Mounting the Wings - Spar and F-704 tolerance

[txnbuilder]

I am in process of riveting the center fuselage, and while I was fitting fitting the center section bulkheads (F-704), I remembered this line in the manual regarding the spacer blocks:

"...The length of these spacers must be 1.438" (1 7/16") to match the thickness of the spar..."

Well, it occurred to me to go measure the wing spars. They are somewhere between 1.444" and 1.450", depending on where I measure. (These measurements are after squeezing together the three pieces that make up the spar).

Also, after measuring my spacers several times, they are more like 1.435"

So, in short, the wing spar is going to be about 1/64" thicker than the space where it is supposed to fit.

The engineer in me wants to believe that when Van's says 1.438", they *must* mean 1.438" +/- some tolerance greater than 0.000" However, I can't get over the fact that 'the hole is smaller than the peg'.

After searching the forums, I can't find anyone complaining about this, so does that mean there will be enough play to wiggle the spar in there when the time comes to bolt the wings on?

Any insights?

Luis

 

[Bruce]

Luis,

If you have NOT rivetted the bottom skins I would (Rebuild spacers) first and
if you have rivetted then call Vans.

They have to be 1.438 inches. It is a tight fit.

Hope it helps.

 

[txnbuilder]

No rivets yet

Thanks for the advice Bruce. I have not riveted the bottom skins to the center section bulkheads yet, so I can still make small adjustments.

After talking with another builder, I am going to try to make new spacers out of MDF, and use a table saw to try to get it closer to 1.438"

It would still be nice to have a tolerance spec, even if it is indeed +/-0.001"

Luis

 

[benbell4140]

If you have any machinist friends have them make some spacers out of aluminum. That's what I did and although I haven't fit the wings yet, I know that the spacers are to vans specs plus or minus 0. Hopefully I won't have any problems.

 

[RV7ator]

Guys,

(Geeze! After the coffee took effect, I re-read the thread starter and my initial response was totally inappropriate. I was thinking of the bushings around a couple of the bolts. Here's the corrected version.)

The center section will be defined by the pre-punched holes in the skins and doublers. Don't try to "adjust" anything. The wood block spacers are an artifact from the non-pre-punched RV-6 instructions and are totally useless. Don't bother with them.

Chamfer the spar ends (front and rear spars) 1/16 x 45 degrees and apply some sort of thin lube (like Corrosion-X). Those wings will slide right in.

John Siebold

 

[LettersFromFlyoverCountry]

I made my spacers out of a combination of MDF, plywood, and cardboard beer cases. Given all the prepunched holes in this area -- the "H" pieces in particular on the sides -- it's going to be pretty hard to build your project in a way that the spars DON'T fit.

 

[rzbill]

I used 3/8" threaded rod cut into short pieces and a bunch of nuts/washers.

Adjusted in place until gap measured OK and then locked 'em down.

Double nutted the "inners" so that the adjustment could not move.

My spars fit fine.