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Marine Grade Plywood?

15K views 42 replies 7 participants last post by  Vastbinder 
#1 ·
So, if I''m building a plywood sailboat and sealing the whole thing with dynel and resin,...

What are the differences/advantages to marine grade plywood over normal plywood? Marine grade plywood pretty darn expensive stuff... is it really necessary?
 
#27 ·
dman, I beleive we shall have to agree to disagree.

A few note applicable to my particular case:
I don''t intend to design the boat from scratch, only to personalize an existing "tried and true" design;
My experience working with materials goes far beyond concrete... the lamination of plywood into specific curves and shaped happens to be one such area;
and
Costs are greatly different if one doesn''t buy all their materials as finished products from the boating store.

Good Sir, your''s is the voice of negativity which turns one away with "I can''t". Nothing ever came of such.

Thank you for your advice. I choose to disagree in many ways.

Happy Sailing to you!
 
#28 ·
I`m not looking to start an argument Vastbinder but take it from me I`ve been there.There is a great difference in negativity and reality.I will give you an example of one such project.I bought a hull and a bunch of gear for 75k,I had 300K worth the rceipts.I thought I was doing alright on that deal and then spent another 40k on this and that.The boat was no where near finnished when my finaces started to become taxed.I then sold the boat for approx. 60K to try and wash my hands from the whole mess.Being a journeyman machinist and owning a machineshop,as well as having a steel yacht,I will guarantee you that there is nothing I can`t build or weld out of metal.This is where the problems arise(ignorance to the lack of general knowledge of marine expenses) I know this project you are taking on is far less than this but the same rules apply.I never say "i can`t" do most things but I can`t afford to waste anymore more money messing with boats.We have come full circle on this thread where you are now going back to construction grade plywood,so what have you learned?Do you want to put a boat together with your name on it,and be poorly constructed?There is nothing worse no matter what it is having your name come up in a conversation saying what you have or had built is trash.For certain things it is better to not have tried,than to have tried and failed.I might have a reason for the negativity(thousands of dollars down the drain) and that money could of been much better spent on family.It is one thing to spend your time doing something you like but going broke doing it is quite another and then to have your creation considered worthless by the boat buying public should you choose to sell it.BTW look through ebay with reguards to homebuilt boats,it`s a firesale.It`s been a long time since my boating disaster and my figures are probably off somewhat on my boat`s prices however it`s close enough for someone to shake their head.
 
#29 ·
dman...

No argument and no hard feeling on my end. I really DO appreciate the advice you and others have given me.

Sorry to hear about the troubles you had with boat building.

I can''t begin to get into that kind of trouble as I don''t begin to have that kind of money. I will be left with buying the best grade of plywood I can find in my price range. Is it the best idea... likely not, but it''s what I can work with.

Regards the boat... it''ll be almost a replica of a time honored and extensively used design, so it''ll sail... maybe not the best, but it''ll sail. If it doesn''t last more than a season... it wouldn''t be that big an expense or bother for me to strip the entire hull off and put on a new one.

If all else fails, I''ll stick pontoons under it and float away just like that on the SS Junk-Heap! ;-) (and don''t think I wouldn''t do it either!)

I''m doing this for fun and hopefully to get to do some fairly minor sailing. So, for me, it doesn''t have to be perfect or last forever.

Once again, and I stress... I DO appreciate AND listen to the advice you guys give. I just don''t have the finances to apply all of it, so I plan to do the best I can with what''s available.

Good Luck! and really, no argument here... no hard feelings...

I''ll try to share pictures if it''s possible next year. This year there''s the "slap-together" dinghy currently in progress. (the dinghy is half for fun and half to test the materials and construction techniques)

Lastly... on an unrelated note: dman, isn''t mild steel just the most wonderful stuff (other than rusting)? I mean, with some judicious hammering, welding, and rivetting, you can get it to do just darn near anything you want! (I''ve been an armourer for about 20 years now)

Happy Days and Good Sailing!
 
#31 ·
windship/Dennis

No worries. I ask for advice in an effort to increase my understanding of best practices. If I had the money to carry through on all that has been offered, I would. Since I cannot though, I will use all the advice given to do the best I can with what I have available.

