Buccaneer 24 Builders Forum

Discussion in 'Multihulls' started by oldsailor7, Jul 22, 2009.

  1. oldsailor7
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    oldsailor7 Senior Member

    Joe.
    I am curious. Why would you want to glass your boat INSIDE.? :confused:
     
  2. Joe Moore
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    Joe Moore Junior Member

    I know it seems a little counter-intuitive, as the nasty stuff is on the outside generally, but there is logic to it!

    Glass is very strong in tension (although not very stiff) so by putting it on the inside it will aid in protecting against pressure from waves and beaches pushing inwards against the hull. On the outside it would offer little to no strengthening benefit, just some abrasion resistance, most of which could be achieved with the correct paint.

    The second benefit is the added waterproofing provided by the glass/epoxy to protect against the small amount of standing water that could accumulate in the bilges - especially of the amas. It's this long term standing water which is more likely to cause problems on a boat which will spend long periods on a drying mooring.
     
  3. oldsailor7
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    oldsailor7 Senior Member

     
  4. Joe Moore
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    Joe Moore Junior Member

    I'm going to have to disagree. By my thinking and that of others with experience in the materials, If glass is required for strengthening it's much better off on the inside than the outside as it'll reach it's tensile strength more quickly on the outside of the impact radius. More importantly, glass in places like the amas where standing water could accumulate should aid waterproofing.

    It's important to note that I'm talking about a small amount of up to 200gsm weave in local areas, not some horrid heavy and weak chopped strand matt all over the hull.

    Still, there's a long way to go before any chance of laminating so once the hulls are built is the sensible time to make a final decision on whether reinforcements are necessary (purely given that the 3.6mm ply is about 25% undersized).
     
  5. sngatlanta
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    sngatlanta Junior Member

    I’ll back up what OS7 is saying for the Buc 24. Anything over the designed layup is moot. The weight to strength gain would be a bad trade. These boats have withstood the test of time built just as designed. Coat the inside as suggested.

    We just finished up an 18ft monohull that is glassed on both sides making the ply a core so to speak. This was done without the bulkheads or deck in place making it relatively easy. The bulkheads are set after the glass and taped in. This boat is designed to be done this way and the strength is required.
     
  6. Joe Moore
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    Joe Moore Junior Member

    I quite agree, the consideration here is being made purely because 3/16" (4.76mm) ply is not available at a feasible price in the UK. The nearest comparison is 3.6mm ply which is effectively 25% undersized - a significant percentage not to be ignored in structural terms.
     
  7. sngatlanta
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    sngatlanta Junior Member

    Are you using BS 1088 Okume Marine ply or the likes? The reason I ask is we have to import it to the US and I’m confidant you do to and am curious as to the different size. Our 4mm is 4mm so I see your dilemma. (note also our 3/16" is 4mm due to sanding or nominal vs. dimensional)
     
  8. Joe Moore
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    Joe Moore Junior Member

    Yep the BS1088 stuff over here is all sold in metric sizes, so the 4mm ply comes out at 3.6mm and is sold as such - I guess for the same reasons that your 3/16" also comes out undersized.

    I'm not sure where they import it from though there is usually a distinction between "far eastern", regular and lloyds approved grades - not that this guarantees it comes from any different sources I suppose.

    My local timber merchant do some good prices on all grades of plywood so when the time comes to place the order I'll go and see for myself what the quality difference is. After all, I've heard stories that all you're paying for in the bs1088 spec vs regular wbp ply is the inspection which can often be hopeless. There is also plenty of anecdotal evidence to suggest otherwise, but that debate has raged on through plenty of previous threads I'm sure!
     
  9. oldsailor7
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    oldsailor7 Senior Member

    Unless you are wanting an out and out racing boat, 1/4" 3 ply is fine.
    If you use Douglas Fir--(Oregon)--the boat will be a little heavier but still fine for a cruiser.
    In any case two coats of Epoxy inside, with three coats outside and in the bilge areas is the go.

    Epoxy is subject to deterioration by UV rays (sunlight), so all exterior surfaces must be painted with a good quality Polyurethane marine paint.

    No need at all for F/Glassing, except for 10oz glass tape on all chine seams and corners. :D
     
  10. bruceb
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    bruceb Senior Member

    coatings and ply

    Joe, the only places water has entered the 1/4 ply skin on my boat has been through fasteners and skin penetrations. Water has definitely gotten in the hulls, and still does, but the epoxy coatings put on 35 years ago still keep the ply dry. I would be more concerned of water getting in some places under the glass next to the frames, where I have had rot develop. On my amas, water had entered at the deck, tracked down the frames to the chine and had rotted it, but the coated ply skin was still ok. All my bulkheads have had some issues but only a couple have needed replacement. The water seems to have entered through the top edges of the bulkhead ply and around the limber holes- both areas that are hard to edge seal. I just "miked" my 4mm and 6mm "Hydrotek" brand ply- 4mm and 6mm exactly. I would trust it, it is quite strong, by the spec sheet and from experience on small power boats I have built. Bruce
     
  11. Joe Moore
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    Joe Moore Junior Member

    all good firsthand info guys, thanks!
     
  12. jmolan
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    jmolan Junior Member

  13. oldsailor7
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    oldsailor7 Senior Member

    I still have one set of Buccaneer 24 plans left if anyone is still interested. :D
     
  14. Samnz
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    Samnz Senior Member

    Capricorn is 4mm Gaboon ply everywhere except the main hull deck/cabin and cockpit which is 6mm. The whole boat is sheathed in a very light dynal cloth to protect the ply from moisture and sealed inside with epoxy. The panels flex a lot, but who cares, a wave will never break a small hull like these and if your worried about hitting a wharf, buy a powerboat!

    Any extra weight will really ruin the sailing ability of the boat.

    However, I am very scared of drying the boat out, only on a very calm day on very soft mud!
     

  15. catsketcher
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    catsketcher Senior Member

    Don't glass inside

    Gday Joe

    If you want to go the normal route you would glass the outside. Glass on the outside does a few jobs. It really does help with abrasion resistance and stops a thing called checking (splitting of the top veneer in sun) which may not be a problem in England. Also you can do a much much lighter glass job on the outside. You can get stuck into the glass with a squeegee and really rip the resin back out of it.

    As for tech stuff - the glass is going to have a really hard time of it going over the chine logs or you are going to use really small pieces of it. It will probably not lie straight so any extra tensile strength will be moot. You certainly won't be able to screed the glass as hard and the resin ratio will be much higher. Also the glass cloth is not really a good tension cloth. Being woven it will stretch a fair bit and then with half the fibres going the across any load condition it is only half good. You don't get stiffness glassing ply. In a foam boat you use stitched fabrics - don't try to use this idea with light woven cloth and ply. Paint is not good at abrasion resistance - a good poly is a great thing but it is a thin skin and easily breached. A beached boat will need an outside skin.

    cheers

    Phil
     
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