Sail battens angle,sail rake

Enable JavaScript to get the best experience.

Search Subscribed Topics Active Topics

Created by

out > 9 months ago, 25 Aug 2020

Madge

NSW

471 posts

27 Aug 2020 4:56pm

Select to expand quote

GasHazard said..
^ Or he could just do what he did in the reasonable expectation of getting a civil response.

I did respond in a civil way, it was him that suddenly knew far more than everyone else and was instead of asking why , was questioning why..????

As a sail maker I do find sometimes that people out there think they know far more than anyone else. I have been in the field for 35 years and sometimes people out there like to know why things happen and thats ok, thats how science works by questioning something, but then telling you that you are wrong is just plain weird. Anyway in years to come we'll have to see what happens.....Until then....???

Gestalt

QLD

14722 posts

27 Aug 2020 7:00pm

Select to expand quote

Madge said..

Gestalt said..
Probably going in the direction of where they once were

Nah, the old sails with no twist at all, they were great for getting up and going but terrible in any gusts. New sails are soo much better.

They aren't so powerful but more controllable, have a wider wind range and are lighter in the hands.

Agree

I was getting at aspect ratio. We've seen high aspect before.

sailquik

VIC

6166 posts

27 Aug 2020 7:25pm

Select to expand quote

GasHazard said..
^ Or he could just do what he did in the reasonable expectation of getting a civil response.

And he has.

sailquik

VIC

6166 posts

27 Aug 2020 7:34pm

Select to expand quote

Gestalt said..
Agree
I was getting at aspect ratio. We've seen high aspect before.

We certianly have.

The first NP RAF wave sails I had in the early '80's were extreme. I remember that my 4.7m RAF Wave set on a 5m mast (plus a bit of extension

) and had an incredibly short boom. They were great in their time, BUT, I would take ANY current sail now in preference.

I had those sails down to 3.3m and they still used a 450 mast! Boom on that one was way under 130cm! (I don't remeber the exact specs and I am too lazy to look them up

)

Gestalt

QLD

14722 posts

27 Aug 2020 9:21pm

Select to expand quote

sailquik said..

Gestalt said..
Agree
I was getting at aspect ratio. We've seen high aspect before.

We certianly have.

The first NP RAF wave sails I had in the early '80's were extreme. I remember that my 4.7m RAF Wave set on a 5m mast (plus a bit of extension

) and had an incredibly short boom. They were great in their time, BUT, I would take ANY current sail now in preference.

I had those sails down to 3.3m and they still used a 450 mast! Boom on that one was way under 130cm! (I don't remeber the exact specs and I am too lazy to look them up

)

And NP race sails that went high aspect.... hang on they've done it again.

Ka koncept has always been higher aspect.

The severne foil freek sounds interesting.

Basher

590 posts

27 Aug 2020 8:15pm

Modern windsurf sails are very good but they have also progressed alongside board development.
Let's runthrohg a few of those issues.

On short wave boards we use a very upright stance but the rig still moves aft as we start to plane, bringing battens more parallel to the air flow.
The aspect ration of sails changed so that our masts were shorter and that was to help with swing weight in transitions and for when a wave board or freestyle board is in the air and rotating.

Those windsurfers who race will have a different agenda. Some newer race sails are now high aspect again and that's because of foiling - which generally happens in much lighter wind.
We might also see tighter leeches on foiling boards, not just because they are more powerful in light wind but to create more leverage or downforce to use against the upward lift from the foil.

Battens are already tapered to help shape the sail, but they tend to take up the cut of the sail rather than to force a new shape into a sail with a bad cut. Batten ends become more critical when used with cams because of the risk of breakage and because of the need for cams to 'tack' (rotate efficiently) on the mast.

There's not much that hasn't been tried with our sail designs. But the latest news is that some foilers are using an MDM mast - and that's a new mast diameter that's half way between an RDM and an SDM. MDM stands for 'medium diameter mast'.

Imax1

QLD

4926 posts

28 Aug 2020 6:47am

Yeah ,cos we need more mast variables .

John340

QLD

3373 posts

28 Aug 2020 6:53am

Select to expand quote

out said..

listen at 45:50 - 47:10 why/how Goyard hold his sail vertical as much as possible.

Follow next few years in which direction foil/slalom sails are going.Indeed,even now, if you watch carefully you can see in which direction they are going.

Madge provided the key response to your question with the second post.

On fin windsurfing you have to balance the centre of effort (COE) of the sail with the centre of lateral resistance (COLR) of the board. As the board goes faster the COLR moves towards the tail as the board gets on plane, so the COE has to move backwards. You can only do this by raking the sail towards the tail.

