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Feb 10, 2016, 03:28 PM
What could possibly go wrong?
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Build Log

RCM Trainer 60


Hi guys, this will be a build thread for the RCM Trainer 60 from the free download plans you can find easily on Outerzone, Aerofred etc. I've included them here for convenience. For some this would be a first trainer under the supervision of an instructor, for others as an intermediate trainer as a bridge to sports models. There are many good trainer kits and ARF's out there but most tend to the .40 size, so this would be a good choice for a first build from plans or if you want a trainer that's bigger than usual, as it's simple and robust, and uses a very "standard" construction.

I haven't been able to find a copy of the original RCM construction article, and the RCMplans site is now shut down. So I'm going to try to make this build thread useful to new builders who want to use this as a first scratch build but would like to have some guidance. Observe and learn as I make all the mistakes you are probably worried about so you don't have to Really there isn't much to go wrong with a design like this one. Remember though, this is an *advanced* trainer, with a symmetrical wing - the symmetry is for inverted flight for starters and it's an aileron trainer too. If what you want is the slowest, safest, easiest trainer to learn on, people have been telling me that a Telemaster Senior is the way to go. My one caveat is that it's a taildragger, unlike this one with a steerable tricycle undercarriage, which is recommended for beginners. But don't be put off, many people learned to fly on the RCM Trainer 60 over the years. As soon as you're ready to try something more ambitious, the same model is ready to move with you, and meantime just limit your throttle and control throws, an instructor can teach you on this one just fine.

From RCM's spec's the wing span is 58-1/2", wing area is 672 sq. inches and target weight is 6 1/4 pounds for a target wing loading of around 21.5 oz per sq. foot. That's relatively high for a trainer, so bear that in mind - it means it wants to fly and land a little faster than a docile beginner's craft, but is still self-righting like trainers should be. I'm considering extending the wing by adding an extra rib or two each side, so for example if the span was 66" the wing loading is then just under 19 oz/sq. foot, or at 72" it's about 17 oz/sq. foot, more like most trainers. There is no reason you couldn't extend the span or even build two wings, exactly the same construction but extended for your "easy" wing.

I've copied wing ribs and the 3 bulkheads (fuselage formers) to separate files so you can print them out to work from, without having to try to snip out these parts from the big plan or work over them. Believe me it's a lot easier this way.

I'll be using a Saito FA-82B 4-stroke engine with this, but there are many choices open to you. As a "60-sized" model most people would probably go for a .46-.60 2-stroke, or a 4-stroke would generally be about a .56 to .82 or so. There are many helpful people on RCG to help you with engine choice and any other questions you might have.

From these files, first thing to do would be to cut out those wing ribs and make a template of the "20 req'd" one - I prefer to make two identical templates out of something hard like aluminium or 1/4" marine ply, so I can sandwich many pieces of balsa together and cut and sand them to end up with a nearly identical stack of ribs. That tapered section in the other rib shows how it should look viewed from the front - I'm not going to build it that way, wait and see and don't go ahead and make it as shown. I'm intending to offer a 2-piece wing option so that part's getting modified. (EDIT - I've abandoned that idea for now. It's just an ordinary, 1-piece wing. Maybe one day I'll work out a 2-piece wing system but I'm not sure it's really needed for this model. The fuselage is bulkyier than the wing, though not as long, so you'll already need a sufficiently large vehicle to transport this one that a 2-piece wing won't really be needed)

Soon as possible I'll have some photos to show you how I went about it and a build log to go with it. Best of luck.

EDIT - I've altered this thread to use a more modern version of the plan submitted by ReelDoc. Apologies if you had already downloaded these files and made parts - I'll now be using this new version. The firewall is now different, if you've cut one according to the older file (formers.pdf) I now won't be using that in this thread, the fuselage will be parallel at the front instead so the firewall becomes the same width as bulkhead 2. The new file (Formers 16 Feb) is the one to use. If anyone's building without following this thread then you'll need the original dimensions so for those people I'm leaving the old file up... but to be clear, to follow this thread, don't use Formers.pdf, use Formers 16 Feb. Other than the firewall width there are no other changes (in the original file, note that I neglected to cut off the piece of balsa that goes under the firewall - another error, sorry. But at least the correct line is there, just trim to the upper of the two lines at the base of the picee).
Last edited by BernardW; Sep 21, 2016 at 07:23 AM.
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Feb 10, 2016, 05:19 PM
Registered User
Looking forward to your build. This was my first RC plane in 1973. It had a Fox Eagle I .60 and it flew great. I still have the engine.

