Looking for Cat plans. Suggestions?

Discussion in 'Boat Design' started by Tropical Sailor, Jun 4, 2014.

  1. Tropical Sailor
    Joined: Sep 2013
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    Tropical Sailor Junior Member

    Good day,
    I´m looking for plans or a design for a catamaran or double canoe that can be built without using plywood and epoxy. Tropical hardwoods are available here on a limited basis cheaper than imported marine ply and epoxy. For those of you who remember my previous threads I have been looking for a project to build with some young men that I have been teaching in a small fishing village on Yucatan’s Northern coast.

    http://www.boatdesign.net/forums/boat-design/what-type-design-hull-form-please-see-fotos-48477.html

    http://www.boatdesign.net/forums/boat-design/modified-bolger-idaho-tourism-safe-design-48578.html

    I have finances for possibly two years more here in Mexico and can dedicate a large portion of my workweek to the build and teaching carpentry to these youths. Volunteering as an English teacher is what got me started with these young people, but from there I have taught a small group of them to sail. And I would like to leave them with more than just memories. I would like to leave them a craft that they could sail and maintain themselves and possibly even create a source of income for some of them, i.e. artisanal boat building, fishing without the cost of 100 dollars a day in gasoline, or a tourism business taking people over to the island of Holbox or just day cruising in the estuary to see the flamingos and flora and fauna.
    I thought of building a Wharram Melanesia, perhaps building two hulls and making a double canoe instead of an outrigger. The Wharram Ethnic designs have many benefits for my students like low cost of construction and maintenance and all spars and rigging can be make from nature or cheaply purchased. The thing that put me off to Wharrams was the price of the plans. The plans for the Melanesia cost 120 British pounds plus shipping. When you compare that to the cost of the build (Wharram estimates that the Melanesia can be built for 300 British pounds) that´s more than a third of the cost of the boat in just the plans.

    Even better suited to the needs of the young men I´ve been teaching (and to whom the boat would belong) would be the Wharram Amatasi. It´s interesting that the Amatasi was designed to fulfill the needs of a group of people that are exactly the same needs that my students have, but for opposite reasons. Wharram says on his website: “The 27' Amatasi with similar hullshape to the Tahiti Wayfarer, won first prize in the 2010 Classic Boat Design Competition for an eco-fishing boat. Capable of offshore cruising, there is a demand for her in the Pacific as a transport boat between islands.” On another part of his site I read that all his ethnic designs were motivated by a lack of good timber and the resultant high price to build traditional pacific island craft on the islands. He therefore designed traditional looking double canoes and proas that serve the same needs as the traditional craft, but that can be built with ply and epoxy. Apparently this form of construction is cheaper there than trying to find trees or planks of the size needed on Islands that have been depleted of lumber long ago. Unfortunately, the reverse is true here in northern Yucatan in Mexico. Here building in ply and epoxy is cost prohibitive. I learned this fact on this forum and then confirmed it for myself. Because everything here used for “modern” boat building has to be imported, marked up, taxed, tariffed, and passed through a chain of hands all wanting to make a profit, it would be impossible for us to build with the stich and glue technique. Even something like bronze boat nails would be hard to find and very expensive. So what options remain? … As a member of this forum explained to me in a previous post, “Local naval carpenters are all dead now or very very old. Classic wooden boats ask for a craftsmanship you have to learn over a long period. In Asia this knowledge is always alive; the Indonesians make wooden boats 40 meters long. But in Mexico and Central America it's all gone 30 years ago.” So if traditional naval carpentry is dead here, wouldn´t it be nice if I could contribute, even in a small way, to its renaissance. Forty years ago with export and domestic use the native tropical hardwoods were becoming endangered. But now that export of hardwood isn´t common here and the naval carpenters no longer exist and therefore no longer use these woods and with strong conservation and replanting initiatives on part of the government, there is now access to many species of exotic and traditional woods here suitable for boatbuilding. Up until 2 years ago I owned a cattle ranch here in Yucatan. The majority of the 1200 acres was in what they call here “monte” or over grown wilderness. Most of the pastures had been abandoned over 70 years ago and nature had taken over restoring the dry jungle, with a small part of old growth trees still standing. I spent a lot of time walking under that canopy and built some wonderful “palapas” or roofed enclosures like open air pavilions with palm thatched roofs. If you´ve ever been to a Cozumel beech club you´ve seen the type. Sorry, I digressed, but the point is that I found many types of trees that would be usefull for boatbuilding. There are those that everyone is familiar with, like mahogany, teak, and cedar. There are others that I only know their names in Mayan or their Latin scientific names, like: Manilkara acras, Ya’ax Ja’abin - Piscidia piscipula, Bojón - Cordia alliodora (for spars), or Rhizophora mangle. (The last one wasn´t found in my ranch but is readily available here on the coast)

    So, that is why I need plans for a catamaran or double canoe that can be built form more traditional materials, or at least without ply and epoxy. Of course I would like modern plans that take advantage of labor saving techniques developed in the last 30 years. I would prefer not to have to build something as they did a hundred years ago, but with the materials available to us, what can you suggest?

