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Old 28th December 2006, 02:32 PM   #11
SIN909
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Default RE: new vs. old slalom shapes

Hi steveC,

My previous slalom board was an ML as well. Great board also. I think it was built around 2001 and I used it until last year. Fin-wise, I found that my new board needs a larger fin than my old board given the same conditions. On my old board I was mostly using a 28cm falcon or 30cm goldwing. I think the narrower tail of the older board was happier with a smaller fin. I think the newer board with the wider tail can handle the power of the goldwing better than the old narrower tailed board. To slalomguy I would say the newer boards do need larger fins. For the new ML board I have been using 30cm, 32cm and 34cm goldwing with 6.0 & 6.5 sails. I don't use bigger than 32cm with the 6.0 but sometimes use the 32 with the 6.5. I'm beginning to think the 32 will be my most important fin for racing. I have a 5.5 which I haven't used much but unless it was really nuking I would probably be on the 30cm with it. I would like to see how the 28 falcon goes with the 5.5 when it's really windy. I also used a 24cm vector for the speed event this year up to a 6.3 sail and it felt good. Improved my top speed by 3 knots over last year when I was on the older board and regular sized fin but still on the Nitro4. I think this setup can go a lot faster, seeing that the winds at the speed event this year were on the mild side. Hard to say how much was the fin and how much the board. If you are racing let me know if you have figured out what fin size to use. I am sometimes torn between going smaller for the extra speed it gives or going bigger for the starts, holes and gybe marks.
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Old 29th December 2006, 03:13 AM   #12
Ian Fox
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Default RE: new vs. old slalom shapes

With the wider boards you'll mostly find easier, more practical, more accessible top speed ~ and more often. That's to say the newer style ride can be less technical, less demanding and often more consistant = a better chance (on average) to be "fast", c/w pure theroretical top end Vmax board that have some very wicked but narrow performance curve..

For g.e.o., it's no doubt efficiency is influenced by tail and fin dimensions, but the aspect ratio of the planing surface actually gets higher (and more theoretically efficent) as the tail gets wider and the planing surface corespondingly shorter - it's the control and longitudinal stability that are (very real) limiting factors in exploiting this. For sure, ride sensation is an issue - it's hard to beat the feeling of flying across the water on a ski rather than a door - but once we got that door to turn and maintain control it can still be potently fast !

Cheers ~ Ian
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Old 29th December 2006, 04:53 AM   #13
geo
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Default RE: new vs. old slalom shapes

Ian,

I am not sure that efficiency increase can compensate wetted surface increase. A short/wide tail will vary wetted surface greatly with trim variations, while a long/narrow one will vary comparatively less. As a matter of fact, boards built for top speeds are narrow, not wide. Plus, I am not perfectly sure about how reduction of tip effects can compensate increase of trailing edge effects; were we talking about a wing travelling through air, I would totally agree; but I confess my ignorance about what happens at the air/water separation surface when a board skims over it.
Of course I totally agree about wider boards being fast easier and more often.
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Old 29th December 2006, 09:50 AM   #14
steveC
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Default RE: new vs. old slalom shapes

While I can honestly say that I come up short on the technical science of things (although I like the input and perspective), from a practical point of view, I think the balance point between wide and narrow tail board performance has a lot to do with overall length of the board too. With the shorter lengths in modern designs, the lever action that can be associated with the front section of the board (a lessening of the possible flyaway factor), contributes greatly to control in tough conditions. Matched with the magic of how a shorter rocker flat in wider tail concepts will ride high, and also facilitate jibing ease and planing power through transitions, it doesn't surprise me that folks are more enthusiastic with more current designs.

Thanks SIN909 for your very useful comments concerning fins. Living in California, I have to admit that my conditions fall quite a bit short of those in Maui. As a result, I've tended to go with larger fins (I used 34 and 36ccm Goldwings) on my older slalom board, with the 34 being my favorite. I think that I might be able to successfully continue on these fins, and maybe the 36 will gain more favor. Still though, I would like to have a fin for higher winds, and I'm thinking that a 32cm Falcon would be the right pick. For speed-type conditions, I also have a couple of Wolfgang Lessacher's 27cm Hyper Duo and Le Wo Duo asymmetrical carbon fins to experiment with.

