Foam, composite materials and the future of stunt...

When I posted the question about the foam wings I got a LOT more then I bargained for!

All off a sudden I started realizing that balsa is on the way to become something obsolete.

I have been thinking, and I arrived to the conclusion that these innovations mightl not start in the "stunt community".

Let's face it, the majority of us stunt guys are kinda conservative, reactionary and prone to nostalgic feelings, and this is no put down, it's just what I have been able to observe.

The only cathegory of CL where there are "old time" contests (OTS, Classic, etc.) is in stunt.

There are some reasons for this:

In combat the goal is to cut the other guy's streamer as many times as you can.

And that's it.

If a better engine comes up, good bye old engine! If one finds a more effective material to build his wings, good bye old stuff!

An "old time" combat match would sound absurd.

Imagine: "Let's get us some old combat engines, some metal tanks and have a ball!"

Is speed, the goal is to run your plane as fast as possible. Same philosophy. The king is dead? Long life for the "new king", be it an engine, a prop or a new material.

But in stunt the very goals of the sport are very subjective. We are not concerned so much about ends (we are after a "beautiful" pattern), and the means have an importance that will not be found in either combat or speed.

That explains, for example the "Fox .35 cult", the importance of the 4-2-4 beak, etc.

OK, OK, the Fox has a nice sound, it breaks nicely into the 2 cycle, but - let's face it - there are dozens of more efficient engines around.

If I post a dumb note saying that PA or Ro-Jett engines are no good people will just laugh at me, but if if a commit the sacrilege of badmouthing the good old Fox.35 I might have a mob at my door, ready to tar and feather me.

Here at Rio de Janeiro I was the first cat to use a low pitch-high rev setup, and the first weekend I showed up at the field with an OS.32F lauching at 11.500 rpm with a 10 X 4 prop a lot of guys felt personally insulted.

I even got a couple of phone calls by concerned friends trying to "bring me back to my senses" and do the "right thing"- "get an OS.40FP and launch at 8,500 - 9,000 rpm, like normal, honest people do"...

The only guy in Brazil to use a piped engine some 4 years ago was Paulo Gomes, a PA.40.

I just got the news that this cat Fontenelle - who has a very precise patern - bought that PA from Paulo, that now uses a PA.61. They will both be at Muncie this year.

But in general folks here at Rio are afraid of tuned pipes as if the devil himself - and not Billy Werwage - had developed them. A guy will spend a load of dough to buy a ARF Cheyenne (around US$500 ) but he'll say that "pipes are expensive". Doggonit, a pipe costs 80 bucks, and an OS.40VF can be bought for a 100 smackers!

Similarly, I believe that we are clinging with our hands and teeth to balsa and not getting wise to the fact that progress is unavoidable. The stuff Ron posted at the Foam thread made an impression on me.

Building a balsa wing is hard, time consuming and you never know if it's gonna stay straight. And if you want another wing you gotta do it all over.

If guys like Ron and some other heretics keep on trying to make wings (and fuelages) that are guaranteed to be straight, and that once you have a mould can be duplicated in a somewhat "industrial" output (repeatable) this would, for instance make aerodynamic development a lot faster.

After all, one of the keys to a sucessful design is doing, re-doing, changing a little bit here, a litle bit there, ya know, just like Al Rabe did in order to get himself a Mustang that flies like a stunt ship without loosing the scale look.

There is also another component in this equation. I imagine things might get to a point that one will not afford or be able to produce the parts needed for a "new materials" ship. Just like one can't laser cut his ribs, we might have to hand over a BIG slice of the "craftmanship" to specialized guys.

"Oh, but this is going against the "spirit of stunt", what about the BOM?

Will we stick to balsa sheets and sticks (the pun is intentional) in order to preserve tradition?

The designs that gave birth to the Spitfire were developed on the Schneider Trophy races. At first the £1,000 were enough to build a racing plane, but as technology developed the price soared to millions. Homemade racers were no more competitive.

I am not saying that prices will become prohibitive, but maybe an airmodeler's role in the building process of a stunt ship might change from cuting and gluing balsa to the use of computer aided design.

Just some food for thought...

Ion

.

Just what I need, more things to think about.

Let me give you something to think about instead. You say, "All of a sudden I started realizing that balsa is on the way to become something obsolete."

Look at this the other way 'round. Let's say we have been using the cookie-cutter approach for years, plus all the hassles, and expenses, inherent in fighting the weight of epoxies.

