Misc. While Waiting on FWF

My thumb twiddling continues.  I'm cautiously optimistic that Van's will get things shipped this week.  I have a lot of things left to do on the plane of course, but I don't really want to move everything around the shop only to have to move it back as soon as the firewall parts arrive.  So household chores it is!

I've decided I will do additional firewall insulation beyond what is in the kit.  The standard firewall is perfectly adequate, but there's a lot of evidence that shows insulating the firewall provides significantly more fire protection.  The bare firewall itself keeps actual fire from coming into the cockpit, but the heat transfer is pretty severe, meaning there's no way you'd be able to keep your feet near the pedals.  Adding just 1/8" of fiberfrax (covered with stainless steel foil), can keep the cockpit side of the firewall cool enough to make it a non-issue.

I made a poster board template of the firewall.  I'll use it to cut the fiberfrax and foil to size.  Once I figure out where everything goes on the firewall, I will temporarily mount it all, then remove it and transfer the hole locations to the template.  I think I'll probably have to buy some hole punches to punch holes in the foil and fiberfrax vs drilling.  The fiberfrax and foil will largely get held on with the stuff mounted on the firewall, but I'll use stainless sealed pop rivets in any areas that need it.  Anything that is structural on the firewall will be riveted/bolted/screwed on directly to the firewall and the insulation will be cut around it (like the engine mount pads).  Everything else that isn't structural, which is really just about everything, will get bolted on top of the insulation.  Fiberfrax is very dense and is fine to be sandwiched like this.  All perimeters will get a bead of 3M fire barrier caulk to not only seal it all up (mostly to minimize the chance of oil getting into the fiberfrax), but to also protect from the razor edges of stainless foil.  The foil I bought is actually stainless shim stock from McMaster - slightly cheaper than "foil" for some reason.  The widest it comes in is 24", so there will be seams where there is overlap.  The overlaps will be sealed with aluminum tape.  This seems counterintuitive, but the reason behind using aluminum tape and not stainless tape is that in the case of a fire, the aluminum tape will melt and open up the seam to allow the fiberfrax to off gas.

One small task I did check off today was dealing with the gaps present at the front of the canopy where the hinges insert.  The standard build just leaves about 1 1/2" of open space of the flange seal at the hinge blocks.  This is a common area of bad leaks and annoyance from what I've read.  This flange that is riveted to the sub panel will get a thin rubber bulb seal that the front edge of the canopy skin sets on top of.  Over that gap at the hinges it doesn't do much good though.  Most people don't seem to bother trying to fix the leak path.  Living in the PNW, there's no way I'm not at least attempting to improve it though.  The last thing I want is water pouring in on top of my very expensive instruments!

I decided to try to span the gap with material that the rubber seal can rest on, like the rest of the flange.  Doing the tiny step bend by hand was easier said than done, but after a few tries I got passable pieces.  I riveted them in place. There are still gaps, but those are small and will be filled with proseal when I'm ready to put the final top skin on.  It's not the prettiest solution, but I think it's as good as it can get for limiting leaks.  It'll mostly come down to how well that bulb seal works.  I didn't really need to make the pieces go forward over the hinge blocks like I did (the skin completely covers that area anyway), but it was simply easier to make.  I filed down the outside portion of the filler piece to make it thin enough that it'll go under the skin without causing any interference.

The other thing people often do is make or purchase a fabric cover for the subpanel area.  There is a company that sells them.  The idea is that even though most canopies will leak at those gaps, the fabric cover at least keeps the water from falling on instruments.  They attack velcro strips to the subpanel and the back of the panel, and the fabric just velcros in place just under the tip up frame.  I haven't decided if I'll go that route or not. I may wait to see how well my fix works.  I've been told the fabric is mostly useful when the canopy is opened on the ground after the plane has gotten soaked though - the canopy is big and that's a lot of water that runs off when it's opened.