How to build a seakayak /PART 4
Fourth part of our tutorial on how to build a seakayak Bette 500 HV, using plywood and epoxy resin , with the so called “stitch and glue” system
gluing the hull panels and removing the cable ties
time required:
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panels gluing with resin: 6 hours
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removing the cable ties: 1 hour
we have to check that the hull is straight before starting to glue the assembled panels; a visual control is fine, align the eye between bow and stern and control (it may be useful to mark the centerline on the bulkheads to better check it, but it’s not mandatory)
-straighten the bow (or the stern) : it’s quite frequent that panels are not perfectly aligned on bow or stern, but they slightly zigzag; we’ll correct this issue simply forcing the panels on the bow line among two stiff battens: take two stiff battens 70 cm long and let’s make a sort of clamp with them as shown in the picture, we may stick them in position with adhesive paper and then tighten them with iron wire or clamps until we force the hull panels in the proper alignment; be careful not to glue the battens accidentally to the hull, use plastic film to wrap them if you fear glue may squeeze outside and glue them ; if necessary do the same operation on the stern too with two shorter battens;
gluing the hull panels : there are some possible approaches, I decide to go for this one:
- start with a first layer of liquid (or slightly thickened with silica) epoxy resin; varnish the inner of hull panels and the bulkheads (the whole surfaces) using a small paint roller, try not to resin near the cable ties, and on the other side try to varnish well the panels’ joints , if resin drops on the outside, remove it when it’s liquid; now let’s wait for the resin to dry ; obviously we’ll glue also the joints among bulkheads and hull;
- removing the cable ties: carve them deeply with a sharp blade (dispose the blade when it’s not enough sharp) and remove them; several will be glued, so remove them cutting them in to pieces; a small screwdriver may help you; if you find that in some zones panels’ joints are not glued don’t remove cable ties, it is mandatory that panels don’t move, so we’ll do another bonding with thickened epoxy and then we’ll remove the ties;
- fast sanding on the inner joints , remove resin drops or patches if present; now we’ll proceed with liquid joinery, that’s to say a small radius of thickned epoxy that will stiffen the panels’ joints; we’ll work with about 150 ml of epoxy each time, thickened with silica and cellulose microfibres in a disposable plastic cup until the resin has the density of a marmalade or a mayonnaise; we’ll use this resin to do resin radiuses among the panels;
- “pastry chef” trick: I used small triangular plastic bags which are used by pastry chef to fill the sweeties with cream , they’re perfect to fill the joints with the proper quantity of resin for a radiused joint; mix the resin in a small plastic cup, add silica and microfibres until the density is ok, then pour it in our little triangular bag, cut a small corner of the bag’s edge and squeeze the resin on the panels joints ; now coes the funny and dlicate part of the work: we have to work the resin with fingers (wear latex gloves, of course) or small washers or other circular shapes to give the proper shape to the thickened epoxy and make a neat clean and smooth epoxy radius in all the joints among panels ; take all the time you need to do this operation, don’t be in a hurry; as a matter of fact this is one of the operations where using slow or very slow hardener for your epoxy marks a big difference ! The smoother and cleaner you’ll do the radiuses, the easier will be next operations; work can be done dividing the hull in 5 sections using the bulkheads as limits, so mix the resin, squeeze on all the joints between two bulkheads, work the resin properly , and than pass to another section of the hull ;
these our our best friends for resin operations: latex gloves (epoxy is a big mess to clean, so make all efforts to work as clean as possible), small plastic disposable cups, disposable syringes to mix accuraltely small amounts of resin and hardener, and most of all tha “pastry chef bag” our secret weapon to achieve smooth and clean radius joints
- bow and stern lines: we don’t have enough room to work in these areas, so we’ll basically set up a cup of thickened resin which have a sligthly lower density, so that we can do a decent radius simply letting the resin flow on the bow and stern joints , from the sheerline down to to the centerline
at the end of these operations we’ll have a hull with a good stiffness