serene – 1, part 3

ade 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!

Serene – 1, part 1
Serene – 1, part 2
Serene – 1, part 3
Serene – 1, part 4

Back to the number 70.39 Watt, a heavy labour (such as a bricklayer) produces about 75 Watt on average, and for only 8 hours. You know what it’s like to paddle 10, 12 hours on a minimum basic, or even more, like I was paddling for 16 hours from Vũng Tàu back to Sài Gòn in my last trip!

The book Kayaks Of Greenland by Harvey Golden is a great guide for home builders, it contains dozens of kayak models ready to be built, with all the necessary drawings! I used some models from the book as references and comparisons when designing this Serene – 1 kayak!

serene – 1, part 2

t 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.

Serene – 1, part 1
Serene – 1, part 2
Serene – 1, part 3
Serene – 1, part 4

Some rough calculations on the energy required to propel a kayak. My target speed is 7 kmph, or 3.8 knots. From the numbers recorded by my Garmin over the years, in normal big rivers and sea conditions, speed is reduced by 1/3 compared to the ideal condition of flat water.

That is you have to struggle at 5 knots to assure that 3.8 knots. The Kaper algorithm tells you that, this Serene – 1 hull produces a resistance force of 27.35 Newton at 5 knots (or 2.57 meters per second). Making the multiply: 2.57 x 27.35, that’s the output required: 70.39 Watt!

serene – 1, part 1

n 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.

Serene – 1, part 1
Serene – 1, part 2
Serene – 1, part 3
Serene – 1, part 4

Recently, I’d noticed that Japanese kayakers usually use kinds of slim, long kayak similar to the Black Pearl, that’s quite understandable cause the body – building of Japanese is Vietnamese alike, we’re not too bold. Use a slimmer, lighter boat, and pack your gears cleverly for longer trip!

It’s interesting to know that, in the old day, in building kayaks, the Inuit people has “recipes” to measure the size of the boat: length should be 3 times the height of the paddler, width should be the hip plus somewhere from 4 to 8 “finger”. Well, like shoes, boat is tailored to match the user.

hello world – 3, part 27

Thanh san hoành bắc quách,
Bạch thuỷ nhiễu đông thành…

onna end the series on my Hello World – 3 kayak building & fitting here with some comments on the design. It is an excellent boat in almost every aspects. The outlook is beautiful and attractive, extremely good stabilities (both primary and secondary), good tracking capability, and turning is easy with some slight edging. The hull shape is good for surfing too, it goes into turbulences, water or wind, with great confidence. And it is roomy, having lots of space for gear storage on longer trips.

On another side, the boat is more suitable for bolder paddlers, in order to sustain a higher speed. Me, at 64 kg, belong to the medium – low paddler group. With my inexperiences (still) in building, boat weight is quite large. Everything put together, my whole day sustainable speed with HW – 3 is bounded into the [6.2 ~ 6.5] kmph range, a bit behind my expectation. Of course, my expectation is of my own, some goals set and to be reached, not something to blame on the kayak design.

And maybe my physical excercising has not been hard enough too! Like I’d mentioned earlier, boats are like shoes, you try until you find something that fits your needs, and also like shoes, owning 4, 5 pairs or more is just quite normal for an average person nowadays 😀. Looking back on all my building and boating experiences, the last 2 years is, anyhow a short period of time, for a life – time hobby. I’m still at the beginning of the road, there’re lots of things to be learned and to be accomplished!

Lots of things happened during that less than 2 years time period, at the beginning of which I even can’t tell the (now – obvious) differences between a kayak and a canoe, I didn’t know how to operate a hammer or a block plane, never done any woodworking before (as well as any other real ‘manual’ labour). Started from the most primitive A, B, C… sometimes I’d wished I didn’t have to do everything the hard way like that. Well, things gradually unfold, like the sceneries ahead of your kayak! 😀

hello world – 3, part 26

Bạch đầu lãng lý bạch đầu nhân…

he other day, I was conducting some re – entry tests: supposed that you’re thrown out of the boat by waves, and you need to climb in again, pump the water out to continue paddling before another wave hits you. But the hatches leak so much that re – entry is very difficult, the harder the next tries, as the kayak continues to take water in, it becomes heavy and unstable. This is very dangerous, imagine if this happens on open sea, and I would never want to be in an… “Abandon ship” situation.

