Would using shorter mast in a freestyle or wave sail help improve the sail's bottom end and help pumping & planing? I have a 5.4 NP Wizard that normally rigs on a 430 mast, and similarly Goya Banzai's in 5.0 that rigs on a 400.
For foiling I rig with less than recommended downhaul and more fullness in the sail.
Would the bottom end improve by using a 30 cm shorter mast and longer extension, i.e would it give a fuller profile with less wind pressure?

That's a good question and one that I have pondering myself. I think the less extension the stiffer the overall situation, but I would be interested to hear the groups thoughts.

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utcminusfour said..
That's a good question and one that I have pondering myself. I think the less extension the stiffer the overall situation, but I would be interested to hear the groups thoughts.

Agree, less extension is stiffer and hence tighter leach and more power

No doubt less extension is stiffer BUT the sail needs shape to work efficiently
My feeling is shorter mast with longer extension will give a better shape when pumped in light conditions, of course sail still needs to be rigged with a tight leech

My hypothesis: Since a shorter mast bends more easily, the energy of the pump is absorbed by the mast rather than driving the sail through the air. As well, it allows the leach to open more easily as mentioned above by several releasing pressure from the sail. (Remember that one of the advantages of a softer leach is the ability to act as a valve in overpowering conditions)
This is similar to cycling where a stiffer frame is generally preferred as leg power is transferred to the wheels rather than bending the frame.

I have been discussing the idea with many people, and I beleive there's no short answer to this question. From a buddy that has been competiting at national level, using both mast extenders at bottom and top of mast has been effective for him as he is a very light guy (sub 70kg).
Concerning wave sails, the shape is induced by design from the shape of the panels, the battens, luff curve, and fabric layout. I believe that brand make a design for an average rider, probably around 85kg. So the adjustement you can make on your sail profile are :
Luff tension. When bending more the mast, it tends to match the luff curvature thus flatening the sail. Of course you have to adjust your boom length accordingly.
Boom tension also has some effect, and some sail are even designed to be trimmed this way.
Battens can be adjusted, first by triming tension, but some riders even trim their profil to adjust the position of the curve. And then there's the mast rigidity, which affects the way the sail takes its shape under pressure and opens up in the gust. When you have a wave sail rigged up, it is rather flat without pressure. To visualyze how your sail will takes its shape and open up on top, you need to curve the mast sideway.
So usually shorter mast are less rigid (IMCS goes down with length). That's true up to a point : depending on brand, mast shorter than 310 don't have lower IMCS. That's to compensate for smaller sail lower pressure.
Also, kids mast have lower IMCS, and that's another solution for light weight riders (often used by women).
If using a shorter mast than recommended, along with a longer extention, you also have to consider other side effects : the curvature of the mast is set higher, thus this tends to give a hard top effect. And the boom will be set lower regarding to the renforced mast section. You can compensate by using top mast extention, but this king have to be DIY. You can also mix top and lower section of mast (it is even standard methods for Ezzy)

Now why do you need a softer mast ?
I tend to favor these for top end, gusty wind with small sails (sub 3.5m) really require the pressure release valve of the sail twist to trigger at once espacially if you're not a top rider.
As for lower end, it's another issue. From my personal experience, I feel that mast responsiveness and weigth is more effective on pumping efficiency. So in short more carbon is better. Note though that I always keep some loose leech : I really don't like my sails with tight leech, but I suspect that really depends on your sail type.

I'd suggest you made your own experimentation, one setting at a time, after having thinking out how and why you want to affect your sail shape.

So opinions are divided. The leach will of course be tighter but it was more the advantage of more shapewith less wind I was thinking about. My non-cambered sails obviously do have a much flatter profile with the battens coming in front of the mast unless filled by enough wind.

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TomDW said..
non-cambered sails obviously do have a much flatter profile with the battens coming in front of the mast unless filled by enough wind.

Well, that's exactly why I think softer mast is an interesting way to use a wave sail for foiling. Plus having discussed the idea with proficient riders, it seems that for the same reason lighter riders gain with softer mast even for fin sailing. But there are other curvature concerns (thus top mast extension rather or along longer bottom mast extension).
But back to foiling, I've been making many trials since I took foiling back in 2018. And though we now have dedicated foiling sail for slalom and racing, there is no consensus regarding small wave sail usage.
I've tried out the tight leech concept as it was commonly thought as the way to go. I've even tried out a 2 batten sail : S2maui Dualist. It is a down the line wave riding sails tight leech design, intended to provide instant power for take of and easy to neutralize in side off. My idea was that it would provide the required 'grunt' to pump up, and then be very light once flying. And it is indeed exactly what I got, but the wind range feels so narrow it is very uncomfortable at my gusty home spot. I tried it out with shorter/softer mast (340 instead of the recommended 370) along with some very long (48cm) bottom mast extension, but the result felt miserable. I've not tried a top mast extension yet though, nor tried out to mix top and bottom mast section.
Now my favorite sail for foiling is an old days Naish Chopper 'M' size I rig on a 340 (with base extension) instead of a 370 as recommended. I've even tried it out on a 310, but the curvature of the mast is too offset upward then.
I don't think there's a universal answer to your question regarding smaller/softer mast being simply better. But sure it does have a real and effective action on your sail behavior. Just be aware that a shorter mast not only change IMCS, it also shift upward the curvature if you're only using a longer base extension. Also, from what I experienced (and I insist on the fact that it is only limited experience), the effect is more noticeable on top end rather than on low end.

