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elevator trim tab cutout bends

Tom Martin

Well Known Member
The left elevator skins have a close out tab that needs to be bent, one down the other up, to form a lapped joint. The plans call for the use of a piece of wood sandwiching the skin to a work bench. Then using another piece of wood to bend it down. I am sure this works but I present a simple alternative that is accurate and repeatable. I made a simple "brake" using some scrap angle.

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I cut the short angle the same length as the tab to be bent. The "bed" angle, the angle that the tab bends around has the sharp edge filed off to give a nice radius. On the picture you can see how the bed angle has a round radius. I left the plastic on to limit any marking of the material during the process. Mark both sheets with a line as documented in the plans. Put a line on top and bottom of both sheets and then lay the sheets together to varify that the lines are in the exact same locations. Mark on the sheets which tab bends bends up. On the first sheet, the one with the predrilled hole, clamp the " bed" angle so that the line is just visible.The top and bottom fixed angles are clamped to the line with the bed angle back just enough to take into account the thickness of the material to be bend. Then simply bend the tab to 90 degrees. Hand pressure was all that is needed. Of course you should practise on some scraps before trying the real bend!
For the bend on the next sheet simple move the bed angle back 1/32" from the line and make the bend. This allows for the overlap of the tabs. 1/32" is real close to .032 and I just used a scrap of material between the line and the bed to get the proper distance. The result is a perfect lap joint
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Tom,

That is a nice little brake.

I must confess however that having built my Sonex with only the 'hit it with a hammer on the edge of a table method' that is how I did these bends. Practice on all the Sonex little bends led to a very nice job for me.

For people with less confidence in my method yours looks nice and simple.
 
Elevator Trim Tabs

Hey Tom,

Wish you would have posted that last Friday. Saturday I bent the tabs and today called Van's to ask if I needed to replace the skins. The bend went too far back into the skin and it adds stress to the skin by the relief areas. The suggestion from Van's was, it's no big deal, just use a small file and take the stress out of the area. Hope that works, although it won't look nearly as nice as yours. Still can't figure out how to get smaller pictures posted here. I'm using TinyPic to upload them like they suggest.
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Maybe it sounds like whining, but I really wish Vans would get rid of bending tabs altogether and supply small end ribs....

Even if they cost $15 or more each, I'd be money ahead in all the screwed up trim tab skins I've had to reorder while building my 7A and 10.
 
.....or you could just make your own little end rib out of aluminum (.016), blue foam and glass cloth(easiest), or balsa wood - covered with a layer of glass (second easiest). I've done the aluminum one and the foam/glass, and both have held up for a long time. No cracks or other issues. If you're picky about minutia, the glass method (either one) looks a little better - no lines or breaks in the paint as if it's a solid piece. Total time fabricating this part (not the aluminum one) is no more than 20 minutes - including sanding after epoxy cure. Works fine - lasts a long time....
 
Stoney
I had a look at the pictures you posted. As others have suggested you could just make a rib to replace these tabs. Before doing that I might suggest a possible save.
Take a piece of angle and firmly clamp it to your back riveting plate. Place your skin on the back riveting plate with the tab up against this angle. Now take another piece of angle and place it on the sheet up against the tab. Make sure to round off and smooth the sharp corner of the angle. This will leave you with a sandwich, two angles with your tab between them.
Take a piece of hard wood, brick chisel, etc and place it on the inside of the angle.
This is the fun part, take a hammer and firmly strike the inside of the angle. This has the effect of pushing the two angles, and your tab together. Have a look and see if the tab angle has a better shape, if not whack it again.
You might just be able to save this tab. If not then make a rib and move on.
 
Tom,

I made the mini-brake as you suggested ($9 for parts...) and it worked perfectly.

Thanks for posting helpful suggestions,

Dennis
 
Van's method worked fine

I just did this step today using the wooden block method and it came out fine - 30 mins all in. Would have loved a better system but not sure how much time I would invest in making it work.
 
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