Reasonably seaworthy cruising powercat conversion

Discussion in 'Boat Design' started by svmegatron, Feb 11, 2012.

  1. Richard Woods
    Joined: Jun 2006
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    Location: Back full time in the UK

    Richard Woods Woods Designs

    Well you asked....

    What a difference a week makes. Last Friday we took the Skoota 28 hulls down to the boatyard in the snow

    On Monday we had the central cabin delivered by someone who normally transports cars "never mind that its 13ft wide and I don't have a wide load permit, its only 38 miles" That sort of a guy. Actually he was very professional and efficient. The cabin was craned onto the waiting hulls, by which time we were in T shirts and the air temp was 68F (20C)

    Then we had three days doing some final jobs

    Thursday dawned wet but by 1.30pm, launch time, the sun had come out and the temperature soared.

    Quite a crowd came down to see the launch. Fortunately it floated on its marks (well actually well above, however there are no cruising stores on board yet, just tools)

    Then Josh, Dan and I went out for a trial. The engines are brand new, so really we should have stayed at tick over speeds for the first two hours. But of course we all wanted to know how it performed so for a few minutes we opened it up

    I was very pleased to find that we did 15 knots with twin 20hp Tohatsu outboards and 10 knots using just one.

    We will trial it a bit more next week, then we take it up to Canada for the summer

    Photos and videos will be posted shortly

    Richard Woods of Woods Designs
  2. Rafael Francke
    Joined: Apr 2012
    Posts: 8
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    Location: Camarillo California

    Rafael Francke

    Nice job

    Congratulation, 15 knts with twin 20hp is very nice, that translate to a very nice lean hull shape and light boat. :D
  3. Eco Cat
    Joined: Jan 2014
    Posts: 12
    Likes: 2, Points: 13, Legacy Rep: 15
    Location: United States

    Eco Cat ECO Cat

    Converting a Sailing Catamaran to a Eco Cat power.

    Glad to see that I am not the only one thinking about this.
    I am building one right now 2014.
    Just got on this site and saw that you are considering converting a sailing catamaran to a power cat. I think your crazy, but you might be on to some thing. I have considered it for many years, I am tried of running these gas guzzling old boats. I know because my Wellcraft Nova III 27’ that burns 13 gals and hour cruising at 25 knots and 28 gals at 70 mph, she weighs 6000 lbs. and drafts 30” so taking the family to the beaches around us is out of the question . She’s a fine boat and we have enjoyed it for the last 20 years and she still turns heads today . She will be for sail in the spring of 2014.
    I am looking for is a super economical Catamaran as well that is light weight and can be powered, I am not out to break speed records just need to do around 20+ mph is fine with a good cruising range. The Boat needs to be stable enough to cruise the inland waters of the east coast from Va. to Florida . Long enough to cut through some rough water, wide enough to be stable. I want a shallow draft 12” is fine so I can get to any beach I choose to and don’t have to wait on the tide to rise if and when I run aground. I want it to look sharp unlike some of the small power cats, most of them look like boxers or snub noses and not very sleek. I want it to burn around 1 to 2 gals and hour so it won’t break the bank. I need cabin space to get the passengers out of the weather or to sleep in over night , with a toilet area and sink area with storage of supplies . Maybe the boat MFG’s will take note to revitalize there business.
    I have been considering the same thing for the past 8 years and looking around and researching as much as I can to find what would suit my needs and budget and not take forever to do the project. I agree to build the hulls is way out side of my ability's and time frame and budget I don’t want to have to re-invent the right hull , I want to by one that has track time and is proven in the water.
    Yes I agree that most conversion don't turn out very good looking but give them credit they tried.
    The Right Track - I noticed that one of the shots that where posted to you were of a Diving cat that I to looked into and used as a bases to consider building one. The dive cats are built in Florida and are about 30' long and 18’ wide and can hold around 20 people and yet will draft only 12"to 16”. They use twin 90 hp motors and can run around 20 to 25 knots if my memory serves me right. They cost around 90k which is way out of the budget here. With no cabin or protection from the weather. But are noted for fuel economy of around 4 gals and can deliver divers to the islands for diving.
    Everybody's right that most sailing hulls aren't made for high speed above 12 knots. But there are many sailing cats that hit 20 to 22 knots and one that I considered was a Sea Wind or Reynolds because of cost and availability, it was approx 22' to 24' not sure. ( Its the third picture at bottom).But not as fast but inside was finished very nice for comfort and room and it look better good as well .
    On my creek there is a McGregor Sail Boat 25' mono hull , a couple a years ago as I was cruising out of the creek here I saw this thing flying in with white water splash from the hull and moving around 20 to 25 knots with the mast leaning into the turn. I did some research on it and talked to the owner directly to find out more. He said that with a Honda 50 hp fuel injected motor wide open he would be burning around 1 1/2 gals an hour doing 20 knots, he could also pull a skier behind but it would burn more. So I looked into that one and saw that it was extremely light weight . If you can afford a 36' McGregor Catamaran that would be the best for sure, just because of length and size for cruising. It was a bit outside of my budget and dock size, but what a cat. So I know it can be done.
    It was suggested to me 5 years ago to start to look into the Stiletto 27' Cats because of the size and buoyancy of the craft and that it could hold up to 8 to 10 people . I did and as I read up on them I discovered that they have sailed up to 26 knots max speed. But yet under power as noted in some threads from owners was that with a 15 hp they could power cruise around 12 to 15 knots. The Hulls have a very unique look and are wide open inside . These hulls are built from Nomex Honey cone materials with epoxy just like our most of our advance fighters such as the F-22s and some of the most efficient air craft of today jet liners. The total weight of a Stiletto is 1200 lbs and the hulls are 3'+ wide and 4' + or - tall.
    My Concept Idea is this if you could find a nice set of perfect hulls that are sea worthy from the get go why couldn't you take the top half of a curved windshield small power boat of about 20' or less and cut off the weight of the bottom half and drop the top half on to the hull supports of the catamaran and make up a bottom pan to deflect the water between the hulls. Make up a motor mount for a 50 to 75 hp Suzuki so that the thrust would be sent through the top half of power boat hull and be distributed equally to the main support tubes of the catamaran hull and support the weight of the cockpit evenly across the support tubes. This would give you all the cockpit finishes with out and work or expense.
    Stilettos where my choice but they are very expensive and rare to find under $10k most are 20k and some are $30k all of which is out of side of what I the project would allow.
    I gave up trying to find a set of hulls cheap, I decided just to build a scale model of the my Idea so I went the Wildjib site to get some specs and I thought I would just check the for sale ads on Wildjib and I couldn’t believe there was on the site within my range so I made the deal quickly and before it snowed, its in my yard now .
    Got It - My Plan is moving forward and I am about to set the top half of the power boat on the cat and fit it up in the next couple of weeks once this Polar Vortex leaves us here in Va. I am now running the weight and balance on the hulls to see how far forward it should sit. The top half is perfect fit to the catamaran in between the hulls. Then to the fiberglass shop to have the bottom half made, and the slot plug made.

    Attached Files:

    Last edited: Oct 26, 2016
    1 person likes this.
  4. Rafael Francke
    Joined: Apr 2012
    Posts: 8
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    Location: Camarillo California

    Rafael Francke

    MacGregor power Cat + sailing

    Here is a link to a MacGregor convertion.
    It is a Power Cat with option for Aux, sailing [ Bi-Plane rig]
    The boat is trail-able, trailer to water 15 min.
    cruising 15-18 MPH about 3 mpg. :eek:
  5. Eco Cat
    Joined: Jan 2014
    Posts: 12
    Likes: 2, Points: 13, Legacy Rep: 15
    Location: United States

    Eco Cat ECO Cat

    Thanks Rafael
    I had not seen this one until now but that is the general Idea. I had seen another one that is on youtube that also folds up with scissor action. No center cabin or seating area. I will send you a shot of what I am attempting to do.

    Dave C

    Joined: Nov 2014
    Posts: 1
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    Location: FL

    GLFSTRM New Member

    Eco Cat,
    I'm considering attempting a project much like what you're in the middle of. What's transpired since your last post?
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