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blaze720 View Drop Down
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Post Options Post Options   Quote blaze720 Quote  Post ReplyReply Direct Link To This Post Topic: Sail Sizes
    Posted: 22 Oct 09 at 4:07pm
This was touched on in one of the threads recently - Are the claimed sizes reflected in the 'alleged' actual sizes as calculated by the software packages used by the major sailmakers ?.

The reason for this is that we have been working on the Halo rig.  On North's package the latest itteration is 11.59m  (and Hyde's latest development is a tad larger) and this might suggest that Halo was particularly large. 

The Blaze is thought by some to have a large sail and that proves to be nearly 10.4m apparently.  However it is natural for some arond any club  to lay one sail on top of another and make comment.  They did this locally when several Phantom ones were laid over a Blaze main.  They have very different outlines but by eye the Phant ones did look larger than a Blaze one - yet barside opinion is that it is only 9.75m - ie a fair bit smaller than the Blaze and that was my own impression previously as well

The North package puts it the Phant one at a calculated 11.24m - so on a relative basis at least it is actually nearer to Halo than it is to Blaze.  I was not sure about this except as a relative measure so also asked Mike Lennon of Hyde what his view was - he confirmed that the Phantom was over 11.0m on their package as well.

We have no axe to grind either way frankly - we are just sizing and developing our own sails to do a particular job and not too worried what any package might say or the size of rigs in any other class.  But it does suggest that Halo is hardly carrying a monster rig.  It is tall for efficiency of course but it does have 2.5m wide wings to deal with it - and it works wonderfully !

So any other views on sail 'measurement'  ?  

Mike L.
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Post Options Post Options   Quote Steve411 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 09 at 4:33pm
Interesting thread. I always wondered why the Phantom took weight better then an RS300 when the 300 main at 10m2 was supposedly bigger then the Phantom at 9.75. Now I know why (+ hull shapes and widths as well, obviously).
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G.R.F. View Drop Down
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 09 at 5:04pm
Obviously the laying one over the other in the boat park routine doesn't
take into account the depth of the foil and the Phantom has a deep belly,
more so than the Blaze.
It also from my very casual observation (My Pal has a Phantom)seems to
have a tighter leech than the Blaze (given my Blaze is kitted with Elvstrom
sails that someone told me were pants anyway).

Now also it has been my observation of the more modern Dinghy sails
which by their very nature are for the most part too big for humans to
handle above force three, so seem to be cut with shallower foils and large
amounts of negative luff than say a few years back this has the effect of a
smaller actual area over a given plan shape and of course the more twist
off up top once the wind puffs.


Having said all that my experience has been limited to the Alto, Blaze,
Musto, Phantom, L&V3000 and the RS600 which to me seemed the most
tuneable of all the dinghy sails I've studied.

Funny I was chatting away to one of the young 49er squad at Weymouth
about sails, luff curve and mast bends since they all seemed to have
astonishingly different Mast Bends, which he claimed seemed to make no
difference at all to their performance. Now either he hasn't got a clue, or
he thought telling me anything would just go straight over my head and
couldn't be asked, or they have a series production issue with 49er masts..

But and I note the RS100 is at least dealing with it. In my world you dont
make a sail until the mast bend is a given. I realise back in the day things
were different, but now with the understanding gained thanks to us in
windsurf world, the relationship between the mast and the luff of the sail
are so key to any design, it surprises me how loose this arrangement
seems to be in some classes.

Edited by G.R.F.
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jeffers View Drop Down
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Post Options Post Options   Quote jeffers Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 09 at 5:22pm

I think what we need to consider here is the difference between 'measured' and 'unmeasured' (or unmeasurable) sail area.

A Phantom's 'measured' area is officialy 9.75 sq m. Now take in to account areas of the sail which may come outside of the given measurement criteria (such as depth of cut, loose foot, etc..) and it would be quite easy to believe that the actual sq m of cloth required for the sail is much higher....

The Blaze sails (because they are OD) do not have to be measured after manufacture to ensure they conform to the class rules.

This is an interesting point though. I think someone quoted in another thread that a Standard Laser rig is acutally more like 7.9 sq m. Would be internesting to know what the 8.1 sail actually comes out as (might have to pick Mr Rooster's brain for that).

Just my 2p.....

