Microcatarmaran

Discussion in 'Fiberglass and Composite Boat Building' started by sebaseba, Apr 14, 2020.

  1. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    Hey,

    I got inspired a year ago with this project DIY Styrofoam Catamaran https://www.instructables.com/id/DIY-Styrofoam-Catamaran/. I am thinking of building something similar myself, but better. This one is rather flimsy.

    I would use it for slow sailing/rowing or having a picnic on water in 2 maybe 4 (although that would be tight) on calm fresh waters (lakes, slow rivers), maybe sometimes on sea bays in calm weather.

    I would make it 3 m long (that's the legal limit of max. length not requiring registration, although on fresh waters it's 5 m). I would paint first XPS with acrylic emulsion to make a better water barrier, increase adhesion and decrease resin absorbtion. I would put on rowing fiberglass and epoxy (epoxy and poly is here approx. same price).

    I was thinking of making the whole boat 2 m wide, maybe cover the whole upper part with a net or net-like fabric, water repellent. Maybe making it easy to disasemble, so like double FRP + XPS core "canoe" + upper part maybe made out of aluminium tubing + net. Maybe something like Technische Details | https://www.mini-cat.de/konzept/technische-details/, just with net of whole length. I like the idea of transporting it on the roof of the car.

    I don't have much experience with fiberglass, mostly for fixing holes in the car. I've used poly and that chopped mat for that. I've used epoxy mostly just for wood coatings. I have woodworking experience, some construction experience, 3D printing experience, electronics experience. Studied chemistry, so I don't have an engineering degree, but I know math/physics well enough to learn more. I have some sailing experience (8 m long sailboat), but I was always part of a crew of 3-4 (incl. me), but I did all the "jobs" on it, so to speak.

    I'm reading now Larsson: Principles of Yacht Design to first grasp the basics. What do you suggest that I read further?

    Also I'm open to suggestions regarding the boat idea. I've read also that XPS is really hated on here, although I'm not really sure why (read various arguments, but it seems to me it's more to personal preference and local conditions, what's cheaper). Well I could remove it theoretically and be left with void space, but I kinda think it's cool to have it inside.
     
    BlueBell likes this.
  2. bajansailor
    Joined: Oct 2007
    Posts: 1,247
    Likes: 343, Points: 83, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Sebaseba.
    Re your comment
    "I would use it for slow sailing/rowing or having a picnic on water in 2 maybe 4 (although that would be tight) on calm fresh waters (lakes, slow rivers), maybe sometimes on sea bays in calm weather."
    does this mean that the passenger capacity is 2 - 4 persons?

    I am just wondering if even a paddleboard would have to be registered if you use it on the sea?
    If not, then it might be easier to try to buy a couple of paddle boards on the second hand market (are they popular in Slovenia?) and build a catamaran with these instead?
     
  3. alan craig
    Joined: Jul 2012
    Posts: 258
    Likes: 43, Points: 38, Legacy Rep: 14
    Location: s.e. england

    alan craig Senior Member

    You mention XPS (eXtruded polystyrene) but I think you may mean EPS (expanded polystyrene). EPS/styrofoam is the crumbly granular stuff and XPS sheet is stronger in compression across the faces as it is made for underfloor insulation.
     
  4. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    Sport equipment theoretically is not needed to be registred, but what falls into that is random in more gray areas like for example a Laser class sailboat is sport equipment or real sailboat, depends on which officer you find. I enquired officially and they've said it's sailboat, i.e. > 3 m, so it has to be registred.
    Well registering is not such a tremendous big deal, even if you make it yourself, it's possible, but I would try not to for my first boat. :)

    That's a possiblity certainly, possibly cheaper. I'm tempted, but I also want to try to make it myself out of scratch. I like that idea too, so that maybe if I'll like it, I learn how to make something bigger in the future. :)

    No, I mean XPS, Styrodur. That's correct, for underfloor insulation. I like the material. I've used it to make arches in construction, covered then with cement and all that.
     
  5. alan craig
    Joined: Jul 2012
    Posts: 258
    Likes: 43, Points: 38, Legacy Rep: 14
    Location: s.e. england

    alan craig Senior Member

  6. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    Thank you. Seems that the idea can work. I like the idea of powerdrills. I have one without a battery, I could use that and attach some lithium batteries. Would be probably enough for what I need.

    He mentions that the fibre choice he did wasn't optimal, but I can't find which fibre he has used.

    Also he tested with just a single layer of fibre and it was super stiff, which is what I thought.

    Thank you again! :) I was really discouraged insofar for testing the XPS/epoxy/fibre idea.
     
  7. BlueBell
    Joined: May 2017
    Posts: 1,268
    Likes: 246, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Youtube, learn how to build, even airplanes, out of foam covered in fiber/epoxy.
    The trick will be getting the two hulls close to the same.
    Suggestion: build them at the same time, going back and forth, from pontoon to pontoon, with each step.
    And search this website for past reference to what you want to do.
    Great project!
     
