Catamaran from two single hull boats

[nimblemotors]

I've been looking into buying another sailboat, this time for blue water sailing, and I want a cat for the room, but the big ones are rather expensive (wait, let me rephrase that, VERY EXPENSIVE)

So I've got this idea to take two single hull sailboats and create a cat from them. This is proabably a common dumb idea, but I didn't see anything in my searches that popped up, so maybe its soo dumb nobody even asks.

Are the hulls of a cat vastly different than a single hull sailboat?
I'm thinking like 30ft cal or something, these come up for sale really cheap, so a couple of them and a lot of work, and I'm thinking I can build a big comfy cat that isn't embarrasing for $20k.

Please tell me how this won't work.

[Corley]

This is a common question and easily answered the negatives are to do with the structure and shape of the hulls a monohull sailing boat is quite fat at the waterline this equals a lot of drag one hull works ok but put two of them immersed in the water together and you have a very draggy combination and the performance will be abysmal.

Another consideration is the structure the gunnels on a monohull are not geared towards absorbing the stresses that beams place in those areas as most of the strength is focussed towards the keel this means a lot of reinforcement to the gunnels plus you still suffer the parasitic weight of the structure where the keel used to attach.

I have seen some conversions of monohulls to a trimaran format which offer reasonable performance normally though they would start with a very narrow monohull like a soling but you still suffer a lack of room in the hulls and they are not up to scratch compared to the performance offered by a properly designed tri.

[nimblemotors]

Kinda figured that was the answer, as the cats performance really comes from the two smaller hulls. But has anyone actually built one this caveman way? I really don't mind if its slow, I'll be in no hurry to get anywhere, but if takes a huge breeze just to move, that ain't no good.

Originally Posted by Corley

This is a common question and easily answered the negatives are to do with the structure and shape of the hulls a monohull sailing boat is quite fat at the waterline this equals a lot of drag one hull works ok but put two of them immersed in the water together and you have a very draggy combination and the performance will be abysmal.

Another consideration is the structure the gunnels on a monohull are not geared towards absorbing the stresses that beams place in those areas as most of the strength is focussed towards the keel this means a lot of reinforcement to the gunnels plus you still suffer the parasitic weight of the structure where the keel used to attach.

I have seen some conversions of monohulls to a trimaran format which offer reasonable performance normally though they would start with a very narrow monohull like a soling but you still suffer a lack of room in the hulls and they are not up to scratch compared to the performance offered by a properly designed tri.

[gonzo]

It is possible. However, if you are planning on blue water sailing, not advisable. Catamarans need narrow hulls or the stresses are enormous. In protected waters and good weather it could be done successfully.

[Frosty]

Boy do I know how you feel , I love making stuff that people say you cant do.

What about taking a sail boat hull, cut in half down the length and glass in a flat side.

You would then have 2 cat hulls, would that satisfy the nay sayers?

[nimblemotors]

Originally Posted by Frosty

Boy do I know how you feel , I love making stuff that people say you cant do.

What about taking a sail boat hull, cut in half down the length and glass in a flat side.

You would then have 2 cat hulls, would that satisfy the nay sayers?[/quote]

indeed. i like to take risks, but don't really want my boat to fall apart 100's of miles from nowhere. It seems making the cat hulls would not actually add much cost considering how much else needs to be built.
I could build some small scale tests, start with r/c boats maybe, or 17ft boats?

I'm convinced I want a cat, so somehow I need to make it happen under $50k, and it looks like $100-200k is what I need for even a used one capable of blue water. building one from scratch is too expensive in both time and money, unless I can find an unfinished project.

[nimblemotors]

are you aware of anyone that has done it? i'd love to see the pics.
i really wanted to photoshop a couple of sailboats lashed together with an RV on top to get some laughs..

Originally Posted by gonzo

It is possible. However, if you are planning on blue water sailing, not advisable. Catamarans need narrow hulls or the stresses are enormous. In protected waters and good weather it could be done successfully.

[CatBuilder]

Nimble, there are a lot of unfinished projects to be had, or you can start a build from scratch.

