Encapsulation question

[Safari]

Hi,

I'm currently cutting out all the pieces of plywood that will be used in my re-flooring project.

I plan to coat all the surfaces with thinned ( to rubbing alcohol consistancy) poly resin. This, will then be catalyzed with a reduced amount of MEKP to allow for a longer kick time, hopefully allowing the resin to penetrate the wood fibre befor curing.

My question is ; when you fellows say "encapsulate", do you mean to cover both top and bottom of the plywood floor with mat?

Or, do you mean to apply a coat of the resin mixture to all surfaces followed by the mat on top?

Thanks for any help.

 

[sdunt]

Re: Encapsulation question

Dictionary wise encapsulation means to coat all sides. I would recommend that you use some type of mat, very thin with that resin. What I found when I pulled up the floor in my boat, granted the boat is from teh 1960's, was a coating of resin that had been painted on with out matting and the resin just peeled off the plywood.

I do not know the technical answer, but there is a limit to how much you can thin resin and have it still be effective.

It is interesting that Jim anderson in his book Runabout Renovation recommends that you treat the bottom of the floor with a wood preservative and leave it 'bare'

 

[fishingdan]

Re: Encapsulation question

Encapsulate the wood with epoxy. Poly resins don't bond well with wood.

 

[JasonJ]

Re: Encapsulation question

Poly bonds fine with wood. What I do is coat the surface liberally with poly, immedialty lay mat, then wet the mat out with more poly. This helps to prevent the wood from wicking the resin out of the mat, and creates a single layer that is bonded with the wood. I am not a fan of coating, letting cure, and laying subsequent layers with poly, too many secondary bonds. I also don' t thin my resin either, but I do mix for a longer cure so the resin can soak into the wood for a good bond. I have ripped plywood apart without the bond failing doing it this way. Epoxy is great stuff, but it is not the end-all of boat repair, it just makes things easier at a higher cost.

 

[Safari]

Re: Encapsulation question

Thanks for the replys.

The reason I was thinning so much was due to a long ago post by jimmythekid. He had used this method. After all was said and done, however, there remained the usuall poly vs epoxy proponents comments.

This boat is almost 50 years old, the flooring was secured to the stringers with nails, not screws, the underside of the ply was not even painted. The top of the floor did have mat and resin though and yet it has lasted all these years! I am truly amazed at how long it has lasted. But, there is stringer damage from being left outside with a leaky floor for years and years by the previous owner.

With all this in mind, I was wondering if only resin on the underside would suffice?

 

[epresutti]

Re: Encapsulation question

Safari,

On my rebuild (and for my own piece of mind), I coated the underside of all wood on the boat with epoxy resin and a layer of 3/4oz matt. I laminated it the same way I did the topsides. After the glass was set I flipped it over and installed on the stringers.

If I had to do it again, I would probably use poly, mostly because of the cost, and after reading many varying oppinions on the topic of poly vs. epoxy vs. vinyl. In my humble oppinion using a layer of glass with resin (of your choice) is definately the way to go.

Peace.

Ed.

 

[rottenray6402]

Re: Encapsulation question

I don't mean to high jack this thread but does anyone think that the reason Jim Anderson recomends coating the underside and then leaving it bare would be if there is a layer of glass on the underside all it would take would be a small pin hole to let moisture in and then it would be trapped between the glass and the wood? The bilge area is like a sauna all summer so once moisture got between the wood and glass it would keep rotting the wood?

 

[sdunt]

Re: Encapsulation question

Rottenray,

I had wondered about Jim Anderson's reasoning myself, there is no explaination in his book. I have heard mixed reviews on sealing only one side of a piece of lumber. Some say it lets the moisture out, other say it lets moisture into the wood.

It should be pointed out that Jim Anderson also said that when using his methods, you must install vents through the floor so air can get under the floor and dry things out.

