DIY Simple Catamaran Sailboat Design

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

  1. Manfred.pech
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    Manfred.pech Senior Member

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  2. SamSam
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    SamSam Senior Member

    That was an adventure! I notice a few handy items in the photo...an outboard and a lifeline!


    .
     
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  3. WilliamPrince
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    WilliamPrince Junior Member

    Okay, the fiberglass splices are well underway, I expect to be finished by tonight. I am on a schedule with this, because I only really have 1 area suitable for the panels to sit while curing, so I apply the fiberglass/epoxy, let sit for 3 hours, then do the next (flip it over and do the other side, or do the next panel if both sides are finished). I did this all through the night last night, to expedite things, so I am running a little low on sleep, but it paid off, I will be done by today.

    Tomorrow I plan to start coating all the panels in epoxy, front and back. I plan to do two coats on each piece. I am going to rent or buy a sander, not the orbital one but the other kind, the flat kind... Not sure what to call it. I didn't like the orbital much, even though it got the job done.

    What is the best way to apply multiple coats? I don't want to wait until it hardens completely of course, but what is the best time to do that?

    I also have one question... Something worried me a little. When I did the fiberglassing on one side, a certain amount of epoxy would leak out and cure on the other side of the seam, the flip side of the plank I was gluing. Is it okay that I just put the fiberglass right over that? Or will the epoxy not bond to that, creating a weak point? It was only serious on one joint, and I plan to epoxy over that anyways, so is there really anything to worry about?

    Anyways, contrary to my discouraged post before, things are going quite well, all panels came out pretty much as they were supposed to.. Will post pics of my panels when they are done!

    Thoughts on the process and of my plan to epoxy them tomorrow? Is that the correct order? Or should I epoxy everything after I stitch it together/lay my fillet joints?
     
  4. kerosene
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    kerosene Senior Member

    Are you still planning on putting a full fiberglass cloth on the outside? inside?

    I wouldn't worry about multiple coats before you do the tape/fabric work. Inside might make some sense as its harder to get to once the boat comes together but for outside early coating is not needed - let alone multiple coats.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Personally I would stitch together and and fillet first.
    You want the outside fiberglass to cover the entire hull at one time, no breaks at the joints. It will make a stronger joint.

    Many people will not precoat the plywood at all before applying the fiberglass/ epoxy. Make sure any exposed grain is well coated since that is the only place the epoxy will get sucked up a lot. Be sure to sand the outside joints smooth and round them, glass does not like to lay down over sharp corners. Also sand the edge of the tape to where there is not a ridge, same problem with the cloth laying down.

    If you have epoxy coming thru the joint, don't worry, just sand it smooth. Epoxy bonds to epoxy very well.

    My suggestion again is to not coat the plywood (especially not twice) the epoxy goes thru the cloth very easily. I have done 4 boats this way (called the dry method) and have never had a problem with the cloth not being fully stuck.

    The good thing about the dry method is that it is easy to position the cloth and get it smooth before you start epoxying. When you coat with epoxy first and then apply the cloth it will tend to stick making it hard to get on evenly.

    Either way will work, but don't waste your epoxy on applying 2 coats. There is far more epoxy in the cloth which is what really prevents the water from getting in to the wood.
    Then you use epoxy with fillers to make it smooth, so that is another layer (I assume you are painting the boat not a clear finish).
     
  6. scotdomergue
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    scotdomergue Scot

    I agree. Coating with epoxy at this stage is just extra work, material and weight. Sand as needed, stitch and glue, fill any gaps/holes, sand to prepare for fiberglass, and use the dry method. That would be my approach. It's worked well for me. Once you've done the fiberglass you'll want to do a fill coat while it's still green enough to bond chemically.

    Not sure what sort of sander you're talking about . . . I've found that an orbital works well . . . The other types I've used are disc on a power drill which is very prone to making gouges, or belt sander which is great for shaping wood, etc., but I'd be afraid of digging too deep on what I think you're doing, so orbital seems good to me.

    Scot
     
  7. scotdomergue
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    scotdomergue Scot

    PS: no problem that epoxy comes through the joints as long as it is smooth enough. If you do the second side while the first is still green (which it will be after only 3 hours) it will chemically bond. If it's more fully cured, then sand and you'll get a good mechanical bond. If it's still at all tacky, then it's green enough to chemically bond, and probably still for a while after that (it should definitely still be soft enough that a fingernail will push into it enough to make a mark/slight dent).

