If a race sail is rigged with a mast that is too hard or soft in the top, what will it look like? Is it possible to look at the rigged sail and say "needs a harder top mast" or "needs a softer top mast"? Or perhaps "needs a harder mast" or "needs a softer mast"?
I recall an article that described how Antoine Albeau rigs new sails on a dozen masts to find the best one (without taking them all out for a test ride). But can regular windsurfers do that?
Background:
1. I have a Maui sails TR7 for which I bought a MS SDM mast from the same year. The sail never looked quite right, regardless which outhaul and downhall settings I tried. A couple of years later, a MS team sailor told me that the TR7 sails did not rig right on MS hard top masts - they needed a softer top.
2. We got Loft Racing Blades specifically because they also rig on RDM masts. On both Loft RDM masts and other constant curve RDM masts, they look quite different from SDM masts. On Loft SDM masts, there's a lot of looseness visible in the top, but on RDM masts, the looseness is further down, and does not show much in the top. The profile is also shallower in the RDM masts (but the sails still work quite well).
I just got a second Ezzy mast, and now have both 460 and 430s. Ezzy lets you mix different mast tops and bottoms, and the RB 7.0 has a 470 mast sleeve. It usually rigs on 430 with 40 cm extension, but I could try 4 Ezzy combos now: 430 top + bottom, 430 bottom/460 top, 460 bottom/430 top, and 460 top + bottom. So my question is: what exactly should I look for when rigging the sails to get an idea which combo might be best on the water?
From my understanding a sail made for CC mast rigged with a "soft top mast" the top of the leech gets very loose before correct downhaul is achieved and there's heaps more shape down low.
The same sail rigged on a hard top mast has the opposite effect ie takes more downhaul to get the leech to loosen and the sail is a lot flatter down low.
In saying that I've seen maui sails rigged on CC / Pryde masts and they looked quite good, so there mast be variations in how masts are built.
Obsession with "perfect" sail shape.
Case in point....your Loft sails offer rigging with either RDM or SDM. Both are completely different from each other. It's up to the sailor to try each and decide for him/her self which should be used.
You see this in rec sailing. Some like max downhaul all the time.
Some like tight leech.
Some like baggy shape.
Some use tight outhaul.
All seem to work.
Choco's explanation is what I have found in general when testing different bend masts in sails 
But there could be differences in the effect of changing masts in different sails depending on the way in which sail designers achieve the shaping of the sail. i.e. the amount of shaping from the luff curve and the seam shaping and the combination of both.
RDM v's SDM sail shaping is a bit different. In my experience is that RDM's bend differently from SDM's. generally, RDM's naturally tend to be more CC because of their shape (far less taper from bottom to top) which means they rely more on layup construction to vary the bend curve. But also the stiffness and curve sems to vary different as the mast is actually loaded. Two masts, one SDM, and One RDM, which test the same on the IMCS test, can have quite different dynamic flex characteristics, and can shape a sail differently. In my experience, with the sails i have used and tested, I never get exactly the same shape from a sail when I switch between RDM and SDM, even if the UMCS test data is the same. It may be that Loft Sails hove found some design ways to minimise this, but there must be a difference.
What I suspect is, that the larger diameter of the SDM carbon masts more progressively resists bending as it is loaded and bent further. This is why RDM's often give a 'softer' dynamic flex feel in sails, and SDM's often rig race and slalom sails deeper in the lower half (and often with more forward draught) than SDM's with the same IMCS test curve and stiffness values, and the same amount of downhaul.
This is something i have been meaning to test with an experiment for quite a while now. In this respect, it should be enlightening to test masts with more and less deflection weight in an IMCS type test.
I have said it here before. My most powerful tuning tool for sails is trying different masts. A sails characteristics can be tuned quite well this way to suit a particular sailor weight or purpose. i have a set od RDM masts that have interchangeable tops and bottoms between sizes, and this is something I do use to experiment with sail tuning as well. Shorter and longer masts can also be used for tuning. Shorter masts are softer in the stiffness when extended, but when you use them in a sail that specifies a longer mast it also moves the mast further up the luff sleeve which can change the overall bend curve enough to make a difference, especailly with SDM masts.
Bugs says the thing to look for is entry angle, this should be similar over the whole luff. If not part of the sail can stall, usually the top. I guess in some cases this may be desirable, I don't know enough to say.
Sails with very flat tops will need a lot of twist to achieve this, but sails that have some draft at the front all the way up won't need as much twist.
Waricle took some pics of us at Liptons on Monday. It's very interesting to compare the twists. I'm the bottom one with a 5.2 KA speed, this has less twist than the others, but for my weight I went very well. (it was very intermittent gusts, so I may just have been lucky). The speed has a bit of shape forward all the way up, so doesn't need a huge twist, can't answer for the other sails, I'm not familiar with them.
