non-cored fibreglass panels instead of ply

Discussion in 'Materials' started by Richard Atkin, Jul 13, 2009.

  1. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    The cabin lines look a bit awkward but I don't care because it has great functionality. The boat will look very good when you are sitting on it - nevermind how it looks from a distance. This is a party boat. Can be rigged much faster than any other trailer sailer. Less than 5 minutes with a few helping hands. VERY low centre of effort. Narrow BWL and centralised crew weight gives nice performance through waves and there will be no transom drag. This is especially important during California's notorious combination of light air and chop.

    Boat weight plus crew currently guesstimated at 1.5 tonnes but will probably end up being more. Performs very efficiently at 6 knots boat speed. Will be a very smooth ride. Very low freeboard to create a small boat feeling. Rigging is kept well away from children. Unsinkable with huge reserve buoyancy below central cockpit.

    This is my original design. Gary Baigent gave me some tips which led me to this design concept, but he might not like to have his name associated with it - but I am very grateful to him anyway. I will be taking this design to a NA when I am in LA for final calculations.

    Still not sure which materials I will use for the hull. :p
     

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  2. apex1

    apex1 Guest

    Hmmm, canoe shape hull, strong and easy made in strip plank, veneer. The superstructure looks alreaydy like ply sheets (and would be a perfect match if).
    So, why did you waste one moment in thinking of sheet material to make such hull?
    I do´nt want to talk you into any method, but this shape is easiest, cheapest and strongest (apart from exotic fibres) made of strip, veneer.

    And I completely disagree with your former statement that weight does´nt matter. That low freebord will not forgive overweight!

    (it seems you are very skilled in using Freeship)

    Regards
    Richard
     
  3. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    Has balanced transom hung rudder. Steering system uses large cogs for lower resistance.
     
  4. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    hi Apex. My only concern about ply is the fact that fungus eats it even when it is on dry land. I think I will have to make my decision closer to the time I commence the build. It might be a financial decision. I am waiting to see how far the American economy will implode before I move there!
     
  5. apex1

    apex1 Guest

    Thats a myth Richard! My boats would´nt exist if not! They are all just cold moulded plywood, completely encapsulated in Epoxy. There are cold moulded boats in service built during second world war (before Epoxy was available).
    A proper treated piece of wood / ply has far less issues than a perfectly made piece of GRP ! The flat panels you mentioned are worlds away from being just good, let alone perfect.
    In terms of maintenance you will hardly find another material that is easier to handle than wood / epoxy !
    And I never ever use the word plywood without meaning a fully Epoxy encapsulated material! That cannot rot, nor does it allow fungus to build up.

    Regards
    Richard
     
  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I can't tell much about that hull shape other then it being a round bilge, but panel construction on that shape, would prove quite difficult.

    You can have your cake and eat it too. I understand your desires for a durable hull shell, one that will not delaminate or rot it's core.

    If it was me, I'd build station molds, then space furring strips over this on fairly tight centers, say about 9". Over this I'd lay cheap foam, open cell crap stuff, just wire tying it to the firing strips. Once the whole hull was covered with this foam, I'd then cover the foam with polyethylene plastic and begin 'glass layup. Just keep applying fabric until the desired thickness of hull shell was achieved. Fair, paint and pop off the jig. The foam, plastic sheeting, molds and firing strip stringers wouldn't be part of the finished structure. You'd just have a solid skin 'glass hull shell, ready for reinforcement, stringers, bulkheads, etc.

    Another option is C-Flex planking.

    This is one of the advantages of using a real designer, instead of attempting to make these decisions yourself or inventing a new construction method. We're familiar with the majority of techniques, likely including ones you've never thought of.

    I can tell you, one thing designers don't like to do is "reconcile" some one else's work, especially if they aren't a trained designer. You must understand, from their point of view, every calculation and decision must be scrutinized. If these decisions have been made by an amateur, then all must be considered suspect and preformed over again to insure correctness. So, not only does it become a custom design, but one with considerable limitations and additional work, from the beginning.
     
