Tom,
Have you looked at an Arc Teryx brand backpack lately? They have an interesting "watertight" zipper technique that they are putting on some, if not all, of their packs (e.g., Bora 60 LT). It appears to be possible to recreate what they did by taking a YKK zipper, gluing a narrow strip (1 - 2") of PVC or similar material (maybe thicker/softer) across the zipper, i.e., from tape to tape. Then taking a sharp razor, virtually zero kerf, and slitting the coverlet down the middle. The idea is extremely simple. The soft coverlet halves butt against each other to form a gasket. The easiest way to understand it, is to look at one. I'm sure that you'll have no problem finding a gearshop that carries ArcTeryx in the land of milk and honey (CO). This may be an oversimplification, but it's worth looking at.

steve

BTW, the boxer is gone. That makes more room in the garage for toys and building!
: Good points. Even though the folding skins are not as tight
: fitting as the non-folders, the speed seems unaffected, and
: the added skin concave may even add to stability. PVC should
: perform even better.

: Let me know what you find.

: I've been testing various tapes for it's adhesion to PVC. I've
: found a clear 2" waterproof polypropylene ? tape that sticks well
: to PVC after the area to be taped is wiped lightly with MEK to
: "dull" the PVC finish. I'm planning to tape over the YKK
: non-waterproof plastic marine zippers I bought to see if
: it's a good home remedy. I may or may not use a flap
: if this works ok.

: Glad it worked out ok. Inwales add some longitudinal stability,
: but add a lot to the lateral stability.

: I hope you'll post some picks of your's and Mike's folders
: from Delmarva.

: Tom