    SOR –
    1. 20’ to 27’ long ( I know that covers a huge range, but I´m open because if the right plan is found one size could serve for some of the uses, while a larger craft could serve all of the needs listed)
    2. Cat or double canoe with simple deck between.
    3. Used for eco-fishing or eco tours or eco water taxi. (There are some Islands off the coast that are not even a kilometer away and they have the beaches the tourists want to get to)
    4. Simple sail rig and small outboard.
    5. Ease of construction with frames and planks or another type of construction that doesn´t involve ply and epoxy.
    6. There are some things about the Wharram Tiki designs that I think would be useful, like the V formed hulls. No need for dagger boards or keels or center boards which simplifies the build and the sailing as well as reduces draft and gives good reserve buoyancy for loading caught fish or passengers.

    The Tiki designs seem to employ an almost equilateral triangle with one corner pointing down as the midship frame, then the triangles slim towards the bow and stern. It seems so simple that I thought maybe I could even design it myself using hardwood frames and cedar planks. But I downloaded freeship last night and can’t get the results I want, so I´m asking for your opinions about a design that will fulfill these requirements.

    Thanks,

    Andy
     
  2. Tropical Sailor
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    Tropical Sailor Junior Member

  3. Petros
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    Petros Senior Member

    Though at the large end of the size range for skin-on-frame hulls, I would consider using that if you can get enough heave fabric to cover the hulls. 10 or 12 oz cotton duck or canvas, or even better, same weight nylon or polyester fabric (uncoated) also would work well.

    I have designed and built perhaps 20 or more skin on frame small boats, mostly kayaks but have also used this method on a number of sailing dingys. It is very efficient use of materials, and very lightweight, no plywood or glue needed at all. With this type of construction you are separating the structural frame from the need to keep water out by using a water proofed skin to make it water tight. I had considered using this method to build a beach catamaran, that is light enough to put on the roof of a typical economy car (less than 200 lb for 17 ft long hulls). For your use I would make the frame heavier to make it more durable, and use a heavier fabric if you can find it. On the kayaks and dingys I 9 oz nylon. You can get up to 20 oz nylon or polyester, but it costly and likely much heavier than you need, about 12 to 14 oz would be ideal.

    For the frame I would make the gunnwales about 1x4 inches (net dimension, or next size up you have available, a 1.5x3.5" or larger would work), stringers to hold the hull shape can be 1"x1" (3/4" square min), and make the keel from a 2x3 laid flat. put frames at about 2 ft spacing made from 1x4 stock. Screw it all together with large counter sunk bronze or stainless screws. You can also lash the frames together if you can find suitably strong lashing cord, polyester works the best (low stretch), nylon is unsuitable (too much stretch, the knots fall out when wet). You can use the same hull lines off a proven design, any hull designed for plywood construction also would lend itself to skin-on-frame shapes.

    You do not want the fabric to bridge more than about six inches between the stringers. You first stretch it length wise, and than wrap it towards the gunwalls. you can either tack the skin on the frame at the gunwales (or use nailing strips of wood) or hand stitch it closed where the seams meets at the center line on top of the hull.

    Search the web for skin-on-frame kayak details to get an idea on how it could be built, you just want to make it a bit heaver (not too much heavier, you will add a lot of weight). With hand tools I can build a skin-on-frame catamaran in the 20 ft long by 10 ft beam size in about two weeks worth of work, one week with a building partner. The hulls would be about 1.5 to 2 ft max beam. Presuming all of the material and tools are at hand.

    You can seal the skin with any durable oil based paint, I like one part oil based polyurethane floor finish (tough), but inexpensive Acrylic paint also works, it just needs to be touched up at the keel often. Use min seven layers of paint to fill the weave and make it durable and water proof. With the skin on frame you can also add an external keel strip of hard wood to protect the skin from dragging it up on the beach.

    dagger boards can be made to work with this type of construction, but it complicates the build, I would suggest using lee boards so you do not risk a leak through the hulls, or a single large center board under the deck.

    good luck.
     
