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Floyd
3rd October 2007, 07:32 PM
How much does rider weight influence sail range for any given board ???


Eg)In Acid range the 80 is quoted as 3.5 to 5.5. I`m looking for a board to use with sails from 3.7 to 5.4 . It looks perfect.However my weight is 102kg; so I suspect 80 will be too small.The 86 with the 3.7 is below its bottom advised limit.Pretty sure everyone will say it will be ok and I`m sure it will but if I was using sail range as a guide to purchase I should be buying the 80?!(Which I`m not)

To be fair I`ve only used 3.7 twice in last 2 years so boards performance at this size is pretty irrelevant but I think you see point I`m making.

ie)My weight suggest I should be getting k96(or similar); my sail usage suggests A 80 ????

Screamer
7th October 2007, 06:48 AM
Manufacturer's quoted range won't work for all sailor's weights and in all conditions. I believe most manufacturers stretch this range a bit (I mean, who would choose a 75cm wide iSonic122 to sail with a 6.0 ?)
A 60 kg sailor could get away with a max (5.5 or even larger) sail on a particular board, whereas you couldn't @ 102 kgs. But then again, when it's howling, there's no way a lightweight can hold things together with a 3.7 (on the same board) the way you could.
Btw, you are asking an awfull lot of one board if you want to use it with a 3.7 and a 5.4 (luckilly 3.7 days are really rare as I understand).

Ola_H
7th October 2007, 03:20 PM
Rec sail sizes re for "medium weight" sailors. So, as you suggest, you need to be on a bigger board. On the other hand, even 5.4 weather for you will mean rather windy day (with corresponding rougher water state) so you should not go to big either. Personally I think the K96 indeed will be the best compromise. It is a real wave board shape, but with a wider tail and wider shoulders. The board also has pretty good control, and I think 4.5 will still be within the sweet spot for you and 3.7 will be fairly OK too. You might want to add an extra fin or two to squeeze the biggest possible range out of the board.

Floyd
7th October 2007, 05:00 PM
Hi Screamer/Ola
Thanks for replies.
On question of my board choice I tried (had) a k95 and found it only marginally better (if any)than present 105 litre board in 5.4 weather and it was a bit big (even with my weight on it) in 4.7. Hence why I`m thinking A 86 (or k89).Present board goes down to 5.4 fine; so I agree with Screamer ie)New board needs to work below 5.4. (ie 4.7 and 4.2 and occasionally 3.7)
On a more general note point I was trying to make was could manufacturers be more specific with weight and sail range relationship. If I chose board from sail range guide I`d be buying an Acid 80;it has in theory perfect sail range for my smallest board.If I chose it purely on volume(width) I`d be buying a k96.

Suspect most 95k+ sailors are in similar dilemna.

Putting it another way ; what is recommended sail range for PA 86 with 102k rider ???

davide
8th October 2007, 02:32 PM
.
Putting it another way ; what is recommended sail range for PA 86 with 102k rider ???
Do keep in mind that sail size is also roughly linearly related to weight and in respect to a 170-80 pounds sailor you can hang on more sail. If you sail mostly in the 15-20 miles/hour range (call it a 6.0 for you, call it a 5.0, on a wave board, for me at 150 pounds) you will need a 90-100 liters board. If you sail in the 20/25+ miles/hour range (5.0 and below) you can use a 80-90 liters board. That is ... an Acid 86 or the Kombat 89 might be sort of ok in your marginal 5.5 conditions but fine in powered up 5.5 or when you use a 5.0 and below ... I suppose :)

Floyd
8th October 2007, 03:15 PM
Hi Davide
Not sure sail size and weight are linear.Infact pretty sure they aren`t.
In lightish winds;or possibly in a particular given wind they could be.But as wind increases the difference in sail size has got to diminish.
A doubling in windpower quadruples the amount of energy/power available.
In lightish winds I find I need about a metre more than average (ie I`ll have a 7 on ; 75k mates on a 6 but in strong winds (ie 4 metre ish) I can get going with pretty much same size sail .
I`ve pretty much got it sorted for sail sizes/wind. But struiggling a bit on smallest board choice.
Agree with you re Acid 86/K89 though.
Thanks for repy.

