PDA

View Full Version : Objectivity ?? Measurements ???


Floyd
17th August 2011, 06:51 PM
I know its an old topic and has been moaned about loads but isnt it high time manufacturers got their acts together with the SIMPLE measurements.. I know its hard to determine subjective isues like board performance/gybing characteristics and handling of sails etc etc ..

Went out other day with my 6.5 Maui Pursuit. Its a great sail ;plenty of range, light and stable and quite fast... Mate was on an Ezzy 6.3.. Wind picked up and we decided rather than change down take the lazy option and downhaul more !!! (we`ve all been there)

We both coped but my sail was seriously on limit if not over it at times.. (I was fastest mind)

He looked and insisted (as sailors always do) that he was fine... Was beginning to think I need to get an Ezzy but after session I checked out his sail stats..

Ezzy 6.3 .,(as set) 458 luff.. 190 boom

And mine

Maui Pusuit (as set) 470 luff... 198 boom ..

Thats 12cm on luff and 8cm on boom !!!.

My sail was bigger??? Supposedly by 0.2 m. Its way more than that !!!

Its like buying a 2 litre car; having it measured and it been 1800cc and somebody elses 2200cc !!

Crazy !!!!! And why ?????

nakaniko
17th August 2011, 08:10 PM
I'm not an expert so sorry if things I say are not correct, but...
They seems to be different sails with totally different shapes so this could be the reason. Note that my old Gaastra GTR 6,5 from Barry Spanier has 463 mast and 203 or 205 boom, my newer HSM Speed Demon 6,5 has SAME mast lenght and 193-195 boom. Both 7 battens nocam, imho no relevant difference in power (but meanwhile I changed board), only SD is more direct but also more easy to rig over the FS 4600 (suggested GTR mast...).
Looking at both sails pheraphs Pursuit is a FR-FC nocam (like all my big sail, so less prone to be used owerpowered, but I suppose with more low end. Ezzy has his classic exposed head and comes from the ten years old classic shape of all ezzy wave sails.
But yes, some obiectivity would be appreciated, none is checking as I know the real sail dimension when testing, could it be with an engineer device? I don't know.
But the thing I could be mostly interested is about the REAL weight of a board, so pricy and you don't know if the specs are about a fully naked board (without pads - absurd), or with pads straps and fin (abdusrd on the other side, imho fin is underwater so weight changes a lot). There isn't a common rule. Finally a wet-straps test could be useful, as some board has heavy 4 sponges... Some tests show big differences from declared to real weights.
All imho

davide
18th August 2011, 12:08 AM
I noticed that different sailmakers measure sail surface differently many years ago, it might have to do with the fact that a sail is three-dimensional, not flat. But whatever the reason I only buy sails from the same sailmaker effectively solving the problem.

Floyd
18th August 2011, 02:27 AM
Agree with what you are saying Nako but even taking (slightly) different plan shape of sails into account there is still no way the two sails mentioned are only 0.2 m different in size !!!

IMO manufacturers build different styles of sails and then "manage" the sizes to accomodate the desired outcome. (Eg Power wave sails are always bigger than normal wave sails) Ezzy are designed to be good in strong winds so they build them small !!!

Davide

Sails are not flat but all sails require a certain amount of material to build them; I`ll guarantee manufacturers know exactly to (high degree of accuracy) how much material goes into the sails ! ie when they pay for materials) Anyhow its still not an argument for not measuring sail area correctly;its not difficult !!

BelSkorpio
18th August 2011, 03:09 AM
The approximate surface area of modern race sails follows a little bit this formula:

Luff size x Real Boom size (you need to add the extra length to the reduced boom size) / 1.4

Floyd, for your sail examples, perhaps not real race sails but I don't care, and I presume no reduced boom length it sums up to:

4.58x1.90/1.4= 6.22 m2
4.70x1.98/1.4= 6.65 m2


So, for sure not 0.2 difference but rather 0.4 difference which is not that far away.

Floyd
18th August 2011, 04:52 AM
Like the Formula..

You are right, its not that far off (closer than I`d imagined)but far enough to produce significant differences in power /stability especially at sail`s limits.

Seems a shame that we cant rely on measurements when we are involved in a sport with many things that cant be quantified..

Volumes/Weights/Sail area / mast stiffness and others all seem to produce anomolies... Things which in industry would be specific and measured accurately..

As customers we just accept it ???

