To glue or not to glue, that is the question!

[Sweet B]

OK, should you glue the aluminum spars strut/wing root attach plates to the spars before bolting in place ?

[Chuck in Indiana]

I can't think of a good reason to do that..

[jrbirdman47]

I did. Just figured it gave it more contact area between metal and wood, microscopically, so to speak, so less movement and less chance to batter the through bolt against the wood. Did the same at the root end. (Kind of the same reason I bed a rifle action in the stock, so there is no movement, although for different reasons)

[Kamcoman77]

Leonard Miholland bedded his fittings in epoxy, per his Wing Video. I watched his old video last night and he mentioned it twice.

[Sweet B]

I guess my concern is I won't have the luxury of a hangar so it will be be more like Les of trailing it to the airport and assembling on site. So far as many times I've fitted the wings to the fuselage I notices I've been gouging the bracket pretty good. I've since replaced the bracket but wondered if it will be possible when glued to replace without damaging the spar/holes. I'm kinda stuck on the decision.   

[Kamcoman77]

Perhaps you should explore the strength versus weight of 0.090" 4130 and 0.124" 6061T6.

[Chris Hudson]

Been around this homebuilding stuff since Rockford Old timers will know what I'm talking about. I had never really heard about this gluing the fitting on also till I got around some sailplane plans where it seems to have been something of a practice, I believe the Woodstock does it. the other homebuilts I've been around the bipes etc. it certainly is never done, for good reason since the glue line would crack with the first 6 g pullup. Again I think it is a product of the glider guys and the ultra light guy's picked it up, as far as it's validity, yeah I think replacement is a big issue.

[Chuck in Indiana]

I've been around since Rockford, too.  I've never heard of it on homebuilts, although I don't suppose it would hurt..

[DA Miller]

since this subject is sort of like "bellybutons"; everybody has one, here's mine. The original question arose from having replaced wing strut fittings and the likely hood of having to do it again. I think the fittings should NOT be glued. Our destructive tests of the glue joints show tearing of the wood fibers; how could you not have wood damage when removing the fitting for replacement?  Besides, what real benefit does the glue provide?

[Kamcoman77]

Good points about removing the wing fittings. If the worrysome issue is hole enlargement where the mounting bolts go through outer fitting end (not through the spar) I would just drill the hole oversize enough to insert a metal bushing to restore the 1/4" bolt hole. I think I would change fittings to 0.090" or 0.100" 4130 if I knew I was going to remove/replace the wings often.

[jrbirdman47]

Another reason for glueing was that I would most likely be storing the plane in a small barn, which is very nearly like tying it down outside minus the rain and sun, yet still subject to condensation, etc. I was thinking about how the older Cubs, Champs, etc., had wood spars and after a few decades we began to see spar failures at the wing attach fittings because it was difficult, if not impossible to inspect the area underneath the metal fittings themselves without disassembling the whole thing. Wood rot was hard to detect there, and probably even more difficult on the LE. I thought that glueing would effectively seal the entire area against the invasion of moisture and I wouldn't have to open the wing and disassemble the thing from time to time so I could sleep at night. Not exactly the reasons Sweet B was asking about, but food for thought anyway. It's my first build, so I could be way off in my reasoning here too. I agree that using steel attachment fittings would be the way to go in his case.