Plywood question, further insight.

studioq

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I thought the lead bars were cool... Beyond that - I'm not sure how many times a boat (other than the transom) would be subjected to those PSI forces in a normal lifetime.
 

GWPSR

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Doug and Kay rock. I've followed all of his projects.
 

bonz_d

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I took a few things from these vids. 1st off was the decision to use 3/4" ply for the test. Reason that was of interest to me is because my Alumacraft originally had 1/2" plywood decking which is 33.3% thinner. So as just for use as a deck covering that is a lot of weight supported between stringers. So far I haven't run apon a 600+ lb person and the span between stringers in this boat is only 10" which is 1/2 the span they used.

Next was the strength differeance between the marine ply and regular ply. Adding 2 more plies didn't increase the strength by much. Then was the differeance between the dry wood and the wood that had been exposed to water and wheather. Huge differeance and change!

Overall this eases my mind some about reusing only 1/2" plywood for my decking. Which also helped in my desision as to which plywood to buy. The local Menards carries a 5 ply marine sheet and a 5 ply premium sheet.
 

nurseman

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Interesting videos, I think the main thing to take away from the plywood testing is that keeping it dry is what is really important. It would have been interesting to see the same weight test on wider pieces as well, say 1 foot and 2 foot widths.
 

Woodonglass

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With a 10" span...I'd put my Big Behind in there on 1/2 Ply with NO WORRIES!!!:eek: Course' you'd prolly throw me overboard!!!!!:D:facepalm:
 

classiccat

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Interesting!

Apply the same failure modes to transom PLY; Loss of rigidity / structural integrity when the wood has experienced extended exposure...but we're not surprised are we... :D

The lamination tests were neat as well; epoxy outperformed the PLY lamination!

Thanks for sharing Bonz!
 

Woodonglass

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The Phenol-formaldehyde glues that are used to mfg Ext Grade and Marine grade plywood cure much like Polyester resin. Once fully cured they are not very flexible and really kinda brittle. i.e. Poly Resin. That's not only the wood cracking you hear when you bend plywood!!!:eek:

Epoxy on the other hand, due to the binders in its chemical makeup, remains very flexible throughout its' lifespan. That's why it's imperative that when you use Polyester resin you must use CSM so the styrene can break down the fibers and use them to molecularly bind the mix together!!!;)
 

bonz_d

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It also appears that encapsulating that plywood didn't seal and preserve the wood as well as one would suspect.
 

Woodonglass

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Remember, each layer of plywood veneer is very thin and separated by that resin glue. When you put Poly or Epoxy on top of the Plywood to encapsulate it, It might soak into the wood just a bit but not much. Even if you thin it and make it more viscous it will only penetrate as deep as the first layer. This is not true for the edges They will soak in a more viscous material. Rot Doctor's product takes advantage of this viscosity. It does hurt the overall properties of the resin but it does allow it to penetrate deep into the wood and promote preservation. Bottom line is as long as the wood is totally encapsulated and that capsule is not broken, the wood core will be preserved for a inderminate amount of time. That's why it's so important to pre-drill and coat all the holes and fasteners after you've restored your boat properly.
 

bonz_d

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Bottom line is as long as the wood is totally encapsulated and that capsule is not broken, the wood core will be preserved for a inderminate amount of time. That's why it's so important to pre-drill and coat all the holes and fasteners after you've restored your boat properly.

Agree on that point completely from all the research I've been doing over this past month and the key point also being that as long as that capsule is not broken and remains intact. Though all it takes is one fastener added and not completely sealed or one failed fastener and then the whole is compromised. Or say if a heavy object such as an anchor is dropped on it it could be punctured or fractured and again it's been compromised.

I have been concidering using CPES on my project, though only using it to do all the edges and holes as this seems to be the weakest link. Despite what some may think through the reseach I've done recently I firmly believe there is no perfect solution. The fact is that water and plywood do not exsist well together and when used in a boat it will get wet.
 
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Woodonglass

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Yah, No Perfect Solution. Like I always say, it all Boils down to Care and Maintenance. Due Diligence will lead to longevity but.. in the end ROT wins unless it's made from something that's impervious to it, and then you usually can't afford it!!!:eek:;)
 

sphelps

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What surprised me was how well the epoxy worked as a glue ...And the marine ply was only 10% stronger than the reg ply at over twice the price ...
 

bonz_d

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What surprised me was how well the epoxy worked as a glue ...And the marine ply was only 10% stronger than the reg ply at over twice the price ...

Also look closely at that glue clip. Notice the thickness or thinness of the top layer of veneer, which is what failed. How strong would that joint be on a solid piece of wood?!!!
The sheets that I've been looking at the marine is 3X the price. At what point does one lose cost effectiveness? I know and see it here all the time that it gets real easy to spend other peoples money.

Perspective,
Here I've got a 26 year old boat that I have about $1500.00 into. There is nothing special about it. Heck I see 20 or more each year for sale so it is a common boat. Of those even the ones in top shape are only valued at about $3000.00 with all the extra goodies with it. Then there is nothing wrong with the plywood that is in it now and I am sure it would last for as long as I own this boat. It just looks like junk and one of the reasons I'm pulling it up is because I want to check all the foam under it as right now the boat seems heavy. Besides the fact I want to strip it all out and repaint it! But then again some of that extra weight may be due to all the 5/8" plywood that was used in the last replacement.

I have no need or intention to build a monument of this boat. It is a fishing boat that will get worked, beaten and at times abused. Cold rainy, snowey, direct hot sun, water that still has ice flowing in it. Spring logs, debris, submerged broken pier pcs., Rocks, stumps, beachings and whatever else may come along. Besides, I've been catching just as many fish in this the way it is as those in the $30k Lunds who are afraid to go into the rock piles and stump fields.
 
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Woodonglass

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Yup, Now that the BF is done, I realize how much time I wasted trying to make her a "Show Boat"!!!! The key is to make it as sound as possible and then give it the best care and maintenance you can. Do That...And she'll last a Good Long Time!!!! Trying to make it last FOREVER is FUTILE!!!!
 
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