Why should I use Okoume vs Fir?

[jawilco]

I've read that fir is less prone to rot than Okoume.

It's less money that Okoume.

Fir sucks up more epoxy, adn that may be a good thing.

It's gonna be covered with glue and glass anyway.

My skill level is beginner level or thereabouts, so fir probably honors my time investment enough.

My budget is purse string.

I'm not looking for a bristol finish, altho I could get it with fir if I had the time and inclination.

I won't resale because I couldn't bear to part with it.

I don't really care if the boat lasts only twenty years VS fourty, cause it will probably outlive me in either case.

Fir might help me build a larger boat than Okoume would allow.

Fir is heavier, and will lower the center of gravity...well, maybe not.

If the boat is a half knot slower with fir, I don't think I care, cause I'm not in a rush if I'm sailing anyway.

So, really why shouldn't I just use fir and be done with it ?

[jawilco]

And I'd like to appologize in advance if this raises your blood pressure.

[Tom Lathrop]

No blood pressure problem at all.  Fir plywood is a perfectly good material to make boats with.  Your suspicions are correct and many boats have been built to a high level of finish with fir.  It is heavier, which is an issue with many small boats like racing boats and canoes or kayaks.  It is harder to get a fine finish on and, bright finished, it does not suit many people.  It is more rot resistant although not great either.  Unless it is sheathed in glass or another suitable material, it will develop checks in the face veneers forever. From the cost standpoint, laying on a sheath of epoxy and glass can equal or exceed the cost difference versus occoume and paint.  I would not personally consider using other than marine fir plywood.  Long ago, the quality of AB exterior fir ply was at least as good as today's marine but no longer. 

Most of us go with occume for its lighter weight. freedom from checking and easier path to a good finish.

[Charlie Jones]

What Tom said. Other than that I'd have to add- it's getting very hard to find decent fir plywood, even in so called "marine grades". The quality that was there even 15 years ago is just no longer there.

Just look it over very closely for internal voids or voids seen along the edges. You WILL NOT find those voids in Okume. So if the boat you are planning needs some stiff curves bent into it, you may get failure with the fir- it could crack at an internal void. If you see voids along the edges, just reject that sheet.

I built a 35 foot trimaran back in the 70s, early 80s using fir marine. I'd be hesitant to do so today on a boat of that nature. On a small boat, it should do fine, since you recognize the shortcomings of fir.

Also -  I priced the Princess 22 in both Fir marine and Okume. This was back in 2002 and the difference in cost, just for the plywood, was about 500 dollars for a 22 foot boat- . That's not a whole lot when you consider the time and expenses for the whole boat that will wind up costing around 15,000 all together.

[Hirilonde]

I agree with all of the above for starters.  Another reason why okoume plywood is more expensive is that all of it is imported.  For whatever reason, high quality plywood for marine use isn't built in the USA.  You can read into that what you will.  Okoume comes not only in metric thicknesses, 3mm, 4mm, 6mm, 9mm, 12mm etc., but most of it now comes in metric width and length.  The metric sheets are slightly larger in both directions than SAE sheets.  I just built new storage shelves at work for plywood and had to accommodate. 

[Greg Luckett]

And I'd like to appologize in advance if this raises your blood pressure.

I cannot imagine why this would occur.  When you get to know this crew of builders better you will see what I mean.

I don't like fir for 3 reasons, mostly: 1) heavy, 2) nearly impossible to find decent marine grade in 1/4 to 1/2 inch thicknesses (for some reason, 3/4 is common around here), and 3) it checks unless covered with fiberglass cloth.

[PAR]

I use fur in applications where there will be lots of fairing anyway, such as under sheathing, heavily curved panels, etc or it will not be seen much. The amount of fairing necessary for fur to look good under paint usually offsets any increase in costs for a better species panel, so it's a crap shoot. If you can fair quickly then fur is the choice. If you don't really care then fur is the ticket.

