Forums > Land Yacht Sailing Sail making

Cam batten windsurfer sails

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Created by JohnHS > 9 months ago, 17 Jun 2016
trbnt
33 posts
31 Jul 2016 8:33PM
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John-

What does "Scored a new PB of 85.3 first run out." mean??

thanks- Thomas

sn
WA, 2352 posts
31 Jul 2016 10:10PM
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trbnt said..
John-

What does "Scored a new PB of 85.3 first run out." mean??

thanks- Thomas


personal best of 85.3 kilometres per hour on his first run on the salt lake.

trbnt
33 posts
31 Jul 2016 11:06PM
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Ah- Thanks!

Westward
47 posts
1 Aug 2016 7:30PM
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Hi All,

Really interesting thread this one.

I had a bash at fitting a windsurf sail on to my mini over the weekend.

I was wondering if using the outhaul on to boom (as i did in my lash up) will be ok or should i replace the boom entierly with the wish bone boom?

When i sheet in it pulls the rake on pretty quickly with only minimul protest noises from the cart.

All the best

Dave


JohnHS
WA, 34 posts
2 Aug 2016 9:42AM
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Westward

Sail looks good but the mast is too long for the sail and therefore too stiff.
The main reason for this thread is to find ways of using wind surfer sails "As Designed" Using the correct mast will result in the sail setting with the intended luff curve. My thinking is that if windsurfing companies are spending millions on R&d to improve the performance of their sails then why do we go and re-cut the luff because our masts are wrong?

A modern windsurfing sail will specify what masts to use see pic.




The boom/out haul you have looks fine for that type of sail. Remember with a windsurfer its the down-haul that sets the shape of the sail.
looks like your sail does not have cam battens.

I am using a wishbone boom because with my particular sail I can not set the cam battens onto the mast without strong out-haul at the point where wishbone attaches.

I would much rather use Chook's solution of adding a triangle to the Clew and using a single boom, but I don't think my sail will work with that method.
Waiting to catch up with Chook and ad Greg to get their input.

Forgot to mention, the pic I posted above of my new yacht with Ben's 3m sail and straight boom suffers the same problem as I have described above. But that's the only small sail I have at the moment.

Once I have had time to get used to the 7m sail I expect I will want a 4.5 to 5m to use as a storm/high wind sail.
Just to be clear that means I am expecting to use a 7m windsurfer sail where I would previously have used a 5.5m class 5 sail and a 4.5 or 5m windsurfing sail where I am now using a 3m storm sail.

Westward
47 posts
3 Aug 2016 7:30PM
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Hi John,

Thanks for your notes :-)

I had a look on the windsurf bag for the sail pictured but it donest have any guidance on settings. I do have a shorter mast though so ill rig it up with that and see how it goes. I'll hope on to Google and look to see if there are any specs for the sail.

Its intersting that you are going to larger windsurf sails than you would use for a "traditional" sail. Is that because you need the larger area to get going with the flatter sails?

The sail that was in my last post is much smaller than the sail I have been using.

Thanks again

All the best

Dave

Chook2
WA, 1173 posts
4 Aug 2016 11:31AM
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Chook2 said..

You can sail an uncut windsurfer sail that is rigged correctly, in almost twice the wind strength of a similar "conventional/old fashioned" land yacht sail.
We have proved this on many occasions.
When the blokarts were over powered on 2mtr sails and were quitting sailing due to the extreme wind gusts in Kingston South Australia early this year, I could still easily out run them with much more ground speed, having fun in my mini fitted with a 6.6 mtr sail still averaging in the mid 80's kmh.

Quite a few guys took my mini for a run with this sail in these conditions and couldn't believe how easily it handled the wind gusts. When you sheet out in a gust, the sail is absolutely drum tight, so it's impossible to get it to flap and the top simply weather vanes/twists off till the gust eases.

This mean that only 3 sails 5.5, 6.6 and 8.3mtr cover me from 3 to 40+ knots. (I have other sizes that I'm still testing but only take 3 to events.)




