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Thread: Plywood Catamarans

  1. #1
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    Default Plywood Catamarans

    In general I find it quite amazing how many designers/designs one can find on the Internet. It looks like most designers now use quite advanced materials to achieve their goals.
    However, there are still a few designers out there using mainly plywood/epoxy like
    Bernd Kohler, Peter Snell, some of Mike Wallers or Angelo Lavarnos designs or Alain Berthet for which I have never seen references in a forum but I like the design despite the Web Page (http://www.abmarine.fr/cariboost1/crbst_0.html).
    All claim that plywood allows for strong, light and yet inexpensive designs. However, little can be found about customers experience with ply-catamarans.
    Do some forum members have first hand experience here?

    Thanks

  2. #2
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    Default Re: Plywood Catamarans

    Know a number of Easy (Peter Snell) owners and they seem all very happy. One of the nicest boats I have seen recently that is for sale is a ply boat.

    Shawn Arber Design - ply cat
    Andrew - MULTIHULL CENTRAL - Australian Distributors of Seawind & Outremer Catamarans and Corsair Trimarans (Queensland)

  3. #3
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    Default Re: Plywood Catamarans

    There are plenty of Wharrams built decades ago that are still sailing. You could add Dix and Simpson to your list.Not to mention the trimarans of Brown, Cross, Nicols, Horstmen etc. All materials have their plusses and minus's but I would not hesitate to build in ply.

    Mike

    http://www.dixdesign.com/43cat.htm
    http://www.boatcraft.com.au/simpson.html

  4. #4
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    Default Re: Plywood Catamarans

    I would add James woods to your list of good boats in ply.

    dont hear much about the experiences unless something goes wrong. seems most folks build and head out happy or we would hear the complaints.

    my only thing with ply is the cost these days. so i am looking at alternatives that will make it cheaper. the other is the Epoxy and its going to cost a bunch unless you get large quantities. its beginning to make sense to find several boat builders who need epoxy and just buy it by the drum. Same with cloth.

  5. #5

    Default Re: Plywood Catamarans

    If you're building a boat you'd be buying epoxy by the drum anyway. Ply boats will be glassed at least over all the external surfaces and well coated on internal ones, so 200 litres will dissappear pretty quick.

    The Shawn Arber boat Andrew refers to was built using the very best quality ply available. Doing this added little to the overall price in reality, but saved many hours in the building process because the ply didn't warp and go mouldy in storage, and could add years to the boats service life. The basic structure of your boat is not the place to be trying to save money.

  6. #6

    Default Re: Plywood Catamarans

    Quote Originally Posted by NW9955 View Post
    However, little can be found about customers experience with ply-catamarans.
    Do some forum members have first hand experience here?
    I have owned a 1991 Waarschip wood/epoxy catamaran for 3 years. I do not know what it weighs (tough to weigh a boat with a 26-ft beam), but I don't think it is particularly light. I do believe it is very strong.

    Rot is the nemesis of a plywood boat. Every fastener is a potential point of water incursion. Vigilance is required. Unfortunately, my boat was neglected under prior owners. The PO had to replace a section of the topsides and deck when water got in under the toerail. I found rot throughout the integral fresh water tanks. Not fun.

    Overall, I am ecstatic about the boat. The build quality is very high. The boat was clearly built by craftsmen, which I attribute to the material. The design is great and I don't feel there are any negatives due to any constraints imposed by the materials. Anyone should be careful about buying a used wood boat, but I would not hesitate to buy this one again.

    BTW, resale on a wood boat is not going to be pretty.

  7. #7
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    Default Re: Plywood Catamarans

    The Bobcat was an early british design made from ply. Some of these are still sailing after more than 30 years.

    From my experiences with a mirror dinghy, and discussions with other owners of old mirrors, the ply loses some of its flexibility, and instead of flexing to impacts, starts to break. Obviously this is a much thinner ply, but the impacts will also be heavier on a bigger boat.

    Of course, this may also be due to using a lower quality ply on some of the home built mirrors!
    Insanity is continuing to do the same thing and expecting different results

  8. #8
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    Default Re: Plywood Catamarans

    My 34' Searunner Trimaran was built of marine grade ply and aircraft grade spruce stringers with epoxy. That was 1979....so my little woodie is 30 years old. Many of the parts are as good as when it was new. the bilge below the floor boards is unpainted, and there is no discoloration anywhere. I have owned it 5 years now, and have had to make some repairs (some damage from an accident) It is not a big deal to repair a plywood fiberglass boat.
    I am very happy with the boat.If there was one thing I could change I would not have stringers. They make it harder to keep clean with the dirt catching and any water collecting along the stringers. but no big deal!
    I would build again, in fact I am considering building again. And Ply is high on my list of materials to use.
    Pics below on the links.