Not only does your latest model look like the one built five years ago because it came off the same tooling, several of your friends have the same exact model as well.

Now imagine that just last year someone discovered balsa and that we can send small crews out in the jungle to get shiploads of the stuff. This "new" material has a decent strength to weight ratio, hand tools are all that is required to work it, it can be cut and/or formed into some great shapes, we can easily afford it...well, you know the list, having used balsa for years.

Of all the basic materials we use in our models, balsa above all is the "New, Improved, Miracle" material. Except it's not new and not improved. It is, however, a miracle material, or at least something quite close.

Just out of curiosity, do you know the per-cubic-foot weight of the best carbon fiber/epoxy sheet? When you find out, do the math,compare it to even 8-pound balsa and then reconsider your position on balsa soon becoming obsolete.

I'd seriously consider Ron B's techniques for producing vacuum bagged composite skins. They can easily be done in a home workshop(no 5 axis CNC mills required). Once you learn how I suspect it is a good deal easier than a lost foam wing. And the bonus is that it comes out just about ready for final painting!! No hours and hours of sanding multiple coats of dope!! But you still are betting the barn on that final layup and vacuum bagging. Make a mistake there and you lose a lot of work.

Sorry, but there is, in fact, quite a lot of "vintage" in other events. Vintage combat (with Voodoos, Winders and such) are becomming popular. There are nostalgia carrier and speed events. While not nearly as popular as vintage stunt stuff...yet. it is becomming more common.

That is just what we plan on doing!!

Actually, we've been doing that locally for the last three years. No metal tanks but bladders, vintage engines, balsa airplanes. Interest has maybe leveled off over the last year. Despite doing fairly well in the contests, I am dropping as I just no longer feel comfortable at the speeds.

Getting old is not good. In the year 1900, US male life expectancy was 49 years old. We are fooling around with mother nature with modern medicine etc. and this is not totally good, IMO.

Ron B.
F4Fguy

SO do I!!! If I thought for one minute that what I and others are doing with composites would increase the ARF market,and especially if I thought it would in ANY WAY effect the B.O.M.,I'd throw my vacuum pump away and make model transport cradles out of all the foam so that I could carry my BALSA models in safety.Everything I've done is easily "doable" by any modeler with the desire to do it.It's simply another approach to engineering the structure of a model airplane.I happen to like scale stunters.The best way I see to duplicating the appearance of an all metal airplane is to make it from materials which can give that appearance.The scale guys simply use "Flight Metal",accept the weight,and get on with it.Stunters can't do that.As Dan points out,carbon is heavy(well,not really,but add epoxy and you get porky fast).So,in order to use composites,you have to find ways to use it economically weightwise.One way is to take advantage of the tremendous rigidity and strength of these materials.One way of doing this is by using much thinner sections and eliminating unnecessary internal support,which you no longer need.The way to look at these materials is not to try to use them as part for part replacements.A good example of that approach is the use of carbon OVER balsa in stab spars as "insurance".This makes the spar wonderfully strong,but adds unnecessary weight.You can design a perfectly good wood spar at the same weight,or you can design a composite spar at the same or less weight.But the real point of all this is to do it yourself.This is the challenge.This is the real legacy of our hobby/sport.From day one it was people doing things THEMSELVES which hadn't been done before.It's certainly not all about the perfect pattern.If it is then it will all be over the first time some P.W. of the future flies a 660 pattern(or whatever the total is now).When that day comes,and it will,there will still be people trying to build lighter,better flying,better looking ,better finished airplanes.

One of the finest things about our little community is that there are very few who keep secrets.Everything I've done is available to anyone who wants it(there are those who don't want it),as is the case with most of the modelers I know.

I've been doing this for going on 65 years now and there are only one or two things I'd change.One would be the likelihood of rain on flying days,the other would be people who don't do their own modeling.

Hey Mitch! Where do you buy your puffery? Down at the White River Fish Market?

There's a supermarket here (Carrefour) that has a section called "Butchery". Those wacky French!

WOW!

You have Carrefour in your couintry?

here too!

Dave, I'm not tlaking about the present technologies. I'm thinking further in a not so far future, when more stuff will be developed.

I got thee ideas from the things Ron wrote on the foam thread.

\>Also, modern top end FF models, F1A/B/C really dont have
>much balsa in them at all.
>
>As for stunt models, this type of construction has been
>available for about 10 years - you can even buy a RTF F2B
>from the Ukrainians, foam core sandwich wing shells, balsa
>core sandwich fuz etc.

