What is the best marine plywood

Discussion in 'Materials' started by rugludallur, Jul 29, 2008.

  1. rugludallur
    Joined: Jan 2006
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    rugludallur Rugludallur

    I'm looking to source plywood to build bulkheads and interior for my 33ft steel cutter.

    Since I live in Iceland I will always have to custom order and shipping means that whatever I buy will be expensive when I get it so I figure buying the best ply available makes sense.

    From what I can tell (skulking about on the internet) the best all around is:
    BS 1088 Loyds certified Okoume(Gaboon)​

    And best manufacturers in order of quality being:
    Bruynzeel
    Shelman
    Joubert
    For the sole I'm thinking 1.2mm teak and holly face veneer
    For the bulkheads I'm considering bare okoume
    For cabinets and such I'm considering 0.8mm meranti face veneers mixed with the okoume.

    What is the best plywood available today in your opinion?

    Would you use different combinations for the face feneers?

    How would you treat the wood, what would you coat it with and how frequently ?

    Would you seal the cut edges with epoxy ?

    Regards.

    Jarl
    www.dallur.com
     
  2. Aethelwulffe
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    Aethelwulffe Junior Member

    I would go with the Okume, all the way, 1088 cert. Can't go wrong.

    Sealing the edges with epoxy is not necessary, and can actually promote degradation by creating anerobic conditions. Okume can usually survive even water that is trapped in by epoxy coatings!

    Teak and holly soles will disappoint you. The veneers are very thin unless you shell out the serious cash. The glues for those plywoods are NOT 1088 cert, and make boats 'round the world smell of mold. I would use a dimensional lumber for the soles, cut into parque over more okume ply. or longitudinally planked with lots drainage holes cut into the substrate, and some swelling room for the planking under the trim.
    For finishing the interior, I would use a soft finish, even for the sole. soft finishes are much easier to repair. This means oil based varnish. Inside you boat, they will last a lifetime. Countertops I recommend you cast in epoxy...looks great, very easy to learn to do and makes veneered countertop surfaces very durable. Any epoxy may be used to do this with, not just "tabletop" epoxy, but it takes a couple of practice runs to learn how much material to use.
    Topside, I would "treat" wood with paint, and lots of it. 2-part, with no non-epoxy fairing compounds or primers. Hydrophillic 1-part primers kill many paint jobs.
    If you want to go overboard a bit, you can use cupernol to treat interior hidden wood before painting. That is a biocide (cupric acetate). I have no recoating data for that treatment, but I often give new boats a bath in it before launching. It is not good to use on cosmeticly exposed wood.
     
  3. Ilan Voyager
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    Ilan Voyager Senior Member

    Okoume is not a durable wood

    The best known norm is the BS 1088 but a lot of good european national norms exist; as you're in Iceland I would look for the excellent swedish and finnish, or even russian boatbuilding plywoods. It's surely easier to find in Iceland than very exotic plywoods.

    There is no one best marine plywood; that depends on the application.

    If your's making a light racer okoume will work, if you're making a fishing boat a boatbuilding plywood from Finland (pine or birch, the stronger one) is the top. Even the best exterior grade construction will be good enough as the quality is superior to the APA marine plywoods from the USA.

    Some russian plywoods are excellent, and the finnish and russian boat building standarts are very high.

    Okoume is not a durable wood, and nor very stiff, so it's perfect for small boats like dinghies or catamarans. It's lone quality is lightness and easiness of bending or torturing.

    Sapelle plywood is bullet proof (and heavy) but prices are now scaring. It was the plywood used on the Muscadet and other plywood boats of the 1950s. A lot are always sailing.

    I've used all these plywoods (plus lauan, sapelli and some very exotics) but the finnish or russian gives the best job at best price for working boats. I've built 20 years ago in russian birch plywood and epoxy resin fast fishing boats (40 feet, 8 metric tons, 2*250HP diesel) and they have just needed paint jobs until now, fishing every day.

    ALWAYS SEAL THE EDGES. Plywood dies by delamination of the edges. Rot fungus needs wood, oxygen and water for living; a good sealing deprives the fungus of oxygen and water. Monoethylene glycol is the best desinfectant before use with epoxy resin.

    In classic construction, copper (naphtenate, or others) gives good protection but its stains in green) and is compatible with oil based paints like alkyd but not with epoxy resin.

