Marine Grade Plywood Debate Thread...

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

Woodonglass...

I spoke to canadian ply.

http://www.canply.org/english/

Cadwelder..

Woodonglass posted the same thing just a few threads ago .

I was thinking of structural use of MG.. There are definately places on a boat that you could use basically any wood you want ( aside from osb and particle board lol ).

If I was to hang a 200 hp OB on my trans .. knowing there are no voids in the wood makes me feel more comfortable.

YD.

 

[Cadwelder]

Re: Marine Grade Plywood Debate Thread...

Woodonglass...

Cadwelder..

Woodonglass posted the same thing just a few threads ago .


YD.

Yep, thought I was following this one closer than that, got a few slipped in on me. My BAD. Iboaters disregard post #40 and refer back to post #31

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

(Quote) Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. (quote)

This part is a little suspect, in the USA this may be the case, but marine ply can be made of many different woods and the good stuff doesn't come from the USA. It also depends on what is meant by good stuff, Fir can be considered rot resistant when compared to some other types of MG ply, but for actual quality of the panel there are better products from other parts of the world.

 

[Woodonglass]

Re: Marine Grade Plywood Debate Thread...

I guess, I must be DENSE or something! MDO and HDO IS Manufactured AS MARINE GRADE "VOIDLESS" Plywood. It also states that it can be used for the construction of HULLS which I believe would be considered STRUCTURAL. READ what it says in RED. Using the MDO/HDO keeps you from having to soak the panel in resin, only the edges need resin. As long as you SCUFF the panel with 60 grit there is NO adhesion problems with Poly and especially NOT with epoxy. You will RIP the Wood laminations before the so called "Paper" outer lamination fails. This is NOT my opinion, This comes from EXPERIENCE!!!

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

(Quote) Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. (quote)

This part is a little suspect, in the USA this may be the case, but marine ply can be made of many different woods and the good stuff doesn't come from the USA. It also depends on what is meant by good stuff, Fir can be considered rot resistant when compared to some other types of MG ply, but for actual quality of the panel there are better products from other parts of the world.

I agree..I have used Mohogany MG ply ( but the stuff warped when cut ). Thats why I stick to Dfur.

I guess, I must be DENSE or something! MDO and HDO IS Manufactured AS MARINE GRADE "VOIDLESS" Plywood. It also states that it can be used for the construction of HULLS which I believe would be considered STRUCTURAL. READ what it says in RED. Using the MDO/HDO keeps you from having to soak the panel in resin, only the edges need resin. As long as you SCUFF the panel with 60 grit there is NO adhesion problems with Poly and especially NOT with epoxy. You will RIP the Wood laminations before the so called "Paper" outer lamination fails. This is NOT my opinion, This comes from EXPERIENCE!!!

Did you get my link I posted ? .. Call them up for yourselves. http://www.canply.org/english/

I was told that they do not recommend MDO/HDO for stringers and/or transoms because the core ply is C grade ( has voids ).

There sending me samples for personal testing .

YD.

 

[ezmobee]

Re: Marine Grade Plywood Debate Thread...

personal testing .

For iboats purposes, you are not allowed to do this testing at your shop. It must me done in your driveway under a blue tarp We have to keep conditions consistent.

 

[Woodonglass]

Re: Marine Grade Plywood Debate Thread...

It sounds like Maybe Canada does not manufacture Marine Grade MDO and HDO Plywood. The APA DOES manufacture Marine GRADE MDO and HDO and it they DO recommend it for Transoms, Hulls, and Structural purposes.

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

The problem with calling a certain company and asking about their plywood is that much of what constitutes the spec is voluntary. So there is no real spec for the product and if one company or organization says MDO or HDO is OK for Marine use, it doesn't mean all MDO or HDO will be recommended for that purpose by all suppliers. or that it meets the same spec as the product which was considered OK for marine use.

"Marine Grade" can mean almost anything, from slightly better than CDX, to a sheet that is a work of art.

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

For iboats purposes, you are not allowed to do this testing at your shop. It must me done in your driveway under a blue tarp We have to keep conditions consistent.

Can I use the woodshop ? .. Guys keep opening the door to cut wood for the docks.. leave me with 2" of snow and 3" of sawdust without cleaning it up when there done LOL.

It souunds like Maybe Canada does not have Marine Grade MDO and HDO Plywood

Yea..the thing was.. I could not find ONE manufacture of MDO/HDO in the US ( only suppliers where they told me to contact the mfg ). .. .. Got a link of someone in the US that makes MDO that I can call ?

