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Plywood choices


lenm

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Gents,

 

I've been pondering lately re plywood in a cost / benefit sense.

I guess purchasing the best quality plywood is always a good rule to live by, however, it comes at a premium price, and perhaps overkill?

 

Is there any particular parts of the boat which you could consider utilising a lesser quality variant to keep a project more economical?

Bulkheads? Topsides?

 

Over her in Australia we have a few choices

- Red Meranti (certified BS standard)

- Gaboon (certified BS standard)

- Hoop pine which has a local industry standard exceeding the BS standard (both structural and quality).  Hoop pine has similar properties to Douglas Fir I believe.

 

The Red Meranti is half the price of the Hoop Pine!

with the Gaboon sitting somewhere in the middle.

 

Thanks

Len

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Meranti is just fine, so save the money and use it. It is about 20% heavier than Okoume (gaboon), but about the same as Douglas fir and hoop pine. If building a performance oriented craft, consider the Okoume, as saving weight is always good. This said, meranti and hoop pine are a little tougher and stiffer, so if building a cruiser, these would be the way to go.

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You mention cost is an issue. If it is a small boat it doesn't make that much difference in the long run. The biggest investment in building a boat is your time so you may as well go the good stuff. Like all things, if you skimp on cost you will regret it later.

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Len, I'm building the CS20#3 using Meranti. It is, as Par said, heavier but I have found it just as workable as the Okuome (Gaboon) and once it is resin coated and/or glassed I think there will be little difference in life-span. The difference will be a heavier boat, which I don't mind. As an aside, I found it difficult to get really good quality gaboon at a decent price.

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Many thanks for the comments so far.

Drew, your review of the meranti is promising

Alex, I fully agree what are saying re skimping on materials.

I guess i am more trying to establish if there is a point where throwing more dollars at something does not necessarily gain benefits. In my case, building the entire rig out of premium grade hoop pine ply.

Perhaps same could be said for sheathing.

I have a 30m roll of kevlar fabric leftover from another project, however, using it for the sheathing may be an expensive waste.

PAR, you make a good point re toughness and choosing/optimising timber species. i think i might try hoop pine on the bottom and top sides (for toughness), meranti stringers and bulkheads.

Okoume on the interior (e.g console, floor etc) to save weight.

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Again, it depends on what you're looking to get. If you want to toughen the hull a bit, use meranti on the bottom and okoume on everything else to save weight and money. Conversely, you might just consider okoume on everything, with a healthy sheathing on the exterior and additional layers on the chines. Given the choice between hoop pine and okoume, price and weight savings should force your hand, in the selection process.

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I used Meranti to build my Bay River Skiff.  I did it for the combination of economy and toughness.  Weight is not an issue for me.  The bonus for me is that the color of Meranti is a little richer (in my opinion) than Okoume, if you plan to varnish any of it.  Both are lovely, but Meranti's color is closer to Philippine Mahogany.  Both are wonderful to work with.

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There is a 3rd choice for BS 1088, but it is hard to find in many areas and certainly isn't a choice for saving money.  It is Sapele.  Which I think is the best looking of the 3 when varnished.  Doesn't help save money, but there might be a few who would buy a sheet or 2 for those places where varnish will be used.  This is what I used on the decks and transom of my Lapwing.

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What are you looking to build? It will help you decide on which plywood to use. If you are building something small go the good stuff, but if you are building a bigger boat then you have to think about the budget more. So what design do you have in mind?

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Hydrotek is a reputable brand.

 

What are you looking to build? It will help you decide on which plywood to use. If you are building something small go the good stuff, but if you are building a bigger boat then you have to think about the budget more. So what design do you have in mind?

 

I can't say I agree with this at all.  I'm a cheap skate, but would never compromise on the material, especially engineered material like plywood.  Your time and effort deserve the best regardless of the size and you deserve the best boat you can build.  When you add up all the money and time, the savings on cheap plywood will be long ago spent and you will still be regretting it.

 

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Hi Alex,

yep building a small boat (Ocracoke 20).

Everywhere I read on Australian sites recommends not to substitute AS2272 ply with BS1088 (see below example - last line).

But to pay over $260 for a piece of 12mm hoop pine vs $124 for a reputable Meranti is a huge difference, which leads me back to my original query being is the local product THAT much better, or just a case of our expensive local manufacturing costs..

 

Marine Plywood

Marine plywood manufactured to AS/NZS 2272 Plywood – Marine is a purpose built structural plywood, intended for use in hulls of boasts and other marine application and also in aircraft construction. It has a permanent Type A Phenolic bond and is manufactured from selected species based on density, bending strength, impact resistance and surface finishing characteristics.

None of the marine species are naturally durable and preservative treatment of marine plywood used in some marine environments.

Marine plywood to AS/NZS 2272 is made from selected species and therefore has known and consistent structural properties. The assigned stress grade of plywood manufactured to AS/NZS 2272 is F14.

Marine plywood to AS/NZS 2272 has two A grade faces and a Type A bond. In the Australian / New Zealand Standards grading system it therefore has a grading of AAA bond

Note that marine plywood manufactured to BS 1088, as imported into Australia, does not have predictable structural performance and must not be substituted for AS/NZS 2272 marine plywood. For assured performance marine plywood should be branded with the ‘EWPAA Tested’ marine plywood stamp. 