    Teak finished plywood is for toys; the glue is not waterproof and the teak won't last (too thin). Teak laminating over plywood is better but time consuming, expensive and very, very heavy. On small boats is not worth, a good swedish pine will do a better job and is just as nice. A good paint with antiskid is the simpler, lighter, cheaper and best solution.
     
  4. Aethelwulffe
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    Aethelwulffe Junior Member

    Durability is a relative term

    Okoume IS a very stiff wood. That is why it is desirable for racers. Far stiffer than fir. I do agree with your usage assessment in that fir would be an excellent choice for your typical commercial fishing vessel.
    Balsa is not a "durable" wood. Nor is cedar, but both are quite enduring in specific applications where a high strength to weight (not as an amorphous/isotropic toughness which no wood has, but in a specific unimetric application) ratio. Balsa, despite being used extensively in the marine industry, certainly has no great weathering ability, if that is what you mean by "durable". Cedar and Okoume both however are pretty darn durable in this regaurd. I have never really seen a serious issue with failed okoume plywood that did not involve one easily identified factor: glue failure in a teak-faced interior plywood. I have (don't tell my customers) used okoume ply scraps that have been lying in the sand behind the shop for a variety of things. Usually a quick sanding brings them back to looking nice and bright. I have not noticed any degredation of the plywood boats I have launched suffering from any serious degredation when they come back for maintenance, and Lloyds likes this stuff just fine for offshore certification. In fact, I don't use epoxy in most of my small boats, so we are getting the behavior of the wood itself here. Sure, you can find stronger woods, but more often you need a high strength/stiffness/weight ratio, as well as superior weathering ability. That is where Okoume comes in.
    Main strengths of Okoume/Gaboon in relation to other marine building materials are:

    Plywood panel stiffness/weight ratio- Very unyielding when you test it relative to a panel of equal mass of other woods. The other woods will not be as thick of a panel of course, and others (some softwoods are lighter) have no where near the ultimate strength of Okoume, and lack weathering ability.

    Weathering ability- Okoume 1088 cert plywood has very little of the sapwood that you see sold as dimensional Okoume. Dimensional Okoume is no fun to work (soft and stringy) and isn't really great in any other way. For dimensional stuff, you are far better using real Mahogany or good oak. Plywood is an excellent way to use Okoume though, and thousands and thousands of boats attest to it's ability to absorb salt and stay nicely pickled below the waterline. It is not good as a bright finished wood in the sun. It likes to be painted.

    Adhesive compatability The radial, tangental, and volumetric shrinkage and expansion of Okoume after drying to under 12% moisture content is the lowest of all commercially available species. This property makes it undesirable for use as a planking lumber, but HIGHLY desirable for a plywood boat. Less expansion and shrinkage means fewer load cycles for your glue. This keeps the glued-on bits of your boats where they belong when they swell up. if for no other reason, this would make Okoume an excellent choice.

    If you want to bend a piece of 9mm Okoume ply and bend it around a tight dinghy bow, yeah, you may crack it if you flex it all at once and don't use doofers to spread the load on the wood. A piece of fir might just take that bend with less problem. The fir will mass about 30% more however, shrink and expand 430% more than the okoume, and not take glue (resins in the fir) anywhere near as well. You will also need to work your butt off to finish the fir ply and get rid of the face grain that stands up when you sand it, where the Okoume will be flat and pretty and just about ready for you to shoot primer after you fill screw holes. Yes, if a jet ski hits your boat at 10 kts in right on the beam, it might knock a clean hole in okoume that would have been a bad crack and busted frames in less stiff fir ply boat, but every wood species reacts to violence differently. I feel that does not qualify okoume as having a general evaluation as being "not durable".

    All that aside, I would not mind hearing about what the North European and russian favorites are for boat lumbers. Spruces and other species have got to have some excellent characteristics. As my grandpa said (he who's word is not challengable) "It isn't the kind of wood, it's the way it's used." He also said "If you do 'em right, it doesn't matter where you put your scarphs (on a spar). If you do 'em wrong, it also doesn't matter where you put 'em."
     
  5. Ilan Voyager
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    Ilan Voyager Senior Member

    Balsa is not durable but works encapsulated in resin as core.

    Okoume is good when protected under resin or good paints. In France okoume is used even n construction grade and it's known to be very sensitive to rotting.

    Well protected okoume is a good plywood. I agree that as timber is not worthy and nobody uses it.