I think it's worth trying to tune for similar entry angle, (under load of course), and see how that feels/works. Light and effortless and fast is what I'm looking for. A heavy feel is a sign of drag
Thanks guys.
Choco: everything you said matches what I've seen. I have also seen plenty of MS sails on constant or soft top masts that looked great.
Decrepit: I find the entry angle part a bit confusing. Not sure how that relates to differences in wind speed by height, or the advice to have little tension in the top battens, or that the loose in the top part of the sail acts to minimize turbulences. But since Bugs knows a lot more about sails than I do, I'll have to think about this some more. The pictures from Liptons seem to show quite a bit of twist difference, although the angles are also a bit different.
Sailquik: The Loft sails seem to rig quite differently on RDM vs. SDM. I think you got a very good point about the bend curve changing as the load increases. The typical number used to describe bend curves relies on just one measurement, with a force that's probably a lot lower than what a typical race sail needs. From the shape, I can see how a SDM mast might measure as "constant curve" under light load, but behave more like a soft top mast under increasing load. In contrast, an RDM mast with more even diameters would have a bend curve that changes less under increasing loads.
For the Racing Blades, my impression is that they rig with a deeper profile and therefore more power on SDM masts. If the top in the SDM masts is effectively softer, that would allow the sail top to "breathe" more in gusts, and keep it controllable. For a given sail size, the RDM would give a bit less power at the low end.
I agree that trying mast-sail combos on the water is what ultimately is most useful. But practically, the wind changes by several knots in most sessions. If I stop in the middle to re-rig, it's hard to tell the differences from changes in the rig and changes in the wind apart. Plus, who wants to stop in the middle of a great session to re-rig - especially in the winter when the days are short, anyway?
That's why I gave up trying....too much shoretime and on the water adjustments.
As you said, the wind is constantly changing, and my former practice partners all quit windsurfing decades ago.
Peter, I think there is a difference between the speed sails and the race sails.
There is less wind pressure going hard downwind, I have the feeling that turbulence is less of an issue than going hard upwind with heaps of sail pressure.
And yes the angle of attack should be relative to air flow, not the rig.
I haven't heard the advice to leave upper battens loose, I guess that could allow some shape near the mast.
Select to expand quotedecrepit said..
I haven't heard the advice to leave upper battens loose, I guess that could allow some shape near the mast.
Letting the upper battens loose is a bit of an overstatement. They are still tight, but not nearly as tight as the lower battens (including one or two above the boom), so the top battens are more or less straight, rather than inducing a profile. I'm pretty sure I have heard the same advice from multiple good sources, both for race and for freeride sails.
Just rig it and try it. Shape on the beach is not as relevant as shape on the water when loaded.
The top battens should be straight and tightened only enough to take out sleeve wrinkles. The battens get more curvature, and more tension, as you go down. That is the oversimplified ideal, but, again, rig it and try it.
Seen some top racers tighten out the top 3 battens, then slowly loosen until wrinkles appear, then tighten half turn.
Looser top battens allow the tip to follow wind direction at speed. No drive needed up there once up to speed.
Used to reverse top 3 battens of my Speed Slalom sails in 1987
Select to expand quotesegler said..
Just rig it and try it. Shape on the beach is not as relevant as shape on the water when loaded.
The top battens should be straight and tightened only enough to take out sleeve wrinkles. The battens get more curvature, and more tension, as you go down. That is the oversimplified ideal, but, again, rig it and try it.
Watching s few rigging videos most PWA sailors crank heaps of pressure on the top head batten.
You missed the whole segment AFTER they fully tighten their top battens, to stretch the material, wait 5 minutes, then they loosen the tops to slight wrinkle, then tighten just a bit.
Itxs a 3 step process.
Some guys do this every few sailing days.
I did not see the videos, but I have been rigging next to top racers at least 70 days a year for the past 35 years.
Most don't share their secrets, so watch from afar.
Select to expand quotechoco said..segler said..
Just rig it and try it. Shape on the beach is not as relevant as shape on the water when loaded.
The top battens should be straight and tightened only enough to take out sleeve wrinkles. The battens get more curvature, and more tension, as you go down. That is the oversimplified ideal, but, again, rig it and try it.
Watching s few rigging videos most PWA sailors crank heaps of pressure on the top head batten.
I tried this choc didn't work for me at all.
Peter. I have the same little 4-9 loft racing blade as Nina. Always ran a unifibre rdm with same results fairly flat on the bottom ( daffy always commented on this )and plenty of twist on top but still great speed and nice across the wind had spare sdm cams from my new KA used them with old 100% arrows Sdm completely different sail with full bottom and very even great looking leach fantastic speed and control. Great rotation both masts. I also have some ezzy masts they seem really soft on my KA,s and not as much belly. usually use hotsails hot rods the ezzy has better bottom end to get planning early but just gets overpowered early on the top end. Way better sails on the hotrods.
