Carbon Socking a 1.2M Speedo Thermo Fuselage - RC Groups
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Nov 29, 2009, 07:58 PM
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Mike Furcolow's Avatar
Mini-HowTo

Carbon Socking a 1.2M Speedo Thermo Fuselage


I'll try and document my progress on applying a carbon fiber/fiberglass hybrid sock to a new Speedo Thermo fuselage. The stock fuselage as delivered has a great shape, but is a thin fiberglass shell and very prone to cracking and breakage, especially in the wing saddle area. I'm going to use a lightweight, carbon fiber/fiberglass hybrid weave sock, and try and keep it as lightweight as possible, yet immeasurable stronger.

(Thread for carbon socking a larger, 1.5M ArtHobby Falco fuselage;
https://www.rcgroups.com/forums/show...php?p=10123947
Same technique, but simpler to apply, heavier armor)



Materials;

New Speedo Thermo fuselage, from

http://www.r2hobbies.com/proddetail....od=rcpl71016_p. Current cost is $56USD plus postage

I picked the Speedo Thermo fuselage because it has a good aerodynamic shape, is very small (scale for 50" wingspan), and has a molded-in vertical fin and X-tail configuration. The molded-in tail presented some real challenges for the socking technique as used before. I wanted to make a super-tough yet lightweight fuselage for lightweight floater wings, and also be able to mount small, heavier, faster, DSable wings.


Carbon Fiber/ Fiberglass hybrid weave socking material;
from Soller Composites @ www.SollerComposites.com. Great source for all things composite. I ordered the CF/fiberglass hybrid lightweight sleeve in a 1.5" diameter size and a 3-ft length. Cost is $2.99 per foot. It comes in all sorts of awesome colors! Take yer pick. Fuse diam is about 1.3".


ShrinkWrap tubing;
from Soller Composites, too. You want the treated shrink wrap for use with resins (comes w a release agent coating on it). You'll need two sizes, for the different tapers; get a three foot length of 1.6" diameter treated tubing, @ $1.18/ft; and a three-ft length of 1.1" diameter treated tubing, @ $.89/ft.


Epoxy;
from US Composites @ www.USComposites.com.
I have been using this stuff since a tip from Jack Cooper at LEG. It's similar to West Systems, and sets up crystal clear. It's not brittle when cured, and is somewhat more "subtle"; when stressed, it will scuff rather than chip. I used the 635 Thin Epoxy Resin mixed 3:1 with Medium Epoxy hardener.



Got it? Here we go;
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Nov 29, 2009, 08:17 PM
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Mike Furcolow's Avatar
I thought a lot about how to deal with the vertical tail. You could armor the whole thing (too much weight back there), or cut it off flush w the tailboom, then sleeve the tailboom with the proper-sized shrinkwrap, then build another balsa tail and mount it. Could have done that, but I love the little molded-in hole under the stab for the control rod--it's so cute. So I'll deal with it another way. I will shrink the larger tubing as much as possible, then split it above and below, and wrap it with stretchy black electrical tape to make the pressure for curing. Sounds kinky, but it worked out perfect! Just keep reading;
Nov 29, 2009, 08:31 PM
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Mike Furcolow's Avatar
Let the adhesive dry for about 10 minutes. Then carefully slide the sleeve back over the nose and over the sprayed part of the tail. Align the split part of the sleeve carefully along the masking tape line. Pinch it off at the back of the fuse, and s-t-r-e-t-c-h it forward to the nose. Re-apply another cable tie to hold it really tight. There's too much material to pull it down tight at the narrow end of the boom; just pinch it in, like in the photo, and we'll trim it off before the resin goes on. Simple!
Nov 29, 2009, 09:04 PM
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Mike Furcolow's Avatar
Now hit it with the heat gun. You'll be surprised how much it constricts. Work from the center of the plane towards either end, to push out any excess epoxy. Naturally, there is an area at the nose and at the rear boom where the shrink wrap will not constrict far enough. No worries. At the nose, cut off the shrink wrap even with the cable tie, and cut small Vs out with a hobby knife. Three or four should do it. Now take electrical tape and wrap the nose as tight as you can, to taper the nose as much as possible. Don't worry, we'll sand it smooth later.

At the rear, the larger shrink wrap will only constrict enough for halfway down the tail boom. Easy. Just take a scissors and cut off the excess above and below, leaving approximately enough of the strip on each side to neatly meet the other side. Once off, you'll have two parallel strips on either side. Once again, just use the electrical tape and wrap it up tight, down to and around the tail. The treated surface will give a smooth shine under the taping when cured.
Nov 29, 2009, 09:30 PM
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slopemeno's Avatar
Looks like a diamondback.
Nov 29, 2009, 09:42 PM
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Mike Furcolow's Avatar

Introducing; SuperSpeedo!


SuperSpeedo!
(sounds like a really REALLY tight swimsuit....)


All that's required for finishing is sanding out the nose and tail, fine sanding, some more fine sanding, and a final thin clear coat with the epoxy resin. In a crash, the nose will only get scratched, not cracked. A little fine sanding and an overcoat of clear coat makes it like new again!


This thing is unbelievably strong!!!
Nov 29, 2009, 09:44 PM
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flyzwell's Avatar
Nice instructions. Very thorough.

Good job.
Nov 29, 2009, 09:45 PM
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Mike Furcolow's Avatar
Quote:
Originally Posted by slopemeno
Looks like a diamondback.


Think I'll cover the wing w fluorescent green and call it the Geico Gecko....no worries, mate....
Nov 29, 2009, 10:47 PM
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Ward Hagaman's Avatar
Very nice!

Did you do any before/after weighing?
Nov 29, 2009, 11:00 PM
I DS slower than I build!
Cory's Avatar
Looks great! One question, though. It looks like the stock canopy fits on even though the extra layer is under it. Did you have to make any modifications there, or did it fit fine without modding anything?
Nov 30, 2009, 01:14 AM
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Mike Furcolow's Avatar
Quote:
Originally Posted by Cory
Looks great! One question, though. It looks like the stock canopy fits on even though the extra layer is under it. Did you have to make any modifications there, or did it fit fine without modding anything?

It just "spread out" just a little, and fits fine. I'll attach it with a pin in the front and magnets in the rear.
Nov 30, 2009, 01:16 AM
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Mike Furcolow's Avatar
Quote:
Originally Posted by Ward Hagaman

Did you do any before/after weighing?
Sorry, I didn't add that. The stock fuse empty weighed 2.0 oz; after complete armoring, the whole fuse and tail weighed in at 3.4 oz. And remember, a good percentage of that weight is behind the CG, so expect it to gain a little more when properly balanced out. I think of it as built-in ballast.

That's on my inaccurate postal scale, but the weights should be relative....

Speaking of ballast, the fuse is strong enough now to support an internal ballast system. I've got a good idea that will let it hold another 12 oz of lead inside the fuse under the wing. First I gotta see if it will slow down for landing, though.....
Last edited by Mike Furcolow; Nov 30, 2009 at 01:26 AM.


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