    But for someone in Iceland, scandinavian boatbuilding plywoods are easier to find or import and surely cheaper. The best aviation plywoods are finnish, and you'll be surprised by the very high quality of the scandinavian and russian plywoods. Simply they are unknown of the USA because not exported there.
     
  6. Aethelwulffe
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    Aethelwulffe Junior Member

    I don't use epoxy with my Okoume. I also do not see it as being reported as having poor weathering characteristics in materials references. How can I correlate this statement?
     
  7. Ilan Voyager
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    Ilan Voyager Senior Member

    You'll have to read French...The french norm AFNOR and the CTB (Centre Technique du Bois) gives the norms for plywood in France.

    CTBX is the norm for exterior glued plywood.
    CTB Marine is the norm for marine plywood.

    The norm describes glues, process, quality of veneers and also specie of wood, classifying its durability and stability.

    The BS 1088 classifies only the gluing and veneers quality but not the wood used if I remember well.

    The CTB qualifies okoume as non durable wood, and the Khaya, Sappelle, Doucier woods get better ratings for durability, but they are far more expensive, and heavier.

    The french navy has his own ratings, and okoume was never used on a warship because concerns of durability. I've worked for them as naval engineer so I know well.

    Okoume plywood is well known in France as it was the cheap plywood (Gaboon was a french colony, and the french started the forest industry there) for more than 60 years, and used in costruction, shipping boxes etc...

    Sapelle plywood was preferred for boatbuilding before the arrival of epoxies which permitted to swicht to lighter and cheaper plywood. All the boats of the french golden era of plywod were made with hard mahoganny plywood.

    The multihulls made in epoxy-wood used okoume because of price and the epoxy encasulaption protected the plywood from rotting.

    Joubert and Toubois expanded their market making (good) okoume plywood with the well known in anglosaxon countries BS 1088. And surely the okoume is treated by them. you add the West System, and epoxies derivates in the 70's, a bit of marketing in the USA by the resellers which want good margins and its done.

    That doesn't mean the okoume plywood is bad, but it's inferior to a mahoganny plywood like red meranti, or khaya, or scandinavian plies in terms of durability. Don't speak to the traditionnal plywood boatbuilder like Mr Constantini in France of okoume ply in a boat! He prefers Khaya. He would say "it's for crate boxes" not for boats. And don't think about selling a boat made with okoume plywood to a french fisherman.

    Traditions last a long time...
     
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  8. xsboats
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    xsboats xsboats

    Okume has been the standard in my shop but I have used lots of aircraft grade Russian birch ply lately. 1/4" for a new foredeck on a 505, new doors and body panels on a `37 Ford Woody Stationwagon, etc... It takes epoxy well on the structural work and varnished nicely on the woody. 5 veneers in the 1/4", no dimples in pieces with 1 inch per foot camber, and less costly than the okume.I have bought up to 3/4" and highly reccomend it.
     
  9. minx163
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    minx163 New Member

    Here in the USA. Back in the day when boats were well "Wood" Before aluminum and fiberglass. They were made of marine grade mahogany ply wood. There are still allot of those boats still out there.generally speaking most boats die from fungus infection"DRY ROT" not water damage. with all of the deforestation in South America mahogany is readily available at a reasonable price.
     
  10. Ilan Voyager
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    Ilan Voyager Senior Member

    Dry Fungus is a misleading term; the fungus develops in a wood with a humidity above 20% and it's very contagious. Very hard to kill, but experience learnt me that borates and monoethylene glycol are very effective because being waterborne penetrate very well into the wood, and the salts migrate into the sick wood, and solvent based treatments do not penetrate intro "humid" wood.

    The USDA has very good publications about that.

    In conclusion I would say that we are all right: okoume is a good ply (even if french traditional naval carpenters think of it as just good for crates), russian birch plywood is excellent (and the finnish, who have also very good pine plywoods), the meranti ply is good also when made with good norms at least the BS 1066 for a job inside.

    Having a concern with deforestation, I'm not very fond of tropical mahogannies, I see here in the Quintana Roo State in Mexico how the forest has been destroyed for a few honduras mahogannies and tropical cedars...

    Just for our friend in Iceland I repeat that it's probable that scandinavian and russian plywoods are easier to find and cheaper for his purpose in his country. Besides these plies have a lighter color. Personal opinion but a lot of yachts are very dark inside because of the use of mahoganny and teak (following the english tradition).

    The teak striped plies may be very disappointing because of the glue used and don't last. Very decorative, very expensive, but often not durable as floors.

