Date: Tue, 09 Nov 1999 10:41:43 +0100
From: Stefano Moretti <stmoretti@tin.it>
To: baidarka@lists.intelenet.net
Subject: Re: baidarka directional stability
Message-Id: <19991109102537.FRVZ8346.fep14-svc.tin.it@stefano>
Llama wrote:
> Stefano Moretti wrote:
> <snip>
> > First question: how experienced are you as a paddler ? Did you
> paddle
> > many different boats before? I would look a this aspect first.
>
> Not at all; this is my first kayak.
So, do not be so disappointed, it will probably improve in the next
future, as you learn more about how it behaves.
> Other way around, actually. The sit-on-top was a 12 footer and the
> kiwi
> boat was an 8 footer, and both tracked better than my 16.5 footer!
>
> > > The boat has considerable rocker, about 2.5" astern and 1.5"
> forward.
> >
> > It really sounds like you have switched ends. I never heard of a
> boat
> > (kayak) more immersed at the bow than astern,
My comment mirrors in some way that of the experienced designer John
Winters:
> > speaking the boat has positive stability roots which just says that the
> > turning moments forward of the Center of Gravity exceed the turning
> moments
> > aft of the Center of Gravity.
> >
> > 2. If the designer intended the boat to have a rudder then he may have
> made
> > the boat intentionally directionally unstable. I have designed boats
> this
> > way because it allows a reduction in wetted surface and makes the boat
> more
> > responsive with the rudder up (or partially up).
>
Being it a "marathon boat, reduction of wetted surface may have been an
intended design feature
>
> > 1) a certain amount of keel. My two have an angle at the keel which
> is
> > thus more immerged than the rest of the hull (not flat in other
> words).
> >
>
> Now if the problem is caused by being immersed too much in front,
> wouldn't a keel just make matters worse?
I cannot tell in advance. My keel is immerged in mid sections and comes
above water lines at front and rear sections (overhangs although
moderate)
>
>
> > 2) placing the centre of gravity over, or slightly aft of the centre
> of
> > buoyancy. In other words: correct trim.
> >
> > To find out in practical terms, fill several bottles with water -
> same
> > size possibly 0.5 or quarter gallons - and shift the weigth from
> back to
> > front or a blend of the two until you get correct trim.
> > My first kayak paddles much better with 3 gallons added, of which
> 2/3
> > forward.
>
> I will definitely try that. Although it seems a pity to take a 38 lb.
>
> kayak and ballast it down . . .
It is indeed, but if your intended use is coastal cruising or camping or
even pic-nics, this exercise would answer the question : "Where to place
the load", so that you may obtain correct trim and better handling while
carrying your daily stuff, rather than just water bottles.Water bottles
or any other known weight make the calculation easier.
> > Let us know the results
>
> Will do.
>
> We'll be waiting... Stefano
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