    Hope it's continuing to go well!
    Scot
     
  8. WilliamPrince
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    WilliamPrince Junior Member

    Okay all pieces are done, too dark to have a picture, but they are ready to sew. Now, they are not all 100% accurate to the plans, but they are really damn close, I hope it will still go together as planned with minimal sanding/reshaping required. Tomorrow I will begin sewing.

    Unfortunately, I had to act quickly, and I applied the reverse side of the fiberglassing on a joint which had about 1 inch of cured run-through epoxy on each side, without sanding first. I hope that will not weaken the bond too much, theres not much I can do now. Well, the boat doesn't have to last long anyways. Tomorrow I will have a full splendid day of work, and will hopefully finish the stitching!

    Ahh, another question. Pic showing the large framepieces, I did not yet cut any holes in them, as the instructions intended, thought being I have not yet decided the design of the inside of the boat... So I don't know where I will need to be reaching through. I guess theres not really a specific question here, I guess I just need to start designing the inside of the boat. Does anybody have any input on this? I will see if I can draw something up right now...

    Basically I need:
    - A place to sleep
    - A place to sit and sail/paddle/steer
    - Attachment for mast (I think I will need help with this... The mast will need to be well and secure)
    - Attachment for leeboards
    - Rudder assembly
    - Anchor assembly (am I even going to take an anchor? Wait... Surely I need an anchor)
    - Storage for heavy stuff along keel (water, cans of food.)
    - Storage for lighter stuff in the bow and stern
    - Some shelter from the elements, if possible.
    - Attachment for my outrigger, if I will use (I think I will use... Just for stability and safety... Thoughts)

    And I'm guessing I need to be able to bail out water, water will find a way in I feel sure of it.
     

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  9. WilliamPrince
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    WilliamPrince Junior Member

    Okay as I prepare to drill the first stitch holes I encountered a problem... My two mid panels are misaligned on the curve. One has about 1.5cm more camber than the other. They are perfectly aligned in terms of length, it is just the camber, which at it's largest discrepancy, measures about 1.5cm. Is this okay? Theres not a lot I can do, I think, but is it safe to go ahead at this point? How can I make sure that despite the difference, the boat will still end up symmetrical? All the fiberglassing came out very nice though, I am quite happy with it.
     

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  10. kerosene
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    kerosene Senior Member

    I don't know what you mean by camber. However if you have different shaped parts left and right - no way the boat will be symmetrical. Now you could shave the parts to match to make the situation symmetrical. That is not necessarily going to put you in much better place though...

    Did you sand/cut the parts so that you matched left to right?

    I would try some kind of cold fitting to see how the "smaller" piece fits. If it seems to fit ok, shave the bigger to match. I get that its probably not big vs small but a shift but maybe you get the idea.

    All this is assuming I am getting you right. Better explanation and photos would help a lot.

    Don't stitch before you clarify this issue. That means also don't drill the holes for zip ties yet on the edges that are suspect.
     
  11. scotdomergue
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    scotdomergue Scot

    You might try stitching it together to see how it all fits and how badly out of alignment . . . that might show you what adjustments would make sense . . .
     
  12. WilliamPrince
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    WilliamPrince Junior Member

    Okay I will try to explain the problem a little better. I put it together with duct tape to see what it looks like - will post that in the next post (still can't figure out how to attach multiple images, I don't think it works with my phone).

    So the problem lies within my two middle panels, mostly in one of them. Essentially, the panel in question has a more pronounced arch than it should, curving up to 1.5cm above the correct position at the highest point. I'm not sure exactly how this affects the hull - as you can see in the picture in the post below this, the hull still goes together. Just because it goes together though doesn't mean it is going together correctly... There is definitely some problem here.

    I have made a video describing the problem which can be watched here: http://youtu.be/DFI0SqROxQE
     

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  13. WilliamPrince
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    WilliamPrince Junior Member

    Here is the hull, seen down the keel, put together with duct tape for now. My last upper panel is still drying, when it is done I can put it on to see how it all looks.
     

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  14. scotdomergue
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    scotdomergue Scot

    Looks pretty good.
     

  15. WilliamPrince
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    WilliamPrince Junior Member

    Do you have any input on the mistake? I just got a comment saying the discrepency wouldn't really matter too much... Do you think it would be safe to just go ahead and stitch er up?
     
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