  4. Tropical Sailor
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    Tropical Sailor Junior Member

    Thank you Petros for your response,

    I had never considered skin on frame for something this. Truth is I know less about it than I do about plywood and epoxy. (Of which I´ve built one boat by Bolger) I will have to do some investigating online and then here to see if the materials are available and how much they cost. I might consider using this technique for a smaller versión of the Cat I have in mind. One that will not leave the saftey of the lagoon. But for a fishing boat that goes 12-20 km offshore I would be afraid of a droped knife or a flopping fish that might pucture the fabric creating a catastrofic failure at sea.

    Thanks,

    Andy
     
  5. Richard Woods
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    Richard Woods Woods Designs

    I was surprised to hear that you couldn't get any plywood at all, of any quality in Mexico. I thought it was pretty much universal these days. I haven't sailed in the Yucatan, but have sailed past it when cruising form Cuba to Belize and onto Guatemala. I have travelled overland there though.

    If you cannot get plywood you probably cannot get suitable fabric for a SOF boat either

    So what is the thinnest lightest suitable wood you can get? If you can get a lightweight wood 12mm thick planks then you could possibly build a hard chine Janus by planking the hulls with 70mm x 12mm planks. (That's why I like using it)

    You don't need epoxy, after all few people used it before 1980. Any waterproof wood glue will do, but the advantage of epoxy is that you can still have a strong leakproof boat even if there are gaps between planks

    http://sailingcatamarans.com/index.php/designs/2-catamarans-under-25ft/166-janus

    or maybe an open deck Gypsy

    http://sailingcatamarans.com/index.php/designs/3-25ft-to-30ft-catamarans-designs/176-gypsy

    and no doubt we could sort out a suitable design fee

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  6. Alex.A
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    Alex.A Senior Member

    Google or search this site for Ontong Java. Large catamaran/ndrua made by Hans Klaar.
    The canoes it was based on come in many sizes. Papua New Guinea style proa's could also work. Look for indigenous canoes to copy and adapt?

    Also check out : journey2live.com
     
  7. Petros
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    Petros Senior Member

    That kind and size of sail boat is perfectly suited to skin on frame. Larger skin-on-frame boats have been used to travel long distances, even across oceans. Many have been built up to 35 ft or so in length, using animal skins for hull fabric. Tim Severin sailed a replica of a 36 ft leather skin and frame boat Currach from Ireland to North America on a two year voyage just to prove it could be done.

    No need to have any concerns for fish or even rocks damaging a skin on frame hull, they are far more tough and damage tolerant than plywood and epoxy/fiberglass. with the heavier fabric weights (12 oz and higher, up to 20 oz), they are almost impossible to puncture. About the only way is to puncture it intentionally is with a really sharp knife and a lot of force (which would also badly damage any composite or fiber glass over ply). even then they are easy to field repair. With internal decks there is no chance of having cargo press against the skin anyway. Aleutes and Greenlanders used both skin-on-frame kayaks and umimaks (large open skin on frame skiffs) to transport game and cargo long distances in the north sea in some of the harshest weather on the planet. It would be perfectly suitable for tropical waters.

    The suitability of if whether you can take it off shore or not is the design, not the construction method. A well built and strong frame, and heavy tough fabric properly treated would be suitable to sail to Hawaii.

    You are far less likely to develop leaks with skin on frame than any plank construction. Consider conventional plank on frame; each mating surface on each and every hull plank has to be very accurately made, hand caulked, and than almost daily maintained. As it flexes and the wood ages it will develop many leaks, as any one with a plank no frame hull can tell you. All this is effort and potential points of leaks (the whole hull) is gone with a single fabric skin. The skin does have to be replaced every several years as part of normal maintenance. Much easier and faster than recaulking or replanking a hull. And if it can be stored out of the sun it will likely last much longer.

    If I were there I would be building these boys a large skin on frame catamaran presuming you can get suitable fabric.

    Build yourself a skin-on-frame canoe, it should not take more than a few days or a week, and about $100 worth of materials (much less if you salvage materials) and prove to yourself it is an excellent alternative to conventional plank on frame.