Greg and I haven't reinvented the wheel in Esperance, we have just taken on board all the development the windsurfing community have proven over the last 15 years. They windsurf at 54 plus knots on water, with 6m2 to 7m2 sails, so why shouldn't it work on land.

It's dirt cheap to try these rigs, as the gear is available in good quantities as the windsurfers upgrade each year. All my rigs came from the "recycling centre" at the waste disposal site, (thanks "sn") or given to me as the older model (mine are 2008) sails aren't worth trading.

The reason for the larger size "Westward" is a windsurfer "cambered sail" (they have roller cams that clip onto the mast at the front of the bottom 4,5, or more battens in a larger luff pocket to make an aerofoil shape when tensioned up.). is down hauled and absolutely drum tight without any sheet rope tension at all. So big is better.

So when sailing and you get hit by a big gust of wind on a conventional soft sail you sheet out and loosen the fabrics tension. If it's bad enough it will belly out the sail, flap or resonate like hell and shake the mast, compromising the traction on particularly the front wheel. This is totally the opposite of what you want to happen when you are in trouble.

When the cambered sail sheet rope is released it simply twists off/weathervanes (just the same as a soft sail), BUT doesn't belly out at all and the whole sail is still under enormous tension from it's down and outhaul and there is simply no way it can flap.

When your not using all the power of the sail, it's simply twisted off/weather vaned at the top from the apparent wind and causing very little drag. But when the power of the extra square meters of area is needed (up and down wind) or in lighter conditions, Sheet in and it's all there to be used.
In very light conditions with a limp sheet rope, the cambered sail is already set to the perfect aerofoil, even before any breeze is detected and ready to power away with even the slightest gust. It just makes sense.


Most times it takes a lot of coaching to even get someone to get in and take our land yachts for a sail in such strong wind conditions, with so much "real estate" up the mast.
But the guys always return with a huge smile, totally amazed and convinced it's so easy to control. ("Touch wood", No one has ever tipped my yacht trying it out in these gusty conditions.)
Sure they will lift a wheel, but can be fully powered up and easily controlled on only 2 wheels and use this to slingshot forward when the gust eases.

If it all goes wrong, just dump the sheet rope at any speed and the sail will just weathervane and nothing else happens. You just slow down.
The boom will not move away from the foot of the sail, flap or try and kill you, as it sits under the sail due to the high out-haul tension and the aerofoil shape holds it in it's neutral position.

Hope I have managed to explain it properly.

barney831
38 posts
4 Aug 2016 10:46PM
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Chook2 said..

Chook2 said..

You can sail an uncut windsurfer sail that is rigged correctly, in almost twice the wind strength of a similar "conventional/old fashioned" land yacht sail.
We have proved this on many occasions.
When the blokarts were over powered on 2mtr sails and were quitting sailing due to the extreme wind gusts in Kingston South Australia early this year, I could still easily out run them with much more ground speed, having fun in my mini fitted with a 6.6 mtr sail still averaging in the mid 80's kmh.

Quite a few guys took my mini for a run with this sail in these conditions and couldn't believe how easily it handled the wind gusts. When you sheet out in a gust, the sail is absolutely drum tight, so it's impossible to get it to flap and the top simply weather vanes/twists off till the gust eases.

This mean that only 3 sails 5.5, 6.6 and 8.3mtr cover me from 3 to 40+ knots. (I have other sizes that I'm still testing but only take 3 to events.)





Greg and I haven't reinvented the wheel in Esperance, we have just taken on board all the development the windsurfing community have proven over the last 15 years. They windsurf at 54 plus knots on water, with 6m2 to 7m2 sails, so why shouldn't it work on land.

It's dirt cheap to try these rigs, as the gear is available in good quantities as the windsurfers upgrade each year. All my rigs came from the "recycling centre" at the waste disposal site, (thanks "sn") or given to me as the older model (mine are 2008) sails aren't worth trading.

The reason for the larger size "Westward" is a windsurfer "cambered sail" (they have roller cams that clip onto the mast at the front of the bottom 4,5, or more battens in a larger luff pocket to make an aerofoil shape when tensioned up.). is down hauled and absolutely drum tight without any sheet rope tension at all. So big is better.

