Laminated sails vs Dacron durability

[Drek4]

Originally Posted by wingssail

Absolutely! Weight aloft is detrimental to stability. It was this characteristic of laminated sails (more than their shape holding ability) which led to laminated sails being developed in the first place. Otherwise top end racing boats could simply buy a new (heavy) Dacron sail every few months, replacing them before the shape changes, and probably save money.

But for all boats, racers most of all, light weight is worth the premium.

Again, thank you for your interesting post.
Looking at it with that perspective, I now understand more the enthusiasm towards laminated sails.

[Drek4]

Originally Posted by markiobe

Short answer: yes.

Longer answer: there is no situation where weight up high is a good thing. One of the advantages to laminate/film sails is they are typically lighter for a given size than a woven cloth. This gives significant sailing advantages as well as making them easier to handle. This is not just for racing, less weight up high will reduce heeling moment and reduce hobby-horsing, both of which are relevant to cruising sailors! This issue is the reason why hydranet is only a kind of halfway house, it keeps its shape much better than Dacron but is really heavy.

Weight up high is also the main reason for carbon masts and dyneema standing rigging. Racing boats (where the class rules allow) will go to the trouble of tapering halyards so that the line is as thin as possible up high and only thicker where they are going through cleats/clutches etc.

Thank you for sharing this information.
In my case I would have to steer clear of sails that are heavy, since I will most likely go with a shorter keel version (5'-6'(1.5m-1.8m)) sailboat.
A sailboat with a shorter keel will be certainly more impacted with a higher center of gravity.

[Adelie]

Originally Posted by Drek4

Thank you for sharing this information.
In my case I would have to steer clear of sails that are heavy, since I will most likely go with a shorter keel version (5'-6'(1.5m-1.8m)) sailboat.
A sailboat with a shorter keel will be certainly more impacted with a higher center of gravity.

Shorter keel can be made up for using a bulb, or more ballast or lead instead of steel as the ballast material.

Shallower keel does not automatically result in lower stability.

[Drek4]

Originally Posted by Adelie

Reducing weight aloft is great for racing it allows a boat to reef a little later than competitors and maintain a slightly higher speed a little longer. But the OP is cruising.

One could argue that the speed advantage might be a safety consideration but let’s say you consistently gain 0.1kt (probably an overstatement but let’s be generous), that’s 2.4nm/day which not really enough to outrun bad weather unless you were already close to a protected harbor.

But then you might argue that the reduced weight aloft increases stability is a safety advantage because it increases capsize resistance in breaking waves but that’s WRONG.
Following the 1979 Fastnet race research showed that sailboats without mast had vastly more stability, had a greater Angle of Vanishing Stability and were much more susceptible to capsize. Blew everybody’s minds, highly counter intuitive.

Ultimately they realized that stability is a static phenomenon (even when the boat is moving) and capsize is a dynamic phenomenon and roll moment of inertia is a primary consideration. Turns out that the mast contributes about 50% of the roll inertia despite only being 2-5% of the mass.

In this case the weight of the sails should not affect capsize resistance either way because by the time you are in survival conditions with breaking waves you should have regular sails secured with storm sails up.

It falls on the OP to decide if the marginal gain in speed is worth the added cost.

Thank you very much for your very informative input.
I feel much more at ease now, for a moment I thought that the stability of the sailboat due to the added weight of stronger sails would be drastically affected, if ever such sails were chosen, and also that this would increase the capsize formula.
I guess I will have to keep all this in mind when comes time for the final choice, because price would have to be juggled with all these factors also.

[Drek4]

Originally Posted by Adelie

Shorter keel can be made up for using a bulb, or more ballast or lead instead of steel as the ballast material.

Shallower keel does not automatically result in lower stability.

Again, I'm in your debt for kindly sharing.
You're right, those can compensate and make it more stable.
Most of the sailboats I envision owning, are on the lighter side though, so I still have to limit the weight that will be higher up the same.
Just for a moment I saw myself bobbing like a cork in the middle of a vast sea.

[Drek4]

Originally Posted by pjShap

A simple example of elevated weight: Removing 100 pounds centered 30 feet above the deck is equivalent to putting 500 pounds on the rail of a 12-foot beam (rail is 6 feet out from the centerline).

Thank you for your reply.
I do agree that, reducing elevated weight, should make for a smoother sail.

[Jammer]

Originally Posted by pjShap

A simple example of elevated weight: Removing 100 pounds centered 30 feet above the deck is equivalent to putting 500 pounds on the rail of a 12-foot beam (rail is 6 feet out from the centerline).

I don't believe that is correct. While the inertial moment is the about same (100*30=500*6, around some axis on deck) the effect on sailing would only be equal at 45 degrees heel. At a typical 20 degree heel angle the effect of 100 pounds at 30 above the deck, on heeling moment, would be the same as 180 pounds on the rail. 100 * 30 / 6 * tan (20 degrees)


But weight aloft reduces performance in many other ways also

[pjShap]

Originally Posted by Jammer

I don't believe that is correct. While the inertial moment is the about same (100*30=500*6, around some axis on deck) the effect on sailing would only be equal at 45 degrees heel. At a typical 20 degree heel angle the effect of 100 pounds at 30 above the deck, on heeling moment, would be the same as 180 pounds on the rail. 100 * 30 / 6 * tan (20 degrees)

My mistake. Jammer is correct.

[Drek4]

Originally Posted by Jammer

I don't believe that is correct. While the inertial moment is the about same (100*30=500*6, around some axis on deck) the effect on sailing would only be equal at 45 degrees heel. At a typical 20 degree heel angle the effect of 100 pounds at 30 above the deck, on heeling moment, would be the same as 180 pounds on the rail. 100 * 30 / 6 * tan (20 degrees)


But weight aloft reduces performance in many other ways also

Thank you for the correct calculation, we should be using.

[Drek4]

Originally Posted by pjShap

My mistake. Jammer is correct.

Thank you for your input.