Building hull in cross sections

Discussion in 'Multihulls' started by SmallSpaceBigImagination, Mar 22, 2021.

  1. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    For what it’s worth this “happy wife happy life” thing is BS. Men deserve their rewards too, it’s a two way street.
    And, I think you’ll find there is a respect gained from standing your ground. Enough said.
     
  2. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    Ok so there's a few issues above.

    There are lots of cheap boats around. Glass seems to last forever unless it's balsa cored, badly built/designed in the first place or ancient (60's or 70's), the time when they were still working things out. As I said previously I'm a metalworker by trade and mech eng by profession. I wouldn't buy or build a metal hull in a fit. They have their place on monohulls but not multis. Any boat you buy second hand you need to know what you are getting. Get a survey or an expert to run an eyeball over it. If the hull is sound do a careful assessment of the add ons. Don't pay for stuff you don't want, don't pay for stuff that's worn out or useless.

    Often a "deal" isn't on close inspection.

    A 30' power cat can easily have 6' headroom everywhere, 2 private heads probably with 6' headroom and space for a shower. And full size doubles, a decent galley etc etc.

    Look at the weight of the boat. That is the rate they cost to build, renovate and usually buy. a 40' boat is not 1/3 bigger than a 30' boat, it's about 4x as big. A typical 30' motor cat might be 15' wide. That's 450 sq ft of mostly accommodation. That's about the size of my 1 bedroom house. How much space do you need for a couple ??? You said you wanted 2 heads. Do you want a laundry aswell ? It's doable but it required space and most of all plenty of electricity and fresh water.

    If you build you might spend 2000 hours per ton of boat. That varies wildly for all sorts of reasons but take that rule of thunb and ask yourself do you really want to do this ? It's ok if you do, just be sure.

    The thing with a motorsailer is it's a motor boat with the option to sail if you feel like it. That costs extra. Everything costs extra. The real question is is it an option you want and am prepared to pay for ? I love sailing for it's own sake. The other experiences are a bonus. I would not sail if getting to the destination was the point.
     
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  3. SmallSpaceBigImagination
    Joined: Mar 2021
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    Location: Toronto,Canada

    SmallSpaceBigImagination Junior Member

    Have no fear, my wife is om board as long as there are 2 toilets. If we stayed together after 2 kitchen renos and a full basement apartment build ---for which I stubbornly refused to let anyone but us do the all of it -plumbing, electrical, drywall (which is my only candidate for a subcontractor next time!)... I may be naive but I think we'll be fine through a boat build

    I came across this article The use of structural methacrylate adhesives in the bonding of thermoplastics and composite materials - Materials Today https://www.materialstoday.com/composite-applications/features/the-use-of-structural-methacrylate-adhesives-in/ which seems to say the bond created by the adhesive matches glass sections and the glass would delaminate before the adhesive broke. I know most of you aren't likely to be marine engineers... So just looking for a sanity check. If i cut the foam core in 1/2. So a 1 x 6 inch foam core plank becomes 2 - 1/2 inch x 6 planks and glass 1 to the end of a section on the outer hull and a second plank to the abutting section on the inner hull would i not be able to adhere the 2 planks back together? Obviously removing enough core to accommodate the glass thicknesses. I can then be careful with my joints and fit out so i can reach the inside joint to glass a foot patch over it when joining the sections.

    If i were to take this idea to an engineer or architect would i be laughed out of their office?
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you were stuck in Gilligan's Island, the plan would be worth looking at. Forcing yourself to work in a space that is too small for the project makes no sense unless the goal is to break a world record of get bragging rights. It will cost a lot more in time and money. You will be better off renting space when you are ready to build. Meanwhile, you can fabricate all the interior cabinetry, hardware, etc. in your garage.
     
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  5. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    I'm a mechanical engineer, or was. Last year I had a couple of strokes and am now half blind and mentally impaired, so take this for what it's worth.

    Joining foam glass or solid glass hull sections is trivial. Been dome a million times. The problem isn't structural. There are a few tricks. Here are some examples of what to look out for:

    If you paint to the join you will have to expose that again ie no paint to get a proper bond.
    Epoxy is chemically durable but vulnerable to UV, so if you store your sections outside you need to block the sun. Don't paint. Either use another coating that can be removed or cover the sections somehow.
    Poly/vinyl esters are not glues. They are UV resistant. They bond to themselves. They don't bond to other things. I don'rt know a lot about the limitations of this so either ask someone who knows (redruben) or make your sections in poly/vinyl and do the joins in epoxy ? Anyway it's doable you just have to ask someone who knows better than me how to manage that. It won't be a big deal if you sort a procedure. If you just suck it and see it might fail. You don't need any oher product. People make sections then bond them all the time. Joining sections lengthways is unusual but it's no different to joining hull halves or hull deck/cabin.

    That glue you mention might be too brittle for a boat hull. I'm not sure what you are describing with your joint. It doesn't matter. Just either break the hull between bulkheads and tape the skins together or break it at a bulkhead and use 2 bulkheads. You can probably make each one with half thickness foam. Put epoxy on the mating faces and tape the skins together and it should be good enough. If you settle on a design ask the designer and they may have a a better solution. I would glass both faces of both mating bulkheads. Gives you a nice surface to glue.

    Sailing Catamarans - Skoota 36 comfortable live aboard cruiser or day charter http://sailingcatamarans.com/index.php/designs-2/6-powercats/265-skoota-36

    That hull will cost maybe 13k australian plus plus...

    Does have 2 bathrooms. Should be buildable in sections. Inconceivably big to me but each to their own.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It has probably been covered somewhere in this thread, but space to store the sections has to be arranged, and as it will take quite some time to do them all, you have a sizeable space over a sizeable time. That has to be a "sizeable" problem.
     
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  7. SmallSpaceBigImagination
    Joined: Mar 2021
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    Location: Toronto,Canada

    SmallSpaceBigImagination Junior Member

    Thank you guzzis3. I was looking for confirmation that it's not impossible... Appreciate the advise!
     
  8. SmallSpaceBigImagination
    Joined: Mar 2021
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    Location: Toronto,Canada

    SmallSpaceBigImagination Junior Member

    Makes sense. The goal was to spread it out in smaller sections amongst friends/family. If they can't store it, then easier to find storage for a smaller piece than trying to find a large storage unit in this area.
    I do realize that I'd have to find a place large enough to put the pieces together in the end.
     
  9. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    It is not impossible, but will take a lot of time and money to do it like you propose. The budget is painfully insufficient to accomplish it. The custom design alone will take most or all of your budget.
     
  10. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    Why would he need a custom design ? The scooter 36 could be done this way, it will just be really fiddly.

    It doesn't make sense. Renting a shed makes more sense, but really building a boat makes no sense. If I could find a freedom 8 or similar I'd snap it up and not build, but the fact is there is nothing on market that will do what I want so I HAVE to build. But if there IS a second hand boat that ticks your boxes buying that is the sensible thing to do.

    There is nothing sensible about building a boat, but then there is nothing sensible about sailing full stop. Just book a cruise...

    So logic really doesn't come into it. If he wants to build a 36' boat in a 10' garage who am I to tell him not to...I think the only time we should suggest people not pursue their ideas is if they are dangerous. The main danger here is wasting time and money on a boat that will never get finished. But it's not my call. He's an adult.
     
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  11. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Well said, I think. There should only be "bosses" in workplaces. I worked for one once who said "just agree with me, and we will get on fine". Perhaps it was a joke ? :)
     
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