So when sailing and you get hit by a big gust of wind on a conventional soft sail you sheet out and loosen the fabrics tension. If it's bad enough it will belly out the sail, flap or resonate like hell and shake the mast, compromising the traction on particularly the front wheel. This is totally the opposite of what you want to happen when you are in trouble.

When the cambered sail sheet rope is released it simply twists off/weathervanes (just the same as a soft sail), BUT doesn't belly out at all and the whole sail is still under enormous tension from it's down and outhaul and there is simply no way it can flap.

When your not using all the power of the sail, it's simply twisted off/weather vaned at the top from the apparent wind and causing very little drag. But when the power of the extra square meters of area is needed (up and down wind) or in lighter conditions, Sheet in and it's all there to be used.
In very light conditions with a limp sheet rope, the cambered sail is already set to the perfect aerofoil, even before any breeze is detected and ready to power away with even the slightest gust. It just makes sense.


Most times it takes a lot of coaching to even get someone to get in and take our land yachts for a sail in such strong wind conditions, with so much "real estate" up the mast.
But the guys always return with a huge smile, totally amazed and convinced it's so easy to control. ("Touch wood", No one has ever tipped my yacht trying it out in these gusty conditions.)
Sure they will lift a wheel, but can be fully powered up and easily controlled on only 2 wheels and use this to slingshot forward when the gust eases.

If it all goes wrong, just dump the sheet rope at any speed and the sail will just weathervane and nothing else happens. You just slow down.
The boom will not move away from the foot of the sail, flap or try and kill you, as it sits under the sail due to the high out-haul tension and the aerofoil shape holds it in it's neutral position.

Hope I have managed to explain it properly.


Most of what you say is true except the part about the 'perfect aerofoil'. The 'perfect aerofoil' is a function of speed and requires on-the-fly adjustable outhaul and downhaul as well as the knowledge necessary to optimize the shape of the sail - particularly important for hyperwind sailing and competitive racing. Fortunately, the 'perfect aerofoil' is not necessary for just rolling around on a beach and a poorly turned battened windsurfing sail is still an order of magnitude better than a soft flapping sail.

Kenney, B.C., 2001. Hyperwind Sailing. Catalyst, J. Am. Yacht Res. Soc., 6, 24-26.

Bynorthsea
67 posts
19 Aug 2016 11:54PM
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Hi Chook I am getting close to taking the angle grinder to my mast foot so I can try the uncut sail idea, so far I haved failed to find short lengths of 4150 hollow steel or equivalent, I could get 40 x5 ms have you tried anything other than high tensile?

Sylk
WA, 197 posts
21 Aug 2016 12:14PM
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Having seen and felt the load on the mast base and watched the whole frame flex in the gusts.
My gut feeling says mild steel wont cut it but that it purely instinct not a shred of engineering.

Chook2
WA, 1173 posts
22 Aug 2016 7:59PM
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Greg was here yesterday and I asked him about his original mast stalk which was only 2.5mm wall water pipe.
This setup lasted 12 months of hard sailing before it failed at the weld where the pipe went through the stalks mounting block, so with 5mm walled pipe I'd just go for it Bynorthsea.

Our 50mm x 31mm 4140 hollow bar is machined down for 48mm x 3mm aluminium to slide over (Internal mast strengthener) so ends up approx 41mm Outside Diameter, so the 5mm wall turns out to be exactly the same thickness, just that the pipe is only 350 grade, rather than the 4140. That 5mm wall thickness of pipe will take some grunt to bend at the weld!!!! Particularly while trying to do it with a flexible lever. (mast)

Bynorthsea
67 posts
23 Aug 2016 2:06AM
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Good my feeling was that it should do and the weak spot was the weld junction. One more question, I currently fly cut windsurf sails following the adage flat is fast. Do I need a cammed sail to get the advantages of a full rig?

Chook2
WA, 1173 posts
23 Aug 2016 8:03AM
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Bynorthsea said..
Good my feeling was that it should do and the weak spot was the weld junction. One more question, I currently fly cut windsurf sails following the adage flat is fast. Do I need a cammed sail to get the advantages of a full rig?



