I've been fiddling with mast tuning and would like to know what settings are being used for the superwing mast in terms of

Spreader rake
Diamond tension
Prebend

Thanks

I can only give you my double-handing setting as that is the way I race most. When I race the boat solo I just use the same settings and just make the most of it, which seems to be pretty decent if I may say so myself.

I use (2-up)

50 mm spreader on 390 mm spreader arms (your Taipan arms are only 340 mm long you the reverse math equates this 50 mm to only 30 mm spreader rake

I use only 20 mm prebend I don't know what diamond tension I use, but spreader rake and prebend combined uniquely fix the diamond wires tension so I see no need to measure the diamond tension.

I went throught

First try : only 40 mm on 390 mm arms with lots of prebend (during DCC event) the boat was a dog upwind.

second try still 40 mm over 390 mm and 26 mm prebend : boat felt noticeably better

third try 50 mm over 390 and 27 m prebend : boat was a little better again, but only a little. Still my leech fell to lee too soon and hurt pointing. Boat was still flighty.

Fourth try 50 mm over 390 mm and 20 mm prebend : Boat was noticeable better at this time I was staying with the F18's on VMG. Boat still likes footing over pointing though. And it is flightly with less downhaul. Feels like I need to much downhaul.

In between I also reraked my mast forward and exchange some top battens. Exchanging the battens really helped and I raked my mast forward (when using the trapeze line measuring method) from "on the rearbeam" to 200 mm in front of the mainbeam. This raking forward really worked out well. Boat is more balances and less rooster tales at the rudders. especially singlehanding this raking forward was beneficial. I was really loading up my rudders too much.

This is how I ended last weekend. I think I can't get much smaller on my prebend (now 20 mm) as that was what the maker of my sail adviced as the minimal setting. But I do believe that I can rake my spreaders a little more aft and get the boat too accellerate more in the gusts instead of heeling. It would be really helpful if she accellerated rather than lifted as that would negate some of the work on the mainsheet that she now requires. I guess that alot of spreader rake is a good thing when you race singlehanded as that keeps you powerup in the light stuff but helps depower the rig in the strong stuff and gusts. Something I'm still lacking now or rather I handle the rough stuff with lots of sheeting action which works but is also very tiring.

So I think I will make 1-up and 2-up settings depart from one-another. I think I'll stick with 20 mm prebend but try 60 over 390 mm spreader rake for double handed sailing as here it feel like the current settings are close to what I want. For 1-up sailing I'm thinkg more along the lines of 80 over 390 mm spreader rake and detensioning the diamond to end up at 20 mm prebend again.

Conversion table for my spreader rake to that of AHPC taipan with shorter arms is

Typhoon to Taipan
53 over 390 mm = 30 over 340 mm
64 over 390 mm = 40 over 340 mm
76 over 390 mm = 50 over 340 mm
87 over 390 mm = 60 over 340 mm
99 over 390 mm = 70 over 240 mm

Summary

My redhead mainsail (2003) feels good now with 50 mm over 390 and 20 mm prebend. When singlehanding, it has good speed with these settings but I think 80 over 390 mm spreader rake and 20 mm prebend would be an improvement in 1-up sailing.

Eric, tell my about the difference between your sloop main and catrigged main. See the other thread on this forum.

WOuter

I understand that--but have you measured the diamond tension with a loos just to see where you're at?

My cat Ashby main is lighter and softer material (pentex, I think) compared to my Goodall sloop main. It has a larger fat top (not radically larger, though), mini battens between the top battens. It is very shapable and easy to manage. I'm honestly not sure about the relative fulness at the bottom--the sails don't seem that different to me in this respect; the outhaul and other controls seem to be able to make just about any shape I want. If you pressed me I'd say the Goodall sail is fuller at the top compared to the Ashby sail.

Overall I can't sense a difference in speed, but the cat main is easier to sail with due to the softer material and larger top.

Do you notice differences in pointing between the two mains ?

