Dent in turtledeck

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karmarepair

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I don't have access to my copy of AC43, so I thought I'd ask here.

Moving my Sonex was LARGELY successful, but a chain of error lead to a grapefruit sized dent in the top of the turtledeck, about a half inch deep. The stringer in that area is clearly involved.

I was thinking of how to pull or push it out, but then thought I should probably CUT it out and patch both the skin and the stringer.

No pictures yet, so just imagine what happened when the improvised door locks failed and the roll up door slammed on the fuselage. Advice wanted. Picture is of the plane in my shared hangar. The dent is between the antennas and the vertical stabilizer.
 

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Daleandee

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I would suggest an email to Sonex with detailed photos to get proper repair advice.

Edit: updated
 
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TFF

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See if there is good auto PDR person around. A friend had someone take out a huge dent in his aircraft. It was amazing. Some can do it better than others. Lots of new cars have aluminum panels so it’s doable.
 

karmarepair

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See if there is good auto PDR person around. A friend had someone take out a huge dent in his aircraft. It was amazing. Some can do it better than others. Lots of new cars have aluminum panels so it’s doable.
I've done a little bit of it (PDR) myself. The bending of the centerline structure I think precludes this.

The dent impacts BOTH turtledeck skins, they overlap at the top.

The U-Haul was too narrow to get the tail in, and the lock we improvised failed

From the initial builders log, you can see the centerline member. EAABuildersLog.org - Free aircraft builders log website.
 

rv7charlie

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If it's a factory prepunched kit like the RVs, then a new spine & top skins might be the most economical path forward, if you value your time at all. I've seen prepunched RVs with some truly impressive damage, repaired by simply replacing the bent stuff with prepunched replacement parts.

If it's scratch-built, the equation changes a bit. ;-)
 

karmarepair

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If it's a factory prepunched kit like the RVs, then a new spine & top skins might be the most economical path forward, if you value your time at all. I've seen prepunched RVs with some truly impressive damage, repaired by simply replacing the bent stuff with prepunched replacement parts.

If it's scratch-built, the equation changes a bit. ;-)
Kit was from 2000. <Frowning>
 

rv7charlie

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I guess that means not prepunched.

Still, if the structure below the top ailerons is straight, replacing the spine and drilling from inside isn't that terrible, if you or your assistant is under the old FAA standard human size. You should be able to do most of the drilling from outside, anyway. With two working, do it just as you would during initial construction. I haven't seen the Sonex build instructions, but typical technique for repairs would be to peel the skin up on one side, work your way down (or up) the other side reaching across the fuselage to drilling and clecoing through the existing holes in the bulkheads. Once one side is done, 'uncleco' from the side longeron up to within a few rivets of the spine, peel up the skin and start down the other side drilling/clecoing.
 

TFF

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You might be able to drill out the rivets and work the dent on each sheet separately. I have see portable “English Wheels” that you might be able to work with.
 

BBerson

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The removed skin can be laid flat and roughly hammered back to flat. Then lay the old skin on a new sheet and pilot drill new holes in the new skin. Bare skin can never go back with an English wheel. The wheeling stretches only and it is already stretched. Shrinking is virtually impossible. (source: English wheel expert forum at Osh)
I would be concerned with oversize holes after drilling rivets.
Skin dents can be repaired with bondo if the section was to be painted instead of bare.
 

D Hillberg

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1- cut out the bent stringer 2" beyond the dent drill out rivets to stringer
2- push up dented area with soft mallet head or it may pop out on its own.
3- replace stringer area cut lap splice joints

It's not certified - or put NACA duct in damaged area for cabin ventilation
 
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karmarepair

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1- cut out the bent stringer 2" beyond the dent drill out rivets to stringer
2- push up dented area with soft mallet head or it may pop out on its own.
3- replace stringer area cut lap splice joints

It's not certified - or put NACA duct in damaged area for cabin ventilation
The aft lower fuselage skin is not on yet, so I like this plan.
 

