i was just advised by our local sailboat repair shop (he crewed for me last sund) that i have to much pre-bend and my mast is bending way to much in light air.

My diamonds are set to 420lbs, (by chance, but also close to what i was advised) and there is a fair amount of pre-bend on my spreaders.

My question is since i sail solo 90% of the time (and dont race much), and i fly a spin.. do i really want to stiffen up my mast... and power up my cat?

Do i risk (breaking) the mast more (with spin out and less pre-bend)?

Thanks.

Here are some pics, not sure they will tell you anything... but they were taken at anchor, with downhaul on, outhaul on, and rotator turned as much as i could (with my foot)... but there isn't allot of bend noticeable..

What does the sail maker recommend?

i hadn't thought about contacting the manufacturer, but this is for a used, modified, tornado sail for a mystere rig. i would wait to bring it to a local sail-maker and have him charge me to mend the sail at this time. But good idea, and i will keep it in the back of my mind if i need to keep searching. Thanks

I am very (more) interested in hearing the opinions of the very knowledgeable people on the forum about the theory of the pre-bend/spin relation, in safekeeping my mast in 1 piece.

Andrew:

Are your battens tight? You have a lot of wrinkles in your sail. As for spin, one thing I learn while out learning spin is you must be traveled in and sheeted to telltales. Main works like a backstay to protect the mast from breakage,



Doug

how much downhaul on? doesnt look like you have much... the top third (or so) should be flatter and more mast bend if you are hard on the downhaul...but i prolly don't qualify as one of the smarter dudes around. Hard to say though since you aren't necessarily in saling conditions there.

the battens are a little lose because as it is... i have troubles getting the sail to switch over (curve to the correct side) and tighter batten tension makes it even harder. I am switching to a stiffer fiberglass batten as soon as i have the time to swap it over,

Hi Andrew, here's my take on your question of the mast breaking. My opinion is that your mainsheet tension while having the spin up will have more effect on supporting your mast than your diamond wire and spreader angles. Sp by straightening your mast, but making sure that your main sheet tension is on with the spin up, your mast should be supported no problem.

I take it you are trying to power up your rig? One thing i do note though is that i think your battens 3,4,and 5 counting from the bottom needs to be flatter/stiffer. The draft in that section looks a little too far forward as well. This may not power up your rig, but it will make your boat sail more in line with the concept of a pre bent rig. I used to have a A class with a set of sails where the battens was too soft for the sail and every time i cranked on the downhaul, it made the top of the sail fuller rather than flatter and powered up the boat rather than depowering it.

Hope this helps

well since i have to much bending going on... i know if i stiffen my mast, and reduce pre-bend...i will have more power.

But its a question of:
do i need more power? - prob not
do i risk my mast (at all) by adding this power (since i sail solo) - don't think so but looking for others input

Battens ... yes i know they need a little tightening.. but this makes getting the sail (in light air) almost impossible to switch over and curve to the correct side.. so i have them a little on the lose side..

Andrew:

I sailed solo most of the time on the Mystere 4.3 I bought to learn spin on. Once I learned to travel in the main downwind the thing would fly. Downwind with a chute is a blast once you get it all tweeked. Getting the battens to go over (inverted sail) in light air happens to all of us. Just grab the back off the boom and give it a quick pop, then sheet in.

Doug

Thanks Doug, i have been flying a spin for over a year and 1/2 now (on my second spin and second snuffer bag). I use it often (as often as i can) and have a good feel for using it... It is a blast and i wouldn't want to sail without it. When i can't rig it.. i am always missing it.

I know about popping the battens over with the boom.. but this requires a few snaps/bangs of the boom and puts a lot of stress on the sail. I have already had 3 tears in my other sail (along the batten pockets) until the sail shredded through 2 pannels.

I really want to take it easy on this sail... and plan to change out from foam to fiberglass battens as soon as i have the time (the fiberglass ones are from my now shredded sail, in my car, waiting to be used). i KNOW this will handle that problem.

The sail you see in the pics was used more for heavy air and the inversion is not a problem. I will probably purchase another sail, more for light air conditions (i actually have one to try)...

Andrew:

Get a Sqauretop. The Pentex one I got really was nice in light air and heavy air (as it would spill off).




Doug

That sail is a mylar squaretop (as was my last one that i shredded last month)

it was used by a professional Torando team.

We purchase them used through Robbie D.

Andrew:

My Pentex sailed 4 HARD season and was still like new when I sold it. NOW the old Hobie Mylar was in BAD shape and separating. BUT Pentx is tough. Try one.

Doug

Cool. i am limited to either purchase a slightly used mylar T sail, or get a custom one (any style) made. I have an old mystere sail i could use as a template, a custome Bob Curry/Saber one too..

Custom pentex would be around 2500 (est)
Custom med sq dacron around 1500 (est)

Used (very good condition, but not for pro racing)
mylar.... $800-$1200

Andrew:

Bob Curry cut the Pentex sail in the photo. You can't go wrong with one of his sails. Pentex doesn't get like a dacron sail, you FEEL every puff, which is really nice in light air. I was moving when others where sitting still.

Doug

very cool.... of course, Bob is no longer at Saber... i think he is doing weather with the AirForce, but i could be wrong about that ,,,

Andrew:

Use this link:

Bob Curry Link

Click on his profile at the left and send him a PM. He lives in Fla and can probably hook you up with a sail maker in the area. He is a real nice guy.

Doug

So I think most of the problems you have are due to running a Tornado sail with a luff curve designed for a Tornado mast (alu or carbon??) on an Mystere mast with Mystere spreader rake & diamind tensions. Of course the sail will not be shaped properely.

To try to get that sail working better, try tipping boat on its side and hoisting the sail up the mast, but not in the sail track. Then compared the sail's luff curve to the existing unloaded curve in the mast. You want these to be nearly the same. Adjust spreaders & diamond tensions to get them as close a possible, and you're good to go. On the T with carbon mast, we go for a range of 25-55 mm of spreader rake (as measured from the track aft edge to a line or batten laying across the spreader arm tips). Actual setting depends on crew weight and wind strengths). For diamond tension we run a #34 on the newer/black Loos gauge...not sure what this equates to in LBS.

Stiff battens are awful to sail with...sail will be very flat and boat will feel dead.

If you have too much trouble "popping" the main on tacks/gybes...something else is wrong...I'd suspect too little mast curve, giving excessive sail body...but that assumes the luff curves match correctly. This reminds of when I tried fitting a non-prebend sail to a prebend mast...looked horrible and had trouble popping the sail. Slow as hell performance.

there was a fair amount of downhaul.. but not MAX...

the OVER bend/flattening is VERY noticeable with wind (even light) on the sails.

The origional 5.5 Mystere main from NORTH was tits. If you can get ahold of an old one for patterns or have North make you another, you'll be way better off than trying to half-butt a cut down Tornado sail on there.

But yea, Stu's right - you do have a serious amount of pre-bend on that sucker.