I ordered some Beckson deck plates (plus other things) from as a fix to the hatch leaking problem. But it took forever for the ordered packages to be delivered, first from Amazon to a friend in the U.S, then from him to Saigon (some goods can not be shipped directly to Vietnam, so you have to make it via a “freight – forwarder”). Can’t wait the progress, I decided to try another solution: install some rubber washers and tighten the locks to help sealing the hatch better. It works quite well indeed.

The packages arrive today finally! But 2 Beckson screw – in deck plates would be used for the next boat instead, as I’m satisfied with the leaking problem now. Also arrived are some rolls of 2″ – width fiberglass tape, those would be very useful for my next builds, and a spray skirt. A spray skirt is absolutely important for kayaking in rougher conditions. It recalls to me that I was really risking (and was lucky too) when paddling to Vũng Tàu last year with no working water pump, and no spray skirt.

Below are a couple of shots showing the spray skirt in action. On calm rivers and canals, it’s not of pretty much usefulness, but it would become critically important once you enter the steep estuary and coastal sea areas. Also showed is the beautiful lines of my HW – 3, people is all taking photographs or shooting video on the kayak when encountered along my paddling routes these days! Despite some building faults here and there, she looks so gorgeous, almost sexy, doesn’t she!? 😀

the pleasure room

aven’t watched the movie (50 shades of grey) yet, nor do I really want to (haven’t gone to the cinema for the last 10 years or so, and I don’t even have a TV at home also), just want to make a little parody! 😀 Having lots of intentions to widen and upgrade my boat – building workshop, and lots of new ideas on boats too, but currently pretty much busy with my works… hope to materialize them in the upcoming months!

hello world – 3, part 25

Lý Bạch thừa chu tương dục hành…

pdates after updates, Hello World – 3 has become quite heavy indeed, now around 30 kg, too heavy to be handled on my back for long distance. Weight has been one of my weakest point in boat building, I’ve always had fears that the boat will not be strong enough, so put more and more materials in, that results into a much heavier boat than originally speculated 😢. This is the most important thing to be improved in my next build (projected to be toward the third quarter of this year).

Want it or not, HW – 3 is my main boat for now, though quite heavy, it’s strong and has the best performance characteristics among my boats. And I’m gonna have some more preparations for my upcoming trips. I added one more mounting point for the light and camera poles, there’re one aft and one forward of the cockpit, so the camera can be mounted in different positions. Also decided that the Canon Powershot D30 would be my sole camera onboard, used for both picture and video shooting.

The Canon Powershot D30 has much better battery life compared to my GoPro Hero 3, and video quality is comparable, though video resolution is not as good. Furthermore, bringing just one camera, one kind of backup batteries would make things simpler, having less to be cared for when on the waterway. I’m not too keen on taking super fine photographs, bringing a DSLR is too bulky and risky for me, so this D30 is already good, an all – round cam: pictures, videos, and can also be used for diving.

I’ve built another cart for my kayak from cheap MDF, made water – resistant using thinned epoxy and paint, it’s smaller and lighter compared to the previous one (which was made of iron tubes). And I reused the two big air – filled tires, you know how it is pulling a heavy load with small solid wheels on a ‘sinking’ sandy beach. There’re some stuffs I originally planned for my kayak, but they turned out to be very troublesome when faced reality. Among such things are the hatches, simply put: they leak too much!

hello world – 3, part 24

Yên lung hàn thuỷ nguyệt lung sa…

ast batch of updates for my kayak before Tết (Lunar new year), a detachable and retractable light (and camera) pole. At a bicycle accessories shop, I found a small signal light which uses solar cell (about 3 square inches in area). Testing the LED torch showed that after being fully charged, it could continuously blink for two nights, more than enough to be used for the boat. It has 4 blinking modes, which could be changed by a switch located behind.

The light is small, lightweight and most importantly, doesn’t need a separated battery since it uses solar energy (that means: less thing to be cared for in a journey). The pole, in its retracted position, is high enough for the signal light to be visible from other vessels on water. When the GoPro is in used, the pole is extended about one foot higher so that the camera could get a better view ahead of the boat. And the whole thing could be used, as a… selfie stick when needed.

