Kayak and Canoe Design Bulletin Board

Re: Design Water Line *LINK*

Posted By: Capn Jimbo
Date: Monday, 22 January 2007, at 9:28 a.m.

In Response To: Re: Design Water Line (Andy Waddington)

: It depends on why you are comparing kayaks. But the implicit purpose in this
: statement is that you want to know how the drag differs for different kayaks
: being paddled on the same trip by the same paddler. To make that comparison,
: you would want a waterline for drag calculations that reflected exactly the
: same load.

: If you are using Kayak Foundry, the calculations are done for what it calls
: the design waterline, but you can change the displacement as needed to make
: two different designs carry the same load for comparisons.

: It's unfortunate that none of these design tools seems to incorporate any
: code which shows up differences in performance in anything other than
: completely flat, static water.

Andy we are in complete agreement. The use and misuse/misinterpretation of all too easily produced drag/speed "predictions" is common. Worse are the manufacturers who encourage this by misleading posting of such data. One that comes to mind is the Little Wing - a design with two sets of sponson/wings - that they claim are out of the water "except when edging". In this fashion, and based on their selective numbers they claim "Little Wing's design goal was to provide the performance of a racing kayak with the stability of a touring boat. This goal is accomplished by adding wings."

Of course this is silly as belied by the pictures at their site which show the "wings" engaging the water most of the time, even in relatively calm conditions. Further, their drag predictions are based on an unrealistically light load, ostensibly to keep those wings out of the calculations on which they base their claim.

So your point that real world conditions have a nasty way of infringing on "the numbers" seems entirely valid. Another author has pointed out that these predictions do not take into account the factors of momentum and/or the notion that kayaks are constantly decelerating and accelerating.

Fort Lauderdale Yakfishing Club

Messages In This Thread

Design Water Line
Arne Haaland -- Tuesday, 17 April 2001, at 11:10 a.m.

Re: Design Water Line
Nick Schade -- Wednesday, 18 April 2001, at 9:38 a.m.

Re: Design Water Line *LINK*
Capn Jimbo -- Wednesday, 17 January 2007, at 8:15 a.m.

Re: Design Water Line-My 2 Cents
Mike Scarborough -- Wednesday, 17 January 2007, at 1:53 p.m.

Re: Design Water Line
Andy Waddington -- Monday, 22 January 2007, at 4:44 a.m.

Re: Design Water Line *LINK*
Capn Jimbo -- Monday, 22 January 2007, at 9:28 a.m.

Re: Design Water Line
Andy Waddington -- Tuesday, 23 January 2007, at 5:19 a.m.

Re: Design Water Line
Bryan Hansel -- Sunday, 11 February 2007, at 11:54 p.m.

Re: Design Water Line
Bryan Hansel -- Sunday, 11 February 2007, at 11:56 p.m.

Re: Design Water Line *LINK*
RiverRaider -- Friday, 26 January 2007, at 4:17 p.m.

Corrected link *NM* *LINK*
Greg Fojtik -- Saturday, 27 January 2007, at 1:29 p.m.

Re: Design Water Line
Kris Buttermore -- Monday, 29 January 2007, at 10:24 a.m.

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