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Old Apr 19, 2009, 06:35 PM
High Planes Drifter
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Joined Oct 2006
81 Posts
Question
Convex hinge lines and hinge bending resistance

Folks -

I've constructed some balsa SGII tailfeathers with kevlar fabric hinges (under 0.75 oz bagged glass) on one side. Both the stab and rudder have some convexity to them along the long axis (tapered towards the tips). I have cut out the triangular hinge gap no problem, but note that there is some bending resistance as the movable surface reaches maximum travel (in both directions), due to the convexity of the hinge line. The resistance is not huge, but I'm wondering if it will make servos work harder than they have to.

Any fixes, or is this something I shouldn't worry about?

- Rogo
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Old Apr 19, 2009, 06:40 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
21,672 Posts
If you bag the parts out of the beds, and lay the hinged side flat on the work bench, it fixes the problem. It seems a little late now, but maybe cutting a few slits through the hinges at the apex of the bent part will help.....

Target
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Old Apr 19, 2009, 08:03 PM
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Poland, Śląskie, częstochowski
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Quote:
Originally Posted by Rogo
Folks -

I've constructed some balsa SGII tailfeathers with kevlar fabric hinges (under 0.75 oz bagged glass) on one side. Both the stab and rudder have some convexity to them along the long axis (tapered towards the tips). I have cut out the triangular hinge gap no problem, but note that there is some bending resistance as the movable surface reaches maximum travel (in both directions), due to the convexity of the hinge line. The resistance is not huge, but I'm wondering if it will make servos work harder than they have to.

Any fixes, or is this something I shouldn't worry about?

- Rogo
Soften hinge little more that should reduce problem
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Old Apr 19, 2009, 09:05 PM
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Canada .the great
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take a triangular file and drag it down the hinge line along the top and bottom of the fin where it makes a bend ,,file until you see fuzz from the kelvar BUT no more than that ..
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