by Bob Weir ( email@example.com)
This is a journal describing the construction of a sea kayak in my basement. The original text was written at intervals during the five month project, but what you are reading here is the result of substantial editing after the fact.
You won't learn how to build a kayak by reading this, and you might not understand much without being familiar with the references (listed below) or at least looking over photographs of this or a similar project. My main purpose is to document the otherwise undocumented: I mean to concentrate on the tasks that references skim over or ignore and to illuminate the effects of some of the techniques that they describe. All of it is here in case I do another boat: there are so many mistakes possible that I'll never be able to make them all if I start repeating myself.
The kind of kayak I built is called a "strip-built kayak."
The name comes from the way that the body of the boat is constructed
from narrow, thin strips of wood laid longitudinally and then
coated inside and out with transparent layers of fiberglass. The
result is a boat that looks like it's wood but whose structural
integrity mainly comes from the fiberglass. My boat is 17 feet
long with a 21 inch beam and was built from a design by Nick Schade
called the "Coastal." Since everybody asks about getting
something that long out of the basement, let me say that before
I ever started the project I carefully determined that there were
at least two feasible ways out and I ran proving experiments with
a mockup before starting construction.
Here are the construction steps:
The spine of the skeleton on which the strips are laid is made
of a long piece of 2" x 4" called the strongback to
which are attached plywood forms. The forms serve the same purpose
as ribs in a traditionally built boat - they determine the actual
shape of the hull.
I cut the forms from 1/2" plywood that I had on hand. Well, back up a little bit: it cost me $15.00 extra to get the full size form drawings when I bought the plans, and the cost was well worth it. I used spray-on glue to stick the drawings to the 1/2" plywood and then cut them out using a sabre saw mounted upside down in the table saw's table. The forms can be cut right to the lines - not a lot of cleanup is needed afterward if one does a careful job.
Most of the forms are placed perpendicular to the centerline of the boat, but a three-foot long form, aligned fore and aft along the centerline of the boat, is placed at each end. I cut the end forms out of 1/2" plywood also, but in retrospect I think I ought to have doubled them in order to provide a better attachment for the cedar strips which formed the hull. I did bevel the end forms, but didn't bevel any of the athwartships forms. It would probably have been a very good idea to make a 6" station at each end (forms were otherwise spaced at 12").
The strongback was carefully marked with a reference line on its top and along one side. I used a two pass system for attaching the forms. The first pass was aimed at having the forms correctly but not firmly positioned. For this I used cedar wedges (from shingles) and hot glue to set each form in its exact position. I don't think that you can be too careful at this stage. The forms should be clearly marked so that you can easily make visual checks along the vertical centerline, horizontal centerline on both sides and quarter lines (i.e. the turn of the bilge). I found that the three foot long bow and stern forms tended to curve a little, so I nailed a 1" x 3" straightener to the top of each. This was removed only after I finished stripping the bottom.
Once all the forms were perfectly aligned I cut a bucket full of 1" x 1" x 3" blocks (I ended up using about two of them per form) which I screwed to the strongback and each form. These blocks provided a very solid attachment for the forms so they weren't able to wiggle at all. By the way, you need drywall screws and a power driver to do this properly. I don't think nails are a good alternative because of the amount of shaking that must occur when they are driven in.
On each of my two sawhorses I made a slot from scrap 2" x 4" that the strongback nestled in. The slots held the strongback securely, but I could also easily lift it out to turn the boat over.
The thing to remember about this step is that it's the only one that you must not screw up, since a mistake cannot really be undone. If the forms aren't perfect, then the boat won't ever be symmetrical.
Once the strongback was assembled, the next task was to convert
two 18' western red cedar boards and a 16' pine one into about
100 long strips. I used a table saw to cut the strips, though
it is claimed that a band saw does a better job with less waste.
But I didn't have a band saw.