Also how much outhaul are you running when cat-rigged. Answer this by estimating howfar the foot of the sail is away from the boom in sideways direction at the point that is furtherst away from the boom. I think I sailed with about 2 inches of "baggyness". I hear others say that I should have significantly more than that when sailing catrigged.

For the 2-up sloop rig guys among us I can tell that 2 inches to 0 inches is what you want when sailing sloop. Past 10 knots of wind I'm sailing with almost hardly any curve in my foot and the boat seems to like that in the sloop setup.

Wouter

Spreader tuning rules of thumb :

I'm coming to the believe that the following rules of thumb apply to the tuning of the spreaders and diamond wires :

-1- Decrease prebend if you want better pointing and more power in the lighter and medium conditions

-2- Increase prebend if your sail is overpowered too soon, or when the boat still feels sluggish when the sails are clearly full with power (pulling on sheets). (here you're sails are too full and too draggy to acquire high speeds despite being filled with drive)

-3- When the boat is still flighty when the prebend is set for good pointing (and good speed in very stable windstrengths) than increase the spreader rake decreasing the diamond wire tension to maintain the same amount of prebend. This will introduce more "pumping action" in the gusts where the loading up of the diamond wires will bend the mast more in the gusts leading to a momentary flatter sail. This will translate into accelleration. You should be able to feel the difference if you have a better setting.

-4- Decrease the spreader rake if the boat is timid in all gusty conditions even when experiencing significant gusts. You have too much pumping action.

-5- Also decrease spreader rake when the tension on the diamond wires drop below a minimum value. You must never sail with diamonds that go slack during sailing (luff diamond wire). This bends the mast too far into the jib slot and closes it off hurting your pointing. Also you will ten stand up the top to much now and will make the mainsail to much bound up (limited) in spilling air in the top.

-6- Set diamond wire tension to suit the optimal spreader rake and optimal prebend for specific mainsail and your way of sailing with it. Forget about any claims that tight diamond make the top fall away better in strong winds (and the other way around) It is better to reduce mastrotation in strong winds to get the same effect. Getting prebend and spreaderrake (pumping action) just right is (in my opinion) noticeably more important than having a particular amount of diamond wire tension.

-7- If you really run into problem with diamond wire tension (minimal amount) than shorter your spreader arms so you can tighten the diamond wires again wihtout changing the optimal spreader rake or optimal prebend.

-8- If you put too much tension on your diamond wires for the given optimal spreader rake and prebend than lengthen your spreader arms and adjust the wire tension accordingly.



I believe you can trade-off downhaul tension for increased spreader rake in gusty conditions. If spreader rake isn't large enough you tend to compensate this in gusty conditions by pulling harder on the downhaul. This hurts pointing and will make you underpowered in the luffs. Increasing spreaderrake will tend introduce more pumping in the gusts allowing you to run with less downhaul tension which should improve pointing and keep you powered-up in the luff thus improveing speed as well.

Prebend, I'm finding, is relatively strongly related to used mainsheet tension which in turn is strongly dependent on the crew weight on board. Less weight means less sheet tension to fly a hull and thus you'll need more prebend to make the mainsail have the correct twist profile and draft with the lower sheet load. If you are running heavy and are increasing sheet tension to bring in the squaretop to keep yourself out on the wires than having too little prebend will flatted out the middle part of the sail too soon. Increase prebend then to off-set this.

In principle your should find the optimal prebend for a given set of mainsheet tension and downhaul tension that your mainsail likes. Mainsheet tends to bend the mast all over its length more than downhaul tension does. Downhaul tension tends to flatten the top more than the middle part of the mast. So you'll first have to find the optimal ratio between mainsheet tension and downhaul and find the best prebend to that. As everything is linked to eachother you can't get this right in one try but you'll have to experiment with a few prebend settings and choose the best one and test some more around that "best point".