  9. #9
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    Default Re: Plywood Catamarans

    Freshwater ingress at fittings and hatches is one of the most frequent problems with ply construction, leading to replacement of large chunks of deck and if maintenance is neglected, deterioration of stringers, frames and bulkheads.

    One effective solution is to bore out all screw and bolt holes for the fittings to a larger size, fill with epoxy so that all ply edges in the holes are totally sealed and then bond the screws , machine screws, bolts and fittings to the deck with epoxy. This also gives better load transmission from fitting to deck. See 'The Gougeon Brothers On Boat Construction' book for details under 'Hardware Bonding'. They may also have a booklet on it, not sure.

    But basically, I think good quality ply is an excellent material and for the right design/ application is competitive with foam on tension, compression and shear strength, stiffness and cost. Where foam probably has the upper hand, IMO, is if you want to build with cross sectional curvature, either in the hull or superstructure. But , then, there's Constant Camber, Cylinder mould etc etc. And ply is much easier to repair and when moving or adding fittings. Then there's the issue of personal likes. I like wood. In it's engineering qualities and aesthetics.
    Last edited by langdon2; 15th January 2010 at 01:46 PM. Reason: Addition

  10. #10

    Default Re: Plywood Catamarans

    My bobcat is still going, 40 years old.

    It has had a lot of repairs due to lack of maintainance and poor Diy additions.

    eg Someone nailed the rubbing strip on with mild steel nails

  11. #11
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    Default Re: Plywood Catamarans

    Another thread just jogged the grey cells. here is a designer who very upbeat about plywood and has some very interesting boat to his name B. Kohler

    If you go to the home page there a lot of off topic stuff about WIG crafts

    the more I read the more I like the sound of epoxy covered ply.

    regards to all who do and who will in the future contribute to this great site

    thanks Paul

  12. #12
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    Default Re: Plywood Catamarans

    Although this is not a Multihull website. Russell Brown is the son of Trimaran Jim Brown, and has done plenty of multihull sailing. I wanted to add this site as it shows what is possible in Epoxy Ply construction. Light strong and beautiful.

    http://www.ptwatercraft.com/ptwatercraft/Welcome.html

    The joints are all jigsaw puzzle shapes, and the whole boat goes together with tabs like a kit. (it is a kit) look into the photo section. I have see the boat in person (and met Jim Brown) pretty cool stuff.
    Attached Images Attached Images

  13. #13
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    Default Re: Plywood Catamarans

    I design a range of plywood catamarans in all sizes. And I currently own three plywood multihulls and another one with ply decks (but with strip plank cedar hulls)

    Plywood boats cannot be left for years without maintenance, as grp boats can, but they do still offer the cheapest, lightest, quickest way of building a boat, especially in smaller sizes.

    Plywood is a familiar material for most people, familiarity which helps when building or modifying a boat.

    Richard Woods of Woods Designs

    www.sailingcatamarans.com

    currently cruising the Bahamas on his plywood/epoxy amateur built 34ft Romany catamaran

  14. #14

    Default Re: Plywood Catamarans

    My dreamed boat is the Reynolds 33 catamaran, but I'm not rich, I'm in Chile, far to USA and high freight cost, high import taxes, etc...
    In the other hand all my life I'm dreaming to build my own boat, I have some experience working with plywood, then I'm looking for a hard chine very fast 33' catamaran, as similar as possible to the Reynolds 33.

    żExist some design like this?

