jp pro edition

Hi iam riding a 8.6 29 110 liter jp pro edition iam an advanced sup short longboard racer surfer ,iam 85 kg 186 cm ,iam thinking of changing my 8.6 jp with a 8.0 27 95 liter 2015 jp pro. My home break is mostly weak beachbreak but i can still punt airs and heavy carves and cutbacks, so i need an advice if the. New jp pro 2015 8.0 will be going to short on the volume ,i still cant choose between the 8.2 or the 8.0jp pro ? Any help

Surfforlife,

I weigh 94L and ride the 8'2" & 8'6" JP Surf so the 8'0" will be fine and in fact from all accounts from people like Piro the 8'0" & 8'2" are very close in size, at your weight and if surfing as good as yous ay you could even go down to the 7'4".

Pete

Do you guys find your JP's to be hard to turn when you don't use the paddle? I'm asking because JP sets the fins with zero cant and zero toe.

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magentawave said..
Do you guys find your JP's to be hard to turn when you don't use the paddle? I'm asking because JP sets the fins with zero cant and zero toe.

I have owned several JP windsurfing wave boards over the years. They are excellent boards, perform well in waves. The fin configuration is the same - no toe-in. I have my eye on the JP 8-10 Pro SUP. I think JP knows what he is doing with his boards.

Magentawave I think these two videos will answer that question

The theory behind the straight zero cant & toe fins is speed and power return from your turns. It's been used for years in Windsurfers & Kite boards nothing new. Have a look at your rear fins in your quad set they are zero cant and reduced or no toe. Tow boards are the same with minimal cant and toe. Another thing is FCS have zero 5 & 7 degree cant boxes so the FCS fins are straight except for ones like the H2's. Unless you get a custom board and specify cant boxes you get straight like all the Sup production boards , that means you are already riding zero cant but didn't realise like the rears in your quads.

Future boxes are all straight so the cant is built into the fins but even Futures are now offering reduced cant fins. I have taken it a step further with my VP fins and you can now buy zero cant with a future base. I've had heaps of emails from shapers of 30+ years saying it can't work , my reply is what happened when you tried it ? answer "I never have"...Boom I rest my case.

Good stuff colas.... thanks

Actually, no toe in is not the fastest, as it will have an angle with the water flow. This is not to say that no toe in is bad, it is just that it may work, but for other reasons than added speed. My guess is that the inner fin is thus preset with some positive angle of attack at the beginning of the turn, for instant lift, whereas a fin with more toe-in with "delay" somewhat the fin grip into the turn.

The Witchcraft shaper did experiments with 4WFS to find the best angles for instance, speed being an important factor for sailboards.
I recommend reading http://www.witchcraft.nu/trifin.php
Windsurfing is nice to experiment as you can keep the same position for long, and closely monitor first-hand or with a gopro the wake to see if the side fin leaves a wake or not

Now, for SUP we go slower than sailboards, so the fastest toe-in angle would probably be bigger than the one for sailboards, be we should take into account the water flow on the wave face too (sailboards are ridden less close to the pocket). If you look at the lower drawing in my post, it should probably beg for more toe-in too.

I guess the boards needing the less toe-in could the tow-in boards that go at high speed with not too much rail pressure...

Actually, there is always displacement! It is necessary to provide the upwards force to support the rider, the upwards force must be balanced by pushing on the water below.

This displaced water molecules is what creates the wake.

The faster you go, the more this dynamic displacement takes part in pushing the board up, compared to the static pressure gradient at work with archimedes principles. But you must put yourself in the shoes of a water molecule: when the boards goes over it, it is just pushed downwards. The water is not "ejected" to the rear at all! If the water flow was "straight backwards", this would means the water molecule wouldn't move to the side under the oard pressure, which is impossible of course. Push on these molecules and they will scatter in all directions, there are no "side walls" in the water preventing them to move sideways.

Ben Thouad www.benthouard.com/ aerial photos are a great way to picture it:



You can see the wake of the 4 fins. their wake is obviously divergent, showing the water flow, even at speed. I highlighted the rear quad wakes in red:




"The angled flow in picture #1 arises from board-volume displacement" - No actually it is from the Witchcraft site, analyzing the water movement at sailboard speeds. The second one is from a site explaining the theory behind the bonzer surfboards.

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Piros said..
It's an hydrodynamics party that is going on in that world first pic.

I believe that that is precisely one of Colas' points, yes?

The board displaces water even whilst planing - that water goes in all sorts of directions. Plus, the wave's water and energy are moving at an angle to the board.

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Piros said..
Would it really look any different if the fins where straight as the board is turning and not traveling in a straight line ? I hope I haven't misunderstood your reply.

it would still be the divergent. Water tries to "escape" the weigth of the board crushing it. They will follow the path of less resistance, the sides for the ones closer to it.

Note that I do NOT say that parallel fins do not work!!! I just warn to be cautious of the simplistic "explanations" that have no actual basis.

What I say is that in the assertion "A implies B" in "straights fins are aligned to the water flow (A) THUS they work better (B)"
I say A is false. This then does not mean anything on B.
B may as well be true, based on experience.

I could go on for many false claims such as "hull concaves accelerate water", "winglets on fins lift the tail", etc....

If I was to try an explanation, I would say that if you put a fin (green) in the picture:



You will see that putting it parallel to the water flow (red line) will not "work" as no lift would be provided, so the rider would not have any force to push against. For this, the fin acting like a wing should get some angle of attack relative to the water flow to provide lift. But note that by angling away from the water flow (red line) we are actually decreasing toe-in (angle with the board stringer)
Thus it may well result that for some boards/conditions a good angle with the water flow to provide lift could be by coincidence equal to the angle of the water flow with the stringer... making the fin parallel to the stringer.