Why not pressure treated plywood?

[jasoutside]

Re: Why not pressure treated plywood?

Well The Arauco may be void free - but MG is formed with water prooof adhesive - I needed 4 sheets for my Holiday - the difference is 80 bucks........

Well, strictly one man's opinion....

Nothing is water proof, only water resistant. Water will always win in the long run, always. So, how long of a run? Materials and build methods dictate that. Example, cardboard vs. Seacast (or whatever you like).

The numbers I was looking at was $80 for MG and $35 for Arauco. So in your example that would roughly make for a $140 savings. OK, not necessarily something to do cartwheels over but pinching pennies over the long haul of a total rebuild ($140 here, $140 there) this sort of methodology can make for thousands saved. Personally, I like that!

FOR SURE, if my wallet were fat, I'd be working MG allllll day long. Very nice stuff.

 

[Woodonglass]

Re: Why not pressure treated plywood?

"but MG is formed with fully waterproof structural adhesive made for wet conditions"




So does the MDO/HDO. Been used in the Road sign business and by Wood boat builders for decades. Since it is already resin coated on the final layer, the edges are all that require sealing prior to glassing. For Decks, IMHO, it can't be beat. Only issue is... Usually only quality Lumber dealers carry it, or it has to be ordered. Price is usually 30% less than MG. My wife drives 30 miles to save 5% on a pair of shoes!

 

[ondarvr]

Re: Why not pressure treated plywood?

Well The Arauco may be void free - but MG is formed with fully waterproof structural adhesive made for wet conditions - I needed 4 sheets for my Holiday - the difference is 80 bucks........and for all the $ I spent

What people need to remember is that what is called "marine plywood" is not just one product, it can vary greatly in quality and type of wood, each has it's own place in building boats (or maybe not if it's junk), so just because you buy "marine plywood" doesn't mean you got something better than what you can buy someplace else with a different label.

I use PT marine ply, as do most fiberglass boat builders these days.

 

[Cadwelder]

Re: Why not pressure treated plywood?

My wife drives 30 miles to save 5% on a pair of shoes!

LOL, Don't they all....

What people need to remember is that what is called "marine plywood" is not just one product, it can vary greatly in quality and type of wood, each has it's own place in building boats (or maybe not if it's junk), so just because you buy "marine plywood" doesn't mean you got something better than what you can buy someplace else with a different label.

So true and holds true with many other products as well.


Don't take this the wrong way guys, but I feel the original posters questions have been taken care of and we don't want this to turn into another heated plywood debate.

 

[starcrafter65]

Re: Why not pressure treated plywood?

Whelp - like my father in law says "It is a boat......"

And here is where my cost equalization occurs.....I did not coat my floor in glass - equalizing the cost between non MG and MG and making the whole install easier....in my judgement the conditions my boat sees (trailered, dry bilge - stored in garage) means that the flooring will not see even sustained humid conditions - let alone subject to water - and IMHO - I am not sure glassing is the be all end all - after all - it is poked full of fastener holes that water can get into....

SC didn't glass their floors - not even sure they do it now?

 

[jasoutside]

Re: Why not pressure treated plywood?

Don't take this the wrong way guys, but I feel the original posters questions have been taken care of and we don't want this to turn into another heated plywood debate.

True dat Cad!

Best of luck halfmoa and have fun

 

[halfmoa]

Re: Why not pressure treated plywood?

True dat Cad!

Best of luck halfmoa and have fun

Thanks man!

Still wondering what the manufacturers do/did though. Can anyone positively attest?

 

[jasoutside]

Re: Why not pressure treated plywood?

Thanks man!

Still wondering what the manufacturers do/did though. Can anyone positively attest?

I think I can say with reasonable certainty that my Starcrafts came with Duglas Fir MG plywood, unsealed (transom wood painted on one side). I reserve the right to be completely wrong on that though.

 

[jigngrub]

Re: Why not pressure treated plywood?

Thanks man!

Still wondering what the manufacturers do/did though. Can anyone positively attest?

My '97 Tracker came from the factory with the CCA pressure treated plywood, I bought it new so I know it wasn't changed over by a PO.

 

[halfmoa]

Re: Why not pressure treated plywood?

Once again, thanks to everyone for responding! This is a completely new subject to me and the learning curve is steep on a few things...like deck replacement for instance. It's obvious that non pressure treated woods sealed with epoxy is the way to go and we've substantiated those claims with not only scientific data but manufacturers reccomendations and real world experience. I never imagined this thread would turn into such a wealth of knowledge but I'm glad it did! Thank you all!!!

halfmoa

 

[Yacht Dr.]

Re: Why not pressure treated plywood?

It's obvious that non pressure treated woods sealed with epoxy is the way to go and we've substantiated those claims with not only scientific data but manufacturers reccomendations and real world experience.

