Splicing spars to extend wings

4 posts in this topic

Posted

I highjacked another thread a while back and thought it would be best to start a new thread to ask for input. The plane I am working on has an aerobatic speedwing that I would like to extend to either the standard Avid length, or possibly the longer Kitfox wingspan.

I have discussed this a little with Jim and he had a good idea to use the I beam stiffeners that are available from Just Aircraft as internal splices. I think this would probably work well but I am also thinking about using pieces of old heavy hauler spar that I already have to make internal splice sleeves. What I am thinking is to cut a notch in the length of the spar splice piece so it will slightly collapse and fit inside the spar and then rivet through the spar and the wing extension into the splice sleeve.I remember seeing in an Avid builders manual they did something like this from the factory, I believe on the Magnum and Catalina spars. Does anyone have any details on this like the length and thickness of the spar splice sleeve and the number and spacing of the rivets?

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Posted

I used Avids instructions when I extended my aerobatic speedwing. Use a 12" piece of .083 spar with about a 1/2" strip cut out lengthwise. mark a line at 6"and put a slight taper on both ends. squeeze with hose clamps and insert into the spar 6" I found a drill pattern online but there wasn't anything special about it. Pay attention where the slot is located and don't drill to close to those edges.

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Posted

Birddog, that's exactly what I had in mind. Thank you for the info!

I have a wing with a bent spar that I can use for the splices but I didn't have the details on how big the splice needed to be. Now I need to see if I can find a local source for some .083 tubing for the spar extensions and I will be set.

One more question - Did you increase the wingspan to the standard Avid span or did you go with the longer Kitfox wingspan?

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Posted

I added three feet. I think that makes it the standard long wing length. If your wing is already built it wouldn't be the best idea to extend it more than 3' if you've built in the washout that the plans call for. The 2" of washout adds a lot of drag and extending beyond 3' could make the negative performance outweigh the benefits of the longer wing

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