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MedSailor 02-22-2013 10:24 PM

Mainsail Design Question...
 
Many sail lofts offer "crosscut dacron" or "tri-radial" dacron and then varying levels of laminates and "string sails".

For the dacron options, what benefits does one get by going with tri-radial instead of the standard crosscut? I've seen the difference between the two vary from adding 60% to the cost at one loft, to 75% to almost doubling the cost at another loft.

I understand that it's a "stronger" construction, but what does that translate to? Does that mean a lighter weight cloth can be used and the primary advantage is less weight aloft? Does the design allow for less stretch which means your draft moves aft less and you end up heeling less in higher winds? Does it stretch out less over time and thus last longer?

What do you actually get, performance wise, or longevity wise, for your extra dollars with this feature?

MedSailor

Faster 02-22-2013 10:58 PM

Re: Mainsail Design Question...
 
I think it's a "yes" to most of your questions... Much of the extra cost would be in labour for sewn triradials. If this is not just a hypothetical I'd suggest that crosscut is what you want for your boat.. Likely not realize the performance benefit of triradials (jmo)..

SchockT 02-22-2013 11:15 PM

Re: Mainsail Design Question...
 
Radial sails are used with laminate cloths. The panels are oriented so that the fibres in the laminate are aligned with the load path. That allows them to use cloth that has most of it's strength in one direction. The result is a much lighter sail.

Woven cloths like Dacron have more uniform strength in both the warp and fill directions, therefore they do not need to be aligned with the load paths on the sail. Instead they just make panels the width of the roll of cloth. (The width is the "fill" part of the weave and has a higher thread count than the length, or "warp" of the roll so it is a bit stronger in that direction) Because dacron is stretchy, it requires more fibres to resist the stretch, making the cloth much heavier than laminates. Cross cut is far easier and therefore cheaper to build.

The crosscut dacron sail will be cheaper and more durable than a radial laminate sail, but it will also be much heavier. Dacron is also easier to repair with basic tools and materials.

Laminates sails are much lighter and hold their shape better but are more expensive and won't last as long. If you don't race you probably don't need laminate. Unless of course you have lots of money and love the look of plastic sails!

I don't know why any sailmaker would make a radial sail out of Dacron, it seems to be pointless to me. I suppose they could align the fill with more precise load paths to gain a bit of strength and stretch resistance but I would guess it would be an incremental benefit for a much greater cost.

MedSailor 02-22-2013 11:50 PM

Re: Mainsail Design Question...
 
It's definitely a tri-radial dacron that I'm looking at from a couple different lofts, not a laminate. I've made my decision on laminate and I'm definitely going with white (dacron) as I don't have the green for laminate.

I am inclined to agree with Faster that I might not see much performance benefit (ie go faster) from the radial construction but what about longevity? Could I expect an extra year or two, or an extra 50% life out of a radial vs crosscut sail?

MedSailor

SchockT 02-23-2013 01:01 AM

Re: Mainsail Design Question...
 
Quote:

Originally Posted by MedSailor (Post 993803)
It's definitely a tri-radial dacron that I'm looking at from a couple different lofts, not a laminate. I've made my decision on laminate and I'm definitely going with white (dacron) as I don't have the green for laminate.

I am inclined to agree with Faster that I might not see much performance benefit (ie go faster) from the radial construction but what about longevity? Could I expect an extra year or two, or an extra 50% life out of a radial vs crosscut sail?

MedSailor

The only advantage to a radial dacron sail would be the ability to have more control over the initial shape of the sail, and to utilize the stronger yarns of a given sailcloth. some performance dacrons are woven warp-oriented, so they can optimize the load paths without panel lengths being limited to the width of the roll. While it would probably hold it's shape longer than the cross cut sail, I doubt it would last 50% longer. The cloth of both sails is still going to loose it's resin and break down.

Of course this also assumes that both sails are being made of similar weight and grade of cloth.

overbored 02-23-2013 01:24 AM

Re: Mainsail Design Question...
 
the one thing I have noticed with my older sails which are all Dacron warp drive cloth and tri radial construction is that the first thing to go is the leach. the sails seem to get stretched there first. they were used for racing only. and are still not that bad but not good for racing. I would not buy one for cruising, to expensive and need to be handled with care. go with a cross cut and a good grade of dacron. up grading the cloth will cost more but not as much as the tri radial cut. and will last a lot longer

blt2ski 02-23-2013 08:54 AM

Re: Mainsail Design Question...
 
For around here, assuming you stay in puget sound.......a lighter stronger sail will be better for the lighter winds we have a tendency to have. So from that standpoint, a tri radial would be better.

Another option that I've noticed to be less than triradial, a bit more than dacron.....you may not like as it is all laminate, is the Ullman CAL sail. This is a cross cut laminate sail, maybe 20% ore than a decent made dacron. I have a 140 out of it, very strong pulling sail. Should have gone with my main that way instead of a string style. Talk to Chris or Jeff at the seattle loft if you think this might be a viable option.

I would not get a North norlam from my experience. These seem to have a short life span, shorter than some true laminates. The cal I have is doing better life wise etc than the nor-lam I have.

Marty

Jeff_H 02-23-2013 10:49 AM

Re: Mainsail Design Question...
 
Tri-radial Dacron sails usually benefit from a variety of things. First of all Dacron tri-radial sails are usually made from warp oriented cloth. Most cloth has an equal fiber in warp and fill threads, but warp oriented cloth has heavier threads running the length of the fabric, and between the heavier weight and higher tension on the warp, the thread lie straighter in the cloth. When woven cloth stretches the biggest initial portion of that stretch is the threads pulling straighter so that alone reduces stretch.

