MDO - what is the downside?

Pete McMiller

Well-known member
I'm replacing the transom wood in a 1995 Lund. Doubled up MDO has been recommended but I've not used that material before. Plan is to incase in epoxy. Any downsides I should be aware of?
 
I'm thinking the same thing, just have to find someone who carries it. big boxes here do not.
 
Pete~


I have used MDO (medium density overlay) plywood for a pilothouse in recent years - sheathed with epoxy + 'glass on the exterior. It has weathered well over several seasons. Its surface gave a nice substrate for paint on the inside.



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And, I also used it to build a sign for the local food co-op (of which Susan was board president). I learned of MDO in my youth as "signboard plywood" - which is what it is engineered for, I believe.


All the best,


SJS
 
Pete~


No sanding needed - although a quick scuffing with 120 couldn't hurt. And, I'm sure I would have wiped it with acetone.


All the best,


SJS

 
Price is similar to doug fir AB Marine. Both are made by the same company - Roseburg. MDO was designed for exterior sign applications. MDO is the only plywood one Wisconsin boat restorer uses for replacement transoms - prior to his recommendation MDO wasn't in my knowledge base.
 
Pete McMiller said:
I'm replacing the transom wood in a 1995 Lund. Doubled up MDO has been recommended but I've not used that material before. Plan is to incase in epoxy. Any downsides I should be aware of?

HI Pete. I used MDO from Menards on my Starcraft floor replacement 10 years ago. It was great stuff with no voids that I saw when cutting the floor boards. My next project I was not impressed. The MDO I bought from Menards for a camper upgrade was full of voids. None over 2" long but there were many. It worked fine for what I was doing but I could have used exterior AC plywood and saved some money. Not sure I'd trust it for a transom now.
 
Hi Ed, Thanks for your input. The MDO looks good so far. All cut, shaped and ready for epoxy today. Both the A/B Marine and the MDO are made by Roseburg, Oregon. I've used their products before without a problem - I hope my expectations are not misplaced.

I was turned on to MDO by a gentleman here who's business and career has been restoring wooden boats (Chris Craft). He has always successfully used MDO for replacement transoms, nothing else.
 
Pete McMiller said:
Hi Ed, Thanks for your input. The MDO looks good so far. All cut, shaped and ready for epoxy today. Both the A/B Marine and the MDO are made by Roseburg, Oregon. I've used their products before without a problem - I hope my expectations are not misplaced.

I was turned on to MDO by a gentleman here who's business and career has been restoring wooden boats (Chris Craft). He has always successfully used MDO for replacement transoms, nothing else.

Sounds good Pete. I've yet to get started on mine. Living on a island one waits until the flood season is over before diving into projects. Please show some photos of your process and progress. Inquiring minds want to know. How did you remove the scupper tubes?
 
Ed, I couldn't wait any longer, I've got a fishing trip to Lake Erie coming up in early May. The total shocker for me was how much of the transom had turned into "worm bedding", at least 60-70%. I went through most tools in my toolbox trying to figure out what's going to work. As it turned out, a 3 ft crowbar and a 1 3/8" spade bit on a 12" extension were the two most important.

In my case, there were 22 SS bolts that I had to drill the heads off and push through to the inside - blind compartments.

The scupper tubes were surprisingly easy after finding a how-to on YouTube. Basically a cold chisel tapping the flange to the center and pounding the whole thing out the other side.


View attachment 20210225_145737.jpgView attachment 20210225_145551.jpg
 
Pete McMiller said:
Ed, I couldn't wait any longer, I've got a fishing trip to Lake Erie coming up in early May. The total shocker for me was how much of the transom had turned into "worm bedding", at least 60-70%. I went through most tools in my toolbox trying to figure out what's going to work. As it turned out, a 3 ft crowbar and a 1 3/8" spade bit on a 12" extension were the two most important.

In my case, there were 22 SS bolts that I had to drill the heads off and push through to the inside - blind compartments.

The scupper tubes were surprisingly easy after finding a how-to on YouTube. Basically a cold chisel tapping the flange to the center and pounding the whole thing out the other side.

Thanks for the photos and insight. Chiseling the scupper tubes sounds less time consuming than what I've done in the past. Ill keep that one on the short list. Looks like you have it well in hand. You should easily meet your fishing trip deadline.
 
I was fortunate that one corner came out intact enough that I was able to trace the perimeter onto cardboard. Some additional measurements got me to the centerline. After determining that the cardboard was accurate, I transferred it to 1/4" sacrificial luan. The luan mock-up told me that my measurements were correct and, just as importantly, that I could get both transom panels to make up the 1 1/2" thickness out of one sheet of MDO.View attachment 20210310_103417.jpgView attachment 20210310_103444.jpgView attachment 20210310_103537.jpg
 
I appreciate your input Fred. I hadn't considered Coosa board because I thought it might be a little expensive. Well I checked it out today - holey moley it's almost 10X the cost of MDO. In any case, the MDO has been cut, doubled, epoxied and set in place.
 
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