I would even set up a 3 way call ( on my dime ) with them .

YD.

 

[Cadwelder]

Re: Marine Grade Plywood Debate Thread...

The problem with calling a certain company and asking about their plywood is that much of what constitutes the spec is voluntary. So there is no real spec for the product and if one company or organization says MDO or HDO is OK for Marine use, it doesn't mean all MDO or HDO will be recommended for that purpose by all suppliers. or that it meets the same spec as the product which was considered OK for marine use.

"Marine Grade" can mean almost anything, from slightly better than CDX, to a sheet that is a work of art.

So basically we've gotten no where....back to just use whatever you want to use.

Maybe we should make a rule that plywood questions are not allowed

 

[Woodonglass]

Re: Marine Grade Plywood Debate Thread...

The APA is NOT a company...
If a piece of Marine Grade Plywood in the USA has the APA Stamp of approval it has met their standards as far as plys, resins and testings. You can be assured of it's quality.

APA Puts the Engineered into Engineered Wood Products

For over seventy years, APA-The Engineered Wood Association has focused on helping the industry create structural wood products of exceptional strength, versatility and reliability. Combining the research efforts of scientists at APA?s 42,000 square-foot research center with the knowledge gained from decades of field work, and cooperation with our member manufacturers, APA promotes new solutions and improved processes that benefit the entire industry.
The Mark of Quality

Always insist on engineered wood products bearing the mark of quality ? the APA or APA EWS trademark. APA and APA EWS trademarks are the manufacturer?s assurance that the product conforms to manufacturing and product performance standards shown on the trademark. The mark appears only on products manufactured by APA members committed to APA's rigorous program of quality inspection and testing. Click here to read more about APA's quality service standards.
The Voice of an Industry

APA is a nonprofit trade association that has grown and evolved with the engineered wood industry. APA was founded in 1933 as the Douglas Fir Plywood Association, and was later recognized as the American Plywood Association. In 1994, APA changed its name to APA ? The Engineered Wood Association to better reflect the range of products manufactured by APA members and the international scope of the Association.
APA members are comprised of well-known industry leaders, whose mills produce the majority of the structural wood panel products manufactured in North America, plus a host of engineered wood products that include glued laminated timber (glulam), composite panels, wood I-joists, and structural composite lumber.
APA Vision and Mission

The APA Vision: To maintain our position as the leader in creating engineered wood product growth for North American member companies.
The APA Mission: To work in partnership with members to develop and maintain markets through excellence in:

• APA trademarked product promotion
• quality assurance
• technical and educational support

The Leading Resource for Information About Engineered Wood Products

With over 400 publications, extensive research and technical reports, comprehensive market studies and more, APA has the information you need about engineered wood products. APA field representatives in most major U.S. and Canadian cities, plus several European and Pacific Rim cities, are available to help answer questions involving APA and EWS trademarked products.

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

When large boats (yachts) are built from plywood, samples of the ply are sent to the company for approval and then it is inspected again when the ply is delivered because each batch of ply can be different even if its supposedly made to the same spec.

When the average Joe buys a sheet of MG he can be reasonably sure it will be a better grade of product than CDX, will the better qualities of the MG be of any value in how the product is used in the boat...maybe...maybe not.

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

Just got off the phone with the APA ..

Here is what the rep that I talked to said ( His name is Merrit Klien 253-620-7400 ).

There IS MG MDO/HDO ( marine grade with the clean/prime ready ply ). More expensive then regular DF MG ply.
There is also regular ply with MDO/HDO surfaces that are cored with voided cores.

APA ( as far as Merrit Klien ) suggest you completely Remove the outer paper face to raw wood before lams. He also said MGMDO is a Waste of money because your going to have to reprep the MDO surface to glass.

You should not lam directly on MDO/Hdo surface ( this is from APA..NOT ME ! ).

MDO/HDO ( from the APA ) is cost efficient for bulks that need direct painting surfaces..Not Structural because you would have to Remove the paper surfaces for laminations ...not just scuff with 60g .

This is not from experiance..but from APA .

So for trans and stringers I still hold firm on MG being the best product .. .


YD.

 

[jasoutside]

Re: Marine Grade Plywood Debate Thread...

There are some pretty seasoned vets posting up...

Here would be one rookie boat builders thoughts...

