resin infusion foam scored one side

Discussion in 'Fiberglass and Composite Boat Building' started by guzzis3, Mar 18, 2018.

  1. guzzis3
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    guzzis3 Senior Member

    What you choose depends on what you want to do with it. My intention is to build the Richard Woods Wizzer design, modified, although I have second guessed myself a few times. Probably Eagle would have been a better choice, or Skua.

    I want a boat I can cruise the queensland coast, but it must be trailerable. Our coast is mostly calm due to the great barrier reef and I have no interest in crossing oceans. The weather is always warm to hot here so exposure is not a problem. It needs to be small enough to sail alone and I want some accommodations. If you have an open deck cat with a flat bridgedeck you can pitch an ordinary tent which are cheap and light, but I want a permanent heads area and ideally a standing headroom shower. Finally we have a lot of very shallow water so I'm not so keen on daggerboards.

    The important thing is to decide what you really want, then build the minimum boat that does that.
     
  2. VadimGo
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    VadimGo Junior Member

    True words, as if you do not know what you want, nobody can help you...

    I would love to see what are you coming to, both as a accommodations and trailerability, so I can learn something.
    Wizzer was aiming at a racer, wasn't it? So you are starting with a sleek bottoms, and add some keels (thats a curious take on a shallow draft) and a top to accommodate a standing room in the hulls?
     
  3. fallguy
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    fallguy Senior Member

    Learning infusion is really the way to fly.

    I am doing wet bagging and it is pretty tough and the results are a bit less than what I desire with a potential for starvation and high epoxy losses.

    All good boat work requires testing. This is no different than learning infusion.

    Break new ground and build a Woods Cat using infusion. I'd try a dev panel build if he has one for sail.

    My build is coming along slowly. I hit a bump in the road and need a hip replaced, but we are making good strides anyhow.

    caveat: I don't know if anyone else has done it, but I haven't heard about it
     
  4. fallguy
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    fallguy Senior Member

    Oh yeah, wouldn't daggers be a lower draft vessel?
     
  5. guzzis3
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    guzzis3 Senior Member

    I guess you read my previous post and assumed I was substituting LAR keels for daggerboards. I am in fact going to have either centerboards or leeboards. Each option presents problems and advantages, I am sure anyone familiar with catamarans knows what these are.

    Eagle is a flat panel boat which can be built in foam, as can gypsy. The problem with gypsy is it has wide hulls which would fit on a trailer but leave not enough room for the central lifting platform. It is also a much heavier boat, 1800 kg empty, which makes trailering tricky. Wizzer has slimmer hulls, 900 mm/3' and I think it and sango are really attractive. Making the curved hulls using infusion is tricky, but then taping flat panels together and achieving fair single curves everywhere can also be tricky.

    So as I say choosing a design, choosing a build method, choosing other options like keel type, each option has advantages and problems.

    Right now I am working on the engineering of the trailer. It has proven to be more difficult than I thought. The mechanics and spatial relations I had sorted in my head, but to build a structure which is stiff and strong enough to carry a 1400 kg (loaded) catamaran with a safety factor but which isn't ridiculously heavy and complex to build is a tad tricky.
     
  6. fallguy
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    fallguy Senior Member

    I had not read the other post.

    I, too, want a trailer for the Skoota.

    The best idea I have thus far is to use linear rails to move the hulls.

    In order to build with dev panel; you could do like I did and get some female jig cnc'd. But you would use infusion. It works nicely.

    My hulls are very close in shape with some deviations at the bow. I made a chain jig to get the bows the same, but have an odd curve here or there that I will live with.
     
  7. guzzis3
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    guzzis3 Senior Member

    I meant the post above where I say I don't want daggerboards.

    People have done the telescoping trailer many times before. The big problem with them is if the hull skews slightly as you pull it out the mechanism jams, locks up, and it's a devil to unlock. I am planning on using swing wings. If you have seen the floats on a dragonfly trimaran it's a mechanism like that. The trouble is hanging 700 kg (1500 lbs) off a pair of 1500mm (5') arms isn't trivial, and I'm trying to keep the trailer weight to 600 kg or less. I had hoped to use C section steel but it looks like I'm going to have to use a space frame.

    The mould isn't the problem with the hull sides. I'm just going to make stations, strip over them in mdf effectively building the hull side in mdf, coat it in something appropriately slippery and that will be my male mould. The problem is getting the foam to lay flat against it so the hull side is fair when it comes out and doesn't need a lot of remedial work. I don't have enough feel for the foam to predict how much trouble that will be.

    Also I plan to have a go at making carbon beams and spars before I start on the hulls. I've got an aluminium mast I bought second hand but it's pretty heavy, 42kg including rigging. It would be nice to be able to walk the mast up.
     
  8. fallguy
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    fallguy Senior Member

    08B772A5-F5E9-4FB0-93C4-E3059E752631.jpeg What is the advantage of a male over a female mdf mould?

    In the female, the exterior is against the mould surface and you can at least in theory get a better surface.