Wouter

Outhaul settings:

Cat rigged, 20mm upwind in heavy air; a bit more (20-50mm) if lighter wind. Downwind, 100-250mm, depending on apparent wind speed. I sometimes sail cat rigged sans spinnaker, and then I usually have the outhaul very loose downwind, 200-250mm.

Sloop rigged, 10-15mm upwind; 100-150mm downwind (depending on apparent wind).

I have now stopped tightening the outhaul taught to 0mm, even in heavy winds because it ends up pulling the bolt rope out of the bottom of the mast. Leaving the outhaul just a bit off the boom prevents this, and I still flatten the sail fine up high.

FWIT, my sails/mast allow 4.5 Ronstan numbers worth of downhaul.

This past weekend we were sailing in conditions where you had to keep the top half of the sail flat and nearly backwinding to prevent capsize. I had my mast settings more extreme (more prebend and tighter diamonds) than I ever had at:
Spreader rake 50mm
Prebend 48mm
Diamond tension 38 Loos

Previously my prebend was 30mm with looser diamonds (33). I was trying to keep the gusts from deepening the sail more. Although it was hard to pay much attention to the nuances since we were just trying not to wash off the boat in the waves, speed seemed okay because, for comparison, an A-cat (Bimare XJ) could just barely pass me upwind. But had the winds been lighter, this would have been too much prebend.

Here are the setting Ashby suggested for my rig and sail:
Spreader rake 55mm
Prebend 30mm
Loos 39 (ends up 33 for me to attain the other 2 numbers)

I think Goodall suggests:
Spreader rake 40-65mm
Diamond tension 42 Loos

McCook suggests:
Prebend 35-38mm


Here's what I'm trying now (0-10kts/10-15kts/15-20kts):
Spreader rake 45/55/60mm (for your longer arms, 70/80/87)
Prebend 20/30/35-40mm

(I'm mostly sailing uni but try to keep mast the same for sloop)

As you suggested, the diamond tension is to be taken with a grain of salt since Loos gauges seem to differ.

If I want to, I can pull 8 numbers on my downhaul = 8 inches = 203 mm I could pull more if my boom wasn't in the way. The 1:12 cascades system is a dream. with one hand I can pull it down all the way to the boom; Only the last 20 mm I have to pull hard the rest is downhauled easily with one hand. A while back somebody asked me what to get for the downhaul 1:8 or 1:12; and for sloop sailing the choose is not that clear but for solo sailing I would definately opt for 1;12. But only when using a 2-STAGED CASCADED downhaul system. Non-cascaded or single cascaded 1:12 systems just have too much friction in them to make them work better than 1:8 systems.

When I pull everything on really tight (mainsheet and maximum downhaul = 200 mm) than my sail is really flat all over. But I shouldn't have put my boom any higher than it is now as I'm always quickly approaching the boom with the foot of my sail. I have fully done away with the bottom flap that curls up. There is simply no advantage to it. In the really light stuff there is hardly any wind that low above the watersurface to justify having any area there. And at about 8 knots my straight foot is only about 30 mm of the boom anyway. At 15 to 20 it is as good as right on the boom. What use is there to close of this 30 mm ? It is better to have the area in the flap put in the head of the sail.


Phill Brander is telling me to sail with less tight outhaul to improve speed upwind and get a little better pointing. I was using about 25 mm upwind in cat rigged mode (1-up) as you but he says that he uses 3 to 4 inches upwind (when using a mainsail cut for sloop sailing). He uses this with good succes. He mentions that the groove is a little narrow and you really have to look for it. He also mentions that pointing on a Taipan comes mainly from having good boat speed.

Main idea behind these settings is that you are trying to make the lower part of the sloop cut mainsail fuller by letting out more outhaul. On a specialized cat rigged mainsail this is not necessary of course as the required extra draft is already cut into the panels and luff curve.

