First post! Also got an RV6 kit and have a couple quetions.

Hello!

I recently purchased a partially completed RV-6 kit and am in the process of getting my head into it. I have at least one initial question that I could use a second opinion on. (Yes, I know I need to join the local EAA chapter. I'll be doing that in January)

This kit has had two previous owners. The second owner fabricated a new front deck skin out of 6061-T6 instead of the original 2024-T3. I'm not sure the reason for it at this point, other than it seems like the 2024 skin has a slightly narrower curve near the aft.

Here's my dilemma: When the 6061 skin was made, it was dimpled, and the framework underneath was also dimpled to match. The "original" 2024 skin was countersunk. I have a feeling I shouldn't rivet a countersunk skin to a dimpled framework, so I suspect this skin is no longer useable. I'm also a little concerned that 6061-T6 is the wrong alloy. It also looks out of place due to the different color.

Should I get a sheet of 2024-T3 and make yet another skin for this section, or just use the 6061-T6 piece?

My build log is here: https://eaabuilderslog.org/?blproject&proj=7rwLWCUmc
The entry that shows some photos of the piece in question is here: https://eaabuilderslog.org/?blprojentry&proj=7rwLWCUmc&e=7sSqr211X

Welcome!

Welcome Nathan!
I'm also building a -6A and I think that the forward deck skin (F-671) should be .032 2024-T3 exactly per the plans, rather than 6061. Also, if the ribs have been dimpled then the skins will need to be done the same way. Dimpling is stronger than machine countersinking anyway.
All the best with your project, there's lots of help and advice and opinions available here.

p.s. that skin will be easier to fit if you can take it to a sheet metal shop to get it rolled to the correct profile, since it is a bit too thick to do manually. You'll probably need to make a couple of firewall/bulkhead templates from plywood, tied together with spacers, to take to the sheet metal shop.

Cheers,
Paul.

The second skin was probably made out of 6061 because that’s what the builder had on hand, and needed to make a new one because the original had been improperly machine countersunk. So I guess you’ve already figured that part out, but I think you should call Vans tech support get get their opinion on it’s use. 6061 is a more workable alloy and is probably easier to make fit where the front boot cowl skin attaches to the longerons. But I don’t think it’s as strong as 2024. For a brief refresher on aluminum:

https://www.aircraftspruce.com/catalog/mepages/aluminfo.php

6061-T6 has lower allowables then 2024-T3 in general so the substitution would be questionable.
The easy way to duplicate the hole pattern, would be to carefully hammer the dimples on the 6061 sheet flat with a plastic or wood mallet and then use it for a pattern. You don’t want to hit the sheet so hard that you stretch the sheet.

I agree with Dan, using the 6061 drilled/dimpled sheet as a template to drill the new 2024 sheet should work. You could mate the upper surface of the 6061 sheet to the lower surface of the new 2024 sheet, keeping correct orientation, so the the dimples don’t interfere with match drilling. You might also be able to use the machine countersunk 2024 sheet for match drilling if the hole alignment is correct. However, a dimpled hole, and also a machine countersunk hole in .032 sheet will be slightly larger than the normal #40 hole than you are looking for, so care should be taken to make sure you are centering you drill bit while match drilling. Not sure how to accomplish that.

Thanks for the replies. You basically confirmed my suspicions. I really didn't want to remake that skin, but I guess I may have to.

I've got a set of transfer punches, I'll see if I can find one that centers nicely with the dimples facing up. If not, I'll just make something.

I have a feeling this is a no-go, but what about simply flattening the dimples in the framework using a rivet squeezer and flat dies? Presumably I could then use the 2024 sheet with the machine countersunk holes.

Schenkzoola said:

I have a feeling this is a no-go, but what about simply flattening the dimples in the framework using a rivet squeezer and flat dies? Presumably I could then use the 2024 sheet with the machine countersunk holes.

Click to expand...

Yuck. My suggestion would be strap/tape a new skin over the substructure, then backdrill the skin from inside the fuselage, clecoing the new holes as you go. I'd use a long drill to give you a better chance to get the drill perpendicular to the skin.

Start in the middle of the skin and work outwards from there...

I agree with the other posters to replace the skin with 2024T3. Please check your plans. I've built 2 -6's and it's been a while since I dealt with that skin but I believe it calls for dimpling on the ribs and bulkheads. The longerons are countersunk because of the side skin overlap but the upper cowl skin is dimpled to nest in the cs. There might have been an option to cs the cowl skin vs the longeron. That skin is highly stressed. If you hang the engine before that skin is riveted you can see the structure give even with it clecoed in place. Don't give up any strength you don't have to.