Balsa skinned lightweight honeycomb prof...

Wondering if anyone has tried to use a
balsa skinned lightweight honeycomb (nomex perhaps)
for a profile fuselage. Was considering
experimenting with my next ship. Thought
one could construct a very light and rigid (although
not cheap) fuse between 5/8" and 3/4" thick…maybe
even hide the control horns/pushrods inside. Your
thoughts?

Larry Cunningham has the answer to your question(s) on the plans to his Mo'Best (sic?) profile design.

I really hate to say it, but the leftie (Larry C.) managed to come up with some really neat features on this model. Very much worth getting the plans--readily available from PAMPA Products--even if you do not plan on building the model.

To the rest of you: Please, please do not tell Larry I had even the slightest of complimentary things to say about him and/or his design skills. After all, as we all know, as Larry certainly knows, "He doesn't know that much."

Apologies to those who do not get the inside joke.

Separate posting for no good reason.

But you might consider skinning built-up balsa construction with 1/64" ply on both sides. Not nearly as heavy as you might think, hugely resistant to twisting forces, the downfall of a great many profile models.

I'm familiar with Larry's Mo'Best and really
like the techniques/design; however, his aft fuse
was a truss construction, not honeycomb. Additionally,
I believe in later discussions of that technique, some
found it subject to warp. To
my knowledge, no one has tried the honeycomb technique yet. The
material is widely used in aviation and sports equipment.
Thought it could find another unique application in
a profile stunt ship.

Roger,

Could you tell us more about "nomex" or any other honeycomb material you have in mind. Such as the size of the individual honeycombs, weight of the material, sheet size availability, where to get it, etc.

I too have an interest in honeycomb. I would believe if it were as light as styrofoam, and could be cored and airfoil shaped, there may even be no need for a spar, if one were using it for a wing.

I'll do some more research...I know there
are several types (material, size, weight).
I'll post again when I have more info; looked
into the material several years ago when I was
doing custom furniture-it is also used
in table/countertop fabrication. More to follow.

I believe that RC pattern flyers have been or are still using honey
comb wings for a number of years.

LAST EDITED ON Aug-20-03 AT 01:09 AM (CDT)
 
Windy's tapes show him and Dave Midgley molding stab and flaps in nomex and CF. I don't doubt the result is incredibly stiff; I don't know about the weight. The materials are quite expensive, Windy even uses post-cured epoxy resin, exotic stuff.

They had some rather beautiful machined metal molding fixtures. I personally think this technique is completely impractical for the average modeler. An unnecessary.

I think an excellent practical alternative is the one described by Tom Morris for his profile Cavaliers, with white foam as a filler and the 1/64" plywood sides. It can be argued that white foam has virtually no strength, but it serves as a filler for the framed area. It is the 1/64" plywood which is so tremendously strong.

In my latest Mo'Best design, I still use diagonal 1/8" sheet balsa formers in the aft fuselage area, instead of foam. Again, they serve only as a surface to plank over with the plywood sides. They are not the source of much torsional or bending strength.

The original Mo'Best plans show diagonal balsa planking; it turns out this is a bad idea, and has a tendency to twist sometimes. To say nothing of being about 1/10 as strong and stiff as the 1/64" plywood.

I think maybe the white foam filled, planked with 1/64" plywood technique was developed initially by Tom Farmer. Someone can correct me if I'm wrong about that. Whoever came up with it, I salute and copy him.

Oh yeah, just my opinion, but I feel putting the control system inside the profile fuselage is more trouble than I'm willing to go to. However, one clever implementation I heard of used a Golden Rod flexible linkage, which solves a lot of routing problems for an internal pushrod.

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"Try not. Do, or do not. There is no try." -Yoda

The "built up profile" is an old trick and can be amazingly strong and light without resorting to fancy materials.
Internal framework with 1/16" balsa sides then doped and covered with Jap tissue or silkspan is all you need. It is astoundingly tough for a balsa structure) and very rigid when done- light too...

