MDO plywood for transom

[83vert]

Re: MDO plywood for transom

MDO (medium density overlay) is exterior plywood and should not be confused with MDF (medium density fiberboard) or OSB (oriented strand board). MDF and OSB are fine for certain applications in home building, but I would not use either of them on a boat.

I think there is some confusion about the two. "Mdo Plywood is made with waterproof glue and is designed for use in exterior signs, has few or no voids and has a smooth surface of phenolic resin paper that accepts epoxy and paint or other glues without any surface preparation." That is a direct quote from the book Maintain and Improve your Powerboat by Paul Esterle.

 

[andgott]

Re: MDO plywood for transom

It might be "Arauco" which is what I currently use for boat work.

I give Arauco a big thumbs up too- It is widely used by amateur boatbuilders... For some reason it got a bad name along the line, something about it not being rot resistant, but that applies to ANY wood that gets wet. Once it's sealed up, that is not going to matter... I've built small boats from it, and am using it in my restoration work now, too... Lowes has it, and the price is right. I can't get marine ply anywhere near me anyway.

 

[Robert4Winns]

Re: MDO plywood for transom

I think there is some confusion about the two. "Mdo Plywood is made with waterproof glue and is designed for use in exterior signs, has few or no voids and has a smooth surface of phenolic resin paper that accepts epoxy and paint or other glues without any surface preparation." That is a direct quote from the book Maintain and Improve your Powerboat by Paul Esterle.

This is true. MDO is not the same as MDF or OSB.

 

[flyer4ever]

Re: MDO plywood for transom

AC ply is 10 times better than what was origionally used in the boat. This stuff will outlast your desire to keep the boat, and if it doesn't then replace it again in 25 years. It will sure save you a lot of money. Just my 2 cents worth. Ernie

 

[robthompson66]

Re: MDO plywood for transom

Arauco is great. I used it for my 16 footer for the transom and flooring and I think for the stringers too. I believe that it was ABX grade too. Worked real nice. They do have ACX as well that is a bit cheaper because of the C grade on one side. Either way the ABX and ACX Arauco is cheaper than marine grade

 

[flyer4ever]

Re: MDO plywood for transom

The plywood available today is much better than it was 25 years ago. To me I would only use marine grade ply if I was building a wood boat from scratch.

 

[83vert]

Re: MDO plywood for transom

Never would have thought that plywood would be come such a good topic.

 

[erikgreen]

Re: MDO plywood for transom

I think there is some confusion about the two. "Mdo Plywood is made with waterproof glue and is designed for use in exterior signs, has few or no voids and has a smooth surface of phenolic resin paper that accepts epoxy and paint or other glues without any surface preparation." That is a direct quote from the book Maintain and Improve your Powerboat by Paul Esterle.

It's worth mentioning that MDO can be used in a boat for some things very successfully... it's not a bad product. If you want to easily create a smooth, good looking surface it's very nice stuff, because as mentioned the paper accepts a lot of coatings (except poly, for that you still need to rough it up, but that's not the paper's fault).

You just need to keep in mind that the paper is meant to be a nice looking surface, not a structural component.

It's the same thing as if you built a transom using painted plywood. The epoxy or poly might stick very well to the paint, but if the paint peels off later you've still got delamination.

Use MDO for what it's meant for and it's nice stuff...

Erik

 

[jonesg]

Re: MDO plywood for transom

Heres my update. I was at the HD today for lunch. They have an exterior grade cabinet 3/4 ply from South America. There is 1 stack of the stuff on a special buy for about $25 a sheet. I'm not trying to be cheap but this is the best looking stuff I have seen. Both sides look excellent. The edges show less voids than any other ply they have regardless of the price. I have read someplace that the South American hardwood they use is excellent quality. I plan on going back to get this tomorrow.

its no good in boats except for cabin work.
I have some beech, its just pop ply with a beech laminate.
I built a casting deck with it, its already de-laminating after 1 yr.
Exterior grade ply is decent stuff.

 

[robthompson66]

Re: MDO plywood for transom

If you're really really concerned with the plywood and want to be sure there are no voids, you'll want something that is stamped with a "BS" rating instead of the APA ratings. The BS or British Standard as I believe it is also rates the core of the wood as well as the outer plys. The APA that you find at Home depot and Lowe's doesn't rate the inner layers. Try going to a plywood distributor, as most have counters for contractors. I'm outside of Detroit and I buy everything at All America Plywood. They are more knowledgeable and have a great selection. The prices that I pay there are better than Home Depot's. Home depot actually gets there wood from this place and places like these all over the U.S. They also usually don't require an account, for awhile when I started out I was just buying the wood c.o.d. at the counter.

Hope my rambling helped

Rob

 

[PaulyV]

Re: MDO plywood for transom

its no good in boats except for cabin work.
I have some beech, its just pop ply with a beech laminate.
I built a casting deck with it, its already de-laminating after 1 yr.
Exterior grade ply is decent stuff.

Its labeled exterior grade..

 

[SKIBUM1M]

Re: MDO plywood for transom

I used a new product by GP called Plytinum Dryply for my deck. It has a lifetime guarentee and seems to be a new form of pressure treating which does not leave the sheet soaking wet. It is 3/4" thick and I got it at Lowes. For my transom I used Seacast. The company was great to deal with and you said you wanted to overbuild the boat, well seacast will never rot and my transom is rock hard. When you hit it it feels like 1 inch solid steel. Just my opinions but I dont know why they still use wood in new boat construction other than they want to sell more boats when the wood rots.

 

[erikgreen]

Re: MDO plywood for transom

They use it because it's cheap.... and honestly, it's a stronger core material than most of the fancy foams. The rot is the major drawback

I used plytanium underlayment for my attempt at a scratch build in 1/4"... nice stuff, a bit more expensive than arauco. Waterproof, mostly void free, five layers of baltic birch in the 1/4" thickness. Sanded both sides.

Not sure it's the same stuff you refer to, but if it is, I like it too.

Erik