Chapter 25 - Section 7

Mismatch Treatment


One major mismatch is between the wing / center section spar match line. Though it is common in the building process, most of the builders were able to make a nice transition with foam / glass and micro. The mismatch is the result of our wing-to-spar alignment process in Chapter 19 - Section 12. Here's a picture of my mismatch.  


After trimming and re-shaping the Plans Wing / Center Section Spar Seal (SEAL) (Chapter 24 - Section 10), I pencil marked the end points for a straight line seam on the wing and fuselage surface respectively. These marks basically line up the two aft faces of the hard points on the center section spar. These marks will be used to draw out the cut line of the seam later on (explained later).





Since I have a gap (~1/16" to 1/8") between the center section spar and remaining overhang of the SEAL, I decided to use 2 layers of BID to bridge over it instead of adding extra support foam. In addition, I added 2 more BID layers that cover the spar over the gap. Totaling 4 BID of overhang from the spar to the cutline and 3 BID (1 BID is from the original SEAL) of overhang from the wing root to the cut line. Then I peel plied and allowed to cure.













Once cured, I added microed over the glassed areas (pre-fill).











After sanding, I lined up the cut line markings (as discussed above) with a straight edge and put a pencil line on the micro. You may have to look closely to see the pencil line. There are no more bumps and uneven surfaces.















Using my FEIN tool and blade, I cut and sanded a fine line through the micro and glass. The thickness of the line is a hair under 1/16" such that I can really straighten it up (only if I want to later). Here's the result!  Now doesn't that look better?










Seam Integrity

One of the concerns with a perfect seam at the wing root is that they tends to get chipped when installing and removing the wings. A friend (Noe), offered some advice and help to strengthen my wing root seams. Here's what we did:


We took a nice flat aluminum sheet/strip (~.030") and applied grease on both surfaces. Then we slipped the sheet between the seems and secure the aluminum sheet/strips in place with masking tapes. You do not want them to move during the flox application and curing period. Then I packed a slight fillet of wet flox along both edges and allow to cure. After cure, I popped the sheet/strip off and carefully sand the fillet flush with the surface.








Then I removed the wings and filled the inner edges with wet flox and peel plied.


Now, my edges are straight and strong.









Here's a picture of the seam after sand and primed.