What would be the speed difference between the two sails of same size, cam vs no cam? Any one with actual gps speeds?

What about light wind conditions, say 8-15knots, is there a power/speed difference? Pros/cons of each?

I'm no expert on speed but as lao shi says you do your best speed deep off the wind without a lot of pressure in the sail.

The trick seems to be that in order to carry the biggest possible sail for the speed run you have to be over powered the rest of the time. Cammed race sails are the rangiest.
I don't think there is much difference with uncammed race sails though. In fact I'd be surprised if there was any difference off the wind.

Received wisdom (Bruce Peterson) has it that uncammed sails lose a bit close to the wind, but not much.

In light conditions the Cammed sail will have more power on average as its shape remains stable thru lulls. In hi winds a properly designed No Cam sail will give it a run for its money.

Most of my experience with No Cam sails for speedsailing have been with wave/freeride sails with Ka's Kaos 4.7, Kult 5.3 and 5.3 Koyote.

The Kaos and Kult have both done over 40 knots for interest sake even though they are not designed for serious speedsailing, they really need steady strong wind/gust to achieve these speeds where their shape his held in place.

Story here www.kasail.com/windsurfing/team/craigspotty.html
or...
Date : Sunday, September 24, 2006
Spot : Sandy Point, Victoria, Australia
Board : Starboard Acid 94
Sail : KA Sails Kaos Wave 4.7
Fin : Starboard Drake Wave 24
Average speed : 38.38 knots (39.4 39.1 38.1 37.8 37.5)
Max. GPS (display) : 41.5 knots
Max. 2 sec. (software) : 40.7 knots
100 m run : 40.2 knots
250 m run : 39.2 knots
500 m run : 38.5 knots

Where as the Koyote which has Koncept blood/shaping in it with more battens, is designed for going fast on an off the wind in a No Cam setup. It has more stability in hi winds and is probably capable of going faster on a big day.

My Koyote GPS speeds story here...
www.gps-speedsurfing.com/default.aspx?mnu=user&val=25886&uid=831
or
session_date Saturday, December 22, 2007
Spot Sandy Point, Victoria, Australia
Board Carbon Art Speed board 44, 2007
Sail KA Sails Koyote 5.3, 2008
Fin KA-Fin Lockwood<>McDougall Assy 21
GPS type Garmin Foretrex 201

Average speed 43.42 knots ( 43.9 43.7 43.6 43 42.9 )
Max. GPS (display) 45.4 knots
Max. 2 sec. (software) 45.2 knots
100 m run 44.2 knots
250 m run 43.8 knots
500 m run 43.3 knots

First Test run....
www.kasail.com/windsurfing/2007_news_archive.html

Either way GusTee just ride it as fast as you can!!!

so many variables there Pete I vaguely remember trying that rig which was set up by Ant Baker with his harness lines- which felt like they were 40 inches long. I couldnt use them. So I only did 1 or 2 short runs before I was spent. Later we checked the length of his arms- they were about 20cm longer than mine... no wonder he had graze marks on his knuckles...

No cam sails are generally flatter overall, so for their size can be sheeted in easier for the same power- especially across the wind. Also the centre of pressure tends to be higher in general- meaning a more upright stance which is useful in lighter conditions to support your body weight. This is less efficient for speed sailing though. They collapse under no load- which is very noticeable when you are sailing downwind and go into a lull- this makes the power switch off completely.

As for profile, the current breed of race sails are very efficient at lower angles of attack (upwind or across the wind at high speeds). A narrow sleeve sail cant really match this performance aerodynamically. The difference is only moderate though.

So the short answer, no-cam sails can be fast, but cams (with wide luff sleeve) offer the advantage of slightly better aerodynamic efficiency at low angles of attack, and better mechanical stability of the profile- meaning the profile doesnt collapse in the lulls, or move around too much in the gusts (resulting in excess backhand pressure for example). So across the wind/upwind the cammed wide sleeve sail will be better. And in really strong wind the cammed sail will generally be more manageable.

For speed the most important thing is to have optimal balance over the range of conditions experienced on the run. Which means maximum sail power with the centre of pressure in the right spot for maximum leverage. Sail efficiency is not so important downwind, since sail drag does not work against the direction of travel, but increases the fin load. This is why ice sailing is so much faster despite the sails being relatively simple/inefficient- the skates can create a lot of side load (lift) without producing drag against the direction of travel.

The drag we experience comes mostly from the board and fin. At high loads (upwind, or across the wind at lower speeds), more fin load means more fin drag, which is why we go slow upwind, and why sail efficiency is important here. The fins operate with some laminar flow, so at higher speeds off the wind the drag is relatively constant under low loads- which means we can tolerate some sail drag without impact on the speed. That is why a lot of people have gone fast on sails that are not very efficient the rest of the time (eg slow upwind).

Just to add my 2c worth, I have an Ezzy SE Wave that I was using for speed sailing. When the (very overpowered) winter gusts hit it I felt like a rat being shaken by a dog. I got a KA Koncept (Cammed sail) and the gusts just made it go faster and I wasnt losing control.

But it took me a few months before my top speed changed by more than 1 knot.

So in my opinion its more about the control in overpowered conditions (which is where you have the best chance of good speed) than the raw power out of the sail.

Hey Gustee,

There's a big difference between buying a cammed sail to go fast, and buying a sail to get going in lighter winds.