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6u1d0 said..

TomDW said..
non-cambered sails obviously do have a much flatter profile with the battens coming in front of the mast unless filled by enough wind.

Well, that's exactly why I think softer mast is an interesting way to use a wave sail for foiling. Plus having discussed the idea with proficient riders, it seems that for the same reason lighter riders gain with softer mast even for fin sailing. But there are other curvature concerns (thus top mast extension rather or along longer bottom mast extension).
But back to foiling, I've been making many trials since I took foiling back in 2018. And though we now have dedicated foiling sail for slalom and racing, there is no consensus regarding small wave sail usage.
I've tried out the tight leech concept as it was commonly thought as the way to go. I've even tried out a 2 batten sail : S2maui Dualist. It is a down the line wave riding sails tight leech design, intended to provide instant power for take of and easy to neutralize in side off. My idea was that it would provide the required 'grunt' to pump up, and then be very light once flying. And it is indeed exactly what I got, but the wind range feels so narrow it is very uncomfortable at my gusty home spot. I tried it out with shorter/softer mast (340 instead of the recommended 370) along with some very long (48cm) bottom mast extension, but the result felt miserable. I've not tried a top mast extension yet though, nor tried out to mix top and bottom mast section.
Now my favorite sail for foiling is an old days Naish Chopper 'M' size I rig on a 340 (with base extension) instead of a 370 as recommended. I've even tried it out on a 310, but the curvature of the mast is too offset upward then.
I don't think there's a universal answer to your question regarding smaller/softer mast being simply better. But sure it does have a real and effective action on your sail behavior. Just be aware that a shorter mast not only change IMCS, it also shift upward the curvature if you're only using a longer base extension. Also, from what I experienced (and I insist on the fact that it is only limited experience), the effect is more noticeable on top end rather than on low end.

Nice write up. Some things that come to mind:
whether a smaller mast acts more or less hard top would depend on the relative flex of the extension. For example, my rdm extensions are HD thick aluminum built for the rigors of wave sailing. I'd expect that it's stiffer than the carbon it's replacing. As well, the smaller mast is usually a step down on the imcs (and, iirc) even more on the mcs spectrum as imcs numbers are normalized to make comparing masts of different lengths easier.
Also, we smaller folk like shorter, softer masts precisely because most sails are designed for heavier riders. In stronger winds, it's more difficult for the sail to bend off as intended because we can't hold down the necessary power to do so, so we'll sheet out instead. This is usually more effective when a mast is at the edge of whether on or another length could be used such when the recommended setting uses very little extension. Using it on a sail that requires, say, 30 cm of extension will end up too soft even for my 62 kg.

I'm not sure an extension is stiffer than the mast. Remember we're comparing the bottom of the mast not the top flexy part. If you were to have a mast made from the bottom part of the mast all the way , and compare it to an extension as long as the mast complete with holes , the extension would be much weaker and flexier. Add to that fact, any sloppiness will produce a kink in the mast to extension join. Even a one mm size difference between the top of the mast extension and the inside of the mast will produce more mast curve than what the bottom of the mast or extension could ever bend. Especially when using more extension thus having a smaller point to point creating a much bigger kink. So I believe , using a longer extension is producing more mast curve on those points alone.

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Imax1 said..
I'm not sure an extension is stiffer than the mast. Remember we're comparing the bottom of the mast not the top flexy part. If you were to have a mast made from the bottom part of the mast all the way , and compare it to an extension as long as the mast complete with holes , the extension would be much weaker and flexier. Add to that fact, any sloppiness will produce a kink in the mast to extension join. Even a one mm size difference between the top of the mast extension and the inside of the mast will produce more mast curve than what the bottom of the mast or extension could ever bend. Especially when using more extension thus having a smaller point to point creating a much bigger kink. So I believe , using a longer extension is producing more mast curve on those points alone.

Good points. Something to consider is that most of the load at the end (ie where the extension is) is in compression rather than bending. The bend in the middle of the mast occurs for that reason even if the section is similar to bottom. Also consider that the 1mm kink is only affecting the foot and not the head where the leach is. Last, my comments are significantly influenced by the HD RDM extension I've been using the last couple of weeks which has a very thick wall (much more than, say, Chinook).

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Also, we smaller folk like shorter, softer masts precisely because most sails are designed for heavier riders. In stronger winds, it's more difficult for the sail to bend off as intended because we can't hold down the necessary power to do so.

This has been my experience as well. At 140lbs, I prefer a softer mast. I like just enough downhaul to create a deep knuckle in the luff, but still have the battens (non cambered wave sail) rotate easily. My lower batten leading edge had a 50-100% overlap of the mast when unloaded.