There is another part to this idea of yours: Money.

Do you want to get your $50K back later, or not? If create some kind of monohull-based catamaran, you can kiss the $50K goodbye entirely, since nobody will buy it later.

If you go and build a real catamaran or take over a build that has failed, you can at least get whatever money you put into it back out of it.

[CatBuilder]

Also, look at the Catalac 10M. It's about $90K, but some are less that need work. Reasonable boat for cruising. Some have crossed the Atlantic. It's probably the best catamaran under $100K you can find.

Check out the US website on them:

catamaransite.com

Also, up in San Fran, there is a big, old wood/epoxy catamaran that needs tons of work they are trying to get rid of. They are asking too much, but maybe by now the dock fees have hurt them enough they'll take a realistic offer.

Also, I know of a set of Chris White Atlantic 57 hulls (overpriced) and two pairs of Kurt Hughes hulls - one pair in CA (out in the weather in San Diego) and a pair in Long Island.

[Corley]

It's not a matter of cant be done it's a matter of what will you end up with, say you grab your two cal 30's which are currently a reasonable sailing boat and perform their sailing function quite well now you spend a packet of money engineering and building beams to hold the two boats together you produce a catamaran that doesnt sail well and will be unsafe in bluewater conditions and has a resale value of nil so really all that money is wasted and you end up with a boat that has poor resale value and is hard to sell.

Remember anything to do with boats will cost you money there is no sense wasting it on false starts and believe me if designers could make successful catamarans by sticking two monohulls together they would because it would save them a lot of time and effort researching hull shapes and the compromises that come with them and the world would be full of catamarans.

I dont want to piss on your idea but sometimes a wakeup call is worthwhile to take onboard I hate to see people waste their hard earned on projects that will not return the desired result. All they end up with is a lot of heartache and a useless boat that ends up sitting on a hardstand with a for sale sticker on it.

On a positive note have you considered a wharram catamaran very basic but seaworthy and may fit your budget.

[Petros]

Taking a mono hull and making into a tri is not a bad idea. Put on a larger sailing rig and than build out the side decks you would get the same amount of deck room at least.

The idea of making a cat out of two monohulls is just too unrealistic to even consider, way too many problems not to mention a waste of time and money. If you are not worried about speed, than why not just buy a large monohull?

You also might consider searching for foreclosures and salvaged hulls, in addition to incomplete cat projects. check the local marina offices and boat yards.

[rberrey]

for 50k you can build a tri in the low 30' range

[Sand crab]

Generally a 30' cat is too small for blue water cruising. The Catalac 10M is still a bit on the small side. The highly succesful Gemini 105mc is about this size and they specifically do not call their own boat a blue water cruiser. Most people consider about 36' to 40' the minimum size for true blue water cats. You need a larger size to get rid of the low bridgedeck pounding. The Catalac and the Gemini both suffer from this.

[nimblemotors]

actually I don't care to loose the $50k on resale since the plan is to die in this boat eventually, of natural causes, not boat failure.
I would hope to build the ghetto cat for $20k, so the loss not nearly as much, specially compared to what I'd have to pay to get a good one in the end ($150k) I get it that its a bad idea. I've looked for unfinished projects, hasn't seen much resembling anything affordable. There just are not older cats to fixup, they are too new, at least the good ones.

My woman will not put up with a monohull, to get enough room and stability its too big to single-hand, so as much as I'd want to go that route and get an older one with my $50k, ain't gonna happen.

I appreciate the feedback.

Originally Posted by CatBuilder

Nimble, there are a lot of unfinished projects to be had, or you can start a build from scratch.

There is another part to this idea of yours: Money.

Do you want to get your $50K back later, or not? If create some kind of monohull-based catamaran, you can kiss the $50K goodbye entirely, since nobody will buy it later.

If you go and build a real catamaran or take over a build that has failed, you can at least get whatever money you put into it back out of it.

[Sand crab]

Catbuilder, Is there a web page that I can look at the Atlantic hulls and the Kurt Hughes in New york. I've seen the one in SD. Thanx BOB