Alternative framing for discussion

Discussion in 'Boatbuilding' started by 2farnorth, Jul 21, 2009.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I based my comments on the basic nature and general understanding that I gather you may have. Reasonable engineering understanding, that would cause these types of questions to be "self evident" was not forth coming (apparently), so it could be assumed you didn't understand why.

    With this in hand, it's clear you have some studying to do. I would start with the basics in volumetric calculations, get a handle on the math there, then onto design theory and engineering fundamentals. This way you can be fairly sure the boat will float where you'd like and not break in half on launch day.

    This isn't an insult, we all start at this point. You have two choices, give up or carry on. It's a lot easier to have these types of discussions, when you have a better understanding of how things work. There is no sense in designing a boat, that doesn't come as closely to your goals as it can. Floating, with the decks facing up and about where you painted the waterline would be a nice beginning on launch day, don't you think? 40' electric propulsion requires a very efficient hull form and some very clever engineering to pull off with any success. A novice has absolutely no chance.
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Hi 2farnorth - apex1 is a bit liverish this week because I have been 'examining his assertions' - but he, and all the others are right on in this case.

    Expanded foam itself is a problem, as it takes up water (unlike slabs of marine foam).

    Compared to plywood, foam and PVC are not cheap. You can get a lot more value out of ply offcuts as ribs than foam and PVC.

    If you wanted to do a plywood shell with hollow frames, you would be better off leaving them empty( but draining to the bilge), and you could use heavy plasticised cardboard as a former for fibreglass.

    My experience is that there are some pretty damn efficient and optimised plans out here for plywood stitch and glue, and you will be hard pressed to make any savings of real value.
     
  3. apex1

    apex1 Guest

    You may examine my assertions, til the cows come home mate, I do´nt bother.;)

    Right the next one here:
    Hollow frames are a mad idea! Whenever possible they are avoided in all shipbuilding industry worldwide. A simple plywood frame in this case, adds the same or more strength (if profiled) than a tube, at less weight and less trouble.
    Just forget about any tubed framing.
    Regards
    Richard
     
  4. 2farnorth
    Joined: Oct 2008
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    Location: Stillwater, Mn, USA

    2farnorth Junior Member

    I am an a..hole because why? I compliment you on your work on your public profile and I am an a..hole? You are abviously a proffesional when it comes to boats but a novice when it comes to actual human interaction. Maybe you need to start a forum only for professional designers and builders who allready know it all, such as yourself.
     
  5. apex1

    apex1 Guest

    Who said that? You named me that way! I wrote: Your a..hole (comment) ..understandable. Calm down and try to understand comments not as a personal offense, especially not when made the way I did.
     
  6. 2farnorth
    Joined: Oct 2008
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    Location: Stillwater, Mn, USA

    2farnorth Junior Member

    Sorry I misunderstood your comment Mr. apex1. Thank you to rwatson, par, eric and daiquiri for informed professional opinions. I am not set on building with any materials in particular, just exploring everything out there. To PAR: I do realize I am not ready to design a boat. I just have an active mind that that questions most everything. I will be deploying to the Midle East in a few months so I will bring some design books with me for my down time.
     
  7. Guest625101138

    Guest625101138 Previous Member

    For a light weight one-off build it is hard to beat flat panel construction using structural foam in a fibreglass sandwich. Go to carbon fibre if you want to go as light as you can but it will be more expensive of course.

    One big feature of foam panels is that you can buy factory produced panels that have good quality control. It overcomes some of the quality issues of normal hand layup. Even if you make panels in the local workshop you have easier and better control on the variables than a normal hand layup over a shell.

    This thread shows the progression of a build using end grain balsa cored factory panels:
    http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962-7.html
    It goes on for pages but you get the idea of how the factory panels arrive and how the boat comes together.

    Some designers are very clever the way they get the panels to fit together.

    This blog shows home made CF panels:
    http://www.adventuresofgreg.com/HPB/2009_04_24_archive.html
    If you work through the blog you will see the boat coming together. The boat is 8m long but quite slender. The formed hull without fittings is only 54kg.

    The weight of some of the modern catamarans and trimarans built using this technique is incredibly low. Forty foot hulls that weigh 200 to 300kg.

    It is worth your while to get some experience with this method if you have a build in mind.

    On this page #295 and #296 I show a small boat I built using CF over 3mm Klegecell. The main hull is 6m long and quite slender:
    http://www.boatdesign.net/forums/boat-design/pedal-powered-boats-23345-20.html
    As noted the actual work was 38 hours. The hull weighed 11.5kg after painting. It is much firmer and more durable than a typical kayak hull of that weight.

    This is a proven technique able to give good results for novice builders who are prepared to take the time to do it well. Playing around with unproven methods, even with cheap materials, can be very wasteful. You are developing the whole thing from scratch and you will not find a designer prepared to check any calculations you might make. Without this it will probably float but you will never have confidence in it. Also do not underestimate the weight of expanded foam even before it becomes waterlogged.

    Rick W
     

  8. 2farnorth
    Joined: Oct 2008
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    Location: Stillwater, Mn, USA

    2farnorth Junior Member

    Thanks Rick. I looked at a few pictures on that Oram designed boat build down under. I will check out the rest when I have a little more time.
     
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