pent a considerable amount of time on optimizing the hull and deck lines. Some little more rocker at the bow, and less (almost square) at the stern. The hull is now a bit finer (less full), hence reducing Cp (prismatic coefficient) further into the [0.48 ~ 0.5] range, quite low indeed. Primary stability is also reduced a bit, with Kmt (transverse metacentric height) at about 21 cm, but the boat is sufficiently stable already.

Cb (block coefficient) is now reduced to 0.33, stepping outside the normal range of [0.35 ~ 0.45]. That is, the boat wouldn’t be very efficient at lighter load, e.g: with the paddler alone. But that would be fine anyhow, since the hull is optimized toward its full displacement, beyond 115 kg. And as confirmed with experiences in my previous kayak Serene – 1, the boat would feel a bit heavier, but more comfortable at full load.

Some other design considerations still need to be done, but they won’t be reflected into the 3D modeling, for the sake of simplicity: the cockpit size and shape, the size and position of the hatches, the rudder and rudder control, etc… Serene – 2 will have a 3^rd hatch, or usually called: the day hatch, which locates right behind the cockpit, to store food for lunch and other frequently – accessed things during a paddling day.

2^nd image below: the stability curves for various loads: 85, 95, 105, 115 and 125 kg. The curves look exceptionally fine in my eyes, they won’t decrease until 50 degree of heeling angle, and the shapes of the curves closely resemble each other, showing a predictable behavior in hull’s stabilities. Almost done with the designing, I think, next is finding some free times to build the boat in the upcoming months.

ntil this second design, I’ve been able to “read through” the hull designing parameters: Cp, Cb, Cm, Kmt, S, LCB, LCF, etc… interpret them correctly and know quite well what they do mean in real – world boat characteristics and performance. Many days out there paddling in various conditions and many hours spent on the whiteboard (a.k.a the Free!Ship software) make me feel very confident with my designing process.

The hull is shortened to 17 feet, reducing wetted surface area, but with minimum rockers, the waterline length is unchanged, also the designed – displacement is slightly increased to 120 kg, as 110 kg of maximum load is a bit under desire as pointed out in my last 9 days trip. Beam is slightly reduced from 45 cm to 44 cm, but both primary and secondary stabilities is significantly improved. I feel very pleased with this design so far!

Unlike my previous boat, the new one would have a curved deck. It is more difficult to build a round, curved deck, it is also harder to build hatches, compass cup, bungee cord anchor points and other parts… onto it. But with a curved deck, the boat will look nicer, less windage, and weigh less overall. Looking from above, it shapes exactly like a bullet, should I engrave a motto onto it: built like a gun, runs like a bullet !? 😀

The most important design decision is to increase the amount of deadrise. In my experiences with Serene – 1, the kayak has excellent sea – keeping abilities in rough conditions, something I didn’t feel with all my previous boats (e.g: the Hello World -3, which has a much flatter bottom). I would attribute that ability to the deeper V – hull, which offers quite a low primary stability, but should let you at ease in waves & turbulences.

‘ve been thinking a lot about the design of my next build. Serene – 1 is a good kayak, she has proved that during my last 9 days trip crossing all mouths of the Mekong river. The boat shows her excellent abilities in various conditions, big waves, strong winds and turbulences, even when overloaded a bit above her designed displacement, she gave me a kind of confidence that I’ve never felt with any of my previously – built boats.

In the quest for an ideal kayak that perfectly fits me, I proceed to designing my next boat, Serene – 2. Some lessons learnt from my last trip are immediately applied: first is a transom – mount rudder. I’ve been into conditions of strong wind blowing whole day, and without a rudder to help adjusting the bearing, corrective paddling would be extremely fatigue. This will have an influential effect to all other designing considerations.

LOA is reduced to 17 feet, approximately 3 times the height of my body. Since maneuverability is entrusted all to the rudder, the boat would have a very full waterline length, very little rockers at two ends. I decide to reduce prismatic coefficient – Cp further to around 0.5; my sustainable speed in reality (paddling at sea with full load) is only around [3 ~ 3.5] knot. There is no reason to waste energy for a higher speed that I can not sustain.

Block coefficient – Cb is reduced to 0.35, this would improve directional stability a lot. In Serene – 1, this value is 0.45, which explains the boat directional un – stability on long distance. Transverse metacentric height – Kmt increased to 21 ~ 22 cm, roughly equal to most popular Greenland sea kayaks, and hence greatly improve primary stability. With Serene – 1, this value is 17 cm, enough to frighten any novice paddlers.