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Slippery bottom shape for 14'

Started by SUPflorida, January 18, 2016, 12:23:54 PM

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yugi

^ yep. Concaves, lots of concaves, came and went in windsurf boards.

I really notice the pendulem swing in new sports and try to stick to the middle ground.

blueplanetsurf

Thanks for posting that DW.  I really like flat bottoms, they are fast, stable, create a lot of lift and are neutral when turning.  The old C4 Waterman 14' Vortice XP boards had deep double concaves, which at the time seemed like a great idea but compared to modern downwind raceboards with flat bottoms or very subtle contours they are pretty awful.  I would stay away from deep concaves and instead focus on getting the rocker line just right. 
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

willi

 From DW > I tested progressive rocker versus constant curve.
Hi DW --- could you expand on this just a bit for my old slow mind --
I have used a constant curve from about center of the board or just a bit forward to the tail for that section of the rocker and the same concept for the nose -- am I right the "progressive" is more curve as the rocker approaches the nose and tail -- ?????
thanks for the post you all this is a great thread -

aloha

willi

yugi

Quote from: blueplanetsurf on January 28, 2016, 04:34:10 PM
Thanks for posting that DW.  I really like flat bottoms, they are fast, stable, create a lot of lift and are neutral when turning.  The old C4 Waterman 14' Vortice XP boards had deep double concaves, which at the time seemed like a great idea but compared to modern downwind raceboards with flat bottoms or very subtle contours they are pretty awful.  I would stay away from deep concaves and instead focus on getting the rocker line just right.

I so agree on principle and seeing fads fail the tests of time. Yet I still am really intrigued by this years SB Allstar. Haven't heard a great deal of feedback other than so stable one can go a size narrower. Wondering how that's is working. When tipped is the rockered chine acting like a single rockered "hammock" like stable DW shape?

Sizing down is width is definitely faster and better for paddling so something is going on there.

SUPflorida

In regards to the SB Allstar...is it their take on the Infinity Black Fish ST? or the other way around? Seems both boards have a lot in common...not exact, but both seem to have a rounded entry, to flat to a single concave that gets progressively deeper and extends all the way to the tail. They both have the chines outside the concave. SB took the attribute to a bit of an extreme...history has shown in the vast majority of cases, that that more subtle uses of these type bottom tweaks are more advantageous. I own neither brand so I don't have a dog in this fight.

Dwight (DW)

Quote from: willi on February 01, 2016, 07:06:17 PM
From DW > I tested progressive rocker versus constant curve.
Hi DW --- could you expand on this just a bit for my old slow mind --
I have used a constant curve from about center of the board or just a bit forward to the tail for that section of the rocker and the same concept for the nose -- am I right the "progressive" is more curve as the rocker approaches the nose and tail -- ?????
thanks for the post you all this is a great thread -

aloha

willi

You are correct from my point of view. Just beware, when marketing people create their BS, use of the word progressive could mean, progressive design, cutting edge, etc and not what an engineer would mean.

SUPflorida

Quote from: DW on January 20, 2016, 04:53:21 AM
I haven't done 14 footers in at least 5 years, so I'm not up to date, but here are the few bits I learned shaping them.

- The narrowest board was the fastest. I kept adding tail width to allow me to stand on narrower boards. My last board was darn near parallel in template and my fastest board.
- I tested progressive rocker versus constant curve. Progressive paddled faster, but felt speed limited compared to constant curve. I was building boards for down winding, so mine did plane up. For something that will never plane up, I'd go progressive curve.
- Even though everyone knows displacement is the fastest paddling hull, I never considered it due to stability issues. Flat was as close to displacement as I wanted to go.
- Deep fins are slowest, so I'd follow Larry Allison's development path and go short multi-fin. Larry is doing a mid ship fin. It might be what a flat bottom needs to fly straight.

DW ...how narrow did you go with your last 14 (overall width) and how wide was the tail?

I keep re-reading all the comments trying to keep an open my mind as to what's really being communicated.

Dwight (DW)

26 wide. Tail width I don't recall. It was probably 5 years ago.

PonoBill

To sum up then, flat is fastest until you want to do something other than go straight in no wind.


FWIW, we called the old Vortice the Tortice.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

yugi

^ excellent summary

Likewise my mid 80's Cobra radical 260 and 290 windsurf boards with major concaves were a dream to turn but ended up being way slow compared to other boards.