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There has been a bit of trouble over BS 1088 ply in the recent past.  Lloyds is no longer inspecting as I understand it.  This kind of makes the standard voluntary and only as good as the manufacturer's choice to continue to meet it.  I don't know how or if the Aus/NZ standards are enforced or monitored.  There are known manufacturers who keep up to the standard.  Joubert and Bruynzeel are well known and I found the Greek product Boulter Plywood carries to be excellent.

You guys also use Hoop Pine, probably because it works and is local.

 

I suggest learning a little more about your local standards and why they are recommended.  It very well could be just because they can assure the product, not that the standard is higher. But that is a good reason.  And how does Hoop Pine compare to Okoume as a product?

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Hydrotech and Aquatech are both quality sheets, built to the BS standard (1088 and 6566 respectively). No need for a boil test. The previously mentioned BS-1088 sheets that were questionable, haven't been on the market for a a few years, so it's doubtful there's any left. The price would be a good indication if it was some of this crappy stuff. In other words, if you find some BS-1088 at 1/2 the usual price, this should raise a big red flag. 

 

I'm not sure where that blurb of information came from, but suggesting that the known and reputable brands of BS-1088 marked sheets just isn't good enough or contain the necessary quality is just bull crap. I use both the BS-1088 and 6566 grades regularly and I've never seen a bad sheet of BS-1088 other than shipping damage. I have seen a few odd bad sheets of BS-6566, but this is also quite rare.

 

These are the same manufactures available to your market, so . . . These manufacturers need to comply to the BS standard or they'll lose market share, which isn't tolerable in such a narrow market.

 

Hoop pine is heavier than Okoume, but lighter than Meranti and Sapele. Hoop pine is rated as a nondurable species, but so is Okoume. Again, given the price of hoop pine, the Meranti or Okoume sheets are an obvious choice. Sapele is strong and stiff and the prettiest of the bunch, but at least for me is also the most costly, hardest to bend and typically is heavier than Meranti, in spite of the spec's posted above.

 

Lastly, Red Shorea (typical red Meranti) has a pretty wide range of physical properties across the various sub genius they sell as red Meranti. Commonly it's a little lighter than above, with ranges from the mid 30 lbs. per cubic ft., making Sapele a the heaviest choice, which on a small boat should be avoided.

 

 

Hoop Pine:

Weight (dry) 31 lbs. cu. ft.

Modulus of rupture 12,300 ft. lbs.

Modulus of elasticity 1,700,000

Crush strength 6,800 ft. lbs. cu. inch

 

Okoume:

Weight (dry) 27 lbs. cu. ft.

Modulus of rupture 10,900 ft. lbs.

Modulus of elasticity 1,230,000

Crush strength 5,300 ft. lbs. cu. inch

 

Meranti:

Weight (dry) 42 lbs. cu. ft.

Modulus of rupture 12,700 ft. lbs.

Modulus of elasticity 1,740,000

Crush strength 7,070 ft. lbs. cu. inch

 

Sapele:

Weight (dry) 42 lbs. cu. ft.

Modulus of rupture 15,900 ft. lbs.

Modulus of elasticity 1,750,000

Crush strength 8,800 ft. lbs. cu. inch

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Lenm,

 

I have used all of the plywood mentioned above. We use Hydrotek where we need strength and low cost and not worried about weight. It splinters more than the others and does have occasional voids. You will often see splits on the face veneer that they fill with a cheap filler.

 

I had no idea that hoop pine was that expensive over there. I was talking to John Welsford a while ago about hoop pine ply. He told me that he had been to the factory and was very impressed. He said that they sell seconds at a good price and they cannot find any fault with it.

 

When I designed the Ocracoke I intended her to built from Okume because performance is primarily power to weight. If I was building one over there I would probably use Hydrotek on the bottom for strength and okume for the rest. I do not think that delamination is an issue with the above mentioned plys as they all use the same glue and are reasonably void free. Hydrotek is probably the likely to rot as meranti is more durable than the rest. That said I would not touch any Chinese made ply.

 

Regardless of the ply used you still need to keep the water out of the wood and the only way to do that is with using good building practices and sealing every piece of wood with epoxy. When creating a vapor barrier thicker is always better and using glass with epoxy is the best way of creating a thick barrier. Where it is not practical to glass, use at least three coats of epoxy.

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Lenm:

 

I have been working on a Princess 26, and am using Hydrotek for the majority of the hull. I will be using Okume for the decks and some of the topsides to save weight up high.

 

Anyway, I addressed some of my findings with this plywood in the thread I started to document that build:

 

http://messing-about.com/forums/topic/8440-princess-26/page-5?hl=princess

 

Relevant parts start about post #95 and again around post #119.

 

To clarify, I see Hydrotek as more of a trade name for the BS 1088 standard using meranti. Different companies make it, so those would be their own brands. I have both Dragon and Fuji marked sheets. I understand both are made in China, so both were suspect. Neither of them are as good as the Joubert branded Okume, but having used both, I have found no major flaws in them and continue to use them. Both survived a hard boil test.

 

If I had to do it over again, I'd do the same, but would love to know what company brand of Hydrotek is trustworthy (comparable to Joubert or Brunzeel), find a source for that and stick with it.

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