I don’t understand sail cloth weight.

[Bully]

Originally Posted by Baronkrak

That brand has a good pedigree.

https://www.challengesailcloth.com/
Challenge Sailcloth is owned by the Bainbridge Family, who founded the first Global technical textile company, Howe & Bainbridge in 1917.

Yes, they make some nice cloths, we use them and dimension polyant mainly

[Baronkrak]

Originally Posted by Bully

Yes, they make some nice cloths, we use them and dimension polyant mainly

Does the German use oz UK or oz USA?

Do you also use Fibercon Hybrid?

[Baronkrak]

Originally Posted by s/v Jedi

The force on the sails is a combination of wind speed and the boat’s righting moment. If you reduce sail area, that smaller area will have to overcome the same righting moment so it needs to be stronger.

Except for multihulls, they will rip it apart so they must reef early until they can’t have any sail up anymore.

I do not follow your logic. For a given wind speed the pressure on a sail does not depend on the area of the sail.

[s/v Jedi]

Originally Posted by Baronkrak

I do not follow your logic. For a given wind speed the pressure on a sail does not depend on the area of the sail.

That’s a shame. Let me try again:

It’s not just wind speed. If you hold the sail up vertically in 20kts wind and not give way to the force then you have more pressure in the sail than when you give in and flip the sail horizontal.

So the pressure in the sail is a combination of the wind speed and the righting moment of the boat. For the same windspeed, a boat with a higher righting moment requires a stronger sail. Also, for the same boat, a smaller sail needs to heel the boat to the same amount which it does because it’s used for higher winds. So the total force of the sail is the same as for the bigger sail which means the force per square foot is higher and thus requires stronger material.

This is completely normal. Sails for high winds are smaller and made from heavier materials. For cats, which have a really high righting moment, the sails need to be stronger just like the rigging, the mast etc.

[hpeer]

Originally Posted by GILow

Sort of. I told them where I’d be sailing, and it’s an area they know well.

But I think Jedi has nailed the reasoning. Certainly what he said makes sense to me.

Thanks for going back to Jedi's excellent comment.

Yes, that the sail area needs to match the boats righting moment, so smaller sails need to be stronger.

But it also gave me another thought relative to cutters. Do you weight the jib cloth assuming the stay sail is up or down?

Very roughly my working jib is 350, and my stay sail is 250 or about 600 total.

So when figuring cloth weight do I assume the stay sail is up and sharing the load or down and the jib needs ro take all the load?

Going back to my boats first set of sails, 1984, as per the boats designer.

Meters and UK Oz
Genoa 67m, 8oz
Jib 31.5m, 8oz
No2 21.9m, 9oz
Stay 19.8m, 10oz

Main 47.1m, 10oz
My jib + Staysial are 50m.


English 10=US8
English 8=IS 6-1/4


So the saulmaker gave the PO furling Genoa of 120z US weight vs.designer specified 6-1/4 Oz. No wonder it did not work.
The main he provided 12Oz vs 8oz.

My jib + staysail is 50m, with the stay being heavier. Which makes sense as you would fly both then step down to stay alone in heavy weather.

Kinda struggling to think this through myself. And cutters are different than sloops or even double headsail sloops.

Hope this helps.

[Baronkrak]

Originally Posted by s/v Jedi

That’s a shame. Let me try again:

It’s not just wind speed. If you hold the sail up vertically in 20kts wind and not give way to the force then you have more pressure in the sail than when you give in and flip the sail horizontal.
.

At 20kts the pressure per m2 will be the same what ever the area is. Reducing the area will reduce the force.

[s/v Jedi]

Originally Posted by Baronkrak

At 20kts the pressure per m2 will be the same what ever the area is. Reducing the area will reduce the force.

Okay, I give up.

[Baronkrak]

Originally Posted by s/v Jedi

That’s a shame. Let me try again:......
Also, for the same boat, a smaller sail needs to heel the boat to the same amount......

Curiously on my boat I do not use the wind to heel the boat I use the wind to move the boat. Heeling is consequential and best kept to a minimum.

[s/v Jedi]

Originally Posted by Baronkrak

Curiously on my boat I do not use the wind to heel the boat I use the wind to move the boat. Heeling is consequential and best kept to a minimum.

I am sorry but you don’t understand the basic principles around sailboat design. Righting moment is a crucial factor that determines the required strength of standing rigging, sails, chainplates, bulkheads everything.

You completely ignoring righting moment even after me repeating it again and again means that further discussion is not fruitful.

[Baronkrak]

Originally Posted by s/v Jedi

That’s a shame. Let me try again:

It’s not just wind speed. If you hold the sail up vertically in 20kts wind and not give way to the force then you have more pressure in the sail than when you give in and flip the sail horizontal.

So the pressure in the sail is a combination of the wind speed and the righting moment of the boat. For the same windspeed, a boat with a higher righting moment requires a stronger sail. Also, for the same boat, a smaller sail needs to heel the boat to the same amount which it does because it’s used for higher winds. So the total force of the sail is the same as for the bigger sail which means the force per square foot is higher and thus requires stronger material.

This is completely normal. Sails for high winds are smaller and made from heavier materials. For cats, which have a really high righting moment, the sails need to be stronger just like the rigging, the mast etc.

I have a staysail. For the stay sail to heel the boat to 15 degrees the wind speed need to be 35.19 knots. That’s ok the maximum wind speed for that staysail is 35 knots.

[Baronkrak]

Originally Posted by s/v Jedi

I am sorry but you don’t understand the basic principles around sailboat design. Righting moment is a crucial factor that determines the required strength of standing rigging, sails, chainplates, bulkheads everything.

You completely ignoring righting moment even after me repeating it again and again means that further discussion is not fruitful.

https://www.biblio.com/book/sailing-...CABEgIJWPD_BwE

Recommend.

[GILow]

Originally Posted by Baronkrak

I do not follow your logic. For a given wind speed the pressure on a sail does not depend on the area of the sail.

Try this way of thinking of it perhaps…

A monohull tilts as a kind of circuit breaker for when the wind gets too strong.

The force required to tilt a monohull is constant for a given monohull, therefore the tilting force required from the sail is constant, regardless of the sail area.

If the sail is smaller then the force required from each available square meter of sail to tilt the mono has to be greater to induce the tilt and cause the circuit breaker effect. Hence the cloth has to be stronger to take the greater force.

[Bully]

Originally Posted by Baronkrak

Does the German use oz UK or oz USA?

Do you also use Fibercon Hybrid?

The Germans use grams per metre squared which is more accurate. That, the denier count and coating style are more what sailmakers look at.

We can use Fibercon Hybrid if customer prefers it. We tend toward DP Radial Hydranet for that style of application.

[Bowdrie]

GILow, it's not a big deal.
Get your "normal" light>moderate air sails made of Egyptian Cotton and the heavy weather sails of heavy Flax.
When the weather turns bad the cotton sails will blow-out, saving you the trouble of taking them down.
The Flax sails will hold-up till the spreaders go in the water.
All above is "tongue-in-cheek".

[Baronkrak]

Originally Posted by GILow

……
A monohull tilts as a kind of circuit breaker for when the wind gets too strong.

In doing that it reduces the area of sails exposed to the wind. That the beauty of ballasted monohull, a sort of self resetting circuit breaker, the mast may even touch the water, I have seen that.
There is other way of spilling the wind, Bowdrie did describe one.

Originally Posted by GILow

……
The force required to tilt a monohull is constant for a given monohull, therefore the tilting force required from the sail is constant, regardless of the sail area…...

Not really