However, being an older guy, I doubt any really super stellar results. Still, it feels great to push the margins a bit, and I love being powered up and moving. Mike's boards really excel under pressure. Once I get the Falcon and play with it a bit, I'll offer my thoughts.

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Old 30th December 2006, 02:51 AM   #15
Ian Fox
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Default RE: new vs. old slalom shapes

Hi g.e.o,

It's exactly what I'm saying with my comments above ;
" it's the control and longitudinal stability that are (very real) limiting factors in exploiting this"
- if you can't maintain longitudinal stability, the board will pitch and the planing surface will vary significantly in length (and this area and A/R) as the width over the length of the variance won't change significantly.

Then, as you comment, we have the practical reason for longer narrow board, however the reason for my comment above was to explain the difference between what is theoretically (??) efficent and what works in practice.

This might not seem a big deal, but if you really look inside what is happening with this current trend of new (short wide) vs old (long narrow) slalom shapes, then A/R actually does play an important part (but again, not in isolation) but without a steadier overall trim/ride
(fore/aft , longitudinal stability), any theoretical gain in "efficency" can be swallowed up in practice.

But we have a better trim, we have a planshape offering more efficent (A/R) planing area and we exploit that within practical gains.

Within speed boards (something I have close association with) the trend is again driven by the same theory; when you really study closely the design of the new modern speed boards, you can see a very distinct trend to move more surface(planing) area aft (again, within reason and practical limitations of control ). Yes, the boards are still "narrow" and small but the area is moving back (A/R inreasing) and the boards are working better.

Interesting to note that true speed boards used in superflat* water actually suffer less longitudinal stability / trim issues than (say) a hi wind slalom operated at much slower (relative) speed in rough open water. Light wind slalom (or FW) boards usually operating in "flatter" conditions (due to lighter winds, less chop) also suffer less longitudinal stability / trim issues than the hi wind slalom at speed in rough open water ; So you can see the trend is that the two "extremes" (lighter wind and speed) can explore and exploit the A/R efficency easier/further than the hi wind slalom design.

Looking (in finer detail) across the iSonic product range, you can see the development of this trend vs board size (or intended usage range) subtly but clearly in combination with other design factors
(like the ability to still be able to turn a slalom board at speed).

Hopefully this helps explain a bit more of what is really going on in both theory and practice with the newer boards.

Cheers ~ Ian

*keeping it simple for the discussion but noting at hi speed conditions, the water is never superflat due to surface chop, but the nature of this chop (+ subsequent trim) issues is quite different to open water hi wind chop.



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Old 30th December 2006, 04:19 AM   #16
slalomguy
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Default RE: new vs. old slalom shapes

Ian,
Is it fair to say that the new wide short boards plane quicker and accelerate faster especially in moderate slalom conditions (7m sails) than the older narrow long boards?
But that the top end speed of the older shapes is greater?
So in a slalom race(again with 7m sails) with many jibes a wider board could easily win due to its ability to carry speed through the jibes and accelerate quickly.
In hi wind slalom conditions(5.8 sails) the advantage of the wider board diminishes as control in the choppy conditiond suits the narrower board and speed through the jibes is less of a problem for the narrow board.
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Old 30th December 2006, 04:21 AM   #17
slalomguy
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Default RE: new vs. old slalom shapes

Ian,
Is it fair to say that the new wide short boards plane quicker and accelerate faster especially in moderate slalom conditions (7m sails) than the older narrow long boards?
But that the top end speed of the older shapes is greater?
So in a slalom race(again with 7m sails) with many jibes a wider board could easily win due to its ability to carry speed through the jibes and accelerate quickly.
In hi wind slalom conditions(5.8 sails) the advantage of the wider board diminishes as control in the choppy conditiond suits the narrower board and speed through the jibes is less of a problem for the narrow board.
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Old 30th December 2006, 10:51 AM   #18
Ian Fox
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Default RE: new vs. old slalom shapes

Hi Slalomguy,

Q1 = Is it fair to say that the new wide short boards plane quicker and accelerate faster especially in moderate slalom conditions (7m sails) than the older narrow long boards?
A1 = Yes, in general it is fair to say that and especially around 7m.

