Ch. 4 - Firewall - Part 3

Front side  (4.7 hrs)

I decided to modify slightly the way the screws are secured onto the firewall. 

The plans call for drilling the holes, countersinking them, then use epoxy on the screws to try to tie them to the fiberglass to go over them. The problem is that you could possibly tighten the bolts enough to break this weak bond. Should this occur, the screws would rotate loosely in the countersunk holes, and there’d be no correcting it, since the head of the screws are butted against the back of the spar, never to be seen again.

My buddy Wade suggested I grind the sides of the screws, and dig matching slots in the firewall, rather than countersinking. This is quite a lot more detail work, but well worth it, since it provides a mechanical impediment to the screws rotation. I added flox to the slots, and to the heads of the screws. I don’t think these babies will be turning on me anytime soon.

Screws before and after

Milling tool and slot outline

Screw slot ready

Dry fitting

Firewall back side

Wider shot of both screw sets

Adding flox

I then took some time to drill, and fit the mounts for the rudders pulleys. These are made out of steel, and they come from the “Cozy Girls” in two parts that need to be matched correctly, so that the pulley axle holes line up.

Rudder pulley bracket getting fitted

With those out of the way, I cut a ply of BID, and glassed the front of the firewall.

Using plastic to help squeegee the single ply of BID

Peel-ply sheet over fiberglass

Here’s a detail of the screws under the curing fiberglass:

Screws buried into the wood, floxed, and glassed.