Spar issue

[shipljl]

The front spar from my prewar BC12-65 has notch in it that I am concerned about. The edge of the spar has been notched to allow room for the compression tube between the front and back strut attach fittings. See the attached photographs.

The logbooks would have me believe that this is an original wing. Does anyone know if this was common practice? Or if not, any suggestions for a repair short of replacing the spar?

[Edwin Otha]

Re: Spar issue

I've seen some others assembled that way. Don't know if it's right but not uncommon.
EO

[freightpilot27]

Re: Spar issue

My wings are Original as far as I can tell (they still have the original data plates on them). One is early '46, one is early '47, both with stamped ribs. Neither are notched.

[mulwyk]

Re: Spar issue

my wings ('46, original) had a notch like that, but maybe not as deep...wish I had taken a picture. When I assembled the rebuilt wings I was able to do it without a notch, but just barely. I'm thinking that in a factory production enviornment, assembling wings in a jig, the notch was used to compensate for some dimensional variation in the spar. So some wings had it, some didn't.

[shipljl]

Re: Spar issue

Thanks for your responses.

[Robert Lees]

Re: Spar issue

It looks "factory made" to me. That tubular collar keeps the fore-and-aft spar brackets apart, and needs to be there to prevent the spar from being crushed when the wire that passes through is tightened up. When I rebuilt my wings, that collar was there but just missed the lower spar face.

Forrest will know best. My opinion is that if it looks original, it probably is. Is the wood surface varnished? And does it look as if the bracket bolt holes have ever been relocated or rebushed?

It does make me wonder what geometry went awry during manufacture.

Can you measure the height of the spar?

Where is Tremonton? I know southern Utah fairly well: St George, Moab, and points between.

Rob

[shipljl]

Re: Spar issue

Tremonton is about 30 miles from the Utah Idaho border.

The groove is varnished. The bushings look original and not modified. I haven't been able to find any markings that would tell me that the spar is original even though the logs don't indicate a new spar. Where would I look for the marking or stamp that would have been put on at the factory?

[shipljl]

Re: Spar issue

The full spar height is 5.790 inch. The reduced height with the groove is 5.630.

[Forrest Barber]

Re: Spar issue

Does not look factory to me, keep checking to see if spar replaced, that is a real critical thing being on the outside of the spar will check dimensions, I see others have found notches. perhaps theirs were replaced too?

[Ray36048]

Re: Spar issue

I have a set of 1941 spars, no notch.

[Larry Lyons]

Re: Spar issue

Ditto on my 41, no notch!
Larry

[shipljl]

Re: Spar issue

After careful investigation I found something I missed in an old 337. The entry said,

"Left hand wing assembly, forward spar at main strut fitting. Three inch crack at center of original reinforcing plate repaired by replacement of plates and extending to cover crack and three inches beyond in accordance with Figure 2-8 C. A. M. 18."

If I understand this correctly, he says he replaced the reinforcing plates. At this point he may not have drilled the holes for the strut attach fitting in the same exact location. If he drilled the holes a bit high, he would have needed to notch the spar to make room for the spacer shown above.

If this is true, then the strut attach bolts might only be supported by the plywood reinforcing plates and not by the spruce spar wood.

Does anyone know what Figure 2-8 C. A. M 18 refers to?

At this point, without better information I think I will replace the spar. Anyone else who has notches in their spars might want to investigate further as well.

Thanks for all your input,

John

[Robert Lees]

Re: Spar issue

Reading CAM18 (filed here at the FAA under CAM215 [6 Mb download]), I think it would mean Figure 2 to Figure 8.

This looks like a predecessor of AC43.13-1

[Ray36048]

Re: Spar issue

How many years and hours did it fly after the repair?

[shipljl]

Re: Spar issue

The repair was made in 1964.