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Flat bottom vs double concave hulls
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 2345

PostPosted: Tue Sep 01, 2015 2:26 am    Post subject: Reply with quote

I still claim that my small 15 ft catamaran does plane!

You can feel it lifting upwards over the water surface at speed. (Not talking about flying the windward hull.) The 'step', two thirds of the way back, seems to work as the step in sea-plane hulls does, to unstick it from the water surface.

It certainly feels supported by the rush of water under the hulls, and to not be pressing down to displace its own weight in water. (Like a stone skimming the surface.)
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jingebritsen



Joined: 21 Aug 2002
Posts: 3320

PostPosted: Tue Sep 01, 2015 4:39 am    Post subject: Reply with quote

concave shapes allow a board to stay attached. they do NOT allow for early planing. quite the opposite, they impeded early planing.
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joe_windsurfxxx



Joined: 29 Jun 2008
Posts: 67

PostPosted: Tue Sep 01, 2015 4:41 am    Post subject: Reply with quote

xxx
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waterloo



Joined: 25 May 2012
Posts: 21
Location: Australia

PostPosted: Tue Sep 01, 2015 6:45 am    Post subject: Reply with quote

ittiandro wrote:


On the contrary, my question has a factual purview: I was asking if anybody has hands-on experience with the boards in question ( Exocet Wind SUP, Bic Wind SUP or the old lonngboards) to tell me :
1) if the Exocet SUP has a better subplaning performance than the Bic Wind SUP to justify its purchase for $ 400 more than the Bic.
2) No matter whether Exocet or Bic Wind SUP, should I expect them to perform better in subplaning than a good old longboard like the Mistral Competition SST, aside from its wobbliness, to which I'am getting used very rapidly?

Ittiandro


Have the Exo 11'8, paddled the Bic, have an 80's race board, a modern race board and the Starboard 12'2 WindSUP Freeride...so here's my 2c worth...

1) The Exo is not the board if you just want sub planing - if you want a mix of waves, flat, planing, paddling, teaching and sub-planing then it's perfect. The Bic is unlikely to be much better or worse at sub planing, and definitely not as good at planing or paddling, and probably would be OK to teach with, I wouldn't buy one as I value the benefits the Exo has over it.

2) A 12'6 raceboard has a longer waterline length and generally plan shape, rail shape and rocker that would aid light wind performance, and so will have better glide then the Exo and the Bic. I would not bother taking the Exo out in light wind given the choice.

The 12'2 Freeride on the other hand, it's quite an interesting and different board, when it's too light to rail up the race board, the 12'2 is the go to board..
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techno900



Joined: 28 Mar 2001
Posts: 3520

PostPosted: Tue Sep 01, 2015 8:19 am    Post subject: Reply with quote

jingebritsen said:
Quote:
concave shapes allow a board to stay attached. they do NOT allow for early planing. quite the opposite, they impeded early planing.

You could be right, but here is an observation. A buddy of mine has been sailing Hypersonics for years and loves them. As you know, they have a radical double concave bottom with a small flat section in the middle from nose to tail.

Without a doubt, he gets more planing time than anyone else in our area, including formula boards (Dallas area lake sailing). He sticks to his 133 Hypersonic for winds between 10&20+ knots with sails from 8-11 meters. He weighs about 190 lbs. I am not saying that the radical concave is a plus, just that it clearly doesn't seem to hamper his ability to plane. In addition, almost all his jibes are planing jibes.

I once sailed a friends 105 Hypersonic with a 9m sail (I had a Techno 283 at the time). The Hypersonic with a lot less volume seemed to get up and plane just as quickly as my Techno.
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ittiandro



Joined: 22 Nov 2009
Posts: 251

PostPosted: Tue Sep 01, 2015 9:39 am    Post subject: Reply with quote

konajoe wrote:
OK.

Ittiandro, you looked at the 2 hulls you have. One you like, one you don't. You noticed the differences, and seem to have concluded that the concaves are the difference. They're not. It's the other design factors. You need to move past that for your own good. Again, if the concaves were important for light wind longboards, they wouldn't have stopped using them.