I recently got a North 4.2 wave sail that I struggled get tuned with a nolimitz sumo mast. It has more luff curve than my goya sails and had to downhaul the hell out of it to get it to rotate, and that made the leach too open at the top. I got a goya 70 mast and now its works great.

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WsurfAustin said..

Also, we smaller folk like shorter, softer masts precisely because most sails are designed for heavier riders. In stronger winds, it's more difficult for the sail to bend off as intended because we can't hold down the necessary power to do so.

This has been my experience as well. At 140lbs, I prefer a softer mast. I like just enough downhaul to create a deep knuckle in the luff, but still have the battens (non cambered wave sail) rotate easily. My lower batten leading edge had a 50-100% overlap of the mast when unloaded.

I recently got a North 4.2 wave sail that I struggled get tuned with a nolimitz sumo mast. It has more luff curve than my goya sails and had to downhaul the hell out of it to get it to rotate, and that made the leach too open at the top. I got a goya 70 mast and now its works great.

Good to hear you got it sorted Matt. How are you enjoying the North 4.2?

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John340 said..

WsurfAustin said..

Also, we smaller folk like shorter, softer masts precisely because most sails are designed for heavier riders. In stronger winds, it's more difficult for the sail to bend off as intended because we can't hold down the necessary power to do so.

This has been my experience as well. At 140lbs, I prefer a softer mast. I like just enough downhaul to create a deep knuckle in the luff, but still have the battens (non cambered wave sail) rotate easily. My lower batten leading edge had a 50-100% overlap of the mast when unloaded.

I recently got a North 4.2 wave sail that I struggled get tuned with a nolimitz sumo mast. It has more luff curve than my goya sails and had to downhaul the hell out of it to get it to rotate, and that made the leach too open at the top. I got a goya 70 mast and now its works great.

Good to hear you got it sorted Matt. How are you enjoying the North 4.2?

Hey John,
Now that I've got it sorted with the new mast, its working well. Obervations relative to my goya fringes...

Shorter clue/boom length relative to the size.
Requires a little more rear weight bias under acceleration or pumping to launch. Less rear hand pressure when pushing hard up wind (no surprise). Might not be able to sail as high and angle going up wind. Need more time to quantify. I've only had one session in lightish gusty conditions, but just a "feeling" at this point. Had a fun session dropping a 30' trimeran.



Response to puffs is immediate. Not good or bad, just different.

Light weight is amazimg. It feels lighter than my 3.0. Haven't looked at the actual numbers.

Durability.. Time will tell.. My brother was a sail designer for North decades ago. He races in many classes (Gold medal in the Pan American games, world title in several dingy classes etc). The local J80 fleet uses the same 3DI formed sails for their jib, and my brother claims they are still competitive after 3 years of racing, where as their standard sails are "blown out" after 2 seasons.

Coming back on a related answer by someone in another thread, to extend the mast extansion in low wind to bring the COE of the sail higher up (suggested to also improve early planing on a waveboard apparently).

I tried it yesterday when the wind dropped and my 5.0 Banzai did not lift me on the foil anymore. I added 8cm to the extension and the difference was massive. Somehow got some leverage that I could pull against, if that describes it. So much so that I will try it on my waveboard next, even in powered up conditions. Note I am 193 tall and have always felt a bit too tall compared to the COE of modern 4-batten wavesails (I put my boom at shoulder height which is almost as high as it can go in the cutout, now I can lower the boom correspondingly).

great to challenge preconceived ideas after 40 years of windsurfing, that it is not about rigging the sail as close to the base as possible.

Shorter mast (eg 400 vs 430) will just impact the bend curve. Very likely your shorter mast will ended up feeling like it has a "softer top" and hence letting out more power as you pump. Smaller sails (4.7 and smaller are probably a bit more forgiving).

I had this discussion with Severne a few years back. I asked him if it would be possible to make a 5.7 Blade that works on a 400 mast. His answer was to the effect off the shape not working because the top is too soft. His explanation was a bit more detailed but that was the take away for me.

I am qurious for the discussion about a blade 5.7 with 430 red rdm and 400 rdm mast. Ik use this blade for mij fsw with both masts an notice no difference on the beach and on the water.

I dont know how to put the pictures here from the sail rigged with the 2 masts

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stehsegler said..
Shorter mast (eg 400 vs 430) will just impact the bend curve. Very likely your shorter mast will ended up feeling like it has a "softer top" and hence letting out more power as you pump. Smaller sails (4.7 and smaller are probably a bit more forgiving).

I had this discussion with Severne a few years back. I asked him if it would be possible to make a 5.7 Blade that works on a 400 mast. His answer was to the effect off the shape not working because the top is too soft. His explanation was a bit more detailed but that was the take away for me.

Jawohl Stehsegler, I tried rigging my 5.0 Banzai on my 370 mast that I use in 4.7 and the bend curve looked 'funny': more curve towards the top of the sail and straighter above the boom, which seems conistent with remarks made here about altered bend curve. I discarded the idea and will keep using the 400 100cc.

however I was thrilled about lengthening the mast extension with my body length and will play more with that, also for regular wavesailing.