marine ply - what? how? who?

[ChasB]

I'm going to need to buy some marine ply to make up some replacement exterior window 'frames' (see this thread ). I need six pieces of about 18" x 9".

The frame looks rather like the aluminium one in this photo

1) Any ideas about suppliers? (I'd like to avoid having 2m x 1m sheets delivered!)

2) what's the difference between marine ply and high grade ply from a timber merchants? I know some boatyards don't use marine ply, like Lindon Lewis get their timber from Jewson's - an inexpensive builders merchants.

3) any tips on working with it?

 

[Alrob]

as far as I recall the differance between exterior ply & marine ply is the glue between laminates

oh and by the way Jewson are about the dearest builders merchants on the go, I always avoid them unless Im stuck

 

[Poignard]

If you need a really high quality plywood, I'd suggest Robbins Timber Ltd, Bristol [see website]. They would cut it up for you, I'm sure.

 

[santeana]

The big supplier oft recommended here is:
http://www.robbins.co.uk/Pdf%20Files/Marine_FSC_0607.pdf
However I've always found Ken Howells of KJ Howells & Son of Poole far more helpful and cheaper. BS 1088 (the marine standard) seems to have become of questionable quality in comparison to 20 years ago. Talk to Ken on Tel: 01202 665724 and he'll give you chapter and verse on the most economic and quality product. He'll cut it in whatever size you want. (no commercial interest - just satisfied customer)
The biggest safeguard when cutting small sections is avoidance of tearing the facing veneer and/or splitting the ply layers. Sandwiching and clamping between sacrificial sheets is one way of reducing this danger (and using sharp tools). When having this need myself I've marked the sheets up and got a local cabinet maker to router them out. Excellent results.

 

[Johnjo]

Running a stanley knife along the line before sawing helps to prevent the splintering.

 

[VicS]

[ QUOTE ]
Running a stanley knife along the line before sawing helps to prevent the splintering

[/ QUOTE ] Anyone serious about woodwork should have a proper marking knife and always use it when cutting across the grain!

 

[Poignard]

[ QUOTE ]
......router them out. Excellent results.


[/ QUOTE ]

Yes, I'll second that. I used a router last time I had to cut up some plywood, it was quick, easy and gave a very clean cut.

 

[earlybird]

The glues used in marine ply and exterior ply should be similar, a resorcinol WBP type. The marine spec. ( BSS ?1088 ) calls for decent quality, hardwood veneers throughout, and no voids. The standard for exterior grade ply is not so demanding.

 

[oldharry]

<<what's the difference between marine ply and high grade ply?>>

Marine ply should have internal veneers cut from the same timber to the same thickness as the external veneers, and in the best grades is a recognised usually red hardwood.

WBP plys from the builders merchants are usually glued with the same grade of glue as Marine Ply, but often the only hardwood is the external veneers which are much thinner than the internal veneers which certainly in the cheaper grades tends to be a softwood. Also it is not uncommon to find a single internal veneer sandwiched between two much thinner decorative harder exteriors.

Also True marine Ply to BS1088 should not have interior voids beypond a certain width - the voids being joints in the internal veneer sheeting. Builders merchant grade plys often have quite large voids creating significantly weakened areas. Better grades of builders ply may have equal thickness veneers internally, but the grqade of timber used is often poorer than 'decent' marine ply.

Unfortunately the market is flooded with rubbish cheap Far Eastern boards often marked BS1088, but nowhere near the true BS requirement. I believe they avoid the Trade Descriptions act by using it as a 'stock number' or 'catalogue number'.

Get a sample from somewhere like Robbins, and compare it with Builders merchant 'rubbish'. You will soon see the difference!

 

[Lakesailor]

Why are you stuck on marine ply.
How about a plastic sheet material. Perspex, foamex etc?

http://www.plasticsupplier.co.uk/products.php

 

[ChasB]

The problem with plastic is sourcing something suitable. The usual frame stuff, fibre glass imprgnated nylon, turns out to be too brittle because the hull is no longer truly flat (see previous thread ). What else would be suitable?

Thanks for the input guys, particularly Harry, and Ron I'll give Mr. Howells a ring.

Cheers! /forums/images/graemlins/smirk.gif

(thinks: must find out what a router is!)

 

[stuey_two]

A router goes between your modem and network - it "route" signals to multiple oulets and is not very good at trimming ply.
On the other hand, a router is a power tool that drives cutters at very high speed that can produce simple or complex edges to sheets of material - and has never heard of a modem.

 

[ChasB]

A search on google yields several woodworking routers that will run quite happily off a PC. Expensive though. I'm sure they could also be networked via routers, but that may cause confusion with multiple users and I might end up fitting a nicely cut toilet seat on my windows. /forums/images/graemlins/frown.gif

Ah, British humour.


Would using a jigsaw be ok? Is there a special cutting bit?

 

[santeana]

Chas, I wouldn't since I'd be trying to safeguard the condition of the exposed end-grain in what is going to be a testing environment. I'd want to do all I could to ensure a long maintenance free life. If you must saw I'd suggest leaving 2/3 mm stock and sanding to size. Personally, I'd still use a router - you don't have to buy one. Mark out yourself and get them cut by a local skilled woodworker. A few quid well spent and maybe a valuable future contact.

 

[ChasB]

Will do. cheers. /forums/images/graemlins/frown.gif