    In conclusion the BS 1088 is a good norm, but scandinavian and russian norms are just as good.
     
  11. xsboats
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    xsboats xsboats

    Those needing baltic birch can e-mail me at kswatts@msn.com for the contact info. Another excellent choice is called Powerply, sold by World Panel Products. It is treated veneers of gurjan. I have built two 8` by 10 pilothouses with epoxy and glass over the last three months with it. The tops took 1/2" per foot camber well. Very dense wood , takes epoxy , and despite the treament,finnishes brite.Check out it's properties on their website www.worldpanel.com
     
  12. bealsomonauk
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    bealsomonauk New Member

    Plywood issues

    I have done a lot of browsing on marine plywood. I am building a Hartley TS 18 sailboat. While I am just the initial framing stages, I am thinking about the plywood planking. Some observations:

    1. There seems to be an almost cult like devotion to Okume Plywood, which in most of the traditional boat building books condemn it for its lack of strength and to resistance.

    2. In the same breath, the Okume devotees condemn exterior grade fir for possible voids that could cause rot.

    3. I have a difficult time buying wood from area of deforestation such as South America, South east Asia or Africa. Hence, I am leaning towards fir or pine plywood.

    4. The only real difference between marine grade plywood and exterior grade appears to be the lack of voids, although I read accounts of people finding voids in marine grade plywood.

    5. Are voids really that big of deal if you use the WEST system? I do not think so as long as it remains sealed.

    6. Exterior Baltic Birch plywood at Menards looks like it as good at Marine grade for less money. Exterior grade, no voids. It cannot rot any faster than Gaboon (Okume).

    7. My plans call for 5/16's plywood. I am thinking about some good BC plywood I saw at Menards. I would use 1/4 inch and put the C side facing each other, after I filled it. This would give me a thicker hull to counter any voids. I plan on sealing it all with epoxy and using Dynel/epoxy on the outside. Any voids would be real small. Indeed, one can look at the whole stack of this plywood and see very few voids in the edge compared to CDX or anything else.

    8. Last, I do not see voids as an issue when bending the plywood with the grain.
     
  13. FAST FRED
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    FAST FRED Senior Member

    Teak and holly plywood are for Eye Candy , but not for a serious offshore boat.

    In the "old days" the Holly stood proud by 1/8 of an inch or so and became the no skid below decks. The teak was usually bare and helped no skid a bit .

    Ply cabin sole works OK in modest conditions if bowling alley, or Gym varnish is used.Both are partially skid resistant when wet.

    With a router we have cut 1/4 inch groves into the cabin sole and hammered , not glued teak strips that would stand proud.

    For refinishing the varnish strips could be pulled out .So the sole would be flat/fast to sand.

    FF
     
  14. Ilan Voyager
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    Ilan Voyager Senior Member

    The quality of fir plywood had dropped and its problems of sanding and checking are rather bothering. Fir is of not use on a good quality small sail boat.

    If the plans call for a 5/16 I would use as possible alternative a 1/4 birch plus some glass fiber each side like a 6 oz. That makes a matrix plywood fiberglass very effective while the thickness of the epoxy is controlled by the fiberglass, thus protecting the plywood.

    I would not use a 2 plies of 1/4 for the following reasons:
    - cost of plywood and resin. It will be expensive, far more than a good okoume or birch.
    - double job (cuts, scarfs etc)
    - gluing the 2 plies together won't be so easy if you're not using vacuum.
    - Weight A 1/2 hull with lots of resin in the glue joint is overkill for a small 18 feet sail boat.
    A big waste of materials and work.

    To give you an idea my 18 m2 catamarans (18 feet long, 10 feet wide, mast 30 feet, weight 190 pounds ready to sail) were made in 1/8 okoume for the hulls...The oldest has 23 years and is sailed every summer by its actual owner.

    Okoume is perfectly acceptable on a small sail boat, where weight is a big concern. It's a different matter on a cruise or work boat.
     

  15. bealsomonauk
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    bealsomonauk New Member

    Re-think

    I was beginning to re-think the double layer idea (particularly in regard to double the work).

    I have pretty much ruled out using tropical woods duw to deforestation. I want to use would from replenishable sources.

    The baltic birch looks as good as marine grade.

    My impression of American marine grade plywood is (due to its lower quality standard) that its market is primarily fiberglass boat manufactureres that use it for seats, floors and coore material, not as planking.
     
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