repairing a crushed plywood firewall- Min-E-Breeze

[Frank v B]

This little 30" span model flew very well and was quite fast.  See first photo before the maiden.  https://temac.ca/smf/index.php?topic=8571.0

It fell out of the sky from 50' when lining up for a landing, hit the ground nose-on. About its 4th flight.
The only damage was
- a broken plywood firewall.  The prop was still in one piece!
- a broken former where the leading edge dowel fit into the fuselage.  Took 2 minutes to glue back in place.
- a stripped/broken wing hold-down tongue which I tapped for the wing bolt.

Approach to fixing the firewall since it could not be replaced.
- glue all the firewall pieces together on the exterior so it would hold together. Photo 95.  Photo 96 is after the front was smothered by 5 minute epoxy.
- glue fibreglass cloth (2-3 layers) to the front on the outside.
- drill out the vent holes and mounting holes through the fibreglass.  Essentially the old plywood firewall is used as a template for the holes.
- flatten the plywood on the inside and re-install the motor.  See photo 98 of the inside of the firewall.  It is not flat...yet!



Frank

[Frank v B]

Firewall re-build

- with a Dremel tool I smoothed out the outside of the firewall.  Got rid of the bumps (plywood, epoxy, etc.)
- covered the entire front face with 5 minute epoxy
- dropped in a piece of 1/2oz fibreglass cloth and squeezed it into the corners with a small brush
- repeat 2 more times- epoxy, cloth, epoxy, cloth. Photo 11
- pushed on a piece of waxed paper with corners cut.  Photo 12.  Pushed it onto the cloth/epoxy mix and worked it into the corners. Photo 13.

Will leave the waxed paper on it until it cures overnight.

Glued a new plywood wing hold-down tongue to replace the broken one. Photo 22.  The new one will be tapped and then shaped with a Dremel sanding drum.

Frank

[Frank v B]

Final touches:

- drilled out the two mounting holes and the 4 vent holes (this is an inrunner)
- installed the motor with the 2 mounting screws. (matching ones would have cost extra )
- painted the firewall red with high quality Dollarama finger paint.   

Prop goes on next.

Frank

[Frank v B]

How to get fibreglass cloth inside and around a corner.

Wanted to reinforce the repaired former where the leading edge dowel inserts.  It was around the corner and inside.

step 1- take a piece of waxed paper and smear some 5 minute epoxy on it the size of the cloth.  I used my finger to smear it on.
step 2- place the cloth on top of the 5 minute epoxy
step 3- smear some more epoxy on top of the cloth.  It will be soaked through immediately. Photo 23
step 4- place everything in the area it is needed and push the cloth around all corners.  Let cure. Photo 24
step 5- remove the waxed paper when the glue has cured and trim the excess with a knife.

F.