DIY dihedral jig

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Dihedral Jig pic.jpg

Hi All, just thought I'd pass along this handy DIY dihedral jig idea so you can fabricate one of your own
for glider builds. It's a fast easy project that shouldn't take you much more than a half hour and only
requires a ruler and hobby knife.

It's not my design, Brad from the Nighthawk Gliders channel on youtube made one for himself for his
balsa chuck glider builds. I built mine from 1/4" balsa sticks glued together but you can use whatever
you have handy.

I just followed his dimensions: 3" tall in the center, and on one side the lowest step is 1/2" tall, and
each step goes up in 1/4" increments. On the other side the 1st step is 3/8" and each additional step
increases by 1/4". That gives a nice range from 1/2" to 3". So much easier than trying to find stuff to
stack to get the dihedral angle correct when sanding or gluing wing roots.

Below is a pic of all the dimensions to make it even easier to get started. After I finished mine I
realized that I could have glued one side on at a right angle so that the jig is self standing. You might
want to do that as well or change the step increments to suit your needs. Happy flying!

Dihedral Jig dimesions and layout.jpg
 
Very cool. I guess you have to make two, one for each side.
If I do this, I might use 3 or 4 color markers to color each stick, so particularly in the mid levels it will be easier to see which level you are at.
Also I guess if I make two, with your "right angles" idea (excellent!), I might make one "left handed" (aka sinister) and one "right handed" (aka dextro.)
 
OK, I'll be the one to ask: how do you actually use the jig? I'm trying to picture it and failing.

I was guessing you put one on each side, and you can use the steps to determine how high you lift each wing tip. But maybe I'm wrong.
 
Typically you place one wing on a flat surface with a weight on it, and then lift the other wingtip to the proper height. The steps allow for the use of one jig for a variety of plans with various dihedrals.

I was guessing you put one on each side, and you can use the steps to determine how high you lift each wing tip. But maybe I'm wrong.
 
During my R/C days, you would set one wing panel flat on the work table and pin it down. Then, you would lift the opposite wing tip to the proper height stated in the instructions with a block or stilt, then glue the two wing halves together.

If you need to calculate that wing tip height you use the formula, wing tip height = (0.5 x wing span) x (sin (2 x dihedral angle)).
 
Typically you place one wing on a flat surface with a weight on it, and then lift the other wingtip to the proper height. The steps allow for the use of one jig for a variety of plans with various dihedrals.

During my R/C days, you would set one wing panel flat on the work table and pin it down. Then, you would lift the opposite wing tip to the proper height stated in the instructions with a block or stilt, then glue the two wing halves together.

If you need to calculate that wing tip height you use the formula, wing tip height = (0.5 x wing span) x (sin (2 x dihedral angle)).


Correct, either raise one tip at a time by the dihedral amount (if gluing each wing separately to the fuselage) or pin one wing flat and double the dihedral angle (if gluing the wings together before attaching them to the fuselage). The jig just makes it a whole lot easier than scrounging for objects of the right height, like coins or a stack of books, printing paper, etc. Acceptable rule of thumb for dihedral angle is 1/8" for every one inch of wing span.

Dihedral Jig in Use.jpg
 
Thanks for that picture. I also went and re-read and now understand the difference between the two sides.

Cool.

I might say this could also be a good application for Lego.
 
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