Hatz Biplane Association

Drawing 16 shows bushing stock for both the front and rear connections for the bottom wing. That is the only place I see bushing stock for the wing or gear connections. All the rest are 4130 tubing. First question is, can bushing stock be welded?

Because of the bushing stock would indicate a connection that rotates (even though slightly) I assume that the bolt should be a drilled bolt with a castle nut and cotter pin.

I know for sure that the gear rotates in the fuselage connections. The bolts for those connections are AN5-16A. Again, shouldn't they be AN5-16 with a castle nut and cotter pin?

I'm having trouble visualizing what you are asking. Could you cut and past a picture of the plans area in question?
What I think I'm reading is you are talking about where the brackets from the wings bolt onto the fittings welded to the fuselage. If so, then there should be no rotation after you finish rigging.
Bushing stock: I used 1/8" wall 4130 tubing and reamed the ID for the bolt. If it's actually bearing stock-that's another story.
As far as which bolt to use, if the bolt has the opportunity to rotate then you need the cotter pin/castle nut. There are some cases (bearings) where you clamp everything solid, and the outer race is what moves, then no cotter pin/castle nut.
With that said, I used cotter pins/castle nuts anywhere I wanted the "warm and fuzzy" security.

Jeff Moore

I did the same as Jeff, 1/8 wall 4130 and reamed for the bolt. I did have the same question as you but there are so many things like that on the plans that I went with what made sense to me. Of course that doesn't make it right but I hope my wings don't rotate.

Thanks guys. Partial copy of Fuselage Fittings attached. I had another builder walk in today and I grilled him also. He's just an RV builder but he came up with the same answers.

I think I'll use 0.50 diameter 063 wall 4130 tubing for the main spar connection rather than the bushing stock as you suggest. I'm still debating whether to use lock nuts or castle nuts and cotter pin for the wing mounts. I'll use the castle nuts and cotter pin for the gear mounts as there will be some rotation there.