No not at all. The un-cammed sails will work equally as well too.
The cambers just add a bit more of aerofoil shape to the large 500mm mast pockets, but the same thing can be obtained with a standard uncut windsurfer sail.
(Windsurfers don't always like cambered sails, They are a bit trickier to get setup. Also when they dunk them this huge mast pocket fills with water and it is much heavier to right again.)

Windsurfer sails are all about downhaul.......... PLENTY off it. People just don't understand this concept of keeping a sail working just as the designer intended it to do.

The sail matches the mast curve and they work together to achieve a really tight sail surface that wont flap at all without any sheet rope tension.
They don't have a sheet rope on a windsurfer rig do they?

Watch a few YouTube videos of guys setting these sails up and you can then understand how much downhaul is required. Most are 6 to 1 to get the sail nice and tight.

The belly of the sail is then controlled with adjusting the downhaul tension, as well as the outhaul at the clew/rear.

When high wind sailing everything is tensioned to the max which flattens them right out absolutely drum tight. But with a perfect foil.

Cheers.

Chook2
WA, 1173 posts
24 Aug 2016 10:30PM
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barney831 said..


Most of what you say is true except the part about the 'perfect aerofoil'. The 'perfect aerofoil' is a function of speed and requires on-the-fly adjustable outhaul and downhaul as well as the knowledge necessary to optimize the shape of the sail - particularly important for hyperwind sailing and competitive racing. Fortunately, the 'perfect aerofoil' is not necessary for just rolling around on a beach and a poorly turned battened windsurfing sail is still an order of magnitude better than a soft flapping sail.

Kenney, B.C., 2001. Hyperwind Sailing. Catalyst, J. Am. Yacht Res. Soc., 6, 24-26.




I just reread that Barney831 and I totally agree.
We tune our sails for high speeds that's all we are after. Up wind, down wind and the reach is just a bonus.

The trim on our windsurfer sails is measured in millimeters of downhaul adjustment with the use of a cam cleat at the base of the mast. Full belly to flat is only 40 to 50mm take up the 6 to 1. It's easy to do on the fly, but not always necessary. The addition of the sheet rope adding additional tension to the very rear of the boom usually solves this requirement.

Gizmo
SA, 2815 posts
25 Aug 2016 9:07AM
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Slower speeds often on sites that have a soft or boggy surfaces require a 'fuller' sail to work effectively, a sail with a 'fixed' or 'pre-set' camber / draft is like pre-setting your cars gearbox in 2nd or 3rd gear and never changing it.

Water yachts even high speed catamarans don't come anywhere close to the 'window of wind speed' that land yachts use.. For example in perhaps a 15kmh wind a land yacht has wind on the sail starting from 15kmh to perhaps 85kmh [which is hurricane force] .. (a 70kmh variation) where as a sailboard in 15kmh wind may get to 30kmh (a 15kmh difference).

So a sail that works from a slow wind speed to a much higher speed MUST adjust the draft of the sail somehow.. A fixed draft is just a compromise.

If you do some research on Czeslaw Marcha and his books will give you a great insight into sail design.

en.wikipedia.org/wiki/Czeslaw_Marchaj

Chook2
WA, 1173 posts
25 Aug 2016 8:47PM
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Thanks for the link Gizmo. Lots of great information there.

I'm just not very clear in answering the query or describing it well. Sorry about that Guy's.

I'm not really doing anything differently from rigging a normal sail Gizmo. All the difference is in the design of a windsurfer sail.

From somewhere around 2005???? They were designed from the ground up with high surface tension over all the sail, under all circumstances. (Drum tight sails and large drafts aren't used in the same sentence very often.) This is where I believe windsurfing sail design has the biggest advantage. The sail can be rigged or set to whatever draft/ belly that is required (within the parameters of that sails use) and it's still drum tight without a wrinkle. The mast is curved with a nice preload and this stops it shaking when there is no sheet tension. (If a windsurfer sail flapped or shook even a small amount at high speed the wind-surfer sailor would be straight into the water. )

So my setup difference to "traditional land-yachting sails" is that I’m pulling the tack down hard with very high downhaul pressures to set the sail SURFACE tightly and also using the outhaul to assist in tension the whole sail surface. This is before any sheet rope tension is even applied, just the same as the windsurfing communities do.

