Some tweaks here and there to smoothen the jointing edges between the hull and deck, putty – seal the bulkheads to the deck, then some slight overall fairing and sanding before putting on the final layer of fiberglass to the bottom part. The glass will marginally wrap over the deck (about 1 inch of overlapping) to strengthen and completely seal the joint. Deck would have no fiberglass on the external side, and would only be clear – coated with thinned epoxy and polyurethane (PU) paint.

4^th image below: the deck thoroughly sanded with 100 grit paper, it looks quite fine now! In my previous boats, I was usually over sanding, with multiple grit – levels applied, and lots of efforts too. But now, I’d realized that I actually don’t need a furniture – grade finish (and I couldn’t do it as nice as a professional woodworker nevertheless). After all, a boat is a functional (not a show – case) object with lots of hard and harsh uses. A too perfect finish wouldn’t be of any practical good!

5^th image: the deck has been stained with thinned epoxy mixed with color pigment (yellowish wooden color). The white duct tapes mark the area of wrapping when glassing the bottom. 6^th, 7^th images: glassing the hull exterior and wrap the fiberglass an inch over the deck. I used exactly 300 gram of epoxy mixed with dark brown wooden color pigment. A lesson learnt from the previous boat: use lighter colors for the wood to appear natural, too strong, deep colors look very… ‘artificial’.

Carved and installed two wood blocks at the two ends to drill holes for the pulling knots (to further save weight, I won’t pour epoxy into the two tips, just the wood blocks with some sealing putty), sanding the cockpit coaming, glassing the lashing lines’ anchor points built into the hull, some more miscellaneous jobs before I can dry – fitting the hull and deck together. In the next couple of days, we’ll see the boat in its final shape! First two images below: inside and outside of the anchor points.

Cut a slot in the aft deck for the skeg box to get through, then the hull and deck are ready to be jointed together, with just some epoxy (not putty) applied to the edges. The two ends, bow and stern, fit well, I just need duct tapes to press them together. The mid section requires some fastening as the plywood bent and and does not offer a perfect match. Nevertheless, the overall process is smoother compared to my previous boats, and I’m so happy to see the kayak taking on the designed shape!

I spent times going around and around the boat, watching the fruit of my efforts! The hull shape looks very fine to me, the deck shape is quite crude indeed (not as cursive and fine as that of Hello World – 3, since the deck was drawn to be easy to build). But in essence, the lines, size, weight… all gives me a very comfortable and manageable feeling! Just a few more weeks from now and the kayak would be ready for her new life on water, can’t wait any more for that!

Conitnue working on the deck part and the cockpit. But first… some pictures to show off the boat shapes, still quite a long way to the final forms, but look fascinating enough to me already, to quote a popular architectural saying: form, IT IS function! 3^rd image below: the cockpit coaming being reinforced with some putty in the corner, then a layer of fiberglass tape the under side. 5^th image: cockpit being jointed to the deck. There’re some miscellaneous jobs to be done on the hull still.

15 anchor points to be built into the hull. First, I glued small wood blocks alongside the gunwales, then drilled two holes (1 inch apart) into each block. Plastic lines 5 mm in diameter (the one usually used in fishery net) are run through, then putty is filled in, this way, just a small amount of putty is used. When the epoxy has cured, pull the lines out, you would have some “tunnels” to run the lashing through. Finally, small pieces of glass would cover and strengthen the wood blocks.

The cockpit coaming is glued, then glassed with the deck, two layers of fiberglass (one under and one upper), it’s very strong now, can withstand the weight of my whole body (while climbing onto it). For such a narrow kayak and small cockpit (45 cm in width, less internally), I don’t install any foot brace or thigh brace, and even back rest, the cockpit almost fits my lower body. I have no idea for a seat for now, maybe that I would just sit on the bare bottom, or with a thin layer of mattress.

Most major tasks on the hull has been completed, now continue on the deck part. First is cutting out the fore and aft hatches’ holes and fit some reinforcement rims (the plywood is weak, it can deform badly around the hatches in the long run). The Beckson hatches are quite small indeed, the largest are 8″ in internal diameter, have to live with that for now anyhow since Beckson does not have a larger size. I also made a rough fairing on the external side of the deck. Next comes the cockpit.

The plywood is so fragile and easy to crack, so I turned to using wood for building the cockpit coaming. 2 thin strips of wood is combined to form the cockpit coaming riser. The strips are cut 3 mm thick and easy enough to bend without steaming, just use the C – clamps to force them following the cockpit template. The riser is quite high, 2 cm, and would be jointed with the plywood coaming lip 3 cm in width, all would be reinforced with some putty and fiberglass before jointing to the deck.