    Here is a 14 ft skin-on-frame sailing dingy with my daughter and I in it at first lanch, I am considering buiding 16 ft version of this with a small cabin on it for overnight stays.
    [​IMG]

    here is an open sailboat built by others, showing what is possible.
    [​IMG]

    here is an alaskan Umiak, skin-on-frame with a heavy timber frame. I have actually sat in this particular boat, it is at the center for wooden boats in Seattle.
    [​IMG]

    here is a nice example of skin-on-frame adapted to a row boat;
    [​IMG]

    Here is a nice adaptation of an out-rigger sailboat done with skin-on-frame;
    [​IMG]

    as for how tough they are see these durability tests (these use much lighter fabric than 12 oz), try doing that to any fiberglass hull!!!;

    https://www.youtube.com/watch?v=gYyvIExWkqU

    https://www.youtube.com/watch?v=ATktVym_NeI
     
  8. Tropical Sailor
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    Tropical Sailor Junior Member

    Hi Richard,
    We do have plywood here, but it’s not very good. What we don’t have is marine grade plywood or epoxy. I guess the glue used here is not for exterior use, as I’ve seen the laminates of plywood come apart if exposed to the elements. And without epoxy to encapsulate the plywood I don´t think it would last long in a marine environment. A member of this forum lives in Cancun and he said he occasionally imports marine plywood and epoxy for “wealthy customers” of his in Mexico City. The very high price of imported plywood and epoxy is what prevents me from using it.
    You asked what types of wood are available. And if I could get it in 12 x 70 mm planks. White Cedar (Cedrela odorata) is abundant in the forest here. It’s highly prized for furniture making because it is knot free and is easily worked. I understand that it was used in traditional Yucatecan boat building until that era ended. Also, teak, mahogany, and “Jabín” (Piscidia piscipula) are grown here. “Jabin” is an indigenous hardwood very similar to teak and is widely distributed in Yucatan. It was also used in traditional boat building here for keels and frames.

    To answer your question about if it’s available in certain sizes, I should explain that most of the lumber for this project will be trees donated by friends and relatives of the group who have 50 acre parcels of forest under the Mexican “ejido” system. We will have to harvest the trees ourselves with chainsaws. To get specific sizes of planks we could square off the trunks, just taking off the outer curve and then transport these timbers to local saw mills to cut the planks. I´m not sure, but I imagine they can mill them down to ½” by whatever width we desire. So, yes, ½” x 2½” or 12 x 70 mm shouldn´t be a problem.

    Are you suggesting gluing the sides of each plank together? Like strip planking? Gluing and nailing each plank to the previous plank as well as the frames?

    I appreciate your offer of plans; much of this boat will come from donations. Besides the donated timber, some of the local fishermen are helping with the hardware and I´ll be providing the canvas or Dacron or whatever to sew the sails. I have a lot of extra line that I carry on my Cal 27 (and extra sails too) that I´m going to use for the running rigging. The boatdesign.net member that lives in Cancun feels that we might be able to get some support/funding from the local government. But, I think that would be easier after the project is started and we have pictures and plans and can provide a written summary of the project requesting aid to finish it.

    About the Gypsy, I think It´s too big. I would trade my monohull live aboard for it any day, but for this project I think the freeboard is too high and the amount of material and time required too much. On the other hand, your acorn, janus, or shadow might work fine.

    Thank you very much,
    Andy
     
  9. Tropical Sailor
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    Tropical Sailor Junior Member

    Wow! Thank you so much, Alex. I thought I had already found all the cool sailing web sites, but these were great. As I investigated Hans Klaar, he reminded me of Capt. Slocum, trading one product easily acquired here for something precious there and making a profit on the deal. I wish traditional boat building wasn’t dead here in Mexico. At least he had the benefit of local shipwrights in Africa to help with his build. There aren’t any left here. But it does show what can be done with heavy timber and planks.

    If you read Columbus’s log from his last voyage to America, he met Mayan traders in a 60 ft long, 8 ft beam dugout canoe. It was made from Ceiba, the Mayan holy tree of life. That grows everywhere here, but I always thought it didn´t have any value except as pulp. Maybe it would work as planking. Did you notice the huge time used for his keel?

    Andy
     
  10. Tropical Sailor
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    Tropical Sailor Junior Member

    I can see you are very passionate about SOF. I guess you might be right also. SOF does seem to lend itself to catamaran building. Cats seem to work best as light weight craft, not to be overburdened or overloaded. Instead of heavy frames and planks, maybe light frames and fabric skin would be more suited to a cat. But, personally, I just wouldn’t feel comfortable leaving a 20 something foot SOF to these young people knowing they will be out there in the Gulf out of sight of land and me back in Texas.