Yeah, prefer SDM over RDM for my old 3 cam Lofts. Deeper pocket and quicker transition to twisted top section.
But I also prefer "power" wave sails over "dtl" wave sails.
Select to expand quotejimbob SA said..
Peter. I have the same little 4-9 loft racing blade as Nina. Always ran a unifibre rdm with same results fairly flat on the bottom ( daffy always commented on this )and plenty of twist on top but still great speed and nice across the wind had spare sdm cams from my new KA used them with old 100% arrows Sdm completely different sail with full bottom and very even great looking leach fantastic speed and control. Great rotation both masts. I also have some ezzy masts they seem really soft on my KA,s and not as much belly. usually use hotsails hot rods the ezzy has better bottom end to get planning early but just gets overpowered early on the top end. Way better sails on the hotrods.
Jimbob, Nina had an opportunity to try one of our small RBs (5.0 or 5.6) with the correct SDM, and ended up buying an SDM. Just like you, she liked the sail before, but loves it even more with the SDM. When I had to replace a 430 mast for the larger sails recently, the store did not have any SDMs. I use an Ezzy 460 in my Switchblade 7.8, and always was quite happy with it, so I got an Ezzy 430. I think some of my freestyle/foil sails need an RDM, anyway. But when I rigged one of these, it seemed quite clear that the Ezzy has a softer top than the older KA RDM that it replaced (and also than the Loft RDM).
The KA RDM mast that broke worked perfectly in my KA sail, and the Racing Blades looked just like they did with the Loft RDM. They worked plenty well (especially on Lake George and other top Oz spots 
), but the sails don't look 100% right, and I think they'll work even better if the bend curve is exactly right. Not sure I'll be able to get that with the Ezzies, but I have a gut feeling that the softer top might help. If mix & match of tops and bottoms allows some fine tuning, even better.
What you say about the shape confirms what others have said. I'll check if I can find an Ezzy combo gives a fuller bottom and a leech that looks right. I got the Loft RDM for comparison. Maybe I can even use the MS hard top SDM to get a good idea what the sail should not look like .
Above my pay grade, but cam tension, batten tension, and batten stiffness thru sanding can deepen lower draft of most sails.
Personally, when dealing with finding deeper cam draft, you need to stiffen the trailing length if you sand the draft pocket area to get stability in the same winds.
After a great deal of experimenting, my experience is that sanding the batten tips thinner or to a different taper in Slalom/Race/Speed sails does NOT significantly change the position or depth of draught in the sails i have experiemented with. In my sails, the shape and position and depth of the draught is almost completely dictated by the sail shaping and the mast characteristics. Once the sail is under full tension the batten tip shape and stiffness has little, or no effect, being completely overpowered by the sail tension, mast curve and seam shape. The downside of sanding batten tips is that you make them thinner, softer and weaker which can adversly affect batten tip durability and cam rotation.
Mast specs on the other hand, can have a significant effect on the sail shape.
Your sails may be different, and you milage may vary, but dont assume you will get the effect you are after by sanding and reshaping battens tips.
There are however, noticeable gains to be had in stability, by stiffening up the back half of main lower/midde sail battens, usually by using higher carbon content, stiffer batten tubes.
Hi Peter. The TR7s set quite flat (esp smaller sizes) and have more of a progressive leech twist rather than the loose fluttery leech of some other brands with 7 battens compared to the 9 batten TR7. Don't overtighten the top battens, and make sure you pull the tack strap as tight as you can, to induce some belly into the lower part of the sail. They moved to CC masts with the TRX which was 3 years after TR7 - the hard top Maui mast you have should be perfect.
Select to expand quoteboardsurfr said..
......I agree that trying mast-sail combos on the water is what ultimately is most useful. But practically, the wind changes by several knots in most sessions. If I stop in the middle to re-rig, it's hard to tell the differences from changes in the rig and changes in the wind apart. Plus, who wants to stop in the middle of a great session to re-rig - especially in the winter when the days are short, anyway?
Yes, I agree. It is most often not at all practical, informative or desirable to change masts during a session. I have rarely done that unless there was a really obvious mis-match from a rigging experiment gone wrong. 
But a lot can be learned from a rigging session at home on a non sailing day. If I am looking for something specific in the way a sail is shaped, if it looks better on the grass, it may well work better on the water. Of course, I have had some false starts with that as well, where a sail looked very promising when rigged, but didn't perform as hoped on the water. Those are probably the best learning experiences. 
Select to expand quotejamesf said..
Hi Peter. The TR7s set quite flat (esp smaller sizes) and have more of a progressive leech twist rather than the loose fluttery leech of some other brands with 7 battens compared to the 9 batten TR7. Don't overtighten the top battens, and make sure you pull the tack strap as tight as you can, to induce some belly into the lower part of the sail. They moved to CC masts with the TRX which was 3 years after TR7 - the hard top Maui mast you have should be perfect.
