Modern Gunter rig

[catsketcher]

Hello all,

I am currently building the second trailerable catamaran of my design. I took the first one to a regatta for a look and was intrigued at some of the things I saw. Many designs took quite a few people and quite a long time to get the masts up.

Although to be fair there were some boats that got masts up and rigged in less than 40 minutes a few had skippers who were scared of their boats. Then when I was unrigging the little 5.9 metre cat the person who is set to build the second of the 7 metre design said " I wish the 7's mast would be that easy to raise and lower." The prototype Cats-paw has a 16ft skiff rig - 9.1 metres tall 80mm diameter x1.6mm wall section. It has a mass if 1.2 kg/m.

That means that it needs 9.1/2 x 1.2 x 9.1 = 50kgm of torque to raise or lower at worst case (when the mast is on the deck) I find this pretty easy to raise.

The 7 metre cat has a 10 metre mast and the mast manufacturer wants a 3kg/m mast section. This makes the section 30kg without spreaders etc. To raise this will take 150kgm torque. 3 times more than Cats-paw.

However if I cut the mast off at the hounds (it is a 3/4 rig) the mast length is 7.5m, weight is 22.5 kg and moment is 84kgm. This is 56% of the tall mast option and means that a person has to lift 28kg 3 metres back from the mast base to lift the mast as opposed to 50 kg for the tall rig.

Now the racers had tall masts and lots of men rigging them. There was an absolute dearth of children and women. I want my boat to be a family boat and so rigging must be easy. A friend said his definition of a trailer sailer is a boat you can push off a trailer and lift the mast up on. I could use power winches and gin poles but want to reduce loads both real and implied.

So I thought about a modern gunter rig. With carbon tube becoming so high quality with sailboards etc I could use a laser style topmast with a sleeved sail over a carbon tube that slides up on RCB batt slides for headboards. The topmast would be shorter than the boom and would require a quick release pin on the top batt slide to drop the topmast down. I could also get a quite bendy topmast for good mono style gust response. If there is enough bend then I could get away from full battens (to save money) but then again full battens are very nice.

Has anyone tried anything like this? I know of the PT 15 http://www.nwboatschool.org/news/ designed by Paul Bieker but has anyone done this on a modern trailer sailer over 6 metres?

cheers

Phil Thompson

[bhnautika]

Catsketcher this idea has been around for a long time and I think it has merit. It sometimes known as a sliding Gunter rig, there’s a number of articles on them around. A nice flexible curved yard with bat wing battens on cars seems good to me. I had a good look at it about ten years ago but never got around to testing it.

[fhrussell]

Awhile back, Wooden Boat Mag had an article on some racing boats that used a sliding Gunter rig. I think they were two Herreshoff designs....(?) They were certainly over 6 meters if not very close in length. I'll see if I can find the issue...
I am thinking about doing the same kind of rig for a 24' catamaran design I have been working on. My parameters are the same,....a rig one can single-handedly raise and lower from a trailer......
I really like the PT design with the track that the yard slides along to reduce the leeward head rotation.

Hey Phil, Any drawings you can post??

[CT 249]

fhr, if you're after catsketcher you'll have to wait; he's not ignoring you, he's trekking or camping in the bush.

This rig has been used on models because it doesn't require full length battens. One version has been tested on a fullsize boat back in 1976 and will be used on my new 18. One major advantage is the upper outhaul.Gives the planform and gust responce advantages of a squaretop rig with more control of sail shape.
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