Personally I never adjust my outhaul from its upwind value. I just pull a kite and head downwind with the same setting. Sometimes I may slacken my downhaul just a little but even that is only done when I have time or when the winds are lightish. Only things I do adjust when going from upwind to downwind is the mast rotation to make my top stand up against the pull of the spinnaker and I run my main traveler a little bit further out. I feel that adjusting the other stuff just takes too much time when going around A-mark for hardly any noticeably gains, but also that finding the correct settings again on the next upwind leg after round C-mark negates any gains ever made by modifying the trim in the first place. I feel that a proper upwind trim for the given conditions is already a very good "ball park" setting for downwind spi sailing in the same conditions. Quick hoists and being on your way soon can easily account for several to many boatlengths of gains. Much more then any gains made through optimized boatspeed through adjusted trim.



It is good to hear that you are using lower diamond wire tensions as well. I found the tight wires set-up (?42 loose gauge?) impossible to maintain. I couldn't get the boat to work like that. But then again I often sail at 145 kg overall crew weight so I want a big of power up high and so I want the top to stand up. Also my larger squaretop mainsail seems quick to spill air. So I'm not at all looking to have my top fall away by having tight wires.

Only real concern I have with loose diamonds is the closing of the jib slot in gusts. However scientically speaking their is no such difference between tight wires and tensioned wires as long as neither wire goes slack during sailing.

Also longer spreader arms (which I have) actually make the middle section of the mast bend less into the jib slot for a given wire tension then shorter arms. So I think I'm already well covered in the jib slot area.

Wouter

Eric,
Here are some articles on tuning the 4.9 and of sailing with the superwing mast, courtesy of the Taipan Sailing Assoc (Aus). Hope these can help in some way.
http://www.taipan.asn.au/Tips%20and%20Tricks/archived_tips_frame.htm

Yes, thanks, was aware, years old.

Looking for new data if anyone's trying new settings, especially cat rigged settings (most mast tips/tuning are sloop rig).

Eric

I have not sailed with the Superwing mast but I have sailed with numerous other masts and was involved in a Tornado mast project with the British Olympic team and the Royal Aeronautical Society in the mid 90's, this mast was similar to the 'wing'. We found a few fundamental things.

1st individual aluminium masts vary hugely in stiffness,

2nd mast rotation had a much greater effect on speed than spreader rake or prebend.

3rd pretty much the same rules applied to all the masts we used.

4th the downhaul is a much more powerfull method of adjusting mast bend (and can be tuned to specific conditions) easily and effectively.

5th the only time that diamond tension made a significant difference to speed was when the windward diamond went slack.

We found that most of the top Tornado sailors were using very different spreader rakes and diamond tension, but were all going along at virtually the same speed.

My advice to you would be to put you spreader rake in the middle of the settings reccomended by the good sailors (Greeg Goodall says 40-65mm I believe.

Then I would set my diamond tension so that when trapezing and with max downhaul the windward wire is just tight, this will make the maximum power for your sail available to you.
I would then forget about spreader rake and diamond tension except for very heavy winds.

I would set mast rotation so that it is at max power (for us it is pointing at the shroud, the tips page on the AHPC site says 50 to 60 degrees, this becomes the base setting and is used in all conditions apart from heavy winds and very light >5 knots windspeed.

Having achieved a max power setting which is used in all wind strengths up to trapezing with full downhaul on, the next step is how to set about de-powering as the wind increases.

During a race this is done by first pulling the rotator towards the middle, (up to 20 degrees off centre), then letting out the traveller (as far as necessary). The guide for how much to de-power is this.

At all times you need to be able to pull on full mainsheet tension without the boat falling over or stuffing into wind and going really slowly. [color:"red"] [/color]

I have highlighted this because it is very important.

If (and sailing in the Bay area this must happen a lot to you), the wind is very strong from the word go, I would let off 2 turns of the diamond tension so that the windward wire goes slack (wires must be heavily taped in or wired in to spreaders if they come adrift the mast will break when you tack). still use max downhaul on this setting but have the rotation in the max power setting(50-60 degrees).

You will find that the sail becomes incredibly de-powered and calms the boat down, it is also very low drag and very fast.

