Different types of Marine Ply

[GuyC]

Whilst the strength is in the GRP, the foam separates the two layers to make the arrangement much more structurally effective. It's a bit like a RSJ where the web i.e. the bit in the middle is just there to seperate out the flanges which are the parts that provide the strength.

Whilst it is structurally efficient, you still have to make the surface that you stand on sufficiently robust that you don't damage it from standing on it. I suspect that is why they use ply as the filler rather than foam until you get much bigger and then the lay up is sufficiently thick to support local loads.

My Pac 22 deck which wasn't glassed lasted 25 years before it needed replacing. I'm a bit on the fence with regards trying to encapsulate the ply. I sometimes think the encapsulation will stop the ply drying out if and when it suffers from a bit of water ingress.

[xpertski]

Originally Posted by GuyC

Whilst the strength is in the GRP, the foam separates the two layers to make the arrangement much more structurally effective. It's a bit like a RSJ where the web i.e. the bit in the middle is just there to seperate out the flanges which are the parts that provide the strength.

Whilst it is structurally efficient, you still have to make the surface that you stand on sufficiently robust that you don't damage it from standing on it. I suspect that is why they use ply as the filler rather than foam until you get much bigger and then the lay up is sufficiently thick to support local loads.

My Pac 22 deck which wasn't glassed lasted 25 years before it needed replacing. I'm a bit on the fence with regards trying to encapsulate the ply. I sometimes think the encapsulation will stop the ply drying out if and when it suffers from a bit of water ingress.

I have thought about that previously, whether not glassing the ply enables it to breathe but then I thought there is very little breathing below deck anyway, which is why condensation can form in there (moisture gets in through air gaps but struggles to get out) ... so perhaps moisture would be trapped anyway...

[jeffstevens763@g]

I think that's where the buffalo board holds its own not looked into the two specs but the glue between the vaneers is different on the edges if the edges area sealed so the whole board is encapsulated without glassing where holes can appear same as with epoxy which pin holes, with 15 year garantee it's going to last 25 years also has a checker plate finish for non slip so a fine grit in the flow coat could be used for neater lines on the edges for aesthetics
If the bilge is allowed to breath condensation shouldn't be a problem it wasn't on my ribquest venting through the anchor locker and stern drain

[beamishken]

Originally Posted by Pikey Dave

Surely if you’re going to glass it in, the grade of board is largely irrelevant. Many manufacturers don’t use ply these days, they use foam. The strength is in the GRP & the substrate is just a form.

Thats my thoughts too, simplest way if your going to use ply is just use wbp & glass both sides
The phenolic ply is great stuff & lasts well on trailer decks but I'd be concerned about the bond between the wood & glass
Glassing both sides of wbp probably costs no more than using marine ply & has to be a better job imho

[xpertski]

Originally Posted by beamishken

Thats my thoughts too, simplest way if your going to use ply is just use wbp & glass both sides
The phenolic ply is great stuff & lasts well on trailer decks but I'd be concerned about the bond between the wood & glass
Glassing both sides of wbp probably costs no more than using marine ply & has to be a better job imho

Out of interest why is using WBP better than using marine ply? Wouldn’t glassing both sides of marine ply be better than glassing both sides of WBP?

[Steve509926]

Originally Posted by xpertski

Out of interest why is using WBP better than using marine ply? Wouldn’t glassing both sides of marine ply be better than glassing both sides of WBP?

No it's not better, but you're still confusing the term WBP.
WBP is in reference to the adhesive used, it is an acronym for "weather and boiling point" of the adhesive.
Marine ply is made with the same adhesive as good quality external ply.
The difference is that marine ply has less voids in it than external ply.
I presume you are asking "Wouldn’t glassing both sides of marine ply be better than glassing both sides of good quality external ply?" - No it wouldn't, it would just be more expensive.

[jeffstevens763@g]

Have a good look at the xs ribs build vid OMO but the support ply doesn't look top grade plus they glass both sides of the deck but every thing is encapsulated in glass, happy to be shot down if you disagree

[beamishken]

Originally Posted by xpertski

Out of interest why is using WBP better than using marine ply? Wouldn’t glassing both sides of marine ply be better than glassing both sides of WBP?

