Converting to a 3-piece Kayak - PART I^

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Ceegee
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Converting to a 3-piece Kayak - PART I^

Post by Ceegee » Mon Jan 11, 2010 6:32 pm

Well minus 8 degrees in my garage wasn’t exactly conducive to messing around with fibreglass, but I got most of the preparatory work towards the three-piece conversion done, so I’ll share the progress to date.

I will wait on warmer weather to undertake the major surgery of cutting the boat and glassing in the fittings (maybe in March?) which I will post then. Many thanks to all who commented, made suggestions, sent photos etc., especially Chris-UK, Richard Moss and Mike @ Rockpool.

Step 1. Determine where to place the joints. The kayak is 512cm long, and 170 cm in from bow and stern clears both hatches, and leaves adequate room for the footrest (fore) and a day hatch compartment behind the seat aft. It also means that each piece will be under 6 foot! I'm planning on locating the (male) tenons and latches on the shorter ends and the (female) mortices and catch plates on the longer mid-section.

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Step 2. Make a suitable bulkhead template. Measure the cross sections at both points and make a cardboard template that fits the LARGER of the two cross-sections. Then mark on where the mortise and tenons will go, so they fit within the smaller bulkhead perimeter. The reason is that you can then use the same pattern for both ends, and just need to trim the bulkheads to the hull cross section. At the same time I marked the (approximate) latch positions to make sure there is sufficient clearance for glassing in between the mortise/tenons.

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Step 3. Make a plug for a suitable tenon. You need to choose a simple shape which will mate cleanly but firmly. I chose a tapered fish paste jar with no lips, overhangs, decorations etc. This was waxed and coated with PVA release agent, and filled with casting resin. I floated a stubby candle in the centre to save on resin and cut down on heat build-up during curing (the wax melts and can be poured out once “green” leaving a hollow centre. Fill the form brim-full and top with a sheet of wax/PVA’d glass to get a perfectly flat base. Once cured fill any cracks/bubbles or pin-pricks with filler, and clean-up with 400/600 grit paper. Make three.

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Step 4. Assemble your mould. Trace the bulkhead onto the underside of a piece of float glass with a marker pen. Glue your (three) tenons in position with silicone, mask off the laminating area with brown parcel tape – leaving an extra 2-3 cm all round for trimming, and wax and coat with PVA release. Use the template to mark and cut out your chopped strand matt (CSM). I used four layers of 300g/m2 per bulkhead, i.e. x 4 = 16 in total. Cut separate pieces for the mortise/tenons (circles) and cut “flower petals” to ensure good fits around the complex shapes. For heavy-duty use or on a bigger boat, I’d suggest 5 or even 6 CSM layers.

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Step 5. Colour your gel coat with pigment to match the boat and apply a decent layer. I mixed about 250g per bulkhead giving 0.5-1mm thickness. Hold your glass to the light to identify thin patches. Pay attention to where the tenon plugs join the glass to ensure a decent bead with no pin holes or bubbles. A tooling gel coat (tougher, for mould making) might be a good idea. Allow to tack-off.

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Step 6. Start to laminate on top of the tacked gel coat. Paint a layer of catalysed polyester resin onto the gel coat, add the first CSM, wet-out the tenon “caps” and stipple the sides onto the gel coat well. Accurate cutting out and trimming of the CSM gives a tight fit which helps to accommodate the sharp radii. I catalysed about 450g of resin for each bulkhead. Work quickly and stipple well – you will need a stiff brush to stipple as the shape is too small and complex to use a wetting-out roller.

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Step 7. Allow the bulkhead to CURE COMPLETELY on the glass. I lifted the first one whilst green, and it DEFORMED. I tossed it and made a new one and left it 36 hours on the mould, it remained perfectly flat!!! Clean up with a bit of 400/600 grit paper, mask the edges with parcel tape and wax and PVA again. Repeat Steps 5 & 6 to give a male bulkhead to the female already made. Again, allow to fully cure. Split the two, remove the parcel tape and trim to the tape line with a mini-grinder and wash. You now have a matching pair of bulkheads. Make a second pair, either by laminating a mate for each of the existing, or by starting from scratch again.