    But if you want to really convince me, why don’t you come down and put on a seminar/workshop/course for these kids. And we´ll build a canoe or even better one of the hulls of the catamaran.;)

    Only, I haven´t had time to investigate online what chemicals and supplies are needed and if they are available here.

    Andy
     
  11. Richard Woods
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    Richard Woods Woods Designs

    Whatever desires you have you cannot escape reality. The Tiki21, for example, is a minimalist lightweight boat with low freeboard. It is built in 6mm ply with very little framing.

    So to make it float at the same WL you'll need to have a hull skin weight to match 6mm ply. So 12mm thick planks of any wood will be pretty much twice the weight, so the boat will be too deep in the water

    That's partly why I suggested the Gypsy, the bigger the boat the less the weight penalty will be noticed. Similarly the higher freeboard will help, as will the dory shaped hull (again as used on the Janus). That's why I didn't suggest my deep V Surfsong or Windsong designs, even though they are built traditionally with stringers and frames rather than stitch and glue

    Ceiba is kapok, I'm not sure how durable it is, nor how well it can be sawn into planks. Dugout canoes are very different and typically only have a 5-7year life

    I'm also surprised that the Mexican govt doesn't waive import duties on materials used for tourism infrastructure. Right now I'm checking with a contact involved with tourism projects in Mexico, I suggest you PM me or email me on my normal email address, or via my website. It would help if you were a US citizen...

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  12. Petros
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    Petros Senior Member


    That actually sounds like a fun idea, I would be game. If we can have the materials and tools ready likely I can demonstration build a canoe or a smaller beach cat in a week or two as soon as I arrive.

    Not sure how much it would cost me, but almost certainly my wife would not allow me to go on a trip like that without her. Perhaps my daughter too, she is actually fairly fluent in Spanish, currently lives in Austin TX. I am afraid I have almost no skills in Spanish at all. I have been to other parts of Mexico, but never the Yucatan, I do not know anything about it. lots to arrange, accommodations, transport to and from the airport, etc. what is your time table?

    You would get at least a boat out of it. If we can do the travel economically enough I might be able to stay long enough to get your full sized boat built and on the water.

    What is the chance of that actually happening? you might PM me if you would really want me to come and help you build a full sized skin on frame cat for the locals. I would consider it, depending on costs and details.
     
  13. Nnnnnnnn
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    Nnnnnnnn Junior Member

  14. Tropical Sailor
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    Tropical Sailor Junior Member

    OK. I´ll send you an e-mail later today.

    Thanks,

    Andy
     

  15. Tropical Sailor
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    Tropical Sailor Junior Member

    Air fare to Cancun is the lowest of any airport in Mexico and has the most direct flights to cities in the US. We are only 2 hours by car from Cancun. I would be glad to try and find you accommodations here that wouldn´t cost you anything. But, I fear they are not what you are accustomed to. This is not a tourist area like Cancun. Almost the only international tourists are those who own the large houses right on the beach. Most of these costal fishing towns in Yucatan have a separate (sometimes even gated) community for foreigners. Many of them rent their beach houses, but they charge upwards of a $1000 a week. I have a friend who is a Mexican industrialist who also has a house here on the beach. When I had my ranch, I often hosted his (as well as my) foreign friends and organized many archeological excursions and beach trips and day cruises. (If the business plan for my ranch had been a bed and breakfast, instead of a Gentleman farmer/Cattleman/Horse beeder hobby retirement plan, it might have worked) So I´ll ask him about lending me the house if it´s not occupied when you visit. (He´s going through a divorce and his wife always handled the renting of the beach house. That might complicate things. But I´ll do my best. You and your family would be much more comfortable there. I´ve been here so long that I don´t even miss air conditioning. But, I´m sure you´ll appreciate it.)

    I think the best way to start is to do as I wrote before and investigate this form of building thoroughly and find out all the materials needed and then see if they are available here. And if they are, what is the cost and how will that affect the project.

    Secondly, we need a plan and a bill of materials. (Maybe firstly) I think Richard Woods might help us with that.

    Then I need time to harvest the trees and rip the timber. (I have some experience with making 2 X 8 hardwood railings for wooden fences and corals and stables and round pens at the ranch. But I used a chainsaw for the whole process, as the results were supposed to look rustic.

    Because of your greater knowledge of this type of construction, why don’t you send me a list of the materials generally used and I can start investigating if they are available and at what cost. While I still intend to investigate for myself online, this would speed things up considerably.

    I´ll send you a PM with my email later today.

    Thanks,
    Andy
     
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