This setting is only for strong winds. and is a 'super depower' setting as fast as it is in heavy winds it is dog slow in medium or light or even quite strong winds.

In very light winds (less than 5 knots) I would set the mast rotation to 80 degrees

give it a try and let me know what you think.

john

John, thank you for a good post with lots of specific information.



Could you specify how you decide on what's "tight" enough in the above point? Just a visual check while sailing, or something that can be measured?
To find your setting, do you experiment while sailing, or do you set it up on the beach (without wind filling the sail). I asumed that you did this while sailing, but it would be good to know.


It was fun reading about your T experiences. That masts differ in stiffness was not new information. But that you brits was working on a new T mast in the 90's was news to me. One of the reasons for the T carbon mast (flogging a dead horse here) introduction was that you brits was working on yet another alu T mast? Do you know anything about that?

Rolf

Visual check on the windward wire tension is fine, it must be done whilst sailing obviously, and needs to be fine tuned on the water, once the setting is known you can measure with a tension guage so that when you replace the wires it is easier to set.

I know you are all aware that masts differ in wall thickness (usual tolerance is 5%) and stiffness, but when looking to tune your mast just taking the numbers from one mast will not reproduce the same characteristics on another one if it is not the same.

The later talk about a new mast was after my time.

john

Thank's John.

I just popped in and saw this post by John. Please allow me to add the little tid bits that I'm aware of. I'm certainly not of the same skill level as John, I will say that upfront. Still, I may have some info that we all can use.





I really doubt it. Forgive me.





While true, both of these points do not help us. That the mast rotation has a far greater effect on speed than spreader rake of prebend doesn't mean that the effects of these last two things on speed is negligible.

That the same broad rules apply to all masts doesn't help us get that final 5 % of speed out our superwing rigs. For that you'll need specific info on how to optimize your mast and sail combo.

I write "mast and sail combo" here because that is were the final few % is a dependence on both. I can use the Goodall mast settings for my Redhead mainsail and complete turn it off. This when the right (redhead) settings can turn my (Redhead) motor on. This is my actual experience and I'm moving away from the Goodall/Ashby settings as a result.





That is not entirely my experience. While true in (again) broad terms I personally found that having to pull too much downhaul (or too little) to correct for the wrong spreader rake and prebend settings was hurting my performance. You can indeed adjust your rig by pulling on the downhaul, even to a large extend, but there is no compensation for a wrong spreader/prebend settings. Especially not when your prebend is too much. How do you pull less on the downhaul then not at all ?




Or when the diamonds are so tight that your prebend is way too much for the luff curve of your sail. Something that can easily happen with the superwing mast section as you sail with significantly less mast rotation then on other boats. Going to 80 degrees mast rotation angle to compensate for too much prebend is really not an option on the superwing masts as that will flatten your top too much. As the superwing is so flexible in the sideways direction you can NOT overrotate without sorting any negative effects in the top. What happens is this :

Say you have too much prebend for the given luff curve in your mainsail and your downhaul is already slack. Your top is however fine as that is not affected by the prebend setting. You feel that you are lacking power and pointing and in relation to a boat with perfect settings you are indeed lacking these. Now you try to increase your mast rotation to present the luff curve of your sail with the straight side of the mast (due to diamond wires that keep your mast straight in this plane). Now your lower section of your mainsail and the very important middle section will stand up and get more draft. However by overrotating the mast you present the more flexible side of the mast above the hound to the mainsheet tension running up the leech. Your top parts bends more and takes up the luff curve cut in the top section of your mainsail. Effect. You flatten out the top part and let the leech fall away there. Your pointing will increase somewhat, but less so than you would expect after optimizing your middle and lower parts. In addition, the other boats will double trapeze upwind while you are barely single trapezing. Your are now lacking power in the top to lift that luff hull and get that final bit of pointing and speed. You'll do better than before but still are uncompetitive in relation to an optimally tuned boat.

Again, I think John is right in the broad sense but for the final bit of performance gain the basic setting of spreader rake and prebend can be important.

