Firewall
 

Hi everyone.
What does everyone use to make the firewall on their 2 meter glow powered F3A birds? I have to make one for a wooden fused plane and was thinking of making it from a liteply fiberglass sandwitch. Would this be strong enough for a YS 140 on a gator mount?
I might also do this for a composite bird that I have here that will have a 3 Mintor 170 engine think.

Cheers.

RE: Firewall
 

Yes that would be enough...for a while. It wouldn't last forever though.

Carbon/lite ply/carbon/lite ply/carbon would definitely work, but the spaces where the mounting holes go through would have to be plugged with something harder than lite ply or it would tear out around the screws.

Of course, there's only 1000 ways to do it, that's just one....

-Mike

RE: Firewall
 

http://img301.imageshack.us/img301/8...arsmall4tg.jpg

This is the firewall on my Abbra---2layers of 3mm liteply with the outer layers' grain bonded at 90 degrees to each other, and 200 gram glasscloth bonded under pressure to the outsides. The captive nuts are held on exta little circles of liteply to avoid their tangs piercing the glass skin.
These sort of firewalls last indefinitely in my experience, used on20-30 cc 2 strokes soft mounted.
I have no experience of 4 strokes.
I have used carbon/end grain balsa laminates in the past---both sorts give a good wide (5mm plus) attachment thickness, but the glass/ply ones are equally light, and much cheaper to make.

PS the cut edges on the holes were fuel-proofed later!

RE: Firewall
 

That's pretty much what I was thinking, except carbon instead of glass. But glass works too, and it's a LOT cheaper to make!

Good pic.

-Mike

RE: Firewall
 

Sounds good, except the adding pressure part. I don't have a vacuum pump or anything, so what do you use to apply pressure to the outer layers of fiberglass?

Thanks for the pic.

RE: Firewall
 

Very basic,but effective...
Take two sheets of 12"x12" liteply, coat one surface with 24-hr wing skinning epoxy.
Lay them against each other with their grain layers at 90 degrees to each other.
Coat one outer surface with epoxy, and lay on a layer of 200 gram glass cloth. Stipple the glue through the cloth with a stiif old 1" paint brush.
Lay this face down on a square of melamine faced chipboard, or similar, with a layer of thin black polypropylene as the separator (I use part of a new rubbish bin bag--really!)
Repeat on the other side(which will now be on top)
Clamp around the margins of the two outer boards with as many G-clamps as you can, or weight them down on a strong bench with as much weight as you can(2or3 old car batterries works OK)
Excess epoxy wiil squeeze out of the sides of the sandwich -just make sure it doesn't go on the carpet, or anywhere else to get you into trouble with the civilized members of the family!
Leave somewhere warm for at least 48 hours, and then it's done.