Wing attach plates on the spars

[Chris In Milwaukee]

Good morning all,

Typically, when fabricating the spars, one would attach the wing attach plates to the spar web, and then trim to the plates after everything is assembled. I'll use Eric's spar as a visual reference below.

spar5.jpg spar14.jpg

When shearing my spar webs this weekend, I sheared them to the trimmed length (where the web flange would begin), and not out to the tip of the wing attach angle. That, of course, leaves a .032" gap between the attach plates.

So, with that being said, am I able to fill the void with a .032" filler and move on, or shall I redo the webs? A call to Bob is in order, I'm sure, but I wanted to check with you all as well, in case any of you had any engineering expertise to share on the subject.

Many thanks for your thoughts,
Chris

[jaredyates]

Let us know what you hear. Can you shorten your wingspan by 4 inches?

[Chris In Milwaukee]

It was certainly a thought that entered my mind! I haven't yet determine if it affects the wing strut angle attachment angle enough to worry about the splice plate configuration.

[Chris In Milwaukee]

jaredyates (or any other 4-place builder/flyer), when you get an opportunity, would you please drop a plumb line from the inboard edge of your flaps and let me know how much room you have between the flap and your fuselage? Checking to see if I do shorten the root end of the wing a couple of inches if I'll have enough clearance between the flap and the fuselage. Thanks!

[jaredyates]

Are you doing a Patrol-style flap root with no gap, or the will yours be like the 4-place where there is a bit of full-chord wing inboard of the flap? The first option seems like the more technologically advanced and perhaps most aerodynamically effective.

[Chris In Milwaukee]

It will be the 4-place gap. Bob mentioned to me the fuselage bows out a bit in comparison with the Patrol which is slab-sided. Hence the gap. So just checking to see what my available wiggle space is.

[patrickh99]

Most of the strength is in the plates and spar caps. I would either make the attach plates a little longer with a filler. Or make the splice plates bigger and add a piece between the two webs at the strut attach point. I think you can make it at least as strong as originally planned, but it might be a little heavier.

Or build the wing shorter and add a longer tip fairing. But that changes almost all of your measurements for everything on the wing. Lots of potential gotchas.

[Chris In Milwaukee]

Thanks for the ideas, Patrick. I had considered the same for the attach plates. I had also considered making the splice plate wider as you suggested, but a filler there didn't cross my mind. Interesting idea. Bob wasn't in yesterday, but should be today. Let's see if our ideas align.

[Chris In Milwaukee]

I spoke with Bob today, and he said the attach plates are more than strong enough, and that an .032" filler would be fine. He did pick on me because the plans do show a distance that would indicate what the blank should be cut to. Glad he's got a good sense of humor. So now I can move forward without worry!

[Chewie]

But aren't your dimensions for cut length unique?

[Chris In Milwaukee]

Yes, they are. I was more interested in overall strength "theory" here, more than anything else. When I drew my spars up in CAD, I failed to dimension it similar to the way that Bob did it (out to the end of the plate), just out to the end of the flanges. So when I made my cut sheet, I forgot to add the extra length for the attach plate, and the rest is history. For the sake of surface area, I added two inches to the attach plate, will add an .032" spacer between the two plates at the "hole side", and then rivet it into place.