Cutting the strips is not really hard, but it is tremendously messy. It took me a full day to prepare for the job (making extensions to the saw table to handle 18' wood) and another day to cut the wood and cleanup. My references say that it helps a lot to have two people, but I did it all by myself and it went pretty well. The key, I suppose, is to understand that 18' boards have to be well-supported on the infeed and outfeed sides.
I've read that some boatbuilders keep the wood sorted from the moment of sawing so that the boards stay matched. Sorting isn't necessary for pine, but it is a great idea for red cedar if you have the space. This is what the second person should be doing if you have help when sawing and routing. I didn't sort while cutting and ended up spending a lot of extra time afterwards trying to figure out how the pieces matched up. (The cedar varies in color greatly along its length and width. And different boards have different grains.)
All strips should be the same 1/4" thickness and most should be 3/4" wide. It is helpful to have about 6 or 8 strips that are half width. I don't recall how many strips I cut, but it was something like 60 red cedar and 40 of white pine. Think about the color when you choose which red cedar strips to cut into half widths.
The strips come from the saw with a rectangular cross-section, of course. It is optional to route the strips so that one side has a concave profile (the cove) and the other convex (the bead). The curved shape allows adjacent strips to easily snuggle together tightly. It also makes them somewhat easier to work with, but on the minus side it means you need more strips. I think the loss in effective width is on the order of 10%.
I thought that routing the beads and coves would be as big a job as cutting the strips, but actually it was pretty easy. You shouldn't put a bead and cove on any of the 1/2 width strips because that shaves them down to almost nothing. I put coves on both sides of my sheer strips (the first pair installed) but maybe one should leave the upper side (the side that mates with the deck) flat. The reason not to is because that edge is vulnerable to damage and collects garbage (glue and resin) during all the work that occurs before the two boat halves are joined. The reason to do it anyway is because it helps in the alignment process when mating the two halves of the boat.
Laying the strips was not hard. The only "trick" is to make sure you lay the strips so that the cove faces up - that makes it easier to lay the glue. By the way, I didn't use anything special for glue - just regular Titebond carpenter's yellow glue. I didn't do nearly as good a job with the hull strips as I ought to have done. Mostly it was inexperience, I suppose. My feeling now is that while you're doing the strips that extend to the bow and stern (i.e. the ones with the tough curves), you should aim to do only one pair per evening session. Concentrate on getting them perfect - if you don't, then you'll end up like me with very large and unsightly "dead" areas of putty (though much later I figured out how to fill with wood rather than putty in this kind of situation). This is where I might have been helped by having 6" stations at the bow and stern. By the way, use whatever it takes to hold a strip where you want it. That can mean adding cleats to the strongback or even using drywall screws through the strip. The appearance of a puttied-over drywall screw hole is nothing like what 12" of putty over a sunken board looks like.
Don't be intimidated anticipating the task of tapering and trimming the strips: it's not at all difficult and cedar is very easy wood to work with. I used a 6" block plane for almost all of the strip shaping.
From my reading, it seems that everybody has a different idea about what the best tool is for planing the strips smooth. What I used was a 6" block plane and a 4" (?) bullnose plane for the ends. I bought a cheap 3" block plane, but it was useless. I also had various paint scrapers, Stanley surforms and a wood rasp, but didn't use them (at least not for the exterior). For most of the sanding I used a 1/3 sheet orbital sander. For some tough concave parts where I'd applied a diamond-hard putty mixture, I ended up using a disc sander. Of course using a disc sander is very risky, but I managed okay. I also made what Nick Schade calls a fairing sander, which is a strip of thin plywood that takes two 1/2 sheets of sandpaper glued end to end. Mine is a neat item - two nice handles and a teflon base (actually a cut- up ironing board cover) that I can spray-glue the sandpaper to. However, I didn't find it was much use. The orbital sander, on the other hand, was great. I mostly used 40 grit paper, and sometimes 60. The final sanding before the resin sealer went on was with 80 grit. I found that a curved-profile, heavy duty paint scraper was quite useful smoothing the concave interior of the boat.