I learned all this from my own experience. All things discussed above happened to me on my own boat. I was sailing with too much prebend in 2004 (result of having too much diamond wire tension) and could not outpoint a Hobie 16 if my life depended on it. I went through 4 different rake/tension settings since then and each time I got a performance improvement.





You will see the same thing in the Taipan and F16 classes. This is not because all masts vary heavily in stiffness or whatever, but more because different sailmakers make different mainsail designs. Each sailmaker will therefor produce a sail that prefers a different setup of spreader rake and diamond wire tension (among other things).

Why is this ?

Well because the basic setting is dependent on the assumed average downhaul tension and average mast rotation. Goodall and Ashby both design THE TOPS of their sails to set right with light to medium downhaul tension and a given rotation. The luff curve of the top of their mainsail is cut to suit these settings. There is not much you can do with the top of your mainsail, you lack the controls. So you adjust your spreader rake and prebend to get the middle (and also a little bit the lower) part of your mainsail to set right with these given downhaul tensions and mast rotation.

My own Redhead mainsail likes alot more downhaul then those of Goodall and Ashby. I compared setups with Taipans and I'm running alot less prebend now (4th experiment with rake/prebend settings). Reason, redhead has cut the luff curve in the top of my mainsail rather round. So the top is rather full when presented with a normal mast rotation setting. Also my top is quick to hook to windward, which is very draggy. To compensate I have too options; increase mast rotation or crank on the downhaul a little more. The first presents the more bendier side to the sail and makes the top bend more under leech tension. The second bends the top more for the given mast rotation. I choose downhaul as too much rotation is slow on the taipans and because I was running so little downhaul that I had creases in my mainsail along the mast. However this is not the end of it. By pulling harder on the downhaul I also bend my mast more at the spreaders. To SOME extend the bending due to downhaul and prebend can be added to oneanother; it is actually a bit more complex but this is accurate enough for now. So I need to run less prebend to get back at the optimal mast curve for the given luff curve cut in the middle of of mainsail. And this is exactly what I running now. I only run 25 mm prebend while Ashby and Goodall advice 40 mm to 50 mm.

So this large difference between my setup and that of others can largely be attributed by the different way Redhead and Goodall/Ashby cut the luff curve in the tops of their sails.





My advice here is to just e-mail Glenn Ahsby (We're talking about your ashby sail here, right Eric ?) and ask him for which rake and prebend the luff curve was cut. Start there and then do some personal fine tuning for your local dominant conditions.

I did that with Redhead and found out that he cut my mainsail for a 20-30 mm prebend and a 20-30 mm spreader rake. As you can tell this is noticeably different from the Goodall (Taipan ) settings. When using the Goodall settings I was noticeably lacking height and speed.




If your luff curve is pronounced in the middle then this advice my lead to sailing with to little prebend and thus a middle part of the sail that has too much draft and a tight leech. This is often less damaging then too little draft and a loose leech but it is still sub optimal. You will often have good pointing but you also max out on boatspeed a bit earlier than others.





Finding the right prebend (average) for both medium and light winds was a bit performance boost for me personally. Johns methode will get you in the ball park for sure but for the final few % performance you will need to look for the optimal setting between the given luff curve of your mainsail and your mast. It can be that more prebend than what you find with John method is better.





The approach that is working for me is finding the mast rotation angle that properly sets the top of my mainsail for the average mainsheet and downhaul tensions. These three things are heavily interacting with eachother on the superwing mast. Much more than I found on saw Hobie Tigers etc. Especially when you are sailing with an entlarge squaretop. I'm finding that a smooth transition between mast and sail (on the lee side) is of no particular concern on the superwing masts. Or at least at times I found better speed when I derotated the mast past this aerodynamic point.




