Building Aero 3D Day 27: Firewall

Monday, Peter & John came over and we shifted focus to the fuselage, specifically getting the firewall situated. I obtained a user Saito FA-100 for my engine and it came with a metal mount.

Based on the diagrams provided the engine needs to be side mounted with the muffler down, this means the head of the engine is going to protude out past the left side (looking at the pictures below). I haven’t decided if I’m going to build the cowel or not out of balsa block. As nice as that’d potentially look it may cause more grief than not for making engine adjustments and getting in flying time at the field.

I had previously marked the center of the firewall and the lines have since been extended to the ends (seen in the right pic below). John did a fair bit of figuring for how best to mount the engine.

Since the center (balancing purposes?) line goes right down the ‘prop mount’ under the mounting plates we rotated the engine mount 90° coutner-clockwise and shifted towards the right. With the engine in this orientation the muffler will be coming out from the bottom and will need to use a longer muffler manifold to clear the bottom and/or side of the plane (stay tuned).

Once that was all figured out and the hole locations marked I used the drill press to drill four 7/32” holes for the T-nuts.

Next, we double checked the fitting of the firewall into the front of the fuselage and mixed up a batch of epoxy. I applied the glue along both sides of the firewall as well as on the slots at the end of the FUBs I then fitted the firewall in place, FUB ends into the bottom slots of the firewall, and notches on the firewall into the sides of the fuselage and clamped into place. Scrap balsa sheeting with used to protect the fuse from the clamps, used to hold everything in place while drying.

Excess epoxy was brushed on the front and back of the firewall. This acts as a sealent to prevent fuel from seaping into the wood negatively affecting its integrity.

Eventually the tank is going to sit into the compartment between the firewall and FU3. If I was thinking would have filled the drilled holes with vaseline prior to applying the extra epoxy, so will need to drill out the holes a bit to allow things to fit.

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