I have picked up many valuable tips from the advice given... and though I cannot apply it all due to circumstances, I will apply what I can.

Believe it or not, the few threads I have run have been very useful to me. I have refined the size and type of boat I will build. I have refined many of the basic structural specs. I have even had a chance to refine my initial desires on what I intend to do with the boat.

It''s all been VERY useful and I am not disregarding the advice I''ve been given at all. I''ve been compiling it and will apply as much as I am able (within my financial restrictions).

You guys have the practical knowledge that I lack. That is why I ask.

I am unable to apply all the advice given and must make certain compromises. That is why I appear to ignore (but I really AM listening)

I don''t know if I can post pictures here... I will if I can or will make them generally available if I can''t. The first pics will be of the dinghy though... and I fear it will frighten many of you! ;-)

Thanks again for the advice, and I really AM listening.
 
#32 ·
Hi Vastbinder,

I am not sure where you are finding a suitable grade of 1/4" exterior plywood for $10.00 per 4x8 sheet. Minimally you will need to look for a A-B grade Exterior grade plywood. A-B will contain some non-organic fillers and so will not seal as well as is desirable. I did a quick search around here and the cheapest 1/4" A-B exterior that I could find was over $30 per panel. The only 1/4" A-B ply that I could find under $30.00 per sheet was graded as exposure 1 plywood which is not the same as Exterior grade and which would be totally unsuitable. I could also find some one side sanded exterior grade A-C stuff down under $20 but AC will not stand up to the bending involved in planking a boat. Frankly, the glue line between the two courses of 1/4" plywood will cost way more than the difference in price between exterior and Marine grade ply. I would suggest that you use 1/2 marine grade below the waterline at least, and then do the topsides in 1/2 exterior. The savings in laminating the sheets of 1/4" plywood would pay the difference.

Jeff

BTW What do you wish to be called?
 
#33 ·
Thank you for asking... Scott is my first name.

I have several months to survey my local area to make sure I get suitable plywood. If I can find marine plywood in my price range, of course that''d by my first choice. It''s when I see the $200 a sheet stuff, that''s something too rich for my blood.

The reason for the 1/4 inch is that I''ve found that curving 1/2 inch ply is very stressful on the wood and it tries really hard to snap back to it''s original shape... which to me is a structural weakness. When one laminates 2 1/4 inch sheets, they bend easily to the desired shape and after the glue dries, they are permanently bonded into that shape... they will not attempt to spring back to flat. Yes, using the glue is a bit more expensive and work intensive, but the end result is better. (of course, in this case, one would make sure to use an entirely waterproof glue).

Loved the little 18'' boat by Antonio Dios? Nifty thing which I imagine would make a wonderful all-purpose lake boat for multiple persons (family boat)
 
#34 ·
Hi Scott,

Tony is an old friend of mine. We met probably 15 years ago at a small boat festival. He is really blessed with that rare combination of an artist''s eye and the ability to deal with the complex technology involved in designing and building boats. (Tony is that rare designer who has both designed and built boats with his own hands and so understands the impact of a design decision on the poor bloke that has to actually build what was drawn.)

Tony and I have enjoyed many a happy hour in lively discussion. Our ideas about yacht design come from very different directions. Sometimes our ideas are very close and at other times they represent the opposite ends of the spectrum. I was honored to be included in Tony''s book, ''Designer and Client'', as one of the clients. The chapter for better or worse reflects some of our differences in design philosophy. For many years Tony would send me his ''works in progress'' so that we could kick around ideas but we have not been doing that for some time now.

He has a number of stock plans that might suit your objects and certainly would be an excellent source to turn to for a quality design.

Regards,
Jeff
 
#35 ·
Jeff,

Actually, at this point, I''m considering going with some advice I was given awhile back and purchasing the plans for a small boat something like the 18 footer currently on Tony''s webpage.

Having the actual layout and dimensions would likely be so much easier for me than having to do some educated guessing. The results would likely be sooo much better.

Though, if I recall correctly, there are some free wooden boat plans out there... some of which I took the time to copy.