The super depower setting make sense to me, although I have not sailed with such a setting. But the slack windward wires would lower the stiffness of the mast in the sideways direction which will allow the mast to bend more in the middle thus flattening out the middle of the sail and letting the middle leech fall away. The top is then still presented with the more flexible side of the mast and is alo bending alot make the top flat and letting the leech fall away. All in all you would be sailing with rather flat sail (small draft) and a open leech. Both will spill power while you can maintain a stiff mainsheet which keeps you forestay taught = flat jib and maintains acceptable pointing.

Didn't Landenberger advice a similar adjustment for the really strong winds ?

Wouter

This is exactly the reason why I'm following the top-down approach now.

First find the optimal mast rotation setting that sets the top of your mainsail right for nominal downhaul and mainsheet tension. = TOP

Then fine-tune the prebend to have the middle part of the sail sit right with these downhaul and mainsheet tensions and the newly found optimal mast rotation. = DOWN

Then adjust spreader rake while keeping the prebend the same to find the best reponse to gusts. This is really the last fine-tuning you do.

Of course as everything is interacting with eachother this is rather hard to get right in one try. It is better to be prepared to hone in on the optimal settings in about 4 iterations. Or by starting at the adviced settings of the sailmaker that actually made your mainsail.

Regards,

Wouter

Firstly I am not going to argue about what I did or didn't do 10 years ago with someone who wasn't even there.

secondly I can tell you that you will not 'fine tune' 5% more speed out of a rig by altering diamond/spreader settings from those I have given or those your sailmaker will give you. 5% is the kind of difference made by whether or not you put your jib up, you will do well to find 1/4 % with fine tuning spreaders.

My advice is my honest opinion based on thousands of hours of two boat tuning with the best sailors in the World and hours of dinghy park chit chat with them.

Eric give what I say a try, if it doesn't work it won't cost you anything.

Post deleted by Wouter

Why this fascination with the superwing being somehow different to tune? It's not some kind of esoteric beast.. there are thousands of them out there.

The principles of tuning any mast hold true for the superwing, in fact it seems little different to the old IYE and, more particularly, Holt Allen Shearwater masts we used back in the early 70's.

The purpose of spreaders are two-fold. To support the mast laterally and to force pre-bend in fore and aft through rake. The further back you rake the spreaders, the less diamond tension required for a particular bend. Balance this against a slight loss in lateral support.

Little rake and loads of tension means that your mast is heavily loaded already and therefore downhaul will have greater effect in the top of the mast. More spreader rake and less tension for a given bend allows the downhaul to affect the whole mast more evenly. Banging on loads of diamond tension is an age old way of dealing with a real blow (but it limits your on the water options).

I too spent thousands of hours doing two and three boat tuning, comparing rake, pre-bend, sail draft, downhaul settings etc. I can echo what John P has said. The boats (Tornados) were not greatly different from each other except when we started to play with rotation (once pre-bend matched luff curve). This was where we could have the greatest influence on power and pointing.

In your position Eric, I'd follow John's advice. Then, bearing in mind the principles I've outlined above, use your own experience and intuition to fine tune to your boat and your sailing style. Never stray however from the unloaded pre-bend (however achieved) matching your mainsail luff-curve

Happy sailing and testing!

Well john,

Can you say that you have ever seen the superwing mast, let alone sailed with one ?

(There is one right back at you, so I guess we are both guilty here)

I'm not critizing against the approach you've written down. It will work, and get you close to optimal even, I even wrote that down. I just wanted to caution agains the believe that spreader rake and prebend isn't important. Get these wrong to a signifcant level (for mainsail with a given luff curve) and it will result in noticeable damage to performance. I found this to be the case on both my Taipan F16 with the superwing mast as my Prindle 18 with a normal teardrop shape mast. And in no unmistakeable terms.

I guess I have just as much right in presenting my comments as you. Considering I can trade off your thousant hour experience on other masts with actual experience tuning my own superwing mast.

For clearity; most damaging is to sail with too much prebend. You can often get away with too little prebend and pull on the downhaul harder even if it is still not optimal. Your approach will lead to the last case and thus get a pretty good basic setting.

Regards,

Wouter