HS Forward Spar

When drilling the forward spar to the HS-714 and 710 reinforcement angles the two of the holes were slightly oval and elongated in one direction (aprox 0.137in). The second inboard hole in the picture will be upsized to 3/16 later so it is not an issue, but the inboard first hole shown in the picture will need to be dimpled to sit flush and will enlarge more.


https://eaabuilderslog.org/?blprojentry&proj=7YL1dRvO9&e=7ZxKrT7jf&listcat=

I see two options:

1) Leave it and set the rivet.

2) Upsize to a -5 flush rivet. I have about 2d in the reinforcement bar and spar. This it is less than the 2.5d rule of thumb, but will be within the MIL-Spec 4719-6A edge distance requirements for both dimpled and countersunk rivets. I would probably upsize both of the bottom countersunk rivets to -5 for consistency.

Any recommendations?

Holes

.002" over max? I think I would "Build On" with 1/8" rivets per plan, but ask Vans since it's public now. I the future, drill small and enlarge. Some of us use reamers for the final hole.

HS Forward Spar and Doublers

I used a 1/8th then reamed to final size. I'm not sure what happened, since I was very careful about drill position and clamping the workpieces together.

I am impressed with your attention to the details.
What did you use to measure your holes? Vernier Slide Calipers can have a ?read error? or tolerance as much as 2 thousandths. Digital calipers a touch better. However, measuring small holes like these can be tricky. It requires you to have the caliper perfectly perpendicular to the surface. Tough to do by hand.
There are other higher precision ways to measure more accurately so I apologize if you have the machinery and skill to use them.

I would consider a thousandths or two as a very likely error. This could be good, or bad.... holes could be a little smaller, or a little larger.

I agree with wirejock?s assessment and path.

RV701775 said:

I used a 1/8th then reamed to final size. I'm not sure what happened, since I was very careful about drill position and clamping the workpieces together.

Click to expand...

Reamers only work to final size a hole. If you want the accuracy of a reamer, drill holes slightly undersized, then ream to final size.

Also, what RPM?s is your drill motor? Style and type of drill bit?

Build on

Vans says build on.

RV701775 said:

Vans says build on.

Click to expand...

Yay! I wasted a lot of words on that one. Ha!
Here’s more....

Oblong holes are pretty common regardless. Drill speed, drill sharpness, technique, drill chuck run out, drill bit type and material, can all contribute....
I think Van’s understands that most of us don’t drill perfect holes and their designs take that into consideration.
I never heard of using a reamer until matched drilled kits came out.

Also, if you believe AC-43-1b as the Bible, or at least an educated “guide”, the only repairs allowed to any spar must come from the manufacture. That’s you!
However, I interpret this to mean the “designer” of the spar, which would be Vans.
Good on you.