By fine adjustment of the downhaul, to a slightly lesser setting, I can still shape a large draft into the sail, but the sail surface will always remain completely tensioned up drum tight. (I guess that's the hard bit to understand, I had a LOT of trouble getting my head round it too, till I experienced it firsthand.) Big or small draft/belly and drum tight/wrinkle free sail, this it the big bonus!!!. A cambered sail adds a bit more aerofoil shape as well.

I sail on my local salt lake which has a pretty soft surface. This is further complicated by fickle inland winds, and sometimes a low atmospheric pressure that has allowed the subsoil water to dampen the lakes crust. So as a sail “pre load” I have a guess and will set more draft set into the sail when I rig up. As I go sailing, my speed increases and more sheet rope tension is added to the very rear of the sail. It flattens the sail further and removes some of the belly (just as conventional sails do) business as usual, till I’m getting closer to the best speed for those conditions.
I can then further increase my top speed by simply trimming (fine tuning my original guess/setting) in these last few mms of downhaul and further flatten/remove the draft from the sail as necessary. This is easily done "on the fly". A reverse I suppose, to the "boom outhaul adjustment levers" that work so well.

So in fact not stuck in 2 or 3rd gear Gizmo, but an "infinitely variable transmission".

The added benefit of these sails is that when it "all goes out the window" and you have to ease the sheet at any speed, it remains totally well behaved without any sail shake at all due to these preloaded tensions. At 85kmh throw away the sheet rope and the sail will simply weathervane and you slow down. It's so nice to have a boom that doesn't want to kill you in these circumstances.


The "Esperance windsurfer sail system" isn't anywhere near perfect yet. Greg and I always need to do further sail testing when there is wind about. (As we have a very small window of opportunity of when our lakes dry enough to sail on.) That's what we keep telling our wives anyway.

gofaster
74 posts
4 Apr 2017 11:41AM
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Sylk

Going back to your experiments with the stayed mast support. I'm interested in following up this approach. Mainly due to paranoia about damaging my expensive windsurfing kit! Could the mast support be unguyed?

Sylk
WA, 197 posts
6 Apr 2017 6:30PM
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gofaster

I dont quite understand your question in relation to this thread. As explained in this thread my 1st idea was to support the mast with guys I didnt like the result so went on to modify chooks unguyed mast support system.

Thats what this thread is all about.

gofaster
74 posts
7 Apr 2017 5:07AM
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Sylk
Sorry had completely misunderstood that you had used a guyed mast. I thought it was a guyed mast support, like on the iceflyer.
I am interested in trying an unguyed mast support, like an earlier post suggested.
I like chooks mast base idea but don't want the reinforcing in the mast. I want to use a windsurfing rig as standard as possible - plug it in to the frame and attach to an unguyed mast support which is in front of it and part of the frame. The mast support needs to be as strong as chooks mast support. He has shown it is strong enough.
My question is will the mast stand the loading as it is not originally designed for this configuration. Would an rdm mast be better than a std?

Sylk
WA, 197 posts
7 Apr 2017 3:42PM
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The system that chook uses works very well but he adds quite a lot of carbon reinforcing to the mast.
The system that I developed in the second half of THIS thread uses less reinforcing on the mast you could use my system with no extra reinforcing but i wouldn't advise it.

I think using RDM masts would be more difficult as the mast support is internal therefore on an RDM support there will be much less material, smaller diameter base etc..

My system works well while only applying reinforcing to the mast over a distance of 400-500mm at the point where the internal heavy duty mast extension finishes. Done properly this modification should not affect performance on a windsurfer.

You can easily set all this up without reinforcing your mast, let me know how it lasts. perhaps i don't need to bother reinforcing my masts.



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"Cam batten windsurfer sails" started by JohnHS