Jehu
Latest updated Friday, October 25, 2024, 19 comments
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Plans, Jehu - 135 EUR
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Jehu is a very fast kayak for exercise and competition. The hull form is close to a competition K1 with high PC and minimal wetted surface. When competing it measures as a "turkajak" (exercise/touring kayak, as defined in the Danish competition rules).
The tradeoff is of course low stability. It takes a skilled paddler and some practice to keep Jehu right side up. The secondary stability is on the high side for the type though - in capable hands Jehu can be a swift touring kayak, provided you travel light.
Jehu can be used with a stern rudder for touring or a standard through-the-hull competition kayak rudder – faster but more vulnerable. More exciting but also more complex to build is an integral rudder (an under-water section of the stern turns 20° to either side), a virtually friction-free steering system with extremely low turbulence. The speed advantage is surprising.
Even apart from the rudder, Jehu is a more demanding project than the other kayaks. With thinner strips and a severe bending in the ends, this should probably not be your first attempt at boat building. But if you try your hand at it, the reward is a kayak with a great potential to be first over the line.
Particulars
| Length¹ |
520/516 cm (overall/WL) |
| Beam |
51/42 cm (overall/WL) |
| Draft |
11 cm |
| Cockpit¹ |
90x40 cm |
| Height¹ |
25.5/20 cm (in front of/behind the cockpit) |
| Weight² |
12-15 kg |
| Displacement/volume⁶ |
110 kg/280 litre |
| Speed³ |
7.9/12.1 km/h |
| Prismatic coefficient |
0.63 |
| Wetted surface |
1.89 m² |
| Drag⁴ |
1.31/2.29 kp |
| Stability⁵ |
1/3 (initial/secondary stability) |
| Intended use |
Exercise, competition, and day tours. |
* These dimensions can be adapted to suit personal needs or wishes.
** Depending on type of wood, equipment, care with epoxy usage, sanding etc. etc.
*** The speed numbers are based on mathematical standard formulas (175 lb paddler + 30 lb carco weight) and corrected from the kayaks actual performance om trials, on tours and in races.
⁴ Calculated resistance in 4 and 5 knots (at nominal load capacity).
⁵ Initial stability and secondary stability on a subjective scale, where 1 is very tippy and 5 is very stable.
⁶ Displacement is kayak + paddler + load. Count off the kayak weight to get the load capacity.
Stability
The curve shows the calculated stability with a static load, and therefore of limited use for a real paddler. The part of the curve near zero degrees indicates the initial (primary) stability – the steeper the curve, the more stable. The part of the curve left of the peak indicates end (secondary) stability – the higher and wider, the safer you feel edging the kayak. The position of the peak shows also how much the kayak can be leaned without tipping over. The part of the curve to the right of the peak with rapidly decreasing righting moment is almost impossible to take advantage of.
Plans
The plan sheets contain the information needed to build the kayak/canoe. Station molds, stems and construction details are full scale. For kayaks the recommended cockpit size is shown half scale with offsets for a full scale drawing and advice on altering the size. On the plans you will also find advice on how to shorten or lengthen the craft. Lines and construction drawings are in metric scale 1:10.
The illustrated step-by-step building manual is in Swedish only, but it is available online in English: it covers all steps in detail and will guide first-time builders through the project.
Plans, Jehu - 135 EUR
Purchase
A new hull configuration...
When Jehu was designed in 1997 it was as a very fast kayak for competition, training and light touring, without any regards for rules and classes. Lately, I have had a number of requests to draw a version that conforms to the Danish touring class of kayaks, that has a similar agenda but demands a wider hull for more stability. Some have also asked about the American touring class and the coming European rules for kayaks used in multisport events.
These three rules systems, though not identical, have enough specifications in common to allow designing a version of Jehu to suit them all. The difference is mainly the length, but this is easily customized when building, by just altering the distance between molds.
So a new Jehu was born. The main dimensions are the same, but the waterline beam is increased from 40 to 44 cm and the draft adjusted from 11 to 8,5 cm (to maintain the displacement). The deck in front of the cockpit is raised 1,5 cm (requested by those used to competition paddling) and to keep the visual balance the stem was raised the same. The volume in the stems are reduced slightly and the sheer is a little narrower in front of the cockpit to allow for a closer stroke.
Much to my surprise I managed to tweak the wider hull to almost the same speed potential as the older (the hydrodynamical calculations indicate a loss of just 0,5% at approx 6 knots) and is of course, more stable, which means that a lot more paddlers will be able to use the speed potential.
Left: the new Jehu with a wider underbody – right: the old Jehu plans, that will be available for those who may prefer the more classic look.