I think that a big cammed sail would be helpful for you, as well as an adjustable outhaul. Also a big efficient fin will help you get going

A lot depends how much you weigh, I'm only light, (just under 70kg most of the time), and have a lot of trouble with most big sails. The uncammed variety by far the worse, they don't turn on early enough for the winds I want to sail them in. Making them unstable and underpowered. I've even had to modify the battens in my biggest cammed sails, (a 7.0 gastra and a 6.0 tushingham) to make them work better in lighter winds.
If you're over 85kg, most non cammed sails will probably fill out ok and if you're comfortable with a 7.5 in 20kts that's probably the case.
But at 8kts, there's not many uncammed sails that will be properly turned on, meaning you will be slower than on a cammed sail that should be somewhere near fully on.
It's amazing how much sails differ in this respect, the Avalon sails I have all turn on very quickly (about 5-8kts for the wave sails) giving them a great bottom end. But some other sails I tried need about double that, killing their bottom end.
So it's very hard to generalise.

GusTee said...
... The wind is weak most of the time I get a chance to get out (8-15 knots). The biggest sail I have which gets used the most is a 7.5 Sailworks Retro, which is RAF. The board is a Starboard Go 133.

If you want to go fast, loose the board... the Go is excellent at learning, but its not a quick board -> its not the volume, but the shape (outline, rocker, width).

Lots of people think "cam's -> must be hard to use"... you could always try using a model that has less cam's in them, eg: NP Slalom, NP V8, KA Koncept, etc. rather than a full-on race sail. aka less cams often implies easier to use.

Sorry Mat. My understanding is that the Go 133 is the same shape as the Futura 133 which is a very fast board indeed. The main difference is the construction. It certainly is heavier but that should not affect top speed much at all. There may be a difference in foot strap positions bit again I think there is quite a bit of available adjustment there.

Go for a smaller fin which will be more efficient at higher speeds.

Oh, and try a Koncept cam'd sail, I think you will like it.

Thanks to everyone who've chimed in on cam vs no cam. Just curious, what are some of the things that cammed sails are not good for? When would you swap out a cammed sail for one that is un-cammed?

I'm keen to try a cammed sail. I might have to bite the bullet and buy a new mast so I can get something around 8.5m to make the most of the light winds.
What are the visual clues/features of a sail that has good bottom end as opposed to top end? Can you tell without actually sailing it? How would you pick the one? What size would you go for? - wind 8-15knts / starboard go133 & jp slalom42 fin / 70kg sailor who likes speed.

Finally, I know the Go133 isn't built for speed and will end up going for something along the lines of Futura 111 or similar once I get some more money together. I was told that in light winds there would be little difference, unless you go for a long board. What would you spend the money on first, board or a larger cammed sail?

GusTee said...
What doesn't make sense to me is why the board weight is held in such high regard. As far as speed, compared to the weight of the sailor and the rig, board weight seems insignificant. Am I missing something?

That is a really good question - the short answer is, 1kg makes quite a bit of difference.

I really dont know what the long answer might really entail -> I suspect is has to do with the boards' swing weight... aka: amount of force that your ankles can exert on the board, while it moves around underneath you.

In a similar vein, board thickness is a common parameter for board tuning (thinner is better), ie: some things we know from experience being good vs bad.


I should note though, that once the wind gets up into the higher end (for the board+sailor), extra weight probably helps more than it hinders.

i have a Fanatic 156 litre [75 wide by 275 long].

it weighs including straps + fin at a very low 8.5kg.

i tested it against another,slightly newer model fanatic 75 wide,that is fully 1kg heavier than mine with a 7.7m severne code red rigged full.

i was planning around 50 percent of time on my gear in around 10 knots.

i borrowed my friends fanatic 75, which also has a wider tail and had a 10cm bigger fin, i put my rig on it and i managed to plane only once in 15 minutes.

i could feel the extra 1 kg underfoot, it made the board feel so sluggish especially in non-planning conditions. once on plane it felt nearly as good as mine.

in 8-12 knots of wind full carbon boards made NOT to last are the way to go.

Yep, agree with fullmoon, the last place to take a cammed sail is wave riding.
To wave ride you need to be able to turn the sail off at times, you can't do this with cammed sails.
I know nothing about free ride, but I suspect the same holds true there.

And in addition to others on the light weight bit.
Riders weight is part of the power train, (power from the sail is counter balanced by riders weight, and can be no more than the sailor can counter balance). Where as the rest of the rig contributes to drag.
So you can't compare the percentage of board weight with riders weight to get an idea of it's effect. you have to compare it with the overall weight of the rig, ie board fin sail mast boom etc, then 1kg change in one of these is a reasonably big percentage.
I'm having a go at lightning my fin, by making it out of timber and carbon, Avalon Sail Co has made me some very light sails, should improve my light wind sailing no end.

decrepit said...

Yep, agree with fullmoon, the last place to take a cammed sail is wave riding.
To wave ride you need to be able to turn the sail off at times, you can't do this with cammed sails.
I know nothing about free ride, but I suspect the same holds true there.

And in addition to others on the light weight bit.
Riders weight is part of the power train, (power from the sail is counter balanced by riders weight, and can be no more than the sailor can counter balance). Where as the rest of the rig contributes to drag.
So you can't compare the percentage of board weight with riders weight to get an idea of it's effect. you have to compare it with the overall weight of the rig, ie board fin sail mast boom etc, then 1kg change in one of these is a reasonably big percentage.
I'm having a go at lightning my fin, by making it out of timber and carbon, Avalon Sail Co has made me some very light sails, should improve my light wind sailing no end.

I've got a demo duo speed fin made of carbon it's at least 30% lighter than the g10 fins i got in similar sizes.
If a kiter uses helium in his kite will it be lighter?

re: They are easier to carry to the beach etc, etc.

This is enough to win me over. I still carry my gear in 2 pieces, as the lot is too heavy...