I'll just say a few words about wood putty. Even though other writers barely mention putty or just ignore it altogether, everybody really needs to use some since inevitably there will be gaps, gouges and other low spots that are impossible or imprudent to eliminate solely by sanding. Get something water based and make sure to get a good color match. Durham's is pretty good and nice to work with, but the color is only right for white pine. So if you use it on red cedar you'll have to tint it. I tinted mine with some fancy Liquitex water-based stain that I happened to have in the house, but water based stains aren't that hard to find (I know Home Depot carries a line). I cannot emphasize enough that getting the right kind of putty in the right color before applying any will pay huge dividends in appearance, time and grief.
The references advise putting a sealer coat of resin down before
laying any cloth, and I did so. One reason for this is to reduce
the air bubbles in the layup. I made a big error in my choice
of hardener: I used the West System slow cure hardener. But its
low end application temperature is 60 degrees and the basement
was always in the 65 degree vicinity. As a result, my mixture
was (I have been led to believe) always on the viscous side. I
think this was a large part of my problems.
I now think that the right application tools are squeegees and cheap bristle brushes. Ordinary foam brushes are too absorbent. The rollers that Gilchrist talks up are pretty much good for nothing - they seem to mainly put air in the layup. I never tried the West System suggestion of cutting a roller longitudinally and using that as a foam brush.
Gilchrist's technique for multi-layer layups is to do both cloth layers at one time with the smaller (if one layer is partial) below the larger. Nick recommends doing one layer at a time and putting the smaller one on top. The West System tech rep also liked one layer at a time. On the exterior of the boat I did it Nick's way, and am reasonably sure that's the best way. Doing two layers at once might save a little time, but not much.
Fiberglass can easily be trimmed with a utility knife when the second coat of resin is done. Don't let it cure hard before trimming.
On the inside of the hull I put a cockpit-sized second layer of 6 oz. cloth (not covering the boat sides) under the full sheet. This time I did the layup Gilchrist's way, i.e. I wetted out both layers of glass at the same time and put the partial layer below the full one. It's much harder to wet out a double layer, I found. Once it cures, you can barely see and feel that boundary. For the interior it's fine, and ends up with much less finishing than would have been required if I'd put the smaller layer on top as I did for the exterior.
All things considered, I believe that the best novice technique for combining partial glass layers with full ones is to put the smaller under the larger, but still wet out just one layer at a time.
The underside of the deck was covered with 4 oz. cloth. Fore and aft of each hatch opening and the cockpit, under the full layer of 4 oz. cloth, I put transverse strips of reinforcing cloth. For the reinforcement I used 6 oz. tape at the hatches and 9 oz. tape by the cockpit.
Preparation for joining the two halves of the boat involved
first cleaning the mating surfaces (the cove was cleaned with
a Dremel tool). I next washed and sanded the interior where the
joining fiberglass tape would eventually be applied, since that
whole region was about to become nearly inaccessible. Once I started
to pull the two halves together I found how helpful the bead and
cove joint was: it was a great help in aligning and holding.
To get the two halves lined up exactly you either need two people or to do something like I did: I hung the deck from bungees a couple of feet above the hull and that let me position the bow halves (the starting point) so they were properly matched.
It requires a lot of muscle to join the two halves. The task starts by binding them temporarily with nylon-reinforced strapping tape. Nick's estimate of 3 rolls of tape was slightly more than I needed, but it would be a real bad idea to skimp on the stuff.
Nick recommends using a putty knife to pry out the hull. I did that and it worked well for me. Also, one of the plywood forms which had been used near the center of the cockpit was a big help: I jammed it inside so as to push the edges outward. I had no trouble at all with the tape slipping - something Nick mentions as a potential problem.
Once the two halves were temporarily bound together, the next task was to make the join permanent by fiberglassing the inside of the seam. Applying fiberglass tape to the inside seam was very tough. I had intended to use a 1" hand cut strip under a 2" machine made strip. But because of the difficulties I encountered with frayed, sticky ends on the handcut stuff, most of the inside is two layers of the 2" wide machine made tape. The problem with that (as pointed out by Charlie Walbridge in "Boatbuilder's Manual") is the machine tape rolls are not very strong in the transverse direction, but that's where one wants the seam strength to be. I tried to compensate for this presumed weakness by using two layers of hand cut tape (1" and 2") on the exterior seam. For the exterior tape I very carefully bias-cut and trimmed the tape. It would be wonderfully convenient to find a source of ready-made 2" bias cut fiberglass tape.
