When to drill wing side of flap hinge??

I finished the wings last month including riveting the flap brace as directed in the plans.

Now I'm finishing the flaps and wondering if I should have left the flap brace off the wing in order to drill the flap hinge. I can't figure out when I'm supposed to drill the wing side of the flap hinge.

I noticed in several logs that some people (partially) built the flaps BEFORE their wings.

I'm just a guy trying to follow directions.

Flap hinge

The manual has thos step in sequence. It's a tricky step because you can't hold the flap brace and skin together with clekos.
I used the fat rivet method.
Partially squeeze rivets and insert them into every other hole to hold the flap brace and skin together. Then just clamp the flap and hinge in place, drill the open holes, cleko, remove the rivets, drill the open holes, done.

Thanks, Larry. But I'm not sure I understood your response. The flap brace is riveted to the rear wing spar web, but unriveted to the rear spar flange and bottom wing skin.

I've already dimpled the bottom skin and countersunk the rear wing spar. Just not sure how and when to add the wing-side hinge holes to the equation. Seems odd to not match drill through dimples.

Wing hinge

I would consider this a gotcha in the plans. I struggled with this as well.

From the manual:

INSTALLING THE FLAP BRACE AND AILERON GAP FAIRINGS
Drill, deburr, dimple where required, and rivet the W-721 flap brace (DWG 14A) to the rear spar.

Notice it says to rivet to the rear spar but doesn't mention riveting to the skin. The plans call for a 1/4 inch gap between the aileron and the flap. I don't see how you could get the proper distance without hanging the aileron before you drill the hinge to the wing.

wirejock said:

The manual has thos step in sequence. It's a tricky step because you can't hold the flap brace and skin together with clekos.
I used the fat rivet method.
Partially squeeze rivets and insert them into every other hole to hold the flap brace and skin together. Then just clamp the flap and hinge in place, drill the open holes, cleko, remove the rivets, drill the open holes, done.

Click to expand...

Flap hinge

Let me try again. Read my disclaimer please.

You should have a flap brace riveted to the rear spar web but the other edge is a row of holes that match a row along the aft edge of the bottom skin. Flap brace holes should be countersinked. Wing aft holes should be dimpled.
You also have a flap with 1/2 a hinge riveted in place.
Heres how you drill the 2nd half of the hinge.
Aileron is in place. Aileron bellcrank alignment jig is in place. I also had an alignment device on the end of the wing to make sure the aileron was exactly where it should be.
Take a handfull of long 426 #3 rivets. Use a pair of needle nose pliers to hold one. Squeeze it just enough so it fits tight in one of the flap brace/skin holes. Insert it so the shop end of the rivet is flush with the flap brace side. Repeat for every other hole. Every one squeezes different so it takes some time.
Now you have a flap brace lined up with the skin holes and the surface where the hinge will be clamped in place is flat with no cleko points sticking out. The long rivets should be sticking out on the wing skin side. You need them sticking out so you can pull them later.
Draw a center line on the hinge. Some, including me, find the need to use wider hinge to maintain ED.
Install the half hinge on the flap with the pin.
Use clamps to clamp the hinge to the wing. Use a piece of 1/4" stock to keep the flap/ aileron gap consistent. When you have the centerline perfect in the remaining holes (no fat rivets in them), tighten the clamps and triple check everything including alignment to the aileron and consistent edge along both aileron and flap.
Make a backing stick out of something with an end the same angle as the side where the drill bit will exit.
Get a helper to hold the backing stick behind the hole and match drill through the dimpled holes in the skin (the ones with no fat rivets). Insert clekos as you go. Don't drill in a row. Skip around so the part is supported by clekos.
Now go back and use a plier to remove the fat rivets ome at a time.
Have the helper hold the block, drill and cleko.
Sounds more difficult than it is.
If this is not the answer, sorry. Maybe I still don't understand the step you're working.

Thanks, Larry. I left this step and got involved with my QB fuse arrival and riveting bottom skins. Now I'm back and your instructions make perfect sense.

I appreciate the time you took to spell it out.