For a 25' lapstrake cruiser I finished up last year, I used fur below the LWL where fairing needs were minimal (bottom paint hides a lot of sins) and okoume above, because I didn't want to spend the rest of my life making this boat smooth. The first comment I got about this boat was on it's sea trials at Lake Dora, by a passing by Sea Ward sailor, who remarked my roll and tip job on the okoume looked like a 'glass boat. He didn't realize what she was until he crossed the fully varnished mahogany transom. That's when you know you made good material choices.

[Greg Luckett]

Par, what thicknesses of marine grade fir are you finding down your way?

Thanks

[Greg Luckett]

I was thinking that below the waterline would be made from Polar Bear fur, since their habitat is shrinking and getting warmer, they should be shedding.  Brave Eskimos (or drunk Canadians) could then collect the fur laying around on the tundra.  Polar Bears shed water very well.  I have heard their fur is actually tubular so it should suck up epoxy well. ;D

[Designer]

Joking aside, one of the points not brought up is the thickness of the ply to be used in the boat.

The thinnest fir ply is 1/4" which too heavy for small boats like kayaks and canoes. Also 1/4" fir ply has only three plies which when used with the sheet/grain fore and aft is nowhere as stiff as the lighter okume five ply and needs extra reinforcing.

My first experience with fir marine plywood was building Spindrift 10 hull # 1. As I folded the boat into shape, one of the boat shape repairs or footballs decided that it wanted to stay straight and peeled out leaving me an awkward repair in the bow. I also discovered that it did not matter how much epoxy and paint that I applied to the surface that it checked leaving zillions of hairline cracks following the grain line which is not only unsightly  but allows water to soak in to the ply. I could have sanded all of my paint off and glassed the outside of the boat but how do glass the inside of the boat with seats and hatches etc. because it checked as well.

I would have no problem using fir ply in the bottom of a Princess 26 or a larger boat because it would be glassed inside and out but I would probably opt for meranti which would be better.

[Terry Dunn]

I built my first boat (Spindrift 10) out of cheap fir plywood (not marine) and the cheapest epoxy I could find. I was going cheap since I did not want to spend a lot of money on my "practice" boat. I ended up encapsulating my s10 in fiberglass so it wouldn't check. What I learned was I could have built the boat in okume cheaper than what I spent on my fir boat with the extra fiberglass and epoxy and it would have been a lot lighter. And most important, it would be look better.

One of the panels broke when I folded my s10 into shape.

I did use 3/8" fir marine plywood for the 3/8" sheets on my CS 20. Okume for the rest. The okume is much easier to work with.

[fatehunter1972]

talking about fir.

My dad is building an airplane out of fir milled off his property.  It will be wood structured with plywood leading edges and modern fabric coating.

Now the plywood he is using!  3/32 inch thick and 5 plys!

http://www.aircraftspruce.com/catalog/wppages/finnishbirch.php

FINNISH BIRCH AIRCRAFT PLYWOOD (METRIC) from Aircraft Spruce

[Greg Luckett]

talking about fir.

My dad is building an airplane out of fir milled off his property.  It will be wood structured with plywood leading edges and modern fabric coating.

Now the plywood he is using!  3/32 inch thick and 5 plys!

http://www.aircraftspruce.com/catalog/wppages/finnishbirch.php

FINNISH BIRCH AIRCRAFT PLYWOOD (METRIC) from Aircraft Spruce

I like Fir lumber.  I use to use it for moldings and door frames, etc.  Darn near impossible to find around here anymore in the lumber yards.

What part of the world is your Dad building his plane in?

