Boat Builder Central - Builder Forums

Ok, so Okume is the best plywood to use in the construction of my PK78! But I have found a close source for "marine plywood" / Fir. How does Fir compare to Okume? I am most interested in weight but want all the pros and cons. Thanks.

JLL,

The fir is substantially heavier, won't bend as well, won't look as good, and will suck up more epoxy. Use the okuome - I wish I had.

Ross

What we call okoume is technically BS 1088 or 6566 okoume marine ply. It's made to rigorous standards which are spelled out by the British government. None of this stuff is made in the US.
No American laws apply to the quality of plywood made here. The various plywood associations make it up as they go along. What you see is....etc.
BS 1088 is much lighter, (makes a BIG difference in a car topper) has more plys (1/4 in. and above),has literally no voids, bends beautifully, finishes beautifully, and will take a lot of the hassle out of the building process.
Charlie

1/4 inch sheet Okoume weighs in at 20 lbs while fir weighs in at 25 lbs - a good solid 25% more weight.

Fir is more rot resistant (irrelevent to us). It is also harder and harder to bend. The biggest difference aside from weight is that fir plywood can check (tiny fractures) so you need to put a thin layer of fiberglass cloth over it to prevent checking (like 4oz) so you have extra cost associated with the glass and the resin.

I personally use Okoume for everything. It is more expensive yes, but I like the weight advantage. I never have a problem saying I am going to use Okoume, sometimes Fir is too heavy so rather than have both around, I just use Okoume.

When I first read Charlie's post, I thought it a bit unclear so a brief clarification for my own benefit. BS1088/6566 is a standard to which there are several species of plywood constructed, Jacques sells Okoume (Gaboon) and Meranti. There are others but those 2 seem to be the most common these days. The 6566 has slightly thinner veneer skins than the 1088. I use the 6566 because I can't justify the extra cost for the 1088. 6566 is like B/B while 1088 is like A/B but compared to the stuff Americans call "A" it is more like 6566 is more like APA A/A as far as I can see.

If you can afford the difference in price for the plywood and shipping (since it sounds like the fir for you is local), get the okoume. I have never heard any one say "I wish I had not built this boat from Okoume". I have heard people say that about fir.

Like you I'm interested in the weight issue.
While I was perusing the various offerings at bateau.com I noticed in one study plan (R 13) a light weight version was possible if British Standard plywood was used.
The standard hull was 3/8 (12mm) frames and transom and 1/4 (6mm) hull planks with a design weight of 100 lbs. By reducing the hull planking to 4mm (at 12 lbs. a sheet it's 8 lbs. less than 6mm) you can reduce the total weight to about 65 lbs. And if the 12mm components are reduced to 6mm the weight will go even lower. The R 13 is strictly a row boat but at 13'5" x 52" it's not small. A rowboat that size that is in the 50-60 lb. range has got to be a breakthru'.
There has been an admission by he-who-is-not-to-be-named that the same treatment could be used on the other small rowing hulls.
Interested?
Charlie

Made a big mistake. 3/8in=9mm
It's hell to be an old guy brought up on the English system!
Apologies,
Charlie

Recommended reading - Ultralight Boatbuilding by Thomas Hill definately not stitch and glue.

British Standard has little to do with weight. There are heavy British Standard plywoods and light ones. So saying it can be built lighter with British Standard plys is a bit meaningless. Also, there are no "LAWS" governing plywood but the APA (American Plywood Association) puts out best practices and standards for US ply.

If you want to talk about alternative techniques to save weight, perhaps we should move this thread to amateurboatbuildng.com before we confuse people who are actually trying to follow the plans.... I would not go playing around with the scantlings unless I had the designer's approval or I was willing to accept the consequences.

