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WD-409 tailspring mount F up…

Clayvt

Clayvt

Well Known Member
Patron
While drilling the tailspring mount to F-711 I didn’t realize it had shifted after punching through the first hole and now they don’t line up at all.
Vans is back ordered with an ETA of 2/28/26…

What do folks think of having the holes welded closed and trying again? Would there be strength issues/possible crack avenues? Aft fuselage is on hold till this gets sorted. Guess I’ll start on the center section in the meantime.

Any suggestions would be helpful.

Great joy seeing this come together!
IMG_7546.jpeg

Followed by awful sinking feeling…
IMG_7551.jpeg
 
...aw snap...Stuff like this happens.

I'd weld closed the holes, clean up the slag - grind it smooth, prime/paint. Then measure/mark/clamp, match drill with a drill bushing through the rear bulkhead. Then upsize to final size. The bushing will keep you from making the existing hole in the bulkhead any larger.

This is a bit of a pain - but install the tailspring, tailwheel yoke assembly and align everything vertically *before* drilling up the WD-tailspring mount. You don't want the tail wheel to sit cocked off to one side...

As an aside, invest in a CP-214 (or clone) pneumatic squeezer, as many different size/type yokes as you can find, an Avery/Cleveland squeezer set, dimple set, and adjustable set holder...
 
Yes I also think welding closed the holes and re drilling makes sense. I had something similar happen on another part. The holes were out of alignment by about half a diameter and an experienced TIG welder closed them up halfway so the hole could be "shifted" to the correct location by filing it (with a chainsaw file) and then final drilling to the correct size.
 
I did a very similar thing. After consulting with Van's I chose to fabricate a rectangular doubler of .063" 4130 and had a buddy TIG weld that doubler in place over the old holes. I then redrilled the assembly. I did not bother filling in the old holes but my misalignment was extremely small, less than 1/16th".
 
If it is just the holes in the triangular plate on the end (as shown in the photo) I would get another piece of 4130 and manufacture a new end-plate. It's not a big job to cut off the old one and get a shop to weld on a new one. The alternative is wait for a new item from Vans but if you're making good progress and don't want the downtime then I'd do the repair.

Good luck.
 
Maybe you saved yourself 1/2 the work if at least one hole is in alignment?

How close is the other hole to the next size up bolt diameter?
 
Found a new in box tail spring mount in the hangar yesterday. If interested PM me. Think it is a WD409. For a RV7.
T.S.
 
I got the new mount installed and everything has been put back on track. Thank You T.S!
 
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