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

[Trevelyan]

Hi all,

I have a rotten companionway sliding hatch which I am going to throw away and start afresh. It has "C" section tracks fitted to the coachroof and t shaped tracks which slide in them, old t-tracks are damaged plastic so a pal is making some replacement long slider blocks out of plastic (perspex?PTFE?) to replace them. So the question now -having the sliders sorted- is what do I make the hatch out of? A sheet of ply with some edging strip? A sheet of acrylic with some edging strip? My main aim is to make it easy and low maintenance - pretty not required!

Cheers,

Trev

 

[pmagowan]

Hi all,

I have a rotten companionway sliding hatch which I am going to throw away and start afresh. It has "C" section tracks fitted to the coachroof and t shaped tracks which slide in them, old t-tracks are damaged plastic so a pal is making some replacement long slider blocks out of plastic (perspex?PTFE?) to replace them. So the question now -having the sliders sorted- is what do I make the hatch out of? A sheet of ply with some edging strip? A sheet of acrylic with some edging strip? My main aim is to make it easy and low maintenance - pretty not required!

Cheers,

Trev

Ply will be easiest. You can make it square or give it a camber to help shed water. It is simply a matter of making a simple frame out of solid timber and then placing the sheet of ply in it. Then treat as required with your proprietary finish such as coelan, epiphanes or just plain paint. The plastic runners will be ptfe if they are good.

 

[Trevelyan]

Thanks for the reply - I was thinking that something like that might be simplest (although if I made something out of acrylic it would be zero maintenance). Any advice on the thickness of ply please (~18mm?)? Is there any particular grade of ply I should be looking for? What kind of timber should I be looking for for the frame? Don't want to walk into a wood merchants entirely green as grass...!

Cheers,
Trev

 

[Tranona]

Personally I would go for Polycarbonate (tinted). You don't say whether you have the framework, but the success of a sliding hatch depends on a really sturdy frame, so the it is both square and fully supports the top. Central fore and aft and two cross beams with a 10mm curve athwartships. 9mm Polycarbonate screwed down onto butyl tape to seal. I made one like this over 30 years ago and still going strong.

 

[Scotty_Tradewind]

Ply - NO! it's the last thing you want to fit if you shun high maintenance.

If you have a large GRP boat maker nearby, it might pay to give them a call to see if some of their offcuts are big enough.

I did this and gained enough sheet to do many jobs on my boat.

Some big cat's have huge cut-outs from their mouldings to fit windows etc..

S.

 

[AndrewL]

It would be useful if you could attach a photo of the current sliding hatch.

I rebuilt a sliding hatch earlier this year, mine was curved to complicate matters. There was a solid wood frame which I reused. I created the curved surface by gluing together three layers of 3mm ply. To make it weatherproof I gave it a clear coat of epoxy, then sheathed the outer face with epoxy & glassfibre and finally painted.

I was very pleased with the result and so far after nearly a year outside it is still good.

 

[KellysEye]

Ordinary ply is that open to the weather will eventually rot so make sure you buy marine ply and make sure it has a guaranteed life. Personally I would use teak and stainless steel runners, which we had, and will never need replacement.

 

[Trevelyan]

I might be able to re-use the old frame, it had a curved top made out of about inch wide slats running fore/aft (caulked in-between), so no wonder it ended up leaking. I could either try taking those slats off and bending thin sheets of ply over the top and gluing together to make a thicker layer - but frankly that sounds like work to get a good finish to the edges etc. Plan B is to take the slats off, cut the frame (to take the curved top off the sides that run left to right) so that it will take a 'flat lid' sheet of either ply or perspex. Is a flat lid really much of a disadvantage for water runoff etc? I'm not really worried at if it looks pretty or not, as long as it works!

I will try to get a photo...

Trev

 

[Scotty_Tradewind]

Hi Trev',
Any curve in the hatch will add slightly to its strength.

Now retired, I have built my own woodwork shop in my garden(man shed )
I used to build boats, I used to teach woodwork, then CDT, then Design Technology.
I have helped my son become a most successful cabinetmaker, I love wood and things of quality made of it.
I respect those opinions and recommendations given in this thread for wood plys or wood laminates, but from your description and explanation of your task, I would still avoid it.

