Fastening Marine ply to fibreglass

[tronic72]

Hi All,

I need to mount some marine ply in the bilge of my 31 foot cabin cruiser. What is the best method of fastening these pieces to the hull. Previously they were simply screwed to the glassed stringers but many of these have been filled to stop water penetrating.

I have painted the ply and test fitted and the glass is so hard I don't expect the paint will last long. I'm thinking of using some sort of rubber or nylon spacers between these two dissimilar materials.

Thanks in advance. Any photos would be great.

[Pete7]

If its going to be permanent then I would sand off the paint from the plywood and use epoxy resin fillets between the plywood and GRP.

West systems is the well known brand but there are others. West system have some user guides if you are not sure, but its not difficult to do.

http://www.westsystem.com/ss/use-guides/

Pete

[tronic72]

Originally Posted by Pete7

If its going to be permanent then I would sand off the paint from the plywood and use epoxy resin fillets between the plywood and GRP.

West systems is the well known brand but there are others. West system have some user guides if you are not sure, but its not difficult to do.

http://www.westsystem.com/ss/use-guides/

Pete

Hi Pete,

I can't do as you said because the bracing in the boat is bullnosed but you gave me an idea to glue blocks of marine ply pieces to the side of the glass bracing with epoxy and then screw into them. These marine ply plates support my fuel and fresh water thanks.

[Pete7]

In that case, you could also over glass them with epoxy and a suitable glass cloth for use with epoxy, especially given the weight they may have to support in a bad seaway.

Pete

[Cadence]

Originally Posted by tronic72

Hi All,

I need to mount some marine ply in the bilge of my 31 foot cabin cruiser. What is the best method of fastening these pieces to the hull. Previously they were simply screwed to the glassed stringers but many of these have been filled to stop water penetrating.

I have painted the ply and test fitted and the glass is so hard I don't expect the paint will last long. I'm thinking of using some sort of rubber or nylon spacers between these two dissimilar materials.

Thanks in advance. Any photos would be great.

Some photos of your job in progress would be helpful on this end.
I might have you adding plywood to the flying bridge.
Kidding aside a photo might help with contributions on the thread.

[dbaublis]

Weld Mount. A variety of fasteners, including studs, tubing clamps and cable tie points, and adhesives specifically for mounting to fiberglass. I use the large cable ties for both cable and pex supports. As strong and permanent as you need it to be.

Weld Mount - Adhesive Fastening System

[captlloyd]

Yes, more information needed to give you a proper reply. Picture or drawing would help. Keep in mind that screws do not work well at all when screwing into the edge of plywood.

[GALAWA]

Plywood bulkheads can be attached to fiberglass hulls quite effectively.
Sand the plywood and hull free of any varnish, paint, or old gelcoat where they will be glassed over.
On the rough plywood , paint a first coat of 50% aceton, 50% polyester resin
Thereafter, simply apply glass fiber and polyester resin.

[smj]

Much better adhesion using epoxy on plywood not polyester.

[DeepFrz]

You need to study this a bit. You will get all sorts of replies here. Some good, some bad and some horribly awful. Without pictures of what you are trying to do everyone is guessing.

[Cadence]

Originally Posted by smj

Much better adhesion using epoxy on plywood not polyester.

Saturating ply with 50/50 acetone and poly works well epoxy may be easier. I didn't get the part of gel coating. I would not want to bond onto gel coat. I may have read it wrong?

[tronic72]

Ok here's some photos.

The photo of the rudder shaft shows where the fuel tank will sit on the ply to the right of the shaft...



The other photo shows the mounting bolts for the p-bracket which is also where the same piece of timber will sit. The timber used to just be screwed into those stringers.



There is also a walk rail that runs down the centre of the boat between the two engines which is have remanufactured. This was also screwed in originally. Here's where it's installed ....



Finally there is another piece of ply which supports the waste and fresh water tanks. This was also screwed directly into the the stringers.



And here's where it needs to go.

[icemate]

Originally Posted by Pete7

If its going to be permanent then I would sand off the paint from the plywood and use epoxy resin fillets between the plywood and GRP.

West systems is the well known brand but there are others. West system have some user guides if you are not sure, but its not difficult to do.

WEST SYSTEM | Use Guides

Pete

Pete, you got this one right. West System was my choice for 10 years that I owned my boat and it never failed. From Barrier coat to clear epoxy, it never let me down.