View Full Version : Okoume and Meranti Plywood vs Fir Plywood
08-24-2001, 03:27 PM
Does anyone have experience in working with the better quality plywoods such as Oloume and also with marine fir plywood.
I am pretty convinced that the quality of the Okoume and Meranti types is better than fir and that they don't have the checking problems that fir does.
However, are Okoume and Meranti stiffer than fir, in other words will it be more difficult to fit to the frames.
Thanks for any insight on this.
08-24-2001, 03:45 PM
Forgot to mention, that in my particular case, I will be using 3/8" (9mm) plywood)
All fir ply marine or otherwise has early and late growth rings (hard and soft); when the logs are rotary cut for plywood these form wild paterns on the face that sand very unequaly and telegraph brutally, especialy under gloss paint. Okume will finish baby bottom smooth cause the face is uniform.
08-24-2001, 10:05 PM
I have used BS1088 Okoume and BS1088 Sapele in 6mm. Both are high quality products. The sapele is harder, stiffer and heavier than the okoume. I also believe the sapele will take a tighter bend than the okoume. When the okoume starts to fail, the outer surface begins to splinter. The sapele fails all at once. When it breaks, it practically explodes. Both take a fine finish.
08-24-2001, 11:19 PM
Gert, I wish I had seen your post about two months ago. I just replaced my transom with 3 layers of 1/2" marine ply. It was handsome material, well made. I am now trying to finish the surface and have experienced the rippling of the surface due to difference in hardness.
I have had to go to the effort of long boarding because my orbital just makes matters worse. I am now in the process of laying on multiple coats of Smiths Hi-build epoxy in an effort to build up the low spots. If I had just used Okoume on the last layer, I would have saved myself hours of work and it would have cost less.
08-25-2001, 11:51 AM
There is no comparison between what they call "fir marine Plywood" these days and meranti or okoume marine. Like different products all together but fir does have its uses. Like Gert and Jim have said, rotary sliced fir will not give a good finish. Meranti and okoume will finish very smooth. Meranti and okoume are a bit more splinter prone than fir so a good quality plywood saw blade with a high angle ATB bevel is manditory to get a clean kerf. For bending situations okoume is much better than meranti. Okoume is also a bit lighter weight if that is important. Both come in 2 grades 6566 and 1088. 1088 is about 40% more expensive. I have used both and have found almost no difference in the 2 grades until you get above 9 mm.
As far as stength goes from strongest to weakest, the order is fir, meranti and okoume. Weight from heaviest to lightest is Meranti, fir okoume.
In my boat, I used fir marine for some interior structural bulkheads in the lazerette and engine room because it is a bit better at noise suppression, less expensive and don't show. Flat surfaces that are painted or veneered are meranti and all the deck skins and cabin trunk are okoume for the weight savings and bending quality.
08-31-2001, 08:09 AM
I've just wrestled with the same question building a 24' plywood runabout. Meranti will make my boat about 200# heavier, 30-40% stronger and $1000 cheaper than Okume. I believe Meranti weight and strength are comparable to fir but fir is miserable to finish.
Just got the Meranti ply from Noah's last week - beautiful stuff and less expensive than Fir.
A builder at the Wooden Boat Show last summer had this comment about using good wood which I thought was pretty insightful: "You are probably building the boat because you enjoy the building process, you will enjoy it a lot more if you use high quality materials."
[This message has been edited by DCWolfe (edited 08-31-2001).]
08-31-2001, 08:54 AM
As the old saying goes - "The bitterness of poor quality lingers long after the sweetness of low cost".
08-31-2001, 09:34 AM
Thanks for everyones input. I'll definitely go with Okoume or Meranti.
One last question, Between Okoume and Meranti, is one of them significantly easier to bend than the other?
08-31-2001, 11:12 PM
One other comparison you should consider before choosing is resistance to rot. Okoume is less resistant to rot than fir or meranti. Meranti is less resistant to rot than fir. Unless you are building an open boat or plan to keep it in your garage, boats built of fir or mearanti will last longer.
If you epoxy the boat all three woods will give long life, though it is hard to keep the checks sealed in the fir. As others have pointed out meranti and okoume don't check as much as fir.
Douglas fir is stiffer than meranti and meranti is stiffer than okoume. (modulus of elasticity: fir = 1,560,000 to 1,950,000, meranti = 1,500,000 to 1,630,000, okoume = 1,140,000)
My recolection is that meranti is more brittle than fir. When laminating, I remember meranti would snap without warning whereas fir would splinter on the outer fiber before the breaking point. I think fir is tougher.
09-01-2001, 09:31 AM
Something else you may want to consider is the difference between the two grades, BS 1088 and 6566, as far as number of layers (plies) go, which I found affects stiffness.
For example, in 1/4"/6mm, the fir will be three plies, and the imported stuff will be five ply. But when you go up one size to 3/8"/9mm, the fir will still be three plies, but the imported stuff will be five plies in 6566, and seven plies in 1088.
My plans called for two layers of 3/8" on the sides, and four layers of 1/4" on the bottom, all cold molded. The plans are older, and called for fir. I will no longer use marine fir for exterior stuff. I found the seven-ply Okoume 1088 was way stiffer than the fir, so I had to go to the five ply 6566 to get the bends I needed.
I think the five ply 1/4"(6mm)Okoume is stiffer than three ply fir, even tho the wood itself is probably more flexible, as BBI says.
I used the weight difference to my advantage as well. The plans call for approximately 750 pounds of inside ballast (it's a diesel sedan cruiser), so I used Meranti for the bottom, to put a bit extra weight down there, as well as have the more rot-resistant stuff below waterline; I used the Okoume for the sides and superstructure to keep topside weight lower. I believe the boat will come out close to the overall weight as if built of fir, but the weight will be more favorably distributed.
And finally, after using the imported stuff, I'll never go back. The crap they sell as Marine fir today is shameful. I've found voids, and had checking and even sleds (those oval repairs) pop thru cloth and epoxy on decks. You will find no repairs at all on the better grade imported stuff, it's truly wonderful clear faces.
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