 

[ondarvr]

Re: Encapsulation question

Do not thin the polyester resin, leave it as is, thinning will only degrade the product, if you were to thin it, use only styrene and only about 3%. Even with styrene, if too much is added it will only weaken it and make it brittle.
Studies on epoxy show that thinning degrades it and allows the wood to absorb a higher percentage of water, so over thinning anything is not a good idea.

Precoating the wood will allow the wood to absorb all the resin it wants, without the possibility of a resin rich, or resin starved laminate. When laminating over wood, sometimes as the resin cures it creates enough heat to expand the air in the wood, this will cause air bubbles to form under the laminate that will need to be repaired, precoating helps to ellimnate this problem also. The natural resin in some wood can retard the cure of resin, so if you precoat you will know if there is a problem. Secondary bonding can be an issue if the surface is left for a long period of time, or is contaminted in some way, but that's normally not a problem when doing a floor.

I would do both side of the floor unless you are planning to have very good air flow under it.

 

[Safari]

Re: Encapsulation question

ondavr:

You say not to doesn't, but doesn't sence make sence to have the resin in contact with the wood for a long period of time to allow for absorption?

In JasonJ the response interpreting JasonJ, I am interpretting his comment to mean use less catalyst so as to delay the cure for a longer period of time. are you in agreement with that? I see teck you were a teck rep for this stuff so I respect Jasonj opinion greatly.

Jasonj:
further
Thanks for the info, but going futher, did you coat both sides of your plywood epresutti mat or just the top? poly

epresutti:

I am going the poly route due to the cost issue. I surely recognize the advantages of epoxy however, after reading a lot of poly posts I am of the opinion that if done properly, the Unfortunately will work satisfactorily. That's why I have all these questions.

Unfortunalely, this is just the beginning. I was out working in the boat today and saw big time rot in my center stringer in places. Now doubt there will be many more questions in the future.

 

[Terry Olson]

Re: Encapsulation question

Head over to www.glenl.com and check there for advice. Those guys build with nothing but wood and I'm sure you'll find plenty of great advice there.

 

[Safari]

Re: Encapsulation question

ondavr:

You say not to thin, but doesn't it make sence to have the resin in contact with the wood for a long period of time to allow for absorption?

In reading the response from JasonJ, I am interpretting his comment to mean use less catalyst so as to delay the cure for a longer period of time. are you in agreement with that? I see that you were a teck rep for this stuff so I respect your opinion greatly.

Jasonj:

Thanks for the info, but going futher, did you coat both sides of your plywood with mat or just the top?

epresutti:

I am going the poly route due to the cost issue. I surely recognize the advantages of epoxy however, after reading a lot of back posts I am of the opinion that if done properly, the poly will work satisfactoraly. That's why I have all these questions.

Unfortunalely, this is just the beginning. I was out working in the boat today and saw big time rot in my center stringer in places. Now doubt there will be many more questions in the future.

 

[ondarvr]

Re: Encapsulation question

Resin is from 35 to 50% styrene when you buy it, most over the counter products are 43+, so there is already a lot of styrene in resin. Styrene does cross link with the resin molecules, but is not as strong or flexible as resin itself, so the more you add the weaker the resin. The resin has been formulated with the correct amount of styrene to achieve the best results. The no sag type resins are thicker, you don't want to use one that says that on the can.

On precoating, go to the lower end of the scale for catalyst, about 3/4%, this should let it soak in long enough. If you go lower than that, the resin may appear cured, but may not have crosslinked completely, this will leave it weaker and less water resistant. you can do it in the cooler part of the evening so it will cure a little slower.

When I say precoat, I mean apply the resin (unwaxed type) and at least let it start to gel (it's best to let it harden though)before putting the glass laminate down. If you only have waxed resin, then don't wait for it to harden completely, it needs to still be tacky when the next layer is applied.

 

[Kevin70]

Re: Encapsulation question

There were a lot of glass boats made without using epoxy. The majority of them lasted over 20 years (mine being one of them) I will be coating with resin, allowing it to harden, sanding with 120 grid, then doing the mat and roving thing.