    Or with a table; you can use a female jig like I did. The only places I had trouble were setting up the forward jig sections (milled at 90s) and getting the dev panels to behave forward. I was stingy on screwing the hull to the ribbands, but the method is decent. What I really liked was getting my bulkheads installed level. I just did some adjusting and everything was within 3 millimeters bow to stern which is basically my sharpie or laser line thicknesses.

    But I would strongly recommend using infusion on panels. Learn it and you'll produce a better part with lots less stress and less resin loss.

    The front of the hull bottoms were hand laid and it was very physically demanding in the narrow space. If done again, I might have challenged RW to make a nosecone instead of finishing just a bit short, but in his defense, I asked for a bit narrower hull.
     
  9. guzzis3
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    guzzis3 Senior Member

    Well as I said before there are choices at every stage and none are absolutely better.

    I am not building a flat panel boat, at least not at this stage, so I need to make a double curved mould. I'm planning to build using resin infusion. If I use grooved foam to carry my epoxy I decided grooves one side are better as I can flood the invisible side first and let the perforations carry the resin to the visible side. That is a hopeful strategy against dry spots on the invisible side. Trouble is those grooves will print through over time so you either get that on the inside where it's pretty invisible or the outside and what some might consider an ugly boat.

    However I might use a carrier layer and only perforate the foam. But a male mould offers another possibility. I was planing to build the strongback from mdf as a box. Very stiff. It should then be possible to mount that on a couple of engine stands. I could set up the hull side laying flat then rotate it vertical, introduce the epoxy at the bottom, have the vacuum drawing from the top, use gravity, and a tap on the resin supply to ensure the hulls side is properly flooded.

    A male mould will make this easier, and I can see how fair the outside will be once I've pulled the vacuum. A female mould is bigger, harder to access inside and hides the outside skin.

    For hand layup of a foam hull I accept absolutely that a female mould makes more sense, but with infusion I can't screw the foam to the forms. Once the vacuum is on I need to look over the hull side and satisfy myself it's all fair, otherwise I let go the vacuum and make changes as necessary. That is a great advantage to infusion but like everything it comes with problems.

    That's my plan anyway....

    How did you get your panels to sit out hard against your forms? I wold have thought you would need to use bulkheads to push them out, or did you screw them ?
     
  10. fallguy
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    fallguy Senior Member

    Screws. It is disheartening to puncture the hull. Look close at the picture the wood pads have screws.

    I did the first hull by only puncturing at tape seams and the second I kept the tape seams free and I regret that. Much better to screw when possible in a location later getting tapes.

    The bulkhead dimensions were not true enough as drawn to use in the fashion you suggest. Further, I would be concerned a bulkhead fitting tight would transfer its shape to the exterior.
     
  11. guzzis3
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    guzzis3 Senior Member

    Right.

    I also meant to mention a male mould should be easier to fair. As I say I have to essentially build a hull side in mdf then lay the foam/glass against it, so it's different to just cutting stations and running stringers. (we can get damaged mdf for $5 a sheet so it's by far the cheapest way to build jigs, sometimes it even has a melamine side on it.)

    I am lucky enough to have access to 3D mechanical modeling software so I'm modeling everything up and checking it all before starting. In theory it will be mm perfect but theory doesn't always translate to reality :D

    If building chined I had thought making male stations, bending the hulls sides around them and using sticky tape to hold it all in place, filling the joins with structural adhesive then removing the tape, sanding and glass taping from there. Again nice theory. Don't know if it would work. Chined is much faster and easier to make the panels but with the curved hull there is only one join down the centerline. It would be interesting to make 2 otherwise identical boats and log times etc.

    I assume you are fallguy1000 from the woods forum? You are building a skoota 32 ?
     
  12. fallguy
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    fallguy Senior Member

    Yes.

    The male station idea is a bomb. Was heavily discussed here as a preface to my build. The problem is the male stations required staying in place during the flip. So I went female.

    And it worked well.
     
  13. guzzis3
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    guzzis3 Senior Member

    That's interesting. So the hull won't hold it's shape once the panels are joined, until it's fitted out ?

    In theory I could chicken out and build my boat off the flat panel lines of the ply sango hulls, but I'd prefer to try for the knuckled hulls.
     
    fallguy likes this.
  14. fallguy
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    fallguy Senior Member

    Yes, the bulkheads need to be at home. I will find the thread here for you.
     

  15. fallguy
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    fallguy Senior Member

    Reread this thread. It wanders and weaves as I try to explain building on a male jig and I finally adapt to full female.

    Richard's original spec was for a female half mould infusion.

    Also a floppy beast. When I come out of the jig; the hull had no deck shoe, but is solid. The deck shoe could be completed, but also changes flipping and bottom work.

    A couple of ideas for improvement would be building a nosecone. It would avoid the trickiness of working in the narrow space. And limit screws not in tape seams.

    Traditional Build with Corecell https://www.boatdesign.net/threads/traditional-build-with-corecell.57580/page-2
     
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