  8. hoytedow
    Joined: Sep 2009
    Posts: 5,654
    Likes: 274, Points: 93, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Bananas

    Welcome, sebaseba. Get some scrap cardboard and make cutouts shaped like various hull segments. You take them from one hull to the other to check for sameness.
     
  9. upchurchmr
    Joined: Feb 2011
    Posts: 3,053
    Likes: 150, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    maybe you could expand this one.
    [​IMG]
     
    fallguy, Dejay and bajansailor like this.
  10. Dejay
    Joined: Mar 2018
    Posts: 520
    Likes: 83, Points: 28
    Location: Europe

    Dejay Senior Newbie

    Not a boat building channel, but a nice compact tutorial for a plywood + fiberglass "tesla catamaran". Plywood might actually be easier and more fun to build with since you need less thickness of fiberglass / epoxy and it's sturdier (e.g. 200g/m² vs 1000g/m²).
     
  11. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    Thanks for both! :)
     
  12. hoytedow
    Joined: Sep 2009
    Posts: 5,654
    Likes: 274, Points: 93, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Bananas

    Keep foam but in a shell.
     
    BlueBell likes this.
  13. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    OK I have thousands of ideas how to do this, but my lack of experience with fibre is showing. I wanted to make the boat easy to disassemble. I'm thinking of making two "canoes" and then perpendicularly aluminium tubes. Now, the problem is how to do it.

    One idea is to put an another tube parallel to the "canoe" then just use some sorts of T-joints.
    Second idea is to have just a T joint that is fixed on the canoe.
    Third idea is to have vertical pipes and then T-joints.

    The first and third idea I have a bit troubles imagining how is best to join the pipe with the FRP.
    Should I just make holes in it, where I could slide the tube in and then use pins in the tube, to not let the tube slide out?
    Should I glue/fibre the pipe to the rest of the structure?
    Should I use screws and clamps inside the structure?

    For the second idea how to attach the T joint? In big boats I know, it's a sandwich structure, you go underneath and just put big washers. But how would I make it here? Maybe square holes in the sandwich structure, so that there is 5-10 cm of material above and then screws going through? Maybe just screws throught whole structure and maybe flat plate for washer.

    Due to galvanic corrosion it's also a problem to use aluminium and other materials. From experience of others (and some knowledge) I've found out that it's best to avoid mixing stainless steel and aluminium, but better to combine zinc coated steel and aluminium, for example for screws/threads/t-joints. Also to put an insulator in between, like rubber.

    Aluminium T-joints, that aren't flimsy or super expensive, seem hard to find. I was thinking of maybe using zinc-steel clamps for fixing pipes on the wall (they are rated for 1100 N) with rubber between. Or those basic one part clamps or those from cars for exhaust. An another idea would be to 3D print (I have the printer so it would be easy) them and reinforce them with fibreglass or carbon fibre or to 3D print a mold and do it from fibreglass or carbon fibre. I could also CNC the aluminium parts, but I don't have the CNC, but I have a friend which has.

    An another idea I've found, regarding "canoes" (and a bunch of other ideas). Video of a sailboat version:

    [​IMG]
     
    Last edited: Apr 26, 2020
  14. Dejay
    Joined: Mar 2018
    Posts: 520
    Likes: 83, Points: 28
    Location: Europe

    Dejay Senior Newbie

    I believe 3m (10ft) is on the low side for beach catamarans, otherwise you could find lots of cheap or even free plans. I'd at least look at them on how they build the beams and fastenings. But short means slow and also wider to get enough buoyancy. Even most canoes and kajaks are longer. Going a bit up in size is probably going to make your project easier.

    And again, building with plywood is cheaper if that is a priority. If I were to build a fun beach sailboat I'd build a E25 harry proa with foam core vacuum infusion. Buying a second hand beach cat or some orphaned amas is probably the cheapest.

    I've seen someone 3D print deck hardware for a small boat but I don't remember where. Here are some examples.
     
    sebaseba likes this.

  15. sebaseba
    Joined: Apr 2020
    Posts: 40
    Likes: 8, Points: 8
    Location: Slovenia

    sebaseba Junior Member

    Thank you for the links.

    Of course I'll research how others have done it. I'll research a lot before even starting. I just like to think first for myself first and then see how others have solved some issues. Then I value their solutions much more, otherwise I just take them for granted or don't even notice those details.

    To be honest, price of construction is not the main priority, more so running costs. The idea I have now is to make it light weight and make it possible to disassembly. Wood is a good material to do it, but I'll try to avoid using it, because I want to "get to know" other materials better. I use wood too much in my life, lol.
     
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.