What have Ullman done here?

Looking at the top of the mainsail in the picture linked to below, there is some reinforcement running from the headboard to the leech of the sail. Anybody who knows what kind of reinforcement this is and what the point/theory/improvement is?

http://www.catamaranparts.nl/foto/g5.jpg

My sail has a strip of what looks like a kevlar uni tape(or carbon, it's been awhile since I've looked at it) in the same position as the top diagonal strip in the photo.

I assume that because the leech tension can't be transferred around the very top of square heads, the tension will pull along those lines. If extra tensile reinforcement (such as is already in the leech) wasn't there, it would stretch the un-reinforced material.

That is what I also thought, but why have we not seen it in other classes with square tops, like the F-18 and the Tornado? I always thought the heavy top batten was taking the loads going over the square top.
It can not be from lack of a suitable material, 10K denier spectra is available and not prohibited in the class rules. Hmm..

Actually F18's and other have similar devices as well. It is very noticeable on this Ullman sail but since then I've recognized similar things in sails of many other designs. Pretty much the leech load on a large squaretop sail is about 400 kg. If all of that or most of it is taken up by the batten then you would simply push the batten through its cap on the luff and jam it into the luff rope and sail track. This is actually what happens on my sail when I use stiffer top battens to flatten the sail. I had to bolt the whole assembly up to repair this issue. Since then I've stopped used stiffer battens to flatten out the top and just found other ways (trim) to get a similar effect.

The Ullman sail has two of these tapes in the sail and overdid it. The top of the sail (squaretop) now just weathervanes even in sub trapeze conditions and now amount of leech tension can bring it back. Together with the owner of the boat we looked long and hard at it and even put the boat on its side and cranked on the mainsheet to see what happened there. The top 500 mm just flaps about in the wind.

Personally I think this setup may be regard both as a benefit and a serious drawback. For a novice sailors this sail is very easy to use as it is impossible to oversheet the mainsail which would make the boat feel really bound up and slow. Additionally the boat is mild mannered. The drawback is of course that a capable crew is blowing off power that they otherwise could use to become really competitive. Double trapezing upwind is extremely rare with this sail. It seems the experience is that it is surprising good for singlehanded sailing but a little underpowered for doublehanded sailing. Pointing with it is difficult as well. Probably because the leech falls aways too soon. Careful mast rotation control and really well adjusted downhaul can get it back up to speed and recover some pointing (when doublehanding) but it is difficult.

It is not a bad sail but it was expected that a renowned sailmaker like Ullman would have come up with a more convincing design. In my personal opinion the new Glaser sails are heaps better. And I would even go as far as to claim that the recent achievements by Matt and Gina McDonald are to a significant extend the result of switching to a Glaser main sail.

I think Ullman needs to look at the experiences with this design and develop a new F16 sail that adresses these issues. If it remains as it is now then it will not be comparable to competing designs from Glaser, Ashby and soon enough also Landenberger.

Wouter

I still can not remember seeing similar things to this done on other square top mainsails, and I really think I would notice?
The way you describe it, it sounds like a fickly thing to get right. Wonder what happens with the sailcloth around the reinforcement, as it would probably stretch more and create point loads in the cloth.
Hmm, if done like that, perhaps even a crosscut dacron sail can be buildt to give reasonable performance..

To me it just looks like they have found a loophole -- can't use more battens, so just sew more "reinforcement" strips on the sail instead. Interesting idea.

I dont think the battens are regulated under the F-16 rules, are they?

I don't know about the F16 rules, but it sure would be a good loophole under some class rules.

Maybe battens will someday be obsolete if they can just sew in reinforcing that does the same job as battens. <img src="http://www.catsailor.com/forums/images/graemlins/smirk.gif" alt="" />

If you can come up with a layout of reinforcing that will match the performance of a fully battened sail, apply for a patent <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
I dont think you will tough, the battens are needed to keep the shape in the sail and work somewhat under compression. Without them the shape will be difficult to control and excessive roach and square tops would have to go.

Rolf,
But if a class is limited to X number of battens, and you would like to have another batten here or there to supplement and stiffen certain parts of the sail, this looks like a good way to accomplish that without violating the rules.
P.S. Depends on what the definition is of "batten."

Does it matter? sail, sail and sail some more and I still don't think you'd notice a difference between U,Sails. G, sails or probably the fastest F16 sails, Landenberger. In my humble unbiased opinion. (Wouter) and enjoy the attachment.

That looks like a nice spot for a sail, Mark <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

I have to say that I experience a lot of the same symptoms as Wouter describes about the Ullman sails. 1-up it's quick, but it doesn't point. Whenever we're sailing together, Mark, if I try and point where you point I just don't go.

Sailed 2-up: yes, twin trapezing is rare. I'd expect it to be more powered up. There are definitely some issues with the jib which I'm still working on. It's easy to get obsessed with the finer points of tuning a sail, but if you're looking at a sail and thinking "that looks like s**t" there's probably room for improvement.

