BS 6566?

BS 6566 (Shelman lists this as "BBX") Note: BS 6566 is no longer a current standard, but because the standard is understood by manufacturers, it is still referred to.

  • Face and back: 1mm
  • WBP glue
  • Patches acceptable on interior cores. Not as select veneers for the outer plies as BS 1088, but in one piece.
  • Does not have to be the same species, but Shelman's is.
  • The panel is completely balanced.

"There are no BS 1088 police." No one polices the standards. There have been cases of distributors re-marking BS 6566 panels as marine. Some of the cheaper panels that are marked BS 1088 do not meet the standards. It is best to get your plywood from a reputable manufacturer if you want BS 1088 that meets the standards and that has the manufacturer's name stamped on the plywood.

Woodenboat plans a series of articles on BS 1088. We look forward to having the differences in the standards clarified.

Follow up questions for Dick Garwood:

  1. BS 6566: Does not have to be the same species, but Shelman's is. Is this correct?
    ANS: Yes
  2. Are okoume marine and exterior plywoods below NOT Lloyd's registered? Or just rated differently?
    ANS: They meet the BS 1088 and BS 6566 standards, but are not Lloyds registered.
  3. Shelmarine: Glue is "melamine" reinforced. This is not the case with the other two grades?
    ANS: Correct
  4. Shelmarine "is approved for application on pleasure craft and small craft construction". So, what is "okoume marine" rated for, if not pleasure craft or small boat construction?
    ANS: They meet the BS 1088 standard, but are not Lloyds registered. BS 1088 is the British Standard for marine, but Lloyds does not necessarily certify it for that use.
The following will soon be on the Shelman web site.

OKOUME PLYWOODS

There are a number of okoume exterior plywoods on the market. It is important to understand the difference in these okoume plywoods so that you select the correct panel for its intended use. Shelman produces three okoume exterior plywoods, two for marine use and one for exterior use. The higher quality of the face, back and interior cores insure a longer life for the plywood.

LLOYDS REGISTERED
Shelmarine® okoume Plywood

Okoume as a species is rated as a non-durable wood. In order to obtain a rating by Lloyds as equivalent to a minimum of moderately durable, Shelman okoume plywood is treated with a preservative. Because of this treatment Lloyds Register gives us an approval for application of pleasure craft and small craft construction. No other okoume plywood has this rating or this marine application. Shelmarine® okoume meets or exceeds all BS 1089 and BS 6566 standards. The core has no voids, patches or gaps. The panel itself is all rotary cut okoume, balanced throughout. In addition, the front and back plies have a minimum thickness of 1.3mm. Glue is melamine reinforced. The surface of the panels is carefully selected to ensure the highest quality. The careful selection of all layers, thickness, face and back panels and special preservative insures you of a panel that is superior to any other okoume plywood on the market.

There are a number of Lloyds registered plywoods on the market. Being registered by Lloyds is a registration only. What is important to note on the registration is the "application" and "rating". This spells out where the plywood be used. Again, Shelmarine® okoume is the only Lloyds rated okoume plywood as "equivalent to a minimum of moderately durable". All other okoume plywood is rated as non-durable. For application, our plywood can be used for "marine, offshore, industrial use for construction of pleasure craft and small craft". No other okoume plywood is rated for pleasure craft and small craft.

Shelman also offers Shelmarine® Sapelli with the same high standards registered by Lloyds.

OKOUME MARINE PLYWOOD

This plywood meets or exceeds the BS 1088 and BS 6566 standard. The glue line is phenolic. Face and back are a minimum of 1.3mm with no voids or patches in the surface or core and is rotary okoume throughout. Panel is completely balanced.

OKOUME EXTERIOR PLYWOOD

This plywood is an all rotary cut veneer okoume plywood for exterior use according to BS 6566 standard. Face and back are one piece with a thickness of 1.0mm. Glue is phenolic. Interior core is joined pieces of veneer. Panel is completely balanced.

Shelman offers you a complete line of okoume plywood panels depending on use. Please contact Harbor Sales at (800) 345-1712 or other Shelmarine® distributors.

