Three-piece kayaks^

[Ceegee]

Christmas is coming, so I'll have to slope off to the garage to avoid the in-laws etc. I'm planning major surgery, which involves converting one of our greenland boats to a 3-piece


I prefer the Rockpool (latch) solution to the Valley (bolts), and great strength is not required as we don't take our rolling boats out in big seas. Mike at Rockpool has already very kindly pointed me to his supplier of latches, so I'm OK there.

Trouble is, Anglsey is a long way go pop in and check on how its done, and chances of him converting a boat at any one time are slim. I'm quite confident about the cutting and laying up / glassing in of the bulkheads with matching rebates, but I'm curious about the exact details of the latch recess boxes.

Derrick Mayoleth has a suitable picture on his blog, but as I said, an open/closed of both sides would help.


If anyone has any close up photos of the latches, in OPEN and CLOSED position, plus a pic of the underside (inside) view of the latch box they can post, I'd be very grateful. Or PM me and I'll send an e-mail address.

Cheers

Steve

[Graham T]

on Nigel Dennis's three piece boats there is a mortice and tenon affair whic is a tight fit and takes the loads, the latches are only to hold the sections together.
Will you latches take the necassary twisting which may take place after all with a kayak such as this is rolling is obligatory ?

Just wondering, anyway it sounds like it should keep you occupied for boxing day no worries

[delphinidae]

The three piece boats start out as a single piece boat, but small plugs are put inside the hull & deck moulds in order to make the recesses (the male & female bulkheads are then glassed into the completed boat > clips & hooks are bolted on and closed > the deck/hull is carefully cut until you have a three piece boat > a piece of ABS is glued to the female bulkhead in order to make the joins flush).

Making the recesses on a boat that hasn't had them moulded in at the beginning would require a different technique.

[Ceegee]

Cutting the boat is easy - just beyond the existing bulkheads (which I'll then remove). Will set boat up in cradle, plumb it and was planning to use a laser level to tape off a perpendicular cut line, then support the boat on foam and use a mini cutting wheel for a neat cut.

Ditto making the new bulkheads (with mortice & tennon moulded in). I used shapers (kid's sandcastle starfish molds - a bit like Rockpool's 3 shells) glued on a glass sheet to make my male plug on which to laminate the one side of the bulkhead pair, then laminated the opposing bulkhead off the first. The "play" is the thickness of the PVA release film, i.e. minimal.

For the latch recesses I'm going to have to cut slots in the deck/hull and bulkheads. Was planning to make the boxes laminated onto a shaper, then glass these into the undersides of the previously cut slots. None of this should be a problem.

I was just interested in the actual tolerances used on the latches and bars, and how strongly these are glassed/screwed into the hull. A picture speaks a thousand words.

Thanks & keep the comments coming, Steve

[Ceegee]

Like this!

[Graham T]

Might be worth asking Nigel Dennis or Rockpool for a little input in this regard. My understanding as before is that the latches serve no real purpose other than to keep the parts from becoming detached.
That being the case there would not be any twisting loads imparted only tension through the latch. Do the latches you are planning to use have some adjustment for tension ?
I look foward to seeing how this turns out hope it all goes smoothly

[Ceegee]

1. Might be worth asking Nigel Dennis or Rockpool for a little input in this regard
2. My understanding as before is that the latches serve no real purpose other than to keep the parts from becoming detached.
3. That being the case there would not be any twisting loads imparted only tension through the latch.
4. Do the latches you are planning to use have some adjustment for tension ?
5. I look foward to seeing how this turns out hope it all goes smoothly

1. Mike at Rockpool has been a great help already - I'm pretty sure I'm 95% there on the concept/technology.
2. Correct
3. Well tensional loads from waves passing under the boat (pulling on the bottom latches as the bow rises), or torsional loads from rolling, but correct, they are minimal.
4. Yes, they're adjustable - same latches Rockpool uses (not cheap - €10 each and 10 per boat)
5. So do I !!! Thanks. I was just hoping someone with such a boat might post a close up pic of of the open/closed latch assembly.

Cheers

Steve

[chris-uk]

I have these latches on an NDK boat, but they aren't recessed. Would you like a picture of them?

Chris

[Ceegee]

I have these latches on an NDK boat, but they aren't recessed. Would you like a picture of them?

Chris

Yes please - I've PM'd you. Thanks

[delphinidae]

I'll see what I can do tomorrow morning; it's too dark to take photographs at the moment.

What I can tell you without looking/sans photographs is that the latches/hooks are bolted to the boat using five bolts (three for the latch & two for the hook) and are bedded* like any other fitting. There is wide range of adjustment available via the screw-in hook on the latch, so placement need not be critical. However, one turn of the (latch) hook can often make a latch too tight to open without the use of some kind of lever.

*(AFAIK, the latches/hooks are not made from marine/A4/316 stainless steel and they will rust/stain a bit in places [mine have])