Re: [Paddlewise] QCC boats and water line length ........

Pease ignore this post as it was sent mistakenly before I edited it. I often
write quickly and then edit later in an effort to make teh post more clear.

-----Original Message-----
From: 735769 <735769_at_ican.net>
To: paddlewise_at_lists.intelenet.net <paddlewise_at_lists.intelenet.net>
Date: Saturday, July 24, 1999 8:24 AM
Subject: Re: [Paddlewise] QCC boats and water line length ........


>Matt wrote;
>
>(Large SNIP)
>
>Matt, when you have read the papers you can tell me if I have interpreted
>them incorrectly.
>
>
>The Navy has never had much concern for costs where performance of ships at
>sea is concerned. How do I know? From my years building Navy ships and
>sailing with a senior officer from the Bureau of Ships. Perhaps Matt has
>better background than that. I would like to hear why they would place cost
>above performance when Matt is paying the bills via his taxes. :)
>
>
>
>>As a group I have never thought of open canoes as seaworthy (well maybe a
>>short rockered whitewater "open" canoe packed full of flotation).
>
>
>I guess you had to have been there to appreciate the seaworthiness of open
>canoes. or even open boats in general. Like Viking ships, the open boat
that
>Bligh sailed, or the Umiaks, etc. Some some experience with them helps.
>
>.
>
>>As I said
>>above ships operate in a different environment than kayaks relative to
wave
>>sizes and steepnesses, although I'll agree naval ships offer the closest
>>comparisons to long narrow kayaks that exist in the ship world. After
>>designing our first Mariner (18'-5"x 20.5") I was surprised that most of
>the
>>relationships between the dimensions were almost identical to those of a
>>naval destroyer.
>
>Ain't that neat?
>
>
>>I know someone on this list has one of John's kayaks out here in Seattle
>>because I have seen it. If you are reading this post lets go paddling on a
>>rougher day (or through the Montlake Cut on a busy summer Sunday) so I can
>>see for myself if John's design is an exception to my experience with bows
>>with little or no rake.
>
>Boy, I can apperciate how unbaised that will be. :)
>
>
>
>>GYRADIUS? If you insist on using words I can't find in a nautical,
>>scientific or Webster's dictionary please define them for us. Is pitch
>>gyradius related to the moment of inertia as I'm imagining? I think you
>>might be reaching here as well. I'm having trouble even picturing a
>>displacement sailboat without a lot of overhang at the bow (and sailboats
>>have a much different shape from a kayak, so I question the relevence). I
>>don't know but I'll bet Gerritsma advocated keeping the ends of the
>sailboat
>>light to reduce the "pitch gyradius" and didn't mention overhang at the
>ends
>>at all because that wasn't something he experimented with.
>
>Sorry for using a word you don't find familiar. I don't now wat you have
>read so you have the advantage of me here. I suggest you read the paper and
>discuss this with Gerritsma.
>
>
>>
>>Big waves do not get as steep as small waves so kayaks operate in rougher
>>conditions than ships, same physics, different scale. Salt water waves
>>(where most Navy vessels operate) do not get as steep as fresh water waves
>>(where a lot of sea kayaks operate). Deep water waves (where ships
operate)
>>are not as steep as waves steepened by shallow water (surf) where sea
>kayaks
>>sometime operate. I'm the first to admit that much can be learned from the
>>study of "Ships in Rough Water". (In fact the book by that name--by
>>Kent--was very influential in the design of our first kayak.) However, the
>>situations are not totally analagous.
>
>Yes, they are. The Navy and Coast Guard also operate in fresh water.
>
>>So if you think my opinions are all wet, I guess I'd have to agree. ;-)
>
>I failed to keep track of the boats I have paddled or sailed.
>
>
>>I think you are both missing the point here although both are right in
what
>>you said. We do design for collisions but not just with other kayaks. I
>>often purposely collide with the shoreline at full speed. I skid right up
>on
>>it (if the beach is sand or rounded rocks and the barnacles aren't too
>>thick).
>
>Gee I do that too with my boats. Maybe I am just a lucky guy sinvce my
>boatrs are designed all wrong.
>.
>
>
>>
>><snip>
>>>In any case, the long overhanging bows increase the moment of inertia and
>>>add weight in the least desireable place.
>>
>>In a loaded sea kayak (which is the time it is most likely to put its bow
>>under) this increase in inertia would be insignificant.
>
>
>Do you have teh proff of this?  Even in an empty sea
>>kayak it would be quite small. Your argument is also assuming the same
>>waterline length. I would argue with the primacy of waterline length here
>>because, as the QCC website so rightly points out, more waterline length
>>increases wetted surface and other things being equal that increases drag.
>>A long waterline is essential to a racing kayak being operated at top
speed
>>but that extra waterline length is often a detriment to a sea kayak where
>it
>>likely increases cruising resistence but more importantly often decreases
>>controlability and responsiveness.
>
>Called design optimization
>>>
>>>I respect Colin's opinions. I have a few that I cherish myself.  In this
>>>case, however,  we have a wealth of information derived from many studies
>>>into the performance of boats in rough water spanning many years. With
>this
>>>at our hands we can temper our opinions with more objective information.
>>
>>All the studies in the world don't mean much to me compared with test
>>paddles of real kayaks in real conditions. My advice to kayak buyers is to
>>paddle as many kayaks as you can and then take your favorites out into
wind
>>and waves and compare them head to head. You will know what is right for
>you
>>without having to listen to all the confusing arguments for and against
>this
>>feature or that and what study of ships or sailboats proved what.
>>If at all possible don't buy a kayak without trying it out, preferably in
>>some wind and waves!
>>
>>Matt Broze
>>http://www.marinerkayaks.com
>>
>>
>>
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