Repairing a hole in GRP question.

[moresparks]

Hi – I have removed some cockpit panels to send them away for recovering which has allowed access to my stern cleats. However I noticed that the cleat bolts were pretty well corroded and the ply backing panel wet and coming away from the fibreglass. So I decided to remove the cleats.
Now the funny thing was, that the cleat was mounted on a stainless steel sheet, self tapped screws into the fibreglass, so I removed the stainless sheet.
I have now discovered to my horror a mess and which can only describe a botched repair as it looks like at some stage the cleat has been torn out and “repaired”. The “repair” has several cracks in it with several gelcoat star cracks.
I have only limited access to behind the cleat via an access hole and the ply backing panel is still stuck fast in places.
I am thinking of completely removing the botched repair which will probably leave a large hole and allow the removal of the ply.
I am thinking of starting the repair with a thin G 10 sheet as a backing before building up layers with fibreglass and resin finishing off with gelcoat and a new backing pad. Does this sound like a good way forward as the area is reasonably flat?
I have used fibreglass before and still have the tools and various handbooks when I bonded in some engine bearers on a previous boat but not repaired a hole before.
I welcome suggestions.

 

[VicS]

Hi – I have removed some cockpit panels to send them away for recovering which has allowed access to my stern cleats. However I noticed that the cleat bolts were pretty well corroded and the ply backing panel wet and coming away from the fibreglass. So I decided to remove the cleats.
Now the funny thing was, that the cleat was mounted on a stainless steel sheet, self tapped screws into the fibreglass, so I removed the stainless sheet.
I have now discovered to my horror a mess and which can only describe a botched repair as it looks like at some stage the cleat has been torn out and “repaired”. The “repair” has several cracks in it with several gelcoat star cracks.
I have only limited access to behind the cleat via an access hole and the ply backing panel is still stuck fast in places.
I am thinking of completely removing the botched repair which will probably leave a large hole and allow the removal of the ply.
I am thinking of starting the repair with a thin G 10 sheet as a backing before building up layers with fibreglass and resin finishing off with gelcoat and a new backing pad. Does this sound like a good way forward as the area is reasonably flat?
I have used fibreglass before and still have the tools and various handbooks when I bonded in some engine bearers on a previous boat but not repaired a hole before.
I welcome suggestions.

The West System website and their instruction manuals will tell you, in detail, all you need to know ( and more) including repairing holes with no rear access.

https://www.westsystem.com/

 

[lw395]

The west website will tell you to use west products.
No real reason not to use polyester.
Starting with a backing sheet to bridge the hole is sound thinking, but the key thing is to lay up a good overlap between new and old GRP.
If you have good access from both sides, a temporary backer (covered in polythene to act as a release agent) will let you bridge the hole, then you can reinforce from both sides.
If you lay up some mat or cloth on the backing piece, then press it into place, that should be a good start.
The key (sorry, pun) is to abrade everything you need resin to stick to.

 

[TQA]

Polyester resin does not stick very well to cured polyester resin IE you boat.

Epoxy does 'stick' better.

If you are buying the resin then the old adage about a 1/2p and tar applies. If you already have polyester resin then, as it will not cause the boat to sink if the bond fails, go ahead and use it.

 

[lw395]

Polyester resin does not stick very well to cured polyester resin IE you boat.

Epoxy does 'stick' better.

If you are buying the resin then the old adage about a 1/2p and tar applies. If you already have polyester resin then, as it will not cause the boat to sink if the bond fails, go ahead and use it.

If you can't make polyester resin stick to cured polyester resin, maybe leave the job well alone and get a tradesman to do it.

 

[William_H]

Not sure exactly what the hole size is or just how much access you can get behind. But firstly any cutting out of GRP is going to ruin the outside surface condition. If this is smooth then not such a problem as non skid. So you may want to be reluctant to cut the outer skin. Underneath you can add lots of back up and it is not seen.
Now if access is difficult to underneath you can try pulling up a piece of stainless steel or ply or previously set GRP with strings or wire to hold it in place. You can try bonding nuts to the underside of the holes in the backing. Or tapping holes in the metal once it is bonded in place. You could also try pulling bolts up through the holes and put a nut on top. Not so neat but can be effective when poor access behind.
I would use epoxy for bonding and as said abrade the inside surface for better bonding but if this is not possible then just go for large area and lots of epoxy. (with some filler) But having said that polyester will stick especially if pull of bolts holds it together.
Stern cleats can come under huge loads at times when used to moor at a jetty or similar so make it strong.
I had a similar problem on my little boat in that i became doubtful about the strength of the flat transom where the transom mounted rudder hung. Access inside was very difficult and not flat with reinforcing GRP covered tube up the middle. I layed up a big square of carbon fibre on the outside. (epoxy) Thus spreading load and making holes more robust. I have previously painted the hull with 2 pack so not difficult to paint the cf and under the gudgeons (or is that pintles) it does not look too bad. I feel more confident. good luck olewill

 

[moresparks]

As an update to this and rather start a new thread..
Now the warm weather has arrived I am starting the repair using West Systems Epoxy and the handbook. The original repair was truly shocking and it looks like some brown/ grey filler was used and the structural integrity was debatable at least, hence the stainless steel sheet covering the repair. The hull in this case is smooth white but its 30 years old so trying to match the finish would be difficult. Having removed the old filler I am left with a hole around 150mm so quite large. I have bonded in an epoxy backing sheet and now building up the layers with woven frabic and will finish off as per the handbook before gel coating.
Now the question .. the finished repair will be quite large, after all the hairline cracks have been repaired at least the size of an A4 sheet, so i was thinking if the gel-coat cannot be a matched I could use a vinyl wrap before fitting the cleats (on both sides). Any thoughts... I do have wide navy stripes leading up to the area so I could use a matching navy wrap to line up. Just an idea at this time.

 

[Stemar]

You'll be wrapping lines round the cleat and those lines will rub on the GRP around the cleat. How long do you think the wrap will last? I'd be tempted to put a teak or similar plate to cover all the grotty stuff and mount the cleat on top.

 

[moresparks]

Hmmm.... Excellent point - thank you. In my desire to complete a neat as job as possible I forgot about the practicalities. I will persevere in trying to match up the gel coat first before fitting the cleat.