Tranona talks a lot of sense to me........
Personally I would go for Polycarbonate (tinted). You don't say whether you have the framework, but the success of a sliding hatch depends on a really sturdy frame, so the it is both square and fully supports the top. Central fore and aft and two cross beams with a 10mm curve athwartships. 9mm Polycarbonate screwed down onto butyl tape to seal. I made one like this over 30 years ago and still going strong.
Read more at http://www.ybw.com/forums/showthrea...ionway-sliding-hatch-from#UVIl2ZPOD5StlKuL.99

How about this? A material that will last for hundreds of years!
Why small external wooden fittings are not now made of this on boats today is probably down to weight and cost, but for the small amount you need, you may get away with less than £100 quid, with very little skill, time and treatments to fit or maintain it.
http://www.ebay.co.uk/itm/TUFNOL-Wh...te-Cotton-fabric-based-laminate-/161443450307

2 or 3mm sheet with a slight curve ..... only the substrate will need any maintenance.

S.

 

[Sarnia]

Personally I would go for Polycarbonate (tinted). You don't say whether you have the framework, but the success of a sliding hatch depends on a really sturdy frame, so the it is both square and fully supports the top. Central fore and aft and two cross beams with a 10mm curve athwartships. 9mm Polycarbonate screwed down onto butyl tape to seal. I made one like this over 30 years ago and still going strong.

I recently replaced similar hatch, was acrylic, scratched and glazed, with a polycarbonate one 10mm
Was lucky as the supplier had some off-cuts from doing a security job (its pretty much bullet proof) which he cut to size for me, 10 pound cash.

 

[Trevelyan]

Hi Scotty - when talking about a polycarbonate hatch you seem to have given a link to this thread (unless I am having a daft moment) - could you give the link that you intended please? Sounds interesting! How difficult is the polycarb to bend?

Cheers
Trev

 

[30boat]

Ply is not a good idea.Mine is solid fibreglass.I used the old cracked one as a mould because it had to be curved.Simplicity itself to make and very strong. Mat and rovings until the desired thickness is achieved.

 

[Daydream believer]

If you use 9mm polycarbonate there is no need to bend it. Just leave 2 drain slots in the aft corners.
Perfectly strong enough. - Mine is flat & OK to stand on. I would suspect tufnol to be a little slippery as it is often used as a bearing material when lubricated by water. I have made new bearings( thrust washers) for my saildrive rope cutter on my lathe from tuffnol & they last a couple of seasons before needing renewal. So are designed to be slippery when wet. That suggests that you could use 2 strips as sliders to take the weight of the hatch so it is not bearing on the side runners

 

[TQA]

Lot of guff on here about ply rotting. Sure it will if you leave it untreated.

Slather three coats of epoxy on any end grain. Put the thing together with epoxy, followed by two three coats of epoxy and finish with some white paint.

I am looking at three old Wharram cats built that way. The youngest is 20 years old. Still looking OK.

 

[smithy]

Your slide set up sounds the same as mine, probably sections of mast track. Rather than making new internal slides I used four "Allslip" slides fixed to the hatch, they have been working well all year. It might save you a bit of time.
[URL=//http://www.bainbridgeint.com/Item.aspx?Item=PRD-900072&PartNo=A108

 

[Tranona]

How difficult is the polycarb to bend?

Cheers
Trev

It will bend OK if you follow my suggestion of just a 10mm crown athwartships. Screw it to the centre spine and the crossbeams at roughly 75mm centres and you will find it will pull down to the edges OK. Don't go any thicker than 8 or 9mm thickness or you will have trouble without heating it.

 

[Trevelyan]

How did you fix the slides to the hatch smithy? That is indeed the same set up as mine - the previous owner had used some sail track slides and then wood glued them into slots in a batten - a good idea apart from the fact the batten rotted! Trev

 

[Trevelyan]

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!




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

 

[smithy]

I cut housings into a batton then held the slides into this with screws and epoxy. The battons are screwed on from the outside of the hatch and are hidden from view. The water cant get at them so no chance of rot. If this is difficult to follow I can draw it out.

 

[Scotty_Tradewind]

Hi Scotty - when talking about a polycarbonate hatch you seem to have given a link to this thread (unless I am having a daft moment) - could you give the link that you intended please? Sounds interesting! How difficult is the polycarb to bend?

Cheers
Trev

Somehow it came from Tranona's link.... pl's ignore mine..
S.