DIY Simple Catamaran Sailboat Design

Discussion in 'Boat Design' started by WilliamPrince, Oct 10, 2013.

  1. bregalad
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    bregalad Senior Member

  2. Skyak
    Joined: Jul 2012
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    Skyak Senior Member

    William,
    your provision and plan are much lighter and simpler than they were yesterday. The canoe or canoe with outrigger would do. You don't have the weight and density of supplies I was concerned about and you are NOT looking at long passages in the pacific with no shelter and no ports to hide in. I am wondering, is your plan still to go to Costa Rica but by bike rather than boat? Isn't there a ferry available? Would you like to sail farther south as long as the sailing is safe and easy? The bike is bulky and cumbersome but no problem.

    I don't see a way to cook and I don't see the safety and navigation items an extended cruise would take. The thing I was looking for was a battery, anchor, and other dense heavy stuff that would push the design toward monohull. We can talk more about safety items but if you are firm in traveling light and not doing long pacific sail all the way to Costa Rica the outrigger canoe is your fast easy design. I think a $60 waterproof hand held gps and waterproof handheld VHF would be worthwhile purchases good for land and water.

    I was wrong about acetone for amine blush. Water is used to remove blush, acetone is for oils and other contaminants. I still go by the rule that if you want something to stick to a surface it should not be shiny.
     
  3. Skyak
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    Skyak Senior Member

  4. El_Guero

    El_Guero Previous Member

    I didn't like the canoe they used, but their 'Cruising Rowboat' is a mix between a wherry and a micro cabin cruiser.

    Their 'expedition' sets really high in the bow, or at least seems to in their pictures.
     
  5. WilliamPrince
    Joined: Oct 2013
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    WilliamPrince Junior Member

    Good news all, I have found a workshop which I think is suitable for my job!
    [​IMG]
    It is kind of a mess, and I spent all of yesterday cleaning it out, and I will spend much of today the same way... I have a question before I buy wood, probaby later today...

    What do you guys think of skin-on-frame construction? I saw a little canoe which had been built with that method and I was considering it... But maybe it is not sturdy enough for my needs, or too difficult for an amateur.

    Also, there is an old boat out back in the place I will be building, with a bent mast.
    [​IMG]
    Is this thing too bent to use? Is there a way I could fix that? It seems to me like a pretty nice aluminum mast, very light, pretty tall. Will get the real dimensions later today.
     
    Last edited: Oct 19, 2013
  6. El_Guero

    El_Guero Previous Member

    Not seeing the images.
     
  7. SamSam
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    SamSam Senior Member

    No images.
     
  8. El_Guero

    El_Guero Previous Member

    SOF is strong 'enough' when you use a strong skin.

    Polyester covered with resin is strong enough. My only concern would be your changing construction method in midstream - unless you have been thinking about building this way, it is a little different.

    SOF is quick, strong, lighter, and actually easier than plywood. But, it is slightly different.

    Our user 'Upchurchmr' has built using SOF. The method he used draped the cloth over the bottom, and then glued the cloth into a notch cut in the gunwale. Using gorilla glue or a comparable water proof glue makes a permanent contact point. Do not over cut the notch. And you can lay the deck using the same method into the same notch, if the notch is big enough. Cutting the notch too deep or wide risks the wood splitting there.

    I think it is nylon that needs to be wetted, stretched, and allowed to dry on the frame.

    Take 'air' bags with you no matter what you build.
     
  9. WilliamPrince
    Joined: Oct 2013
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    WilliamPrince Junior Member

    Okay, I have bought some lumber. 3 sheets 4x8 1/4 inch birch plywood, 8 16ft long, 25mm x 40mm (cut those myself from larger wood), 2 16ft 2x4s and 1 8ft 2x4. Also the lumber yard had a bunch of very fine sawdust laying around, so I got about a pound of it. Can I use this as filler for my epoxy? I read somewhere that sawdust was filler... Does it need to be super fine? Mine isnt that fine.. But not huge.

