is reduced by 1.5X but being longer, it also means the arm is ‘inputting’ a larger force. By how much? By the exact same ratio, 1.5X (1-1/2 times).

This effect on the servo is akin to adding a cheater bar to a wrench to help loosen a stubborn nut! Check out some numbers . . .

• With a 1-1/2in long servo arm, a servo outputting 360oz-in outputs at the outermost mounting position 350/1.5=240oz-in. Again, not opinion, physics.
• Conversely, inputting a force back to the servo using a 1.5in servo arm vs a 1in servo arm the force is multiplied, it’s increased by 50%, so 20lbs becomes 30lbs.
• And a 20lbs model at 4Gs at the bottom of a loop? That’s akin to 80lbs being fed back into the servo.
• And just FYI . . . 360oz-in is the same 22.5lbs.

Anyway, at the bottom of that loop, it means now the mass of the model, multiplied by gravity (and the faster it goes the more G-forces) are back feeding the forces of the air acting on the control surfaces backward ‘into’ the servo’s mechanical structure (the case).

Where? Focused at the output shaft. And since the bearing is what is supporting the output shaft, then this is why I keep talking to you about stretch deformation. Saying – bluntly – these forces ‘may’ be in excess of those for which the servo’s been rated.

Beginning to understand the issue of stretch deformation?

Faster and heavier

Next, imaging the model’s going a bit faster, now instead of seeing 3Gs, or 60lbs of force for a 20lb model, imagine it’s maybe seeing 4Gs or even 5Gs, call it 80-100lbs. I bring this up because engineers always go the edge case to understand what can happen.

You are responsible for making a decision regarding what servos to use. Whether you select some of ours, or another brand, if you’re reading this it’s because you’re curious and want to do the research resulting in the best decision for you and your circumstances.

Anyway, as I keep repeating, what resists the force feeding through whatever length servo arm you’ve selected? It’s the 25T splined output shaft. And what’s supporting this? The bearing. But what’s supporting the bearing? For some servos it’s seated in plastic and for others it’s aluminum!

And we know plastic deforms and may even crack with repeated loading. Just saying the foundation for your servo’s entire structure is the case. We, like many others offer cases made with plastic components (technically an engineering polymer).

Genius lies in solutions

So knowing this about stretch deformation, we didn’t just sit on our thumbs. Back in 2023 we redesigned the standard class upper polymer case. What for? To reinforce it!

Remember, everything we’re saying about our polymer case servo holds true for Savox, Futaba, Hitec . . . anybody and everybody’s servo made with a transmission section using plastic case, OK?

So to reinforce it meant a new mold. One adding more material. In fact, we spent a fair bit of coin editing the mold for the upper case of our standard class servos.

What did we accomplish? Eyeball the massive ring of material we added to reinforce the design surrounding the output shaft bearing in this next photo . . . this is before and after.

Note above how – now – there’s more material surrounding the 25T splined output shaft where the bearing seats. Our servos have a ‘lot’ more material than competing designs. And it’s there expressly to better anchor the bearing.

This next photo shows competing approaches in the 270oz-in class. So not just more plastic compared to the previous iteration, more than competitors use.

Added to which, beyond the bearing support ring being much beefier, note how we’ve also boxed in the output shaft bearing with 2 added bolts. Basically, six bolts total but four in close proximity and surrounding (or boxing in) the bearing make the case section stiffer than a case assembled with just four screws.

The extra bolts helps the gear mesh stay at design limits. But no matter what, it’s still plastic so there are limits to how well it’ll hold up, which is why we go to alloy cases north of about 400oz-in.

Again, your call regarding what to use servo-wise. However, it’s our opinion a 20-24lb model is approaching the limit for a polymer case. No, this is not hard and fast rule because as usual, it depends.

On what? On how much the model weighs, how fast it is, and on you, also. E.g. how hard you fly it? Like do you horse it around the pylons like what it is, a replica of an air racer, and the way I flew mine? Or are you a Sunday flier who flies around for fun with the engine large parts of the time at part throttle? This makes a significant difference in the stresses on the entire structure and the servos, take my meaning?

We’re all different and even a heavy model with a super powerful engine can be perfectly fine with hybrid case servos if you’re not out tearing up the sky all the time flying it like you stole it. So it’s a continuum and this is why I can’t (nor can anybody else) tell you with absolute certainty which servos are the very best for you.