Quality, ranked highest to lowest...
1. MG Plywood
2. MDO/HDO
3. Arauco Plywood
4. Exterior Plywood

Price, ranked highest to lowest...
1. MG Plywood
2. MDO/HDO
3. Arauco Plywood
4. Exterior Plywood

Notice anything? Ya me too.

I really think that each have unique characteristics and therefore, appropriate and inappropriate uses for each.

Every boat builder also has a unique budget to work with, some have cash and others don't.

The trick? Making the two work together. Acquiring the correct materials and using correct construction methods for the selected project, all the while staying within the identified budget.

Just one non pro, very simplified opinion.

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

When large boats (yachts) are built from plywood, samples of the ply are sent to the company for approval and then it is inspected again when the ply is delivered because each batch of ply can be different even if its supposedly made to the same spec.

When the average Joe buys a sheet of MG he can be reasonably sure it will be a better grade of product than CDX, will the better qualities of the MG be of any value in how the product is used in the boat...maybe...maybe not.

I really dont know one US boat builder that uses anything less then MG in there "structural" builds ( unless its a composit stringer system ). But transoms ? .. I still dont know of a builder that used less then MG ( voidless ) wood.

Could you give us a link of boat builders that use anything other than MG or composits on the trans ?

I dont know were you can suggest/backup this statement ..

"When the average Joe buys a sheet of MG he can be reasonably sure it will be a better grade of product than CDX, will the better qualities of the MG be of any value in how the product is used in the boat...maybe...maybe not.[/QUOTE]
"

Its like saying .. erm.. dunno what your using ply for..but you can use x or y depending on application. True..but are you suggesting that CDX is for construction..or repairs ?

Need a breath...

YD.

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

Thats the funny thing...

Some here have the feeling they can save 60 bucks on MG..then go and spend hundreds on epoxy

For trans and stringers would you use osb ? .. CDX ..MDO ? ..

Thats what the pros and cons are for..

I still dont see many cons about MG other than its more expensive ( about 60-80 bucks more ) ..

Con the MG if you can for stringers/trans/decks/bulks. .

YD.

 

[fishrdan]

Re: Marine Grade Plywood Debate Thread...

I will say that more and more manufacturures use PT MG ply now.

By the way, I use PT MG ply.

Is that pressure treated MG ply (IE: doug fir, plys laid at 45* no internal voids, knots over X" boat patched),,, or just a CCA pressure treated plywood with voids and knots?

I agree with ondarvr that "maring grade" is kind of a loose term as there are many plywoods used for boats; different woods, different layups, different ply count/inch, treated, non-treated, etc. The APA has their MG spec, but this isn't nessasarily what boat manufacturers are using to construct boats. My aluminum Crestliner had knots all through out the plywood decks and transom, though it was CCA treated plywood.

 

[jasoutside]

Re: Marine Grade Plywood Debate Thread...

Some here have the feeling they can save 60 bucks on MG..then go and spend hundreds on epoxy

A con is a con and money is money my friend....

Build two transoms, I build mine with MG while you build yours with Ext Grade, both epoxied. We are both worm food before either of our transom projects rot out. You take the $120 (2 4x8 sheets @ $60 more) you saved on your project and buy everybody a steak dinner after your boat ride while I pull through Taco Bell. You win!

Course...

If I have the cash for MG AND the steak dinner it really becomes a moot point, eh!

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

(Quote)

Re: Marine Grade Plywood Debate Thread...
Originally Posted by ondarvr
When large boats (yachts) are built from plywood, samples of the ply are sent to the company for approval and then it is inspected again when the ply is delivered because each batch of ply can be different even if its supposedly made to the same spec.

When the average Joe buys a sheet of MG he can be reasonably sure it will be a better grade of product than CDX, will the better qualities of the MG be of any value in how the product is used in the boat...maybe...maybe not.
I really dont know one US boat builder that uses anything less then MG in there "structural" builds ( unless its a composit stringer system ). But transoms ? .. I still dont know of a builder that used less then MG ( voidless ) wood.

Could you give us a link of boat builders that use anything other than MG or composits on the trans ?

I dont know were you can suggest/backup this statement ..

"When the average Joe buys a sheet of MG he can be reasonably sure it will be a better grade of product than CDX, will the better qualities of the MG be of any value in how the product is used in the boat...maybe...maybe not.[/QUOTE]
"

Its like saying .. erm.. dunno what your using ply for..but you can use x or y depending on application. True..but are you suggesting that CDX is for construction..or repairs ?

Need a breath...

