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boardsurfr
Joined: 23 Aug 2001
Posts: 1266
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 Posted: Tue Aug 11, 2015 10:06 pm Post subject: |
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| ittiandro wrote: | | If it is not relevant to them, to which boards is it relevant?! |
Maybe you should read the rest of my post, instead of getting hung up on the first sentence. The same actually applies to this post - check the bottom for a (repeated) answer to your question.
| ittiandro wrote: | | When I speak of longboards, however, I mean the older, true, longboards of yesteryear with a more or less pronounced V-shaped displacement-type of hull. |
You are using a non-standard definition of "longboard", so perhaps you should say so right away. Longboard racing is alive and well in many parts of the world. Up until a few years ago, it has been mostly dominated by F2 Lightnings and similar boards from the late 80s and 90s, which have a mostly flat bottom (if you ignore double concaves etc). Recently, the older boards have largely been eclipsed by the Starboard Phantom 377, at least at the highest level of competition. But the same ideas apply - fast in light wind but made for early planing.
The points that Dan mentions are much more relevant to their speed. A theoretical hull speed, however, is pretty irrelevant since the boards can actually plane, and because they can transition very smoothly from displacement mode to planing mode, with intermediate states (and things like planing on the daggerboard when going upwind) that are absent for shortboards.
| ittiandro wrote: | | Bottom line, no matter in what sense the hull speed discussion is irrelevant to you (perhaps too academical?) |
I'll have to assume that you are trying to be funny. You used the most primitive of the hull speed formulas. Your formula assumes that boat weight has no relevance to hull speed, which is bloody nonsense. More weight at the same length means more displacement and large bow and stern waves, which limit "hull speed". The formula in the article that I linked to at least took weight into account, and gives "hull speeds" that are substantially faster for windsurf gear. It is still very simplistic, though, since it ignores all form factors.
One big difference between older longboards like the original Windsurfer and the (slightly) newer longboards like the Fanatic Cats and F2 Lightnings is how well the boards plane; how controllable they are on a plane; and issues like water release that influence top speed. Most longboards (excluding perhaps D2 boards and maybe the Superlight) transition seamlessly to planing somewhere near their theoretical "hull speed", so what relevance does hull speed have? It is primarily a measure for boats that cannot plane.
Where the concept of "hull speed" might be useful is when it comes to shortboards made for planing. Shortboards do have a quite noticeable maximum non-planing speed, and a significant gap between it and the minimum planing speed. In "hull speed" boating terms, you need a lot of energy to climb up the bow wave. In practice, it makes it harder to learn how to plane on a windsurfer, and it is a darn good reason to learn to pump. Understanding this, and acting accordingly, can make the difference between planing and not planing in marginal conditions. |
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techno900
Joined: 28 Mar 2001
Posts: 4161
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| Posted: Wed Aug 12, 2015 7:43 am Post subject: |
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itt said: | Quote: | if you agree that there is such a thing as a hull speed in the older longboards, I wanted to know if the hull speed represents the maximum speed one can attain in subplaning mode, as the person I quoted thinks, no matter the size of the sail or if it can be substantially exceeded
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I think the question has been answered in a variety of ways, but since "older longboards" include a wide variety of hull designs, there really is no answer to your question. That is unless you define exactly what hull design you wish to model. |
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cgoudie1
Joined: 10 Apr 2006
Posts: 2599
Location: Killer Sturgeon Cove
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| Posted: Wed Aug 12, 2015 10:00 am Post subject: |
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Greeting ittiandro,
You can derfine longboard however you like, but the standard
windsurfing definition of longboard is a board with a centerboard
(or daggerboard). So a "true" long board is something like an Equipe II,
but so is a techno 293 with a center board. One will get over it's bow
wave and transition pretty smoothly out of displacement hull mode
(and off the the function of your formula), and the other will transition
dramatically away from your formula.
In the case of a Kona, being a long board, the designers may have
been using the surfing term which is more of an actual length (8 footish
or more) with a different planform than a surfing short board.
Some Konas do have centerboards, so they are a longboard by
both definitions.
;*)
-Craig
| ittiandro wrote: | | boardsurfr wrote: | | The hull speed discussion is completely irrelevant to longboards. . |
I don’t quite understand why you say that the hull speed discussion is completely irrelevant to longboards. Perhaps academical or theoretical, but not irrelevant. If it is not relevant to them, to which boards is it relevant?!
There might be some confusion in the terminology here: some modern boards, like my own Bic 293 are( perhaps misleadingly) called longboards because of their length and their centerboard, but in reality they are still shortboards because they are flat-bottomed. Definitely the hull speed discussion is irrelevant to these “ longboards”: by being flat-bottomed, they simply don’t have a hull speed.
