totally agree with you all on this one. we need manufacturers of masts and sails to give all the facts.

seems some of them won't so we should do it ourselves.

to start the ball rolling

maybe we should assume that powerex are the true constant curve?

if so then you can include art masts in that as well and also KA masts,

yeah i know. i'm a KA girl but what can i say. they rock and rig on lots of different masts. also i can rig from a 7m down to a 5m on a 430 mast and a 5.8 down to a 3.3 on a 400 in powerex/art/KA/ masts etc. plus their website has lots of advice with regards masts on there sail range when you look in the forums.

north sails also have the one mast fits all range thing goin on. i am a very big fan of north sails. but i don't use them anymore cause i need a north mast. (big shame) they rig poorly on powerex / art mast i can say for sure.

also i can say that neil pryde masts don't work well in north sails.

i know lots of others out there have the same experiences to share and there are lots of other brands that make sails to fit true constant curve masts and are more forgiving in masts that aren't perfect in bend......

so whats eveyones experience. and keep it positive

There are probably enough people on here to get a fair sample of different masts.

I propose a bit of backyard experimenting. Drag out the sawhorses, a drum of water, or the weights off that weights bench that you used to use once.

Support the mast at, or very near (50mm) to the ends, load up the weights at the halfway point. 30kgs is ideal - as used in IMCS testing, but probably anything over 20 will be enough for an indication. Run a string line across the top, as long as it's the same both ends, it shouldn't make any difference (for this purpose anyway) whether you run the string to the very end of the mast, or to the point of support.

Keep it easy, and take 7 measurements (ALONG THE STRING). Measure to the halfway, then halve that, and halve again.. you should get seven points, plus the ends.

Measure the distance (in mm) from the tight string line to the top surface of the mast vertically below.

If we keep it standard and record measurements in order from the bottom of the mast to the top that'll help.

A constant curve mast should look something like:
0,A,B,C,D,C,B,A,0 regardless of the weight used.

Post your results, along with the weight used(in kgs), mast brand/model, length, IMCS according to the label, and maybe the age?

I'll start tonight and post a couple of masts worth of numbers to get things rolling.

Sounds too hard to me
Lets just have a database we can all add to like this, and keep the reasons short.

Don't use an ezzy RDM in a KA sail (too stiff)

TelecomGreg

quote:

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Originally posted by nebbian

Fantastic idea 555, although I'm not sure that this statement is quite true:

quote:

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Originally posted by 555
A constant curve mast should look something like:
0,A,B,C,D,C,B,A,0 regardless of the weight used.

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According to this site: www.peterman.dk/windsurf-mast-article-gb01.htm

It is evident from the scale that "Constant Curve" doesn't mean that the mast is equally soft (or stiff) from the bottom to the tip. Constant Curve means that if you hang a weight of 30 kg from the midpoint, the mast deflects 10 - 12 %-points more at the 3/4 point than at the 1/4 point. No more - no less.

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So.. Constant Curve isn't really Constant Curve?! But instead it's a name for a particular bend curve.. Hmmm.

I'd always thought that constant curve would be what you got if you drew a huge circle, and then made a mast who's bend matched a chunk of it's circumference. But there you go. More ambiguity in the mast world!

Even more reason to get measurements from a bunch of masts and see what's really going on!

quote:

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Originally posted by mathew

Excellent idea. Some points:

- for it to be useful, everyone should use the same distances and weight to determine the mast curve-type - although, using different weights might be handy for light vs. heavy sailor comparisons.

- if we are going to the effort of setting up the test on each mast, we might as well measure more points; this will be especially useful for flex-top/bottom masts.

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All fair points. May as well be as scientific as you're allowed to in your own back yard.

100mm separations? I think we should measure the separations along the string, rather than along the mast. That will also allow you to set up a string, and mark it once instead of measuring for each mast individually. I also think we should run the string from top to top of the mast ends as this is easier to reproduce, and probably more consistent than approximating the 'point of support' on the top side.

