# Epoxy with any wood?



## TroutNreds12 (Jan 4, 2016)

Any reason if I'm using epoxy to coat all wood before glassing I have to use marine plywood ? Trying to keep cost somewhat down on a small boat rebuild but want to use epoxy?
Thanks in advance


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## yobata (Jul 14, 2015)

It has to do with the type of glues used to laminate the ply together. Here is a link to a build where I believe exterior grade ply was used: http://www.microskiff.com/threads/14-rivercraft-rebuild-into-flats-skiff.17276/


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## Dadvocate (Jun 26, 2011)

Lot of people on here with tons more experience but I had good luck by sealing bottom of plywood with epoxy. Then flipping over and coat with epoxy, apply fiberglass cloth and then finish wetting out cloth. Cheap bristle paintbrush to push out any air trapped. Working wet on wet when bonding and applying FG cloth saves time and wont waste as much epoxy plus better strength. My 2 cents.


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## TroutNreds12 (Jan 4, 2016)

Ok thanks does it matter type of plywood I wanted something from HD or lowes that has very little voids? Did you use pressure treated or is that not even necassary with epoxy?


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## jonrconner (May 20, 2015)

You need ply with exterior grade glue at a minimum, smooth on both sides is a big help also. I'd check prices of marine plywood first so you know how much you're actually saving.if you can get luan with exterior glue, that's probably your best alternate.
JC


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## TroutNreds12 (Jan 4, 2016)

Ok thanks may just use 3/8 meranti with 6 or 9 oz cloth on both sides. I'm in Melbourne so can order from boatbuildercentral and pickup vero save shipping won't be too bad plus with no voids will definitely save on fairing


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## Backwater (Dec 14, 2014)

Re-post your question on the "Boatyard Basics" Forum here on Microskiff. There you will find a lot of good comments from other people as well that do a lot of this.

As a reply to your original question, marine plywood is basically more durable outside (glues and wood treatment) in the elements and rain as opposed regular plywood, of course. The down side for a small skiff is it's a lot heavier. What epoxy will for any wood is, if done properly, is it will make the wood more water-proof than marine plywood or even polyester resin. So putting epoxy on marine plywood is almost redundant, in regards to the marine treatment of the wood further helping the epoxy out.

That being said, consider "fur" plywood, then epoxy and glass it. Fur plywood is about a few dollars more than pressure treated plywood, but cheaper than marine plywood. The real benefit is it has a much higher tensile strength (great for small skiff decks) than most plywoods, including marine. The biggest benefit is it's about half the weight as PT plywood and even more (maybe 40% of the weight) compares to marine plywood. You can find it in Home Depot or Lowes.

Don't just coat it with epoxy and call it good. I would consider covering both sides with 1780 bi-axle cloth and then work the epoxy into the cloth. This strengthens the deck by creating opposing forces (the strenght of the fiberglass).

Start by form fitting the plywood to the hull, whatever you are going to use it for (i.e. floors, decks, bulkheads, stringers, etc.). On a clean table or floor, run some visqueen or plastic sheeting to protect the table or floor. In the case of a deck, have the underside facing up, Precut the cloth, wet down the wood, lay the cloth onto the wood pattern (mat side down, weave side up). Pour some more epoxy (use a slow kick epoxy for extended working time). You can use a brush or epoxy mat/foam roller to spread the epoxy around evenly. Use a glass roller (with ridges) to work the resin into the cloth fibers. Finally, use a disposable squeeze to squeegee off any excess epoxy resin off the part. Make sure you coat the ends of the board good with resin. Let the resin kick and fully cure.

The next day, Grind smooth the edges. re-coat the board/deck edges with epoxy. Let it kick. Make up your own epoxy glue by mixing epoxy with cavicle glass particles/fibers. Add either the cavicel or resin to get the texture of putty. Apply and dab the putty onto the supports where you will attach the deck. With the fiberglass/epoxy cured deck bottom, place that glassed deck bottom on the supports with the putty. Apply just enough pressure so the putty will level out and fully cover the contact area of the supports where they connect with the deck part, but not too much so the putty will squeeze out. Check underneath for excess resin and wipe up the excess. Let the whole thing kick and cure.

The next day, get some 5" wide 1708 fiberglass tape (comes in a roll). The tape is what you will tab in the top of the deck to your hull sides. Make sure all the gel coat is ground off on the hull where you will glass things in. Make yo some more putty. Fill all voids where the wood touches the hull sides. Wet down the hull area and deck area where you will tab in the deck. The width of the tape will be divided into half, whereas half will be glassed to the hull (2.5") and half to the deck (2.5"). Do that along the deck where it will touch the hull or where it connects to any other part, like a bulkhead. Again, mat side down. Let it kick and cure.

