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Kayak and Canoe Design Bulletin Board
Re: Dynamic versus static weight
Posted By: Nolan In Response To: Re: Dynamic versus static weight (Nick Schade)
Date: Thursday, 26 August 1999, at 2:42 p.m.
> Kinetic energy is not the energy required to maintain velocity, rather it
> is the energy required to obtain velocity.Oh Nick! How could you step right in front of the force equation?! F=MA.
The kinetic energy is the energy of the moving body. The energy required to obtain a change in velocity (direction included) is force.
This is why even in a nice vacuum, you cannot shove a sitting locomotive down the track, or stop one that is moving. Your ability to impart significant amounts of energy are negligible compared to the energy of the locomotive. Though you can cause changes to a light weight hand car sitting on the same tracks in the same vacuum.
I certainly will not argue about the increased draft and drag, for those are important factors as well. But mass itself cannot be simply ignored.
I would also agree with you that for the average paddler under average conditions that minute amounts of weight changes will not measurably affect speed, especially in light of the many other factors that will. But, for a paddler who is going to be paddling all day, weight very definately has a direct bearing on how well that paddler will be doing come dinner time. Will one pound all by itself be a phenominal effect? No, but 20 lbs may. And 150 lbs certainly will.
> Carrying a boat, you must support the weight, paddling a boat the water
> does it for you. All you need to do is make the boat move. Weight is much
> more of a factor carrying the boat to the car than when you have it in the
> water.In the strictest of math modeling, the carry factor doesn't matter. Only the lifting of it does, and that is negated as soon as one lowers the boat. You know the drill about work. And in real world stuff, the better balanced the load, the easier it is to carry, hence the price for really good back packs. It's also why U-haul went with that low frame truck.
But when it comes to moving a body in a horizontal direction, it does not matter who is floating in whom, for all the mass must be propelled. A 50 lb person in a 100 lb boat must expell the same energy as a 100 lb person in a 50 lb boat if both are moving at the same velocity. All other factors being equal or removed.
> 150 lbs during a cruise will make a difference, but not as much as if you
> had to carry it all on your back.That I certainly disagree with. For this greatly has to do then with a persons muscle structure, experience and loading, and therefore becomes highly subjective. Myself as an example, I am far more experienced with hiking and carrying heavy loads then I am with propelling myself from the shoulders. To cover a given distance, it would be much easier for me to do so upon my feet, using my legs for propulsion, carrying a balanced load that is properly distributed. Other peoples milage will vary of course.
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