Ray Timm
8th October 2007, 05:06 PM
I would go for the PA86 at your weight. A good friend of mine who weighs 104 kg uses it with everything from a 5.8 to a 4.5. My PA80 feels too small for him unless the wind is up to the point where he needs a 5.0. Compared to my 84 kg, my friends who are over 100kg tend to use the next sized larger wave board or B/J board and at least one size larger sail until the wind is up over 28-30 knots when we can end up on nearly the same gear although I prefer boards closer to 70 liters when the wind is really strong.

davide
8th October 2007, 10:23 PM
Hi Davide
Not sure sail size and weight are linear.Infact pretty sure they aren`t.

Agree with you re Acid 86/K89 though.
Thanks for repy.
About linear. Wind force is exponential but locally a linear approximation is effective.

Try: 0.65 x Weight (Kg) / wind speed (meters/sec)

For example, at 8 meters/sec (15.5 knots) I am on a 5.5 square meters sail, at 12 m/sec (about 23 Kn) I am on a 3.7 that underestimate a bit the size but is not bad as an estimate.

Floyd
8th October 2007, 11:43 PM
Hi Davide
See your reasoning but I think you are doing what we all do at times; ie bend the figures a bit here and there and then say well it nearly fits.
First of all from an energy point of view
A 12m/s wind contains root 2 (1.41) times 50% (ie difference in linear speed) as an 8m/s one.(ie a 12m/s wind is 50% faster than an 8, so it contains about 70% more power.)(ie x 1.7 )

In 15 knots I would be on around a 6.5 (or even 6.2)
In 25 above figures would give me a 4.2 (ie 6.5/1.7)(for equal power ???)
Which is about correct.(Id be getting overpowered with 4.7 and thinking about 4.2)
This model would also show sailors coming towards similar sized sails as wind gets stronger. (which is one of few facts we have.)

PS Your equation gives me an 8.2 metre in 15 knots ?? and a 5.5 in 25. (Both out, my biggest sail is 7 and I sail from around 13 knots)

It just cant be linear when doubling wind quadruples power ! Its what makes fin and sail choice so interesting.
Take care.

davide
9th October 2007, 12:05 AM
Hi Davide
See your reasoning but I think you are doing what we all do at times; ie bend the figures a bit here and there and then say well it nearly fits.

In 15 knots I would be on around a 6.5 (or even 6.2)
In 25 above figures would give me a 4.2 (ie 6.5/1.7)(for equal power ???)
Which is about correct.(Id be getting overpowered with 4.7 and thinking about 4.2)
This model would also show sailors coming towards similar sized sails as wind gets stronger. (which is one of few facts we have.)

PS Your equation gives me an 8.2 metre in 15 knots ?? and a 5.5 in 25. (Both out, my biggest sail is 7 and I sail from around 13 knots)



It is a wild approximation, if you could sum up variables such as wind force, board lift, water conditions, sailor weight, sailor height (think leverge), and ... sailor preferences (do you like to go overpowered or powered up) in 1 silly linear equation ... well, quite a good eqn it would be. However, center the equation on your sailing style (i.e. change the 0.65 coefficient to match your 15 knots = 7 suqare meters) and the eqn will work ok ... in the sense of giving an idea of ballpark weight related differences (not to actually pick up a sail at the beach!)

Individual variation can be a very large component. Two days ago I was out with my Acid 74 with a 4.7 SO alternating with my W52 with a 5.6 twin-cam: just for fun, same wind conditions, if I was racing slalom I would have been probably on a 6.0+

Floyd
9th October 2007, 04:19 AM
Yeh I agree it can work with an adjustment and over quite a small range; of either windstengths or weights.
Variable which has biggest influence on outcome is wind speed; purely because its effects are not linear.All others are.(Well nearly; apart from drag which favours heavier sailor.(ie double weight you dont double drag.Double wind speed ; well you know)

Think I`ll stick to sending a wind dummy out before I sail.Its still best option.

We havent factored in to any of this efficient boards.My recent Goya certainly gets me planing with I`d guess half a metre less than I was used to using.(Sorry *B)

Good sailing Davide.

Ola_H
9th October 2007, 05:15 AM
Hi Davide
Not sure sail size and weight are linear.Infact pretty sure they aren`t.
In lightish winds;or possibly in a particular given wind they could be.But as wind increases the difference in sail size has got to diminish.
A doubling in windpower quadruples the amount of energy/power available.
In lightish winds I find I need about a metre more than average (ie I`ll have a 7 on ; 75k mates on a 6 but in strong winds (ie 4 metre ish) I can get going with pretty much same size sail .
I`ve pretty much got it sorted for sail sizes/wind. But struiggling a bit on smallest board choice.
Agree with you re Acid 86/K89 though.
Thanks for repy.