I meant using fully encapsulated wbp would be better than using marine ply & only coating with epoxy or similar as explained by humber. If your using marine ply & fully encapsulating it then your just wasting money on expensive ply for little benefit imho

[beamishken]

Originally Posted by jeffstevens763@g

Have a good look at the xs ribs build vid OMO but the support ply doesn't look top grade plus they glass both sides of the deck but every thing is encapsulated in glass, happy to be shot down if you disagree

Exactly my point using expensive ply & glassing both sides seems to be a waste of money

[xpertski]

Originally Posted by Steve509926

No it's not better, but you're still confusing the term WBP.
WBP is in reference to the adhesive used, it is an acronym for "weather and boiling point" of the adhesive.
Marine ply is made with the same adhesive as good quality external ply.
The difference is that marine ply has less voids in it than external ply.
I presume you are asking "Wouldn’t glassing both sides of marine ply be better than glassing both sides of good quality external ply?" - No it wouldn't, it would just be more expensive.

No I did understand WBP ply as referring to weather boiling point, online seemingly usually referring to exterior ply, so just assumed that, but yes understand the glue is the same as marine ply with the difference being mainly in the quality of the timber (ie without voids etc).

So basically I guess what you are saying is that because of the glassing creating a seal around the timber the presence or absence of voids doesn’t matter? So in that sense there is little/less benefit from a higher grade ply (and impact resistance differential between timber species less important with solid glassing both sides) - I guess only if water penetrated through screwing through a deck where old sealant may degrade (perhaps avoided by Forst sealing drilled hole with epoxy they turning screws into an epoxy filled hole ... I think I read somewhere that polyester resin lets moisture through over time but guess this can be stopped by applying an extra coating, something like flow coat. Speaking to the guys at fibreglass direct they mentioned that polyester resin is just as waterproof as epoxy , though tbh I had heard elsewhere that polyester resin isn’t as waterproof as epoxy ...

[xpertski]

Originally Posted by jeffstevens763@g

Have a good look at the xs ribs build vid OMO but the support ply doesn't look top grade plus they glass both sides of the deck but every thing is encapsulated in glass, happy to be shot down if you disagree

Sounds good, I’ve watched that before but not focussing on the ply ... will watch again [emoji106]

[Steve509926]

Now I have to refer back to #26

[xpertski]

Originally Posted by jeffstevens763@g

Have a good look at the xs ribs build vid OMO but the support ply doesn't look top grade plus they glass both sides of the deck but every thing is encapsulated in glass, happy to be shot down if you disagree

Yes you are right!

See photos ... also out of curiosity anyone know what that fibreglass looking beam is from that they glass to the underside of the floor? Almost thought it might be a channel for cables etc

[Steve509926]

Don't know, but it could be a dual purpose fitting. Firstly to add longitudinal strength/stiffness to the deck and it would make an ideal cable channel. Incidentally that looks very much like Light Red Meranti.

[xpertski]

Originally Posted by Steve509926

Now I have to refer back to #26

[emoji23] I am definitely an over thinker, but then again interesting discussion with some good knowledge being shared so I’m ok with that [emoji23] ..... to quote hot fuz “for the greater good”

[xpertski]

Originally Posted by Steve509926

Don't know, but it could be a dual purpose fitting. Firstly to add longitudinal strength/stiffness to the deck and it would make an ideal cable channel. Incidentally that looks very much like Light Red Meranti.

Did wonder what it might be, looks like there is a gap in one of the layers of that piece as well!

[jeffstevens763@g]

Cable duct I think

[GuyC]

It's funny that they look like they are drilling holes in the bulkhead after it has been installed in the boat. For a production boat, you probably know where the hole is before you cut the bulkhead out of the 8'x4' sheet of ply. As a result it would be better to cut the hole at the same time as the bulkhead. Ditto any holes in the deck for cable entry etc.

[69cmw]

Ask Nugent on here what he uses for decks as he has rebuilt a good few ribs over the years

[jeffstevens763@g]

Originally Posted by GuyC

It's funny that they look like they are drilling holes in the bulkhead after it has been installed in the boat. For a production boat, you probably know where the hole is before you cut the bulkhead out of the 8'x4' sheet of ply. As a result it would be better to cut the hole at the same time as the bulkhead. Ditto any holes in the deck for cable entry etc.

In my expeariance it's easer to glass solid wood than to glass around a hole not an expert but just easer for me