Adhesive for GRP

[Kalico]

Anyone know if gap filling adhesives such as Gripfill and Pink Grip can be used on fibreglass?

If not, what can be?

Thanks Rob

[Steve Firth]

The usual gap filling ahdesive used on GRP is epoxy filled with glass microballoons.

[Grunff]

Most GRP is styrene, not epoxy. If you are filling styrene based GRP, you really need to use styrene based filler - otherwise adhesion isn't great.

The majority of car body fillers are styrene based, and so work well on GRP.

[Peter Parry]

Polyester resin - car body filler, you need to abrade the existing fibreglass surface first and if you use a coating of polyester resin & hardener and allow it to semi harden before filling with polyester filler you will achieve stronger results.

[Steve Firth]

Polyster.

No, that's not true. Polyester resin doesn't adhere as well as epoxy to cured polyester. Epoxy will always provide a good bond, *provided* that you clean away the moul release agents from the surface. Roughen and swab with acetone before attempting a repair.

What you must not do with epoxy is to use it with CSM. The binder that is included in CSM is only soluble in the styrene used with polyester resin, epoxy can only be used with a woven glass tape.

[Grunff]

Nit picking - styrene monomer which polymerises to polyester. Plenty of free styrene left over.

Hmm, gotta say that has not been my experience, but I've only dabbled, so I'm prepared to take your word for it.

[Kalico]

Yikes! Lots of very technical answers.

I am less concerned with the strength of bond, since it is not for anything critical.

More that I would hate to apply something which would then dissolve a hole into the bottom of my boat!

Thanks for all advice - I really appreciate it. Hell, there is certainly some good knowledge on this group.

Rob

[The Natural Philosopher]

Oh - Boat? Normal prtactice would be to file degrease and roughen as described elsewhere, and then use glass cloth with probably polyester rather than epoxy to fill any structurally weak areas, and epoxy and microballoons or indeed car body filler to get everything nice and smooth.

[Steve Firth]

It's a fairly common repair in situations where strength is required (boat building). In general epoxy to polyester gives the strongest repair, polyester to polyester can work but it's not the best combination. Polyester to epoxy won't work at all.

A common technique in boat building to support something heavy is to epoxy a stainless pad with a stainless threaded stud to the polyester hull, then to put woven tape/epoxy over the pad to ensure it won't move.

[Pete C]

Hi,

Have a look at:

Epoxy gives a much better bond than polyester BTW.

cheers, Pete.

[:::Jerry::::]

Little confused here, the OP was asking about 'gap filling' not bonding, the original reply from 'Grunff' that suggested Auto body filler would be OK is correct / if / it is gap filling that is required, but if the OP wants to bond then Epoxy should be used.

[Kalico]

All I need to do is glue a wooden block to the inside of the hull.

Attached to the block will be a metal eye to tie a bungee cord to that will be tied at the other end to a locker lid. Just to stop it falling overboard really so does not need to be that strong.

The block has previously been glued to the hull by someone else but has come off.

My first reaction was to bang some Gripfill in there as it is cheap and would accommodate the slightly concave hull shape to the flat block. I just didn't want to damage the hull.

Also, do you know if Gripfill (or similar) will bond to stainless steel?

Thanks for all your advice. Rob

[Pete C]

Hi,

Try asking the makers of Gripfill whether it will do, I wouldn't mind hearing what they say. Whatever you use you'd need to grind off any paint or left over glue back to bare fibreglass to get a good key.

To make epoxy gap filling just thicken it with something, see archives of rec.boats.building for some ideas. Will this be indoors out of the weather or not?

cheers, Pete.

[Kalico]

Well, it may catch the odd bit of water but otherwise will not be getting wet too much.

I shall ask Evode.

Replace 'spam' with 'org' to reply

[:::Jerry::::]

Is there any reason why you can't laminate this mount onto the hull, in other words, use GRP mesh and resin in the same way as the boat will have been built IYSWIM ? It wont be as quick as using a bonding glue but it will be stronger if done correctly.

[Kalico]

The only reason that Gripfil sprung to mind is that I have used it extensively before with excellent results whereas I have absolutely no experience with glassfibre.

Rob

Replace 'spam' with 'org' to reply

[Pete C]

Hi,

Had a quick search and found a list of materials and a data sheet on the makers web site:

Would probably work OK, but if you can paint or coat the wood and the area round it sometime that would be better.

cheers, Pete.

[Kalico]

That's excellent - thanks very much Pete.

Rob

Replace 'spam' with 'org' to reply