On foil windsurfing, the COLR is fixed, so the COE remains fixed and the sail remains upright. In the video, they talk about the increased vertical lift from the front wing and the need to increase weight over the front leg to counteract this lift. This reinforces the need to keep the sail upright.

sailquik

VIC

6166 posts

28 Aug 2020 8:43am

Select to expand quote

Gestalt said..
Ka koncept has always been higher aspect.

There was a significant lowering of Aspect Ratio of the KA Koncept in 2012. Many of the sizes went one mast size shorter. e.g., the 7m went from a 460 mast to a 430 mast. The 5m went from 400 to 370.

Gestalt

QLD

14722 posts

28 Aug 2020 9:02am

yes but compared to other manufacturers it's higher aspect.

sailquik

VIC

6166 posts

28 Aug 2020 4:12pm

Select to expand quote

Gestalt said..
yes but compared to other manufacturers it's higher aspect.

Not so. When was the last time you checked them out?

Boom and mast lengths are very simiar to same type and sizes in many other brands. Compare them with the Simmer sails for example and luff and boom lengths are within a cm or two for same sizes.

As I said earlier, most of the different brand slalom and race sails share very, very similar AR. Those very few that don't are the exceptions.

For a couple of years the NP cammed slalom/race sails were among the very lowest aspect. The small changes they seem to have made to the latest release seems to bring them back closer the majority in my cursory scan of it. It certainly does not appear to be a radical change.

John340

QLD

3373 posts

28 Aug 2020 5:04pm

Select to expand quote

Gestalt said..
yes but compared to other manufacturers it's higher aspect.

There is no discernible difference between the KA and Duotone 2020 7.7

Gestalt

QLD

14722 posts

28 Aug 2020 5:40pm

ka koncept 7m - 199x458 = .43
ka race 7m - 199x458
np racing evoxII 7.4 - 205x482 = .425
ga vapour 7.2m - 208x461 = .45
simmer scr 7m - 212x451 = .47
duotone warp 7m - 213x452 = .47

maybe im reading it wrong but here are the numbers. in order of boom length

John340

QLD

3373 posts

28 Aug 2020 7:05pm

Boom lengths are effected by the size of clew cut-outs. The clew cut-outs on the Duotone are smaller hence the boom length is longer. However if you put the Duotone on top of the KA, the luff and leach above the boom are almost identical.

Gestalt

QLD

14722 posts

28 Aug 2020 7:53pm

Select to expand quote

John340 said..
Boom lengths are effected by the size of clew cut-outs. The clew cut-outs on the Duotone are smaller hence the boom length is longer. However if you put the Duotone on top of the KA, the luff and leach above the boom are almost identical.

well.
the way i read your post is you have excluded the area of sail below the boom.

Mr Keen

QLD

690 posts

28 Aug 2020 9:01pm

Bottom baton longer on KA, area below the boom much the same...

Gestalt

QLD

14722 posts

28 Aug 2020 9:26pm

Select to expand quote

Mr Keen said..
Bottom baton longer on KA, area below the boom much the same...

if we overlay sails and they look much the same that doesn't really mean much. with a typical sail outline a shorter boom means a higher aspect ratio because it effects the average chord generally speaking.

Mr Keen

QLD

690 posts

28 Aug 2020 9:42pm

Not necessarily, width of luff and general cut would surely have influence of chord or combination there of....
disclaimer: not sail designer, maybe one could chime in

Gestalt

QLD

14722 posts

28 Aug 2020 9:53pm

"Aspect ratio is a measure of the ratio between the span of the wing to its chord. In most cases the wing chord is not equal along the length of the span which is why aspect ratio is most commonly calculated by dividing the square of the wing span by the reference wing area."

luff x luff / area.

in the case of the duotone v koncept they are both 7m sails. because the koncept has a longer luff the aspect ratio is higher ie. the boom length is shorter.

the sail spec verify that boom length is shorter also.

as a rule of thumb for a sail with a clew cutout shortening the boom length increases aspect ratio because it reduces sail area below the boom.

kato

VIC

3513 posts

28 Aug 2020 10:09pm

Popcorn is ready.......::

Subsonic

3384 posts

28 Aug 2020 8:54pm

Mr troll has suceeded in creating an argument.....

Gestalt

QLD

14722 posts

28 Aug 2020 10:56pm

Not sure it's an argument. We can argue bout if it's an argument.

Mr Keen

QLD

690 posts

29 Aug 2020 5:10am

Can't be an argument, quite liked Gesalt's answer

Ian K

4164 posts

29 Aug 2020 7:49am

Select to expand quote

Subsonic said..
Mr troll has suceeded in creating an argument.....