Because warp oriented cloth is a premium product it is made with higher quality Dacron, and usually goes through a more rigorous inspection program than the commodity Dacron cloth which is often for cross cut sails. That alone helps increase the life of the fabric.

If you look closely at a fabric, there are little squares formed between the vertical and horizontal threads. The cloth is strongest and stretches less in the direction of the threads. The diagonals of the square holes between the threads is the 'bias' of the fabric. These square holes distort into parallelegrams when the stress does not align with the threads. This results in greater stretch than a similar stress would cause parallel with the threads. In a cross cut sail, the stress pattern in the sail is such that it causes bias loading a throughout a larger portion of the sail and therefore greater stretch in the sail.

Radial cutting of a sail allows the panels to be better oriented to the stress patterns in the sail. This means that there is less bias stretch. And because the cloth is generally higher quality and the stress follows the path of the fibers, and the fibers are less distorted there is much less stretch.

Stretch of course is a bad thing in almost all ways. To a racer it means poorer upwind ability and a less stable flying shape, but to a cruiser, it means a sail which is powering up, just when you want the sail flat. The problem with a powered up sail is that it causes more heeling and weather helm, so you end up reeling much sooner than you might with a lower stretch sail.

But also,when threads stretch they spring back to something close to their original length. That ability to remain elastic is one of the nice things about Dacron. But every time it stretches, it does not return perfectly. Instead it grows ever so slightly longer and never returns to its original length. That is called creep. Cumulatively it is creep which ultimately spells the end of the useful lifespan of a Dacron sail, before it has deteriorated into the realm of a white triangle pretending to be a sail. The more the cloth stretches, the more creep occurs. Since cross cut sails stretch more, they tend to experience more creep. Creep means a fuller sail and for the cruiser that means more heeling and weather helm as well.

The reality is that your boat's performance will always be limited by the configuration of the hull and rig. You can easily argue that the performance gain of a radial sail would be minimal. On the other hand, you can easily argue that if anyone could benefit from a bit more performance, it might be your boat. You can also argue that the reduced heeling of a radially cut mainsail with warp oriented fibers would reduce heeling, weather helm and the need to reef, all really good things. And lastly, the greater lifespan of the radial sail may pay for itself over the life cycle of the sail.

I also think that none of us can specifically answer the question of what is right for you. These are preferential questions. Only you can evaluate your priorities, who's much sailing you do in gusty, or windy conditions, first cost or life cost and so on. There is no single, universally correct answer here.

Respectfully,

Jeff

MedSailor 02-23-2013 01:44 PM

Re: Mainsail Design Question...
 
Quote:

Originally Posted by Jeff_H (Post 993954)
...The reality is that your boat's performance will always be limited by the configuration of the hull and rig. You can easily argue that the performance gain of a radial sail would be minimal. On the other hand, you can easily argue that if anyone could benefit from a bit more performance, it might be your boat...

Hey!!! That's my girl you're talking about there!:mad: Though you do make a really good point, so I guess we're still friends. :p

Decreasing creep so that the sail retains its shape longer certainly sounds like an advantage whereby it will last longer especially in conditions where it is sailed harder and closer to the wind.

How about the other ways to destroy a sail? Is leech flutter/flogging from reefing worse on tri-radials or do they handle it better than crosscut?

I've heard that warp oriented dacron can be more U/V sensitive. Lucky for us there is NO UV up here. ;) On the other hand our plan is to depart in 5-7 years from now to Mexico --> South Pacific--> circumnavigate Australia. There is plenty of sun on the later years of that route, but I wonder how long my sail should be expected to last into that plan anyway? And would it last longer/go further if it is a tri-radial?

Also I've heard that some of the warp-oriented cloth actually wasn't as good as advertised and they wore out much faster than crosscut. Do you think they've figured out this (warp-oriented dacron) technology now or is it still "too new"?

MedSailor

Jeff_H 02-23-2013 05:23 PM

Re: Mainsail Design Question...
 
Med, I mean no disrespect to you or your girl. We all love our boats for different reasons, and of course overall performance is but one item that you may or may not cherish. In the end the best boat for anyone is the one that we think works for us.

But to address your questions, these are questions best addressed to the specific sail maker who is making your sails. There is a tendency to think of terms like radial construction or warp oriented fabrics as if these terms describe something very specific and as if they describe commodity items. In fact like so many things in sailing, these terms are very broad generalities but the reality of how good or bad these are, lies in the specific execution.

But also this is one of those areas where purpose can trump lifespan. The technology is nothing new. That concept has been around since cotton sails. But its how it gets used.

For example not all radial sails employ warp oriented cloth, and not all warp oriented cloths are made the same. Only the sailmaker who is quoting the sail can explain what they plan to use and its various advantages and limitations.

But talking more generally, Warp oriented cloth is one of those cases where the generality means very little and the specifics are the real truth of the matter. The last time that I had looked at warp oriented dacron, there were a wide range of products out there. In some warp oriented fabrics, there was only a small difference between the warp and woof threads. But in other products, mostly intended for race boats looking for a PHRF cruising sail credits, there was a huge difference in the weight of the warp and woof. That sail cloth was pretty short lived in the leech where fluttering and flogging stresses the horizontally oriented, weaker woof fibers (rather than the stronger vertically oriented warp) to a premature failure.

I have not heard anything about a shorter UV life, but my guess is that in the heavily biases clothes, the weaker (thinner) thread could sun rot sooner and fail.

I wish I could be more specific but to do so I would need to also be speculating or else talking to your sail maker. What this does hint out is one reason not to buy mail order sails. A good sailmaker will spend time finding out about how you plan to use the sails and your personal preferences and then discuss their approach to meeting your needs in enough detail that you can make an informed decision about how thier recommendations dove tail with your own needs and wants.

Jeff


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