I know that, Dave, I saw one of those Iatchenko ships and I was amazed.
It fits in a little box!

>Owning one of these, I can say that structurally it is
>superior in every way to a conventional balsa airframe -
>lighter, stiffer, no warps, much more robust at the weight
>and painting is a breeze.
>
>The downside, in my opinion a very big one - is the
>investment in tooling required, I reckon it would take me 2
>years to produce the tools/moulds to make an equivalent
>quality structure.

That's why i said that a huge slice off the nuilding wouldbe done by specialized guys, just like laser cut parts.

>
>And, as DD said, with that investment in time, the next few
>models are going to look pretty much the same. With TR
>models it is common to share the tooling among groups of
>flyers, for this reason.
>
>I have a design on the drawing board right now, using this
>type of structure - but I'll be building a balsa prototype
>first!

\Well, the first MERLIN engine was built out of hardwood. Then they made the parts.

Ron B.
F4Fguy

Ion:

I refer you to my post#9 above.the whole point of my work is to find methods which can be practised by Joe Bellcrank.Tooling?It costs a little time to make the buck,about an hour to cut the foam,if I have the templates add an hour, if not add another 20min. 1 hr.to skin it with mylar.Add the spruce trailing edgefor another 15min +wax and parting agent at 15min..The buck is finished.Wing skin wood assembly,an hour. Cut two carbon or kevlar skins for inner and outer surfaces of the molded skin and a mylar cover/parting sheet,all from the same pattern,1hr.That's all you need to make a composite wing skin,And the plug will last indefinitely.Where's all this "tooling cost"?A fuse buck is a little more complicated,but still well within the capabilities of the average modeler.I can buy all the materials for a molded wing at a cost less than twice the cost of those for a built up balsa wing,and I'm going to spend a lot less time and money finishing it.It's interestingly ironic that to use high tech materials for modelling involves mostly hand work.It's also ironic that most of the cost of a purchased composite part is in the handwork you could do yourself.

As to being "stuck with one design",allthe tooling is cheap enough that you can toss it if you want to,and do smething else relatively painlessly.On the other hand,if you want to,you can make more copies than you will ever need.If you're doing this to make a buck (no pun intended)this is not a good way to go,but it wasn't intended to be.I've never sold a component and don't plan to start now.I've helped guys cut wings and shown them how to do it,but if they ask me to do it for them,I tell them to take up R.C.

Sorry but that's the way I feel.

Oh, puhleeezze!!

Let's see here, the CF fuselage was 3 ounces lighter than the balsa unit, which implies some very thin carbon/epoxy skins. (You and Ion both need to find the pound-per-cubic-foot rating of carbon and epoxy in order to get a grip on what is involved here.)

Such a structure may well be strong enough to use in a CL Stunt model. But it would also be fairly easy to damage with nothing more than a healthy slap or two, let alone hitting it really hard with a fist.

This is one of those times when you should have first considered the source prior to passing along that which is most improbable.

Ron B.
F4Fguy

Gee,I never thought of that.Maybe that's what I've been doing wrong.I've never tried giving my airplane a healthy slap.I usually make it sit in a corner and take a time out when it doesn't perform well.

Seriously though,you're right,you do have to develop a new appreciation of the different"soft spots"in a composite airplane.But,thats no different than having an appreciation for open bays covered with silkspan.You just have to learn where the hard points are.I have to agree that,even if it was "12 times stronger"(which I SERIOUSLY doubt),it's not a good thing.At that strength, you've got way too much material,and weight,in the airplane.

The idea,as I see it,is not to replace balsa,it's to find ways of building better airplanes by using ALL the resources available.

>The idea,as I see it,is not to replace balsa,it's to find
>ways of building better airplanes by using ALL the resources
>available.
>
>Ron B.

That's it Ron you got it, as I said in my post, the best of both worlds balsa is light and carbon fiber is strong. Mix them together properly and you really got something. Hopefully light and strong. Also wood is one of the best vibration dampeners there is. Absorbing vibration is a good thing because it makes the rest last longer as opposed to cracking and self destructing if it's to stiff and or brittle.
I am in the process of making some wing spars right now that are made of balsa and laminated with .030 thk. G-10 epoxy sheet. Lighter than the original plywood spar but just as strong. Why do people think balsa is the enemy?