When I speak of longboards, however, I mean the older, true, longboards of yesteryear with a more or less pronounced V-shaped displacement-type of hull. Contrary to what you said, the hull speed discussion is absolutely relevant to them AND ONLY TO THEM precisely because of their hull, which has all but disappeared from the modern boards. Even the much vaunted and certainly excellent Kona 1, marketed as a longboard, is as close as you can get to a real longboard, but not quite, because the hull is still almost flat, in spite of the clever step tail.
In fact, a friend of mine has tested both and he found that that the Mistral Equipe still glides better and faster than the Kona 1 in sub-planing mode. Not difficult to see why: if you put a Mistral Equipe and a Kona 1 bottom up side by side, you will notice the difference in the hulls : the Mistral has a rounded, slightly convex hull with longitudinal ribs, which minimize the contact with the water, hence the drag. Furthermore, this contact with the water is further reduced because between the longitudinal ribs the hull is slightly concave length-wise. It looks more like a watered down sailboat’s hull. Even my kayak, which tracks pretty well, has the same ridges and convexities, which make it glide a lot better and more effortlessly than the completely flat-bottomed lake canoe I once had. The Kona 1, on the other hand still has an almost flat-bottomed hull.
Bottom line, no matter in what sense the hull speed discussion is irrelevant to you ( perhaps too academical?), if you agree that there is such a thing as a hull speed in the older longboards, I wanted to know if the hull speed represents the maximum speed one can attain in subplaning mode, as the person I quoted thinks, no matter the size of the sail or if it can be substantially exceeded
Ittiandro |
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bred2shred
Joined: 02 May 2000
Posts: 989
Location: Jersey Shore
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| Posted: Wed Aug 12, 2015 11:14 am Post subject: |
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| ittiandro wrote: | | boardsurfr wrote: | | The hull speed discussion is completely irrelevant to longboards. . |
I don’t quite understand why you say that the hull speed discussion is completely irrelevant to longboards. Perhaps academical or theoretical, but not irrelevant. |
It's already been discussed, but the reason the hull speed is irrelevant when discussing long boards is because even long boards can get onto plane (to some degree). The hull speed equation really only applies to keel boats which can not climb out of their own bow wave (i.e., they can't plane). Once the board, or boat, or any type of hull climbs over it's bow wave and starts planing, all of the displacement math goes out the window.
In essence, an efficient displacement hull (think catamaran hull) is the exact opposite shape of an efficient planing hull (think Formula board). So in light wind, the longboard with it's relatively high length to width ratio will walk away from a Formula board. Once the Formula board can pop up onto plane it's a different story and the long board doesn't stand a chance.
sm |
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konajoe
Joined: 28 Feb 2010
Posts: 517
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| Posted: Wed Aug 12, 2015 12:04 pm Post subject: |
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Hi Ittiandro!
I wonder what other stuff your source has been telling you? Now, you'll have to question everything he's told you.
Whitevan gets my vote. That was my understanding. That formula only applies to hulls not capable of planing.
There was a recent comment about longboards planing 'to some degree'. I think folks would be surprised to find out how poorly formula boards do on gps-speedsurfing. Max speed on longboards is every bit as fast. |
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ittiandro
Joined: 22 Nov 2009
Posts: 294
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| Posted: Wed Aug 12, 2015 12:35 pm Post subject: |
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| boardsurfr wrote: |
You are using a non-standard definition of "longboard", so perhaps you should say so right away.. A theoretical hull speed, however, is pretty irrelevant since the boards can actually plane, and because they can transition very smoothly from displacement mode to planing mode, with intermediate states (and things like planing on the daggerboard when going upwind) that are absent for shortboards.
I'll have to assume that you are trying to be funny. You used the most primitive of the hull speed formulas. Your formula assumes that boat weight has no relevance to hull speed, which is bloody nonsense.
Most longboards (excluding perhaps D2 boards and maybe the Superlight) transition seamlessly to planing somewhere near their theoretical "hull speed", so what relevance does hull speed have? It is primarily a measure for boats that cannot plane.
Where the concept of "hull speed" might be useful is when it comes to shortboards made for planing. Shortboards do have a quite noticeable maximum non-planing speed, and a significant gap between it and the minimum planing speed. In "hull speed" boating terms, you need a lot of energy to climb up the bow wave. In practice, it makes it harder to learn how to plane on a windsurfer, and it is a darn good reason to learn to pump. Understanding this, and acting accordingly, can make the difference between planing and not planing in marginal conditions. |
I have to credit you for explaining in one short paragraph why the hull speed is relevant only to non planing crafts and not to windsurfing boards, because they can plane, often at close the theoretical hull speed.
This is something I understand less, because, if the theoretical hull speed ( according to my “ primitive” formula, of which later) is about 5 knts/hr, I cannot bring myself to believe that one can plane a board at such a low speed unless he or the board has no weight ( or almost!) and sails with a..12 m2 sail or the wind is far above 6 knts. When you say quote Most longboards (excluding perhaps D2 boards and maybe the Superlight) transition seamlessly to planing somewhere near their theoretical "hull speed"unquote , I must ask YOU, for clarity sake, what you mean by longboards and which ones are these wonder boards I am afraid there is a bit of a hype here.