Incidentally, the technique used for the inside tape job was to put the boat on edge and roll from the cockpit. I did the two layers separately, but didn't allow any curing time in between. Soaking the rolls of tape in a pot of resin did not work all that great for complete saturation. Next time it might be better to lay it out on a long sheet of wax paper and saturate it before rolling. That would probably also be less wasteful of resin.
Since it is essentially impossible to get tape applied properly inside the boat all the way to the ends, the last few inches are filled with a resin plug called the "end pour." The mixture used for the end pour is not pure resin but a combination of resin and bulk filler. Sawdust is the best filler, since it is cheap and light. I used silica for the bow, but wised up by the time I got to the stern.
My end pours went reasonably smoothly, though I suspect I used too much resin in the bow. The mixture there totalled 10 squirts (from the resin mixing pumps) and probably 5 or 6 would have been enough. As I recall, the stern fill was made from 7 or 8 squirts. I think my mixtures ended up totalling 6-10 ounces at each end (probably closer to 6).
I did the pours with the boat on end and lashed to a post behind the house. Standing on a ladder, with my head poked through the cockpit, I lowered a small, open-topped plastic bottle filled with the plug mixture toward the end. When the bottle was as close to the end as it would fit I tipped it over (using a string taped to the bottom of the cup). The mixture had a pasty consistency, so actually getting it all out of the cup required a lot of bouncing and bashing which resulted in splashing some of the mixture against the interior sides beyond where the end pour was supposed to reach. To cleanup the spatter I should have nailed a squeegee to a stick and scraped it all down to the end pour, but didn't think of it at the time. So I was punished much later by having to sand that stuff out with sandpaper stapled to a long stick.
The weather was in the 35-40 degree range both days, but so far as I can tell that hurt nothing. The fill gets the area quite hot as it cures - enough to soften the outside resin. I don't believe that any damage is caused by having the resin soften that way. But I used a bucket of water to try to cool it somewhat (ineffectively, perhaps). You have to plan for the water cooling before setting the boat up: put a bucket down with some foam in the bottom and then line the bucket with a plastic bag. The end of the boat goes into the bag and rests on the foam which helps prevent the boat from puncturing the bag. Water is poured into the bucket, and the bag is supposed to keep the boat dry. I didn't experience the bag melting against the boat, but it could happen. I did experience the bag leaking on the first end, which is why I used foam for the other.
For both ends I left the boat outside for about 3 hours, then brought it in and kept it tilted as best I could for several more hours.
After the end pours cooled and I removed the tape, the next step was to do the outside seam. This was kind of troublesome because at the bow, on both sides, there was about 18" where the deck overlapped the hull somewhat. What I did there was to glue in a piece of cedar and shape it to the hull. This is what I ought to have done for all those earlier problems in the hull, rather than using putty (to my everlasting regret). Next I smoothed the joint and glassed it in.
Smoothing the fiberglass surface was a big job which I did not do too well. What I ought to have done was to smooth the hull some and then apply a smoothing coat of resin to fill in the open bubble holes on the hull and the ridges left by the ragged tape edges. But I didn't realize I should do that. So I just sanded a lot, without getting anything like a professional quality surface. I found 80 grit sandpaper - either by hand or in the orbital sander - clogged pretty quickly and that was a major contributor to my quickly losing enthusiasm for the sanding. Foolishly I figured that the varnish would help me out a little and work as a filler, but it really didn't.
The varnishing job was not anything special. I used two quarts of Z-Spar Captain's varnish, applied with 3" foam brushes, and sanded between coats with 220 grit paper. Hull and deck got 6 coats, with two days between the first and second and one day between the others. I kept the shop reasonably clean but didn't do any of the fanatical dust reduction techniques that you read about sometimes.