Might just buy the Ezzy`s ???!!!

pxlwz
18th August 2011, 12:28 PM
I assume, you rigged your pursuit on the correct MS mast to specs (measured from the top of extension ring to bottom of the furthest pulley), you weigh the same as your mate, used the same board and fin as your mate, and are at about the same level as your mate. If any of the above does not apply, that could explain why you felt at the limit, and your buddy did not.
Did you switch boards with your buddy?

I weigh about 160lbs, and always have to over downhaul my TR race sails by at least 1 cm, for them to feel light.
I also have a buddy (about the same weight as me) that has iSonics, and he is always 0.6 to 1 m bigger than me. I could not handle it (Exocet boards), but I plane earlier than him on the smaller sails.
Numbers are just that: A number to start from.
Good luck !

Pxlwz

Unregistered
18th August 2011, 06:38 PM
Cant believe folk would argue against a post which so obviuosly true..

Irrelevant to differences in rigging;skills;conditions ;fins the two sails mentioned are clearly not correctly measured in their area...(or one of them isnt.)

And Davide`s point is also irrelevant.. So what if you only use one manufacturer that does not make it ok to measure area wrongly and besides points made apply within a manufacturer. (Eg compare NP Search and Combats) NP obviously do not use same process for arriving at area for their different ranges..

Weights are invariably out.. Weigh your board..

Volumes are always wrong/out/adjusted.

Compare stiffness of a Tush C45 with a Tush 100%.. Both same IMCS rating !! No way are they same stiffness !

Compare an RDM with an SDM of equal IMCS... Loads different..

Manufacturers print what suits them on specs.. (Many sails dont even rig to spec written on them !!)

Measure your boom ..

Mine says 160 - 220 on it... Its 163 to 223.. Not much I know but why ??? Bought it thinking it would be fine for a sail needing 158cm... Thats 1cm short and boom 3 long; Gap of 4cm !!! Sails fine but it just shouldn`t happen !!!

Or perhaps I cant use a tape measure !!!

davide
18th August 2011, 11:35 PM
Davide

Sails are not flat but all sails require a certain amount of material to build them; I`ll guarantee manufacturers know exactly to (high degree of accuracy) how much material goes into the sails ! ie when they pay for materials) Anyhow its still not an argument for not measuring sail area correctly;its not difficult !!
Oh yes, I agree, but what I was hinting at is that "we users" cannot really measure the surface of a sail by simply considering its luff/boom dimensions.

pxlwz
19th August 2011, 12:28 PM
Floyd,

According to Mauisails (the remeasured the sail), it is 6.52m

You can check their forum.

I have to give it to you: Feeling, that the sail is .02 meter bigger, than it should be:
I am impressed!

Pxlwz

joe_windsurfer
19th August 2011, 06:12 PM
http://www.mauisails.com/forum/viewtopic.php?id=3425

AND forget the "formula" where one divides by 1.4 !!

Diplomat
20th August 2011, 02:42 AM
Still plenty of arseholes on Forum then !!!

Unregistered
20th August 2011, 04:45 AM
Calm down everybody !!!

Joe
I wasnt freaking out; I swear more when I do that..
..
Could well be that Maui Sails measure accurately but I suspect all manufacturers claim to measure their sails accurately and perhaps they do in their own "accurate" chosen manner but there is obviously some discrepency accross manufacturers.

I was well aware of the fact that boom/mast length are not the only parameters to be taken into account but they are a guide. ( Just been looking at a North 6.5 (???) with luff of 480 and boom 200 ??!!! wonder if they justify their measurements aswell ??? Is there an industry standard for measuring sail area ???

My point was and still is there is a lack of objectivity in our sport involving even the simplest of specifications..

Dont get me wrong; as I stated in the first post, the Pursuit is a fantastic sail..The was no criticism of any single manufacturer..

Couldnt log in for some reason.,. (Perhaps SB have banned me freaking out !!!)

Good winds.

Floyd

UnregisteredFloyd
20th August 2011, 04:14 PM
PS
I also said "as rigged"..

Find (my) Pursuit works better rigged on 470 mast length (10cm ext) pulling sail to 469 (ie with a 1cm gap betteen sail pulleys/mast ext pulleys) and fully down when overpowered. And yes its on a good spec mast ! (460 Tush 100% C or Gun Terminator 75% C,rigs identical on both;Tush obviously lighter)

joe_windsurfer
21st August 2011, 05:56 AM
MS is considered HARD top
GUN is high end CC or constant curve
and TUSH is definitely FLEX TOP or WRONG for MauiSails/MS !!!!
see http://www.unifiber.net/2011/mast-selector

my point in following up this post is:
MS sails are good sails for the money and well supported
if one has ANY questions or criticism i suggest you use their forum
that was all
and i was not freakin out either floyd
i need no swearing for comedy nor freakin out :)

