Thanks Presto. I too sat through a couple semesters of fluid dynamics. Bernoulli was my good friend (or perhaps not!!
) I knew the why, but was looking for advice on the best method to correct it.
Based on some inspiration from Centmichsailor's project, I decided to move forward.
I originally had about 1/4" lateral movement of the boards in both trunks. Looking down the trunk well with the board in place, the 1/8" gap on each side was clearly visible. Here's a pick looking from the bottom side before correcting.
I considered both closed-cell vinyl foam (3mm = ~1/8") and the fuzzy side of the Velcro (3M/Scotch RF7760; comes in white or black; 15' roll was about $5). I got them at Menards, but any hardware store should carry it. I was afraid the higher friction of the vinyl/rubber might cause board insertion/removal issues or get peeled off by the board, so I went with the velcro (fuzzy side).
I cut it into strips about 90% the length of the trunk. Application was tricky as the adhesive is very
sticky/tenacious, and getting both the proper distance from the bottom (I decided on about 1/8") and the correct angle were a challenge.
Board fit is now "perfect" - its still easy to insert/remove, with a nice snug fit with no lateral movement and very little area for water to come up. Unfortunately no wind is forecasted this weekend, so I can't test it...
Only potential issue with the tighter fit that I can imagine is that it might induce some drag if the overall boat has any toe-in/out issues. Last time I measured the hull, it was within 1/8" on flat water, but I'll probably be more conscientious about raising the windward board when sailing flat.
Here are a few photos after the fix.
Looking down the trunk
Bottom view board-out
Bottom - board-in
I placed 4 pieces each just below the top edge of the trunk at front/rear and sides similar to centmichsailors project. This should prevent excess movement at the top and help limit some abrasion seen in this area.
Hope this is helpful. I'll let you know how things go...