After the fiberglass sanding and also between varnish coats I scrubbed the surface with a water and ammonia wash and then rinsed with clean water. This seems to have worked well as far as I can tell - there were no problems with application or adhesion.
The cockpit was made much as Nick describes, except that he
has a scheme for giving the cockpit a lower profile (a good thing)
that I couldn't really figure out, so didn't attempt. So, after
the exterior of the deck was glassed I cut out the keyhole shape
on the main deck using his template. Around the edge I built a
ring of 3" vertical strips to constitute the coaming. This
was glassed on the exterior. Then I took some long 1/2" wide
ash cut into about 1/8" strips (so as to be bendable) and
proceeded to laminate a spiral to form the lip of the coaming.
Doing it in a spiral rather than successive rings was my own idea
and I think it worked great. I didn't do anything to the ash to
get it to bend easier, mainly because I don't know how. Fortunately
I did not have any serious problems with splitting. I ended up
with about 7 circuits in the spiral, giving me a hair under 3/4"
of overhang on the coaming. I think that this is barely enough
- more would be better. Also, I believe that a lip thinner than
1/2" would be quite fine - 1/2" is probably the thickest
one could want and I believe that 1/4" would have been dandy.
Incidentally, you cannot have too many clamps when winding the ash. I had about 40 of them of all sizes and shapes and would have been delighted to have twice that number.
Other than that, there isn't much to say. It would be good to read what Charlie Walbridge has to say about the shape of coamings (he wants them curved on top), which of course I didn't notice until it was too late to put his ideas into practice. But I believe that mine will provide a reasonable seal.
All in all, the cockpit coaming was a very satisfactory little project and it looks nice.
The hatch design I used is different from what was on the plans,
mainly because I wanted a smaller and simpler shape. I choose
a trapezoidal shape because it looks good and also ensures that
I cannot get confused about which end is which. The corners of
the trapezoids are not angles, but rather are 1" radius arcs.
The hatch coamings were raised just like for the cockpit, with a finished height of about 1/2." I used Nick's suggestion of self- adhesive neoprene weather seal for the water seal, and I also made an attempt to put something approximating a knife edge on the coaming. It is uncertain yet how this will all work in practice.
My seat cushion is a molded minicell model from VCP, purchased
via Charles River Canoe and Kayak. It's the same seat found in
the VCP Skerry. It is fastened directly to the bottom of the boat
with contact cement. Nick Schade describes building two vertical
strip-and-fiberglass panels on either side of the seat to provide
a snug fit, but I simply used minicell foam which probably does
a superior job for far less effort.
I bought a nylon and foam backstrap from Great River Outfitters, and did install it, but was never happy with it. Besides the expense of the strap and the great trouble I had deciding how to fabricate and install fastening points it, I was convinced it would not be very comfortable. Fortunately I met some people from Zoar Outdoor who had hand-carved minicell backrests for their whitewater boats. So that is what I ended up doing for mine, and compared to the backstrap it's like a Cadillac next to an Opel.
I made a sprayskirt from 1/4" neoprene (couldn't find
any 1/8", which is what I wanted to use), but it was quite
expensive. Materials for mine cost approximately $60.00 and I
could have bought a good quality manufactured one for 2/3 of that
price. I used the method described by Charlie Walbridge in his
"Boatbuilder's Handbook." It was a fun project but only
time will tell how satisfactory the thing really will be. I found
that neoprene is not easy to find, and that undoubtedly is the
reason for the high cost. The "next time" I will try
to find a better source (presumably via mail order from some big
diver's supply house).