Actually ... its not obvious at all .. I see nothing that substantiated anything concretely. Well .. other then that Star had it right about MG ply for boats .. and EZ's Arauco Ply ( good stuff btw for an alt to MG ) .. or Ondarvr's multiple grades/makes/models of MG .. or Woodies MDO .. or CW's post #35 .. or Jasoutside's "Well, strictly one man's opinion...." .. .. .. need I say more.

What Im trying to get at ( and its been said already ) is that everyone/anyone has a plethora of materials and tools to choose from when restoring or repairing a Boat.

There is NO ONE BEST tool or material for every "category" of job. And thats what all the hubbub is about. A floor is a floor.. a stringer is a stringer.. a glass job is a glass job .. " just tell me the best way to do it ".

It just does not work that way .. its a boat to boat .. application to application .. material to material.. etc. ( Dont skimp on your protection gear Ever ! ).

There are No-No's .. but you Can get around them if you are talented and familiar enough with that specific application ( however there are some No no's that will get you in the dog house if attempted ) .

Iboats ( IMO ) is one of the best sources of information because of the member base. .. We have Experts/Pros to Novice members. Some of the threads/questions brings out the light of not only the "experts" but the "newbs" experience as well. Im sure all of us learn from each other regardless of there Member Stature ..and grow as a vast support to anyone that wants to venture into DIY.

Sure.. things can get a little heated..and posts modded or deleted ( cough oh no not me ) .. but the bottom line is you WILL find your question answered here. And your answers could come from a 5 post count new member..or a Mod or Rear Admiral ( cough I should be upgraded to Admiral ) .

YD.

 

[Mojo^]

Re: Why not pressure treated plywood?

Thanks man!

Still wondering what the manufacturers do/did though. Can anyone positively attest?

In 1988 the fine folks at Grumman used uncoated PT for the core of the transom on my 1542 Scrambler. Years later the transom skin (inner and outer) looked as if it had been shot a few times with a 12 gauge. Really, really nasty galvanic corrosion and it required a lot of work to replace it. I had no idea just how bad it was until I disassembled the transom and was able to get inside. I thought I'd be able to get away with cleaning/killing the corrosion and then patch it but the more I tried to clean it, the bigger the holes got. The area around the 3/16th aluminum fastener holes going through the transom quickly grew into thumb-sized holes as the aluminum just flaked away and turned to dust.

 

[ezmobee]

Re: Why not pressure treated plywood?

In 1988 the fine folks at Grumman used uncoated PT for the core of the transom on my 1542 Scrambler. Years later the transom skin (inner and outer) looked as if it had been shot a few times with a 12 gauge. Really, really nasty galvanic corrosion and it required a lot of work to replace it. I had no idea just how bad it was until I disassembled the transom and was able to get inside. I thought I'd be able to get away with cleaning/killing the corrosion and then patch it but the more I tried to clean it, the bigger the holes got. The area around the 3/16th aluminum fastener holes going through the transom quickly grew into thumb-sized holes as the aluminum just flaked away and turned to dust.

Grumman's choice of treated plywood in 1988 would have been the old arsenic kind so that didn't cause the corrosion. Damp wood trapping water (even better if salt) against the aluminum did it. Sounds like you need to get yourself a nice street sign

 

[Mojo^]

Re: Why not pressure treated plywood?

Grumman's choice of treated plywood in 1988 would have been the old arsenic kind so that didn't cause the corrosion. Damp wood trapping water (even better if salt) against the aluminum did it. Sounds like you need to get yourself a nice street sign

Thanks to sound advice received on this forum I bought an 4'x8' sheet of .062 5052 and did the right thing by replacing all of the corroded skin having it MIG welded. I replaced the core with two sheets of exterior ply laid-up at 45 degree angles bonded with PL and sealed with epoxy. Seams and fasteners were sealed with Gluvit on the interior and Steelflex on the exterior. It was a major PITA but it is solid as a rock now and will most likely out live me.

 

[oops!]

Re: Why not pressure treated plywood?

What people need to remember is that what is called "marine plywood" is not just one product, it can vary greatly in quality and type of wood, each has it's own place in building boats (or maybe not if it's junk), so just because you buy "marine plywood" doesn't mean you got something better than what you can buy someplace else with a different label.

I use PT marine ply, as do most fiberglass boat builders these days.

Thanks man!

Still wondering what the manufacturers do/did though. Can anyone positively attest?

ondarvr can attest. he (according to cad's dictionary terminology) is a true expert in the field of fibreglass and gellcoat)
as far as the rest of boat building......he visits the production floors of most boat manufacturers all the time.....so he is "up" on what they are using. he can also tell you what kind of resin/ fibreglass, wood. vynal and foam they are using in the 2012 models..something we have to wait till the spring boat show for.

guys like yd, bwt and me, ect, (sorry if i missed any) can attest to what we know works.....as we do this every day all day long. so we know what not to use, and what to use that gives the best results for the cost.
so when we see a question like using pt on an aluminum frame with out any interface between the different products.....we will advise against it.

to use the "proper materials" is an open question. there are many books that say you can use "this" material. however in all practical purposes...it is the wrong stuff to use.
take automotive bondo for example. it IS the correct product for filling and fairing.......but, in a boat, we know that it absorbs water. so it it the "proper" material?. no

on the other hand.....look at PL......is it made for this purpose?, no, is it proper?, no. but does it work properly?....yes. (in most circumstances).

what is "proper" about marine plywood is what EZ said.... it has waterproof glue....more layers of laminates, and less/no voids. the difference between that and ext ply is minimal....so, in that case....we can get away with it.

dont forget that if we used the "proper" materials to build our $2000 boats....they would be worth 30k by the time we were done. they would also last forever......do we need them to do that?.....no.....so we make trade offs to bring down the cost.