LarryA,
What I stated can be easily verified if you have the time.
On the study plans for R13 (which you can go to with the click of a mouse) and on the actual plans which I purchased for $35 everything I stated about the lightweight versions is spelled out. I was not engaging in wishful thinking.
I also posted a query about using this technique on the other small hulls that was answered as I have stated by Mr. Mertens himself.
If your still unhappy, you'd better go to the web-master here and tell him to delete the items that I refered to. If I can download them so can anybody else. Maybe,even you.
And finally, I read Tom Hill's book on lapstrake construction numerous times and it doesn't bear on this discussion at all.
Keep your bow into the wind.
Charlie

This thread is about the PK78, not the R13 so the relevance is somewhat dubious. I was never unhappy, nor am I now. Nor did I state that any of the data you posted was erroneous (with the exception of the continued reference to British Standard as some sort of weight measure), inaccurate or in any way bogus. I am interested in discussing it but I have learned, from experience on the board (which I have been on for several years now), that it can confuse people whose primary interest is building their first boat and following the plans - all this fellow asked was for comparisons between fir and okoume - not what Jacques said could be done on the R13.

There is no question that Jacques and others (including myself) have discussed lighter laminate schedules. If you have read the book then you realize there are a lot of options for building a boat. You could use 4mm frames and glass them and could save a lot of weight while achieving the same strength. My point was not that it is not possible nor that it has not been discussed. My suggestion was simply to move the concept of scantling modification from the thread about Fir versus Okoume to a place where it would not potentially cause confusion.

Peace.

JLL said,"I am most interested in weight but want all the pros and cons".
I did my part.
Charlie

We started discussing Okume versus Fir then drifted to the R13 then argued about scantlings. . .

It is possible to build very light boats by using 4 mm aircraft plywood at $ 120.00 a sheet. Other weight gains can be made with framed light ply for the top seats and foam sandwich seats and frames. Lightenings holes should be cut wherever possible.
It is all very costly and labor intensive. Until now, many have asked the questions and sometimes argued about it but not many have tried.

If one has problems believing our weights, he can refer to Tom Hill's book. Tom H. uses the same scantlings: 4 or 6 mm Okume.
He rates his 15' 9" Whisp at 68 lbs against 65 for our Row 13 in light version. The Whisp is almost 3' longer and has fancy woodwork.
He has a wide canoe looking like our Scilly Gig, same overall length and beam and announces 49.5 lbs, ours is 80 to 100 lbs and I know one builder who made one hitting the scale at 65 lbs.
Our weights are reasonable. When we announce a light weight version, we expect the builder to pick the best materials, understand that he needs lightening holes and show good skills in his fiberglass work like 50% glass content.
If a 1st time builder uses cheap materials and does a sloppy fiberglass job, he should not complain about the extra weight.
If you are a 1st time builder and want a light boat, build an heavy one 1st.
I am not joking, it is not easy to make a light and strong hull, it takes some experience and more $.

Thank you for ALL your responses. Regardless of other disagreements, the answer to my question is clear. I will build the boat from Okume. Any savings from using another type of wood are dwarfed by my time and labor input. I believe in doing it right the first time. I will order the Okume Plywood.

I've already built that first boat. It was very heavy and I hope I learned my lessons.

Thank you again for all your help, and I'm sure I'll have more questions!

JLL

JLL wrote:Thank you for ALL your responses. Regardless of other disagreements, the answer to my question is clear. I will build the boat from Okume. Any savings from using another type of wood are dwarfed by my time and labor input. I believe in doing it right the first time. I will order the Okume Plywood.

I've already built that first boat. It was very heavy and I hope I learned my lessons.

Thank you again for all your help, and I'm sure I'll have more questions!

JLL

If you have already build a boat, there are good chances that you will keep the weight below 65 lbs. Keep in mind lightening holes in all frames.
One weight saving modification that would not be too difficult is foam sandwich frames and seat tops using using blue insulation foam.
I have to do some calcs and maybe test a panel or two, let's hope I find the time before you start.

I'm in the process of building the Row 13 and it's my first boat. It's taken me longer because I've made some mistakes that I had to fix. Some mistakes are not worth fixing.

I had the idea of making it a light version, but like Jacques said, it's a lot easier (and cheaper) to make a heavier boat first.

I'm glad a choose a simple boat to build as my first one. Although in hindsight, building something like the FL11 or 14 would have been easier and faster. But my 5 year old daughter liked the Row 13 because it's "prettier" and you can't argue with that logic!

If it's your first one, make a simple and heavier one. Or at least get the "practice epoxy kit" to get a feel for things. And read the epoxy book first!!!!!