One thing that I spent a lot of time pondering over was how to manufacture the backstrap cleats inside the boat. After trying a couple of things, I made nice hefty ones out of 3/4" oak veneer plywood. I had the happy idea of hot gluing them into place and making sure they were properly positioned - a darn good thing because after a trial I moved them significantly. The glassing- in process was routine: hot glue the cleat, then coat with saturated cloth, then (after a partial cure) cut out the opening for the strap. I believe that the best material for doing this would be bias-cut 4 oz. cloth, though I only used that weight for one of the cleats (it took me a while to realize the 9 oz. tape is too heavy for the job). Of course, those cleats are now unused since the backstrap was replaced with a carved minicell backrest.
The next thing I did was to figure out where to put the deck bungees. At the same time I ought to have also considered where to place the aft bulkhead since the fasteners for the bungees pierce the hull, and access to those nuts affects where the bulkhead can be put. Failure to do that resulted in having to place the aft bulkhead slightly farther behind the seat than I would have preferred.
I have three pairs of bungee attachment points on the fore deck, two pairs between the cockpit and after hatch, and one pair aft of the after hatch. The latter is intended to hold the spare paddle blades. I thought carefully about the weaving pattern for the bungees to make sure it would look right, but there's nothing hard about it. Bungee (1/4" diamter) can be gotten at either West Marine or REI. Nylon web straps (1" is the most useful width) and the Fastex buckles and such can also be gotten at either West or REI. For some reason the REI prices are much lower, but of course I didn't realize that until too late. West Marine has a better stock.
For the bungee strap attachment points I used a tip from Chesapeake Light Boat and made a loop of 5/8" web secured to the deck with a 3/4" #8 stainless steel machine screw and finish washer. It looks good and has a very low profile. I used the same kind of machine screws to attach the 1" nylon straps for the hatch covers. Each hatch also has a short 5/8" web tether (like on Sea Lion hatches) to eliminate the chance of losing one of the covers. The only reason to use the narrower webbing (5/8" or 1/2") was appearance.
The bulkheads are made of 3" minicell (closed cell) foam. I made cardboard cutouts as templates, then cut the foam about 1/2" too big, and then shaved down with a Stanley surform until the size was close enough to squeeze in. Minicell is funny stuff to use - it compresses, but not much and you have to give it steady slow pressure - punching it accomplishes nothing. The cutting was done with a sabre saw with a long blade. The blade wasn't quite long enough to go all the way through so I finished up with a serrated edge steak knife (a long bread knife would be ideal). Having started the cut with a saber saw helped ensure a vertical cut, but one still has to be careful with the knife (a lesson I learned in the usual way).
I used 3M 5200 adhesive to secure the bulkheads. The adhesive acted a little bit as a lubricant, and that helped when pushing the foam into place. I put a zigzag glue bead around the perimeter of the foam, and once the foam was in place put a fillet bead around the edge on both sides. The adhesive takes a week to cure and it can be worked for a full 24 hours after the tube is opened! Which was good - I used the same tube to put a seal on all the washers for the bolts that pierce the deck. I didn't get the forward bulkhead as far forward as I should have, so the boat is not going to be suitable for anyone much taller than me. The footpegs were installed after the bulkhead. They are parallel to the sheer line and about 3/4" below it.
I weighed the boat with most everything except footpegs and it came out at 43 pounds, which was right on target.
Other weights from earlier in the project: forms and strongback - 36 pounds; kayak deck (exterior only glassed) - 12.5 pounds; hull (exterior only glassed) 16.5 pounds.
The best kind of foam to use for bulkheads and seats is minicell, and that is what I used on the boat. The technical description of the minicell I used is (apparently) L200 cross-linked polyethylene. The value 200 is the density. It comes in various colors, but I was never in the position of actually being able to choose a color - I just took what I could get. It is easier to find ethafoam, but ethafoam is coarser and does not carve nearly as well.
Minicell is damn hard to find (at a reasonable price). Small amounts are stocked at REI for phenomenal prices. Very large amounts can be purchased commercially, but I spent a day on the phone calling all over eastern Massachusetts and several hours driving around without finding a source that would sell it in lots under several hundred dollars. Great River Outfitters has a reasonable price, and that was my source for the bulkhead foam. Later I found Zoar Outdoor, whose price was about the same as Great River and more convenient for me.
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