Reference Material Question

Discussion in 'Fiberglass and Composite Boat Building' started by Rich M, Feb 19, 2012.

  1. Rich M
    Joined: Jan 2004
    Posts: 29
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    Location: Florida

    Rich M Junior Member

    I built a small boat and would like to make it in a vacuum bagged FG+carbon laminate and do not know where to look for reference material to learn how to do this build.The bottom is 36 inches of FLAT with two sides at 45 angles. Length is a tad bit under 10 feet long.

    [​IMG]

    Thinking about a 1208+mat layer, Carbon layer, and 1 more layer of mat, vacuum bagged with Vinyl or Epoxy. Will it be stiff enough for a 250# guy (me) to stand in without much flex? Does it need a core?

    Weight with plywood & FG is about 80#. I would like to get it down to 50-60# for my 70-something dad to be able to use.

    Don't know if vinylester or epoxy is better.

    All kinds of questions - can anyone suggest a good reference/starting point? Located in FL. Prefer reference to be simplistic if possible.

    Thanks!

    Rich M
     
  2. eguven
    Joined: May 2010
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    Location: Turkey

    eguven New Member

    Hi Rich,

    I am not an expert for boat building, but highly interesed about building my boat, I read lots of books and sources,

    Carbon fiber is an expensive material and it is very rarely used unless it is an hightech project desinged by serious manifacturers, it seem not somethig for amateurs like us.

    For epoxy vinilester poliester resins and fiberglass construction method I can suggest a book which has the answers for your question- The Elements of BOAT STRENGTH for Builders, Designers and Owners - by Dave Gerr. I have read the book and developed an excell sheet to make those of calculation in future, If you can provide the following information, I can calculate the laminate for you, but a confirmation from a Naval Architect may required. Hopefuly some good guys can help you for that part as well,

    If you provide following information I can calculate the scantling for you:

    LOA ( length over all)
    LWL ( length waterline)
    Beam ( the widest point of boat)
    BeamWL ( the widest part on water)
    Depth of sheer ( from deck level to deepst point of boat)
    Displacement (estimated total weight of boat, including equipment and person)
    Maximum speed

    and for construction method do you plan to construct with foam core, balsa core or single skin fiber laminate. Foam core is lighthest one.

    Cheers,

    Eguven
     
  3. tunnels

    tunnels Previous Member

    Can you explain where you got that lay up from ?? why 1208 and carbon ?? what do you hope to achieve doing it like that ?? :confused::?::idea:
     
  4. Rich M
    Joined: Jan 2004
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    Location: Florida

    Rich M Junior Member

    Thanks gentlemen,

    Eguven, Thank you - let me work on the various lengths - I will get back on that.

    Tunnels - I pulled the laminate out of the air. I built a one-off johnboat with 1208 and a layer of 3/4 oz mat and cheap ployester resin after seeing some guys use that layup schedule to build a flatsboat (I think they did a 1208 and a 1-1/2 oz mat). It was very tough but flexible. I don't see a 5 ft x 3 ft piece being stiff enough to stand on without a stiffener of some sort.

    The carbon is a guess - something to add stiffness without much extra bulk....to reduce any oil canning...probably try to do 6 ft where I would step and stand.

    My goal is a stiff but light weight boat.

    I did find some references but it is usually easier to work with someone in the know - to be pointed at beneficial references. What I've seen is that people with knowledge tend to hold it back, some cite liability concerns, others seem to feel that their hard earned knowledge is not to be shared. Some have shared before and been burned or abused. I can understand the reasons.

    With the gas going up I may not have the extra money to drop 500-600 into building this boat once I have the time this summer.
     
  5. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    You would definitely get a better result with a core.
     
  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Eguven, if you employ Dave Geer's scantling rules for this boat, it will turn out heavier then the current version and considerably more then necessary, if the goal is light, stiff and strong.

    If you employ carbon, you'll need vinylester, though you'd save more weight with epoxy. This is because you wouldn't need mat in a epoxy laminate, but you would in a vinylester.

    I honestly think you'd be pushing the envelop with a solid 'glass version of this boat, in regard to weight, though a core might address this, I still think you could build it in plywood for 60 pounds, probably less if well engineered.

    This said, if you went with a fairly high tech approach, using a high percentage of costly fabrics and core, you could get into the 50 pounds range. If you think good plywood is expensive, just cost out a similar strength and stiffness panel in these materials.

    The point I'm making is plywood will be a very difficult material to beat, in regard to weight, strength, stiffness and cost, pound for pound. Sure you could go carbon composite and sandwich construction techniques, but bring your wallet.
     
  7. Rich M
    Joined: Jan 2004
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    Location: Florida

    Rich M Junior Member

    Thanks, gentlemen.

    A few years back I tried to buy some core material from Bateau and the guy there told me to forget it, the boat (an 8 ft version at 55#) would weigh the same or more... LOL!

    I've never been very competitive but I can be stubborn when I put my mind to something.

    My understanding of composite building is extremely limited and I have much to learn before I attempt this. Spending some money isn't too much of a concern - providing I don't waste it. Looks like that is where the challenge lies.
     
  8. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Joel or Jacques over at Bateau was correct. Unless you accept considerable concessions in your solid skin or cored composite margins and/or employed some pretty costly, light weight materials, you'll (again) be hard pressed to beat a thin plywood hull, in these general dimensions. It's really fairly simple physics. The modulus and elasticity properties of the "usual choices", in regard to cored composites, have lower end limits. Simply said, you can only go so thin or so light, before you don't have enough modulus and elasticity properties values, to make the trouble (and cost) worth it.

    Simply put, you'll have to have some pretty fancy engineering if you expect to get a cored 'glass build much lighter then plywood, given the same strength, stiffness and margins, with a boat this scale.

    For example assuming you'll employ standard 6 ounce, 3K (6k would be a better choice), 12x12 carbon, off a 50" roll, you'll pay about $34 per yard, in the quantities you need. You might get a deal closer to $30, but a plain weave E 'glass will cost about $4 - $5 per yard. Kevlar will be about the same, possably more (ditto carbon) depending on material type, weight, construction, etc., which all make the cost of the laminate rise considerably. This said, I'm sure I can offer a laminate schedule that will get you under 50 pounds, if this is that important to you. The cost will rise, but it'll be strong, stiff and light, plus you can brag about your carbon/Kevlar composite racer.
     
  9. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member


  10. Rich M
    Joined: Jan 2004
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    Location: Florida

    Rich M Junior Member

    PAR, I sent you a private message.

    Thanks, idkfa. Serious looking panels.
     
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