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Step 8. Make a plug for the latch recesses. I made an MDF plug to make five at a time I’m using five per end – one on each hull chine and one on the deck centre line. This seems fairly standard as long as they are evenly spaced around the circumference – the obvious location to avoid is the keel line. At £12+VAT a pop they are not cheap, and six seems excessive. The latches I’m using are the same as Rockpool, from http://www.protex.com. The recess is deep enough for the latch to be flush with the deck. In this case the latch is 20mm high when closed, and the deck is ~5mm thick so the recesses are 16mm deep. I allowed 2mm per side and 5mm per end clearance. The plug then was given a coat of polyester resin to seal the MDF and waxed and PVA’d.

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Step 9. Laminate the latch recess boxes. I used a pigmented gel coat of 1mm + to match the boat colour (black in this case) and 4 layers of 300g/m2 CSM on the base (where the screws will go) and two on the sides and flanges. This will be added to when the recesses are glassed into the deck underside and rear of the bulkheads. I laminated them as a group, and had to really stipple well to avoid bubbles and voids. I’ll probably make an additional set and choose the ten best as a means of QC. The set was cut into individual pairs with a mini grinder, and the flanges trimmed and roughened on a grinding wheel.

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The components are now assembled, comprising two each pairs of male/female bulkheads and ten sets of two-piece latch recesses, together with latches, catch plates and s/steel screws, washers and lock nuts.

Cost to date:

1 kg gel coat (~£7), 2.5 kg polyester resin (£10) and 4m2 of CSM (1.2 kg - £6) plus ~£12 for sundry bits n’ bobs (acetone, pigment, wax, PVA etc) = £ 35. The latches cost £15 each incl. catch plate and VAT plus shipping, and another £1.00 for 5 each nuts, bolts and washers – so the total material cost is likely to come in at around £250. I suppose I’ve invested about 10 hours time over several evenings so far, with the same to go.

Coming soon…

Jigging and cutting the boat, trimming and glassing in the bulkheads and latch recesses, and fitting the latches.

Cheers

Steve
Cheers,
Steve C. G.

das boot
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Re: Converting to a 3-piece Kayak - PART I

Post by das boot » Mon Jan 11, 2010 6:56 pm

hi steve, great to see you are on the way for your three piece qaanaaq.


thank you for posting progress, looking forward to see some more.

martin

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MikeB
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Re: Converting to a 3-piece Kayak - PART I

Post by MikeB » Mon Jan 11, 2010 10:07 pm

Wow!

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chris-uk
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Re: Converting to a 3-piece Kayak - PART I

Post by chris-uk » Tue Jan 12, 2010 8:48 am

That is AMAZING Steve!!! What a job!!! I hope the rest goes as well as this lot clearly has, and I'm certainly looking forward to the rest of the story unfolding. Outstanding so far :-)

Chris

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MePower
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Re: Converting to a 3-piece Kayak - PART I

Post by MePower » Tue Jan 12, 2010 2:54 pm

Nice neat job! Can you post a video of you slicing your kayak into 3? In a sick way that would be something great to watch!

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Ceegee
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Re: Converting to a 3-piece Kayak - PART I

Post by Ceegee » Tue Jan 12, 2010 3:37 pm

Will do...

Splashed out on one of these, so should be a neat, precision job!!! (I hope)

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Steve
Cheers,
Steve C. G.

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MikeB
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Re: Converting to a 3-piece Kayak - PART I

Post by MikeB » Tue Jan 12, 2010 3:47 pm

MePower wrote:Nice neat job! Can you post a video of you slicing your kayak into 3? In a sick way that would be something great to watch!
Ah yes - this is going to be the good bit - - -

What strategy are you using Steve? I presume you'll be cutting in fron of the front, and behind the rear existing b/heads? Which will (I guess) retain the structural integrity of the central part of the boat. What happens then? Do you remove the existing b/heads and repalce them with the ones you fabricated? Or bond the new ones to the existing one? And then bond the partner b/head into the bow / stern sections while hoping the (unsupported?) hull sections retain their correct line.

Out of interest, do you know how Rockpool and Valley deal with this when they do it? I suppose if the hull sections were secured in some form of cradle or hull-form that would do it.

I have to say I am in awe of what you're doing!

Mike.

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Ceegee
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Re: Converting to a 3-piece Kayak - PART I

Post by Ceegee » Tue Jan 12, 2010 7:33 pm

Well Mike,

The plan is to get the boat level in length and width on trusses, generously mask the cutting area with 2" masking tape, and use a laser plumb (the kind for projecting tiling lines on walls) to project and trace the cutting line. Because it is a hard chine boat I was thinking of glueing fences along each cut line with thermosetting glue for the Dremel circular saw to follow.

