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xblueh2o

Well Known Member
I had a rare full day out at the airport and made some nice progress today.
At the end of the day I had all the skin stiffeners riveted to the rudder skin and after I had cleaned up the workbenches I set up my bending brake in preparation of bending the rudder trailing edge. My brake is made from 2X4s with the "work" being done on the 2" surface. Just for grins I placed the skin in the brake and began to close the brake to check if everything was adjusted right and it just spit the rudder out of the brake. Out of curiosity I tired it lightly a few more times, same reaction. I was now running late for a dinner engagement so I didn't get a chance to tinker around with it more. I can't imagine I will have different results when I start applying pressure for real so my question is, did anybody else run into this issue and how did you resolve it?
 
BruceEicher said:
I made my brake from 2x8s, the larger surface must give more friction to hold the aluminum in place. I do recall having to hold (push) them in somewhat as I lowered the brake. Might want a helper as two hands pushing equal pressure down on these homemade brakes will give more uniform shaped trailing edges. Have your helper hold them in place.
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Same here. Even with 2x8s for the brake, I recall that the skin still wanted to slip out of place, so either figuring a way to clamp the skin down or having a helper to hold it in place is essential.
 
Second set of hands. Got it. That is sort of what I was thinking was going to be the case. I appreciate your input.
My brake is made from 2X6 (not sure why I wrote 4 in the OP) and I ran them through a planer so the two working edges are true and perfectly parallel to each other.
When the brake is closed you can't see the seam between the two pieces.
 
Look Ma, no hands

Just bump some boards against the leading edge of the stiffeners and clamp them to the table. This will eliminate any chance of the work moving during the bending process.
 
Just don't squeeze it too much. When flying in phase 1, you can sqeeze it some more, if the flight characteristics dictate, but it's hard to 'un-squeeze'.
 
xblueh2o said:
Second set of hands. Got it. That is sort of what I was thinking was going to be the case. I appreciate your input.
My brake is made from 2X6 (not sure why I wrote 4 in the OP) and I ran them through a planer so the two working edges are true and perfectly parallel to each other.
When the brake is closed you can't see the seam between the two pieces.
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But, an 1/8" gap helps accommodate the 1/8" dowel and 2 skin thicknesses and keeps from spitting it out.
 
Unsqueezing can be accomplished during flight testing by tapping the trailing edge with a hammer. Protect the trailing edge with a board. Tap gently along the trailing edge to get what you want.

Also, remember that paint doesn't like this, but it likes squeezing even less.
 
I clecoed my elevator and aileron skins to the bench. The top of my bench is flush with the frame on the end, allowing me to clamp the brake flush with the top. If my bench hadn't been so heavy, I would have moved it out so I could clamp the whole width of the skin to the top, but the method shown worked well for me. You might also try wide strips of duct tape to secure the skin to the bench. My build log shows my results.
FP03022013A00051.jpg
 
Securing bending brake and skins

I screwed my 2x8 bending brake down to the work bench from underneath the bench, and then used gorilla tape to semi-secure the edges of the skins to the bottom of the brake. I think I also used an additional 2x4 to give the rest of the bottom skin something to sit on that was level with the bottom of the brake. I di not use an 1/8 inch dowel - just ensured that the skins remained as flush up against the hinge line as I could keep it. I bent about half way and checked the position of the skin edge agains the3 hinge line, adn bent some more.

The skins still slid forward just a slight amount during the bend, but the tape pretty much did the job of keeping everything in line. The edges turned out fine.

Beef up your bending brake with some wider boards, and secure the bottom skin somehow (clamps/tape, etc.), and you should have no problems.
 
Exactly

longranger said:
I clecoed my elevator and aileron skins to the bench. The top of my bench is flush with the frame on the end, allowing me to clamp the brake flush with the top. If my bench hadn't been so heavy, I would have moved it out so I could clamp the whole width of the skin to the top, but the method shown worked well for me. You might also try wide strips of duct tape to secure the skin to the bench. My build log shows my results.
FP03022013A00051.jpg
Click to expand...

This is the exact way I did it and it worked great!!!
 
SHIPCHIEF said:
Just don't squeeze it too much. When flying in phase 1, you can sqeeze it some more, if the flight characteristics dictate, but it's hard to 'un-squeeze'.
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There is much more damage caused by under-bending than by over-bending.
If the trailing edge is not bent sufficiently, cracks will form around the stiffener rivets. This is VERY common.
 
Just to tie a nice bow on this thread, I saw Sam's finished work and it came out beautifully. Congratulations Sam!
 
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