Using the angle grinder, I adjusted the bevel edges of the gunwales to better match the hull and deck. Also glassed the 3 hull’s external seams, each with about 80 gram of epoxy (240 gram in total). With experiences gained by now, I can control the amount of material used quite precisely. Hence, this gonna be the first boat which I could have weight truly under control, my projection is somewhere around 17 ~ 18 kg overall (everything not including the paddle). Let just see if I could make it there!

Boat building is a labour – intensive process, and only skills and experiences could help to reduce workload and improve quality. Up until now, I’m quite pleased with the building, my 4^th one. Today, I cut a slot into the aft hull to install the skeg box, the excellent Fein multimaster oscillating tool offers a nice cut as usual. Things went on smoothly, I have great confidence in this 5 cm fiberglass tape, it produces very fine and strong seam lines, so I decided to use just 2 layers (one inside, one outside).

In my previous boat, I used 4 layers of fiberglass to secure the skeg box in place (which results into more weight added). The skeg blade is smaller, 30 x 14 cm, I guess a deeper V – bottom would track easier, so I would need a smaller blade just for some weather cocking conditions. Still stay indecisive about skeg’s control, I’m not totally happy with HW – 3‘s skeg control line, which runs over the aft deck, though perfectly functional, potentially could interfere with self – rescue actions.

Working on the skeg box vs. hull joint (the external side), then give the bottom a rough fairing to remove excess putty and smoothen out the edges, then apply 300 gram of thinned epoxy to it. A long busy day with lots of dust. Next would be exposing the hull to sunlight for 1, 2 days for the xylene solvent to completely vaporize, before glassing the external seams and other jobs. The hull part would receive an additonal overall layer of fiberglass once it’s jointed with the deck part.

Various miscellaneous jobs in preparing for the next steps. First is glueing the skeg box and glassing the skeg blade (I use the “skeg in a well” as in my last boat, the skeg box is like a “well”, going through hull and through deck, a design that greatly facilitates maintenance and repair). Then forming the cockpit coaming by 2 nested narrow strips of 4 mm plywood, bending around the MDF frame cut earlier, the ply is so fragile that I had to brush it with a layer of epoxy to prevent cracks when bending.

There’re still lots of things to be done before two halves of the peanut shell (a.k.a hull and deck) could be jointed together: fitting the starboard gunwale, fitting and glassing fore and aft bulkheads, install some cross – beam stringers, install the skeg box and it’s control line, making and installing the cockpit as well as the two hatches’ rims, build some lashing anchor points into the hull… any many other unnamed jobs. Forcing myself to slow down as not to let my impatience harm the kayak quality.

5^th image below: the stringers glued and screwed in place, these stringers serve multiple purposes: help maintaining the boat width profile, support the skeg box and bulkheads, the stringer right behind the cockpit would help strengthen the deck (as the only way to get into the kayak is climbing upon its aft deck then slide your legs in). 6^th image: the fore and aft bulkheads clamped in, ready to be sealed with putty and then glassed. Next would be the important job of installing the skeg box.

Epoxy resin and putty are the most crucial parts in small watercraft building, yet they’re the most annoying, paranoidly sticky and easy to mess around. It takes me a long time to learn how to use them properly. After filling all the internal seams with the 511 putty (which I found very good for boat building), I put a layer of 5 cm – width fiberglass tape over them. I highly praise this double – weave glass tape: easy and quick to work with, precise laying, resulting in nice, tidy and tight bondings.

With my previous boats, I haven’t got these fiberglass tapes yet, hence had to resort to bias – cut fiberglass, and it is next to impossible to make out a straight narrow strip of 5 cm, consider the mediocre local plain – weave 6 – oz fabric I was using. The very satirical thing is that this tout simple commodity of fiberglass tapes is not available anywhere in Vietnam market, and so I had to buy them on Amazon.com and have them shipped from the US, with delivery fee doubles the purchasing cost!

To further reduce weight, I only glass the internal side in part, the mid section slightly larger and around the cockpit, the place that could potentially expose to water. Next would go in the gunwales (a.k.a the sheer clamps) and the bulkheads. The gunwales are 15 x 30 mm long strips of wood, bevelled to match the deck’s profile. 7^th image below: jointing 2 strips of 3 m wood to form the gunwale that covers the entire 5.5 m length. It’s so good a sensation to see the boat gradually take shape!

