Re: Musings on balsa vs. coroplast.

GallopingGhostler Tue Mar 07, 2023 8:00 pm

I've been wanting to get my hands on some corroplast, been told to seek out of circulation ads, campaign posters, etc. Seems in this small town though, hard to get and the blank stuff in stores is too expensive. Has merits though as natively fuel proof, so even though slightly heavier, can be trimmed in paint.

andrew Tue Mar 07, 2023 8:56 pm

batjac wrote:........I'm stalled at what is the best glue to use. Looking online, the recommended glues are things that glue the sheets surface to surface, but not really good for edge gluing, such as for the wing to fuselage joint of a profile CL plane. The best method seems to be premium hot glue at a very hot temperature which more or less 'welds' the coroplast according to the S.P.A.D. guys........

The Investor Mark

Some guys were using hot glues, some medium CA. The Gorilla Glue company does not recommend their Gorilla glue for polypropylene (coroplast). However, everybody flashed their joints with a propane torch before glueing regardless of adhesive and some sanded lightly after that.

You might want to look into Loctite Super Glue All Plastics. It seems to be specifically formulated for polyethylene, polypropylene and PTFE/Teflon.

batjac wrote:.....but not really good for edge gluing, such as for the wing to fuselage joint of a profile CL plane.

While it certainly would not be very pretty, you might try a test piece of coroplast cut part way through like you make hinges, then bent to a 90° angle and use it like a piece of metal angle iron, maybe with sides only a couple of flutes wide, on the bottom of the wing on either side of the fuselage. That would give you surface to surface joints for reinforcement.

batjac Tue Mar 07, 2023 10:23 pm

Andrew, I had thought of doing that. I was going to clean and flash the coroplast, then glue with thick CA, then use a sheet of coroplast on the joint like I would use a piece of triangle stock balsa on the joints. But that's a pain, and the glue would have to fill a large gap that I didn't want to deal with. The slot for the wing is just the flute cut out in the right position. Unfortunately, the flute is a little wide, and it's also not perfectly square, so there is a small gap where the wing and the stab slide through the fuselage. I will tack it in place with CA, then use the heavy duty glue stick to glue in the wing and fill the gap. I don't want to use too much reinforcement because that will add more weight, and one purpose of the experiment is to see how light I can build this.

The Sticky Mark

andrew Tue Mar 07, 2023 11:26 pm

batjac wrote:.......I will tack it in place with CA, then use the heavy duty glue stick to glue in the wing and fill the gap. I don't want to use too much reinforcement because that will add more weight, and one purpose of the experiment is to see how light I can build this.
The Sticky Mark

I think you've got a good plan.

The newer glue sticks are formulated so much better than the older sticks and a small fillet may very well be just the ticket. I just recently bought one of the higher capacity high temp glue guns and a pack of the better sticks, but have not used it yet. Your results may well be the nudge I need to put it to work.

a--

HalfaDave Wed Mar 08, 2023 5:48 pm

Hi Mark, (nice thread !) Cool

From my coro combat days, ( I flew against them with wood/foam)
The best glue for coro was medCA and kicker. (need the kicker for some reason)
-Gorilla PU and Goop worked good too.
-rubbing the surface with 120 grit, acetone wipe was the key, and the rub. (pun intended)
-1/16th bamboo skewers are your friend.
I think,
A 1/2A coro plane, has all the advantages of,
A balsa plane with many crashes/ repairs.
Coro is close. And needs,
Just as many props...
Take care,
Have fun,
Dave

batjac Wed Mar 08, 2023 10:23 pm

The glue sticks that I bought were the premium Arrow Slow Set sticks (here). At $1.21 per stick, they'd better be the best. I got the sticks recommended by a user on the S.P.A.D. forum on RCG. I messed up and didn't notice the glue gun I got was not dual temp. The reviews said it heats up pretty high and works great, so we'll see how a couple of test runs work.

The Spendthrift Mark

HalfaDave Thu Mar 09, 2023 5:13 am

Hi Mark,
All my coro info is 20yrs old...
I am familiar with Tig/Mig welding...
If you can weld coro together,
Is it called,
Pig welding? Smile

Take care,
Have fun,
Dave

roddie Thu Mar 09, 2023 9:40 am

HalfaDave wrote:
If you can weld coro together,
Is it called,
Pig welding?
Take care,
Have fun,
Dave

that's oinking funny!

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