RE: [Paddlewise] bracing and power

Something just didn't seem right but I was having trouble putting my finger on
it. My daddy always said that if you want to see how things work, take them to
the extremes. So let's make the paddle blades very heavy but also very big and
buoyant. When the paddle is absolutely vertical the buoyancy balances the
weight at some point. Let's say at just the depth you want the blade to be. So
if we make the paddle weigh 32 pounds and the blades are 1/2 of a cubic foot
and weight 15.5 pounds each so the blade will support the paddle in seawater
(which weighs 64 pounds per cubic foot) when the blade is fully submerged. To
simplify things a bit lets say the paddle could be operated vertically but
tumbled in the direction of kayak motion (like a paddle wheel) by the paddler.
With a slight, but not imperceptible, shove to accellerate the upper blade
slightly the heavy blade would fall forward due to gravity and the lower blade
would pop up as the weight over it was reduced by the upper blade falling
forward so here gravity and buoyancy would drive the forward stroke until both
blades were out of the water (or laying flat in it if the paddler has yet to
intervene--what seems like free energy here really isn't because energy was
used to get the paddle to that vertical position in the first place and
therein lies the rub). At that point the paddler is either holding up a 32
pound paddle against the accelleration due to gravity (coincidentally, 32 feet
per second per second) or they are trying to pick the rear blade back up while
pushing the front blade down (if they hadn't held it up against gravity) to
restore the original vertical position. The forward falling blade has some
momentum and falls forward with a splash but because the rising rear blade
isn't vertical over it yet the front blade can not be sunk enough to immerse
the blade without some additional effort required to work against the
buoyancy. To make matters worse, the blade rising from behind didn't get
enough "pop" to go to vertical on its own either (unless some extra effort had
been made against buoyancy in the beginning to sink the other blade deeper
than the paddle weight would do itself). Therefore, the paddler is going to
have to work even harder to lift that rising blade against gravity while also
pushing the other blade into the water against bouancy further than it will go
on its own in order to again restore verticality again (where the buoyancy
just balances the weight).



Would you like to use my 32 pound buoyant paddle or would you want to have the
blades weigh as little as possible and have no buoyancy? How about the paddle
just weigh just one pound more in the blades and have blades buoyant enough to
support the paddle with the blade fully immersed? How about the same weight
paddle but with buoyant blades. There is no free lunch in the universe.



______________________________
> Date: Sat, 17 Jul 2010 10:30:23 -0400
> Subject: Re: [Paddlewise] bracing and power
> From: carey_at_jimparksfamily.com
> To: marinerkayaks_at_msn.com; paddlewise_at_paddlewise.net
>
> A quick point on weight and weight distribution. This is a simple
observation made with limited data points, so I'm not claiming fact here, but
just suggesting paddle weight in use is complicated by buoyancy in a similar
but opposite way as windage. The weight of the paddle in air might be
different than the effective mass of the paddle in use. My GP is quite
buoyant. I'm not required to support a lot of it's weight while in use. And I
think I use it to take advantage of that buoyancy by paddling a little more
vertical at times thus resting the off-side weight on the submerged blade a
little, and allowing the float to pop the submerged blade out of the water and
start the swing going. Having an EP that also has buoyant blades I believe I
can separate the buoyancy from the other EP/GP characteristics. I like the
floaty blades on that EP too. A rhythm can be established that sort of bounces
the paddle from side to side making use of the buoyancy.
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