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View Full Version : Meranti 6566 vs Doug fir marine grade



Ted Schmidt
01-22-2005, 08:35 AM
I am currently trying to decide which 3/4" marine grade plywood to use for the bottom of an Elver I am building. The two choices I can get locally are Meranti 6566 and marine grade fir. I will be glassing the bottom no matter which I use. Any comments on the two would be greatly appreciated
Thanks

Domesticated_Mr. Know It All
01-22-2005, 11:16 AM
Meranti is heavier than Douglass Fir and usually more expensive. Douglas Fir is more rot resistant. Meranti looks better finished proud but If you're gonna glass it, or paint it,Doug Fir would be my choice.

Bill Childs
01-22-2005, 11:59 AM
I like meranti much better than fir. It bends better, sands better, and the 6566 generally has higher quality of core plys. The quality of fir is getting so bad these days that I won't even consider it for hull material.

boatbuilder.org
01-22-2005, 12:10 PM
I would certainly use Meranti 6566 if the cost between the two were close and even if the cost was not camparable I would still lean toward the 6566. Generaly speaking, BS grade ply is just better than marine grade ply. Rot restistance is not an issue if you are using proper "WEST Style" construction.
---Joel---

JimD
01-22-2005, 01:00 PM
This is for Steve Redmond's Elver with the perfectly flat bottom panel and strip planked sides? You shouldn't have to worry about bending, sanding, or fairing. Looks like just a very straight forward piece of cut out plywood. Durability and strength seems to be the issues. I've used 3/4 inch df plywood and its easy to work with. I've used meranti as well but not in that thickness. Looks to me like a take your pick choice.

Venchka
01-22-2005, 01:05 PM
Based on a quick survey, 3/4" meranti and doug-fir are the same weight. BS 6566 is a whole notch or two below BS 1088 in terms of quality-assuming whoever made it paid attention to the wording of the specs. The big difference I see is in the face veneers, 1.0mm for BS 6566 & 1.5mm for BS 1088.

Ted, you haven't said how much 3/4" plywood or in what sizes. I assume 4'x8'. There are 5'x10' plywood panels available if that works better. It just doesn't seem like an Elver bottom could use enough plywood to justify less than the best available. It doesn't sound to me like BS 6566 meranti or doug-fir marine are the best available.

On the other hand, it's your boat. Good luck with whatever you do.

Wayne
In the Swamp. :D

JimD
01-22-2005, 02:15 PM
Hard to say if you're going to find anything better in any practical way. The 0.75 inch df I have has 7 layers, the inner 5 are the same thickness, the outer two are 2 mil (I just measured it). There are no voids, its waterproof glued, and the outside faces are finished as smooth as fir gets. Given that the application is for the bottom of a fg sheathed boat you may find plywood more expensive, but its difficult to see how its going to be 'better'.

Venchka
01-22-2005, 02:28 PM
If the doug-fir is that good and getting covered up, sounds decent.

Wayne
In the Swamp. :D

RodB
01-23-2005, 04:01 AM
I asked this same question when I was building my two layer hull...and went with Merranti on the exterior versus D Fir. From my research on this the Merranti is just manufacured to a higher standard and it is a bit heavier and stronger. I would think rot resistance would not be an issue if sheathed... If the D. Fir is less money, then go with Doug Fir.

RB

Venchka
01-23-2005, 11:02 AM
All else being equal, which seems to be the consensus, buy the doug-fir and keep your neighbors employed. We need North American plywood production.

Wayne
In the Swamp. :D

Quilbilly
01-23-2005, 12:31 PM
I'll just add this note of my experience with meranti. I used quite a bit on my boat and everthing is WEST system epoxy coated with a layer of 6OZ glass. One day during building the cockpit I noticed a little chipped void and started picking at it with my fingernail. pretty soon I was pulling 6" wide stips of cloth off with very little adhesion. I ultimately just stripped off one cockpit side completely and stopped trying, figuring I could redo all of it later just as easily if it failed as doing it preventively right then. I investigated other plywood in the boat, I had used fir and ocume and it seemed secure. In retrospect I believe the meranti was so dense that there was little epoxy saturation given the smooth surface of the factory sheets. So I really scuffed it up from then on to give it some tooth. The boat has been in the water without a cover in the rainy Northwest for two and a half years so far and the surface is perfect both on the part I redid and that I didn't. Go figure, but in summary, be sure to rough up the meranti before glassing and you will sleep better. Todd Miller

JimD
01-23-2005, 12:37 PM
Todd, that's an interesting experience you had with meranti. I have a utility skiff finished in bright meranti from the waterline up, so naturally I wanted as fine a finish to the plywood as possible and did not scuff it up to aid epoxy adhesion. I've had no trouble with it at all.

RodB
01-23-2005, 10:43 PM
I had an similar experience with Okoume ply where I spotted an area that was a bit light in color. I also have Merranti in my boat. Anyway, I also picked at light spot and began ripping off epoxied cloth...until it wouldn't rip off any more....ie., untill the wood fibers were ripping off.

I analyzed the situation and did a test (per my boat designer's recommendations) where I sanded an area fresh on this floor panel in question and attached a strip of glass to it, let it cure 24 hours. Then I ripped it off and the wood fibers were ripped out of it. Test OK... So the only conclusion was contamination... It seems that it is common for wood after manufacture to be contaminated and it was really the most likely explanation.

I am sure that the Merranti in my boat would not allow the cloth to be ripped off, it would have to be gound off. I think clean surfaces and well mixed epoxy and there are not problems with Merranti.

NEVER spray anything around your boat, or panels that will be going into the boat, that can cause loss of adhesion.

Like silicon, or lubricants, etc.... a possible explanation.

RB

[ 01-23-2005, 10:45 PM: Message edited by: RodB ]

imported_Dutch
01-23-2005, 11:17 PM
if its like most meranti that ive used the surface veneers are extremely thin probably 1/64 of an inch or so at best.the inner plys are fat one. whereas a normal 9 mm okume or sapele in 1088 might contain 5 plys all equally thick these things have uneven veneers. somehing just doesnt strike me as right about them. if it was on the bottom and going to be glassed anyway id go with the doug fir if it is a honest marine grade. ive got several sheets of that meranti out in my shop and im looking for someone to pawn them off onto

Ted Schmidt
01-24-2005, 08:02 AM
thanks for all your replys. I am surprised at the mixed opnions.
from previous posts I was thinking that the Meranti would be the better choice but Now I see that it is about a toss up. I have not seen the Meranti yet but have seen the Doug fir. the fir looks pretty good but does have a few edge splits less than an 1/8" which is allowed by the APA grading system. the panels are stamped with the APA seal so are real marine grade.
I do like the idea of using locally produced plywood for the boat as opposed to imported.

Bill Perkins
01-24-2005, 08:28 AM
Ted I ordered A-A marine fir ply from Harbor Sales that was very nice .I cut it up every which way and can report it had no voids . A friend of mine who bought his locally says mine is significantly nicer .When I next ordered he came in with me and bought from Harbor Sales as well .Check out their website if you're interested in price & freight ; or maybe check one of the West coast dealers that also specialize in marine ply . All fir Marine ply is not created equal .

[ 01-24-2005, 08:33 AM: Message edited by: Bill Perkins ]

Venchka
01-24-2005, 11:50 AM
Originally posted by Bill Perkins:
... or maybe check one of the West coast dealers that also specialize in marine ply . All fir Marine ply is not created equal .AMEN! Maybe even nip across the border and get some B.C. marine fir plywood.

All meranti plywood isn't created equal either. There are too many unkown mills making the stuff.

Wayne
In the Swamp. :D