  7. mitiempo
    Joined: Feb 2009
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    Location: Victoria B.C. Canada

    mitiempo Junior Member

    I would build this design in strip plank with diagonal veneer over - all encapsulated in epoxy. Lightweight glass cloth and epoxy coated for abrasion resistance. After the hull is finished you are left with a clean interior with just the main bulkheads and inner keelson showing. A few clear coats of epoxy inside leaves a good looking interior and this method is very durable, self insulating to a certain extent, and very light for its strength. Any attachments should be overdrilled and thickened epoxy filled before redrilling. Water ingress is an issue with any non metal structure and polyester absorbs more water over time than epoxy. Wood/epoxy is also pretty easy to work with in my opinion. I believe this method would also be the least expensive. Ultimately whatever the material durability is at least partially dependant on maintenance. This method should give you more durability than polyester in any of its methods and be as maintenance free as any other method if not more so. I suggest you see "Gougeon Brothers On Boat Construction". Good luck.
    Brian
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you'd read this thread from it's inception, you'd have noted that the original poster isn't interested in wood or wood cored construction, for understandable reasons.

    As much as I tout epoxy use, polyester hulls can be easily found 40 and 50 years old, still quite sound. I even know of a few 60 year old 'glass production boats, that have faired far better then their wooden or metal counterparts, given the same level of up keep negligence and neglect.
     
  9. apex1

    apex1 Guest

    Thats not the full story Paul! Look here:


    And I have seen boats of any kind and material one can think of, in pristine condition after half a century of daily use! Which is one of the secrets the boater is´nt told too often: the more it´s used the better it will stand the time.
     
  10. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Richard -

    Check out

    http://www.f-boat.com/pages/construction/index.html

    have a feeling this method would suit the your design.

    Basically, if you want curves - you must suffer. I choose to suffer only moderately around the bilges.

    People who recomend strip plank like to charge for their work - I wouldnt wish it on anyone who wasnt a masochist - especially cleaning out the female side of the hull. Plan on 10 hours per square metre.

    Otseg - I am very familiar with Kelsalls work thanks. Your illustration were very usefull to me.

    The main point - Flat panel on a smooth surface, whether one skin or two, does away with the most arduous part of boatbuilding - the exterior finish. Plywood is just as hard to finish as any other method, because you have to glass the outside - and thats where all the sanding, filling, more sanding goes on.

    Plywood will last a long time - IF mantained well. Maintaining a ply or wooden hull is tiresome - every ding, nick and bump has to be attended to quickly as moisture spreads through the wood, and is really hard to get rid of..

    Foam DOES NOT absorb water if you use the correct material.

    The other point is that fibreglass panels are not 'floppy and weak', unless you use very little material. Fibreglass strength for the equivalent weight in steel is over ten times. Fibreglass made to the same thickness as ply, will bend exactly like the ply. Its just physics. Sure it will be heavier - hence the use of a core to maximise stiffness. It will bend exactly like PLy, in two planes.

    Richard - , my feeling is like PAR said so well, CARE about weight - care a LOT about weight. Weight is $, and time and effort.

    PS - since you are a New Zealand type person, I found www.high-modulus.com to be good value for materials.
     

    Attached Files:

  11. apex1

    apex1 Guest

    Rwatson, the material in question is a prefabricated flat panel! That is commonly not the best quality of glass and resin. And has only disadvantages compared with a hand layup.

    A proper made strip plank vessel is less hassle than a glass layup and needs less maintenance than GRP. Thats not a guess, thats fact! And my products are proof of that every day.
    Please avoid discriminations like the one above! I cannot see how I would charge a Forum member! Strip planking is one of the best methods for amateur building, and one of the strongest too.

    Regards
    Richard
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Rwatson, fiberglass is without question pound for pound the weakest of the bunch, in regard to hull material choices. So much so that engineering tricks have to be employed to make it successfully compete with other materials (well okay, except ferro).