Notes (These come from a variety of sources.):

  • BS = British Standard. These people formulate standards for all sorts of things, not just plywood.
  • BS 1088 veneers may be rotary. The method of cutting is at the option of the manufacturer.
  • Although we have referred to BS 6566 because this is a used terminology, this standard is officially withdrawn and superseded by BS EN 315.
  • WBP glue: Weather & Boil Proof
  • All plywood is graded based on the quality of the veneers and the size and number of permissible voids and patches. Grades A-C are the most common. To be suitable for marine construction, panels must be made with waterproof glue and marked as exterior plywood (EXT) or marine plywood.
  • As a general rule for boatbuilding, use marine-grade plywood for planking because the wood used to make it is of higher quality with smaller voids and fewer patches. Inner veneers are also of higher quality, grade B or better. Marine plywood is therefore more stable, has less potential for checking, and the overall strength and stiffness are better than exterior plywood. Considering the overall cost of a project, the price for marine grade plywood is good insurance. For applications where the plywood is not bent (transom, stems, breasthook, knees, gussets, etc.), we would generally use ABX (X = exterior). If planking is applied in multiple cold-molded layers, ACX can also be used.
  • Domestic marine plywood is made to standards formulated and monitored by the American Plywood Association (APA). It is not a US government standard.
  • Domestic marine plywood: Species: Douglas-fir No 1 or western larch. Glue: waterproof. Face and back veneers A-A, A-B, B-B smooth cut and free of knots, pitch pockets and open splits and other open defects. Inner plies, B or better. Repairs: no more than 9 repairs allowed on A faces in a 4x8 sheet.
  • There are some plywoods available that are not called "marine plywood", but use marine in the description. These plywoods are made from wood that is other than those listed in the marine standard.
  • Pressure treated plywood: Pressure treated plywood is often heavily warped. This is primarily the result of the high temperature and rapid moisture take up during processing. Some plywood delaminates during the process. In addition, some pressure treating methods incorporate water repellent materials. These materials can easily jeopardize bonding so you won't be able to glue or paint the plywood successfully. See Preservative-Treated Plywood for Boat Manufacturing Applications - Best Practice Guide in the Wood & Plywood Information section of our web site for treatment techniques that are boatbuilding compatible.
  • BS 1088 (Marine Plywood) is currently undergoing a revision (the latest available version is 1966, updated in 1988) and may not be available for at least another four months. BS 6566 (Plywood) has been withdrawn from circulation for some time now and has been replaced by various European standards, including BS EN 636-1, BS EN 636-2, BS EN 636-3 and DD ENV 1099.
  • Bruynzeel used to "own" the US market, they are now out of business. There may be a company producing limited amounts of plywood under the Bruynzeel name, but it would be very limited.
  • It is important that any plywood you use for boat construction be "balanced". This means that there is a center ply with with an equal number of veneers on either side and the corresponding veneer the same thickness.
  • All plywood has exposed end-grain on the edges, which makes it susceptible to moisture migration and damage. Whether exterior or marine, any exposed edges need to be sealed.

Summary

BS 1088 uses more select material and is definitely a superior panel. Having said that, BS 6566, like Douglas-fir exterior, is suitable for some boatbuilding projects. In a perfect world, where we would only use the best, marine would be the only plywood used for plywood boatbuilding.

Personal opinion: On hulls that do not have to be the lightest weight, I would choose Douglas-fir over okoume. It is stronger and more rot resistant than okoume. Shelmarine® may be equal on the rot part... don't know for sure. Okoume is possibly more attractive than DF, but only just. For a natural appearance, I wouldn't choose either. Sepele is an African mahogany that has a more attractive veneer and is available in BS 1088 and may be a good option. The other would be to apply veneer over a plywood surface using epoxy resin. Some web sites that I have visited on my search have suggested that using interior plywood is acceptable for boatbuilding as long as it is encapsulated in epoxy. Not my boat. There is normally a lot of other stuff that goes into a boat, not the least of which is epoxy. If you drill a hole in the boat and do not properly seal it, your boat can turn to poop. If the glue bond fails, the plywood turns to rubber and there is not much you can do about it. In defense of those other guys, IF no water gets to the glue, it will probably be fine.

In a subsequent conversation with Dick Garwood, he gave his opinion on Douglas-fir. He conceded that it is stronger and more rot resistant than okoume, but that the patches in DF can be a problem. Because younger trees are now being used, there are more surface patches being allowed and that this could be a weak point that could allow moisture into the inner plies. He suggested sapele as an alternative.

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