Newbie Redecking question (Plywood and sealant)

[Chaser 32]

A good quality polyurethane spar varnish is worth the cost. There are many that say spar varnish, you just have to look at the UV rating on them. I spent 2 weeks drying 6 layers of spar varnish over 1'' of plywood, and its as durable as a solid chunk of metal. It depends on what your exposing your boat to. Look, there is no permanant fix for a decking or transoms; otherise there woud be no post about it. If you spend $150 on cheap plywood thay you laminate yourself to make 3/4 in. and cover it in carpet, it will last you 2-4 years, maybe more, depending on how much moisture you expose it to. You can go and spend $500 on what is called quality Marine grade plywood" and in 10 years you'll be replacing it again assuming you still have the boat. What I am getting at is, look at the cost/value ratio. Is this a party boat for a bit or something you hope to pass to your grand children... if you get my drift.

 

[MH Hawker]

sealing the wood holds water in and makes it rot faster get some marine ply lay it down and go on with things, marine ply is good for 20 years all by its self, no need to re invent the wheel

 

[Scott Danforth]

go to Menards and get their premium ACX plywood. its AraucoPly and its much cheaper than MDO or marine. (I really wish there were Menards south of Tennessee)

then treat with Woodonglass old timers wood preservative formula of 1 part linseed oil, 2 parts mineral spirits and 1 part spar varnish

install the deck and go boating. in another 30 years when the wood goes bad again, you will have long sold that pontoon

 

[ondarvr]

The UV rating of a product has nothing to with it being waterproof (nothing is water proof, there are just varying levels of water resistant) or it's durability. Plywood under carpet is about the harshest environment there is, if the ply is going to be sealed, it needs to be done with an actual water proof product that can hold up in that environment.


​The issue with ply in this situation is that the water barrier needs to be as water proof as possible, and epoxy does that, but every screw hole and other penetration needs to be sealed or the barrier is compromised and water finds the plywood, this makes the barrier almost worthless. This also includes all the incidental damage from dropping stuff (anchors, motors, camping gear, etc.), it's almost a no win situation. I renovated a toon recently and the 20+ year old ply was very good condition, we reused it and went with diamond plate aluminum over it, I've seen others with bad decks much sooner.

​I try to go with the best ply the budget will allow, and also consider how long I really need it to last, or make it easily replaceable and go with a lower cost material. The "for ever" product would be a plastic (composite) that will cost a fortune.

 

[domwebhost]

go to Menards and get their premium ACX plywood. its AraucoPly and its much cheaper than MDO or marine. (I really wish there were Menards south of Tennessee)

then treat with Woodonglass old timers wood preservative formula of 1 part linseed oil, 2 parts mineral spirits and 1 part spar varnish

install the deck and go boating. in another 30 years when the wood goes bad again, you will have long sold that pontoon

I am guessing this is a homebrew mixture as a Google search comes up with no results as far as a brand name. How many applications to treat would you think? Dry time between applications?

 

[Scott Danforth]

search iboats for old timers wood preservative.

for what its worth, my buddys pontoon which gets 400 hours of use a year is running on non-treated ACX from menards. been fine for the past 20+ years, will most likely be fine for another 10-15

 

[ahicks]

Also, when I lay the ply should I stagger the vertical seams (the ones going from bow to stern)?

Using 4x8 ply, there should be no seams going from bow to stern, unless I'm missing something.

 

[domwebhost]

Using 4x8 ply, there should be no seams going from bow to stern, unless I'm missing something.

Good to know. I didn't know if there were some reason to cut the sheets and stagger the seams. I'm a newbie but I'm learning.

 

[ezmobee]

If you can get MDO I'd go that route. Someone recommended Arauco ply. I have used that and it's a beautiful product and has like no voids but unfortunately it's made with soft wood so it's going to be more rot prone than others. If you go with a more robust flooring like marine vinyl as opposed to carpet you'll get even better life still. My Starcraft deck is still rock solid and like new after 8 years - regular exterior ply, epoxy resin sealed, marine vinyl covering.

 

[domwebhost]

No Title

search iboats for old timers wood preservative.

for what its worth, my buddys pontoon which gets 400 hours of use a year is running on non-treated ACX from menards. been fine for the past 20+ years, will most likely be fine for another 10-15

I tried to do a search on iboats for the terms you stated but I did not find anything (see attached image)

Perhaps it is this? http://forums.iboats.com/forum/boat...g-and-hull-repair/10017033-old-timers-formula

 

[domwebhost]

Old Timer's Wood Preventative (from what I could find)

1 part spar varnish (Helmsman or something like that)
1 part boiled linseed oil
2 parts mineral spirits

After applying this to all six edges
Then, I am to put at least 3 coats of spar on all six edges as well.

The post does not mention how many coats of the 3 part mixture is to be applied. 2? 3?
Also, won’t the mineral spirits thin out the spar and if so would it be better to spray apply or roller/brush it then?

I am wondering what the coverage would be for this concoction. Maybe I will just go with a gallon of spar, a gallon of boiled linseed oil and 2 gallons of mineral spirits in a five gallon bucket and see how far that gets me? Then, finish up with three coats of spar rolled on all edges?

BTW- I had to do a Google Search for it in iboats because for some reason I was just coming up with the 4 results.. I am guessing because the Google result used the terms "Old Timers Formula".

 

[domwebhost]

Looking on other posts I seem to have found a breakdown of the technique (another piece to the puzzle---yay!)

Apply liberally until the wood seems to have soaked it in and won't absorb any more. Let it dry for 2-3 days and then apply 2-3 full strength coats of urethane. (this comes from Woodonglass 's reply on a post about whether the formula should be used on hardwood such as oak.)

 

[jbcurt00]

Yep, can be used @ply too

 

[Scott Danforth]

you can pump it in an airless sprayer and shoot it, you can also put it in certain garden sprayers and hose it on. I roll it on with a thick roller, preferably over a gravel driveway or a drop cloth

 

[leorupp]

Has anyone used a bed liner type of material to seal the deck ...like on the bottom side...rhino lining ????

 

[domwebhost]

Great to know and thank you all. I am going to start a new post showing the restoration of this boat. That is not to say that I won't be coming back here to let you guys know how your advice has helped me with the decking Here is the new thread URL if anyone wants to subscribe/check out the progress. http://forums.iboats.com/forum/gene...0420018-1989-starcraft-bass-buggy-restoration

 

[Chaser 32]

Spar varnish isn't a great waterproof finish, it needs to be reapplied fairly often for it to retain any amount of it's water resistants'. If there's going to be carpet over it, spar varnish won't help much at all.

​Check the online pontoon boat sites for ply designed for this purpose.

Why do you say that Spar Varnish isn't a great waterproof finish? I'm curious if you may have had some bad experiences using it.

 

[NYBo]

This thread has me wondering if I should seal the underside of the deck of my new-to-me pontoon boat.

 

[ondarvr]

Why do you say that Spar Varnish isn't a great waterproof finish? I'm curious if you may have had some bad experiences using it.

​Because it's not that waterproof, nor is it very strong. Wood expands and contracts a great deal as its moisture content changes, spar varnish is somewhat waterproof, but the wood will still absorb moisture and swell, then the SV cracks, which allows water into the wood, this is why unless you reapply it occasionally it doesn't hold up. If it worked well people would use it instead of epoxy when building wooden boats.

 

[jbcurt00]

This thread has me wondering if I should seal the underside of the deck of my new-to-me pontoon boat.

Lots of opposing views on that, sort of like asking about ethanol gas or what oil to use.....