Next, cut another piece of 1708 cloth and at least 1.5oz to 2oz mat cloth in the pattern of the deck. The 1708 will not bend easy over the cockpit edges of the deck, but if a bulkhead were there with the corners rounded with a grinder/sander, then it will. The 1708 (again, mat side down) will go on first. Install it the same way as I described the underneath side. As soon as that layer is done, after it kicks but before it fully cures, place the mat over it and do the same with the mat. The mat doesn't have a ton of strength but will add some bulk to the glass and it hides the weave pattern that the 1708 has once cured. Plus it sands out easier.

Finally finish it out with sandable filler, sand it out smooth, apply a good texture deck paint and whatever kind of paint, gelcoat or epoxy paint to paint it.

In the end, you may spend a little more, but it will be strong and lighter weight, for a plywood floor skiff. It will also last.

One final note. All too many times, I see guys painstakingly take the time to glass both sides of the wood they are using (and that's good!). But they will drill holes and not retreat those holes with epoxy or glass resin, before they use the holes for whatever reasons they cut them for. That is where the "Cancer" (wood rot) will start!"

On another note, make sure you have good and enough deck supports. If wood, they also have to be fully glassed in.

Good luck!

Ted


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## WhiteDog70810 (May 6, 2008)

Weight
Okoume: 40# for 4'x8'x.5"
Meranti: 50# for 4'x8'x.5"
Fir: 49# for 4'x8'x.5"

Flexibility
Okoume > Meranti > Fir

Strength
Fir > Meranti > Okoume

Ability to get a Fair Surface
Okoume/Meranti >>>> Fir

Think of okuome or meranti marine plywood as high quality hardwood plywood with exterior glue and no or very few voids. Because of the lack of voids and the natural flexibility of okoume, okoume bends cleanly, so it forms fair curves. BS 1088 is also stronger than exterior luan because of the lack of voids, so you can often use 1/4" okoume or meranti when you might otherwise use 3/8" exterior luan or 3/8" instead of 1/2", etc. For flat pieces like bulkheads, you can use BS 6566 (the voids can be a bit bigger) which is much cheaper than BS 1088. I've considered fir, but at local prices, it isn't much cheaper than BS 6566 and suppliers often only stock 1/2" in my area. You have to glass both sides of marine fir to prevent checking, so it can end up being heavier due if you didn't intend to glass both sides from the start. Others have told me fir doesn't bend well.

You must use at least exterior non-treated ply. The exterior glue is important because you will eventually damage the exterior glass and the ply core will not delaminate AS FAST when exposed to moisture. Treated ply interferes with the epoxy's adhesion.

My choice would depend on the boat. If I was just rebuilding a beater to last until I could buy something better, I'd use exterior luan. If it was nice hull I wanted to pass down to my kid, I'd use okoume or meranti marine ply. If I was making a simple boat for brutal use when strength and low cost were high priorities and weight and finish were lesser priorities, I'd use marine fir. My next boat (a mudboat) will probably be made from marine fir.

Nate


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## DuckNut (Apr 3, 2009)

All good advice above.

Only thing I would recommend is not using 1708 as it is very heavy, loves lots of resin and is very coarse. These little pieces will be a lot heavier than you think and your wallet will be lighter after it drinks up all that resin.

12 oz cloth is a better choice with a 6 oz veil to go on top of the visible areas. Much nicer to work with.

1708 is very tough stuff. Go look at some before you buy it and imagine all the fairing you will have to do. Fairing is the worst part about rebuilding. It down right sucks.


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## Vertigo (Jun 3, 2012)

I've actually built a few wooden boats. Use marine ply, okoume if possible. Seal it with epoxy and skin with glass. The effort you'll need to smooth and seal any other type of ply is not worth the cost savings and you'll not save any weight. Quality marine ply is free of voids and put together with waterproof adhesives. Sooner or later you're going to wear a few holes in the epoxy/glass skin, and good marine ply will save you a lot of problems.


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## Backwater (Dec 14, 2014)

Whitedog - I thought he was rebuilding a skiff and was seeking plywood/glass/epoxy advise. That tells me he's doing floors/decks, stringers, bulkheads, etc. Non of those components need bending. Fur/Fir is super stiff and ridged and super smooth with a very nice A grade laminate outter layer. Go pick one up and then pick up some PT or marine grade plywood and tell me what you think and which one is heavier. Also, which one is cheaper. On another note tho, as you mentioned, you can go thinner and therefore be lighter, if given the proper supports. What I like even better is sandwiching 2 thinner layers (1/4-3/8") of the plywood with a glass layer in-between. That creates more opposing forces (strength).

Duck - I agree that 1708 is somewhat thick and has ridges when cured. But it's super strong and worth the extra resin. But it wouldn't suck up any more than 12 oz mat plus a veil of 6oz. He could hold his cost in resin down by going with vinyl ester, ISO or even polyester resins, But I do prefer epoxies over those. Also consider using your glass suppliers brand of epoxy (typically boat builder's grade), as opposed to name brand, like West Systems.

Also, he can ask for grade "B" or "C" fiberglass cloth like 1708 and save a ton of money there but still get the extra strenght. Grade "A" is geared to picky high-end boat builders and the quality can push close to S-Glass, which is way more expensive. But grade B or even C is ok for DIY skiff rehab projects. It can be half the cost.

