RE: [Paddlewise] Kayak Profile

The Spartan looks to be fish formed to me. If you put a stick under an inner
tube to make a longer waterline you don't increase the hull speed. You could
chop four or five feet off the ends of the Spartan and it would be about as
fast as it is now. However, that is due to the prismatic cooeficient rather
than any asymetry. Essentially any hollowness in the ends are likely to make
the hull act shorter since the bow wave is made further back along the hull
and the finer stern isn't as well supported by the second wave at speeds
approaching hull speed. The hull will then "squat" at a lower speed (in a
shorter wave length). This fine ended shape is slightly more efficient at much
lower speeds though.



Your Nordkapp was very efficient at normal cruising speeds but is not a
particularly fast kayak in a sprint. Some would argue with me, but on the
waters surface it is my understanding that, other things being equal, slightly
Swede-form is faster than slightly fish-form. Racing canoes are limited by the
rules in how Swede-formed they can be. If it weren't faster why would the rule
be needed?



We discuss this whole subject in a lot more detail in the FAQ's in our
website.

> From: douglloyd_at_shaw.ca
> To: marinerkayaks_at_msn.com; PaddleWise_at_paddlewise.net
> Subject: Kayak Profile
> Date: Thu, 25 Mar 2010 17:53:19 -0700
>
>
> Matt, et al:
>
> I'd like some objective comment regarding a kayak's overall asymmetrically
> profiled shape as seen from above with respect to forward paddling
> efficiency at a moderate sprint.
>
> I demoed an Atlantis Spartan VI last year. I liked the kayak for the
quality
> construction, fact it was a local kayak, had a bonded-in skeg line, large
> oval hatch at bow (many only have a round hatch located there), nice low
> wind profile, reasonable responsiveness in all regards, good foot and cargo
> room, and paddled efficiently at 3.5 knots. Here's the profile seen from
the
> top:
>
> http://www.atlantiskayaks.com/spartanvi.htm
>
> While I know Matt that so much of a kayak's performance originates from the
> various hull curves and asymmetry at various sectional levels, you can see
> from the overall top profile that the Spartan's forward bow section
provided
> a narrow entry line but flares quickly at the front bulkhead.
>
> When I got the kayak up to 4 knots then tried sustaining it at further
> speeds, there just didn't seem like any real return for the effort. It
would
> move smartly along but then fall off rapidly. Even though my Nordkapp is
> Fish-form, it didn't do this. I always felt I was the limiting factor at 5
> knots.
>
> Other kayak profiles show Swede form with long, more graduated entry line,
> plus the fact the gear mostly stuffs in the rear compartment where the
Swede
> form has its bulk.
>
> Atlantis may be coming out with a shorter play boat next year and P&H has a
> new offering thins year, but I have not seen the profiles yet. The Cetus
> certainly is big-butted, but suffers from weather cocking a bit.
>
> So, is the Spartan VI profile the issue with top speed question?
>
> Thanks.
>
> Doug Lloyd
***************************************************************************
PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
here are solely those of the writer(s). You must assume the entire
responsibility for reliance upon them. All postings copyright the author.
Submissions:     PaddleWise_at_PaddleWise.net
Subscriptions:   PaddleWise-request_at_PaddleWise.net
Website:         http://www.paddlewise.net/
***************************************************************************