I am installing an engine that requires a 3/8 in firewall. The firewall installed is only 1/4. What is the best way to increase it to at least 3/8? I do not want to add to the outside if it can be avoided and on the inside I will need to cut the size down to get it to fit between other fuselage structures. Also on the inside of the firewall it is not very smooth and I will have to do some sanding in hard to reach area's. Can I add fiber glass to the inside this would be easy if the fiberglass is strong enough to reach the same strength as a 3/8 firewall. Thanks for any advice.

What plane/engine/mount are you working with?

I stick with 1/4 inch all the way up to 1.40s without problems. I use 3/8 with a 40cc gas engine. What plane and engine are you using? The 1.40s I use are both gas and the YS four stroke.

It is a SIG cap 231 installing a DLE 30.

The 1/4 inch is fine, just use some angle stock to reinforce it to the fuse, ARFs tend to just glue in the fire wall without a lot holding the fire wall to the fuse. You stand a better chance of having the fire wall pull out then the fire wall breaking.

Well said, I wouldn't change it either, just use some good triangle stock and give it more grab to the fuse sides.

Pinning the fire wall and fuse the the corner stock wouldnt hurt.

Cool Thanks guys!

Yeah, Scooter didn't elaborate on it, but if you drill some 1/16 holes through the fuse into the firewall, cut some 1/16 wire or threaded stock, slap some epoxy on the wire and slip into the holes. Cover with your favorite covering and nobody will ever know they are there. Also like GrayBeard says, if you put some triangle stock behind the firewall with the pins, you can put a Chevy 350 on the front of this thing if you want to and it ain't coming off.