WBP PLYWOOD

The big difference between wpb and marine ply is that most wpb's are coreboard, consisting one or two thick layers of softwood, coated with much thinner harder veneers. They also have quite large voids bridged only by the outer veneers making them totally unsuitable for structural use. Being softwood the internal veneers rot very quickly if exposed to long term damp.

In dry non structural marine situations, such as furniture wpb is OK, but I would never trust it for loaded or stressed components
 
Thanks everyone again for your advice.
I must admit I am inclined to go along with the, (for wbp guys) as, firstly I will be gluing two peices together to give me aprox 36mm thickness, these will then be cut to shape and then prepared with epoxy as described above, when they are fitted they will be completly glassed in and sealed completly, with many layers of epoxied glass.
Since I posted my original message last night, I have been making new wash boards today from some leftover wbp that I have from my last job, which was bought from B&Q, and I must admit it seemed to be very good quality, no filler etc, and as I am fitting a small round porthole window in the top washboard I made a doughnut bessle from this wbp and never found one void in it when cut and sanded.
In fact it had thirteen layers which should look good at the rounded edges when varnished, maybe I will stick in a pic when their finnished.
BTW what is the best glue for the ply?
Thanks all, Cheers, Eamonn.
 
Polyester may not surface bond to wood very well .... but thin PE will soak in and provide good key.
The trick apart from using a thin PE and one with slow setting time .... is to sand the ply to roughen up and remove any surface agents from when ply was pressed and formed.

An old trick to get really good lock was to drill or gouge small holes / divots for resin / matt to mould into.

Epoxy is better, but generally epoxy unless it's a laminating epoxy such as Wests etc. is too thick in use.
 
Re: WBP PLYWOOD .... thick coreboard ?

Depends on grade and spec you buy .....

All Marine and WBP I have used on boats / models etc. have basically been same in terms of layers, veneers etc. In fact only difference I found when selecting was top surface colour of veneer.

Coreboard in thick sections ... sounds like packing case ply.
 
Epoxy resins for boatbuilding (kit boats like Fyne Boats, etc) seem to ve very runny. I have had to made dams from Plumbers Mate to stop them flowing away. You can of course thicken them, but that defeats the object of getting them to soak in.
 
Epoxy ...

Never said there wasn't "runny" epoxy ...

I was just highlighting to make sure that those who haven't used such material know to make sure they get Wests or as you highlight Fynes etc.
The thinning with Meths is valid ... but I also know from model building days when we we often used that trick for wing-joints ... it weakens the epoxy - I suspect it interferes with the chains produced when it cures. In a lot of cases we found the epoxy a) changed colour to red or blue depending on meths used, b) became more brittle in low volume mixes, or rubbery in extreme.
I much prefer a proper Boatbuilding Epoxy resin such as Wests etc. where designed to flow.

Further on bonding to wood. A friend of mine restored a Dunkirk Little Ship by replacing as much rotten timber as possible and then applying a "tissue-matt" + West Epoxy resin outer skin. It was a beaut of a job ... being thin and tissue matt - it didn't hide the wood etc.
Unfortunately local hoods who decided to have a bit of fun one night set on fire a few boats in the yard ... one being alongside the DLS.
The boat was scarred and blackened by the fire - luckily didn't catch itself ... Fire Brigade arrived pretty quick.
I had to do a second inspection of the boat ... (first was the restoration for Insurance). This second for the claim for damages etc.
The Epoxy matt skin had protected the boat remarkably ... but had lifted. This actually was a saving grace of the hull .. as the skin could be peeled off in large sections where blackened. We were able to peel back to and then cut .. chamfer at good bond edges ... Some days later after re-skinning and fairing up - boat was back to A1 ....
It goes to show that the resin in fact even though penetrated the wood ... actually lifted away after the heat it suffered.

Just thought I'd pass it on ...

Oh and the Yobs ? Large fines only and Probation..... Me ? I would have locked em up ... as they were well known Bully Boys and sadistic .....
 
Re: Epoxy ...

Yes, I've wondered about the advice to thin with meths. The resins are very particular about the correct proportions as it is.

You can strip most of an epoxy coating with a heat gun and scraper. Bloody hard work though. Setting fire seems a bit OTT!
 
Good point by Oldsaloz. I have found the same effect when gluing rubber with super glue. Push the two parts hard together and there is not eneough glue in the joint. The bond fails.

Philip
 
Balcotan also works extremely well and is more tolerant of higher moisture contents than epoxy, being a one part moisture cured glue. Cheaper than epoxy, it is fine for general gluing jobs where the higher strength of epoxy is not needed. Like epoxy, the wood breaks before the glue join gives way.
 
When you say that the WBP is 13 ply is it the very light coloured finish. If so it is Beech ply and will need to be VERY well sealed as any moisture will cause it to expand. Been there, paid the £36 and got some very good ply which I now have to find a use for as It aint going on the boat! I have used the Mahogany WPB from B&Q and found it a very good product, but I do search to find the best stuff. as far as Mr hulley and Bryunzeel ply is concerned It is as been said the dogs wotits but a a VERY high price as last time I got some from him he only sold by the sheet (8*4) and 12 years ago a sheet of 12 mm cost about £100. Gilmour and Aitken at Jamestown sawmill do Mahogany Marine ply at about £40 per sheet (8*4) but again I believe they don't rip it to size for you. This is aI believe a H & S thing!!!!

Derek
Konsort 'Rhumlady'
 
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