Bruce
Feb 10, 2016, 07:36 PM
It's gonna be YUGE!!!
LVsoaring's Avatar
Bernard, bear in mind that the specs include the weight of radio gear of the day. It's safe to say your radio gear will be significantly less heavy, so adding a bay or two to the wing may be unnecessary to achieve the wing loading you're after.
Feb 10, 2016, 08:59 PM
A man with a plan
Balsaworkbench's Avatar
I'll second that. Also, a significant number of planes in the early 1970s were still covered with fabric and dope, so your plane should be lighter for two reasons.

Most of my planes built from old RCM plans are at least 10% lighter than published specs, and some even more so. Also keep in mind that higher wing loading numbers are acceptable for larger planes.
Feb 10, 2016, 10:22 PM
KC4JAJ
Jim Johns's Avatar
Nice project, BernardW.

I've built two of these - a Bridi Trainer 40 (identical to the RCM Trainer Jr) and a Great Planes Trainer 60. I'd suggest you do as the others have mentioned and build the wing per plan, as it flies just fine that way.

If I were buillding one from plans I would make a few modifications based on my experiences with these planes.
  1. Relocate the Elevator control horn. I can tell you from experience with my Bridi Trainer 40 that adjusting the elevator clevice with the hingle line at the reat center of the fuselage is a total pain! I'd move it outside the fuselage.
  2. Change the firewall to match the width of bulkheads 2 and 3, especially if not using hardwood beam engine mounts. This is one of the changes Great Planes made to make the model easier to build. They also stopped the fuselage sides at the firewall and used 3/16" sheet for the cowl cheeks.
  3. I'd use two aileron servos located In the bay between ribs 4 and 5.

These models also make great tail draggers and the conversion is very simple. The tailwheel hookup isn't the easiestwith the empennage hinge line layout of the RCM T-60, but it can be done. The attached photo is my old Bridi T-40 modified with conventional gear.

Regardless how you build it, it should be a fine flying model.

Jim
Feb 10, 2016, 11:52 PM
What could possibly go wrong?
Thread OP
<Shrug> OK, original wingspan it is. I did another thread asking for advice choosing this project and a lot of votes came in the for Telemaster Sr with that REALLY light loading, then looking around all the trainers I saw seemed loaded a lot lighter than the numbers came out for this one. But it's absolutely true that modern radios and coverings really should save some weight. It's already known as a good trainer so in that case, let's not mess with it.

ReelDoc, those bullet points all seem fine to me and I'd been planning on most of those ideas, except I wouldn't have worked out about the firewall until I got there. I'll check that out in more detail and probably list that mod specifically. How do the separate cowl cheeks attach then, if they're not just extensions of the fuselage sides? I'd have thought it was a pretty simple affair to keep the sides and doublers as one-piece and attach a commercial engine mount inside - or are those beams in the original plan needed to get get the front fuselage to narrow all the way to the extreme front?

1, the elevator horn, has got to go, I agree. I'll simply offset it to one side as is done on approximately 2 zillion other designs. 3, the aileron servos in the wings, with a very direct link to each is my plan, probably with servo plates between a couple of ribs and the servos on their sides as you say. I was considering separate flaps but with today's radios flaperons make far more sense.

A lot of the queries I've seen from brand new modellers have specifically asked for 2-piece wings so I'm looking for a design to straight-out copy, I haven't done this before. Can anyone suggest something, maybe as seen in other free plans? I thought I'd cover some other options like a built-up vertical stab, I'm just not a fan of slab balsa fins and tailplanes as thick balsa sheets often arrive warped from the store, it seems inelegant and maybe a few builders would like the option of something nicer to build. A truss or ribbed version should be no problem. Hadn't thought about tail-wheels but I see no reason why not, there are tail-wheel units you can buy that mostly take care of it for you, I'm planning on something like that for another build so I'll check one out for this one. But as it's aimed at 1st-timers the tricycle gear is usually suggested as the way to go - I suppose for someone wanting to step up to this as a 2nd trainer that would be a good option. I think these days the basic 3-channel trainer is less popular than it was, the popular trainer kits (or ARF's) I see are all at least aileron models.