[Charlie Jones]

I use a lot of fir lumber also. I make stringers, keelsons, masts, booms, etc from it. Fortunately I have a yard about 50 miles away where I can go select the boards I want from his stack. He usually brings the whole stack out on a forklift, lowers it to where I can reach and then watches while I pick and choose

l generally find grain structure like this or better

And in fairly long lengths also

[PAR]

I can get fur in most common sizes, 1/4" on up. I don't use 1/4" very often, mostly 'cause I don't build boats that small. I can get a pretty nice quality of 1/2" (though it is 5 ply), but void free and limited surface defects. Yep, it checks at the mentioning of moisture content cycling, but if not tortured too badly and used out of sight or under a sheathing, quite acceptable.

I would never use fur as a brightly finished piece or as solid lumber, unless it was in the bilge or other wise out of sight. It just can't be reasonably finished and expected to stay that way. It's a fairly strong lumber, holds fasteners better then most softwoods, but turns into a washboard as soon as you try to smooth it.

I've been experimenting with Rhino Coat truck bed liner on wood. This seems to be the only product that will prevent the checks from printing though. Even a light sheathing will eventually allow the checks to work through.

[Frank Hagan]

I use a lot of fir lumber also. I make stringers, keelsons, masts, booms, etc from it. Fortunately I have a yard about 50 miles away where I can go select the boards I want from his stack. He usually brings the whole stack out on a forklift, lowers it to where I can reach and then watches while I pick and choose

l generally find grain structure like this or better

Man!  I haven't seen fir like that around here in a long, long time.

When I built my Weekender, I found some fir in my dad's "basement" that was used.  It was cheap back when he bought it in the 1970s, but it was the best looking stuff I ever saw.  Very straight grained, as good as any "vertical grained fir" you can buy today.  When I asked him about it, he said it was No. 2 common, rough, for patio covers and the like. 

I'll have to find a source here for fir lumber like that, Charlie.  Most of it I see has wide grain, symptomatic of fast growth in plantations, and not very good.  I love the look of grain like yours with just a coat of a varnish like Epiphanes ... it gives it a rich, warm glow.

[Charlie Jones]

lol- and I know where there is ONE board, 16 feet long and 6 inches wide, that has lain on the lumberyard shelf for over 26 years. That particular yard doesn't handle lumber anymore- they began doing other stuff, but the board is still there, when I get ready to go get it . You should see the grain on THAT. There were two, but I bought one of them to use building the tabernacles on the Princess 22

[Greg Luckett]

Charlie, your comments about that fir at the ex-yard reminded me of something.  A few years ago a buddy of mine gave me a board (fir) that was left over from doing a ceiling in a church sactuary.  It is a tongue and groove edging, but is about 14 to 16 ft long, 6 to 8 inches wide, and at least 3 inches thick.  It has been sitting in my shop loft tucked into the back.....I can still see it and almost reach it.  Man, this is like finding money in the pocket of an old coat in the closet.....hmmm, now there is an idea too with my memory being as it is... ;D

[olp4835]

This is the same questions that I am currently going through. I have built a few boats using the fir, had the checking issue, fixed it with glass.  The okoume, I have never used this before, I was shocked at the price. When I was going through the Aircraft Specilty + Spruce Co. catalog I thought I made a find at $19.30 per 4x8 sheet for quarter inch, 5 ply.  I called the Co. and ordered 14 sheets.  The sales people called and emailed me back several times. Each time they called back the news on the condition of the wood was going down hill.  I cancelled the order and apparently they are not eggar in refunding the money.  The catalog description is definatley not what they are selling.  The problem that I am finding with the Okoume ply is a reputable place to buy it.  There are no BS1088 Police, everyone that sells it say it is 1088, even Aircraft Spruce.  I'm leaning to the Fir because I am familiar with it. 

Where can I find the Merranti?   

Lowe's + Home Depot are now getting into the " water resistant luan game"

What is the weight difference in Fir vs Okoume vs Merranti  ????

Thanks, Otto :-\

[Greg Luckett]

Going by memory, 4x8 6mm Okume is 20 LBS, Merianti is 24 LBS.  I do not remember about fir plywood as I quit using it years ago for boat building.