Sorry for not replying earlier, but I was a bit busy and had to think a bit too. It is always dangerous extrapolating my own light weight experience to something else. However, your comment above makes things more clear. Regardless if things are linear or not, you're sail size experience is indeed the experience you have. And that coincides with my experiences as a lightweight (watching how sailor of different weights rig relative to how I rig). I would say that this comment also explains why it seems harder for heavier people to get as much wind range out of their boards.

So, when you are powered up on that 5.4, it is going to be very windy (say 4.7 weather for me) and the spectrum down to 3.7 (when I probably i still hanging onto my 3.5) really is not as big as it first seemed. Since you will pretty much not ask any light wind performance from this board, I think you should go rather small. That said, even when it windy there are wind holes, so you have to find a volume that you are still reasonably comfortable on. Hence I to think the PA 86 will be the best compromise. Then you get the more control oriented thinner and narrower tail (compared to the Kombat 89) and you still get the extra weight carrying capability compared to K79 or PA80.

Floyd
9th October 2007, 03:39 PM
Hi Ola
You are obviously correct.
I was talking about comfortable ; well powered sailing.(ie at my age I like to sail with "just" enough sail.)
On day you quoted did you wear GPS ?Would be interesting to compare Vmax on such occasions.(On same board ???) Sheer grunt versus efficiency ???
An engineer friend of mine used to say " any fool can build a bridge it takes a good enginner to "just" build one" .Sail choice is a bit like that.I like to be just sailing for most enjoyment.(and longest time)
Its got OT anyway.
All I wanted to know was how everyone thought weight affected sail range.
ie What is sail range for KA86 with 103k on it ???
Take care.
Floyd

Floyd
9th October 2007, 03:42 PM
PS
Thanks Ola for well wriiten reply.Iam going KA 86.

Ola_H
9th October 2007, 04:56 PM
Thanks. I did that "sail efficiency test two times only. One time I was on a slalom board (iS76) 6.6 was OK. Only ever so slightly on the big side I still wanted to try my 5.5 which was very underpowered, changed fins from 26 slalom to 23 speed too. Still went pretty much as fast and the biggest difference was that it was hard to get in position for a god run with the smaller gear.

A few week ago I was sailing with my wife. She was on 4.0 and I one 5.0. Lake sailing but wave sails. Kombat 79 for me. 5.0 was definitely on the overpowered side but 4.0 was still only reasonable powered up for blasting purposes. I still went around 1.5-2 knots faster with the smaller sail (and a 100 times more comfortable).

In both these cases, 2s speed readings was around 30 knots, I think.

But of course there are instances where a bigger more powered up sail would be faster.

The final answer on "weight dependance" is that it depends...

Jean-Marc
12th October 2007, 02:53 PM
Nice discussion going on here. This is a very complex issue since there are a lot of variables at play. Two examples below to illustrate that complexity :

1) 105 kg mate on Carve 161 + freerace 9.5 sail and myself 65 kg on Kombat 86 + freemove 6.9 sail. Drag racing side by side in steady onshore 12-18 knots of wind. Below 12 knots, none of us can start planing. We can both start planing at the same time with 12 knots winds and well powered-up, we were equally fast.

2) 85 kg mate on iSonic 122 (Drake Slalom Pro 42/44/46 cm fin) + Racing 7.8 sail and myself on iSonic 76 (Drake Slalom Pro 32 cm fin) + racing 6.6 sail. Drag racing side by side in gusting offshore 15-20 knots of wind. Well powered-up, he was a tad faster than me but way faster once we hit a 15 knots lull. Enter a 67 kg racer on Falcon 72 (Tectonics GW 36 cm fin) + 6.7 racing sail and this guy beat us on all point of sail with stuning planing ability in lower wind range.

Conclusions :

1) match board size with sail size according to your weight for the conditions.
2) a wider board size with a fairly large fin is faster in gusting offshore winds.

Cheers !

JM

Floyd
13th October 2007, 03:42 PM
Thanks everybody for contributions on thread.

Going top get A 86 next week !

Take care.

Floyd