RE: [Paddlewise] Skeg Jammers etc

Peter Treby [mailto:ptreby_at_ozemail.com.au]  wrote:>> <<


>>(quoting me in quotes: " I never divide or weigh the gear. Twice as much
is only a goal to shoot
for. I shoot for it by packing every heavy dense bag (and water) that I can
into the stern and then put what won't fit there into the bow..."
One negative with all the heavy gear in the stern is that some heavy gear
will be out at the very stern, offending the aim usually advocated for
maximum manoevrability, of having heavy gear located in the centre
of the boat, and leaving the ends light.<<

This factor is usually way overblown. The major problems caused by it is due
to too much weight in the bow (spearing the waves and increasing the
heave/dip of the hull). If the goal is a better handling gear laden kayak,
one would be wise to load the kayak stern heavy enough to minimize the
weather helm and broaching. I usually put the water right behind my seat so
as to keep it as close to the center as possible (any water in front of my
feet would be a whole lot further from the CofB). However, once using a
rental kayak on a week trip in Baja I found that it handled a whole lot
better (in side winds and following seas) when I put some of my water all
the way in the stern.

>>I suspect this 2:1 trim may not achieve a good result for fish form kayaks
with thin cross sections in the stern, like a Nordkapp. I am now interested
to try this, or more interesting, induce some of my paddling friends to try
it and see what the trim of their boats might look like, and how they
behave.<<

Given the reduced volume aft in a Nordkapp I'd still try to put as much of
the weight as I could in the stern to help keep the kayak at trim with a
gear load. The reality is that getting twice as much weight in the back
would not likely be achieved, but it wouldn't hurt to have that your goal as
you then might actually get enough back there not to have that kayak bow
heavy and weather helming. Of course if we are talking an HM version the
tracking is so stiff already one should try not to make it trim stern down
because that will make it even harder to turn.

> Only in kayaks that float level when empty...You seem to be assuming that
when the centers line up the kayak will be LEVEL.>
>>OF COURSE I have
been assuming that an unladen kayak floated on the water will be trim and
level. It seems to be the case with all sea kayaks with which I am
familiar.<<
[the contrary=] >Most Mariner kayaks for several.<
>>I hazard a guess, without data, that Mariner kayaks are at the extreme of
the swede form long bow design, so that my assumption re
empty-boat-level-trim is true
of many sea kayaks, and true enough of most. Anyone on the list have a boat
which is noticeably out of level trim when placed on the water empty?<<

You didn't say which kayak you own but it may be just as extreme as any
Mariner (if my guess is correct).
Possibly you yourself have an out of trim kayak when empty, especially if my
guess is correct on which kayak you own. Noticeable is in the eye of the
beholder though. An out of trim weight distribution would be a lot more
noticeable when picking it up (and discovering the center of balance is
forward of the front of the seat) than it would be when floating on the
water. When a kayak is sitting on the water one is unlikely to notice a few
(very significant) degrees of angle difference in trim just by looking at
it.

>Since most kayaks don't
>have a seat you can easily move it is a moot point about getting the
paddlers
>weight over the center of gravity of the kayak anyway
>(with a level trim). With a fixed kayak seat you need to play with the hand
>that the kayak designer dealt you.
>>Now this is interesting . How many new boats are sold with any
advice as to trim? Your owner's manual contains advice, maybe you are an
exception. Many boats are purchased second hand. How is the kayak owner to
know what the intended trim is,if he or she cannot assume that the unladen
kayak
will float at level trim? Perhaps not many boats are sold with a level.
Perhaps it is not necessary, as
most boats float level unladen, or at least level enough, and close enough
to
suitable trim so that body movement is enough to make the boat work OK.
Are Mariner kayaks in a small minority here?<<

Hopefully the designer will have placed the seat such that the boat is
either in trim or where the designer has determined the best trim to operate
the empty kayak would be (if he thought about it at all). I think you are
making this all to complicated. The question is how to load a kayak for best
all around performance considering the conditions one might be exposed to.
Even if the designer totally screwed up one can still load the kayak in such
a way as to optimize its performance (even if that performance is still bad
relative to some other kayaks).

>why not just bring a small level with you and once you've gotten into the
floating kayak check
> that the kayak is now level (or slightly stern heavy if loaded with gear)
>>Well, a high percentage of my launches are not onto calm water, and I
do not want to take redundant one-off use gear like a level. How would
the folding chair fit in? I want a practical trimming method, if trim is
important,
that can be used without extra gear. Do you take a level with you every time
you are using a loaded boat?<<

No only when I'm checking the trim of a kayak to either determine the seat
placement or to check if the boat I'm wondering about is as out of trim as
it looks like it might be. My method is much simpler. I follow a simple rule
for a heavy gear load: "Put all the densest stuff in the back." It doesn't
much matter where level trim is when you are looking for the best handling
performance, what matters is to get the best handling without messing some
other important factor up too much.

>>More level problems: the point where you want to know that the kayak is
level is obstructed by the seat and fittings, making you level it at a point
forward of the seat, at least theoretically not the correct point to measure
level
trim. In practice that is close enough if the keel there runs level. In some
boats,
due to the hull form there may be no suitable point to place the level.<<

Sure there are exceptions and if you go back and read my original statements
I'm confident that I left room for them in what I wrote. With ninety plus
percent of sea kayaks you will be able to use a level just in front of the
seat to reasonably accurately check the trim (if you want to get that picky
about it). I'm not that picky except when I'm designing the kayak. It is
hard to get too much weight in the stern of any fully loaded kayak and the
consequences of overdoing it are minimal compared with not getting enough in
the back.

>>Re the plane-in-a-wind-tunnel-at-45-degrees:
I see that you meant the combination of forces on a free moving kayak, and
not what you said.<<
>If the wind is blowing such that it hits end "A" first
> that end will have more pressure on it than end "B".

>>After a brief moment, the wind pressure is equal along the length.<<

No, I meant exactly what I said. The wind pressure will be greater on the
end of a long symmetrical object more pointed into the wind. This will
continue to be so until that objects turns exactly crosswise to the wind.
Please look this up and show me a text that contradicts me before continuing
with this part of the thread.

>What kayak do you paddle?
A swede form boat with chines at the stern and a bloated V bow.
Sound familiar?

It sounds like maybe I'm the hull designer. Is it the Nagdee Expedition?

>When sitting still in a side wind does your kayak blow straight sideways
or slightly bow or stern down wind?
>>Fairly quickly bow downwind, so that it is balanced in moderate winds at
usual
paddling speeds. I like that.<<

So do I. It sound even more like I designed it. I'll ask again. What model
is it?

>>I am still now intrigued as to a practical method of finding the design
trim
of a boat, given that a level assumes the keel line it is placed along is
suitable for
level trim.
What about those boats you decline to name? Will the intended design trim be
uphill towards the bow?
No kayak manufacturer paints a waterline on the boat. Is that the only
really
definitive way to determine ideal trim?
Rambling thoughts, it is late,<<

One of the unnamed kayaks had a stern down trim of about 3" (nearly 2
degrees). I'd determine the ideal trim with some experimentation with
different loads in different conditions. Then I'd try to repeat the loading
that made the kayak handle the best in the worst of conditions.

Matt Broze
www.marinerkayaks.com
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