Wing Spar Attach Fittings and Fuselage Alignment

[alaskabearhawk]

I'm just getting my head wrapped around putting the wing spar attach fittings on my fuselage and the process behind it. Alignment, incidence, clearances, etc. Out of all the info I have, it seems like most make the fittings, line them up using water levels, weld them, put the wings in place and match-drill the fittings to the wings using long contraptions. Adding to the mix is having the front and rear spar bolt holes offset from each other.

I was thinking...it seems the process would be easier to make and fit the fittings, finish drill the bolt sizes (5/16ths for the rear and 3/8ths for the front) through the fittings and spar attach points and bolt them together, using a very thin washer on the inside to compensate for future paint. I would then put the fuselage on the table, level it up and secure it. Then jig the wings in their proper position (incidence, distance from tailpost, etc) and tack the fittings to the fuselage? Once they were tacked in place with good tacks, you could also cut and fit the wing struts and put in all the pulley brackets for the flaps and ailerons at the proper angles.

Another option is to make a jig that mimics the wing spar attach points and use that as a guide, but would still need the long drill contraption to accurately drill the spar bolts. Any thoughts?

[tf104]

I have not given this much thought as I am still welding my fuselage. What about just welding the front attach points prior and welding the rear in assembly as you have suggested?

[alaskabearhawk]

There is still the vertical variable in there, along with other issues. There has to be some alignment of both mounts simultaneously with any method.

[X'N]

How about making a jig that fits the root end of the wing? Say take some 1/2 MDF and cut slots for the attach brackets, then slide it over the brackets to the root, trace the airfoil shape and cut out. Then bolt on some say 2" angle and match drill the holes in the spar attach plates, then take them off and make a false wing spar attach plate(s), match drill again, remove the angles and you should have perfect replication of the wing. sorry kind of hard to put into words.

[alaskabearhawk]

That is an intriguing idea. There will have to be one made fore each side. I'll have to think about that.

I think someone else did what I'm proposing, but I didn't tag the photo as to who this was or know if it worked out as planned.

[mswain]

The builder I know locally did it exactly as you described (Tack in place using the wings) on his bearhawk and patrol.