Keel Fairing - Filling Cracks

[Little Rascal]

I've just noticed a couple of little cracks at the fore and aft end of the top of my Europa's keel. As far as I recall from the last time I stripped the keel to the cast iron, they would be in the compound fairing the keel to the hull. The boat hasn't been grounded and the keel bolts look bombproof but she has seen some wavy weather on a few trips.

Can anyone suggest how to seal the cracks, more to prevent corrosion than anything? Some kind of flexible submersible compound?

Thanks.

 

[Concerto]

Personally I would use a Dremel to open the cracks up to see how extensive the cracks are. If they are in the fairing compound then the crack should show as a dark line whilst using the Dremel with a small abrasive point. If it is just in the fairing compound, then I would just fill with 2 part waterproof epoxy filler. Then antifoul as normal.

If the cracks reappear at a later date, then you are experiencing some hull flexing due to movement of the keel. This would suggest the fibreglass should be strengthened. This is the time to get a surveyor to give advice on what, if anything, you need to do.

 

[Little Rascal]

Ok thanks, I will try that.

Would something like International Watertite be suitable? Or is there anything cheaper (in smaller quantities) since its a tiny area?

 

[Concerto]

Any of the 2 part car body filler type fillers will do the job. You do not need to use expensive marine fillers for this.

 

[Little Rascal]

Ok thanks, good to know

 

[MagicalArmchair]

Car body filler? Really? I thought it could shrink and pop out? Epoxy thickened with Colloidal silica I would have thought...?

 

[Concerto]

He wanted something cheaper. I first came across car body filler being used by Camper and Nicholsons. They used it to fair in the flanged keel on my father's new Nich 30 in the early 1970's. Ours was sailed very hard and it never moved or cracked.

 

[KAM]

Sounds quite normal to me and nothing to worry about. You need to use something flexible like sikaflex. Not much point in using epoxy. Have a look at other boats in the yard and you will see what I mean.

 

[[448]]

Here's what I have used successfully for 40 years for similar jobs under water. It's a one part polysulphide and can be painted. It does take a day or two to go off. I always had a tube on the boat.

Arbokol 1000.

http://www.dortechdirect.co.uk/window-installer-tools/Arbo-Kol-1000.html

Sticks like shit to blanket and remains flexible.

 

[Skylark]

e-bay item 290915083617. JB Marine Weld. Cost £7.70p

Tried this for the first time recently. Used to fill a small scratch on the rudder. It was easy to apply.

 

[Greenheart]

Not sure if my small problem requires a similar solution, but the answers so far encourage me to ask.

I reckon my boat was flooded at some point when it was on its trailer, and the weight pressed the narrow trailer-supports through the bottom of the hull...

...this was repaired in a fairly workmanlike way, although many years later (I've no idea how long ago it was) the filler is visibly distinct from the original GRP, and there are tiny cracks in the filler.

If I had used the boat much lately, I wouldn't be surprised if she'd absorbed some water, but she hasn't been afloat since October. Yet today when I looked at the undersides, these old, tiny cracks showed a rusty-brown powder has accumulated along the length of the cracks...

...which seems to me to show that some liquid has been retained for a long time inside the moulding, and that it has lately escaped through those old cracks.

Looking at those photos now, the cracks look pretty scary. So I'm keen to seal them permanently, even if that means trapping some residual liquid inside.

Given that the cracks are probably the consequence of shrinkage in the filler used, what's the most suitable product I can use to fill the cracks and prevent their recurrence?

The boat is an early-seventies GRP Osprey dinghy.

 

[MagicalArmchair]

This is a cracking reference for GRP repair:

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

Epoxys bonding characteristics to old Polyester resin are astonishing - the rest of the boat will fall apart around any repair with West System before the repair fails . Its not cheap, however, its a fix once and forget product.

 

[Concerto]

Dan

I would start by cleaning off all the crud so you can see exactly how bad and extensive the cracks are. I expect they travel through the gel coat to the glassfibre and these areas will probably need reinforcing internally. It should not cost a fortune if you use a West repair kit, but it does depend on how extensive the damaged area is. I have used cfsnet.co.uk for my supplies as they are cheaper than a chandlery. I presume the hull is white. Once the reinforcing has been completed you can open the cracks with a Dremmel type tool and then fill with Gelcoat Filler made by Plastic Padding (about £12). Smooth off and polish with the rest of the hull.

 

[Greenheart]

Thank you gentlemen, it's a great relief that you're not despondent about the prospects of making a good repair.

I reckon you could charge, for such reassuring advice. :encouragement:

 

[Concerto]

Did I hear "The cheque is in the post"?

You are welcome. How else would you learn how to tackle what appears to be a difficult job without advice. It is better to ask before starting than doing something that makes it an even more difficult job. This way you will save time and money.

 

[Greenheart]

...better to ask before starting than doing something that makes it an even more difficult job. This way you will save time and money.

With that excellent principle in mind, I must ask whether I should buy a cordless Dremel...or some less costly substitute. I'm not reluctant to pay up for a good tool which I don't doubt will give many years of convenient and varied use - but if the grinding-out of old GRP cracks might easily be achieved by a chisel or craft knife, I must consider the cost.

My boat is nowhere near a 240v supply...so a cordless Dremel is what I'm thinking of. They look like nice tools - compact and versatile - but is one model better than another?

 

[Concerto]

Dan

Dremel's are the market leader. I have one but you could buy one a similar type one. This looks a fairly good one http://www.ebuyer.com/438986-xenta-...gn_email&utm_campaign=B2C_(Friday)_Openers_FS.

That one or a Dremel will require a mains supply. The battery operated ones will a lot heavier or have only limited power or battery life. Your best bet would be to move your dinghy closer to a mains supply to do all your work.

 

[TQA]

I would not use regular P38 car body filler under water. It is hydroscopic, you will get blisters.

P40 is better.

But better still is some flexible sealant like 3M 4200 or even 5200.

 

[Greenheart]

Concerto, my belated thanks for your reply last weekend. :encouragement:

Unfortunately 240v power isn't an option for my work on the boat where she is, and nor can I foresee moving her nearer a socket. I may or mayn't pick up a cordless Dremel, but after reading the West Systems PDF, I reckon I can 'feather' the scratches on my hull with a decent craft knife, ready for epoxy repair.

One thing I don't know, is whether the same kind of micro-fibres or filler-granules are usable with polyester resin or epoxy...somewhere, I think I have plenty of the polyester variety left over from work last season, so if it is equally suitable for epoxy repairs, I needn't buy more. Any views?

 

[Concerto]

Dan

You would be wise to ask a glassfire supply company about the micro-fibres or filler granules and polyester. I do know that you need a partcular type of fibreglass mat with epoxy. I have found www.cfsnet.co.uk to be very helpfulon technical questions.