The bigles jointed very well, with just some neglectable tiny defects, port and starboard pairs match perfectly. Before putting them all together to form the initial boat shape, I applied a layer of penetrating epoxy (epoxy thinned with xylene), taking care so that the amount of epoxy used won’t exceed 0.6 kg overall. For this job, I use a kind of elastic epoxy with the B5 slow hardener. There’re two kinds of epoxy: one hard and one elastic, with at least 3, 4 kinds of hardener available in the local market.

I put a layer of fiberglass to the internal side of each joints before stitching the bilges. The deck is quite easy to form, since it’s very well geometrically – defined, I don’t even need to use steel wire and thus, avoid the unpleasant job of drilling holes, just duct tape over the edges, then dully apply the putty onto the bevelled seams. The hull is not that simple, with wires to fasten particularly at the two ends. Check the geometry of the overall shape, fasten the wires tight, then fill the seams with putty.

Cares are taken to use as little putty as possible, as I especially long for this to be a light boat. The same steps as in my previous boats, but done by more skillful hands. Actually, I sometimes feel bored with those same things having been been done 4 times already, I should be planning for another boat in a different building method. But sure, not until I could feel I’m good enough at the current method, if you’re not “up to the level” yet, you would probably done wrong with whatever method used.

Using staples to clamp 2 sheets of plywood together, I then cut the hull’s planks, port and starboard, all is composed from 3 pieces. Then the deck’s pieces, and other parts: forward and aft bulkheads, skeg box and skeg blade… After 3 boats, I can now cut the wood with quite some accuracy. Sometimes, I’d wished to have the accuracy of a CNC machine, but such a machine that can cut in the 1.22 x 2.44 m dimension is not a possible option for most home builders, including me.

Next is the dusty job of beveling the edges of the plywood bilges, the edges are carefully bevelled at different angles along their lengths, to ensure a suitable gap, not too small, and not too big, for just a small amount of putty to go into the seams in a later phase. Then I joint the parts together using finger joints instead of the originally – planned puzzle joints. Straight finger joints, though not as strong as puzzle joints, they’re easier to cut and to fit, and most importantly, easier to align longitudinally.

This is very important, in my first boat, the 2 ends of port and starboard bilges differ as large as 5 ~ 6 mm. I can now confidently keep the tolerance under 1 mm along the 5.5 m length. Patterns of the joints are drawn on paper, photocopied into multiple sheets, glued onto the plywood and cut accordingly. I work carefully as to ensure a tight fit, an accuracy of a small fraction of a millimeter is required. This is quite hard when done by hand as my thinnest saw blade is already over 1 mm thick.

Serene – 1 is quite a distinctive boat, originally took inspiration from the Black Pearl and the Anas Acuta, but in it current status, it shares not a single common point with them. The hull has been transformed into a light cruising one with long water line, deeper V bottom, little rockers and a very narrow beam (45 cm). There’re times that I’m worrying on the feasibility of the design, except for some theoretical calculations, there’s nothing to ensure me that it would be a good watercraft.

When you build something from a well – known designer, it’s already a well – proven boat. For Serene – 1, there’s no way to know, unless you build and trial it yourself. Eventually have some free time to proceed on today, first is cutting all the hull & deck framing stations in MDF. Can also see drawn is the cockpit template, this would be a very small one, 50×40 cm in dimensions, that’s what they called an “ocean cockpit”, you would need to climb over the aft deck and slide your legs into the hole.

The framing box showed up, by now, I could see how slim the boat would be, at this size, you just don’t ride the kayak, you essentially… wear it! Like an integral part of your body going to rough water, that’s how the feeling should be! Next would be the important task of drawing, and cutting the bilges from exported offset tables. For ones who don’t know, offset table is just a matrix of (x, y) coordinates, I use a very fine matrix (points every 5 cm interval) to precisely reconstruct the bilges on plywood.

Finalized my new kayak design, a considerable amount of work on optimizing the hull shape, adjusting it back and forth to find out the minimum drag numbers (based on the Kaper algorithm) while keeping stabilities and other parameters under control. Some numbers: LOA / LWL (length overall / waterline): 5.500 / 4.945 m, BOA / BWL (beam overall / waterline): 0.452 / 0.420 m. I reduced the boat width to exactly my hip plus 4 fingers (that is: 36 + 9 cm, my fingers are quite big, 9 cm for 4 fingers).

Designed draft: 0.11 m, Designed displacement: 95 kg, Cp (prismatic coefficient): 0.5475, Cb (block coefficient): 0.4064, LCB (longitudinal center of buoyancy): 0.5225, VCB (vertical center of buoyancy): 0.0690 m, LCF (longitudinal center of floatation): 0.5136, Cw (waterplane coefficient): 0.6445, S (wetted surface area): 1.699 m², Aw (waterplane area): 1.329 m², Am (midship section area): 0.034 m², Cm (midship coefficient): 0.7466, KMt (vertical transverse metacenter): 0.196 m.