It's called "biting the hand that feeds you".

sailquik

VIC

6166 posts

29 Aug 2020 10:19pm

Select to expand quote

Gestalt said..
ka koncept 7m - 199x458 = .43
ka race 7m - 199x458
np racing evoxII 7.4 - 205x482 = .425
ga vapour 7.2m - 208x461 = .45
simmer scr 7m - 212x451 = .47
duotone warp 7m - 213x452 = .47

maybe im reading it wrong but here are the numbers. in order of boom length

OK. That is interesting.

A couple of things:

The boom length measurement is pretty much irrelevant. More relevant is the Luff length and the Sail Area. The reason I say this is that the clew eye in these modern race slalom sails is never on the trailing edge of the sail. It may be more relevant to look at the max chord of the sail, but we dont have published measurements for that and I think you would find there would be very little difference anyhow.
Also, to get a given sail area with a set luff length, unless the sail has a very different outline, it should be all that is needed for a good comparison. (You cant work out a AR number, but I dont think they are very instructive in this case anyhow.

Here are the luff lengths of the 2020 Simmer SCR and 2020 KA Koncept/Koncept Speed sails:

size - 5immer - KA
5.0/5.2 392 393
5.8/5.7 418 413 (the 419 measurement on the KA website was an error)
6.3 432 433
7.0 451 458
7.8/7.7 483 473
8.6 500 498

As you can see from this, the 7.0m was probably not the best example as it is an odd one out, and the next size up (7.8) is actually back the other way.

In any case, I stand by my statement that the AR of these sails is insignificantly different. Some ever so slightly lower or higher.

However, the previous model 8 batten KA Race sails were slightly higher Aspect. They were replaced by a 7 batten Race sail in 2019 whose luff measurements are within a cm of the Koncept.

Gestalt

QLD

14722 posts

30 Aug 2020 8:52am

interesting that the 7m is so different. i wonder why.

peterowensbabs

NSW

497 posts

30 Aug 2020 9:06pm

Select to expand quote

Madge said..
Foil sails and windsurfing sails are two different breads.

Firstly foil sails give lift, lots more than a windsurfing sail, yes you can use a windsurfing sail on a foil and vice versa but they are both different. Try using a foil sail when totally over powered and I tell you, they are terrible, they are more efficient by far at lower speeds.
Gliders are really efficient too and they are really high aspect but you'd never be able to rig one as the mast would be like 8m long.

Foil sails have much higher leech tension to get the foil up out of the water. Where as windsurfing sails give more forward drive.
Windsurfing sails can be used much more over powered too so the leech twists more. The luff curve shape is totally different on foil sails too, almost the opposite of a windsurf sail.

" Upright sails " as you call them also wouldn't work as at speed and when over powered you cannot then level against them with your body weight.

Also twist in the sail not only exhausts wind, it also flattens and changes the angle of attack of the luff angle when they twist which flattens the entry of the sail.

I know where you are coming from but when in actual use its a different thing all together.

Boat sails are different again as they can change so many settings when sailing compared to a windsurfer.

Pryde have in the past had battens that were horizontal to when the sail is raked but they didn't look very nice and when not fully powered were terrible.

If still unsure check out " Sail Rocket " its both raked back and at an angle and is the fastest sail craft by a long stretch.

I also wouldn't really call them battens are they are part of the foil but they are parallel.

I always wondered at the efficiency of the creases that appear in well down hauled deep cambered sails exhibiting plenty of twist, Im no expert (no need for the "judgey" keyboard worriers to shoot me down thanks too much of that on here in my opinion). I know, in say dingy sailing creases are a big no no as with racing yachts, so I've always felt it looks kind of "wrong" but will be the first to agree modern sails are faster and more stable than ever. Anyone have an informed explanation?

Jetlag

NSW

194 posts

30 Aug 2020 9:52pm

Select to expand quote

peterowensbabs said..

I also wouldn't really call them battens are they are part of the foil but they are parallel.

Peter, are you talking about wrinkles whilst rigged in the car park or whilst loaded up on the water. Many race sails are designed to be rigged with significant creases in the leach of the top panels (often with markers as to how much creasing should be seen). When loaded up however both the leach twists away and the mast bends to leeward (much more than a yacht mast) these panels then before much more taut. My sails only seem to get creases again when very overpowered, giving excessive mast bend and twist.

SaltySkiffies

NSW

28 posts

30 Aug 2020 10:31pm

Select to expand quote

peterowensbabs said..

I also wouldn't really call them battens are they are part of the foil but they are parallel.

I think the creases are just outweighed by the beneifts that a particular profile provides. On the skiff we don't worry about speed creases until we need to start depowering and we're running out of outhaul. I think given how thick the boundary layer is for air, the creases would have to be quite deep to have an impact.

End of posts

Please Register, or first...

Topics Reply