 

[Yacht Dr.]

Re: Why not pressure treated plywood?

to use the "proper materials" is an open question. there are many books that say you can use "this" material. however in all practical purposes...it is the wrong stuff to use.

. but does it work properly?....yes. (in most circumstances).

what is "proper" about marine plywood is what EZ said.... it has waterproof glue....more layers of laminates, and less/no voids. the difference between that and ext ply is minimal....so, in that case....we can get away with it.

dont forget that if we used the "proper" materials to build our $2000 boats....they would be worth 30k by the time we were done. they would also last forever......do we need them to do that?.....no.....so we make trade offs to bring down the cost. .. Edited by YD..

Iboats is not about 2k boats .. and/or that restoration exclusively.

I seriously doubt that a small resto will be worth 30k .. or 20k .. or even the cost of the el' cheapo way of 10k.

Saving a few hundred on Basic cost of wood and resin ( glass is glass and can be bought at cost for many members here ) Might be a good thing. .. but it might be a bad thing. That is the Thrust of buying Quality on the Main Rebuild Materials.

So you want to skimp out on a 4x4 sheet of MG ( doug fir MG ) and replace that with some ABX .. or CDX .. for a cost saving of 40 bucks..

Then you want to skimp out on the resin ( or some suggest buy the other stuff and epoxy coat ) from HD.

Look .. the way to repair or rebuild a boat is in the same context as that of a good chef. Sure you can get by with the Kmart knives to cut your stuff.. but a Chef pays more for his tools .. and has less problems in the Process of slicing.

Sure you can make a cheap steak Look/feel/taste like a Filet .. but its not a filet and has to go through more processes to Emulate that same Cut that a Chef will have in 5 min.

Tools and materials .. it boils down to this. You spend more .. or less .. its up to you. But the outcome Might be the same thing if you fail prepping some material that your not use to.

I have In My experience decided to go with the Best of the Best. Not because Im a pro . .. because its more cost efficient in the long run.

You can cut corners here and there .. but some corners should NOT be cut. Not worth the time or agro or $. The end result is the same .. but the path you take is completely different.

YD.

 

[halfmoa]

Re: Why not pressure treated plywood?

You can cut corners here and there .. but some corners should NOT be cut. Not worth the time or agro or $. The end result is the same .. but the path you take is completely different.

YD.

Well stated YD!

What I was looking for in this thread was an answer besides "because". "Because" doesn't cut it unless you're the boss and I'm the worker. "Because" with elaboration, which I've received, is what I was after. There's a whole lot of "because" out there...

So....1/2 inch Douglas Fir plywood coated with resin. Is that the resounding answer? Anyone care to provide a link to iBoats page of a product they've used with great results?

Thanks again everyone!
halfmoa

 

[bbodin]

Re: Why not pressure treated plywood?

Yacht dr, Oops said worth 30k no 30k worth of materials. Even a 35k bass boat bought new has not got 35k worth of materials. Worth is about supply, demand and what someone will pay for it. If I had a original wood canoe owned by Abraham Lincoln, it would be worth several undred thousand but only a few dollars in materials. So Oops is correct. Worth is in the eye of the beholder.

 

[oops!]

Re: Why not pressure treated plywood?

yd im not sure of some of your points. some seemed to hang in the air.

but lol......i could easilly run up a tab of 40k parts only doing a restoration......easy......new motor, new transom assembly, new drive.....there is 15k right there. if we go BB double that.
aircraft core deck and transom.....epoxy that all together, then lets do a full 4 color gell to the hull....and after that we can put new glass in the windsheild. may as well buy a proper new frame with it.

as you know they do it every day in super mod go fasts.

the key word is "proper" this is a subjective word. most of our boats are made from poly, so poly is the proper material to use. so why go epoxy?
you see?....proper is subjective.

but as i mentioned.......if we see something that will not work, we will advise against it

 

[oops!]

Re: Why not pressure treated plywood?

by the way dave......

not to hijack. (since we are going down the materials road).... i know you have to use what materials the owner of the shop gives you to use...(its what they buy, sometimes you might get a different product if a new salesman gives a good deal to head office).

i am referring specifically in this case to 3m polishing compounds. as you know, i use farecla. however, i have heard of a product called "the stick". out side of this laymans name, i dont know anything about it. other than great reviews.
have you heard of it or used it?

thanks
ward