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Procedure for Spar lamination?

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wmax351

Member
Joined
Oct 10, 2018
Messages
11
Location
Ann Arbor, MI
I'm currently in the planning stages of building a flybaby. I'm considering a laminated spar, since it would allow me to be more certain of the quality of the wood, as I could inspect it every 3/4 inch or so.. I would likely purchase the wood at public lumber in Detroit. Options include "Spar and mast" grade sitka spuce, Doug fir, white ash (and any other suggstions).

The spars are 3/4 x 6nom and 4.5 nom. x 13 feet

My initial plan is below, all dimensions are exact. I'd appreciate any suggestions and tips.

1. Rip 1x3/4 or 1/2 pieces. Inspect, test some 1/2 x 3/4 or 1/2 samples to destruction from each board.
2. scarf together as needed for ~14' or 15' lengths. Scarfs will be offset by >3 scarf lengths, or 2 layers.
3. prepare a straightedge form, using metal stock or very straight wood/mdf covered in duct tape and saran wrap. Spar will be built with the long edge flat on the table. A mold board will be used on top, screwed to the table to provide a flat side. The clamping will be provided by numerous 1x2 wedges, opposed to each other in pairs, pressed against a board running ~3 inches past the dimension of the spar. One will be placed and tacked with a Brad nailer, the other will be tapped into place to clamp, and also tacked in place.
4. glue will be t-88. Allow to cure fully at 70+ degrees.
5. when complete, will be inspected, planed to 3/4 exact with thickness planer (I can use my father's nice one for the cost of greyhound freight to ship it), and then reinspected.
6. ~ 1 foot sections will be removed from one or both ends, for destructive testing. I am planning to find a shop with a hydraulic press with a guage, and it will need to be loaded to about 5-6 tons in the middle of a 1 foot span. After that, I will test for destruction at the glue joints by the hammer and vice method with 1 inch blocks from the end of the sample.

I figure I will get a nice Spar that I can be very confident in this way, for a lot less than A/S (~600 dollars plus shipping).
 
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