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Wing Spar Center Section Fit

mfleming

Well Known Member
Patron
-7, standard wing kit, QB fuselage.

I made some measurements today (after Van's tech support closed of course) that have me a bit worried.

I measured my wing spar thickness and my center section width and the numbers don't look good.

Here are the numbers:

Left wing spar top - 1.4450"
Left Center Section top - 1.4080"
difference -.0370" :(

Left wing spar bottom - 1.4450"
Left Center Section bottom - 1.4270"
difference -.0270" :(



Right wing spar top - 1.4460"
Right Center Section top - 1.4315"
difference -.0145"

Right wing spar bottom - 1.4540"
Right Center Section bottom - 1.4365"
difference -.0175"

In all cases the center section is to narrow for the wing spar to fit easily.

This is the only thread I found on this issue.

From reading the previous thread it appears that with .010 to .015 one might be able to massage the wing spar into the center section. But .027 / .037 seem a bit much.

Any thought on this until I can call Van's on Wednesday?

Here's some photos where I measured:

center.jpg


spar.jpg
 
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The curse of pictures

Hope Vans can solve your problem.

I really appreciate the heads up on this critical measurement.

Looking at the picture, and having completed this step no more than 5 minutes ago, check there are at least 1 full thread sticking thru the nuts on the front and rear center section spar bolts. It is not clear in your picture, but I had to use an AN960- 10L washer on these, instead of the AN960-10 washer( the thicker version)
 
I'm very interested to hear what Van's has to say on this one. I would think that the spacing is set by the spacers and mainly the side center section plates.
 
Hope Vans can solve your problem.

I really appreciate the heads up on this critical measurement.

Looking at the picture, and having completed this step no more than 5 minutes ago, check there are at least 1 full thread sticking thru the nuts on the front and rear center section spar bolts. It is not clear in your picture, but I had to use an AN960- 10L washer on these, instead of the AN960-10 washer( the thicker version)

I'm very interested to hear what Van's has to say on this one. I would think that the spacing is set by the spacers and mainly the side center section plates.

I called Van's and they are conferring with Gus and will call back :eek:
 
Not at this stage yet, but when I built, I machined some hard Delrin spacers for the spar carrythrough before I riveted it to the fuselage structure. In my opinion Vans instructions are poor here (I think they mention a wood block). The spacing should have a machined spacer and I think Vans should supply it.

However, this doesn't help you. This also happened to a friend of mine, and Vans recommended de-riveting the skin overlap on the bottom of the fuselage, insert the spars (or machined spacers would probably work)and re-rivet the skin overlap.
 
another suggestion

I would also suggest you make sure there is absolutely no debris between the spar's shear web and the spar caps that could be making the spar 'thicker'
 
Van's Called Back

So I heard back from Van's.

They thought the numbers I posted earlier were within the tolerances needed to successfully mount the wings.

Chamfer the spar ends and use a block of wood to lever the center section open a bit and I'm good.

It will be a bit before I'm ready to do that, so I won't be reporting back right away.
 
I believe it will be ok also.
Spray the spar mating areas with a little Corrosion X, they will slide together nicely.
 
Sorry for reviving a necro-thread. But, how'd it go?

I'm ready to make the center section spacer, prior to riveting the center section to the fuselage, and when I measure my wing spars, they're about the same as the OP's.

Curious to know what happened.
 
Spacers

Sorry for reviving a necro-thread. But, how'd it go?

I'm ready to make the center section spacer, prior to riveting the center section to the fuselage, and when I measure my wing spars, they're about the same as the OP's.

Curious to know what happened.

Not sure how Michael came out but I recommend a set of spacers. You can buy them from Buller or make a set. A few thou wider than your wing spar bars is enough. I bought a set from Larry Buller .005" wider. Wings needed a little lube and persuasion but slid right in.
 
Sorry for reviving a necro-thread. But, how'd it go?

I'm ready to make the center section spacer, prior to riveting the center section to the fuselage, and when I measure my wing spars, they're about the same as the OP's.

Curious to know what happened.

Unfortunately I haven't fitted my wings yet. I thought that would happen this winter but no luck.

I talked to Van's and they said the numbers I posted should not be a show stopper. BUT their suggestion was....wait for it...use an oblong axe handle, fit it in-between the center section and twist, then slip the wing spar in...

We'll have to see on that one :eek:
 
Not sure how Michael came out but I recommend a set of spacers. You can buy them from Buller or make a set. A few thou wider than your wing spar bars is enough. I bought a set from Larry Buller .005" wider. Wings needed a little lube and persuasion but slid right in.

These spacers must be for if the wing spar is a bit narrower than the center section...correct
icon5.gif
 
Spacers

These spacers must be for if the wing spar is a bit narrower than the center section...correct
icon5.gif

Either or both but if the wing is smaller, there's no issue. The wing will fit. You won't know for sure till the fuse is done unless you bolt a set of spacers in the center section to hold it to the dimension required. The idea is you measure the wing spar and make or buy spacers a tiny bit wider. Seems like the spacers are in the manual but I may be mistaken. When the fuse center section is assembled, the spacers are bolted in place and left there till the skins are riveted. Theoretically, when they come out and wings go in, the space should be perfect. We're taking very little extra. Mine were .005" and my wings were pretty snug. Had to get everything perfect before they started going in.
 
Unfortunately I haven't fitted my wings yet. I thought that would happen this winter but no luck.

I talked to Van's and they said the numbers I posted should not be a show stopper. BUT their suggestion was....wait for it...use an oblong axe handle, fit it in-between the center section and twist, then slip the wing spar in...

We'll have to see on that one :eek:

I made a spreader with a bolt and bar to push against. One on top and bottom. The outer holes could be used if the wing can be held in position while the spreaders are removed. The width was monitored and the torque on the bolts to generate the spreading force was quite low. Under 20 in-lb. I got flamed for posting previously, but it was tested and the gap returned to the original with the forces applied. Much more controllable than a blanking axe handle, but exactly the same result. If anyone actually wants to do this, email me.
 
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I made a spreader with a bolt and bar to push against. One on top and bottom for the inner large bolt locations. The width was monitored and the torque on the bolts to generate the spreading force was quite low. Under 20 in-lb. I got flamed for posting previously, but it was tested and the gap returned to the original with the forces applied. Much more controllable than a blanking axe handle, but exactly the same result. If anyone actually wants to do this, email me.

Sounds better than an axe handle to me ;) I'll send an email shortly.
 
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