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Plywood quality


Aphers
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I probably know the answer to this already. The boat I want to build (S11N) needs four sheets of 5mm okume ply.

I have found a source for this but it is at the other end of the UK and the price is of course rather eyewatering, no surprise there.

 

I can pick up 'marine' plywood, BS1088, for a fraction of the price and much more easily at any local supplier. I am in absolutely no doubt that it would be poorer quality, more liable to check, with voids, and most likely just 3 ply rather than 5. But is there a chance that it would be good enough to last a few years? The boat will be a tender used daily, and does not have to look pretty. With the money saved on the plywood I could probably spend more on epoxy and glass and sheath it. It would work out cheaper but heavier.

 

I know the best thing to do is to buy the correct ply. But it would be interesting to hear from anybody who has tried using lower grade stuff, and how long it lasted. This will be my first attempt at boat building, and I am willing to treat it as something of a trial run, so long as it would last me at least a couple of years.

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Why are you sure the local suppliers have poorer quality?  If it really is BS 1088 there is no poor.

 

That being said, Lloyds of London no longer has any real control of the manufacturing or use of the standard BS 1088 and unless you know the origin of the material, you need to inspect it yourself at least. I bought my Lapwing material through a very reputable lumber yard, that was how I determined it would meet standard.  They have it manufactured in Greece for them and was wonderful material. I would go look at the local stuff and see if it has a stamp that identifies who made it.

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From what I've read, BS1088 means no voids and waterproof glue. But nothing about the actual species of timber used. Often it will be three ply, not five.

The BS1088 sheets cost less than a third of the cost of the recommended Okume/Gaboon plywood, which are also not available locally, adding further cost and hassle.

 

I was recently reading a magazine article about a clinker ply dinghy, where the builder had used cheaper 3-ply as he did not know any better at the time. The only apparent issue was that the scarf joints failed and had to be butt-strapped. That's something I could probably live with.

 

When I price up the materials that are going in to the project, it will cost about 40% less in total if I use the cheaper ply. So it's pretty tempting. But it would be a false economy if the whole thing falls apart after a few months use...

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What type of plywood to use for small boat construction is a source of never ending debate in internet discussions. Personally, I wouldn't build a boat with anything other than name brand marine plywood. Joubert and Brynzeel are 2 very good manufacturers. I know that some low quality far eastern manufacturers stamp their plywood with 1088 but it's really meaningless. The reputation of the manufacturer is the important thing.

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B&B used to buy BS1088 from one source until they started finding voids in it.  They switched suppliers.  My point is that all BS1088 isn’t necessarily high quality.   So, inspect your source’s wood, looking for voids along the edges.  
 

Not sure that three ply is a problem.  I built a dinghy with it, and the only problem I encountered was checking of the surface (fir).

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On balance it certainly sounds like the more expensive ply is the best option.

I was quietly hoping to hear from people who had thrown together a boat from any old ply and found it was still holding up ten years later. But that seems like wishful thinking, because so far the only reports I've had is from people who found the cheap ply to be very poor indeed.

Ah well, it's only money...  :D

 

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My first boat was built of “any old ply”.  It saw the water only occasionally, though.  But she is still sound after 30 years.  (She is currently in drydock, dying of “death by checking”.)The only problem was the checking of the fir, and that was nasty.  The photo was a refurb I did at age 20.  She checked badly the following year.
 

 The biggest risk in building with questionable exterior plywood is the chance of having an internal void.  But if you are only going to use this boat for a few years, I wouldn’t worry about it.  It can always be patched.  


Normally, I preach on using quality wood.  My justification is that we out so much time, effort, and our souls into these boats, that skimping on the wood is foolish.  But if this is a “temporary” boat, it might be justified.

A8C57F6C-BD0C-48F7-B83F-2326A0AD4A90.jpeg

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I might as well throw my 2 cents in.

I built a Princess 22 with marine fir plywood. It was stamped 1088.

12 years later and I am still sailing her in the Atlantic waters off the northern Massachusetts coast.

I didn't choose the marine fir, it chose me. I received it as payment for a garage clean out. Did not even know what I had at the time. 

As near as I can figure it was manufactured sometime in the early 1960's. I encountered no voids. I covered the whole outside with 10 ounce fiberglass.

If the plywood is made with waterproof adhesive and there are no voids, how long it lasts will depend on how well it is constructed and cared for.

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16 hours ago, Thrillsbe said:

 My point is that all BS1088 isn’t necessarily high quality.  

Yes, all BS 1088 is superb quality.  Not all wood stamped BS 1088 really is.  BS 1088 is a standard, either it is met, or it isn't.  Once Lloyds stopped the expensive process of certifying all manufacturers with constant inspection we no longer had assurance that what we bought was really up to spec. When in doubt, go with a known name brand, like Joubert or Brunzyle.  If you have reliable sources, you can get other manufacturers. it's a lot like finding the truth these days.  You have to become a skeptic and thorough investigator.

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