You also say that I use the most primitive formula for hull speed, because it does not take into account the weight of the craft. You are theoretically correct, however the weight factor is relevant only to non-planing crafts because they have by nature an extremely wide range of weights.. Certainly the hull speed of a 15 ft/150 lbs sailboat is quite different from that of a 50 ft yacht or a supertanker, but becomes irrelevant in computing the hull speed of windsurfing boards: their weight and their weight range is relatively small, unless you go to extremely light( and expensive) materials, like carbon. An older longboard of the 80’s /90’s weighed about 15-16 kgs, almost the same of a Kona 1 today . My Bic 293 is about 15 kg as well. So what relevance does it have to inject the weight into the Hull speed equation? We are always around 5 knts, afterall !
As to your remark that I am using a “ non-standard “ definition of “longboard” and that I should have stated at the onset what I meant by it, I should point out that I didn’t know that there was a “standard” definition (who sets it?) but what I meant by “ longboard” should have been clear in my context, since I mentioned the Mistral ( Equipe) and similar boards having a V-shaped displacement-type of hull . Frankly, I don’t even recall that there have ever been flat-bottomed longboards in the 80’s and 90’s. My “non-standard” definition of longboards couldn’t but refer to the ones having the classic V-shaped displacement-type of hull.
My original question has become a bit clouded over by a wealth of technical details shaped by what I call the planing bias. This is not, by choice or necessity, the only universe in which all windsurfers navigate..
Personally, I don’t have either the skills to plane in 6 knts winds nor the money to buy more performing equipment nor the power to change the weather conditions nor a…more planing-friendly weight.
I am confined to a sub-planing environment and , no matter what the planing gurus tell me, the OLD longboards ( now you know what I mean) are still far better in sub-planing than the shortboards I have have had and the one I still have. The other day a friend of mine let me try an OLD Mistral Equipe in about 10-12 knts: as soon as I set my foot on it, the board glided away effortlessly ( he could even plane it) , whilst my Bic 293 which I sailed on right after, was, as usual standing still..This difference in performance may well be due partly to my technique, but it is also based to a great extent on the inescapable laws of physics, if you look at the two hulls..
Finally, with all due respect, if any debate implies a difference of opinion, arguments don’t become more convincing by being bombastic, ironic or using words like “bloody nonsense …” and the like or surmising that one is “ trying to be funny..”
Itiandro |
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techno900
Joined: 28 Mar 2001
Posts: 4161
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| Posted: Wed Aug 12, 2015 1:06 pm Post subject: |
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If someone wants to see what was on the market in the 80's and 90's, here is an interesting resource. Many of these were only available in Europe, but there were many, many longboard planing hull boards. Just look at the foot strap locations to see what was designed to plane.
https://hitthewave.wordpress.com/2011/05/02/windsurfing-brochures-ads-80s-90s/ |
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isobars
Joined: 12 Dec 1999
Posts: 20935
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| Posted: Wed Aug 12, 2015 1:11 pm Post subject: |
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| I doubt any WSer would call an Equipe a "displacement" hull, despite its V. It's intended to plane, with slogging being attributed mainly to operator error, including rigging too small or not grabbing the Superlight instead. |
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coachg
Joined: 10 Sep 2000
Posts: 3550
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| Posted: Wed Aug 12, 2015 1:34 pm Post subject: |
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| konajoe wrote: | | I think folks would be surprised to find out how poorly formula boards do on gps-speedsurfing. |
Actually I don't think people would be surprised. Hi gps speeds are small finned, narrow boards. Far from a formula shape.
Formulas are know for high upwind & deep downwind angles on a plane. Great for course racing in medium winds, especially with very long reaches.
Coachg |
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konajoe
Joined: 28 Feb 2010
Posts: 517
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| Posted: Wed Aug 12, 2015 1:42 pm Post subject: |
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Hi Ittiandro!
I'll take a crack at some of your questions. I think your getting hung up on making planing and subplaning a sudden transition. If you looked at a 30ft sailboat, it's waterline would be the same from zero up to it's maximum speed. Not so with that Equipe or your 293 or any board. Your waterline will change with speed. So, think of subplaning, slow planing, medium planing, full planing. Does that help?
Things get really nutty if you get hung up on that waterline formula. Think about it. You get a small puff, and the attitude changes to a little more nose up. Oops, your water line just got shorter, so the max speed just went down.
You're trying to learn this stuff, and you trusted someone who gave you some bad info. Happens to all of us, no matter what we're trying to learn.
Last edited by konajoe on Wed Aug 12, 2015 2:38 pm; edited 1 time in total |
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