Multi-masted sailing cats

[Chris Ostlind]

I've done a boat with a twin masted setup... a trimaran, and she is a really sweet machine for handling, as well as a good turn of speed. As mentioned, there are all sorts of reefing and boat balance options available to rig design of this type.

I liked it right away because it let me lower the COE quite a bit compared to a single, taller rig. This, in turn, gave me loads of options to design a set of very lightweight amas and lighter weight aka tubes. The masts, themselves, could then become self supporting, rather than further complicate the design with shrouds, stays and all the hard points to support same. It also removes the compression problems to a large degree, allowing for a lighter hull structure.

Overall, for the design of the XCR trimaran, the twin rigs and all that came with them, were a very favorable design strategy. I'm using the concept on several of my trimaran designs and plan to use this rig format on a cat, or two, in the very near future.

Video Clip here:
http://www.youtube.com/watch?v=2eEou...e=channel_page

[robherc]

Nice boat Chris...looks great in motion...pretty quick too. Good Work :-)

[ancient kayaker]

I notice the masts are in tandem, and they look identical. There is an advantage to having them the same, economy of scale, reduced spares, identical rigging.

Chris, what is the sail material?

[Chris Ostlind]

All the above, AK.

Beyond those important issues, I also use the same sail on about a dozen other designs. If the homebuilder chooses to build another boat from my portfolio, then there is a good chance that he will not have to buy another complete rig. This process enhances the savings and makes the sail inventory that much easier to manage.

The sails are built in Dacron. This set was made by Stuart Hopkins who goes by the loft name of Dabbler Sails. http://www.dabblersails.com/index.html

Stuart makes terrific sails that are beautifully made with a high degree of attention to detail.

[Fanie]

I have some objections to that rig. No place to put a fish in I can see you leave (tough choice ?) your buddy (or wife ) to take the fish out. If the bar is closed you go back for either.

[robherc]

Originally Posted by Fanie

No place to put a fish in

Hmm...that could be easily enough to remedy...just design a fish/bait well to hang on the ama arms (better make that two) on either side (to keep things balanced). Then they're removable when you're looking for all-out performance, and easily re-installable when you want to get some fishing in

[Fanie]

He he... I can see you Texans aren't used to fish. You hang it somewhere and guaranteed the biggest shark in that area will make it his business to relieve you of it. It's a bit like our residential living here in SA

Chris, those sails, one in each ama's, could free some hull space up... Any drawbacks to using it like that ?

[robherc]

I didn't say to make the bins clear...I doubt the shark'll be able to sense them inside an opaque tub with sonar (though I guess that still leaves dolphins as a concern )
Of course, with my luck, right about the time I put a trophy fish in one of 'em...I'd get hit by a whale or somethin' ... knock the bin into the water, and send me home with no fish except for the ones in my story...rofl

[Fanie]

Sounds like the normal kind of thing to happen. Whales are nothing, it's those giant squids that worries me.




Chris, those sails, one in each ama's, could free some hull space up... Any drawbacks to using it like that ?

[brian eiland]

I was looking for some other items on my computer and ran across these two photos

[oldsailor7]

Brian.
The only reason I can think of as an advantage on that Trimaran is the fact that the mizzen sail enables the boat to balance, given the very forward position of the mainmast.

There is nothing wrong with that.

It enables the accomodations to be expansive in the middle of the boat, and trimming of the helm is easily done by adjusting the mizzen.
As a result it is probably a very nice cruising boat.

If they really wanted "Performance" as well, all they have to do is put a furling jib on a bowsprit.

[ancient kayaker]

Oldsailor, you mentioned balance first and then went on to suggest adding a jib.

That prompted me to wonder how the jib would effect the balance. Does the CE remain more or less in the same place when the jib is raised (I haven't sailed with a jib so I never had the chance to find out for myself)? Or does it move forward as seems intuitive?

I ask the question as, from reading another thread, there seems to be some uncertainty when establishing the effective CE of a rig; it seems clear that it has only a loose connection to the center of area.

[robherc]

To get a "true" CE you'd have to figure the area of each sail, the center of area of each sail, and the actual effort (i.e. beam windage) being exerted on each sail. Figure these all together & you can find the CE which, consequently, can and WILL move about the boat a bit at different angles of trim.

With that in mind, if you fly a jib that is fairly small, relative to the main/mizzen, and you fly it with a bit more luff (did I get the right word there?), then it'd make a very minimal difference to your CE, while still giving you a bit more forward power, at least when reaching/running. A genoa would DEFINITELY unbalance that sailplan though...lol

[robherc]

So I guess it really boils down to how tightly you sheet in the Jib. Tight sheet = moves CE fore; loose sheet = moves CE aft.

[jamez]

The sail plans for the Newick designed Spark and White Wings (post 40) both show a wire-luffed headsail that can double as a mizzen staysail. White Wings has 2/3rds the displacement of an F36. The newick Lungstrom ketch rig is a no bones cruising rig but the way DN designs his boats they almost can't help but be quick. A sloop rigged Echo would probably be quicker than WW to windward but cruising down wind without extras I suspect there wouldn;t be much in it.