Author Topic: XL Spar questions  (Read 638 times)

Online 914pete

XL Spar questions
« on: July 12, 2019, 08:42:15 AM »
I've been reviewing my XL plans to build my spars and have a few questions:

Why are the cap strips tapered at the wing tips?
Where are the 1"x3/8"x154" and the 5/8"x5/16"x154" cap strips used?
ACS only sells 12' Spruce cap strips so I'm assuming they have to be spliced to meet the 154"? Is there another source for 13' lengths?  If I have to splice, whats the best location to do that and procedure?
The plans just mention "plywood" for the spar webs. What type of ply is used? If its the Domestic Birch ACS has Is there a difference between domestic birch ply that ACS sells and any other lumber yard finished domestic Birch product?

Offline Tom XL-7

Re: XL Spar questions
« Reply #1 on: July 12, 2019, 11:06:23 AM »
taper on the cap strips at the outboard end is only to reduce weight. The loads diminish as you get to the end so the heavier section is not needed. Wouldn't surprise me if some skipped that work

The 1x3/8 is the trailing edge of the wing. It is to be tapered. may be available that way. the 5/16x5/8  goes in the nose ribs notches. I have not been able to confirm that so look for it there(that drawing is not with me and I am too lazy to get the original set or nose rib template)

Call ACS and talk to a sales person, she called the wood shop and they had it so they sold me 13' Same on 5/8 tubing got two 14' for lower longerons

the ACS dom birch plywood is aircraft grade and meets MIL-P-6070. Do you need that? my rear end does- if it is structural I will spend the money

Offline Tom XL-7

Re: XL Spar questions
« Reply #2 on: July 12, 2019, 11:11:13 AM »
I talked to Robin Mc Hugh ext312 or a direct line is 877-477-7823 that was 8 years ago. if she is still available she was most helpful and patient.

Online 914pete

Re: XL Spar questions
« Reply #3 on: July 15, 2019, 07:51:40 AM »
Thanks for the replies Tom. I see now on page 36 the reference to the trailing edge. Very blurry on my copy. I saw on the ACS website they carry "Spar Stock" in 13+ foot lengths. I'm assuming its better structurally to go with full lengths and using a table saw to rip the sizes needed? I'm assuming cutting the sizes needed is more cost effective too. Is this what builders have done? The truck shipping cost will be more then double that of UPS though.

Offline Kamcoman77

Re: XL Spar questions
« Reply #4 on: July 15, 2019, 10:11:01 AM »
I bought two 14-foot spruce spar stock pieces 3/4" x 5" from ACS and cut all my spar caps, compression struts, and diagonals from them. I still have a few strips 1/4" x 3/4" left over. Even using a thin blade on my table saw, I lost 1/8" of wood with each cut. I still saved some money over letting ACS cut everything, BUT shipping was not an issue since I only live 30 miles from them. If you make proper scarf joints, they should be every bit as strong as a solid piece. I plan to splice my TE using a 15 to 1 scarf. If I were in your position, I would go with whatever sizes of wood gave me the best price, shipping included, but would order lengths that only required one scarf/splice per spar cap.

Online 914pete

Re: XL Spar questions
« Reply #5 on: July 15, 2019, 10:57:31 AM »
Thanks Kamcoman....Did you have enough material to cut the leading and trailing edges as well with the two 3/4x5"x14 footers? I'm leaning towards full length because I also have to buy the plywood so the truck shipment might be my only option. I was able to buy 1/4"x1/4"x5' caps and the .8mm ply for the rib gussets which they rolled and sent UPS.

Offline Kamcoman77

Re: XL Spar questions
« Reply #6 on: July 15, 2019, 11:19:16 AM »
Not quite enough left over for the trailing or leading edges. I'll cut up my leftover 1/4" x 3/4" strips into the 1/4" x 1/4" called for as aileron cross bracing. I used 4-foot long sheets of 3 mm Birch plywood for all my spar webs. Instead of butt joining the pieces, I made scarf joints in the webs to make one, 13-foot long sheet of ply. You might save some freight by using 4-foot plywood instead of 8-foot. Used a belt sander to make the scarf joints.