Mainsail Shape for Bluewater Cruising

[myocean]

You think the square top could break? Is that realistic?
We would in principal carry the old main as spare.

[geoleo]

Any Remer needs a hot sail! Get that fathead!

[Stumble]

Originally Posted by myocean

You think the square top could break? Is that realistic?
We would in principal carry the old main as spare.

It certainly could, but isn't any more likely than a pin head (ignoring wear on a backstay if there is one). The loads on all multihull sails are just significantly higher than on a comperable monohull. This is why multihull sails have significantly reinforced headboards compared to a mono. It's a feature of the boat not the sail design.

[daddle]

Originally Posted by Stumble

It certainly could, but isn't any more likely than a pin head (ignoring wear on a backstay if there is one). The loads on all multihull sails are just significantly higher than on a comperable monohull. This is why multihull sails have significantly reinforced headboards compared to a mono. It's a feature of the boat not the sail design.

This not a monohull thing. Its a sail thing. Ask your sailmaker. Roachy sails have much greater leech loads. The vang or traveller loads of the square top main will be much large than that of the elliptical. Those loads keep the top 'in' where it needs to be to do anything useful. That load goes directly into the upper battens which then bear against the mast. On my old race boat with a very long top batten that batten car and pocket were regular service items. When the batten or car failed the sail was useless.

Some boats have pathetic vang and traveller systems. The extra load may make both difficult to use. So check that. I have raced cats with silly travellers that needed to be low-speed winched to weather. Took ten minutes for a simple trim change. Silly.

[Stumble]

Daddle,

Multis also have higher loads than a mono, because the boat doesn't heel to depower the sail. Instead the sail loads up. So a multihull sail of the same size and geometry will always have higher loads than a mono in the same wind speed.

[careka]

Fathead. in trirad-cut.

[mikereed100]

Myocean,

Were I in your position I would get quotes from as many sailmakers as I could. A good sailmaker will listen to your requirements and make recommendations based on your needs. They should also be able to answer questions you may have on your options. For 15K you should get more than "should be easy to reef".

[islandplanet]

I would not waste money on crosscut Hydranet. It has little advantage over a premium Dacron. Use the radial Hydranet. Or consider a good load path sail.

[Hammer]

+1 on a square top sail.

[44'cruisingcat]

Originally Posted by Stumble

Daddle,

Multis also have higher loads than a mono, because the boat doesn't heel to depower the sail. Instead the sail loads up. So a multihull sail of the same size and geometry will always have higher loads than a mono in the same wind speed.

Not always. deep reaching or downwind, we'll go faster, see less apparent wind and have lower loads.

[myocean]

OK, I will go for the tri-radial version. Should be ready in February/March :-)

[Kestrahl]

Originally Posted by islandplanet

I would not waste money on crosscut Hydranet. It has little advantage over a premium Dacron. Use the radial Hydranet. Or consider a good load path sail.

100% correct, Crosscut Hyrda-net is out performed by some of the better dacrons. However it does have greater tear resistance which is something to factor in on a cruising boat, but for the price it is a rip off. Laminates i.e. loadpaths won't last as long as anything woven.

I'm a ex sail loft owner from NZ who is currently cruising

For your application I would recommend the hydra-net radial.

The roach on the cross cut main looks ideal, and easy to manage, just get him to do a radial version of the same sail.

The CE going forward when reefed is no problem, upwind you are partly furling the headsail to balance the rig. as soon as you go off the wind you want the CE in the sail plan further forward to balance the boat, the further downwind you go the further forward you want it. This is why you see skiffs with huge long prods and gennakers putting the CE way forward downwind, they don't have lee helm, it is balanced.

His radial layout is wrong in the head for square head and will cause diagonal creases.

[myocean]

Originally Posted by Kestrahl

The roach on the cross cut main looks ideal, and easy to manage, just get him to do a radial version of the same sail.
(...)
His radial layout is wrong in the head for square head and will cause diagonal creases.

Thanks a Lot for the very valuable inputs - great!
Where come the creases from?

[Kestrahl]

Its not to bad, I have seen some lagoon's etc while cruising with square head made from soft dacron with creases going everywhere....

Red line shows where you will get bias creases with his layout. Other pic is what the layout in the head should look like, ignore the rest of the sail. Of course this is just my opinion from personal experience.

[islandplanet]

Kestrahl is spot on in his analysis of the design. One question I'd be asking if I were in myocean's shoes, is how many multihull mains like this has the sailmaker done.

Back to material for a moment, I agree that the hydranet radial, being a woven, will outlast most load path sails. However, the life cycle cost of the load path sail may be less. Hydranet radial is ridiculously expensive and I'm not convinced it lasts a commensurately longer period of time. So take the cost of the respective sails, divide by the anticipated service life, and compare results.