RE: 4*120 Build Thread
ALRIGHT!!
I'm back in the saddle. I got downstairs today and did a little work.
I decided to go ahead and cut out the stock firewall and move it back. Had to fab a new firewall.
The firewall needs to be 4.25" wide. Even though the fuse is only 4" wide inside--you need an extra 1/8" on each side to "key" it into the fuselage side doublers.
It is 5 and 3/8" tall (5 3/8" )
I didn't have enough hard ply to make a firewall out of 1/4" ply. So, I improvised. I made my firewall from 1/4" lite-ply and then doubled it up for a total thickness of 1/2".
I decided to build in some right thrust with this firewall. The factory firewall doesn't have any right thrust in it, and since I'm using a bigger engine--and I had to make a new firewall anyway--might as well build in some right thrust.
I measured back on the left side 1 and 1/2"--(1 1/2" )--and made a mark where the FRONT of the new firewall would set. Then I measured back on the right side and made a mark at 1 and 9/16"--(1 9/16" ). What this does is angle the firewall off too the right. So, I've created 1/16" offset in the distance of the firewall--4".
Now, I have my lines marked on the sides of the fuse where the front of the firewall will set. And my firewall is 1/2" thick. I just made another mark 1/2" behind the first marks. I've got my firewall layed out.
Now, I took a razor saw and cut through the fuselage side doublers untill I hit the fuselage sides. I needed to remove the doubler where the firewall would set. This allows the new firewall to be "keyed" into the fuselage sides. Just like the stock firewall. The doublers are 1/8" thick on each side. Thats why the firewall is 1/4" oversized for the spacing inside the fuse. By making the firewall 1/8" bigger on both sides and then cutting through the doublers--I've got my firewall locked into place between the fuse sides and it can't move forward because it's resting up against 1/8" of lite ply on both sides.
The pics will make this clear as day. I hope I'm explaing this clearly.
I've got some pics here of the glueing procedure. I've used a handfull of rubberbands to act as clamps. Also got a couple bar clamps on there as well.
The first pic is a shot looking from the front. If you look on both sides--you can see where the old firewall was cut out and then just sanded flat with the sides of the fuse.
The second pic is a shot from the back--inside the fuse. This just shows where the new firewall is sitting.
The third and fourth pics are just waiting for the glue to set. Notice how I've cut the fuse side doublers out to key the firewall in.
Pics: