pontoon that masquerades as a powercat -overview

Discussion in 'Boat Design' started by PirateTwig, Oct 11, 2016.

  1. PirateTwig
    Joined: Oct 2016
    Posts: 29
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Florida

    PirateTwig Junior Member

    Still really paranoid about over and/or under building the framework. So, how bad would the cost be to have a design done by one of you pro's? Basic idea is a floating primitive campsite with easy access in and out of the water. Hulls would need to have enough internal width (in an 8-10 ft length area) for an average size person to lay down with support to hang a parachute nylon hammock. Headroom doesnt have to be great. Its a bunk not a living room. :D Center section would be similar to a teardrop camper. Just enough room for two adults to lay down plus space for steering and self contained toilet. Bottom edge of connection beams should be high enough to allow me to duck and get under in a standard canoe. LOA between 16-22 ft, BOA 8'-8'3". Dual outboards, preferable nothing too big but would like to be able to hit somewhere around 20 knots, just enough to get somewhere in a decent time frame. I would likely fit a sliding beam structure under the center to enable it to open up to around 11-12 ft, not necessary to be designed at the moment (unless it wouldn't affect cost much) but I'm thinking that info will affect design. From what Ive seen custom designs start around 3k. I am hoping someone has a stock hull plan that could be easily narrowed to fit the bill for a price I can afford. I can design the center myself, if it will help design cost, my main concern is the hull design.
     
  2. sailhand
    Joined: Jan 2017
    Posts: 141
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    Location: australia

    sailhand Senior Member

    Google jarcat 6 they also do a motor cruiser 18 knots with a single 20 hp. All sailing gear from a beach cat and you save the cost of one motor. Heaps of them in australia and they go well. Forget the sliding beam thing its been tried heaps by some pretty good designers and none have been reall successful. For mine i would find an old farrier tramp and go sailing. Building sucks compared to sailing.!!!!!
     

  3. Barry
    Joined: Mar 2002
    Posts: 1,851
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    Barry Senior Member


    In your post you had welcomed any comments even if those might not agree to your current thoughts.

    First of all, you are not DESIGNING your cat. You are drawing a bunch of sketches and then taking them to the build stage.
    Certainly, many things have been built using this process. But as certain, quite a high percentage of them have ended up in the land fill sites or a fire pit due to poor performance.

    There have been many OP's who start down this path and come to the forum then looking for some design information.
    What shape of the hull should I use? What thickness of plywood? How to build the cross beam? What size of stringers and frames and glue and paint and horsepower and stability problems, and and and???

    It is an admirable trait to take a project on as you are doing. And many boats have been built using this process.

    But there are so many items within the DESIGN section, between conceptual sketches to a SUCCESSFUL build, that
    it is a safety issue to bypass this most important section and then ask opinions assuming that you will get ALL the answers that will meet the requirement of a proper design process.
    The design process is complex, your families lives could depend on a proper result.

    Your goals were to have a cat that you could build, which it appears that you have the ability, to enjoy boating.

    You want to do it inexpensively and perhaps want the satisfaction of building your boat.

    You will spend a considerable amount of time in the build, hopefully most of it fun and you will spend a considerable amount of money on the materials.

    Why try to save $500- $1,000 bucks by not buying a set of plans from a proven DESIGNER, where the profiles, beams, frames, stringers, buoyancy calculations, and proven build processes etc etc have already been proven?

    If you spend a bunch of time and money on your boat and find it does not work properly or breaks apart or has no resale value when you want to move from a 20 footer to a 25 footer, the $500-$1,000 saved by not buying plans will seem a bad choice.

    If you have been reading the threads on this site you will see many topics regarding developable surfaces. This is a surface that a plywood sheet (or aluminum or steel) will bend smoothly. Ie you can not significantly bend a sheet of ply in two directions.

    When I look at your pictures in the bow, it does not appear that plywood would attach to the keel to chine and the center stringers. It could be the perspective given by the fish eye effect of a camera lens.

    So if you go to all the work and expense to build the frame-stringer skeleton in your hulls and then find that the plywood will not make contact with all of your stringers, you could have a mess on your hands. Or a poor quality build.

    But it appears that you want some freedom to change the internal locations of staterooms, bunks etc.
    You want certain things. If the weight and locations are not too significantly different than what was originally designed into a set of purchased plans, you can expect good performance but more importantly you can probably expect that the boat will not come apart if you get caught in a storm.

    How important is the safety of your family?

    And in this post, you are now asking as to the cost of actually designing a one off boat where all the design cost (well most of it) will have to paid for with this one boat. When you buy a set of plans from a qualified designer-plan marketer, the design -build process is amortized over many boats saving you a bunch of money.
     
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