Recapping, one servo per control surface, overkill is never a bad idea if you can afford it, and if the model is heavy and fast, opt for alloy at least on the elevator servos. Added benefit is you also get a brushless motor. The motor article I linked earlier will help you understand the differences.

Note; ProModeler servos have soft start. They all do. So you get the benefit of the gentle centering to protect airframes upon the application of avionics power even with our $30 entry level models. Ditto finned alloy centers.

Cooling fins

Fins shed heat better. Cost more also. Worth it, else we don’t do it. Note the o-rings on the bolt heads. You don’t care if they are or aren’t there? We don’t either. But if you do care, then you’ll be glad we put them there. All servos don’t have them. So remember the old saw, you get what you pay for. Problem is, consumer grade servos may charge you but not deliver.

Maybe ask, or better still, take a look for yourself.

All-alloy servos

So for our polymer case servo we reinforce where the gear shafts are fitted with bronze bushings. But it’s not practical to do this at the output shaft where the bearing is fitted. So we beefed up the polymer at the opening. Made it better. It’s a LOT stronger.

Does this make it as good as an alloy upper case? Nope. Does, however, make it a country mile better than competing designs.

So in anticipation of higher loads, you may have noticed our servos switch to aircraft aluminum for the case. Still light, but stronger than polymer. Basically, beyond our DS415BLHV servo, we go to all-alloy cases.

Note; we also reinforce gear shafts bore within our alloy cases.

So this conversation regarding stretch deformation is 100% to do with strength of materials. Plastic is great until it’s not and at 20 lbs and a fair bit of power, we’re at an edge-case. Approaching the limit. Where’s the exact limit? We don’t know, exactly because it’s not like the edge of a cliff. We know it’s there, but don’t know where exactly. Thus, cluing you in so you don’t pony up for servos and regret it.

Unfamiliar with your wallet, I don’t know if the thought of $100 a pop for DS505 elevator servos is out of the question, or no big deal. Just as we’re all different as pilots, we’re all different in terms of our wallets, too.

But when asking my opinion, I’m going to try and present the considerations that go into making a judgement. If you can afford them, I’d guide you to the DS505 servos everywhere. Next best is DS505 on elevators and DS360 or DS415 everywhere else. The weight and speed of the model affect this judgement.

For the throttle servo, the DS90DLHV is all you need.

Other considerations

Beyond selecting servos, with giant scale models you have other considerations. For example, how to power the avionics, the ignition, and issues to do with long servo extensions. Bone up with these articles:

• Servo Leads & Extensions
• On the batteries John prefers using
• Why and when to add capacitance
• Regarding ignition and radio switches

Final thoughts

Allow me offer a few final thoughts. The right servo for your model is a reflection of yourself, your goals, your dreams, and your budget. We put a better grade of servos in your hands. But nobody can make you buy them. This, you decide for yourself.

Any questions? Feel free to reach out, we’re readily available;

• Telephone: 407-302-3361
• Email: info@promodeler.com

. . . maybe together we can suss out what’s best for you!

I’ll close with this, one thing’s certain, best is a race that’s never finished. Best right now? ProModeler, but far from David vs Goliath, we’re more akin to a flea on the elephant’s back in this battle.

Means we need your help. Presuming you like our servos, then do us the favor of taking one to a club meeting. Pass it around. Maybe even pull out a 1.5mm Allen driver and open it up – you’ve seen how they go together, there’s nothing to be afraid of. And please, show them to a pal.

But most of all, kindly grace us with a photo sharing your thoughts. What for? To put on the website, and within articles like this one. Basically, for telling the next guy what you like about our servos.

We’re Jones-ing for photos like this one because your favor is priceless and can’t be bought. We know this. So do others.

Last thing

Have you enjoyed this? If you like reading and are interested in learning more, then maybe find time to review more articles like this;

• On the batteries John prefers using
• About pots vs Hall Effect sensors
• On selecting battery packs
• Pro tips for improving your ARF
• Amazon servo vs DS505s
• Why’s my pack got two JR-connectors?
• Rip Van Winkle, on returning to RC
• How to guide a rocket using servos
• Phoenix Models 70in Strega guide
• Advantages of pull-pull via pulley
• Bret Becker: Mr. Top Gun
• Will ProModeler servos work with NiCds?
• How to determine flight time for a 2S850 LiIon
• Hangar 9 60cc Pitts S-2B servos
• Fear of loss, or how to stack the odds in your favor!
• When LiFePO4 is mistakenly charged as LiIon
• Idle thoughts regarding chargers

. . . and hundreds more. Best part? They’re all free!