I do not want to argue with anybody, and I'm NOT defending any point of view.
This friend ot mine, Professor Romildo Bueno, one of the wisest men I've had the privilege to be able chat with, told me that "ideology will make one blind to truth".

The moment I grab an opinion and start defending it I'll loose any chance of learning something!

Please do not worry about hurting my feelings by saying anything against my hypothetical (yes, hypothetical) speculations.

BUT, since we're at it, you could be a nice fella and re-post some pics of the fantastic work tou have been doing over the last years.

Al Rabe does that every once in a while, and we all love it!

Don't "baby feed" us, please give us an indigestion..

Ion (post them pics, Ron!) Muniz

Whaaat...???

I went over to those pattern guys house. Their stuff is all composite. It is incredible. Way better than balsa.

I think your comments are out of line. Windy could build better than most of us with his eyes closed.

Votin for the Best of Both myself. Sure, we could all by preformed parts and forget about whittlin balsa, but where would the fun in that be?

Probably so,I don't build at all well with my eyes closed.

This is one of those times you might want to do a little of your own research yourself before you start in with such comments.

What a backhanded way of caling someone a liar. Why dont you just come out and say it?

I have handled the Miss Ashley carbon wing myself. I have handled the carbon fuse myself. They are excellent parts that are in the weight range of any good modeler's balsa parts out there for that size. The durability factor is not even in the same ball park. I have also picked up that plane a few times and compared weights to mine at 58oz and they seem to be very similar in feel.

What I dont understand is this fascination with it being superior to taking a slap or being hit with the fist. What does that prove? Anyway I have seen it on the video during production of the thing and yes he hit it and it was strong where balsa would have crushed. I really think he was just trying to show on camera the difference in the strength of the two types of parts. Anyway our models are not under compression but they are under severe torsion during flight. Go squeeze the wing on a Pitts sometime and you will notice it doesnt hold up so well yet it turns like a mother...hummmmm I wonder why? Bill Wilson here in Fort Worth uses an all composite fuse with no formers,1 layer 2.9 carbon and 1 layer .5 crows foot glass, and it is very easy to squeeze the fuse sides. However you can twist on the stab and pick up the plane with it. Same goes for a wing. It doesnt have to have this great ability to withstand compression just torsion. Thing is to get great torsional strength with balsa you end up with really good compression resistance. Best of both worlds huh?

One of the really cool things some people are deffinantly missing with the composite parts is the ease of repair. They dont soak up oil over time so clean it off and go after it with CA and POW you are on the way. Cracks, go right over them with a strip of stuff from the inside and keep on rollin'.

I am in the process of making a Female mold of a Geo Bolt wing right now. Yes it is not for building one offs or experimental stuff. But I plan to use this wing for a long time so I thought I would give it a try, besides I am so tired of finishing wood parts and all the filling and covering it makes me want to quit building planes all together sometimes. So far I have the male plug built and polished and I have pulled a couple of plaster molds off of it with no luck on parts that size. But tonite I did the epoxy gel coat and fiberglass. I hope it turns out. Oh and I dont think I have gone over a 100 bucks yet on this one either. Even with the two other pulls I tried for fun out of plaster and painters mud.

Most composite techniques are not for the putterer. you spend a lot of the time making stuff to make the parts, then finish sand the wood in the wing or something. After a lot of work you still don't have anything that looks like an airplane. Then the next afternoon you do all the layup and vacuum bag it or whatever, and the next day it hopefully comes out of the mold virtually done. Then if you find some error, like the epoxy didn't spread properly or the mold release didn't, go back and make a complete new part.

Most state-of-the-art composite techniques are 185 deg. apart from building a model. They are more designing and engineering a plane with a difficult, and expensive learning curve. Some of Ron's techniques are pretty nifty and a lot more useable for a modeler. When you talk to some of these RC guys about machining solid aluminm molds from blocks and $200 worth of materials in a wing it gets a bit unreal- all to save 1 lb. of weight in a 30 pound plane. With only 10 oz. or so of material in a 750 sq.in. wing(whether it's balsa or composite) we are getting to the point of being barely more than a coat of paint around some air. You can't get much lighter.

>I went over to those pattern guys house. Their stuff is all composite. It is incredible. Way better than balsa.

>I think your comments are out of line. Windy could build better than most of us with his eyes closed.

