Test fit of wing skins
The wing skins were test fit, including the fuel tank and outer leading edge skins. Some mismatches evident. I will be communicating with TAF do determine rational criteria for 1) rejecting a skin and requesting a replacement, or 2) elongating holes and ignoring the mismatch, or 3) upsizing rivets to absorb the mismatch
As I see it, I think it prudent to request a replacement root skin 4. This could be shipped flat with the fuselage kit. As for the fuel tank skins, the holes affected by mismatch are not believed to be particularly structural, so some elongation (even after upsizing) could be tolerated. Will check with TAF. As for the bottom root skins, the mismatch with the main spar front-facing flange is also beieved not to be structural, so elongation of the 4mm holes is tolerable. Due to the double layer of the flange, upsizing the inboard holes to 4.8mm is not an option, unless I can successfully counterbore (I have a 5/16" with 4mm guide). Upsizing the outboard holes to 4.8mm is a possibility.
More concerning is the mismatch of the left hand root bottom skin holes with the rear facing main spar flange. These holes are definately structural in nature. Will check with TAF as to whether any elongation is tolerable.
Will also look into possibility of obtaining a right angle chuck to permit possible counterboring the double flange holes to a larger size allowing 4.8mm rivets to be possibly accommodated.

Both skins 5 (top tip skins) good - match each other and front spar

RH fuel tank and outer leading edge

RH fuel tank and outer leading edge quite good rivet match when stand-alone (within 0.2mm)

LH fuel tank and outer leading edge

LH fuel tank and outer leading edge - very good rivet match when stand alone

RH fuel tank to outer leading edge when clecoed - some mismatch probably requiring upsizing to 4mm only on top side, bottom side good

RH fuel tank to outer leading edge - reduction in mismatch with some forcing

RH fuel tank and outer leading edge - perfect fit on bottom edge

RH fuel tank and outer leading edge - with minor pressure at the outer edge of fuel tank good rivet matching achieved everywhere except for where rivet line jumps from front to rear main spar flange, and the mismatch persists for about 10 rivets

RH fuel tank and outer leading edge - worst case mismatch of about 0.7mm. Upsizing to 4.8mm rivets seems practical

LH fuel tank and outer leading edge - perfect fit on bottom edge

LH fuel tank and outer leading edge - with minor pressure at the outer edge of fuel tank good rivet matching achieved

LH fuel tank to outer leading edge when clecoed - some mismatch probably requiring upsizing to 4mm only on top side, bottom side good

LH fuel tank and outer leading edge - worst case mismatch of about 1-1.2mm. Upsizing to 4.8mm rivets seems a tolerable solution

LH fuel tank and outer leading edge - worst case mismatch near transition from front to rear spar flange - not quite as bad as it appears

LH bottom root skin

LH bottom root skin - Some mismatch (not more than 0.3mm) along the front flange holes (bottom) which appears to reach a maximum at the middle if the holes match the spar at the end. Also mismatch with the rear facing spar flange holes (top). This is believed to be not so important, and other builders elongate.

RH bottom root skin - good hole match everywhere except about a 0.7mm mismatch with the rear facing main spar flange holes. This is believed to be not so important, and other builders elongate.

The skin 4 (top root skin) holes match for most of the length, but for the most outboard 40cm a mismatch appears, as if one of the skins has slipped while being machined. This error affects matching with the front flange of the main spar and rib 8 skin holes and the rivetted connection with the tip skin 5.

Bad skin 4 hole mismatch with rear main spar flange - upsizing to 4.8mm would be practical but would it be also possible to absorb fuel tank mismatch?

Bad skin 4 rivetted connection with the tip skin 5 - 1mm hole mismatch. At least a 4mm upsizing would be required, and this would be marginal
This post is from Adam Dickson