questions about building a catamaran

Discussion in 'Boat Design' started by chevyman, Jul 3, 2012.

  1. Silver Raven
    Joined: Oct 2011
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    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Gooday 'chevy' - What have I missed here ??? - - Why can't you have -

    1/ A go fast

    2/ To sail around on

    3/ To go fishing off

    4/ Be comfortable on

    All those things - - - in 1 package ???

    I'm sure that - 'all those requirements' are not all that hard to come up with - if you just - take some time - - do some very lateral thinking & ask a lot of questions - then YOU make the final choice ! ! !

    Ciao, james
     
  2. chevyman
    Joined: Jul 2012
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    Location: Arizona

    chevyman Junior Member

    I have been trying to find something like that or to design something like that but frm what everybody is saying makes it seem impossible. I Would love to build a catamaran that has all that.
     
  3. Silver Raven
    Joined: Oct 2011
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    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    'chevy' - since when did you listen to this person 'everybody' & if so what did you learn from them - I'd suspect not much nor did much get done ! !

    You want to build a boat - so - O.K. - do it.

    1st/ get twice as much money put aside - as you think it will cost.

    2nd/ what was wrong with the first boat pic you 'posted' the link to ??? The hulls looked like they were fat enough to support sufficient weight to make the whole project very practical - lots of buoyancy is a must have.

    Looked alright to me. Judging by the fittings on the transoms - it had rudders fitted to the transoms & the hulls look like they were and/or could have been a sail boat - originally. With a 'sun-cover - I'd go fishing in/on that - quick as & with a simple sail & rudders fitted back on the transoms - I'd be both sailing & fishing - - quicker than - with the right comfy company - of course ! !

    3rd/ Keep the length as long as possible - cause the end result will be far better - an extra foot or two doesn't cost all that much more but will make for a much better boat in every way - higher, dryer, more floatation, smpoother, better weight carring capacity - just a 'win - win' all round.

    4th/ Go into 'craig-list - your local rag - 'trade a boat' or anywhere & see if you can find a set of hulls 24' long - or then maybe 20' long & lengthen them yourself. Keep the hulls as wide apart as you can ( the 20' x 10' Tornado sailing class - can be trailed - by lifting 1 hull up in the air - on the trailer) transported anywhere in any country. Use 4" diameter alloy cross-beams - raise them 4" up off the top of the decks of the hulls - - keep the floor light & stiff (like foam with glass or carbon & epoxy either side) but remember - you must keep it light - or the whole idea will not work well at all. Foam is best but ply is cheaper. Either way keep the 'core' thin & expxy/glass or carbon either side. Bend it all into the simplest shape that you want - glass it altogether - paint it - put some bean-bags on board - clamp a 9'9 hp or 15 hp on the back & go fishing. Don't forget the sangers & esky full of refreshments - bait - lines - hooks & sunscreen & away you go. It is really KISS - so go and do it. Want some verbal help - just ask. Ciao, james
     
  4. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Silver Raven,

    Much of what you said I agree with.
    But do you even know what the original boat was that he posted?
    Its a Tornado - see your 4th comment.

    Chevyman,

    The Tornado would be a great boat to use.
    They may be hard to find.
    If you have seen the video of the conversion you first posted, you will see that the transoms drag in the water badly, which will slow you down. I was surprised at the speed the builder of that boat stated he did, it was relatively slow - 15mph or so.
    If you convert a Tornado locate the solid deck farther forward, along with the motor.
    There is no possible reason to raise the deck beams on the Tornado up an additional 4" and no need to use anything other than the original beams.
    You can tilt up a Tornado to trailer, but the upper hull will be 10' up in the air, if you have that big fixed deck then add another 2-3 feet. Be seriously concerned with ripping something off by hitting trees or bridges, etc. And it is a serious chore to tilt up the boat and cradle.
    If you want to sail fast then you need to be able to take off the solid deck. If you want to act like sailing (slow) then just hang any short mast and little sail on the solid deck - you will just be trying to look cool, but you will be really slow. Keep the motor ready.