Paul
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Post Options Post Options   Quote iansmithofotley Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 09 at 7:48pm
Hi Paul,

Funnily enough, I canít find anywhere in the Phantomís Class
measurement forms, for the sail, or spars, that states that the sail area
should not exceed 9.75 sq. mtrs. However, this is the sail area quoted in
most publications.

What the rules do say is that the maximum distance between the two
measuring bands on the mast should not exceed 5626mm, and from the
aft of the mast to the outer boom band should not exceed 2820mm.

Keeping things simple, imagining a simple triangle and the area of it
(base times height divided by two) gives a figure of 7.93 sq.mtrs.
Obviously luff curve, foot drop, roach and sail shape has to be included
on top of that figure but I would be surprised if it all adds up to more
than the approximate 1.8 sq. mtrs difference. I have no idea how these
things (outside the basic triangle) can be measured.

It would be interesting to know where the figure of 9.75 sq. mtrs
originated and why.

Ian   (Yorkshire Dales SC.)




Edited by iansmithofotley
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Post Options Post Options   Quote blaze720 Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 09 at 12:13am
From memory it was based on a Fireball main....  What is the 'sailmakers take' on that today and what does the Fireball main 'measure' today.  Has it's 'offspring' grown over time then ?

The key thing is to compare class sails on a like for like basis surely - the relative differences being more interesting than the absolute areas quoted perhaps.  So a Phantom sail is in fact 8.17% larger than a Blaze one and a Halo one is 5.78% larger than the Phant one in reality.  Should not be too tough for the larger helms as is being proved ! 

Mike L.
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Post Options Post Options   Quote jeffers Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 09 at 7:51am

Originally posted by iansmithofotley



Keeping things simple, imagining a simple triangle and the area of it
(base times height divided by two) gives a figure of 7.93 sq.mtrs.
Obviously luff curve, foot drop, roach and sail shape has to be included
on top of that figure but I would be surprised if it all adds up to more
than the approximate 1.8 sq. mtrs difference. I have no idea how these
things (outside the basic triangle) can be measured.

It would be interesting to know where the figure of 9.75 sq. mtrs
originated and why.

Ian   (Yorkshire Dales SC.)

Hi Ian,

I think you have hit the nail on the head there mate! There are things that cannot be measured when it comes to sails because they are not designed to be a flat triangle (which is how I believe the sail measuring system works). I did hear a rumour some time back that one of the ways to measure a Phantom main was to lay it over Simon Childs main, as long at it was no bigger it measured (this could be bar speak but it did come from a Phantom sailor)!

Other classes have much more involved measurements that make you fold the sail and take various measurements but that the end of the day you are still going to come up against the same issue.

Perhaps the classes who measure sails whould bring in a rule that you should not be allowed to use more than x sq m of sailcloth......

Paul
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 09 at 8:48am
There's a reasonable and repeatable method of measuring sail area already established. The IYRU (as was) designed in many years ago and its used by at least some of the development classes, one and two hulled. It seems awfully complicated, but in practice its straightforward enough when you've done two or three, especially if you have a spreadsheetto feed the numbers into. With square headed sails you have to do a little tweaking, which is allowed for in the full rule set but this section as listed is all you need for things like Phantoms.

Here you are...

3. Soft Sails set on Spars
3.1 When the sail is set on spars and between measurement bands the distance between the bands is used to obtain the primary dimensions of the main triangle.

3.2 Area using measurement bands

3.2.1 With battens set in their pockets the sail shall be pegged out on a flat surface with just sufficient tension to remove waves or wrinkles from the edoe rounds and to spread the sail, as far as possible, substantiallv flat. Once the sail has been pegged out in this wav all the required measurements shall be taken and no alterations to the tensions shall be made.

3.2.2 Needles shall be fixed at the head and clew, making allowance for that part of the sail inside the spars so that the distance between the needles is the length of the leech. A third needle shall be fixed at a point so that it is the distance between the measurement bands on the mast from the head needle and also the distance of the boom measurement band from the mast from the clew needle. If the boom is shorter than the foot of the sail or if there is no boom, the length of the foot shall be that found by measurement with the sail set on the mast. A thin line shall be stretched round these needles to define the main triangle. See fig (3).

