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  #1  
Old 05-19-2020, 09:41 PM
MIKE JG MIKE JG is offline
 
Join Date: Sep 2016
Location: NE Ohio
Posts: 147
Default Rudder Bend, Need More Bend

Looking for advice on how to get more bend out of my brake. The rudder is nearly there but I just can’t seem to get the final pinch to get it to lay in the proper position on the spar.

With the rudder in the brake and just the weight of the board, the rudder is perfect but as soon as the brake is taken off it springs back to about 2” of gap too much.







I started with 2 2x8” boards as Vans suggests. That didn’t seems to give me the results I needed so I switched to 2 2x4”’s made out of cedar, hinged on the 4” side so I was only using the small sides to do the squeezing. That didn’t seems to help so I tried this final setup witch is a 2x4” along with a 2x8”.

Using the brake I can push the rudder all the way down until the stiffeners are touching the opposite skin, so I can’t physically bend it any more than that. But it doesn’t remain there after the brake is taken away.

I got to thinking could the vinyl backing be causing it to not bend all the way??

I would appreciate any advice.
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Last edited by MIKE JG : 05-20-2020 at 08:07 AM.
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  #2  
Old 05-19-2020, 10:17 PM
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PaulvS PaulvS is offline
 
Join Date: Aug 2019
Location: Western Australia
Posts: 782
Default hinge orientation

Apologies I'm not 100% sure from the photos but it looks like the hinges may be oriented in a way that is limiting movement. If the hinge pin faces out rather than in, as it does on a house door, then that should work better. It's a bit difficult to describe without pictures but if you lay the two 2x8s flat together and then put the hinges on the 2 inch edges with the pin barrels facing out you will get a tighter bend.
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  #3  
Old 05-19-2020, 11:00 PM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 923
Default

Exactly the problem.. you have the hinges on wrong. Place the hinges on the outside and be careful, the brake is very powerful!
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  #4  
Old 05-20-2020, 07:49 AM
MIKE JG MIKE JG is offline
 
Join Date: Sep 2016
Location: NE Ohio
Posts: 147
Default

Thanks for the quick replies but unless I'm misunderstanding (and that's always possible!) that's exactly the way I have it set up, hinges on the outside, 2" edge with the hinge pins facing away. As it is set up, the boards are able to sit perfectly flat on one another with the hinges installed.


Maybe I need different hinges, these are standard door hinges where the pin lays sort of down the middle of the actual hinge plates???



Here's a closer image of the setup:
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Last edited by MIKE JG : 05-20-2020 at 08:00 AM.
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  #5  
Old 05-20-2020, 08:40 AM
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PaulvS PaulvS is offline
 
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Location: Western Australia
Posts: 782
Default Pictures

Hi Mike,
In post #4 the first image looks right the way you have it, assuming both boards are 8 inches wide and face to face, as the lower board is not clearly visible.

The second picture in this post looks different though and it appears as if the hinge pin is on the inside of the boards and inside of the vee.

Can you maybe post a picture taken directly end-on and with the skin in place?

It should look something like this:



I used this bending method on rudder and elevators (RV 6) and it worked fine.

Other things I can think of to check, assuming the hinges and boards are good:
Stiffeners have been adequately tapered at trailing edge ends so they don't contact the skin, or each other.
Stiffeners are tight against skin and rivets are not clinched.
Skin is fully inserted right to the back edge of the boards when doing the bend.
If skin is clecoed to spar is the surface perhaps already straight enough? If there is any bowing out at the trailing edge... then it needs to be bent more.

As a last resort, a padded hand seamer could be used to very very carefully bend the trailing edge, this is risky because it is very easy to cause unintended damage and cause a crease.
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Last edited by PaulvS : 05-20-2020 at 09:13 AM. Reason: Inserted sketch
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  #6  
Old 05-20-2020, 09:35 AM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
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Default Brake

Rotate each hinge 180°. The edges of the boards will be the contact area. A bit more difficult to orient but far more power. So much you should be very careful.
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Last edited by wirejock : 05-20-2020 at 09:37 AM.
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  #7  
Old 05-20-2020, 09:49 AM
PhatRV PhatRV is offline
 
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Location: Buena Park, California
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Default

Before you try to rebend it, cleco the rudder spar and rib and see if the rudder skin is still straight and the trailing edge still has the correct curvature. Aluminun sheet is supposed to be flexible and the slight springback is normal. Don't over bend it because it is very hard to undo. Your picture shows the rudder bend is normal
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Last edited by PhatRV : 05-20-2020 at 09:50 AM. Reason: add more comment.
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  #8  
Old 05-20-2020, 09:55 AM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
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Looks like you are bottoming out on the stiffness, don?t force the bend further at this point. Continue with the frame assy with hole preparation and skin dimpling for spar & rib holes first. If bend is too tight you won?t be able to gracefully get in to dimple the rear most holes.
You can assemble & rivet the whole structure with the slightly under bent trailing edge, finish off the bend as the last step. Perfect tool for this is the vicgrip seamer sold by Cleaveland tool as it can be adjusted for a very gradual tighter gap. For final bend tightening - GRADUALLY move along the trailing edge bending moving along in 1? steps. GRADUALLY tighten the bend to radius required. I fold a hand towel to at least 3 layers & lay that inside & between the seamer jaws and rudder bend to prevent the edges of the jaws leaving ugly ?nibble marks? the whole trailing edge.
This vicegrip seamer method will come in real handy later when dealing with aileron trailing edges and adjusting for heavy wing conditions.
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  #9  
Old 05-20-2020, 09:59 AM
David Paule David Paule is offline
 
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Location: Boulder, CO
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Default

If you need to, you can unbend it slightly by forcing a metal rod the right diameter down into it, and carefully pressing on the rod with the trailing edge on a flat surface, spar end up.

You can also get more bend by moving the trailing edge almost to the long edge of the boards, yes, away from the hinge, and carefully using a c-clamp. Use a measurement at the spar side of the rudder to gauge how far you're going and take it in small increments.

For both of these, be very careful and don't go too far at once. Distribute your load and the pressure you apply or you'll get an uneven edge. You can work it out, with time, but it's a pain. Do this gently, and again, carefully.

Dave
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  #10  
Old 05-20-2020, 11:17 AM
MIKE JG MIKE JG is offline
 
Join Date: Sep 2016
Location: NE Ohio
Posts: 147
Default

Thank you all for the advice. I have a few things to try based on the advice here. I will report back. Def won't try to bend it too far at this point.
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