By spring, I should have things all prepared and worked out! Now I just need to track down a trailer to get my sailfish to water and I''m all set ;-)

Scott
 
#36 ·
Hi Scott,

Late lunch today......There are a variety of boat designs in the ''public domain''. Most of these are older designs from the 1940''s through 1960''s that were published in now defunct magazines. Some of these were reasonably good designs, but many were not very good designs even by the standard of their day and are very poor designs when viewed by today''s standards.

I think that you may be referring to Svensens free boat plans. http://www.svensons.com/boat/

I find most of the boats on that site not all that great a design. One design that does appeal to me is the 22 foot sharpie, ''Southwind'', although I suspect it would not be the most idiot proof boat to sail.

Here is another site with a bunch of older plans. I thought that ''Coot'' was a pretty neat little boat.
http://hometown.aol.com/polysail/HTML/oldboats.htm

In a similar veign, you might see if you can find a public domain set of drawings for Commodore Ralph Munroe''s ''Lifeboat Sharpie Egret''. This has always seemed to be a neat design. WoodenBoat magazine sells a nice set of proprietary drawinsg for the Egret.

In a more modern veign I thought that this was a very nice 26 footer for which very detailed free plans were available. http://www.boatdesign.net/nyd/K800/

BTW I happened onto the Boat Builder Central site: http://plywood.e-boat.net/categories.php

They have 1/4" marine grade Meranti for $27 per sheet. In other words that would add roughly $120 to the project over non-marine ext fir plywood. I really do not see how you can decide not to use marine ply when you consider the over cost and time involved in your project.

Regards,
Jeff
 
#37 ·
Jeff,

Thanks for the leads on boat designs. I shall have to look through them as time permits and when I select one, I''ll likely ask for opinions on it.

If the boat I choose is small enough and the marine ply available at a price I can manage, I certainly intend to have the good sense to use it! ;-)

Thanks greatly for the help... and I''ll let you know when a design is selected so I can get some feedback on my choice.

Scott
 
#39 ·
On the svensons page, would anyone care to express opinions on the Blue Moon, Gypsy, and Star-lite designs... with a thought to possibly using the Blue Moon as a starter boat since it''s smaller and I''m guessing easier to handle for a single person.

Scott
 
#40 ·
I would say that all three of these designs are very dated and would take a lot of effort to build only to produce very mediocre boats. Of the pocket cruisers on the Svensen site, the one that looks most like a decent boat that would be reasonably easy to build is the 22 foot sharpie called the Southwind (labled ''south'' in their link). This is a pretty traditional sharpie design.

Jeff
 
#42 ·
"Has sailing tech changed so much in the last 60 years or were these just crappy boats to begin with?"

At some level the answer is ''yes'' to both of these. Hull forms and rigs and evolved dramatically in ways that improve seaworthiness, ease of handling, motion comfort, and performance. BUT beyond that, these were really poor designs for their day.

The better D.I.Y. designs of that era came from magazines like ''Rudder'' and ''Field and Stream''. These magazines published designs ranging in quality from amazingly good to pretty bizarre. Many of the designs in these magazines came from the boards of designers of the caliber of Atkins, Crocker, John Hanna, Winslow Warner, Fredrick Geiger, Clinton Crane, Starling Burgess, and L.F.Herreshoff.

But most of the designs on the Svensen site are ''public domain'' designs that were prepared by unknown designers. The price of drawings are cheap compared to the hard costs of building a boat. It really makes sense to pick a good design even if you have to pay for it.

That said there are a bunch of good designs out there for free or nearly free it is just a matter of sorting them out.

Jeff
 
#43 ·
Well, for whatever it''s worth, I think I have selected a first design. The one I intend to build this summer is the "Breeze Baby" from the svenson''s site.

It''s likely a crappy little boat... in fact, it''s little more than a rowboat with a sail. However, it appears to be very simple, has more seating and offers a dryer ride than my sailfish and even if it doesn''t last 10 years, it might be a good way to "get my feet wet" so to speak... without it being a large project.

I figure that if I start out with a small, simple project like this one, then over the winter and next spring, perhaps I''ll have a better notion of what I''m looking at with a bigger project.
 
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