: This past weekend, we managed to crack the 4mm marine ply hull on my wife's
: new VOLKSKAYAK - I launched her stern-first by lifting the bow - when I
: let go, the bow section came down on a sharp rock. The resulting crack is
: L-shaped, about 6 inches long with a 1 inch spur at 90 degrees to that. It
: has noticeably displaced the panel to the inside. It's bad enough to let
: in about a gallon of water enter the forward compartment on a thirty
: minute paddle.

: I'd prefer not to place a FG tape patch on the outside for cosmetic reasons -
: thinking of sanding down the inside ridge, applying two or three
: overlapping layers of FG tape, then sanding the outside indentation (it's
: pretty shallow) and filling it with a epoxy-silica mix. If anyone has a
: better approach, or sees any major problem with my idea, suggestions would
: be much appreciated.

Hi,
Assuming the Volkskayak is a taped seam hull, putting any glass on the outside would show badly. Your idea of glass patching the inside is the most common method I've seen similar 'events'. Can you get direct access to the area inside? If you can, could you press the point of the crack back to closer to its original level before patching it?
One method I saw was to drill a small hole as big as the stitching holes in the corner of the piece pushed in, in your case about 1/4" in from the corner, thread high tensile wire through the hole and through a block (larger than the area of the crack) inside. Fasten the wire to the inside block. Put a flat solid board against the outside (hole for wire in the middle) of the hull. Fasten the wire to a third block so it's spaced a bit from the block against the hull. Use wedges between the two outside blocks to pull the inner block outward and the corner of the crack should close to its original level.
The blocks against the hull can be shaped to account for any panel curvature.
If you can get thin epoxy into the crack just before this, that should seal the broken edges and glue them together. Oh yeah, use plastic between the blocks and the hull.
If it closes fully, the amount of filling is minimal on the outside. Glass patch the inside as you planned.

It's easier to do than explain. But it's a good 'away from shop' technique.

Hope this helps.

Mike Savage
South West Cork