Farlo
21st August 2011, 04:51 PM
Windsurf is not less objective than garment for instance. My shoe size varies from 41 to 44 according to brand/models and so on with pants, shirts, jackets. May be an inherent unaccuracy in textile manufacturing or changes happening between design and production, plus each brand may have his own method of measuring. Anyway you can't compare different sail models by their "exact" surface, whatever it is. And for similar cuts, boom length seems a better raw indication of power. IMHO the top is designed for low drag so a few more cm do not matter that much. This been said it is true that board volume could and should be accurate, although it is just one amongst many factors. Over the years I've been trying dozens of 100ish boards. Some were real pontoons and others semi-sinkers (for a stable bodyweight of course).

Ken
22nd August 2011, 10:49 PM
I am delving into an area where I have no expertise, but it seems like you could take photo of an unrigged sail from above, laying flat in a specific sized space (say a 6 meter square box or smaller for smaller sails) outlined with a line.

With the photo and some computer software, it seems like one could come up with a program that would instantly give you the "sail occupied" space inside the box, thus providing the exact size of the sail.

This way, everyone making sails and using the same software would be able to measure sail size consistently and accurately. A universal process, isn't that refreshing.

UnregisteredFloyd
22nd August 2011, 11:55 PM
Nice one Ken..
Perhaps we could put Farlo`s shoes in it too !!!

Good winds

They still aren`t letting me on !!!

Always though Tush were constant curve (and Gun ??) NP are flex top ??? Learn something everyday...

Unregistered
25th August 2011, 06:45 PM
Think some posters are plain thick !!!

Original poster didnt say his sail measured big ; he did not criticise his( or any other sail for that matter). He pointed out ,quite rightly, that there are discreprencies in measuring AREA of sails acrross manufacturers...(and sometimes within ).This is a fact....full stop...Why the advice about masts ???? Whats that got to do with AREA. I have a Gaastra 7.5 GTX; in size terms it equates to an 8.0 in other manufacturers (or other years perhaps) Its something we learn to deal with by using sails but there should be more uniformity in measurements.

Poster no.19 ; are you poster 10 ?? If not try and be original...


There should be more objectivity in our sport...Fact.

carlosgp5
25th August 2011, 09:17 PM
The sail is not a triangle, the width of top (from the leech to the tip) will completely affect the sail area.
I think so, anyways...
Cheers

Farlo
26th August 2011, 12:58 AM
Hi Carlos, this is true but the top of modern sails is mostly designed to release excess pressure. It's pretty obvious on some models where the whole upper part will dangle down sadly when rigged. IMHO comparing surfaces whether or not accurate gives only a very rough indication, notwithstanding other factors (design, mast, downhaul, etc).

carlosgp5
26th August 2011, 02:31 AM
Yeah Farlo,I might sound dumb, but the first poster didnŽt make sense to me... lenghts of luff, and boom donŽt give sail area.
If I understood your post, you say that with the sail rigged and fully downhauled, the upper part, where the leach is open, would not count as sail area?
I find this subject very interesting...
For example, now severne has de Overdrive 11, and the Overdrive 11 light wind. If you get both unrigged and put on the floor one on top of other, you realize the differences in boom lenght and top width, however, both should have same area.
IŽll give it a try sometime, IŽll photograph and measure it on a Cad software, as someone gave the idea on previous post.
Cheers

Unregistered
26th August 2011, 02:35 AM
You can change when rig depowers with mast choice and even amount of power available with adjustments but no matter what you do you can not alter the sails area. Rightly or wrongly it is the paramater we choose our sail`s by for that reason alone it should be measured accurately and by same process accross manufacturers.

Its not complicated.

Just measure the sail area by same method properly

Farlo
26th August 2011, 04:28 AM
Hi Carlos, the upper part counts as sail area but difference in boom length, or in the overall profile of the sail, have a lot more impact, I think. And yes it is certainly possible to measure sail area properly, however it may not change our life or make sail choice easier. I guess the Overdrive and the Overdrive light wind have completely different behaviours for the same surface.

Ken
27th August 2011, 12:38 AM
The basics we all want to know:

Board length, width, volume

Sail size, mast length, boom length

It seems so simple, but variations or misrepresentations do occur. Finally, Starboard got away from the "virtual volumes" on their boards and got real.

As with boards, different sails that have the same basic measurements do and should vary considerably in performance. We use them in different ways so design/performance specifics will vary based on what the designer was trying to achieve.