The size I used was a 7.0. I had two local slalom sailors who always used MS, and their sails definitely had a very different shape with more profile. They were faster, too, but that may have been skill . One of them commented that my TR7 7.0 looked wrong, but could not come up with a way to fix it. The sail worked fine as far as I could tell, and I got decent speeds (for my not-so-high standards) with it.
It was couple of years later when a MS sponsored slalom sailor who competed in national races and worked in a store that sold Maui Sails for a while stated that MS had messed up with the TR7, and that it worked better with a soft top mast. The guys I mentioned before had mostly rigged on old Fiberspar masts, which are definitely not hard top, but worked well with MS sails from different generations. All this happened 2017 or earlier. Does not really matter much since MS is history now, except that the Loft sails I have now remind me a little bit of the TR7 when rigged on RDMs. Just a little bit, though, they look and sail better even on the RDMs I've used so far. But I recall at least one very good speed sailor (perhaps Stroppo?) commenting that our RBs had a flatter profile than most other sails when we sailed in Oz, and Boro, the guy who got us into Loft in the first place, really did not like the way they rigged on our masts.
Select to expand quoteboardsurfr said..
I use an Ezzy 460 in my Switchblade 7.8, and always was quite happy with it,
Thats interesting, as I have 5 1/2 year old Ezzy Lions (6.5/7.5/8.5) which I'm going to replace. I thought about Loft Switchblade as they would be a bit faster (probably) than the Lions, but didnt want to run to the expense of a new set of masts as well. How did the cams fit on the Loft with the Ezzy mast, did you have to do a lot of fiddling with spacers as the masts are different? Is the rotation as good?Select to expand quotechoco said..
From my understanding a sail made for CC mast rigged with a "soft top mast" the top of the leech gets very loose before correct downhaul is achieved and there's heaps more shape down low.
My experience of slightly different mast curves in sails the same as Choco's above.
So did the flatter profile low down from RDM masts balance out any extra shape low down from using a slightly more flextop Ezzy mast than the Loft mast?
In the end I decided to stick with Lions as they are easy handling and rigging and good all-round performance so have ordered another set. But its interesting reading anyway. Thanks.
So far, I have only rigged a 7.8 Switch Blade on Ezzy masts. The cams fit well, and rotation was smooth, but that's to be expected on a 3-cam freerace sail. Rigging the Racing Blades on Ezzy masts will have to wait another week or two.Select to expand quotePhilUK said..
In the end I decided to stick with Lions as they are easy handling and rigging and good all-round performance so have ordered another set. But its interesting reading anyway. Thanks.
If you liked your old Lions, that's definitely the way to go. Durability on Ezzy sails is in a very different ballpark from most other sails, especially racing sails. I managed to punch through two panels in Loft sails in unfortunate crashes so far. Overall, the build quality of the Lofts is quite decent, but monofilm will break when used as a trampoline . Ezzys are in a whole different league.
For speedsurfing, though, I'm quite happy to have a panel rip every now and then. If the crash is big enough, something's gotta break, and panels can be replaced. I vividly remember a speed crash into a different slalom sail with high-tech scrim material. The crash was bad enough that any monofilm panel would have evaporated. The scrim held, but it took me a few minutes before I was sure that it was not my neck that had broken when I face planted into the sail.
Good info. As well as the Lions, I was thinking of getting a second hand 6-6.5 race sail to use as a speed sail every now and then so if the Loft works out I might get one of those.
Select to expand quotechoco said..
From my understanding a sail made for CC mast rigged with a "soft top mast" the top of the leech gets very loose before correct downhaul is achieved and there's heaps more shape down low.
The same sail rigged on a hard top mast has the opposite effect ie takes more downhaul to get the leech to loosen and the sail is a lot flatter down low.
In saying that I've seen maui sails rigged on CC / Pryde masts and they looked quite good, so there mast be variations in how masts are built.
I did get caught on this with one of my first purchases with a Maui sail on a Neil Pryde mast. No one could work out why it looked so bad until a veteran pointed out that they were opposite ends of the mast curve spectrum. Hard top vs soft top has not shown any material performance advantage so I wish the industry would just standardise on constant curve.
Select to expand quotepaddymac said..
Hard top vs soft top has not shown any material performance advantage so I wish the industry would just standardise on constant curve.
To some extend, you've gotten your wish. Maui Sails went to constant curve in their last years, before they stopped developing new sails. Gaastra was the other big hard top brand, and they went constant curve, too. I'm not sure about the soft top guys like NP (and Hot Sails?).
Of course, there are some differences within the "constant curve" range that may still matter for race sails, plus additional differences between RDM and SDM.
