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W-620 main spar steel plates

T

tturner

Well Known Member
I purchased a RV-6 project that was partially completed. I am trying to determine if there are 2 or 4 of the W-620 plates required. ( these are the 1/4" steel plates that tie the two main spars together ) I only have two, one upper and lower. I can see in the drawings where they show one upper and lower on the front side of the spar but someone told me today that 2 were also required on the back side. I can't verify that from the drawings.
 
Yes, there should be 4 of 'em...

Drawings 15 and 32 show the front mounting plates. The Construction Manual, Chapter 7, page 7-1, section "ASSEMBLING THE MAIN APAR" states that there are 4 of the W-620 steel splice plates.

Each is marked with identification "scratch" to identify which position it belongs (something along the lines of top / bottom / front / back).

The Packing List for the wing should also indicate a QTY of 4 for the W-620 item.
 
W-620

Thanks for the quick answers. What is the best way to match drill a new W-620? I have two which I believe are one lower and one upper for the rear side. What if you match drilled a new upper and lower using the existing W-620's I have and drilled them about .020 undersize. Them assembled them in the aircraft and reamed them to the finish dimensions? How far undersize will a reamer handle? Any suggestions are appreciated. The fuselage and wings are finished.
 
Actually, no, it wouldn't. They are match drilled to the spar and the front/rear plates are not interchangable, especially with close-tolerance bolts. I'm not sure how the old spars were drilled but the bolt holes were not exactly square through the spar in all cases. Also, I expect the plates were done with the spars rigged for proper dihedral.

However, having said that, if it were me I'd give it a shot by using a faux spar, something built up to simulate the thickness like the false spar used in fuselage construction. That way any deviations caused by angular variation will be equivalent to that found in the actual spar. Have the machine shop use the front plates as a drilling guide through the faux spar and the new plates clamped in position in the back.

Of course, before I did any of that I'd beg the original source of the kit to have another look to see if the missing plates turn up.
 
flion said:
Actually, no, it wouldn't. They are match drilled to the spar and the front/rear plates are not interchangable, especially with close-tolerance bolts. I'm not sure how the old spars were drilled but the bolt holes were not exactly square through the spar in all cases. Also, I expect the plates were done with the spars rigged for proper dihedral.
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I totally agree with Patrick.
You can not rely on the front plates being the same as the rear.
They may be close enough to go the final ream route you mentioned but I don't think I would risk it...the alum spar is much softer than the steel and if the misalignment is very much, it could pull the reamer to the side and oval the holes in the spar.
I think a better choice would be to make a .250 and a .375 drill bushing with about a # 30 hole down the center, clamp the plates in place with the wings final installed in the fuselage (that will be a challenge with the bottom one) and drill pilot holes for all of the hole locations. Then remove the plates, and center on the pilot holes while drilling them in a mill or drill press. If you could find a way to clamp them in place and first pilot just the 1/4 " holes on the ends, you could final drill those and then temp bolt them back in place with no risk of it moving while you pilot drilled all of the 3/8 holes.
 
I would make a duplicate set of the rear plates (or have a shop do it) and then just see if they fit. If not, then go the direction mentioned in other replies. You never know, it could all line up fine. Maybe have two sets cut, one .020 undersize and then take measurments once the wings are in place and have them modify the holes if required.
 
I am going to email the builders son to see if they may have them. The builder died about 6 years ago and I purchased it last spring. It had been sitting in a hanger for 5 years and I loaded it up myself. After looking at your suggestions I will try the plates I have to see if they will fit on the front and the rear. If they do then I will just duplicate them. I am not a machinist but I do have a vertical mill and lathe.
 
WingsOnWheels said:
I would make a duplicate set of the rear plates (or have a shop do it) and then just see if they fit. If not, then go the direction mentioned in other replies. You never know, it could all line up fine. Maybe have two sets cut, one .020 undersize and then take measurments once the wings are in place and have them modify the holes if required.
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Colin... we do think alike. A simple reamer and an step up oversized bolt may just do the trick if the plates did not line up. Ahh, but what the **** do we know. :eek:
 
LifeofReiley said:
Colin... we do think alike. A simple reamer and an step up oversized bolt may just do the trick if the plates did not line up. Ahh, but what the **** do we know. :eek:
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This type of plan might work...the problem with reaming in place is accessibility.
It would likely be very difficult on some holes. That was the reason for my recommendation of drill bushings. A 12 " extension drill could be used. It is even a bit flexible to make access easier.
 
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