Vortice VS. Bark... No Contest (on flat water)

[greatdane]

Just traded boards with a friend for a couple weeks.  His 16' rudderless Joe Bark for my C4 Vortice.  Just got back from my first paddle on the Bark.  Only had a few minutes tonite so went to my local lake. My regular loop, that normally takes me 27-30 minutes blew by in 21 minutes!!  I knew the Bark would be faster in these glass conditions... but holy crap that's way faster.  The amazing thing is how QUIET the board slices through the water. 
Obviously comparing these rigs is like comparing apples and oranges.  The Bark might flounder in 4 foot or bigger swells (at least with me on it) due to such little rocker.  But all 16' is in the water... which translates to speed... the Vortice has so much rocker that only about 11-12 feet of it are in the water (flat water that is)
Can't wait to try the Bark in the open water.. there is no leash plug, so I hope I don't swim too much.

[PonoBill]

Yikes, don't go out on a windy day. With that freeboard the board will sail away from you much faster than you can swim.

[paddlesurf.net]

You should see the newer Barks and Hobies- they're even more radical with foot comings and wells and destroyer bows! I've seen a few at the races around here and they just plain look fast- don't know how they'd do in heavy swell, don't seem like they'd fit the chop but they're kicking ass around here!

[Dwight (DW)]

I've been following these racing threads for awhile and my arm chair impression is the Vortice is made for our conditions. Cape Hatteras and Cape Fear always have big swell when the wind blows. Now if I could just get a Vortice owner who lives where the ocean swell is small, to sell his board to me cheap, I'd be set. 

[Tom]

Greatdane, Why do you think it's so much faster? Is it flat bottomed, concaved, or what? Do you have a picture of what the bottom looks like? Inquireing minds want more infromation.

[PonoBill]

I bet it has something to do with Joe Bark revolutionizing paddleboarding a zillion years ago. He's been shaping fast stuff for probably twenty years. As I recall even Mark Raaphorst venerates him a bit.

[Tom]

I bet it has something to do with Joe Bark revolutionizing paddleboarding a zillion years ago. He's been shaping fast stuff for probably twenty years. As I recall even Mark Raaphorst venerates him a bit.

Bill, I've been noteing the times you've been posting about your training and I need to know how to get a lot more speed. That damn walker keeps bogging me down.

[PonoBill]

I think it's mostly my board--an old Starboard 12'2" in the Ke Nalu shape. That and the ten miles a day I've been paddling, though I'm still just about as fat.

[greatdane]

Posted some pics in the Gallery.

Why is it faster?  My thoughts are that it is 2 feet longer... and length almost always = speed in boat science.  Very little rocker allows it to glide over water and not "push" water like a huge rocker will at slower speeds.  Also, the nose is displacement and allows it to slice through water instead of slap over the top of it.

On a steep ocean swell, the Vortice would probably excel, but I'm not sure.

The bottom is almost totally flat, with rounded rails.  The first three feet of the board starts to get round and turns into the kayak-like nose.  It was custom made for a guy who weighs 220, and I weigh 180...

[PonoBill]

So I start this post by saying I know very little about hydrodynamics and boat hulls, though I used to hang out and make a pain in the butt of myself at the hull testing tank at MIT when I was a kid. Pretty thin credentials.

What I do know is that for a displacement hull the wetted length limits the top speed. Doesn't matter how much oomph you put into pushing it, they won't go faster unless you make them plane over the bow wave. The formula is 1.34 times the square root of the waterline in feet. So a twelve foot hull should max out at 4.75 nautical miles per hour. which would explain why I can't do much better than a steady five MPH on my 12'2", though my GPS does show peaks of nearly 8MPH. A sixteen foot hull gets you to 5.36 knots. Eighteen gets you to 5.7. Of course none of this takes into consideration catching a swell, since you are clearly planing then. that's why you blow by people.

I'm not sure that a surfboard is a displacement hull, but I suspect that with my fat ass on it that it probably is. A Destroyer nose probably slices water rather than pushing it in front of a flat line in the water (surfboard rocker) so it takes less energy, which means you can be at or near the peak speed longer,  but it won't go faster unless the boat is longer.

[greatdane]

I may be improperly calling the Barks nose "displacement."  I've been using the term basically to describe boards that have more of a kayak or boat like prow, than say a flat surf board.

Maybe Mr. Foote could chime in sometime with his theories on fast boards?

[PonoBill]

I'm reasonably sure that all hulls--even surfboards and multihulls--are displacement hulls until they climb into a plane, and that doesn't happen until they ride over their bow wave.  To my knowledge there really haven't been any man-powered planing boats, you need wind, wave or a motor to make the hull plane past the bow wave. Even long skinny sculls with all their mechanical advantage (sliding seat, cupped oars, super slim hull) don't exceed displacement hull speed, which is the reason they are so long.

[greatdane]

Pono,  here might be the one human powered boat that can overcome the bow wave... you just have to be Olympic caliber to paddle it...


http://www.foilkayak.com/videos/

[PonoBill]

That's handy. Even then your guts explode at a kilometer or two.

[greatdane]

I guess we won't be seeing a hydro foil sup any time soon.