Tommygun

My Feedback: (2)

I had both these wings snap in the midst of a very literal "snap roll." What do you guy recommend for the best repair possible? It flew very light and well, and has lots of excess power, so adding some weight won't really be a big deal. I was thinking some kind of spruce or possibly even carbon fiber reinforcments? This is for a very old (30+ year) Sig Liberty Sport.

Tommygun

My Feedback: (2)

You can see the kind of damage it did to the spars and beams...

Bax

My Feedback: (11)

Basically, you have to remove the center section sheeting on the top or bottom of the wing, carefully butt the wings together at the proper dihedral angle, and glue in a plywood center-section reinforcement. You may have to trim the ribs so that you can install the plywood. Use a piece of 1/16" ply to reinforce the leading and trailing edges.

If you sandwich the spars between two pieces of 3/32" ply that's the full depth of the wing, you should be OK. Use pieces of card stock to determine the shapes of the new joiners you'll make. Just butt the wing halves together and lay the card stock against the spars and trace the upper and lower spars. Make the joiner extend at least 1-1/2 rib bays out from the center. If you need to remake the center ribs, either use the old one as a template, or use a piece of card stock to trace the contour of the next rib out.

Use epoxy to hold it all together. Replace the sheeting you removed with new stock of the same thickness as the original.

An alternative would be to remove the covering from the center of the wings, butt-glue the wings together with epoxy, and then wrap the center of the wing with at least a 4" wide piece of 6-ounce fiberglass cloth. Use epoxy or polyester resin to bond the cloth to the wing. Many a 60-size Pattern plane had the glass cloth as the only reinforcement to the center of the wing, and they held together very well. All the old kits by Joe Bridi had the wings joined in that manner. Very strong.


When you're done, just clean up, sand, and recover.

Tommygun

My Feedback: (2)

Okay, here's what I've done so far. I'm using spruce strips to reinforce the spars...here all the center sheeting has been removed. I used a razor saw to cut away the ribs from the spar, and wood files to clean up the back of it for smooth bond.

Tommygun

My Feedback: (2)

This is the spar, and I used a shaped dowel for a leading edge insert.

Tommygun

My Feedback: (2)

Here's everything bonded. I used West Systems epoxy with some microballoons. The top wing has the spar test fit already, but I'll wait to glue it until tommorrow.