: Yup, I was thinking that and just wasn't sure if I wanted to bring it up. But
: since someone did. Here is an exert from something I am working on for my
: web site. Still needs some editing.
: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

: Everyone knows that a longer boat is faster than a short boat, right? That is
: what I was always lead to believe. When I started to design boats and
: learned more about hull design I started to question this. I also realized
: you have to define what fast means because it means different things to
: different people. Fast to a Racer is fairly obvious, top speed. But what
: about the paddler that never paddles at racing speeds for more than a few
: seconds at time? Does fast really mean top speed potential?

: Since speed is relative to the paddlers strength a much better way to look at
: it is how much effort it takes to propel a boat at a given speed. Using
: hull resistance numbers you can compare one boat to another with hard
: numbers instead of opinion.

: The method I used was to take an existing design in my computer and let the
: software stretch and shrink the length of the hull, nothing else. What I
: found was interesting and not what exactly what I had been lead to
: believe.

: Clearly the longer hulls are faster. At 8 lbs of resistance the 21 ft boat
: would be at least .5 mph faster than the 15 foot version. Meaning for the
: same amount of effort from the paddler would go faster in the long boat.
: So long boats are faster. Well, actually they have more speed potential if
: you have the horsepower to power the boat.

: How many recreation paddlers can keep up these speeds for more than a couple
: of minutes? From what I have read and seen not many, the average
: recreational paddler travels at around 3mph with the more experienced
: probably closer to 4 mph. The number of paddlers that maintain a higher
: than 4 mph average are a fairly small group. With this in mind the chart
: looks a little different.

: Dropping down to the more typical speeds of 3mph you see something
: interesting, the 15 foot boat has the advantage. Under approximately 4.5
: mph the shorter 15 ft. boat is actually faster (has less resistance) given
: the same amount of effort. The paddler in the longer boat has to exert
: more effort to maintain the same speed.

: At 2 lb of resistance the 15' boat is approximately .4 mph faster than the
: 21' boat. Meaning if you paddled for 2 hours that would put you almost a
: mile further down the river for the same amount of effort.

Hi Jeff et al,
To throw a large spoon(paddle) into the mix.
If the hull speed formula 1.34x square root of WL is applied and assuming the 15, 18 and 21 foot lengths were waterline lengths, a paddler would be limited to 5.19kn, 5.68kn and 6.14kn respectively.
Few kayaks are actually planing hulls and few people would be able to produce enough power to lift a planing hull (as a kayak) into planing mode to "break" the implied hull speed limit.
Some paddlers can and do exceed this theoretical limit on a regular basis in sprints.

From messing about with multihull designs in the past, there seems to be a strange effect on the 1.34 factor when the waterline ration exceeds 8:1. At higher ratios, the factor changes to between 2.5 and 3.5 as far as wave generation is concerned. So far, I haven't seen any theoretical data on this effect, just empirical.

Like quantum mechanics, I think you need some dice to roll a sanity check. 6 and higher is good. I just rolled a 5.

Mike Savage
South West Cork