Epoxy or varnish

[pcatterall]

Hi all,
Starteed to repair my wheelhouse side last week. Thought I would be able to repair the delamination of the 30 year old ply.
Gave up in the end as it was too far gone, took the whole panel off.
I have made a new panel with 3/4" marine ply and am considering the best treatment. I certainly propose to use epoxy around the edges and into the screw holes. Some areas were varnished and I would like to have this effect on the new panel.
Can I use epoxy like varnish? does it need further protection?
Can I thin the first coat and if so with what?
Thanks (as usual) guys
Regards

 

[alb40]

Epoxy has no UV resistance, so it cannot be used as a varnish.

However, it is worth coating the ply (especially the end grain) in the epoxy to seal it. After the ply has been coated, apply varnish over the epoxy to provide the UV resistance.

It will look good, and because the varnish is on the epoxy, not the wood, it will last very well. Keep it maintained though, otherwise the epoxy will fail if the UV can get to it.

 

[wooslehunter]

Epoxy can work great or can be a real pain.

I did a couple of new washboards a couple of yeasr ago. Within 2 weeks one had stared to lose its epoxy and by the end of the season was looking like it had been there for years. the other, done at the same time and cut from the same piece of ply was still perfect.

Did them both again over last winter and they still look great.

This isn't the first I've heard of epoxy being a pain to work with.

So epoxy done right and then varniched will last far better and look great. Varnish is far easier to work with but will need regular maintenance to keep its looks.

 

[oldsaltoz]

G'day Peter,

We would go about replacing the section as follows:
Cut the new sheet to size and dry fit to ensue no further cutting or sanding will be required; because we don't want to break into the epoxy finish and have to re coat it.

You can thin Epoxy resin, first measure your resin and mix in the hardener then add up to 40% Methylated Spirits by volume, this is good for penetration work, start on the edges and then the upper face and finish on the edges. This will complete one side, let it cure for 24 hours or more and turn it over to do the other side, alternatively you can stand it up and leave the bottom edge till last. We prefer to lay the sheet as the penetration is deeper. Note: the edges will keep soaking up the resin, so apply more as soon as it looks dull or the wet gloss look goes, keep applying more till it stays glossy.

You should apply at least 2 thinned coats and one full coat as a minimum, we like to apply two of each.

To avoid having to wash and sand between coats you should apply wet over tacky, so make small batches to avoid resin waste.

Any cured resin must be washed with running water (a hose) and kitchen scourer, the green ones with a yellow foam backing are good, start at the top and rub till the water no longer forms beads like a you see on a waxed car after rain. This removes the residue left by the curing process and avoids the use of chemicals.

When all coats of the Epoxy have been applied wash as above and sand with a 200 or 300 grit, just enough to remove the high gloss finish, this will provide a good key for the varnish (or paint) to be applied. Note: if you plan to paint over an Epoxy you should apply a coat of high build epoxy primer first.

I hope this helps.

Avagoodweekend......

 

[ccscott49]

You do not get a better explanation than that! Heed him well!

 

[pcatterall]

Yes, what a mine of good practical information OSOZ is.
Many thanks to you all.
Regards
Peter

 

[LittleShip]

One "trick" used in the States when they use CPES which is a penetrating epoxy is to put the first coat of varnish on before the epoxy has gone off. It seems that the varnish then bonds too rather than sticks too the epoxy.

Probably worth testing a small piece before you do the whole job!

Tom.

 

[wagenaar]

I find the term "methylated spirits" every now and then, but don't know what it is. My "old" rubberbible" does not mention the word either, so could you explain it to me. I think it is CH3OH, but would like to be sure, before using it to dilute epoxy.

 

[oldsaltoz]

[ QUOTE ]
I find the term "methylated spirits" every now and then, but don't know what it is. My "old" rubberbible" does not mention the word either, so could you explain it to me. I think it is CH3OH, but would like to be sure, before using it to dilute epoxy.

[/ QUOTE ]

Methylated spirits ("metho") is a mixture of ethyl alcohol (95%) and methyl alcohol (%5). The methyl alcohol is poisonous and is added to prevent the methylated spirits being used as cheap drinking alcohol.

Avagoodweekend......

 

[oldsaltoz]

[ QUOTE ]
One "trick" used in the States when they use CPES which is a penetrating epoxy is to put the first coat of varnish on before the epoxy has gone off. It seems that the varnish then bonds too rather than sticks too the epoxy.
Tom.

[/ QUOTE ]

Almost any top coat that compatible with the first coat will bond, we add the first coat of antifoul to a tacky high build epoxy and have never any problems.

Avagoodweekend......

 

[LittleShip]

Thanks old............. I was trying to say there is a difference between bond and stick /forums/images/graemlins/confused.gif which I "think" you have agreed with! I have to be honest here and say I have never tried this method for varnish, but there is a first for everything!

Tom

 

[wagenaar]

Thanks for your explanation. Basically methylated spirits is ethanol with just a bit of methanol added to make it bad for one's health. I assume that the actual percentage of methanol is not important, within limits. Whether it is 0 or 5 percent will not influence its function in diluting the epoxy..