Then the cuts, a chine at a time and then plenty of duct tape over each cut before the next. Finally sever the ends along the gunwale seams and keel whilst a helper supports the end!

Then place the cut section with the existing bulkhead (say for instance the footrest end) upright on a sheet of paper and carefully trace the outline. The existing bulkhead will preserve the cross-section. Then reduce the tracing by the thickness of the the deck/hull (say 3-5 mm, but I'll measure this at the time) and trim the new bulkhead pairs to the same.

Cut out old bulkhead with the Dremel and clean up. Up-end the section onto the bulkhead lying on flat ground and tack in place with duct tape, then reach through cockpit and glass in with strips of 2" CSM. Sounds complicated but the photos will explain when the time comes! I'LL MAKE A VIDEO!

No idea how Rockpool, Valley etc. do it, but this seems to make sense and I don't want to pester them. All I know is they build a finished boat (presumably with no or only temporary foam bulkheads) then cut it up.

Steve
Cheers,
Steve C. G.

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MePower
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Re: Converting to a 3-piece Kayak - PART I

Post by MePower » Tue Jan 12, 2010 8:39 pm

Ceegee wrote: I'LL MAKE A VIDEO!
Steve
Great idea Steve, look forward to it!

Ligan
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Re: Converting to a 3-piece Kayak - PART I

Post by Ligan » Tue Jan 12, 2010 10:08 pm

I may be to late with this, I had a three piece made by valley and they very kindly told me how they do the cutting bit.
They mate the bulkheads up with a 2mm gap between them and then glass the double bulkhead inside by reaching in from the hatch and cockpit. Once its gone off they cut the boat up by hand with a hack saw blade which nicely slips into the 2mm gap between the two bulkheads. To make life easier they make a small hole with the hacksaw blade and line the bulkheads upon that at the start.

good luck and looking foward to the video

pete

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Ceegee
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Re: Converting to a 3-piece Kayak - PART I

Post by Ceegee » Wed Jan 13, 2010 1:55 pm

sinkingpete wrote:I may be to late with this... mate the bulkheads up with a 2mm gap between them and then glass the double bulkhead inside... cut the boat up by hand with a hack saw blade which nicely slips into the 2mm gap between the two bulkheads
Not at all, cutting is still a few weeks in the future good idea. I could just tack the two halves together with a little double-sided tape, trim and replace the old bulkhead - then seperate as you suggest. Might be an idea to run a bead of silicone along the outer edge of the mating faces go stop them getting stuck together by resin flowing in. The sawblade should cut through that no problem.

Ta,

Steve
Cheers,
Steve C. G.

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Jim
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Re: Converting to a 3-piece Kayak - PART I

Post by Jim » Thu Jan 14, 2010 2:37 pm

For a good finish to the cut use your dremel at high speed and try and use a diamond disc rather than toothed. Not sure about kayak builders but boat builders tend to use an air powered cut off tool with a diamond disk - the dremel at high speed should be a good substitute. As long as you can avoid wobbling you shouldn't need to sand the finished edge, but it is worth smearing some resin around to seal the 'end-grain' as it were.

To make absolutely sure the bulkheads won't get stuck together if resin gets past your silicone dam you could wax the bulkheads or paint with PVA release agent (I've found hard wax to be slicker, will need to build up a few coats to be certain but not as many as for a new mould).

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Ceegee
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Re: Converting to a 3-piece Kayak - PART I

Post by Ceegee » Thu Jan 14, 2010 4:18 pm

Jim wrote:1) use your dremel at high speed and try and use a diamond disc rather than toothed...

2) ...you could wax the bulkheads or paint with PVA release agent
All good advice, thanks Jim.

1) Dremels have a pretty high RPM (30,000+?). I'm not sure if the circular saw attachment accepts the cutting disks. The other thing to use would be this, but I'd rather save £80 at this stage. The Dremel cutting disks do the business on GRP (from experience) but the saw attachment has the advantage that the housing can be run along a fence for an absolutely straight cut, and the toothed blade cut is under 2mm wide. I'll practice on some GRP sheeting beforehand!!!

2) The more wax & PVA the better in my book, so will do, but was planning on spreading a thin silicone bead to maybe 1" wide around the edges and clamping until set. That should provide a very resistant dam.

Will seal the cut and/or fillet any gap between bulkhead & deck with flowcoat and sand back.

Thanks

Steve
Cheers,
Steve C. G.

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