The trick with thicker mat or bi-axles like 1708 (45 degree weave), 1808 (90 degree weave) or thicker, is to use a glass roller to totally saturate the fibers, then squeegee aoff any excess resin. You would be surprise how most back yard DIY project guys use an excessive amount of resin when they didn't need to, thereby costing themselves more, making it heavier and creat spider cracks long term. Also, once the top exposed layer is kicked, the mat that goes over it will smooth it out and make it easier to fare out. He can also scuff the 1708 kicked layer first, with a grinder/sander with heavy grit pads to knock down the ridges, then go back over it with the mat (the mat is the veil), it will finish out even smoother. As you know, you will need that extra layer as the "veil" you speak of, plus it adds the extra strenght.. If you do the mat veil after the 1st layer (1708) kicks, then scuff, you wouldn't have much print thru of the texture. Then sand and fare it out. Also, most guys at that point will add a thick layer of non-skid afterwards which will further hide any print-thru from the 1708. That way, he can put more effort on edges and bulkheads to get things smooth and hide the rest of the sins with non-skid and splatter paint.


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## yobata (Jul 14, 2015)

Backwater said:


> Whitedog - I thought he was rebuilding a skiff and was seeking plywood/glass/epoxy advise. That tells me he's doing floors/decks, stringers, bulkheads, etc. Non of those components need bending. Fur/Fir is super stiff and ridged and super smooth with a very nice A grade laminate outter layer. Go pick one up and then pick up some PT or marine grade plywood and tell me what you think and which one is heavier. Also, which one is cheaper. On another note tho, as you mentioned, you can go thinner and therefore be lighter, if given the proper supports. What I like even better is sandwiching 2 thinner layers (1/4-3/8") of the plywood with a glass layer in-between. That creates more opposing forces (strength).
> 
> Duck - I agree that 1708 is somewhat thick and has ridges when cured. But it's super strong and worth the extra resin. But it wouldn't suck up any more than 12 oz mat plus a veil of 6oz. He could hold his cost in resin down by going with vinyl ester, ISO or even polyester resins, But I do prefer epoxies over those. Also consider using your glass suppliers brand of epoxy (typically boat builder's grade), as opposed to name brand, like West Systems.
> 
> ...


What is ISO? I have only heard of epoxy, vinyl ester and poly...


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## DuckNut (Apr 3, 2009)

yobata said:


> What is ISO? I have only heard of epoxy, vinyl ester and poly...


Isophthalic is a type of polyester resin


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## WhiteDog70810 (May 6, 2008)

Backwater said:


> Whitedog - I thought he was rebuilding a skiff and was seeking plywood/glass/epoxy advise. That tells me he's doing floors/decks, stringers, bulkheads, etc. Non of those components need bending. Fur/Fir is super stiff and ridged and super smooth with a very nice A grade laminate outter layer. Go pick one up and then pick up some PT or marine grade plywood and tell me what you think and which one is heavier. Also, which one is cheaper. On another note tho, as you mentioned, you can go thinner and therefore be lighter, if given the proper supports. What I like even better is sandwiching 2 thinner layers (1/4-3/8") of the plywood with a glass layer in-between. That creates more opposing forces (strength).


No argument here. I just listed the relative traits of the different marine plys because these projects can go off on unexpected tangents. Fir may be lighter than I listed, but 49# for a 1/2" sheet is what I found. I have been reading that AA fir is getting hard to find. Most seems to be BC, which can make life harder than necessary.

Nate


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## DuckNut (Apr 3, 2009)

Do not use pressure treated wood.

Also as backwater pointed out the costs could be brought down by using other resin than epoxy. If you decide to go this route you now have to listen to what whitedog was saying.

Epoxy will be the best choice for a long term build. The ester resins will eventually seperated from the wood.

Your decision. Mine would be to use 3/8 marine (pick the name) and epoxy for the deck covered with glass on both sides. For the bulkheads I would use 1/4 covered in 6oz glass stuck on with epoxy.


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## TroutNreds12 (Jan 4, 2016)

Wow!! Thanks for all the help this will just be a cheap project to use and abuse for now. Workboat finish but still would like it relatively light going to use tuff coat on all interior so not going to be doing a lot of fairing as I've done plenty in the past haha. Picked up lil 14ft vhull and trailer for 300 bucks gutted it now ready for rebuild and fish low investment for most part and fun project. Thanks again guys


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## TroutNreds12 (Jan 4, 2016)

Yobata love your build and hope to copy some of your idea....maybe I could take a look at it sometime I'm in Melbourne thought I seen you were close


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## yobata (Jul 14, 2015)

TroutNreds12 said:


> Yobata love your build and hope to copy some of your idea....maybe I could take a look at it sometime I'm in Melbourne thought I seen you were close


Yup I'm in Melbourne, sent me a PM and we will meet up


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## Backwater (Dec 14, 2014)

Post up some pics of your progress either here or on the bragging board here on Microskiff.


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