    Look, a single skin hull can work fine, eliminates the need for a core, potential core sheer or rot and multiple skin layups. C-Flex will require multiple face layups, but issues associated with cores don't exist.

    I don't see any reason why this poster should settle for anything less then what he wants, a boat that doesn't have a core (and it's associated potential issues), no wood to rot, an easy way to lay it up and minimize fairing.

    I disagree in that strip planking is less maintenance then a GRP layup. The facts do not bear this out. In fact, wood cores and wood construction of any type will require the most maintenance of all the other material choices. More importantly, wooden structures (any type) can tolerate the least amount of neglect before damage occurs. This is the primary flaw of wooden anything in the marine environment.

    On the other hand, I agree that for home built craft, strip planking has much to it's credit. It's fairly easy for the novice to work with and less then top shelf planking stock can be used. It does require a good bit of fairing and the planking process is quite tedious, so if paying for labor, not the best choice of methods (as has been pointed out).

    Some forms of strip planking, of which very few builders actually employ, can be the lightest of structures, only rivaled by high tech fabrics, foam cores and vacuum bagged hulls. I know of very few using these strip techniques, but it's possible.

    As a rule, strip planking in it usual form, is one of the heaviest forms of composite building, if the wood is a true core. It's about middle of the road (in terms of weight) if just a wooden structure with a light 'glass sheathing.

    I'm reasonably convinced the original poster has been persuaded from flat 'glass panel construction.
     
  13. apex1

    apex1 Guest

    Strip planked, cross veneered, glass sheathed Paul! Done with the accurateness (and time) of a ambitious homebuilder, to a well engineered design, and the comparison looks quite different.
     
  14. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I don't consider strip plank with additional diagonal veneers as a reasonable backyard alternative for a novice. The strip planking is easy enough, but fitting veneers can challenge the beginner, let alone getting good bonding contact between the two surfaces. Yes, this is a strong and durable construction method, but not well suited to amateur efforts, mostly because you have to be fairly precise about cutting and especially bonding the veneers.

    Now think about it Richard, remember the first time you applied veneers?
     

  15. rwatson
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    rwatson Senior Member

    No its not - I raised the question of principle of flat sheets in this discussion, and if you re-read, I planned to lay them up on a flat surface, and then hand layup the inside. I dont know where you got the idea that it was some kind of inferior product.

    Dont argue with me then- argue with the Product Spec sheets. This applies to marine quality foam, Epoxy and to a great extent to Vynelester.

    I have seen foam cored surfboards used day in, day out with big chunks missing, and no absorbtion. Try doing that with any kind of timber.

    And, if you get any damage to a wooden hull - what do you have to use to repair it ???? More wood ? Nooooooo - you use some kind of Epoxy and Cloth !! Yes - even you do !

    "best" in what way ?. Its hugely time intensive compared say to 'stitch and glue'. You need to have a carpentry savvy amateur - there is quite a degree of skill involved with it - and a *lot* of finishing work.

    I wasnt referring to you personally, but it sounds like I hit a nerve. I was talking about boat builders in general - there is a lot more money to be made in labour intensive hull construction.

    Aha - now we see where the strong opinions come from. So then Apex - why do more than 80% of all commercially built small boats get built in anything but timber. Its NOT because they are lower maintenance - and your biased view doesnt stand up to the real world practices. As Par says -

    Yes Par I DO agree that "wood cores and wood construction of any type will require the most maintenance ". I DO agree that GRP is "strip planking is more maintenance'. I DO agree that wood tolerates the " the least amount of neglect before damage occurs."

    I know - and mostly by some very erroneous statements, which I am attempting to rectify.

    Richard, I have been around and around this material business for the last two years. I even built several smaller craft before my big project, and have been using them on a day to day basis. I have owned steel, canvas and commercially built fibrglass larger boats.

    I love wood, I love welding and I hate building in Fibreglass. But - I am convinced that the 'flat table' FG technique yields a high quality, much much lower effort product quicker.
     
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