Removing sodden foam core

[ripvan1]

With a spongy foredeck and fearing disintegrating foam between the two grp skins, I have cut off the outside skin to access the core. This was after reading up on other forums and against some advice on others to drill up from below and squirt foam in holes. (Glad I didn't go this route)

There was a lot of moldy sodden foam there (don't let anyone tell you this stuff is water resistant) but its all out now and cut back to sound and un-deliminated foam.

As it's a relatively small and flat 2ft x 4ft area, my intentions are to put one layer of gsm over the lower skin (from above obviously) put down 9mm sealed ply then building up a few layers of gsm, sand, fill, sand and gelcoat.

As a novice to this grp lark and getting most of my info from reading up on the web and asking about, does the above seem about right or am I missing anything.

Thanks

 

[prv]

I'm not an expert either, but it's pretty much what I did and no ill effects so far.

Pete

 

[neil_s]

I'm no expert on this but have an interest since I have two areas of deck which are going a bit springy. There was an article in PBO I remember that suggested that the old piece of deck top laminate could be put back if you made sure the foam/ply filling was the same thickness as the original. The edges of the old deck were feathered and the join made by laminating layers of GRP into the triangular gap area.

Cheers! Neil

 

[Poignard]

I think I would just follow the techniques described in section 5 of this WEST manual:

http://www.westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

 

[Little Five]

http://www.lackeysailing.com/

Have a look at this web site. Tim Lackey repairs classic GRP boats with full descriptions of each step and photos.

 

[30boat]

If you're not using epoxy resin and fillers(and in my opinion that would get you a better repair)then use a mix of fluffed up csm mixed with resin and catalyzed filler,polyester obviously,to glue the plywood to the substrate.One layer of csm alone won't give a good enough bond and the whole thing will certainly delaminate later.Roughen up the plywood to improve adhesion.I did the decks of my previous boat that way and the result was a strong repair.Given the choice I would go for epoxy because it is a much better glue.

 

[rjcoles]

Don't forget to wash the remaining bottom layer of GRP to remove any salt, in the final wash mix some IPA with the water to degrease as well. I would only use an epoxy as new polyester does not bond very well to old GRP

Don't ask how I know!!

 

[ripvan1]

Thanks all, plenty of reading there and some good tips

 

[john_morris_uk]

Epoxy is very much worth the extra expense, as others have said it sticks much better to the existing GRP and to the plywood panel you are proposing laminating in place.

Are you sure that the deck is truly flat? Decks often have an almost indiscernible camber to help them shed water.

The instructions should also explain how you will need to feather the edges of the top surface of the old deck to allow the new epoxy surface to stick to it with reasonable strength. A small angle grinder is very effective for doing this. Good luck. Why not take some pictures?

 

[nigelmercier]

squirt foam in holes...

AFAIK, you can only get open cell foam in the squirty tins; you need closed cell foam on a boat.

When I had to remove a foam core, I put a bit of bent piano wire in my drill and used it as a flail; it worked well.

 

[PabloPicasso]

what and how did yopu fill the gap after flailing out the old foam/plywood/whatever?

 

[prv]

what and how did yopu fill the gap after flailing out the old foam/plywood/whatever?

My waterlogged core was under the mizzen mast, so it was plywood before and new plywood after.

Pete

 

[PabloPicasso]

so did you open the deck by cutting out a peice?

 

[prv]

so did you open the deck by cutting out a peice?

Yep.

Some people put the old skin back on again; I laid new fibreglass instead as it was a relatively small area and I'd fairly mullered the old bit making bigger and bigger holes chasing the rot.

Pete

 

[ripvan1]

what and how did yopu fill the gap after flailing out the old foam/plywood/whatever?

2x 1.5 oz csm layers onto base

11/12mm ply

2 x 1.5 oz csm layers onto ply

several layers of resin thickened with cabosil

(not shown)

several coats of gelcoat

(not yet done)

deck paint

 

[PabloPicasso]

that looks like a neat job. I'm not sure I'd be confident enough to tackle it though.

 

[prv]

that looks like a neat job. I'm not sure I'd be confident enough to tackle it though.

My deck was only my second ever piece of fibreglass work, after blocking up a small access hole in a vertical panel. It's really not as hard as it seems.

A book I read on cruising remote areas listed one of the benefits of GRP as being repairable with "unskilled labour".

Pete

 

[ripvan1]

That was my first attempt

In fact after 3 other boats this is my first grp boat - reading other forums, picking peoples brains at marina and of course reading this forum, it's a case of taking a deep breath and just going for it.

 

[oldsaltoz]

It's a pity you did not cut from inside, it saves the original deck anf non slip areas.

Wash the area with Acetone before you do any work, and again after sanding if you do any.

I would avoid using ply, the quality of the timber and more importantly the glue used is very poor in ply today unless you pay a fortune for it and then worry about it for the next few years.

Faster, easier and lighter would be the way the go. Use a closed cell foam, you can cut it bend form it and sand it with ease.

Also only use and epoxy resin, stronger and lighter.

If the foam available is too thick, cut or sand to size, if too thin, glue sheets together with epoxy resin and Micro-fibres.

Cover the base with a layer of micro fibres and epoxy resin, drill 6 mm holes in the foam on a 60 mm grid, press the foam onto the mix and any trapped air or excess resin mix will come up through the holes.

Now ready to glass in.

To finish do not use Gelcoat, use flow coat instead, it's the same as gelcoat but has wax added so you don't have to mess it with a plastic covering.

Good luck and fair winds to all.