Plyak12 build by gbgb

[gbgb]

Starting a thread for the build of my Plyak.
Plywood purchased - 4mm marine Okume for the body and 6mm birch for frames and sole
"Lofting" completed - total 4 hours

[gbgb]

Oops' I just saw that there is a special section for building progress threads.
If an admin can move this thread to the correct place then great - I will wait for some days and see if this happens.
If not, I will simply stop writing here and start at the correct place

[gbgb]

All plywood panels cut - 2 hours
Still did not cut the cockpit opening as I am considering making it smaller than the plans, probably at the line of the footrests. The main use of this kayak will be at sea, and although I do not plan going out on very choppy days, it is rare that the sea is flat as a lake, so a slightly longer foredeck may help.
I guess it can always be enlarged at a later stage (less convenient but possible).

All panels joined using FG splice, cleats glued to frames - 1.5 hours

[gbgb]

Checked the FG butt joints. When I flipped the first panel the butt connection snapped open. Although the other panels did not, it looked like the joints were not strong enough.
If I remember correctly from past experience it should be enough to apply the FG on one side, but this was many years ago so maybe I am wrong. Maybe it is due to the fact the these panels are very thin compared to what I did in the past, and probably the fact that I did not thicken the epoxy for the butt connection (not sure if it would have helped).
Anyhow, simply made a FG splice on the other side as well.

It was a very hot day and the epoxy cured fast, so I managed to squeze in also the lamination of the shear clamp to the side panels, so tomorrow will probably be stitching day.

[narfi]

I am curious as to what failed. Was it the epoxy? (that would be troubling....) or did it peel up a layer of the plywood? (also seems a bit weird)

[gbgb]

It was the epoxy, or probably more correctly lack of epoxy. No plywood was peeled - the FG side remained perfectly well, it simply disconnected at the joint and remained hanging on the FG splice.
What I think is that the joint did not get enough epoxy. Although I "paintetd" the edges, let it absorb and then applied again, probably most of it got absorbed and when the pieces were pressed together almost no material remained between them. The hot weather also made it very runny. This is why I think that thickening it would have helped. I think that would have ensured that enough material remains in the joint.

[pee wee]

Yes, to make epoxy glue you need a filler like wood flour, adjust the amount of filler according to the need- usually a ketchup/catsup consistency but sometimes it has to be thicker. Check under How To's at the top of the page on this site for more detail on making and using epoxy glue. Use enough to squeeze out a little.

[youtube]https://youtu.be/L2K66a3GG5o[/youtube]

[gbgb]

Yes, I begin to remember the work procedures. It's been about 15 years since my last boat build.

Today marked and drilled the holes for stitching and stitched the boat.
Also marked and cut the cockpit opening - As already said, I decided to make it smaller than the plans - ended up making it about 30cm (~12") shorter.
The only slight error is a 5mm offset of the seat back frame - it is not in-line with the cockpit cutout. Noticed it only after I put on the deck and stitched it - not a real problem - I will correct it when I make the permanent installation of the frames.
4 hours

[gbgb]

Spot welded the hull. 1 hour.
Before applying the epoxy I made final adjustments to the stitches. Inserted 4mm dowels to maintain a uniform spacing as possible.
I did the spot welding in the morning. Thought of removing the stitches in the evening and complete the seams, but although the epoxy cured it felt not as hard as fully cured (compared it to epoxy that was applied yesterday), so I decided to give it some more time until tomorrow.
It seems that this epoxy takes more time than epoxies I used in the past to fully harden. This could also be the reason that the butt joint failed the other day - I put stress on the joint before full hardening. From now on I will give 24 hours for joints under stress - basically these are only the seams. There will be no problem when doing fillets or wetting the FG .

Meanwhile I am having some thoughts about the sole. Since I could not find 6mm Okume, I am using for the frames and the sole birch plywood, which is ~30% heavier. No problem for the frames, since it is strong and the frames are rather small, so weight difference is of less concern. But the sole is large and weighs almost 4kg (~8 lbs) - this is heavy. Trying to figure out how I can reduce this weight by at least 1kg (which will still be slightly more than an Okume sole) without losing strength. If it will not be a simple solution I will leave it as is.

[narfi]

could you do a foam or honeycomb sole? (not sure what materials you have access to)