    If you want a tornado, but there aren't any available, the plans are available on the internet- this will be a plywood boat made of tortured ply.

    How many do you want on this boat? do you really need 24'?

    One last comment. When someone suggests some specific thing, ask yourself why. We all have our own biases, but it ought to make sense to YOU.

    Just do it I agree with, but check the cost, and only do what you really need.
     
  5. chevyman
    Joined: Jul 2012
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    Location: Arizona

    chevyman Junior Member

    Okay so some qeustions about designing this boat if i made it 25 foot how tall will the hulls have to be btwn 3 and 4 foot. I am thinking a daggerboard with a trunk. I want the actual wood look i dont want the color over it im not sure if that changes how i should do it or not. I am wonering if it would change the price much if i built it ply on frame or if i did strip planking. I will draw up a simple design and yall let me know what you think about what i should add or change cause im pretty sure yall will have alot more experience with that than me.
     
  6. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

  7. chevyman
    Joined: Jul 2012
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    Location: Arizona

    chevyman Junior Member

    Yes id be shooting for something exactly like that. Can you still get reasonable speed with a cabin in the centero r should i put small cabins in the hulls?

    I would like it to be able to go from a full beam down to a 8.5 foot beam so it can be pulled on a regular trailer and transported.
     
  8. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Less weight = more speed (with equal sail). Less cabin means less weight.

    Lots of boats have tried and failed. Copy someone who has succeeded

    Good luck.
     
  9. chevyman
    Joined: Jul 2012
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    Location: Arizona

    chevyman Junior Member

    Just me and another person maybe 3 or 4 on an occasion could i do around 18 to 20 feet just fine? Iam thinking I would like to do a big trampoline deck and have sme sleeping area and outher small things inside the hulls. How big would the dimensions be for a boat that is 18 feet and i could just make the beam 8.5 feet so there is no need for folding or dismantaling the boat.
     
  10. chevyman
    Joined: Jul 2012
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    Location: Arizona

    chevyman Junior Member

    For some basic dimensions would how does 18 feet long with a 10 ft beam sound. If i made the hulls 2 ana half or 3 feet wide would that be to wide for the length of the boat. I was thinking if i made the hulls 3 feet wide and put storage in one and a small bunk or cot type thing in the other that it would make it stable enough for bigger sails to help pull the weight of the bigger hulls.

    I dont have much experience with the sail stuff so what would be a good sail setup for what I want to use it for.
     

  11. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    You have placed go fast at the top of your list. A long skinny boat will be on your drawing board in that case. Divide the length of the waterline by the width of the hull. The ratio needs to be 10 to 1 at the very least. In that case 36 inch wide hulls will mean that you need 30+ feet of boat. For an 18 foot boat the hull would need to be restricted to 21 inches of width, preferably less. If you want to go fast under sail you will need to be thinking of trapezing, you will do everything you can to minimize weight, you will not have a rigid deck, and certainly no cabin structure. That is the general idea for a fast cat.

    Another thing that you need to be aware of. You must prepare to spend a very signifigant amount of money for a good suit of sails, mast, rigging, blocks, and lines. If you try to build your own sails you will not get the speed you hope for. Do yourself a favor. Find a Hobie 18 that needs a new home and you will go very fast and save money too.

    Now if you insist on speed, plus a fishing platform, a hard deck, and sleeping accomodations then forget sails and build a power cat. That would be a lot more practical to cover all your wants. A power cat can be 18 or 20 feet long, trailerable, have three foot wide hulls, a hard deck and all the rest of the stuff that you want........except sails. The power cat will go two to three times faster than the best sailing cat with only a modest pair of outboards. This option will get you to the fishing hole and back, quickly, even on very light air days. A sailboat will not. Take your choice.
     
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