Wide-hulled trimaran?

The Robert Harris designed Zipper is similar to what you seem to be asking about, Bob has a swing-beam version of this boat called the Swinger, with a docking beam of 12'

 

planning/displacement motorsailing trimaran

This sounds similar to a concept that I've been wondering about. Maybe you could comment on it: a motorsailer based on a trimaran with a planing hull and with long, narrow deep amas mounted so that the two amas deliver much (maybe most?) of the buoyancy of the boat. I wonder if it could be designed so that at speed (whether sailing or motorized), the boat would essentially turn into a catamaran with the center hull out of the water or barely skimming it. Maybe you could even put lifting foils on the amas to make them lift better.

Here are the characteristics that I would expect (keeping in mind that I'm not a boat engineer...):

In comparison to a sailboat of the same size, it would give you the option of going fast when you want to get somewhere.

In comparison to a displacement sailboat, it would sail faster, would not heel, and would have better interior room. It might not have as much load-carrying capacity, especially after adding the large engine and fuel tank.

In comparison to a power boat of the same size, it would be able to sail so you could have fun on the water and make headway without pouring dollars down the drain, although it may not have as much top speed.

In comparison to a power boat with a flat planing hull, it would have better stability at rest and be easier to maneuver in close quarters when there is wind. It may be less efficient at speed.

In comparison to a deep planing hull it may be more efficient at speed --or maybe not, but it would sure be a lot more efficient at sailing.

Any thoughts?

 

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Sounds like it could be worth some serious investigation. I have spent zero time in the last thirty years looking at cruising multihulls but lots of time designing, building and sailing small tris and a few cats. There are a lot of considerations that would be worth asking an experienced cruising multihull designer about. I think that there may be some interest in the "MacGregor 26"
of multihulls but not for me-but it might be able to work....

 

Tad,
Yes, Zipper and Swinger are starting to look interesting. Do you have further specifications on these tris? How did they sail? Plans? Is Harris still alive -- designing?

 

Looks like plans are still available.
http://vanyacht.com/home.html

Also Robert B Harris wrote an informative book 'Racing and Cruising Trimarans' back in 1970. Has a good analysis of types available then, including a number examples of wide bodied tri's from other designers such as Norm Cross. Worth a look IMO if you are contemplating such a design.

As an example there is a 11 metre (35 foot) demountable Harris for sale here. Looks a nice boat.
http://www.trademe.co.nz/Trade-Me-M...sail-boats/Moored-boats/auction-368317995.htm

 

There is an aft version (Swinger style) of the Harris 38 currently listed on ebay.......she's sitting ashore at Walter Greene's in Maine.......

http://cgi.ebay.com/ebaymotors/38-x-24-Trimaran-/110675803004?pt=Sailboats&hash=item19c4cabb7c

 

You could dig out your Vagabond plans. The Cavalier was rated at an enormous 3500lb -4000lbs payload. It had increased sheer on the main hulls and amas to compensate for the deeper immersion. The scantlings would need to be heavier but it would be faster than what your proposing with a softer ride. The yawl rig looks better than the ketch, though of course the sloop is faster.

 

http://au.yachtworld.com/core/listi...access=Public&listing_id=51350&url=&imc=pg-fs

 

Jamez,
Thanks for the link to VanYacht and the Harris book title. I'm trying to contact VanYacht and have bought Harris' book.

Tad,
You must be familiar with this particular boat as I don't see any description in the advertisement suggesting it is the Swinger style. From the single deck photo I don't understand how the beams swing? Could you explain how they fold?


Cavalier,
How does the Cavalier differ from the Vagabond? I understand it is a foot longer. What else? Is it demountable? If you had any details on the Cavalier that you could post that would be great.

 

The Cavalier and Vagabond MK2 are the same design length at 36'. My vagabond is a foot longer with a more raked mainstem. The boats are basically the same except for the Cavalier having 6"-10" more freeboard with the same wing section raised with the sheer. This gave higher underwing clearance allowing more payload, D.H. Clark actually published a figure of about 4500lbs taken from the Nicol people. The cabins are a little lower as you can see in the Hedley Nicol plan thread. Some one posted a picture of a demountable Cavalier awhile back so it could be done but would have to be engineered. The scantlings should be stronger especially at the ama wing joint where a couple of the cavaliers had problems way back when, most however didn't have any problems. The keels were a little shallower because the loaded hulls rode deeper but the rigs and options are all the same. These are pictures of a ketch for sale in Texas.

 

Below is the Swinger arrangement.....This is a tiny scan from Tracks On The Water, Bob's 2008 Autobiography.......

Obvious differences between Zipper and Swinger are the arrangement, aft cabin for Swinger vs aft cockpit for Zipper, and stub keel with centerboard (?) for Swinger vs centerboard/daggerboard for Zipper.......

Mentioning the boat listed above is "Swinger Style", I meant she is a center cockpit/aft cabin version of the wide body 38' Harris tri.......that's all......

 

Hi Tad, do you have a source for the Harris autobiography? I'd like to get a copy but can't find it on Amazon or our local marine book shop.

 

Tracks On The Water is self published by Bob, try the VanYacht site or you can write to Bob at

Robert Harris
795 Sawyers Lane
Vancouver BC
Canada
V5Z 3Z8

Also the book does have an ISBN number 987-1-897518-81-6, which may help your local bookshop order it....I don't know how these things work.......

The book is a little jewel....my main wish is that there were more drawings printed in a larger format......Bob does not realize how important his work is as reference material.......There are some good stories as well........

 

I'm still thinking about wide-bodied trimaran hulls. I found this trimaran design by Len Surtees, with a length of 38' and the main hull waterline width looks to be maybe 6'. Payload 4000lbs. Much closer to what I'm looking for than anything else. Would just need to make it demountable.

Does anyone know what its sailing characteristics are? Apparently Osprey was purchased by Tristan Jones, renamed Outward Leg, and sailed across the Atlantic and through various rivers in Europe. Has anyone read Jones' books concerning this voyage?

http://www.surteesmultihulls.com/11m-re-rightable-trimaran

As shown in the photo below, Surtees initially launched Osprey upside-down, then self-righted it, just to prove that it could be done.

 

Have you looked at this thread? The main hull is fairly wide and they claim it is a planing hull. Just launched...... http://www.boatdesign.net/forums/multihulls/new-sail-tnt-34-a-31643.html