Weight wise - I have some plastic 20 litre drums which are pretty common everywhere. (the almost cube shaped ones with a molded handle in the top) It would be easy to use one drum, so 20kg, but better to be consistent with the IMCS measurement and use 30kgs.

I don't think that changing the weight used is analagous to rider weight, as it's more a simulation of downhaul, than rider specifics.

I was trying to keep it simple so that people like TelecomGreg could join in, but obviously that was a miserable failure!

Don't make the misconception that just because masts are made in the same factory that they behave the same. Everyone uses their own specs, parallel example I guess is the cobra factory for boards.

cracks are a god sine that you haven't got a good mast

hi pc simpson, (great movie)

yes it's a big box opened. i think it would be a positive move for the sail and mast manufacturers to list the data. it will mean more sales for them. now i know that sailworks make sails that rig on masts similar to what i have i will consider them in future. both masts and sails, before your post i wouldn't have taken the chance.

i am sure there are lots of other products out there i won't consider because i am concerned about the same thing when they are perfectly good for the job but i don't have that knowledge.


nebs, 555, mathew, tg and crew.

i agree that we should probably measure the masts too. we need someone to post a how too so we can all use the same measure.

what ever is used weights wise needs to be exactly the same for everyone. we need to compare apples with apples.

i reckon the peterman method is a good place to start. but we should add in a few more points to get 7 positions like mentioned by ben severne.

also, if any of the sail and mast manufacturers reading this already have the data then why not post it. would be a very helpfull outcome.

cheers

quote:

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Originally posted by decrepit

The 3 musketeers, (hardy, elmo & decrep) found out what not to rig a 6m gastra speed sail on today. Just won't go on a N.P, elmo tried to force it and broke the brand new batten tensioner, (hardy was not amused!) Well elmo did manage to get the camber to engage the mast, more than hardy and I could do, trouble was cam tension was so great the sail wouldn't rotate, even with hardy's weight pumping it.
The 7m did rig on an ezzy skinny, but this had the opposite problem, no cam tension at all, in fact the cams were only just engaged, I was worried a big pump would disengage them.

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jeezzzzzz,,, don't tell me you guys elmoed the team challenge prize i am yet to receive.

Hardy
Sorry mate the masts are on the way.
Ok on the 7.0m there are cam spacers available to push the cam out the extra few mm that is the difference between RDM and SDM. This will solve that problem.
Re the Vapor 6.0 is it only the batten tensioner or is it the cord that holds it in? I can send you a new tensioner.


Like someone else said in this post the sails are made to the masts but then say there is a need to chnage construction ie for re-inforcing etc. The mast bend changes from this. Making a mast that has a specific bend curve is no easy task it's more taking something within a pretty loose tollerence guide line and making the sails work based on what the mast maker gives you in terms of material and re-enforcing spec. Some makers have had the same forever ie fiberspar and powerex while others NP Gaastra and others have changed. Due to changing materials and/or factory or even moving the factory which has changed the mast characteristics. It's also a very short period of time between when mast samples are ready to use for sail deisgn and when the final sail design must be on the market.
It's true not all masts are the same out of the one manufacturer ( the case in point being a certain Italian maker). But this is due more to quality of materials, re-inforcing spec "which really means price" and the machine used rather than the sail makers wanting a very specific bend curve. They try to get the same bend curve across different Carbon contents etc but it is not always the same and especially not between SDM and RDM.

Really I think you will find when you do all these measurements that the differenc as a percent chnage across brands is lexx than 10% and that the masts all coming from the same factory have more like 5% difference if that.
As Neb said it is also important to note how the luff curve of a sail reacts with the natural bend of the mast under specific load or downhaul tension. As it has already been noted you will need more outhaul on the flex top masts rigged on sails designed for CC masts.

I also think it's not really in the interests of the manufacturers to tell you their mast secrets this is really the only thing they have up their sleeve to make their sails a certain way that is hard for the competitors to copy. If the dail maker goes to make sails on a different mast it will take him a couple of seasons to re-create the same set and feel from his sails on the old masts because they are constantly tweeked all the time through feedback from the riders etc.