YD. (Quote)





I'm not sure what you're asking in the first part.

I've seen almost every type of wood used in putting boats together, MG, CDX, Pine 1Xs, 2x4s, stuff that looks like pallet boards, cardboard, etc, none of my current customers use anything but MG, most use PT MG.

What I'm saying in the second part is.

If someone is doing a cheap rebuild on a small boat that is going to be disposed of or sold in a couple of years its not going to make a real difference which wood is used. Even the lowest cost AX will provide enough strength and easily last long enough. Whatever amount you spend on it will never be recovered in the sale of it. Nor will it be in service long enough for any of the possible short comings of the cheap ply to come into play, if they ever do. You would never see one of these in your shop.

If someone is rebuilding or repairing a boat that is of more value, most likely larger, possibly higher performance, plus a desirable design and knows with the correct repairs or modifications the boat will be of even greater value, or will last many years into the future. Then by all means use the best products possible. This is the type of boat you will more likely see in your shop.

When a guy off the street orders a sheet of marine ply from the local lumber yard he is sort of stuck with whatever sheet arrives...good or bad, and for the most part he won't know the difference because he's not a plywood expert and has nothing to compare it with.

 

[Woodonglass]

Re: Marine Grade Plywood Debate Thread...

I guess a lot depends on the questions asked and how they are presented. I too, called the APA and requested specific details from the same source as YD. He did not speak to me but sent an email that is shown below. The APA does state in their written documentation that STRONG bonds CAN BE ACHEIVED with Light Sanding and the Use of PROPER Glude. The Gentleman gave me HIS personal experiences but as to the APA recommendations for lamination of MDO and HDO this is what was offered. Again, I will say in MY Experience with this product, Sanding with 60 GRIT and GLUING with epoxy yielded a bond that under HEAVY (OVER 2000 lbs of load) cause the wood laminations to fail before the Glued laminations failed. But.... that WAS just MY EXPERIENCE. As others have said before and will say again, Standard Marine Plywood IS the wood of choice for MOST boat builders and Professional Restoration shops. I am NOT one of those. I am just an OLD Contstruction guy that has played around with boats and construction material for over 4o years and am trying to apply lessons learned and pass some of them along. Take em and leave em as you will. I learn every day and hope to continue to do so. YD, Ondarvr, Jasooutside, Fishrdan, Ezmobee and countless others have "Learned" me a lot and I am sure they will continue to do so. I research the heck out of stuff, I make mistakes like everyone else but I like to think that experience counts for something and my experience with this particular product lends me to believe that it is a product worth using in the construction of some of these old boats we try so hard to put back together. But heck I'll be dead and gone before my boat rots away NO MATTER what wood I use. I guess that's it for me. I'm done with this one so take all of my BS for what it's worth and COlOR ME GONE!

We do not have additional information regarding face lamination of MDO or HDO with other materials.

The HDO/MDO product guide I sent to you states, ?HDO plywood develops strong joints if proper gluing techniques are used. The overlay surface should be roughened by light sanding and cleaned before glue is applied. A resorcinol or phenolic-type glue is recommended for exterior applications.? The HDO/MDO product guide makes no mention of bonding to MDO. I my personal experience when bonding MDO I have always removed the overlay at the point of bonding to expose bare wood so that I was assured of a wood to wood structural bond.

Regards,
Merritt Kline
Product Support Specialist
Wood Products Support Help Desk
APA
Southern Forest Products Association
253-620-7400 (phone)
253-565-7265 (fax)
merritt.kline@apawood.org
www.APAwood.org
www.SouthernPine.com

Disclaimer​

Neither, APA, the Southern Pine Council, nor their members make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this communication. Consult your local jurisdiction or design professional to assure compliance with code, construction, and performance requirements. Because APA, nor the Southern Pine Council have control over quality of workmanship or the conditions under which wood products are used, they cannot accept responsibility of product performance or designs as actually constructed.


From: Taylor, Mike [mailto:Mike.Taylor@Williams.com]
Sent: Tuesday, February 22, 2011 10:10 AM
To: Help
Subject: RE: Gluing MDO and HDO panels

Sorry, it does not. I have read ALL of the material on your website and could not find anything regarding my questions. That is why I called.

My questions are regarding the lamination of HDO and or MDO panels together face to face with the resin layers.
Will Polyester resin, polyurethane glue and or Epoxy glue adhere to this resin layer? Why and or why not and does the APA have any technical/testing data to backup these findings?

Mike Taylor