SonexBuilders.net

Well.......here we go again boys and girls.

Just before I left for Sun-N-Fun, I riveted the ribs to the LH spar and test-fit the upper aft skin. Initally, everything looked very good. But upon closer inspection, I found the rivet holes closest to the spar, (from #6 rib through #12) were directly over a flute in the ribs. #1-#5 are specialty ribs with no flutes in that area.

Every Sonex/Waiex I examined at SNF showed no evidence of a similar issue. To drill down through the flute and install a rivet would seemingly cause a depression in the skin at those locations, not to mention a crappy joint. Everyone's was smooth.

Has anyone else run across this problem?

I picked up the wing kit (Legacy) last June when Sonex was offering discounts to clear the warehouse to make room for B-model components. As one of the last legacy kits before the Bs were offered, I would have thought I was going to be working with the "Pinnacle" of kit development. I've had MANY mis-matched holes during this build, but this one takes the cake.

Levi, at the Sonex booth, suggested I straighten the flutes. I checked with both ACS and Wick's and neither had a flute removal tool. The fluting pliers I purchased at the beginning of the build (the ones Sonex recommends) are not suitable for reshaping. I tried reshaping a couple of flutes on an extra rib and came up with an unacceptable result. Besides, how many times can you change the direction of a flute in 6061 T6 before it starts to crack? A shim was suggested, but it would need to have compound curves to match the flute. Not easy to do with a .040 shim, and likely to still leave evidence behind in the form of a distorted skin.

Anyone that knows magic, or has access to holy-water, please do contact me. The only "fix" I can see is drilling an extra rivet hole ahead of the flute for the skin attachment, and either leaving the holes in the skin as a conversation starter, or plugging them with AN rivets.

I am really.......really trying to remain positive, but the factory is not making it easy. Once again, I should be progressing, but am at a standstill till a solution presents itself.

The tunnel grows longer and darker by the minute here @Area 51%

If you bought the parts from sonex directly and they don't fit then they are defective. You should be asking Sonex to replace the parts. Straightening and moving flutes isn't something you should have to do after spending good money to buy premade ribs. If they think it is no big deal then let them take the ribs back, fix them and try to resell them to someone else. Yes, you could do it but why should you have to?

Keith
#554

I would straighten the flute in that area, keep making progress, and soon you will forget all about it. My turtle deck formers were way worse in this regard. You can stop your project with analysis paralysis or you can find the best solution you can and drive on.

There are several places throughout the Sonex kit where you'll find a hole over a flute (for me it was especially bad along the upper firewall, but I also ran into this a couple of times on the wing and tail). Its the nature of their ideal drawings & rivet spacing vs. the reality of flutes being placed where they're needed to achieve the proper final shape. Note that Sonex dimensions work fine if you're exactly on-spec; but most of us will wind up mis-aligning parts by a few thousands of an inch (or perhaps more than 1/32nd of an inch on occasion). That can have a ripple-effect that causes a rivet hole to fall over a flute.

Do not try to straighten the flute out with fluting pliers; as you experienced, it will not help. Wish we could have helped you avoid that - don't be afraid to post before trying an idea! To flatten a flute you need a tool with flat jaws - not something that applies point pressures. My personal favorite is to use a hand seamer, like these: http://aircraftproducts.wicksaircraft.c ... mer/tp44-0

First, use that tool to flatten the flute. Then use your fluting pliers just ahead or behind the hole area to put a new flute into the metal (to return the overall part to its proper shape). Don't worry about getting the original flute 100% flat, just get it close - as long as you don't overdrill the hole you'll be fine. Remember that the metal will deform slightly ahead and behind the fluting pliers, so space the new flute appropriately. Try on some scrap first to get a feel for it. Once you've done it a couple of times it will become routine and easy. OK, maybe a little annoying; but still easy. :-)

Hope this info helps!

--Noel
Sonex #1339

Hi all,
Good advice Noel, thats exactly what i was going to suggest. Hang in there randy, you'll need alot more gas at the end . I know sometimes can be fustrating. Keep plugging away. U'll find solutions to crazy stuff.

WaiexN143NM
Michael

I agree moving the flutes is probably an easy solution that won’t disrupt your project too much.
I’ve seen RV builders turn dimples inside-out after accidentally having stuffed it up initially, and tell me the factory told them it was OK to do so, so I would not worry too much about flattening a flute.

However, it is implied here that that if you had built exactly on specification this would problem would not have occurred. I would disagree with that, let me explain why:

My Sonex was not bought as a kit from Sonex LLC, it was partly built from scratch, partly made by a guy I can across here who owns a factory that makes BBQ’s & pizza ovens.
He had all the machines to laser cut, punch, form & fold exactly as per the plans so he made pretty much all the 0.025”, 0.032” and 0.125" parts.
(BTW, at the time he made this “kit” Sonex were still developing their own kit and they were just selling plans along with a few pre-made parts. I guess in that way he was even ahead of his time, unfortunately he lost interest in building and decided to buy a finished aircraft so he ended up selling everything he made, I bought everything :) ).

Anyway, he drew everything up in CAD exactly as per the plans and let his machines do the rest. This included the wings skins and ribs. They came out EXACTLY as per the plans, and I can tell you, no holes in the wing skins came even close to any of the flutes.
You would have had to miss-align things by half an inch or so for that to happen, not just a few thou. So based on my experience I would say that either the holes in your wing skin and/or the flutes in your ribs are not exactly as per the plans.
Do Sonex still distribute fully detailed plans with their kits like what scratch builders would have bought? If so, just check the position of the holes & flutes against the plans (if not contact me offline)

I built one of their kit wings and did not have this problem. There was some frustration with the firewall flutes and I think I do remember some tricky flutes on the tail (both already mentioned), but the wings had plenty of spacing from the flutes.

Are you absolutely sure you are installing the aft skin in the correct orientation? The holes are not the same distance from the edges, so I could imagine this happening if you accidentally have it backwards or maybe the bottom skin on top.

The plans show the location of the front flute being 1/4" different on the top and bottom of the aft rib, so be sure it isn't the rib that's upside-down.

My understanding of their process is it would be impossible for the flutes to be in the wrong position since they are formed with the rib--this only leaves the holes on the skins as a possible culprit unless they are using new forming dies (which I guess they must be for the specialty ribs you mention without flutes there?)

I suggest comparing the hole placement in your plans to what you see on the sheet you are using. I'd want to absolutely understand the cause of this issue before I continued, because it's possible you are somehow attaching the skin in the wrong orientation.

Looking at my drawings, should there even be a flute in the location you mention?

This is a scan I had in my laptop, I don't have my full size plans here with me but judging the dimensions it looks like the first flutes should start at about 90mm from the forward edge of the rib...

I remember my firewall flutes being bad in a few spots but not the wings. But, as they say, memory is the second thing to go.

I built from the kit, purchased in 2006 and had no skin holes near any flutes. I think it probable as said above that you are fitting the wrong skin or the wrong orientation. Easy to check grab the other skin and see how it fits. As far as the firewall flutes go, like other builders I had to re-work some of the upper flues. Not for the rivets but where the Southco fasteners needed to be. As previously suggested I used a pair of hand seeming pliers to flatten the existing flutes and used a smaller fluting pliers to make flutes on either side of the original flute location. You could use the big flute pliers but don't make the flutes as deep as there will be two flutes to shrink the metal.