Fitting a Firewall

So we have finally far enough to try fitting the firewall to the front.  I had already clecoed the firewall together (not shown), so fitting it up is pretty straight forward.

I began by clamping the firewall in place with wood blocks an C-clamps.  It took a lot of adjusting to get it straight.

Here is the firewall clecoed in position.  If I wasn’t working in a crowded shop, I would probably have to make airplane noises at this point!

Here is a closer view of the c-clamps with the wood blocks – no clecos yet.

Now we have clecos!  Note the board across the frame.  This was used to ensure the fuselage is straight, because I still am missing some bracing in the front of the nose, and the whole thing can be twisted pretty easily.

Anyhow, this is a boat makers trick.  I used the board on the front of the fuselage, and clocked it against the horizontal stabilizer (on a boat, you use two boards) to ensure there is no twist.  Note the prop blocks under the right corner, which were used to ensure very near alignment.  Call it a very primitive jig.   At this point, I have managed to push all the existing holes on the motor mounts into the firewall and re-usable framing and clecoed them in place.

Here you can see the angle brace on the left, and it is already drilled – as it is being re-used.  On the far side, I am more or less duplicating the pattern, using a rivet fan.  The fan won’t fit into the space in the normal manner, as the structure would get in the way – but it isn’t a problem.  I’m just skipping every other rivet spot on the fan, and that makes it all fit.

Here’s one of the new undrilled weldaments.  At this point, it is pretty well set all except on the bottom.  That will come after I remover the firewall.

Speaking of Wedaments, lets re-visit the ones that I need to replace on the top.

Here is the damaged one removed, and you can see the weld starting to crack.  I’m definitely happy to be replacing this.  All of the holes on this one have been duplicated in the structure and firewall, so it is pretty easy to fit the new one in its place.

And here is the new one next to the old one.  Note how much more heavy duty the new one is.  Its made of three pieces instead of two, and the plate is about doubly thick by comparison.

New motor mount going in.  I used C-clamps to pull it tightly into the corner of the longeron.  Then on to drilling and riveting to the longeron, followed up with drilling and clecoing to the firewall.  At this point, I am starting to run low on clecos.

Holes pushed through the firewall and structure.  Other side is similar.

While I’m at it, lets get that left front skin done.  This is pretty easy, as the old one straightens well enough to make a good template.  All the good quality holes can be drilled in to the new skin, and any that is wallered out will be drilled into the skin from the inside after the skin is clecoed onto the aircraft.

Cutting on the lines around the edges of the skin.  I actually snapped this picture to illustrate why I like offset snips – note that I can cut in a straight line without slicing my hand on the freshly cut edges.  Also, look closely at this photo, as you can see that I can only count to 4 on this hand.

Here is the unadjusted skin, clecoed onto the front.  I’ll play with it a bit to get it to fit smoother.  Note that there are no holes on the front where this would rivet to the firewall.  There is no reason to match any rivets where the other parts don’t fit against pre-drilled parts.  I’ll drill both sides of this seam at the same time.

Also – a brief rant.  Note that half of the plastic is missing on the side.  Wicks aircraft sold me this skin, and I didn’t notice it was missing almost half the plastic on one side until I got it home.  Bleh!

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