Angusnofangus

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Any idea how to do this without damaging the skins?
Slide a piece of stainless between the stringer and skin, ( a putty knife works well for this is you don't have any scrap stainless) and use a die grinder with a cut-off wheel to cut the stringer. Clean up the ends of the cut stringer and you are good to go.
 

karmarepair

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I pulled the plans out, since I'm isolating at home (breakthrough COVID) and can't get to the airport. The turtledeck skins overlap at the centerline, and the joint is backed up with this channel spine, one narrow side gets riveted to both skins at the overlap. I'll have to see whether both flanges of the spine are "tripped" out of plane, or if just the uppermost flange and the web.
SonexTDeckSpineChannel.jpg
I think my repair strategy is to cut out the damaged "spine" channel, use my brake to form a repair doubler that fits tightly in the flanges of the existing channel, and start riveting.

The question is whether to 1) work a Joggle in the upper flange to overlap the existing "spine" channel, or 2) just use a .025 shim between the new repair channel and the (gently persuaded back into shape) existing overlapping skins, and let the repair channel just nestle inside the existing channel, no joggle, the shim takes up the resulting gap. I may try and sketch what I'm on about later tonight...

Angusnofangus, your input in particular is eagerly sought!
 

Angusnofangus

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I pulled the plans out, since I'm isolating at home (breakthrough COVID) and can't get to the airport. The turtledeck skins overlap at the centerline, and the joint is backed up with this channel spine, one narrow side gets riveted to both skins at the overlap. I'll have to see whether both flanges of the spine are "tripped" out of plane, or if just the uppermost flange and the web.
View attachment 115033
I think my repair strategy is to cut out the damaged "spine" channel, use my brake to form a repair doubler that fits tightly in the flanges of the existing channel, and start riveting.

The question is whether to 1) work a Joggle in the upper flange to overlap the existing "spine" channel, or 2) just use a .025 shim between the new repair channel and the (gently persuaded back into shape) existing overlapping skins, and let the repair channel just nestle inside the existing channel, no joggle, the shim takes up the resulting gap. I may try and sketch what I'm on about later tonight...

Angusnofangus, your input in particular is eagerly sought!
Either way would be just fine, but shimming your repair channel is the easiest. I can't tell for sure by the drawing, but it looks like the standing flanges are not tall enough to put rivets in at the splice area. It looks like the channel is one inch wide, but again can't see for sure as it is fuzzy. You will need your repair piece to go four fasteners on each side of the cut. As this is the turtledeck I assume this channel isn't a structural part of the aircraft, turtledecks generally being just fairings. Hope that helps. If you have other questions, feel free to PM me.
 

karmarepair

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The channel is nearly 3 inches across the web, with the flanges 1/2 inch.

I'm also toying with the idea of buying a whole airplane's worth of channel from Sonex, it's only about $22, but shipping will probably be 3 times that. In that event, I'd cut the length I need, and butt it to the existing (on an angle? a sort of "scarf"?), with splice plates fore and aft on the web and flanges. OR drill all 72 rivets, and just replace the **** thing all the way from the canopy bow to the vertical stabilizer - maybe not though. It clips to all the intervening bulkheads....

Now that I'm home, I'll crack AC 43.13 AND the plans, but you've given me some ideas. Thanx!
 

Angusnofangus

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The channel is nearly 3 inches across the web, with the flanges 1/2 inch.

I'm also toying with the idea of buying a whole airplane's worth of channel from Sonex, it's only about $22, but shipping will probably be 3 times that. In that event, I'd cut the length I need, and butt it to the existing (on an angle? a sort of "scarf"?), with splice plates fore and aft on the web and flanges. OR drill all 72 rivets, and just replace the **** thing all the way from the canopy bow to the vertical stabilizer - maybe not though. It clips to all the intervening bulkheads....

Now that I'm home, I'll crack AC 43.13 AND the plans, but you've given me some ideas. Thanx!
This is also a viable fix. Put four rivets in the standing flanges, each side of the cut. As for cutting the channel on an angle, straight across is the way to go. Sounds like replacing the whole thing would be a bigger job than splicing in a repair piece.
 
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