Not wanting a re-hash of the previous crash post. I am in the re-build stage after my little mishap with my WH Yak. I have made a replacement plate for the landing geard mount and I will easily be able to re-sheet the parts that were affected but now I am considering what to do about the firewall.

The firewall pushed in a bit on the lower right hand side (looking at the plane from the front). The right corner pushed in enough that the wood broke out. (I still have the piece) I would estimate that 80% of the firewall is in tact. Should I put a doubler in from behind and then glue back in the pieces. I would also re-inforce the bottom with a 1/2 X 1/2 piece of hardwood glued inside the box. Or...is it better to cut out the whole front plate and replace it? This seems like a big job and I do not have a scroll saw or nice jigsaw to cut out new custom pieces. My main concern is the area I am referring to is right around the motor stand-off hole. I considered a doubler on the front but I have a DA50 on the plane and I do not want to move the weight any further forward if I do not have to.

Any suggestions on this repair?

Thanks,

Jeff

If you could post a couple of pics of inside and outside the firewall I and others could obtain a much better idea of what would be the best method of repair. Is that possible?

Good idea. Here are a few pics. Sorry they are not of better quality.

-Jeff

Thanks!!

What I can see would have me make a 1/8" ply doubler that would cover 1/2 the inside of the firewall, top to bottom, right to left, from right side to left looking at it from the front. After that was epoxied in place I would use another piece of 1/8" lite ply to fill the void at the front of the firewall to provide a level mount for the stand offs. The whole job shouldn't take much more than a couple of hours at a cost of $10.00 or less.

The reason for the 1/2 inside is to spread the good stuff over the existing part of the firewall that remains, balancing the load a little. More secure in the long run for the engine mount. Unfortunately there is no way that a repair will ever come out lighter than the original unless you started with wood and went with composites later. Not practical in this case. The end result will likely end up about 1-1/2 ounces added to the nose. Moving a battery or choke servo will easily offset that.

Good luck,
Pat

Thanks a lot. It shouldn't be too difficult. Can't wait to get back in the air.

-Jeff

Jeff, you are right around the corner from Tom! You ought to take your plane by his place and see if he can offer any better suggestion than silver surfer did.

Bobby

Bobby,

Thanks. It is nice to only be 3 miles from Tom's house. I might do that. I hate to bother him, but he was really nice when I picked up the plane.

-Jeff

I'm sure Tom wouldn't consider it being bother at all. Historically, he's been very helpful with me.
Shaun

Hope you don't mind. I took the liberty to lighten you pictures up a tad.

I still suggest adding a piece of 1/8 lite ply to the back side of the firewall. Full width and 1/2 of the overall height. The only item I would change would be to fill the front depression with fiberglass or C/F weave to match the rest of the face.

Lighter made the damage a lot easier to see.

10-4 Jeff. Have I met you at an IMAC contest somewhere? I can generally remember a face and an airplane associated with that face but you know there are so many Wild Hares out there it's difficult to remember them all!!

Bobby

Here's my suggestion.

Square up the firewall so it's exactly where it started. Make a new firewall that matches the original exactly, you can fit it in back to get the right size.

Epoxy 2 1/4" square strips of some hardwood like bass in the corners behind the original firewall. Then epoxy the new one behind the strips, using the strips to maintain the original angle so now you have two identical firewalls 1/4" apart.

Cut off the front one.

Voila. A brand new firewall spaced 1/2" back.

Mount the engine with your origional standoffs.

Now cut off the back edge of the cowl to shorten it and redrill the mounting holes so it's about 1/4" behind the prop.

This shortens the fuse by 1/2" which eases the node heavy condition and give you a shiny new firewall.

TF

The only thing I would do to add to Tom's method is drill and pin the new firewall. Maybe add another couple pieces of 1/4" stock to the back side.
If you don't want to cut your cowl you can also ADD spacers to the front of the firewall.

Just trying to add some more ideas and thoughts.

Thanks everyone. This is really good input. I will get on this sometime in the next week.

-Jeff

Tom,

I agree with you that a completely new firewall would be the best way. I'm not to certain of how much work the owner wants to expend, though. If he had a good working knowledge of composites and fiberglass components and applications there are other ways to do the job but they come out pretty expensive.

Pat