Looking forward to this, I've been doing some work on those patterns, just home on a quick break from work right now so I'll hopefully get something finished and photographed for this thread before I lay me down to sleep. Cya then.
Feb 10, 2016, 11:57 PM
A man with a plan
Balsaworkbench's Avatar
Regarding the elevator clevis inside the fuselage: I would build it per the plan, and use a DuBro EZ Connector on the servo. Then you make adjustments at the servo rather than at the elevator. Make sure you use the metal retainer, not the plastic one. The straight push rod is superior to a bent one. Although, if you're using tube push rods it's easier to make it come out the side. http://d2eqefissbzcnq.cloudfront.net...dub121-450.jpg
Feb 11, 2016, 02:31 AM
Registered User
High_Start's Avatar
Looking forward to your build.
Feb 11, 2016, 07:28 AM
ARFs Are Me
TomCrump's Avatar
This should be a great project, and I commend you for taking it on.

Like many of the others, I suggest that you build it pretty close to the plans, with few modifications.
Feb 11, 2016, 08:44 AM
What could possibly go wrong?
Thread OP
Quote:
Originally Posted by TomCrump
This should be a great project, and I commend you for taking it on.

Like many of the others, I suggest that you build it pretty close to the plans, with few modifications.
Thanks Tom and everyone, yeah that's my intent, as close to original as possible. The only changes will be things like using a store-bought engine mount instead of wooden beams, that seems pretty obvious to me as it's a better, more flexible installation, it's easier and simplifies the model. I'll alter the linkage to the elevator as discussed below too. I'll be specifying two aileron servos, wing-mounted, so you can program them to act as flaperons. I think that's a good feature for trainers to have.

One change I doubt anyone will mind is that I can't see any sign of shear webs between the spars, which seems strange since it uses separate upper/lower balsa spars, not hardwood, surely by themselves that's nowhere near strong enough. Maybe it is since there's LE sheeting and cap strips... in any case, I think they should be there a) for peace of mind and b) because first-time builders will certainly be seeing them again and again if they keep building balsa/ply models after this one. It's a learning exercise for them and myself as much as a matter of just getting something built.

I'm going to aim the build thread at first-time constructors, even though not everyone following will be in that position. I think this plan with a thorough and introductory step-by-step guide to follow could help some people. I'll do my best to show how to do it with the fewest and cheapest tools and outlay for parts. I'm thinking of young people with little to spend, or maybe pensioners or retirees in the same boat. I got back into modelling because I'd been laid off and the boredom was terrible, but I had next to no income, so I had to buy small amounts of balsa OR a cheap tool every 2 weeks and that was my operating budget... a young person working part-time at an entry level job might not have any more than that to spend either, and this is a good model for someone starting out so let's keep it affordable. Likewise, I'll assume the builder doesn't have access to unusual power tools, especially table saws, scroll saws and so on... heck, all I've got's a power drill myself (actually I have a Dremel-like thing which I've barely used, but for that reason I know I can work around it and not require the builder to have one). As I go I'll specify what tools will be needed. Wish I could predict right now everything you'd need and include a complete materials and parts list but sorry, I'm not that experienced myself. But I'll try and work out some sort of estimate and post it soon.

OK enough posting, I'm going to go and make stuff and take photos so that hopefully tonight I can get the thread started. I've got a good few days completely free coming up to spend on this so I will be kicking my own butt (you should see me do this some time, it's even better than it sounds) to get on with it. I'm a terrible procrastinator, in fact I am the PRO-crastinator, but I will be using this thread to push myself along, on the assumption someone out there actually wants to use it to build a model. When it's done I'll compile the thread into a new construction manual to go with the plan and offer it up to Outerzone etc. where I found it. There will be photos and diagrams along the way too.

See ya soon.

EDIT - hey, I see there's already a fair few downloads from this thread of the plans and the templates I copied from them, maybe someone IS interested after all. If so, please make yourself known and ask all the questions you want, or go ahead and PM me and I'll do my best to help. If you're happy to post your questions here then more and smarter people than me will be able to help too.
Feb 11, 2016, 09:10 AM
AndyKunz's Avatar
I have built the 20 size at both 20 size and UMX size. Build it per the plans and it'll be indestructible.

The thread linked above has photos of both planes.

