What material to make a (simple) companionway sliding hatch from?

[Amulet]

I made one out of ply. See click. It is still going after 13 years. It will be better to bend two 6mm sheets of marine ply with epoxy between. I'd think near impossible to bend an 18mm sheet. Mine is actually laminated out of three sheets, but I expect to be able to walk/jump on it, and it has no intermediate cross members.

The main advantage of the 207 West hardener is to improve the flow characteristics for coating, and it is what you need if you coat with epoxy. I wouldn't coat with epoxy. It is not tolerant of UV and degrades unless protected. I did mine with epoxy (as shown in photo) and subsequently stripped it and did it with two part polyurethene varnish. If had the time and patience I'd have done it with Epifanes.

If you decided against this approach for maintenance reasons you might be able to take a mould off the old one to make a new one out of GRP. The other klutzy method (which may not have to end up looking klutzy) would be to dry it out thoroughly (heat gun etc.), soak it in epoxy to stabilise it, and then sheath it with glass fibre cloth.

 

[Amulet]

Sorry, hadn't read your last post..... I wouldn't coat it in epoxy outside for the reasons above. You'd still have to coat the epoxy with something else to protect it from sun ( it does sometimes shine ). My dislike of epoxy coating is not blind prejudice. I started off coating everything in sight with epoxy and have removed it all over the years.

N.B. You should NOT regard sealing on the underside as a way of keeping water out. You must seal the outside. If water can get into the timber from above but not get out from below you will have optimised the conditions for rot. There are even those who say that the underside should never be sealed for this reason. I'm not that extreme.

 

[TQA]

Hi all,
So I have pulled the bottom (underside) surface of the hatch off (ply), and found I actually have a fairly solid hardwood frame and also the 'slats' make up the curved surface of the lid (about an inch wide, running fore/aft across the top) are about a centimetre thick and also sound. Pictures below - apologies about quality, phone is old!


View attachment 55290View attachment 55291

There were two ply stringers (yes, ply) running across the middle which were rotten, but the hatch still seems pretty strong without them. A 13 stone friend stood on the top with both feet (after the stringers were ripped out) and nothing moved.

His suggestion is that I simply sand it off and put a generous layer of epoxy to the UNDERSIDE of the hatch to form a seal across all the slats (watertightness) and add some stiffness. Then likewise on the outside epoxy coat.

What do you think of this?

How much epoxy do I need (roughly)? I have a 'junior pack' of west at the moment, do I need to go out and buy say a 1kg?

I have also read that where you want a 'transparent' finish (to show off the wood) you should use 207 hardner rather than the 205 hardner that comes in most small packs - is 207 the one to go for?

Perhaps a dumb question - do I need to be mixing in microfibres to stiffen up the mixture? Will they affect the colour/transparency of the finish? (I happen to have just bought some microfibres, 403 i think, for another job)

Another dumb question - should I varnish the wood first, to get a colour, then epoxy over... or just epoxy straight onto the sanded wood? I am imaging the latter for mechanical reasons.

Cheers,

Trev

You need to protect epoxy from UV, so epoxy first then varnish. HOWEVER most who go down this route end up regretting it because if the epoxy fails you get black stains and it all has to come off if you want a good finish. Removing epoxy is a right b*******. So epoxy then paint with a good quality UV resistant paint. I have never tried 207 but I live in the Caribbean where the UV is fierce.

As for fillers microfibres or any wood fiber will color the epoxy. Only a problem if you go down the varnish route. Some save their sawdust in hopes it will match but sadly it does not. Still a small economy. Me, I use microballons because it is easy to sand.

Word of warning when using West, it is prone to " amine blush " so follow the guidance given here http://www.westsystem.com/ss/surface-preparation/