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Installing Correct Diheadral

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Installing Correct Diheadral

Old 03-07-2019, 10:35 AM
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Default Installing Correct Diheadral

My first scratch build from plans by AMA Plans Service. It is the "Old School" design and drawn by Larry Kruse. It's a design that is directed toward the new builder. The plans call for 1 1/4" dihedral at each wing tip. This is my problem How do I get the 1 1/4 inch dihedral. This may sound simple to some but to me it's driving me out of my mind. What is the best method to sand the center ribs to conform to this dihedral.

Old 03-07-2019, 10:39 AM
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Are the root ribs thicker then the rest and can be sanded to the correct angle or are the intended to be glued in at the correct angle? Does the airplane have ailerons and what is the wing span?
Old 03-07-2019, 02:26 PM
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What I do it assemble a wing but don't glue in the root rib yet. Then block up the wing tip 1 1/4" and glue in the root rib vertical to the building surface.
Old 03-07-2019, 06:42 PM
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Copied from
Old School Model Aviation

"The dihedral angle is set by propping up each panel 1-1/4 inches at the tip, holding a sanding block vertical to the work surface, and gently sanding each center rib. Trial-fit the wing panels, sanding again as needed, and then pin down one panel while raising and supporting the other panel 21/2 inches at the tip.

Thick CA or epoxy can be used to glue the two panels together. Sand the wing, and then using thin CA adhesive, glue a 5/8-inch strip of lightweight fiberglass over the seam to strengthen the dihedral joint."
Old 03-13-2019, 08:58 AM
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This trick of blocking up the wing and sanding the face works easier if you can set the wing's root face right at the edge of the bench and using a large sanding block work with pressure against the edge of the bench to aid with keeping the sanding at right angles. Obviously though this may not work super well if the edge of the bench is quite thin and there's not much support to hold the block vertical to the bench top.

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