Repairing a hole in a GRP deck

[flipper]

I've recently removed the foredeck vent on my new to me boat as it was leaking. The deck is sandwich construction and the core around the hole is soaking wet. The hole is 4" diameter and as yet I'm not sure how much I'm going to have to cut it back to get to sound material. So my question is, how do I go about making a repair in say, a 6" hole in the deck? Is it a case of making a snug fitting piece of similar thickness ply (wedged I suppose) and then building up from each side with CSM and epoxy resin and applying gel coat filler to the deck side, or have I missed something?

I'm not replacing the vent as I plan to fit a new hatch in the forecabin with a built in vent.

Any ideas welcome. The boat is a mid 70's Itchen Ferry 25

Thanks, Patrick

 

[gjgm]

I've recently removed the foredeck vent on my new to me boat as it was leaking. The deck is sandwich construction and the core around the hole is soaking wet. The hole is 4" diameter and as yet I'm not sure how much I'm going to have to cut it back to get to sound material. So my question is, how do I go about making a repair in say, a 6" hole in the deck? Is it a case of making a snug fitting piece of similar thickness ply (wedged I suppose) and then building up from each side with CSM and epoxy resin and applying gel coat filler to the deck side, or have I missed something?

I'm not replacing the vent as I plan to fit a new hatch in the forecabin with a built in vent.

Any ideas welcome. The boat is a mid 70's Itchen Ferry 25

Thanks, Patrick

West System Epoxy have booklets on various jobs, for about £6.
I suggest you spend the £6 on the booklet as it think it tells you what to do with the core, how wide to scarfe the grp etc etc. You may get a bit of phone line advice if you arent then sure while you are asking them quite which fibreglass matting to use ;

 

[narcer]

Epoxy

That will work fine, however maybe consider the following also :

When you´ve cut back and found dry stable material to epoxy into I would definitely seal the foam core with pure epoxy resin at this stage just as an extra barrier.

Also when you start to laminate remember to "scarf" in the epoxy repair to the existing fibreglass deck lamination eg at least 5:1 is recommendable. Just cut it back to a nice angle with a p 16 on a flex on the topside and the bottom side.

Wet out your pieces seperately first on a wet board and then you go much quicker and it´s better for controlling the wetting out process.

Do it all in one hit - it´s a better job.

Good luck

 

[status]

What is the core?

My decks are balsa, the sight of rotting balsa fills me with dread, but....

I had a similar problem with a deck vent, once removed I raked out the wet and soft balsa from around the hole with a chisel then sealed the outside with plastic/ductape and left a couple of weeks to dry out. I then re-filled the gap in the core with resin/microballoon filler. This saved the need to make the hole any bigger.

I re-installed the vent, but if I was filling it in, for a 4" hole I would not be too worried about the wooden plug (4" dia of filler is not going weigh the boat down) or the CSM (to gain a meaningfull strength requires the inside and outside laminate being ground back to give a tapered overlap). Cover the bottom of the hole with polythene and ductape then fill from above with a polyester resin based filler, possibly with glass strands in. Fill in layers (2 or 3) allowing one layer to gel (not go hard) before adding the next to reduce the risk of the resin going thermal (overheating with a runaway reaction). Finish 3mm below the deck level and finish with a coloured flow coat.

Hope this causes even more confusion!

Stuart

Edit: I have suggested polyester resin as Epoxy is not so good in UV light, hence the need for a flow coat on the deck, if the deck side is painted Epoxy is fine. I know sticking polyester onto epoxy can sometimes be funny and would not like to recomend it. (i.e. flowcoat onto epoxy filler)

 

[flipper]

Thanks for the responses so far guys - looks like we are getting towards a solution. I think the core is balsa and I've got the hole covered up to let it dry out for a couple of weeks.

That was a great suggestion re Wests - they have a number of articles to download for free:

http://www.westsystem.com/ss/fiberglass-deck-repair-part-1-replacing-damaged-balsa-core/

Cheers, patrick

 

[mitiempo]

If the balsa is wet it will not dry out and will have to be removed back to dry core. Any scarf should be 12 to 1. Epoxy is the only way to guarantee a good bond with the original polyester. Here's a link to the entire West fiberglass repair manual which is downloadable - link at top.
http://westsystem.com/ss/fiberglass-boat-repair-and-restoration/

 

[Old Troll]

Old Troll

As always the advice given in the forum is good value. There is a book available from Adlard Coles Nautical called " Hull and Deck Repair " by Don Casey at a cost of £14.99p which covers many types of GRP repairs, materials and types of resin etc I have found this book to have been very useful when I first started doing my own GRP repairs.

 

[William_H]

Deck repair

I think you will find polyester resin OK for this repair. As said you need to rake out as much of the rotten balsa as possible and fill the gap with resin possibly with microballoons or even talc filler.
You will need to put polythene over the hole from underneath which must be supported in some way to amke a flat surface level with the inside surface. Before you do that grind away the outside edge of the inside surface so that you can fit a patch of cloth over the hole (a few layers) but let into the surface so that it is all level on completion.
I would suggest you buy woven cloth as this will naturally lay smoother and flatter and is stronger than CSM.
Again grind a chamfer on the outside edge of the top layer so that glass cloth can be laid in in successively smaller sizes to fill the hole to,level. Of course you fill the majority of the hole with circles of cloth just the right size. Once the resin is hard enough you lay the inside layers to complete the job.
Do this underside as soon as resin is firm enough as this then gives a chemical bond of top to bottom layers. The whole repair is like a yo yo larger on the outside on both sides than the inside so locked in place. This is the way to fix holes in hull but not nearly so critical in the deck.
When the resin is really hard you can sand it flat and use filler to get it level and smooth both sides.

You will end up with a smooth surface on the deck which may contrast with the probably non skid molded surface. This is no problem if you are going to paint the deck with non skid but can be a real problem otherwise. There was an article on this forum recently about molding in non skid but i think it would be very fiddly. good luck olewill

 

[Ubergeekian]

What about a 5" diameter flush and non-opening porthole?

 

[nigelm]

I've recently removed the foredeck vent on my new to me boat as it was leaking. The deck is sandwich construction and the core around the hole is soaking wet. The hole is 4" diameter and as yet I'm not sure how much I'm going to have to cut it back to get to sound material. So my question is, how do I go about making a repair in say, a 6" hole in the deck? Is it a case of making a snug fitting piece of similar thickness ply (wedged I suppose) and then building up from each side with CSM and epoxy resin and applying gel coat filler to the deck side, or have I missed something?

I'm not replacing the vent as I plan to fit a new hatch in the forecabin with a built in vent.

Any ideas welcome. The boat is a mid 70's Itchen Ferry 25

Thanks, Patrick

i have just been through a similar thing with my countess , its not as bad as you first imagine , PM sent .

 

[flipper]

I think I need to see how much rot there is. It's too cold now for doing any serious GRP work. I'll dig out all the wet wood - If it's not too bad I think I'll follow the resin/microballoon recommendation, fill it and replace the vent with one of these for £22 which will solve the problem.

The key thing was when the original vent was fitted the edges of the hole were not sealed so it was asking for trouble.

If I have to go down the open deck surgery route, a la nigelm, that's a different story. Our boats are next to each other in the yard at the mo so that's something. Here's a pic of the foredeck. Acknowledgment to boatshed for the pic. It is my boats deck from when she was for sale sometime ago. Offending deck vent centre left.

Next job is the mast step as that's got a leak through the deck too...


Cheers, Patrick