I think that the fact that manufacturers or surfers may have stopped using the double or triple concave hulls is not a sufficient indication, per se, even less a proof, that these hulls did not possess their own intrinsic advantages for sub-planing. You may be right, but, to me, the reason is, rather that subplaning itself and light winds sailing have sort of fallen into disgrace in view of the tremendous rise in popularity of planing and the manufacturers have, of course, followed suit, by abandoning more traditional hull designs viewed as less compatible with strong-winds planing and speed.
As usual, it is the market that calls the shots and, in a sort of perverse way, the manufacturers are those who call these shots by shaping the public’s taste by savvy( and sometimes misleading) advertising.
Bottom line, If I can plane( or almost!) in 12 knts winds on a 20 years old, $ 200 worth, Mistral longboard with a puny 5.6 m2,( which I could never do with an expensive planing board in such winds without at least an 8.5 or larger) I don’t really see what benefits, aside from the lighter and better quality material , these modern “ planing” boards offer…
Yesterday, with 12-15 knts winds, I was sort of amused looking at windsurfers who could barely move with 8.5 m2 sails on their state-of-the-art planing boards, while I was getting very close to planing on my Mistral with the so much deprecated( or at least useless, for some) triple concave hull and a 5.6 m2 sail to boot.
In fact, I could have probably planed if I used my 6.5 m2, but that was quite enough for me. Both sails are modern planing sails a few years old with an array of battens and supposedly requiring strong downhaul. For light winds, these sails are sort of severely castrated. In fact they came back to life only when, against conventional wisdom, the first thing I did was shortening the battens on the luff side to ease rotation and removing the two central battens altogether. This is why I could get by very well with a 5.6 in these winds.
There might certainly be things I don’t know or understand and windsurfing is in many regards an art, rather than a rigid science. We may all act on no more than subjective perceptions, sometimes, me included. This is why I tried to give the debate a bit more of objectivity by recalling Newton and certain basic principles of physics. But still somebody doesn’t seem to agree with them
By the way, I looked at the video. If I am not wrong, their hulls look like displacement-type. These are the sort of hulls ‘d be looking into.

Ittiandro
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dllee



Joined: 03 Jul 2009
Posts: 4617
Location: East Bay

PostPosted: Tue Sep 01, 2015 11:29 am    Post subject: Reply with quote

ConVEX is a round bottom, impedes playing, and sucks the convex part of the bottom of the board down.
ConCAVE adds resistance to planing compared to flat, but can be used to "pop" the board up onto a plane, and it smoothes the ride of the board once planing thru choppy water.
Almost every slalom race board has double concaves ahead of the front straps, on the bottom. They don't want planing IMPEDED.
Hypersonics were the dog of the windsurfing world, slow, and smooth, which is why they died their 5 year span to death. Anything was faster planing, but the reason it did plane was the deep spines and double concaves, and the abliity to hold a giant sized sail.
I said this ON the Starboard forums, was banned by Ian Fox, yet some of the other Starboard team rider's who posted on the forums AGREED with me.
In the long run, Ian was wrong.
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lucashurt



Joined: 06 Oct 2010
Posts: 21

PostPosted: Tue Sep 01, 2015 1:03 pm    Post subject: Reply with quote

What is hard to sail about the board you have? I have two long boards a Mistral One Design and a Fanatic Fox. You know what is the biggest difference between the two, the Mistral has a bigger, stiffer centerboard.

If you care about sub-planing performance, anything wider will also be slower in sub-planing mode. Short and wide is slow when not planing. Look at kayaks, if you want to think about sub-planing, long and skinny is the ticket.

Leave the centerboard down when you tack, and practice the footwork on the beach for a few minutes. Unless money isn't a concern, I'd say don't fall into the trap that a new board will make you a better sailor.

How long is the SST and how wide? Go measure it if you have to. While your looking at your board, put a straight edge transversely across the subtle chines and get a feel for how much concave there really is and whether the bottom is mostly flat, or had a deeper center section. Also make sure if you take experience from someone else that they have sailed something similar to the SST as well as the new boards. It's more important that you compare what you have now to the two new boards, than to compare the two unknowns to each other.
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isobars



Joined: 12 Dec 1999
Posts: 19378

PostPosted: Tue Sep 01, 2015 1:38 pm    Post subject: Reply with quote

lucashurt wrote:
Unless money isn't a concern, I'd say don't fall into the trap that a new board will make you a better sailor.

Or even if money is not a concern. I don't buy and own a fleet of old wave boards because they're cheap; I do it because I have found almost zero modern boards that do what I want to do. New and different do not inherently mean better.
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techno900



Joined: 28 Mar 2001
Posts: 3520

PostPosted: Tue Sep 01, 2015 2:38 pm    Post subject: Reply with quote

Anyone getting the feeling of chasing one's tail for several days? I don't think it's possible to share any more information without being overly repetitive.

I should also say that it has been somewhat entertaining.
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