Spars

[Jflyer]

I'm no where near the point of making the spars, but dream building in my head, reading the plans, manuals, and build sites, trying to scope out various items. The manual and The Bob Book explain to cut the spar blank the height of the rib, adding in 1/8", plus the 9/16" for each flange. Directions understood.

Looking at the pictures from various plans built spars including Eric Newton's world famous and seriously 'underpriced' builder's manual (plug-plug), there looks to be a bit of a gap between the cap strips and the top and bottom flanges, which does not appear to be consistent from one builder to other. It would make sense for there to be a variance between builders as it's based on the accuracy of the ribs, spars and wing attach plate each builder manufactures.

My question is this: Is there a tolerance level to stay within for this gap, or is it a 'do the best you can' scenario? Or Is less than 1/8" to small and may cause binding and more that 1/4" too large which could cause structural issues?

[markphillips1228]

There will be small differences in the gap between the bottom or top of the cap strip and the flange. But for most people it will be almost the same. I think the crucial distance is the center of the capstrips being 6" apart ( im not looking at my plans now but I think that is the distance)

[X'N]

I believe the real difference in what your seeing is how people bent their spars or should I say how wide their center ribs are. The overall distance between the top and lower cap strip should be 7 1/4. If made per plans (7.59 inches) that would leave .17 on either side of the cap strips. If someones ribs were say 7.65" that would leave .2" on either side. + the top main spar web leg is also only bent to 82* so visually that could make them look different.

I also believe bob put that gap in there so the cap stip would not rest on the radius of the spar web.