Advice on sourcing a stayless rig

[alyne]

Hi

I am planning to build a small car toppable catamaran as a project for myself and my children. I could do with some advice on sourcing suitable rigging.

I want a simple stayless rig. Ideally I would like a windsurfer style rig as they are quick to assemble, relatively light and the mast splits for easy transportation.
Also there is no chance of the kids banging their head on a low boom. I am looking for about 100 square feet of sail area.

Could I use a windsurfer rig and beef up the mast some how? I have seen such windsurfer style rigs used before, for example the Alley Cat used such a rig.

Any suggestions greatly appreciated.

Thanks
Andy

[gonzo]

You can have a boomless main in a catamaran because of the large beam. One easy solution is a double set of sheets each leading to a hull.

[grob]

Andy,

I am using twin windsurfing rigs on the prototype car top catamaran I am building. My calculations indicate that a stayless wind surfing rig will not be strong enough. But it does depend upon the righting moment of your boat. How wide will it be and what is your crew weight.

I am told that you can beef up the mast by buying an extra top half that you slot into the lower half. This is something that Ice boat builders do.

Another thing to note is that although a windsurfing mast is not strong enough to take a high righting moment, it might be so flexible that it will just bend so much that you cannot generate enough righting moment to break it anyway.

All the best

Gareth
www.fourhulls.com

[alyne]

Thanks for the suggestions.

Since I am on a budget I think I will try a windsurfer rig and strengthen the bottom section - perhaps using your suggestion Gareth of an extra top section slotted into the bottom section.

I'm afraid I am a complete amateur just in it for fun, I wouldn't know where to start on calculating turning moments and associated forces

Gareth - I think your idea of a collapsable cat is excellent. I have always believed there is a big market for a quickly assembled car toppable cat. Best of luck with your ingenious idea.

Andy

[JPh]

Hi Alyne,

I have been thinking about a similar project, maybe not car topable but to be transported on a small trailer, the two hulls and beams would separate so the width would be similar to a car dimension. The rig I was thinking of is the Sunfish rig, its simple (check here page 3 http://www.teamvanguard.com/boats/c/...ishLocator.pdf) and more forgiving than a Laser rig (smaller boom and you can lower the sail under way), now the rig is self standing and would have been buried in one of the hulls making it a kind of a proa or better said an asymetrical catamaran.
My actual project is quite different, see link below.

JP

http://www.geocities.com/jp_br/Dreampage/Catamaran.html

[gonzo]

A windsurfer rig is strong enough to take you flying out of the water. The drawback, is that it is designed to be held from the boom. Are you planning on having your crew do that?

[grob]

Gonzo,

Not sure if this is directed at me or Andy, if its me the answer is no, it is not suppotred by the crew, but by stays connected halfway up the mast.

Gareth

[gonzo]

A windsurfer rig is very specialized. I think that modifying it with standing rigging is a mistake. The advantages of this rig are its flexibility and changing CE. Shrouds will take that away and overstress it.

[alyne]

Gonzo

What are your thoughts on the idea of instead of using shrouds on the windsurf rig, strengthening the lower section by inserting a second inner tube.

I appreciate what you say about spoiling the inherent design of the rig, however as I am on a budget I would like to experiment with the use of such a rig.

Andy

[gonzo]

Do you have the rig already? If not, you can use the sail and boom with an aluminum tube section.

[alyne]

No, I havn't bought the rig yet. I think it may be time for me to get down to my local aluminium supplier.....

Thanks for the ideas everyone

[grob]

Andy,

Do not use aluminium tube with a windsurfing sail, these sails are designed to be rigged on a mast with specific bend characteristics which are a function of the taper and stiffness of the mast. You will not be able to get the sail to set properly on a constant section Aluminium tube.

You may be able to reinforce the lower part of the windsurfing mast with aluminium tube. Ths is essentially what a mast extension does. With an unstayed rig the bottom section of the mast takes most of the load. By all means experiment but be careful as it may break depending upon the width and weight of your boat

Gonzo

Using shrouds does not affect the masts flexibility as it is still being supported in a manner similar to having a crew holding the boom.

In addition the mast is certainly not overstressed, the "strength" of a mast in compression is a function of length squared and the shrouds are set very low on the short mast.

Gareth

[gonzo]

Grob:
Shrouds affect the mast flexibility; that is what they do. How do you propose to attach shrouds and stays to the wishbone boom?

Gonzo,

Yes shrouds affect a masts stability, but the shroud set up that I have does not, as it mimics the resraints that a windsurfing mast normally sees.

The stays are not attached to the boom but to the mast in a position similar (though a little higher and closer to the sails center of effort) to where the boom is attached.

I have been in converstaion with a leading windsurfing rig manufacturer/designer who is supporting my design.

All the best

Gareth

[gonzo]

Windsurfer rigs produce a lot of lift because the head is to windward. The masts are very bendy which works well for that design. Why do you want to use that type of rig instead of one appropiate for your application? You have to buy a rig, so it is easier to get one that fits the boat directly. There are plenty of small production boats with rigs in the same price range.