Did you flute the top of your firewall flanges?

[David_Nelson]

Hi All,

I'm using camlocks and I'm working on attaching the top cowl attach strap. Long ago I fluted the firewall so that the top forward skin would fit along the firewall flange. But now the flutes are keeping the attach strap from sitting flush with the firewall flange. Was I not supposed to flute the firewall flange? If I was not supposed to flute the flanges, how am I supposed to fit the forward top skin?

Thanks,

 

[Vlad]

David I am doing the same - attaching strips and fitting the cowl. I do not remember I saw a fluted firewall flange while browsing hundreds of people's webpages. Try to unbend them otherwise you won't be able to get good fit for either strips or hinges. I understand you have already match-drilled to the skin. First unbend a little, check the fit with the skin, if OK proceed until all flanges are flat. Unbend while everything is clecoed. I think you were not suppose to flute the firewall, flanges would be sandwiched between strips and skin and all perimeter is stiffened with all those multiple angles and corner steel contraptions.
If you are unable to get hole matching, try thicker strip with grooves for flutes, or shorter strips to bypass the flutes... Or a combination of everything. It's just some thoughts, I am sure others will speak too.

 

[David_Nelson]

Having slept on this....

Hi Vlad,

I thought about unbending them, as you suggested, and I could probably get away with it along the top center. The flutes where the skin transitions from horizontal to vertical are not trivial. I'd guess about 1/8". If I were to unbend those and re-drill the top skin and firewall I'm concerned that I'll end up with a) a lot of oblong holes and possibly b) swiss cheese of the firewall.

Having slept on this, I'll try the "unbending" and see how far that takes me. For the bigger flutes, I'm thinking about cutting them out and dressing up the edges with a Dremel tool. If anybody has any other suggestions, I'd sure appreciate hearing them.

Thanks

 

[boom3]

In order to get a good top skin fit, I fluted mine too. At the time it seemed like the right thing to do and it wasn't till later that I thought about the cowl attachment. I've always planned on doing skybolts or equiv so I think it will be easy to work around the flutes with the skybolt attachement brackets. It seems like the attachment brackets are made of pretty thick material, can't you notch them for the flutes?

Hinges would be a different story.

 

[edbooth]

Having built three RV's... 6,7 and 10, I have never seen the need to flute the firewall flanges. The metal is so thin that if there is a slight bow, it is easily straightend when all clamped toether with the skin and hinge material or the metal strip for the skybolt fasteners for drilling the rivit holes. You probably can straighten the flutes if your careful. If the rivit holes are already drilled, I would cleco everything together and use your flush rivit set in the hand sqeezer to straighten the flutes. Good luck..

Ed Booth, Trenton, SC
Builder/flyer RV-6, 7, 10 (and now a 9A)

 

[Wicked Stick]

You probably can straighten the flutes if your careful. If the rivit holes are already drilled, I would cleco everything together and use your flush rivit set in the hand sqeezer to straighten the flutes. Good luck..

Ed Booth, Trenton, SC
Builder/flyer RV-6, 7, 10 (and now a 9A)

That is exactly what I did and it worked out fine.

 

[David_Nelson]

De-fluted...

I was just about to start and decided I better check the forums before I did - you know, just in case. Sure am glad I did! I put the top skin back on, cleco'd it within an inch of its life and flattened out one of the major flutes. That seemed to have worked so I did the rest with excellent results.

Thanks everybody!

/\/elson

 

[mikeasselin]

Firewall Fluting

I too fluted my firewall and am really glad I found this post. I was considering making up spacers but the cleco and flatten seem to be an easier solution.

 

[BSwayze]

I did it, too.

Like a big dummy, I fluted my firewall flanges, too. It just seemed like the right thing to do at the time. Especially after doing so much of it during the wing kit. I've been staring at those flutes for many months, wondering how I was ever going to get my piano hinges to lie flat on them for riveting. I'm using the traditional hinge method for my cowling.

But, there's GOOD NEWS! The other day, I took my pneumatic rivet squeezer and some flush rivet sets, clecoed every single hole, and flattened out those flutes one at a time. The holes were dimpled long ago before I final-assembled the firewall. The dimples and clecoes hold it all in place, so I don't see any elongated holes. The firewall is thin, and easily flattens out when you squeeze the flutes flat.

I am so relieved to have this problem solved! You look at my flanges now, and you'd never know they had flutes in them.

 

[Lemmingman]

I'm glad Mike revived this thread. I just took my firewall out of the shipping crate a few days ago. I should be getting to it this weekend, if I read the directions right. I wouldn't have thought twice about fluting it.