Newbie asking for advice

Discussion in 'Multihulls' started by jmoropeza, Oct 17, 2021.

  1. jmoropeza
    Joined: Oct 2021
    Posts: 16
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    Location: Mexico city

    jmoropeza Junior Member

    Thank you very much for your reply Mr. Woods
  2. jmoropeza
    Joined: Oct 2021
    Posts: 16
    Likes: 1, Points: 3
    Location: Mexico city

    jmoropeza Junior Member

    Wow! Thank you very much for your answer and your generous offer Rob!
    I'm pretty sure I'll go for a Richard Woods Gypsy. I whink is a good compromise between price, sailing characteristics, speed and building time.
    I would love to go for rouded bilges but since is my first build and my first time using infusion, i think i'll go for flat sandwich core panels to minimize my possible errors.
    I have contacted Utek and they quoted me $25.92 per P80 1080*1000 sheet delivered in Mexico. What do you think about that quote?
    I have many questions about infusion and i would love to ask you and guzzis3 about some details. Since english is not my mother lenguage, sometimes i have a hard time following the technical terms. Don't know what kind of epoxy use or if it recomended to use vinyl with infusion? What's the right epoxy from Utek for my application? The right ammount of vacuum components for my build? and so on.
    Again, thank you very much, i'll research more about unstayed masts and shunting.
  3. jmoropeza
    Joined: Oct 2021
    Posts: 16
    Likes: 1, Points: 3
    Location: Mexico city

    jmoropeza Junior Member

    Thank you everyone for your answers, I realy appreciate your time and availability to share your knowledge with me.
    I'm pretty sure I'll go for a Richard Woods Gypsy since it has a good balance between size, specs, speed and building time/cost.
    The only two factors that i have doubts is about the central cuddy without internal access to the hulls and the type of bilge i should choose.
    I have made some numbers and definetly marine plywood is a no go for me. I'll go for sandwich core with Strucell P80 (same structural data than Divinycell) using resin infusion and flat panel construction.
    I'm just at the begining of this journey and have alot to learn and research, so if you don't mind, i'll continue asking questions.
    Thanks again for your answers and time.
  4. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    Let me restate that I don't care what you decide. All I care about is that you are happy with your decision.

    The cost and time to build is proportional to the weight of the boat provided you use the same materials and it is a fairly efficient build.

    Rob has refigned his built method and designs so they are very efficient.

    I personally don't like proas, but then I'm not that keen on trimarans either. This is personal taste.

    There is nothing wrong with any of them provided you build a "good" design. There are examples of all types which are less great boats.

    Those designs are best avoided.

    You said you can't get ply so I mentioned foam. Utek can supply everything you need, foam glass bagging materials, sealing tape spiral tube etc for vacuum bagging.

    They do resin but it might not be economic to ship.

    I don't know anything about mexican ports and borders. Enquire at a shipping agent to find out what things will cost.

    With foam build the 300 gsm scrim is to aid the panel making. It's not required structurally. Without it the glass can bunch up and move around.

    It depends on how you decide to build what materials and techniques you use. The $ difference is small. The cost of infusion materials is small.

    It's the foam that makes up the bulk of the cost. Having said that if you buy as much as possible from UTEK it will bring the materials cost down a lot.

    None of this will affect the cost of rig, motor and other fitout. All those are more decisions you have to make along the way.

    Gypsy is a good choice. Dory or round hulls don't really matter much. Foam may have a better resale if you decide to sell it on.

    Work out what you want to build first than look into the build choices. Whatever you do good luck. Ask questions, people will help.
    Will Gilmore likes this.
  5. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    It is really fast to use tortured ply to build a whole hull versus building a panel at a time on the infusion table.

    I was comparing wet bagging panels to glassing a whole plywood hull.

    You are comparing infusing panels to glassing a whole hull. Your method is certainly better, but panel work is always slower.

    can you expound on the cabosil comment?
  6. jmoropeza
    Joined: Oct 2021
    Posts: 16
    Likes: 1, Points: 3
    Location: Mexico city

    jmoropeza Junior Member

    Yes guzzis. I'll go for Foam core and infusion since is the most efficent method as far as i've researched. I've contacted Utek and they give me a great price so I'll go with PVC P80 at least. I will have to purchase the plans to see about the exact requirements for the build.
    You are right about the decition of the boat, I have many questions and doubts and it's a fine balance between compromises.
    About the weigh/building time. Yes it's a huge factor but i'm conciouss of it and i won't be able to speed build since it's not the same earning in dollars or pounds than in mexican pesos, so even if i want to speed up, it will take some time, but even in that scenario i have to balance motivation with building time.
    Thanks for your advice
  7. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Senior Member

  8. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    This might be correct if the designer simply replaces ply with infused panels. ie "The boat is designed for ply, but you can also use foam/glass, infusion or bagging". If the job is designed for infusion by someone experienced with the process, it is no contest in terms of speed, cost, weight and safety.