    Anyways, I am thinking about building the 14ft canoe in the free plans on Bateau, as a practice.. Would this canoe design be a good basis for my pontoons/canoe on my boat? I am considering an outrigger canoe as well recently, as it would be much easier to build and potentially a better vessel anyways... I would build a deeper V than the Bateau canoe, more like the Flaquita, and a deeper boat in general, so I wont get swamped with a single wave.

    And Sky, as to my plans... Yes I plan to sail as far south as the sailing is good, then get off and continue on my bicycle. I think you are right about the GPS and I am looking into purchasing a good one.
     
    Last edited: Oct 19, 2013
  10. Skyak
    Joined: Jul 2012
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    Skyak Senior Member


    William,
    you are making progress. About skin on frame -it has the attributes noted but I don't think it is right for you because it flexes too much when you try to put a sail on it and it is not tough for dragging up the beach with a load. We can consider SOF for the outrigger float and we will need good water tight canvas for dodger and deck covers anyway.

    At this point I think we should concentrate on building you a good strong canoe main hull. I think we should stick with a flat or close to flat bottom and that you should not make the main hull very skinny to avoid a lee board (just make a lee board, no problem). You still have quite a load and you should be able to sleep inside the canoe on the beach or at anchor without unloading your stuff and risking it being stolen. I think you should consider a raised floor in the middle that allows you to store heavy dense stuff like water and provisions under it. The raised floor will be dry and the heavy provisions will be secure in the best position.

    The JEM canoe is 18ft X 35inch beam and will carry your load nicely. I think it is a 3 sheet design. If you have enough epoxy to build the JEM stitch & glue and cover the bottom with glass and epoxy as high as the waterline I think it would be the best use of your resources. I don't know how much epoxy you have, could you weigh it and tell us?

    If you are short on epoxy you could build a flat bottom canoe with PL premium glue and chine logs, then epoxy and glass the bottom.

    About sailing south -Before you leave you should know all about the coast, all the safe bailout points and how far it is to the next safe harbor. This info and the weather will determine how far it is safe to sail so you need the best weather info you can get. VHF radio has weather channels and is carried and monitored by almost all boats. If you have one for distress calls and for information it will greatly improve your safety and range.
     
  11. bpw
    Joined: May 2012
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    bpw Senior Member

    Try to get a copy of one of the sailboat cruising guides for the coast, will give you a lot of good info, also one of the chart books, pretty cheap and will cover the whole west coast of Mexico. There are a few parts of that coast where you will not be able to stop, you will want to know when they are coming.

    A VHF could be useful for emergencies but I would spend the money on an Epirp if you can only afford one. A lot of places on the Mexican coast you will not be heard by anyone if you only have a portable VHF. Thre are almost no VHF weather broadcasts in Mexico, but at least the weather is pretty stable so not too likely to surprise you. Look up passageweather.com for good online wind and wave prediction.

    If you are near a anchorage with sailboats go talk to some of the cruisers, they could tell you a lot about what to expect.
     
  12. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I have been following your progress from the beginning.

    skin-on-frame is one of the most cost effective and light weight ways to build a hull. I have built something like 20 SOF small boats, kayaks, canoes and small sailing dingys up to 18 ft long. I like the method because of the lower cost and the faster assembly, and there is no handling of costly and toxic adhesives like epoxy.

    All of the strength has to come from the frame, so the stringers, gunwales and keel have to be a bit heavier than for plywood skin boats, the hulls tend to have more parts than a plywood hull, and the heavier frames tend to take up more interior room than a plywood or plank hull. the design can be very tough and economical to build, but skin toughness is an issue. heavy 16 to 20 oz /yard fabric is expensive, and as noted it is not well suited to dragging up on a beach fully loaded (though you can protect it by installing rub strips).