Predicted drags at 0.11 m draft (95 kg of displacement): 3 knot ~ 7.122 N, 4 knot ~ 12.622 N, 5 knot ~ 23.763 N. Predicted drags at 0.121 m draft (110 kg of displacement): 3 knot ~ 7.679 N, 4 knot ~ 13.611 N, 5 knot ~ 25.506 N. The hull is heavily optimized for speed in the [4 ~ 5] knot range with some sacrifices in stability and load capacity. Now that all “theoretical calculations” has completed, it would take a few months to build the physical boat to tell the real truths about the design!

Made some good progress in the process of modeling my new kayak… For a human – powered watercraft, water doesn’t like complex curves and shapes I think, so they need to be as simple as possible (it is not too simple to come to that simplicity though). The model is then decomposed by Free!Ship into several “developable” plates, at this point, professional builders could just output the plates to a large CNC machine, which would precisely cut the plywood accordingly.

I print those plates to paper to make a 1:15 paper model. Cut the plates with a pair of scissors, then stitch them together using transparent duct tape. Making a paper scaled model would help verifying about the “develop – ability” of the product, double check if there is any design mistake, and give a clear view on how we should compose the pieces into the final boat. For simplicity, I didn’t draw details such as the cockpit, skeg, lines or hatches, just the basic shape of the kayak.

The paper model is a bit ugly (my hands are not too skillful though), but the pieces come together perfectly, the shape just looks like a bamboo leaf! This gonna be a long, thin kayak with very little freeboard! Next would be finding some free time to materialize all these drawing onto the plywood sheets. I don’t have a printer that’s large enough to print the plates in their real sizes, so I would just redraw them using offset table exported from the CAD software, actually, I prefer this manual method!

It tooks just a few hours to learn the new software and construct the basic 3D objects: hull & deck. The time – consuming tasks are adjusting the shapes and playing around with hydrostatics. Some basic measures: LOA / LWL (length overall / waterline): 5.50 / 4.44 m, BOA / BWL (beam overall / waterline): 0.483 / 0.451 m, Draft: 0.1 m, S (wetted surface area): 1.66 m², Cp (prismatic coefficient): 0.5619, LCB (longitudinal center of buoyancy): 0.5150, LCF (longitudinal center of floatation): 0.5192.

Additional hydrostatics parameters, VCB (vertical center of buoyancy): 0.0590 m, Cb (block coefficient): 0.4684, Cm (midship coefficient): 0.8336, Cw (water plane coefficient): 0.6385, Displacement: 0.096 tonne… Well, I wouldn’t pretend that I fully understand those parameters above, cause they contain insights into a boat that can only be correctly interpreted by an experienced designer. However, I’m tweaking around to optimize the parameters toward a higher Cp, higher LWL, and lower S.

Drag (resistance) predicted by the KAPER algorithm looks fine till now, however, the displacement is sacrificed already, 96 kg, barely enough for me (65 kg) plus 30 kg of gears. This gonna be a demanding boat with low primary stability, not recommended for beginner. It takes some real world experiences to understand why low initial stability is indeed a good thing, and why a kayak which appears to be very stable on flat water could probably throw you up side down in bumpy conditions.

In the progress of learning to design my new kayak… you know its name already. I’m using Free!Ship, a CAD software running on Win XP virtual machine (with VirtualBox) on my Macbook. I haven’t used any CAD software before, haven’t designed anything 3D, not to say about a watercraft. So why designing a kayak!? Well, first, just for the fun of doing something yourself from A to Z. Second, though I’m no naval designer in any sense, I believe I have some guts on how a good kayak should be!

Many kayaks are designed for 70 ~ 90 kg paddlers on average, I’m not that bold, and I need something slimmer, lighter, with the drawback of sacrificing some load capacity of course. I’m re – modeling my kayak after Björn Thomasson’s Black Pearl, using just some publicly – available pictures of the boat. And it’s not a copy, there’re some modifications: slightly narrower beam, slightly less rocker, and slightly deeper V – bottom. And I would stick still to my familiar stitch & glue construction method.

Why stitch & glue!? Strip build generally offers best boat shapes, but look at the Inuit people’s SOF (skin on frame) kayaks, those “hard chines” suit naturally to S&G, the method is simpler and takes less time (which I don’t really have much for now). It gonna be not an easy process: just for the hull, adjust the 60 control points back and forth, recalculate the stability and performance parameters, repeat again and again until you’re satisfied with the results. I hope I can finish the design in about a month or so.