    For tortured ply, building frames have to be cut, erected and levelled. The ply has to be scarphed, resin coated, drilled, wired and spread; the keel poured; stringers and gunwhales added, bulkheads, deck frames and deck cut, resin coated and installed; all raw ply edges treated; doors built and fitted into frames; window, hatch, beam and mast holes cut; extra material glued into high load areas then the whole shebang sheathed and faired.
    Intelligently Infused panels require an airtight, flat table. The panels are laid out full length with the joins and most of the stuff mentioned above included. It is then infused. When cured, the pieces are glued together.
    Wet bagging panels instead of infusion combines the waste and contact with dangerous chemicals of wet laminating with the anguish of getting everything under vacuum before the resin cures. Similar to plywood over frames and stringers, it is out dated technology. But without the ??? of working with wood, spending days in a hazmat suit, gloves and mask expending a lot of energy turning expensive toxic materials into dust to make a boat look like a piece of furniture.

    It's not. On the cargo proa, a couple of students set up, infused and demoulded a 12m panel in a relaxed couple of days with the result being a quarter of the hull. Prepping, fairing, glassing and filling a 12m hull would take longer, waste more materials and require a lot more exertion. And require the hull to be built first.

    Sure. In simple terms, Cab-O-Sil (colloidal or finely ground silica) adds very little bulk to the epoxy, and barely changes the strength. Microspheres/Microballoons/Microlight are tiny glass/phenolic/plastic balls which displace the resin, increasing the bulk, reducing the density and the strength.
    If you are going to glass a bulkhead in, the glass is doing all the work. Similar, but different to the glass on a cored hull or the flanges on an I beam. All the fillet has to do is keep the glass from being bent out of shape and ensure the transition from one surface to the other is smooth. The lighter filler material fillets do this admirably, as would foam. Depending on the resin, the temperature and fillet size, you should add a small amount of colloidal silica to the mix to increase thixotropicity, or the tendency of the resin to drain out of the mix or slump.
    Glassing fillets is usually overkill. If you run fillets along a join between 2 pieces of material, leave it to cure, then break it, one of the pieces will break before the fillet. As the bonded pieces get bigger/thicker/stronger the fillet should change from light filler to cab-o-sil then increase the diameter. Rule of thumb for ply is thickness of the material equals fillet radius. 9mm ply, 9mm radius fillet. Foam and light glass a little larger due to localised crushing.
    Bulkheads etc which are held on two, three or four sides need even less to hold them in. Try kicking out the bottom of a filleted box, or twisting it to destruction. The material will break long before the fillets. Bunks, shelves, furniture and non structural bulkheads need even less to bond them in. Infused foam panels have the edges glassed. This is sufficient surface area for glue in a lot of cases.
    Tests such as these (and many others) should be done by builders to give them a feel for their materials and boat strength.
    Designs which over spec materials often indicate a designer who has not done enough testing or believed what his materials sales rep tells him. If the designer asks the rep for advice (engineering, boat design, etc) which the rep is unqualified to give, the rep over specs to cover his arse. He would be foolish not to. The solution is for the designer to pay a lot of money to an engineer or do a lot of tests himself.
    Equally bad is copying what everyone else does, the 'industry standard'. This always results in overkill as 'the industry' assumes that a poor build quality or misuse of the end product is 'normal', so increases the spec.
    When I started selling materials in 1986, <30' multis were built from 6mm/quarter inch cedar with 200 gsm/6 oz glass either side. Some of these boats are still sailing. Now, the standard is more likely to be 12mm with 600gm/18 oz glass outside and 400gsm/12 oz inside. The result? Heavier/bigger hulls, rigs, rigging and motors. And loads. So some break, resulting in the next generation having 600 both sides.
    Don't get me started on generic standards and scantling rules....

  9. jmoropeza
    Joined: Oct 2021
    Posts: 16
    Likes: 1, Points: 3
    Location: Mexico city

    jmoropeza Junior Member

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