Anyone have a copy of the May 2007 UK Boards magazine?

http://www.boards.co.uk/equipment/mastsweb/mastsoverlay.html#

Neb - I agree totally, hanging a weight off a mast does not accurately simulate rigging a sail on it. BUT.. given that each sail is different (or we wouldn't be having this discussion) and that we don't all have the same sail, we need to come up with a standard way of inducing the bend so that we at least have consistent numbers to compare across different masts.

Either by weight, or, as Boards mag have done, by tensioning it so that the midpoint deflection is a specific value. Their method looks a bit extreme to me though!

Perhaps someone can measure a "constant curve" mast with a sail rigged on it and see if it really does have a constant radius. I have a mast, but not a matching sail that is supposed to be rigged on "constant curve"

My thought is that if we measure a bunch of masts and determine that Mast 'A' has a very similar curve to Mast 'B' when subjected to a standard test, and we also know through experience that a particular sail will rig well on Mast 'A', THEN.. we can also be confident that the same sail will rig nicely on Mast 'B'.

There are two parts to the equation really:
1) identify a mast with a curve that works for a given sail.
2) identify other masts that have the same or very similar curves.

That should give us enough info to answer the popular questions like "I'm buying a new KA speed sail, do I need to buy the matching KA mast, or will the Tushingham mast that I already own work just as well?"

Sure, some people can afford to buy the factory recommended mast for each new sail that they aquire, and for them, this is all totally irrelevant.

quote:

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Originally posted by Gybesports
If the dail maker goes to make sails on a different mast it will take him a couple of seasons to re-create the same set and feel from his sails on the old masts because they are constantly tweeked all the time through feedback from the riders etc.

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Thanks for the reply Gybesports, it's good to hear from someone who's actually in the industry.

What percentage of your sales would go towards weekend warriors, who value longevity and standardisation over a super-tweaked design? Obviously there are people there who update their quiver every year, with the latest and greatest masts and sails, but as far as I can tell there are lots more weekend warriors out there than super-speed freaks. Maybe I'm wrong.

I'm sure that most people understand that manufacturing tolerances can change a curve slightly, but the issue I have is manufacturers (Pryde? Gaastra?) deliberately and dramatically changing the curve of their masts, possibly to make them incompatible with other brands. That's a deal-breaker for me, and means that I will never buy any of those particular brands again unless I start making gobs of money.

Unfortunately when you start out in this sport you don't understand any of this, you think that if you buy a sail, and then buy a mast that matches the size and IMCS that your sail requires, then it will work perfectly. I wonder how many people have made the same mistake that I have, and thrown money away on components that don't work together properly? At the moment I feel that it's a bit of a lucky dip as to whether or not the sail you buy will work with the mast you already have. And there's no definitive way of knowing without rigging it up.

Of course, if mast manufacturers started printing the IMCS bend characteristic on their masts then that would work fine, and alleviate a heck of a lot of confusion.

As soon as I find a 30 kg weight I'm going to pull out the tape measure and start filling in 555's database. Until then, there's a good start located here:
www.peterman.dk/masts-all-imcs01.htm

We know by experience that certain brands of masts, suit particular model sails -> the idea is this type of test is to standardise the technique for mast measurement so that when you purchase a sail, you have a fairly good idea that it will work with your existing masts. Having a "recommended mast to sail guide" is a good idea too, but that is not the purpose of the mast testing - they are separate datasets, both equally useful.

The reason that simply rigging is not good for mast testing is:
- every brand/model sail cut differently and so will load the mast differently
- boom heights differ between sailors
- the amount of downhaul and outhaul tension depends on the type of sail, conditions, sailor weight, etc.

If we wanted to go to extremes, we could also post our downhaul and outhaul settings + body weight, so that others could use that info.

Great points Elmo, I give you a green thumb for that

Out of curiosity, has there ever been any study on mast curve etc. over time? By that I mean with the same mast, i.e. do the bend characteristics change as the mast gets older???