  15. #15

    Default Re: Plywood Catamarans

    Well. Experience. I am currently finishing a 39 foot plywood and epoxy/glass catamaran - hopefully ready to go in the water later this year. So far I have had to chop out and replace some small sections of the deck where water got in.
    My original plan a couple of years ago was to build a plywood and epoxy/glass cat - materials chosen mainly from an ease and cost point of view.
    However I ended up buying a plywood/epoxy/glass shell with 60% of the furniture done, which cost not much more than I estimated the materials would have cost for me to have built the boat to that stage. It saved me an awful lot of time and both I and the wife were happy about this.
    This is a point to think about. When you try to sell a plywood boat or even an incomplete plywood project you may be surprised at the low offers you get. Generally people with lots of money to spend will be looking at fibreglass production boats. So just to be aware.
    Make no mistake I am extremely pleased with the boat. However if I was going to build one knowing what I know 2 years later I think I might go for a ply bulkheads/wooden frame with a fibreglass skin (by molding fibreglass sheets on a flat surface).
    After you pay for the plywood and the glass and epoxy and do all the work and fairing and painting I truly think that a polyester resin/glass skin would not cost much more. And the pain of constantly worrying about water ingress would largely be absent. Especially on a reasonably large boat like this it is a genuine concern. Every fitting and screw has to be absolutely watertight - and watertight for the long term and under all sorts of stresses it will encounter.
    I have seen people suggesting you can simply epoxy paint wood to seal it. So far I have seen on this boat that wherever the glass cloth is missing pinholes and cracks form in the epoxy/paint surface and water will get in and cause problems.
    And as for just quickly chopping rotten spots out and replacing them with fresh plywood and glass/resin. My experience is this is no quick little job to get the new material to fit in with reasonable cosmetic properties. The ply has to be the same thickness and then you have to fair and fill it all in - and on the deck you also have to get the non-slip and paint to match reasonably. If the weather is ideal then you can do it quickly. Otherwise it can take days waiting for one process to set and then get to the next process etc.
    And as for it being light. Perhaps if you get extremely light plywoods you will achieve this.
    On the other hand if stressing about ply is going to stop you from getting going, then just go for it and follow your dreams. Most people who have ply boats that have been built well and taken care of are very happy with their boats.
    Anyhow. Cheers.

  16. #16

    Default Re: Plywood Catamarans

    Congrats on buying your hull, and good luck with it in the future!

    I'd suggest that every fitting should not just be sealed, but that the plywood core should be removed around it, and replaced with a solid epoxy filler. Best if you can do this from inside, leaving the outer glass skin intact, so you have a large overlap of glass over epoxy. That way even if water does get past your caulking compound, it still can't get to your core.

    This should be standard practice for any boat which isn't made of solid fibreglass. (Or metal)

    An excellent resource for plywood, and in fact any catamaran builder, can be found here: http://www.hostmybb.com/phpbb/index.php?mforum=easy

    Really helpful people, all boat builders like us, and not trying to sell anything.

    My own project is here: http://www.hostmybb.com/phpbb/viewto...54&mforum=easy

    re: It being possibly cheaper to use polyester/glass instead of ply/glass/eopxy - if you went with solid polyester/glass you'd end up with an extremely heavy boat. If you use any other core than ply, it will need glassing on both sides, and the cost will be greater.

    Also polyester suffers from osmosis.

    Again, best of luck. It's worth it in the end!

  17. #17

    Default Re: Plywood Catamarans

    Quote Originally Posted by DiasDePlaya View Post
    My dreamed boat is the Reynolds 33 catamaran, but I'm not rich, I'm in Chile, far to USA and high freight cost, high import taxes, etc...
    In the other hand all my life I'm dreaming to build my own boat, I have some experience working with plywood, then I'm looking for a hard chine very fast 33' catamaran, as similar as possible to the Reynolds 33.

    żExist some design like this?
    Don't know if this would suit? http://boboramdesign.wordpress.com/29-islander/

    Could be built from ply/epoxy insted of Duflex, would be quite a fast boat to build and sail.

  18. #18

    Default Re: Plywood Catamarans

    I dont think you understood the needs/whishes to own a Reynolds 33.
    A Reynolds 33 is far away from this design, you have posted.
    its a comparison between a motorhome and a F1-Car.

    regards

    JBU

  19. #19
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    Default Re: Plywood Catamarans

    Richard Woods has some designs that might suit you with a little modification:
    The 9m Javelin, with daggerboards, or even the 10.5m Romany, built in hard chine plywood and leave off the deck pod.

  20. #20
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    Default Re: Plywood Catamarans

    i've got a 10 yr old ply epoxy trimaran, well build, and will easily last another ten without any major hassle for sure.
    go and see some boats and you should be convinced.

    as said, you need to look after the two pack paint and fittings. not hard to do, you gota do something when not sailing ?

    i saw a 20 yr old epoxy ply cat in devon, perfect order, except for the bodges the owner had 'improved' the boat with, that's why i did not buy it

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