Building with Duflex or similar panels.

Discussion in 'Fiberglass and Composite Boat Building' started by Steve W, Feb 13, 2016.

  1. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    I have read a few threads where folks have built catamarans from duflex kits. I would like to expand my knowledge on this build method. There are a couple of things that come to mind that I am unclear on and have not found in the threads I had read so am hoping someone here can clarify for me.

    1/ When you receive the kit do the panels have the full laminate schedule in and out requiring only filling and fairing before primer or does the boat require additional laminate after assembly?

    2/ Does the Z joint require any additional glass on each side or is it or is it all that's needed?

    3/ Is there additional laminate on the bottom panel to protect the balsa core from damage should the boat settle on something sharp when beaching.?

    4/ What is a typical laminate schedule for joining the panels at the chines etc?

    5/ Anyone know how the panels are made, based on Bob Norsons rather dry panels with lots of pinholes I'm guessing press molded , I cant find a description on ATLs website but I'm thinking that would be the most practical way when making a lot of panels. I don't think infusion would lend itself as well to production but I could be wrong on that.

    I'm sure I will have more questions but these are a good start.

    Thanks in advance ,

    Steve.




    I'm sure I will have other questions but these will do for now
     
  2. waikikin
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    waikikin Senior Member

    Best talk to this bloke, http://www.cruisersforum.com/forums/members/44'cruisingcat-3477.html probably not unbiased but has a very successful 44' build and also a rebuild to as new behind the opinion.
    Aside from that my biased opinion from 1980s apprenticeship in ship & boatbuilding rates the panels as resin starved and lacking in the biggest advantage in composites... the contact molded white glossy gelcoat, both methods will get you a good boat.... but via different paths.

    BN hold some bias as well but takes the extra effort of acheivement of end result somewhat personally, the marketed panels do the job, they do need extra effort, from the start they were described roughly as 85% as strong through the Z joints but equal in stiffness the critical factor apparently.
    Boats have been designed for use of panels finished laminate.
    Z joints as above, I believe they can match design requirements to order.
    Additional laminate would be at designers and builders discretion, maybe not "nessesary" but sandwich laminates need to be matched inside to out also, maybe a good idea but resin/screed and paint do keep the h2o out.
    Panel joining would likely be matched to panel laminate- nothing bad about some edge tapering to panels and subsequently to join tabbing but a little wider.
    Not sure how they make them but some press & uv or heat kick off would get them through to a profit... infusion or wet preg and waiting probably wouldn't.

    The panels with good design will get you a great boat, every FRP boat needs sanding and grinding... treat it like a job of work that needs to be done and you will get through unless allergic to epoxy.

    All the best from Jeff.
     
  3. groper
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    groper Senior Member

    The process idea/mandate is to reduce labour using prefabricated, perfectly flat, structural panels for generally 1 off constructions as production environments lend themselves better to contact molding - as per waikikin above noted. Certain design constraints which detail efficient design elements such as strategic unidirectional fiber concentrations ie. Beams/spars etc -are stipulated by the yacht designer and are generally added by hand or local infusion to the assembled duflex frame. General hull panels generally dont need any additional laminate beyond the taped seams.
    not for general panel joining like hull topsides and general exterior paneling etc but again depends on the panel design and what the yacht designer needs to acheive structurally with that panel - sometimes main bulkheads etc will need the z-joins taped over.
    thats upto the designer, owner, and builder to discuss and the boats owner/operator requirements.... some boats are never designed to be beached... other people like "the warm fussy feeling" they get from knowing they have a massively thick and heavy fuel guzzling hull which will protect them from damage should they hit something in the water.... yet others are bound by class society and/or survey regulations and stipulated minimum hull thicknesses... insurance plays its corrupt part in that too :p
    again design related, but TYPICALLY use 150% of the panel skins laminate.
    They are not infused... the rolls of fiber are prepregged, laid up, and then cooked in a heated plate press - 10min bake, pop it off and lay the next etc...
     
  4. Steve W
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    Steve W Senior Member

    Thanks for the info guys, I don't have any intention of using duflex panels myself but I find it an interesting method of construction. As a professional boatbuilder since the early 1970s with a decade of that time spent out of the industry as a patternmaker and as a snowboard manufacturer I am always looking to expand my knowledge. In the ski and snowboard industry press molding is how its done pretty much exactly as you describe groper. I'm thinking they are probably using an impregnator but perhaps prepreg. We built all our own presses and it would be no problem to build a press to do 4' x 8' sheets but personally I would prefer to use full length infused panels with no vertical joints and a duratec primer in mold surface finish as you suggest Jeff but of course that is not possible in a kit scenario so the duflex panels seem to be a very good solution.

    Steve
     
  5. groper
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    groper Senior Member

    Yes- they use an impregnator as you said... it essentially ends up similar to building with ply wood in terms of build process with the z joins as an added benefit compared to scarfing the ply to make large panels, and of course the CNC routing of the entire set saves time too. The system is not as efficient for production building but certainly has proved it's worth for 1 off builds.
     
  6. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Hey Groper, congrats on the upcoming launch, the boat looks great.

    Steve.
     

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

    Steve,
    Private message sent.

    rob
     
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