>The City Smasher

Godzilla,

I remain fully conversant and current in what the RC Pattern guys are doing. Your opinion that their models are way better than our balsa models is not an opinion I share. Also note a number of factors which separate the two events, even though there is some (limited) commonality.

My comment about Windy stands, and I don't believe it had anything to do with his building skills. The two are about as far apart as, oh, self-promotion and being able to lay down a fine coat of paint.

What if you're self promoting your ability to lay down a fine coat of paint?

Ron B.
F4Fguy

Phil:I agree most "state of the art" techniques go past dead center.My aim has always been to develop methods that Joe Bellcrank can use.I always use materials Joe can afford and probably has used,if not in the same way.As to time,it's all relative.My wing comes out of the bag ready to paint.My fuselage is one piece.

The molds are all foam,blue,pink,or spiderfoam(admittedly a little more costly but still readily available).I can carve a whole fuselage buck in the time it takes to do the top and bottom blocks in balsa.And if I screw up,I can whack out the offending area,bung in a new piece and get on with it.

Epoxies are West,Easylam,or even hardware store laminating epoxy. 0.010-0.014 Mylar for carrier sheets and wing buck covering is readily available from plastic supply houses,and from many art and graphics stores. It takes no more time to cut a core for a composite wing than a balsa sheeted one.All of these are cheap enough,and fast enough that they are very feasible for"one off"models.The fact that a material or process is unconventional doesn't make it"exotic".It simply means that you may have to learn some simple new skills to take advantage of it.

I use .02-.03 and .05oz.carbon,kevlar and glass mat,because any thing heavier is overkill,and because mats present no orientation issues.Sure I could get more strength and stiffness,but its not necessary and only adds weight.Besides,remember Joe?He's generally going to balk at $180/sq.yd.for 1oz.carbon cloth.

Incidentally,you don't even necessarily need a vacuum pump.My first bagged wing was done with a plastic garbage bag and a vacuum cleaner(big momma was NOT amused).Hell,it'll pick up a bowling ball won't it?(before you all write in ,I'm aware of the trick)I don't recommend it,but it worked.

As they said in the sixties"different strokes for different folks.

Trick?? Please elaborate.. I don't know about the bowling ball trick, and it'd be a neat thing to do at parties..

I've wondered about this in the past, whether you can actually use a vacuum cleaner for bagging. I understand, with most vacuum bagging setups, you pump the air out, squeeze off the tube, then you can turn the pump off. Did you leave the vacuum cleaner running the whole time? (I can see why big momma wasn't amused, if so...)

I'm pretty tempted to try this.. I've got the mylar, I've got the carbon and kevlar veil, I've got the .5 oz. glass cloth. And the trash bags and vacuum cleaner. Hmmmm.. the neighbors might come over wanting to know what all that noise is, though...

Ron B.
F4Fguy

Iskandar:

The "trick" is to make a funnel adaptor for the vacuum hose,such that thr area x force(vacuum)=>than the bowling ball.Vac salesmen do it all the time on TV.Yes,I had to leave it on,there were too many leaks.I wouldn't recommend cloth of any kind ,unless you've got access to bias cut material.the tortional rigidity of the finished part is too low.Mat(finishing veil)works better and is cheaper,it is randomly oriented.I havn't tried them yet,but I've got some vacuum storage bags for clothes storage and travel.These appear to offer a solution the vacuum cleaner/seal problem.

Regards Ray Lloyd.

Ron B.
F4Fguy

Sorry to rain on your parade,Ray,but several people gave very specific answers to Ion's question.The answer is ,yes you can build a foam wing as light as a (conventional)built-up one I'll leave the "lost foam geodetic"form for now.However,it ain't just that simple.Building a light foam wing requires just as much dedication to doing it right,and using all the right materials and techniques as does building a light built-up wing.Otherwise this thread would have been about two or three posts long.To put things in a little perspective,the wing for my F4F-3,with flaps,controls,L.E.guide,tip wt. and box,tips AND finish painted weighed 11.8 oz.admittedly this was carbon ,not balsa covered.It's also 66"span and 735"2.Anybody who tries can build a foamer at the same weight as a built-up.A typical foam core wing,properly cored and covered with 1/32" 5# balsa,will be in the ballpark of 11 oz.ready to install.In addition, it will be straight true and will stay that way.Can some people build them heavier?You betcha!But they don't have to be that way.Is it easy,not if you do it right,but then neither is built-up,by the time you build the jigs and fixtures to get one straight.