I've had some experience with nomex panels, but for non-modeling applications only. Great stuff, but kind of pricey. I've used these folks before, you can check it out:

http://www.wtp.net/DBEST/hcomp/nomex.html

Seems to me that similar results can be obtained using the structural sandwiches suggested here; foam. balsa, ply, etc. for a lot less cash.

I've used Nomex and rigid foams before.
Nomex in particular, is quite amazing in the stiffness of the resulting laminate, but it has two major drawbacks.
1, its expensive and 2, its really hard to glue to a dry skin.

Because the honeycomb is made of paper thickness walls in a 1/8" hexagonal 'grid' there really isn't much gluing area. Of course this is no problem with carbon/glass because the skin is full of sticky resin anyway.

Also, because the core can only take shear stresses, the skins need to be pretty tough to handle all the bending and direct stresses. Go with the 1/64 ply or some reasonably hard balsa, 2lb Nomex and try appling epoxy to the nomex face with a roller or the like. Go for it!

A.

Not to rain on anyone's parade, but I have to wonder at the act of throwing technology at simple profile models. We already have a superior type of structure: Built-up, full fuselages which eliminate all of the problems inherent in profile models. For example, no one to my knowledge has ever attempted a profile Impact; it simply would not be a worthy project.

If one simply must build and fly profiles--and I don't care at all what the reasoning might be--it seems beneficial to concentrate on the positives (quick building, ease of repair, inexpensive) while not cluttering the situation up with hard-to-find components, unproven technology.

That's why I suggested sticks laminated with 1/64" ply. A little tricker than standard, easy to do, cheap, and immensely stronger.

Larry, I don't think the Golden Rod trick would be worthwhile. Yeah, the installation would be easy enough, but there is a certain amount of "stiction" to these things.

I once built a batch of AMA (Fast) Combat planes that had this type of pushrod running down the center of a 1/2" balsa boom (laminated on both sides with, ta-da!, 1/64" ply) and while it did work in that application, we Stunt Guys are just a bit too snooty for such. Plus I don't think the more sensitive-handed amongst us would care for the feel of the controls.

While I have no ego involvement in the idea of using 1/64" ply in all manner of places, it seems as if I do remember mentioning it--possibly in a Bad Boy Stunt column--and within an issue or two seeing the same thing presented by others.

Coincidence? Probably. After all, I have never, ever copied anyone when it comes to model airplane stuff. Well, except for PTG. And Rush. Yeah, Walker. Randy. Godzilla. Aldrich. Buck. Ted. McClave. Windy. Rabe. Oooops, this list might just get kinda long, kinda quick.

I agree with Dan. Although I'm all for improvement in profiles, and can see going to some effort for an extra good competition ship, once the effort involved in making the fuselage reaches a certain point, you're putting lipstick on a pig.

Yes, the built up fuse requires a little more effort with top and bottom blocks, cowls, cockpit details, etc. But (particularly after molds have been made!), it becomes more worthwhile to make the built-up fuselage. And it can be built lighter than the equivalent profile. It virtually always will perform and look better than a profile fuselage.

I find the 1/64" plywood planked side method a good compromise for a profile designs, not much more effort, just a little more expense, and much improved performance.

Dan, I suspect you are right about the Golden Rod - fine for servo drive, but not for a CL stunt control system. I was told that it operated 'like butter', but the slightest drag on a stunter control system is adverse (to me).

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"He has the right to criticize who has the heart to help." -Abraham Lincoln

LAST EDITED ON Aug-20-03 AT 07:01 PM (CDT)
 
>I find the 1/64" plywood planked side method a good
>compromise for a profile designs, not much more effort, just
>a little more expense, and much improved performance.
>
>Dan, I suspect you are right about the Golden Rod - fine for
>servo drive, but not for a CL stunt control system. I was
>told that it operated 'like butter', but the slightest drag
>on a stunter control system is adverse (to me).
>