Screw off the pole from the connecting dock bolted down to the aft deck, attach my other Canon D30 camera to the end, then I have a selfie stick in hand. Well, I’ve been concentrating more on boats and paddling, not the photography things, but it’s better being able to capture the beautiful scenes along the paddling way anyhow. There’re still many things to be done for the kayak, but that would be until the next year. For now, just more and more paddling, 25 km every 2, 3 days or so.

May the new year comes for me with more will and determination to reach my dream target. The more I understand about the task, the more challenging I’ve realized how it would be, for now, I’m not sure still if I could make it: lots of practicing and preparing, a huge deed of efforts and endurance required to make that 300 km (6 ~ 7 days or more) journey. May the new year comes with more internal calm and balance, for me to live wholly in this simplicity and purposefulness.

hello world – 3, part 23

Trường châu cô nguyệt hướng thuỳ minh…

ade some more miscellaneous improves to my HW – 3 kayak… First is filling the two boat’s ends with Polyurethane foam. For an example of how PU foam works, see a demo video here. It takes just a few minutes for the mixed – two components to expand into a closed – cell (water proof), somewhat rigid structure. The foam I bought is exactly the one used for refrigerators’ insulation (see the 2nd image below, two bottles containing two components called: Polyol and MDI).

The foam adds about 600 ~ 700 grams to the boat’s weight, it fills about 1 meter of boat length at both two ends, occupying a total volume of about 60 liters (estimated). This is just an act of precaution, as in the worse case should the boat cracks, or if there’re holes punched into the hull, the whole boat could be flooded, but it will still stay afloat. I erect the kayak upright, pouring the mixed PU foam through the hatch, wait for 15 minutes, then repeat the same thing for the other end.

Instead of making a complex foam seat as I originally planned (which could be very time consuming cause it requires creating a mould), I chose to install instead the simplest thing that works. Bought a small plastic kid seat, cut the four legs away. A strap line helps holding the seat in place (bolted to the cockpit coaming) and supports its back. The size of the kid seat is about right, not too small for a comfortable ride, and not too big so that a spray skirt could be deployed later.

This season, Christmas, Gregorian New Year until Lunar New Year (about 1.5 month from now) the city is decorated with all kinds of lighting, creating splendid sceneries. I’ll try to have some night paddling to capture those colorful moments. With the overpopulation situation in Sài gòn becoming worse and worse day after day, I dare not step into the urban districts these days anymore, viewing the city from above the water seems to be a very nice alternative option to me! 😀

hello world – 3, part 22

Kính hồ lưu thuỷ dạng thanh ba…

aving made some more thorough testing, I’m now feeling very pleased with the new boat and its build quality. After several 20 ~ 25 km paddling trips, I think I can average out at 7 kmph for extended time (5, 6 hours) and probably longer with more endurance exercising. That’s still not up to my expectation yet, but about speed, on the internet, you can hardly find trustable reporting on kayak and its paddler’s abilities, some boating information is purely… bloating!

At some points, due to the lack of correct information, I did have some illusions on paddling speed. But now I definitely know that a typical good sea kayak has the average, sustainable speed in the 7 ~ 7.5 kmph range. Beyond that would be the domain of racing kayak or surfski, which could step into the 8 ~ 9 kmph range, the best of which could not reach too far beyond 9 kmph. And that probably would be the target of my next build, though currently I have no plan for it yet.

Unlike HW – 2, I feel very comfortable to paddle HW – 3 into the wind. The hull pierces waves nicely, and I think the boat would surf well also. Haven’t had the chance to trial the kayak in big standing waves, but in some lesser situations, I’d noticed that the boat rides waves in style, with very little drifting, shaking. That’s a characteristic very much needed when I would leave the relatively – calm rivers to go into the much more choppy areas of coastal sea and large estuaries.

It’s approaching year end and I’ve got lots of other stuffs to do, so there won’t be any big updates to the kayak until next year. It’s a real pleasure when on rivers, people was asking where I bought the boat from, and when I told them that I built it myself, none believes it 😀! This season, day temperature is dropping below 25°C (that’s already called “cool” for a tropical Saigon), good for going paddling indeed. Some video shots to show the boat, captured with my GoPro mounted at bow.