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Choosing: My kayaks: Jehu

Updated Friday, August 15, 2008 10:41 PM

Plans kayak - Jehu, €89

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Jehu

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.

Images - Jehu

Jehu - professionally built by Johan WirsénJehu - built by Per Balch-Barth in NorwayJehu - built by Per Balch-Barth in NorwayJehu - built by Jesper Tornebjer

Lines - Jehu

Particulars - Jehu

Length:total/lwl: 520/516 cm*
Beam:total/lwl: 51/42 cm
Draft:11 cm
Cockpit:90 x 40 cm*
Height:in front of/behind the cockpit 25,5/20 cm
Weight:12 kg
Load capacity:110 kg - 280 liter
Calculated speed:9,6 - 14.4 km/t**
PC:0,63
Wetted surface:1,89 m²
Calculated drag:(4 knop) 3,21 kp - (5 knop) 5,85 kp
Stability:low
Intended use:Exercise, competition, and day tours.

* These dimensions can be adapted to suit personal needs or wishes.
** The speed numbers are based on mathematical standard formulas (175 lb paddler + 30 lb cargo weight) and corrected from the kayaks actual performance om trials, on tours and in races.

I can also offer complete kits and professionally built and finished canoes. Please contact me for prices and terms.

The plans

Two sheets contains the nescessary information to build the kayak.

Two sheets

The hull shape change

When Jehu was designed in 1997 it was as a very fast kayak for comptetition, 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 surprice 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.
Hull shape for new and old Jehu

Comments

1 7/27/2008 11:43 AM Wrote Tommy Nansen

Hej Björn.

Tak for hyggelige og udbytterige foredrag på Havkajakroernes træf på Doverodde.

Jeg bor tæt på en søsystem (Google Earth: Farum sø) og ofte er det "overkill" at padle havkajak her.

Derfor har jeg tænkt at anskaffe en marathonkajak.

Men har set du har "Jehu".

Hvordan er dens stabiletet og hurtighed i.f.t. en marathonkajak?

Og kan epoxy indfarves (kan der blandes farvepigmenter i epoxyen?).

Med venlig hilsen

Tommy Nansen

2 7/27/2008 10:41 PM Wrote Björn

Tommy

Jehu är i sin nuvarande inkarnation (reviderad efter de nya multisportreglerna) en ganska stabil kajak - lite mera stabil och måhända en aning långsammare på slätvatten än en maratonkajak. I vågor däremot är den lättare att hålla fart på.

Epoxy är lätt att färga in - jag gör det regelmässigt med de kajaker jag sedan målar. Pigmenteringen av epoxy innebär att färgen kommer djupare ner i ytbehandlingen och minskar risken att smårepor blir synliga.

Om du menar infärgning av virke och epoxy - betsning (beis?) - så går även det men det finns fallgropar på vägen: /faq.aspx#b3

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