    The other problem you would face it there are a lot fewer successful designs of skin on frame hulls for anything outside of a kayak or canoe type of hull. It would be easier to find a similar size plywood on frame or stitch and glue design and adapt it to your purpose and just copy the details. I have designed and built SOF sailboats (5 of them), but I had to develop my own plans and design details (often after several redesigns), and I have been designing and building small boats for over 3O years. to build a custom design in SOF you would be on your own in working out the design problems. Not really a good idea for someone with limited experience. The fact that there is less storage volume for any given size is also a consideration for you.

    so, yes it can be done and you end up with a good boat design, but there are some drawbacks that might preclude you from choosing it. I have ideas for a pocket cruiser 16 ft sailboat done in skin on frame, but the design has not been built or tested yet, so I would not recommend it until it has some sailing time to know if there are any unforeseen conditions or problems that have to be worked out first.

    With your short time schedule, it would be best to stay with a proven construction method for your intended use. You do not have the time nor the budget to work out problems after you have it built. While I would be willing to do that since I expect to have to work out design problems as I go, I would not ask someone else to do it.

    keep the pictures coming, we are all eager to see you succeed.
     
  13. WilliamPrince
    Joined: Oct 2013
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    WilliamPrince Junior Member

    Okay so I have begun construction. I am going to be building a design very similar to the Flaquita. In fact, I was going to order plans but unfortunately Joe Henry is unable to send any plans until November 6, and then it would take ~10 days to arrive so based on my time schedule that will not work out. With careful inspection of all his pictures, I will work out my own dimensions as close as possible.

    I started by getting started on the ama, as it will be a much simpler construction than the main hull. It will be 14 feet long, with a basic triangular frame of plywood frame pieces and 40mmx25mm wooden chines at each corner, as well as one running down the top. I will be done, or at least close to completion by tomorrow, so I can put up some pictures so you have a better idea as to what it look like. I am operating on offsets drawn by peterAustralia (much thanks) which can be seen here: http://www.tacking-outrigger.com/ama_14.html . I hope it is kosher of me to post that... But I think he would not mind, and since he will be away for a while, I will take all extra help available.

    Anyways, I have a few questions about this, as it is what I was working on all day today. I have read in many places about a hull being "self-bailing", and I have looked all over but not really found a good answer as to what that means exactly. What is a simple mechanism I can build that will make my hull self bailing? Are there any dangers to a self bailing system?

    Anyways, as for the construction method... I think the consensus is right that switching building methods so late in the game is not a good idea, so I will stick with the plywood construction. And as Petros points out, there is much less support out there for building with the SOF method... Would be more difficult in many ways.

    As for the epoxy, Sky, I have 2 gallons of West System 105 epoxy resin, with sufficient hardener. I will look into getting fiberglass when I finish the ama. I want to get the ama done first and quickly, for a few reasons, primarily that it is good practice, with relatively little expense (about 30$ of material), and if I make too many stupid mistakes, worst comes to worst I can make it again in a day.

    As for the main hull, I am conflicted as to how to design this thing... One option of course is the 18 foot Jem canoe, which as far as I can tell looks like a good canoe. I also have plans saved in my phone already, so that is a huge plus. My other option is to attempt to piece together my own plans based on the Flaquita pictures. As you mentioned Sky, the wide beam of the Jem is going to make it much nicer to live in, so I am inclined to go with that. But I dont know if the outrigger of the Flaquita will work well with that.. And how would I attach a sail to the Jem? Maybe these are nooby questions, but I think I am still within my right to be asking nooby questions :)

    Also, can I use regular wood shavings as thickener for my epoxy mixture? Or I must I buy super-fancy West System wood shavings which are far superior to my wood shavings.

    One last question, about the apropriate board to use... I think a centerboard is obviously not a good choice, but what are the pros and cons of a daggerboard vs a leeboard? Is a leeboard really strong enough to withstand that pressure? If I do make a leeboard, what side would it be on, the same as the ama, or the opposite? Also, how should I go about construction said board without a power planer? I guess i do have an old fashioned manual planer... Will that be possible or would it take ridiculously long?
     
    Last edited: Oct 22, 2013
  14. El_Guero

    El_Guero Previous Member

    Self-bailing really means there is a deck above the waterline, and there is a one-way valve which lets water drain out, but not back in.
     

  15. El_Guero

    El_Guero Previous Member

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