Andy
Feb 11, 2016, 10:58 AM
What could possibly go wrong?
Thread OP
I read that thread, I am no way going to be able to quickly whip up a wing while the glue for the fuselage dries, and I doubt any first time builders will either, but I appreciate the link. Trainer 60 is considerably bigger of course. I'm starting modelling again after many years away so I have nowhere near your experience, so I'm going to do things in baby steps so I and any new builders who may be following can check what they're doing in a fairly fine-grained fashion.
Couldn't spend a heap of time on it tonight but I do have a first post, here we go...
Feb 11, 2016, 11:43 AM
What could possibly go wrong?
Thread OP
OK here we go with the first post of my RCM Trainer 60 beginner's build, meaning by a beginner for other beginners. Actually I've had some recent experience so I'm confident to share it for anyone who wants to try this model as their first build from downloaded plans. The way I do things and the order I do them might not be the same as you've seen elsewhere, but it works for me and I offer it as one way to build this model, you could vary it if you prefer.

Before I forget, as a rule whenever there's a printed line to work to, the ideal will be to cut to the *middle* of that line. They are generally thick enough to affect the dimensions and you have to standardise somehow; right or wrong, that's how I'm doing it. One other rule - *always sand EVERYTHING* - it makes adhesives bond better, gives sharper corners and flatter edges, and most importantly, impresses everybody and looks great. Fresh, smooth surfaces will look infinitely better than dirty, furry surfaces covered in glue smudges and finger-prints.

First I'm going to recommend a method for making wing ribs. The method is to cut two formers, as identical to each other as you can make them, then sandwich a stack of balsa between them which will become your wing ribs and shape them using the templates as guides. They need to be held together somehow so they stay in place while you do that. There are variations on this method, and the downside of mine is that you risk damaging the templates as you shape the ribs, but that encourages you to be careful and take your time!

Cut the rib from the paper print, accurately, and mark around it in pencil on two pieces of your template material (I used 1/4" marine ply, I've also seen thin sheet aluminium or galvanised steel sheet used, cut with snips and ground or filed to final shape). Rough-cut the two templates out. As I made mine from ply I used a coping saw, the ideal power tool would be a scroll saw but I don't own one (we're assuming the builder needs to spend the minimum here).

Next, I lightly sanded one side of one piece with medium grit sandpaper (180) and made sure to clean all the dust away. Using spray contact adhesive, lightly coat that face and the back of your paper rib. Let them go tacky for a few minutes, then you get one chance only to stick that paper rib on without creases or misalignment. Rub it down flat with a scrunched cloth and let it dry per the glue's instructions; best to clamp the paper between both formers and weigh them down. The light sanding gives better adhesion.

At this stage they're still only roughed out, but I'm out of time to work on them. For the next post, I'll be clamping the formers together and shaping both at once until they match the outline on the paper guide. There are those two notches for the spars too, a coping saw will do these (if you're not familiar with this I'll get some photos for next time) or again a scroll saw, which would be better. You *don't* want them shifting against each other while you're doing this. I use spring clamps, a few at a time, so I can move one out the way as I get to that section leaving others to hold the stack together - remember you want two identical formers. Before we're done, we need to drill these formers for a guide to go through both and all the ribs to keep them exactly in place as we shape them. It's late where I live so I'll get photos of these steps tomorrow and post them. There will also be tips on how to sand properly, including getting a nice flat edge around those formers at 90 degrees to the front face; that's important everywhere.

Yes it's long-winded but I did say I want to be thorough for other beginners. If you're having any difficulties or not understanding the posts, just ask. Good luck.
Feb 11, 2016, 01:36 PM
Registered User
I would consider the engine choice carefully. While the model is a "Trainer 60", it isn't really a 60 sized trainer (using current engines). Glow engines have advanced considerably since the Trainer 60 was designed. It was designed for 40-61 sized engines that were available back then.

The model is smaller than the 40 sized trainers designed for currently available engines. It should be a hot rod with a modern 40-46 sized engine. I would also be cautious about engine weight. Most trainers are designed for plain bearing engines, and need tail weight to balance properly with a ball bearing engine. This model being smaller, will probably require even more tail weight than current trainers, if you choose a ball bearing, or 4 stroke engine. I am not even sure if the engines specified on the plans had mufflers. If they didn't, a modern engine (with muffler), will probably make balancing the model even more difficult.

Might I suggest, a nice plain bearing 40-46 engine for this model.
Feb 11, 2016, 02:36 PM
ARFs Are Me
TomCrump's Avatar
Quote:
Originally Posted by AndyKunz
I have built the 20 size at both 20 size and UMX size. Build it per the plans and it'll be indestructible.

The thread linked above has photos of both planes.

Andy
I agree. This design was built and flown by many, over the years, with success. I don't see a need to add extra weight, like sheer webs.

As I remember, the model flies well, but it builds on the heavy side.


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