Fitting the tailwheel spring mount^3h

Today I went back to the aft fuselage and fitted the WD-409 part.

Since my tailwheel assembly was on backorder, I thought it would be a smart idea to get a new WD-409 part to fit it to the fuselage.

I spent some time opening the cut-out on the bottom skin to fit the mount, to get the initial fit.

I will probably need to grind the skin some more once I powder-coat the part.

After that, I proceeded to match-drill with the F-711. I was hesitant to match-drill since I didn't want to ruin the holes in the F-711 part in case the drill would wander on the steel part.

So initially I tried to mark the location of the holes on the mount using the transfer punches and drill them. I got to 5/32" holes when I stopped because I did not like their location (they were a bit off). Again, guestimating the location of the holes, it seemed like they are spaced 3" apart with a 3/8" edge distance. Since 3/8" is not a lot to spare (given that bolts are AN4, which use ~0.250" holes), I decided to move over to my mill again and locate holes exactly. Which I did. Since the holes were started already I used my 1/4" end-mill to bore the holes in proper locations. It worked well, the bored hole cleaned all the drilling I did before that.

Then I suddenly realized that I can take F-711 out of the fuselage (which I should have done before!), so I took it out and simply reamed the holes to 1/4". They perfectly matched the holes in the WD-409, so at least that part worked well.

Finally, I drilled the holes for the keeper rivets estimating their location based on the drawing. I opened the "mouse hole" so it does not interfere with the welding bead.

I was happy with how the part turned out. Up until the moment when I wondered why the plans do not tell me where to drill the hole for the tail spring. After a bit of research I have realized that when you get the whole assembly, it comes pre-drilled to the spring. So now I need to figure out what to do about it. Drilling to an existing spring is probably not going to work well -- it would require some smart fixturing to locate the hole precisely.

I am probably going to buy a new tail spring, then drill it to the mount in my mill (I can also do a taper pin mod at the same time). And I can sell the original assembly, as I don't need anything else from it (I am planning for a different tail wheel).