Paul

Just about to order a new sail and I'm wondering whether to go US, Aus, Far East, rather than European sails which have become very expensive in my view, any thoughts guys and girls about some of the smaller manufacturers such as Randy Smythe and what did you pay for your sail ( recent prices please ) <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

There is only one way to get it just like you want it.. Build it yourself <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />
Seriously, I find the prices in Aus good. You want to buy the sail from a sailmaker who knows the boats, rigs and sailing techniques. You probably also want him to tailor it somewhat for your conditions. This means you can not just go to any sailmaker and expect a good sail. I dont know any sailmakers who qualify in the far east, but there are several in Aus and the US.
What is Ashby charging for an F-16 main these days? Glaser lists US$1300 on his site for a main, but I dont know how current that price is. Landenbergers site is just re-done and dont list F-16 sails at all.

I think your mast rotation has a lot to do with your upwind performance. At Grafham I thought you had the edge on me in pointing/speed ability but prior to that I felt more confident in my own boats performance. I put this down to your mast rotation being better tuned bearing in mind you have a wing mast compared to my standard section. So in summary I believe that if you have a wing mast you have to play the rotation a lot more than the standard section. The good 'A' Class sailors and some F18 Sailors are getting this additional tunning down to a fine art and I suppose it wont be long before the F16's follow suit. Although, for me it just seems like you can gain as much as you lose by having the rotation just right or badly wrong.

Ashby mainsail is aus$1550.00 plus battens aus$330.00. I agree with rolf build your own then you get what you want sail makers will sell you the panels if you ask i use the demo version of pro sail design then take to my local sailmaker put in the detaile to his computer he charges me for the cloth and a cutiing fee i take home and put together photo is of the f18 sail i made. Yes this is Blade Mk1 f18


Taipan (not finished yet)

I do not understand the forces on a batten that would push it through its cap. It seems like that would require a force parallel to the long axis of the batten. Would you elaborate on the physics of this statement?

I'm quite interested in getting a set of Glaser sails. The exchange rate makes it quite attractive: jib, main and battens for just over £1k. Not sure what'd cost to get it here, though.

Paul

The strip is not stiff in bending or compression, only tension. Therefore it is not a batten, it is soft like the surrounding sail.

It take the tension rather than the surrounding clothe so the clothe doesn't stretch.

To understand the forces on the top batten, imagine there is no clothe; only the batten and leech tape (including the top leech tape). Then pull down on the trailing edge leech tape and you will see the batten is compressed.

So instead of this force travelling around the leech tape and compressing the top batten (which will push depth into this part of the sail), it is predominantly bypassed along the reinforcement that is shown in the photo, leaving the top batten with its pre-compression only.

Thank you. I get it now. I had never appreciated the fact that a square top sail's leech is like a bow string.

I've been thinking about it some more and realised there is another aspect to the functionality. A couple of other points are...

Without the reinforcement tape, the leech tension would still be transfered to the head along that bypass route more than over the top of the head, but the sail material would stretch more.

This tension along the bypass route also holds the batten relatively straight where they cross. Imagine the bow string analogy (that's a good term for it) with an extra bow string going along the bypass route and fixed to the batten where they cross. The batten will be held there and bend either side of it. You can see this if you capsize your boat on land and crank the downhaul on till the top is completely flat and the batten starts to behave funny, it may even invert.

Back to the original question.

If you look closely at the panel configuration of the sail you can see the panels closest to the luff appear to converge at the head of the sail at the halyard lock. But look at the panels towards the rear of the sail & you can see the panels start to depart from the head point & spread out over the width of the head. Ullman have simply put the reinforcing tape to help the panels that do not align with the head board. Radial sails need the seams to be as close as possible to the load lines as the maximum strength is primarliy along these lines. It is extremely difficult to satisfy all the loads at the top of these sails & I dont believe any sailmake has solved the problem......but it looks as though Ullman are heading in the right direction by covering both bases as you can not configure you panel layout to the forward head of the sail as the material in the upper panels with self destruct in a short amount of time & sailors will be pissed off. <img src="http://www.catsailor.com/forums/images/graemlins/mad.gif" alt="" />

Most sailmakers (they are generally restricted by their software)will spread all of their head panels evenly across the head of the sail & try and get the head reainforcing to pick up the shortfall that occurs as a result.

An interesting point out of all of this is that F18 would not allow this type of construction as I tried to enquire about a tape drive style of sail & was informed that if the sail was likely to cost more the class rule was likely to prohibit it. <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />

Ok, thanks again Marcus.

So the reinforcement is there to take off-axis loads from the cloth. Much as suspected, but it would be very interesting to see the result from a finite element stress calculation.


Adding some high modulus tape like this can not drive cost up much(?) Doing a tape/string sail on the other hand.. But prices are dropping there as well.