Aw Dan, I'm sure you might have mentioned the 1/64 ply technique. But it might also be a simple case of parrallel development. You see, I was talking to Tom Morris at the VSC, I think it was 5 or 6, perhaps earlier. We were talking construction methods, and I mentioned how strong the wing was on an RC ship I'd built. Foam skinned with 1/64 Ply. I mentioned that I thought the method would build a very strong profile fuse, the rest is history my friend. Tom went home and built one that way. So for the record, it was Tom who should get the credit as we were just too lazy to do it ourselves......:-P

Larry,

I've often wondered about using the RC type golden rod system for CL. Richardskits has a Korean warbird, the Navy Panther fighter, I believe, with a T tail. It was originally designed with the carrier event in mind. He uses that system for elevator control. Says it works great. I can see some advantages to be gained if this is true. Linearity for the flap to pushrod link could be improved, especially when the elevator is mounted somwhere outside the magic geometry.

I'm wondering why everything is spinning around?

John,

You are right on all points. However, you took the bait in being the first to actually date Tom's use of 1/64" ply on fuselages.

Ahem. My BMA Combat planes (Fast) used 1/64" ply doublers on the center rib of foamies, plus the laminated boom w/integral pushrod. Okay, not comparable. But my Slow BMAs did have a fuselage and it was a laminate of balsa and 1/64" ply.

Built the LAST of these guys in 1989.

Now if I can just remember from whom I copied the idea...

>John,
>
>You are right on all points. However, you took the bait in
>being the first to actually date Tom's use of 1/64" ply on
>fuselages.
>
>Ahem. My BMA Combat planes (Fast) used 1/64" ply doublers on
>the center rib of foamies, plus the laminated boom
>w/integral pushrod. Okay, not comparable. But my Slow BMAs
>did have a fuselage and it was a laminate of balsa and 1/64"
>ply.
>
>Built the LAST of these guys in 1989.
>
>Now if I can just remember from whom I copied the idea...
>
>Dan Rutherford

Well, we won't have to argue as to how tough those fuses get with 1/64th Ply on them. Very inovative for the dark ages my friend. Whoever that guy was, he was thinking good.

I still will have to give Tom the nod for adapting skinned foam for profile stunters though, and, they are light, stiff, and not that hard to do. I think we'll both agree to that.

I'm wondering why everything is spinning around?

If Howard Rush hasn't tried this yet, I'd be very surprised.

The man has an autoclave for curing prepreg in his basement!

>Could you tell us more about "nomex" or any other honeycomb
>material you have in mind. Such as the size of the
>individual honeycombs, weight of the material, sheet size
>availability, where to get it, etc.
>
>I too have an interest in honeycomb. I would believe if it
>were as light as styrofoam, and could be cored and airfoil
>shaped, there may even be no need for a spar, if one were
>using it for a wing.

Kaz Minato showed up at the Nats a few years ago with a molded wing made out of this stuff. But it wasn't constructed the way you're thinking of. Instead, it was a hollow shell, the skin being two layers of carbon fiber (or glass) separated by honeycomb. If you look at the wing's surface, you can see the honeycomb through the skin.

http://member.nifty.ne.jp/bluemax/BM99build.html

They use this construction for a lot of types of models, most notably sailplanes and pylon racers.

LAST EDITED ON Aug-21-03 AT 00:51 AM (CDT)
 
"lipstick on a pig". Oh yeah, and eye shadow, pink panty hose, twelve beers. Ok, I can see it.
Isn't the Corvette floor board made up of honey combed carbon fiber and balsa? Find a wrecked Vet and salvage the floor board.
Back in the 70's, I built a hollowed profile racer for 1/2A Goodyear and the controls were inside the fuselage. It had a "T" tail. (Rivets). Al Culver showed me how to do this and we used 1/64th ply in parts of it. He worked for the Boeing at the wind tunnel building models for years. So the technique has been around for a long time.

Geez, for history's sake, my friend Norman Vanderschel was laminating profile fuses with 1/64th plywood and Goodyear Pliobond contact cement in 1953, near as I can tell. Got the MAN article to prove it. And Bare has Van's Flex-i-bull-it plans for sale now.