Skeletonized Foam Airframes Thread - Page 5 - RC Groups
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Feb 12, 2011, 09:31 PM
Aircraft Designer Guy
AJWoods's Avatar
Originally Posted by derk
MITKid, that cub flies GREAT! do you think it would knife edge?
i think i may have to build one of those for my old sukhoi guts and paint the frame yellow so it at least has a half way scale look
Thanks, I've gotten a few more flights on it and really like it. It'll hold knife edge, but there's a fair amount of coupling.

I got some paint on it, and finished the little details. I'll revise my drawings and try to get plans up sometime next week.

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Feb 13, 2011, 10:33 AM
Headed to Naval Flight School!
PiperCub49's Avatar

I really love the cartoon scale touch with the engine detailing. Great idea!

Feb 13, 2011, 10:50 PM
Registered User
WoW these planes you guys are building amaze me. I have been flying for a few years now and just would like to get into this smaller scale. Where could you guys point me for electronics and planes for these types of birds. I really love the look of the skeletonized planes. It really shows of the work you guys put into it nicely. Anly help would be greatly appreciated. Thanks

Feb 13, 2011, 11:11 PM
QuAd FaNaTiC
Razors edge 29's Avatar

your cub rocks man; bravo
Feb 13, 2011, 11:56 PM
derk's Avatar
Chance, you want to look at the parkzone ultra micro planes. The 4site and sukhoi are the top donors for these planes.
Feb 14, 2011, 12:29 AM
Registered User

I already have a Sukhoi and its not much fun to me anymore could you point out some good and fun to build kits that i could use the guts for. I would love something very floaty that i could fly around in my small backyard. Thanks again for your quick response
Feb 14, 2011, 12:47 AM
Registered User
machinate's Avatar
I think maybe the best stepping-off point from Parkzone UM planes is the Dynamic Foamy Warlord. It's cheap, it'll work well with your Sukhoi guts, and it'll absolutely shame all the Parkzone/E-Flite micros for low-speed manners and aerobatics. It's also an opportunity to get used to building at this small scale without having to do all the work yourself, and since it's milled it gets you about halfway to these skeleton planes. Fly that around for a while to decide if you want to keep going with the extreme lightweight models. Then you can start going really nuts and looking at one of these scratchbuilds.
Feb 14, 2011, 04:22 AM
Fly long and land softly
Jim_Marconnet's Avatar
+1 to what machinate says.

I'm building a Dynex Warlord using a smushed UM4-Site guts. As he says, it's a whole new world of building light with really tiny pieces of milled foam, laser-cut plywood, and carbon rods. One neat thing that plane kit has is a small foam stand that you quickly assemble. It supports the plane off the bench, either upright or upside down, for construction, display, and repairs.

One thing that I think will be very important on a very light plane this small size is building some sort of safe transport box. Carrying such a plane to and from the car and the gym can be more dangerous than flying it. I was carrying a similar plane out of the house one time when I reached over to turn off the light switch. The wing brushed the wall and it broke in two! That's called Hanger Rash!

Feb 14, 2011, 01:32 PM
Registered User
machinate's Avatar
I've made some progress on the Elevon Shark I R Irv posted. This is 3mm Cellfoam88, Sharpie color, and heavy-duty Saran wrap stuck on with 3M-77. I don't like the mottled, inconsistent color from the markers, but painting at this size would have been too expensive and too laborious to justify.

The fuselage is covered on both sides, while the wing is covered only on top. Total airframe weight is about 14 grams; my scale doesn't do sub-gram precision so that's only a rough estimate. The surfaces are temporarily attached with masking tape, so disregard the little white overhangs you see along the hinge. Also, don't put masking tape on the covered side. It's stickier than 3M-77 and may therefore cause problems.

Now I just have to figure out how to brace it and how to mount electronics. This'll end up a bit heavier than Irv's, since I'm going to add an AP05, 2s 180mAh power system. Still, I hope to come in under two ounces.
Last edited by machinate; Feb 14, 2011 at 01:41 PM.
Feb 14, 2011, 01:42 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Originally Posted by machinate
I don't like the mottled, inconsistent color from the markers, but painting at this size would have been too expensive and too laborious to justify.
You might try "Short Cuts" spray paint. All my planes at the top of this thread us it. It's cheap, available in most craft or hardware stores, adds almost no weight, and is very quick to apply. Just dust it on before covering.

Feb 15, 2011, 02:51 PM
Thanks for the Fish!
aerogel's Avatar
If you lay half of a molded fuselage on your laser’s bed does it have the height to cut a frame out of it? Or it will only work on flat sheets? I.E Will it cut none flat objects?
Feb 15, 2011, 02:56 PM
Registered User
machinate's Avatar
Speaking of lasers, what laser system do you have? It's something I've always wanted, but when I start looking into them it's very hard to find hobby-level equipment in among all the industrial stuff. Yes, I realize even "hobby" lasers are quite expensive still, but even then it's hard to figure out what I'm looking for.
Feb 15, 2011, 07:48 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Without a fixture to hold half a molded fuselage it probably can't do what you described. A fixture that held it upside down and then manually setting the height of the cutting table would probably work. Whether it's worth it compared to cutting it out by hand I can't say.

My laser is a Universal Laser systems 30 watt 12"x24" bed table table top model. Cost was about $12k five years ago. Used lasers seem to go for about 1/2 price. And, there are now Chinese lasers. Epilot has some experience owning the Chinese lasers.

Feb 16, 2011, 12:12 AM
Registered User

Full fuselage approach

I worked up a folding approach for full-fuselage construction that might fit in here. I haven't used on any larger models but .025 and .05 durobatics works very well. It takes some lofting and layout that is best done in Cad but once done and committed to laser parts the build is a snap. The parts print pic is the laser pattern for a small 10" model. Note the red lines (not to be lasered!) and where they line up with the small straight lines (lasered just outside the parts outline. I bent a radiussed incising tool out of 1/32 MW and before I remove the parts from the laser nest I carefully run the tool along the red lines using the black lines as a guide for a straight edge. The incising (not cutting) tool track makes a simple and accurate fold line for bending the parts. The picture shows a fuselage that I have bent up.
I haven't used this technique for larger models, say, 3mm depron but some sample runs look good. The folded parts ,the interior bulkheads and Rx decks are usually .050 Durobatics in the tiny stuff. Alignment, squareness, positioning and assembly always comes out great.
Now, the caveat...the only way to make this work IMHO, is to lay it all out out in Cad or some method where some rather complex lofting and laser parts tweaking is possible. The actual dimensions after folding must be experimented with and used in the laser patterns.
Feb 25, 2011, 10:07 PM
Registered User

weight savings?

i am very interested in this method of construction. in your use of this technique have you been able to determine an average percent of weight savings vs all foam?
i'm on the 4th build of a "short scone", each time it comes out very tail heavy.
i've tried thinner foam, stick and tissue for the flying surfaces. i'm thinking now about using your technique on the back half of the fuselage.
maybe i can get the thing back to the 15 grams i set as a goal for auw.
thanks for the idea and for being a prime mover in this micro hobby.


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