3.2.3 The area of the main triangle shall be calculated from one of the following formulae or by a scale drawing.

(a) Area = SQRT(s.(s-a).(s-b).(s-c))

where s = (a+b+c)/2

and a = length of luff
b = length of leech
c = length of foot

(b) Area = ABx CP where CP is the minimum distance from C to 2 * the thread from A to B

3.2.4 The area of the luff round shall be calculated and added to or subtracted from the area of the main triangle. If the curve is fair and continuous its area shall be taken as two thirds of the product of the chord length and the maximum perpendicular offset to the chord. In fig (3) below the area of the luff round is 2g(AY)/3.The offset to the chord shall be taken as the maximum distance between the point on the sail corresponding with the aft edge of the mast, and the thread defining the main triangle.

3.2.5 The area of the leech round shall be found as follows:
either
(a) where the leech is a continuous fair curve from point A to point C in fig (3)
the area is taken as AC (1.16d + e + 1.16f)/4
where AC is the leech length indicated in fig (3); d, e and f are the perpendicular offsets between the points on the thread from A to C a quarter, a half and three quarters of the distance between the leech measurement points A and C and the edge of the sail. For the purposes of the measurement of the offsets, any hollows in the leech shall be bridged.
or
(b) where the leech is not a fair curve from point A to point C in fig (3) the area of the leech round shall be found by dividing the area into trapeziums, triangles and segments and measuring each. For the purpose of this instruction the area of a segment shall be taken as two thirds of the product of the chord of the round and the maximum perpendicular offset to the chord.

3.2.6 The area of the foot round, if the sail can be pegged out substantially flat, shall be measured in the same manner as the luff round.

3.2.7 Where the foot has a "shelf" or a substantial amount of shape so that when the foot is extended there is loose or bulging material above it, then the area of the "flow" of the bulging material shall be determined as follows (see fig. 4.. A measurement shall be taken from the straioht line joining the tack to the clew, in the wav of the greatest fullness, to an arbitrary point where the sail does lie flat. A second measurement is then taken from the arbitrary point to the point of greatest fullness following the folds or bulges of material. The difference between the two measurements represents the offset of the rounded foot. The area of the foot round is taken as two thirds of the length between the tack and clew multiplied by the offset.

3.2.8 The area of the shape BYTX in fig (3) is not deducted from the area of the main triangle.

3.3 Where there are no measurement bands on the spars

3.3.1 With battens set in their pockets the sail shall be pegged out on a flat surface with just sufficient tension to remove waves or wrinkles from the edges and to spread the sail, as far as possible, substantially flat.
3.3.2 Needles shall be fixed at the head, tack and clew. A thin line or thread shall be stretched tight between head, tack and clew to define the main triangle.
3.3.3 The area of the main triangle shall be calculated in the manner indicated in Section 3.2.3 above.

3.3.4 The area of the luff, leech and foot rounds shall be found in accordance with the instructions 3.2.4, 3.2.5, 3.2.6, 3.2.7 above.




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Post Options Post Options   Quote Scooby_simon Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 09 at 11:26am

SCHRS and most Formula Cat classes use the ISAF model.

Main Sail Measurements

CM - Area of Main Sail + Mast + Boom

  • S1 = ((h + h1)(a - a1) + (a1 x h))/2
  • S2 = c x h2/2
  • S3 = 2/3 c3 x h3
  • S4 = c4 x h4/2
  • S5 = 2/3 c5 x h5
  • S6 = 2/3 c6 x h6
  • S7 = 2/3 a x h7
  • S8 = 2/3 b x h8
  • CM* = (S1+S2+S3+S4+S5+S6+S7+S8)m≤
  • Area of Mast0 = (Total Length x Perimeter / 2)m≤
  • Area of Boom1 = (Total Length x Height)m≤
  • CM = (CM* + Area of Mast + Area of Boom)m≤

* intermediate calculation if other conditions apply
0 only applies to rotating masts
1 does not apply to boomless sails or if height is greater than 1.5 of breath

 

http://www.schrs.com/measurements.php

Works well for us!

 



Edited by Scooby_simon
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Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 09 at 11:38am

Funny that a metric in which people put so much faith can have such variance.

I suggest there is a similar issue with manufaturers claimed hull weights ...

There is often a significal difference between what it says on the marketing materials & the reality of what the boat weighs.

I have always weighed my new boats and one or two showed up quite different to my expectations based on the marketing materials only to be told  "they all weigh that ..."

Here is the breakdown of my Musto weigh in ... sad I know ...

http://www.mustoskiff.com/sub-pages/weight-breakdown.htm

But as an ISAF class all boat got weighed at the Worlds and everyone was happy so Ovis are making very consistant boats.



Edited by Guest#260
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