Q2 = But that the top end speed of the older shapes is greater?
A2 = Not so simple; in fact (as discussed above) it's possible both in theory and practice for short wide (high A/R) designs to also offer top end advantage (c/w accel or mid jibe speed). This is most noticeable in smoother conditions (light to moderate slalom conditions and speed sailing on flat water). On the other hand, in rough open water, a slightly lower A/R (and less theoretically efficent) design could have top speed advantage.. But it would be an incorrect generalistation to say the older shapes have greater top end in all circumstances.

Q3 = So in a slalom race(again with 7m sails) with many jibes a wider board could easily win due to its ability to carry speed through the jibes and accelerate quickly.
A3 = Yes. And more, because we have significant testing of boards around the 7m size (~ iS101) which can show higher point to point open water speed, a lot more than just "effective speed" around marks and thru jibes etc. If you add in further real world variables such as improved rideability (ability to push the board hard to achieve higher top and avaerage speeds), relative ability in patchy or inconsistant conditions plus "upwind" ability (when required), then the overall result out on the water is pretty convincing.

( Practical side bar here : I can't think of anyone in our team who would now choose the classic benchmark Sonic 100 in that range over the iS101 for anything like slalom racing in 7m conditions)

Q4 = In hi wind slalom conditions(5.8 sails) the advantage of the wider board diminishes as control in the choppy conditiond suits the narrower board and speed through the jibes is less of a problem for the narrow board.
A4 = Yes, the advantage diminishes, however mainly because of rough water interference with maintaining an efficent fore/aft (longitudinal stability) trim across serious (hi wind) chop at high speed, rather than speed thru jibes etc.....
iS122 (for example) has a rather unreal hi speed pivotal jibe ability for any 12xLt or 75cm slalom style board, but again acknowledging a slightly different style or technique being optimal to that of the drawn out scalpel carve of a narrow, long slalom. In fact, what we found testing iS101/105 vs S85/95(S100) was that even when solidly overpowered in a straight line, the iS could still offer some advantage (suprisingly) in the jibe (with minor techique/style mods to suit) by carrying more power into and thru the jibe, with less precision required than a long narrow.
(advantages in real world use, especially the hustle of tight short leg slalom racing are pretty obvious). Now again, that doesn't make long narrow obsolete (esp for hi wind open water) but it does show the short wide advantage can encroach (in practical use) further into long narrow territory than maybe theorectically optimal.
(final footnote here is the short wide in question better have a good jibe, or this peripheral advantage doesn't exist...)

Cheers ~ Ian
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Old 31st December 2006, 08:29 AM   #19
steveC
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Default RE: new vs. old slalom shapes

You know, that thing that I think needs to be highlighted here is that width cuts across the product line. Sailboards designs are generally wider overall. Yet, still the high wind stuff is markedly narrower than the light wind stuff. Designer/builder focus is truly on wider and shorter designs, even when it comes to ultimate speed shapes. The narrower shapes of the past have found a conflict with the updated design influence in the current market, for good or ill. Frankly, in my opinion, its a good thing. While many of us still find value in the older designs, time moves on, and we have to adjust. In the wave of new thought and technology, it's an unstoppable push. Look at computer/software technology. Just because some are happy, that doesn't change the push of new thought.

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Old 19th January 2007, 07:40 PM   #20
scotty
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Default RE: new vs. old slalom shapes

Hey hope you guys don't mind me resurrecting this thread, found it quite interesting and useful. We've had no wind for ages, so I've had to take up skateboarding again!

Anyway last year I got my new 7.2, 8.4 RS-S sails to use on my old Z-26 Protech and boy those sails work well! However, I'm noticing the 7.2 is probably a bit small as I find I'm getting a bit of nose lift, despite the mast foot position being forward enough to make the foot of the sail drag a bit much on the deck of the board. Granted I am using a CK95 mast, which will hopefully soon be replaced with an X9. I'm finding the CK95 only seems to let the sail twist to a certain level on the leech and then no matter what it had an abrupt step.

So I'm planning to get a 6.2 and 5.4 RS-"7" and combine that with the Isonic 87 and possibly the new JP 69 S3. What I was curious was whether anyone has tried using the 7.2 RS-6 or equivalent on the 87 Isonic, and what was the general outcome? I really would prefer this board over it's bigger brother, who knows prehaps next year I'd go for a bigger I sonic?

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