Few maintenance questions

[NigelCraig]

Firstly, I don't understand the relationship between painting the hull and gelcoat (above the waterline). As gelcoat is self coloured, is the concept of painting strictly for older boats where years of weathering and "erosion by polishing" means painting is the only option? BTW, I saw a 1970 Nic 32 a couple of weeks back with quite a few little blisters (max 1cm but mostly smaller) in the paint above the bootline - could these just be defects in the top layers of paint?

Other main issue is repairing a teak rubbing strake, of roughly 5cm by 2cm section - it's lost a big splinter at the aft end which runs through one of the screw holes. I have a short section of teak but the section profile is marginally too small to replace the whole end bit with a scarf joint. Could I just replace part of the end section? i.e. with a scarf joint for the vertical join but a butt joint longitudinally - obviously that means a lot more exposed join for water to get into. (you can see my carpentry skills are non existent!) And what sort of glue to use? I envisaged just unscrewing part of the strake and supporting it, enough to get a tenon(?) saw in to cut a piece out. Any idea how long to clamp the join before I can screw it back?

 

[jwilson]

Re the GRP hulls: yes - painting is just a way of smartening up the original GRP surface. Sometimes it is even done from brand new as top-quality paintwork is shinier and harder than gelcoat. Virtually all "superyachts" are painted, for that reason. On more ordinary boats, if you now buy a new blue Beneteau, you get a white one that has been sprayed blue. On old GRP boats almost any shiny paint looks better than ancient gelcoat, and I see nothing wrong with painting old hulls - a decent coat of paint has been an acceptable finish for yachts since the 17th century, though we may not use as much gold leaf as then - see http://en.wikipedia.org/wiki/File:Jacob_van_Strij_-_Het_Jacht_van_de_kamer_Rotterdam.jpg

Blisters just above the waterline are quite common, particularly in the "splash zone" around the boot-top where water from passing wash or small waves constantly wets the hull surface, and dries off again as it gets warm in the sun. Sometimes this is the first area where blisters (often called osmosis) appear - warmed water is worse than cold water for causing blistering. Other times a hull gets an "osmosis treatment" and whilst the bottom is fixed, they do not do the boot-top area, and that goes next.

 

[oldsaltoz]

Firstly, I don't understand the relationship between painting the hull and gelcoat (above the waterline). As gelcoat is self coloured, is the concept of painting strictly for older boats where years of weathering and "erosion by polishing" means painting is the only option? BTW, I saw a 1970 Nic 32 a couple of weeks back with quite a few little blisters (max 1cm but mostly smaller) in the paint above the bootline - could these just be defects in the top layers of paint?

Other main issue is repairing a teak rubbing strake, of roughly 5cm by 2cm section - it's lost a big splinter at the aft end which runs through one of the screw holes. I have a short section of teak but the section profile is marginally too small to replace the whole end bit with a scarf joint. Could I just replace part of the end section? i.e. with a scarf joint for the vertical join but a butt joint longitudinally - obviously that means a lot more exposed join for water to get into. (you can see my carpentry skills are non existent!) And what sort of glue to use? I envisaged just unscrewing part of the strake and supporting it, enough to get a tenon(?) saw in to cut a piece out. Any idea how long to clamp the join before I can screw it back?

G'day Nigel,

Gel coat is not used when fully coating a hull, 'flow coat' is what is used. Flow coat is in face Gel-coat but has wax added so that it need not be covered to cure.

Many boats are re-coated with flow coat rather than paint, it's a lot more work but tends to last longer and the finish on a new coat of flow coat can be made to look spectacular.

Tiny bubbles in the boot topping area are a sign of moisture under the paint in most cases, but can appear under the gel coat, don't let them worry you, in paint they often go away by themselves, in gel coat they can be cleaned up and re-coated.

Good luck and fair winds.

 

[vyv_cox]

I watched a couple re-gelcoat the topsides of a 38 foot boat in Greece. I was surprised that it was relatively easy, although labour intensive. The final finish was excellent, and of course gelcoat is far more robust than paint in resisting the knocks and scrapes that boats are subject to.

 

[morgandlm]

At the risk of trivialising this thread I have to say that I really like the idea of "watching a couple re-gelcoat a boat in Greece". The thought of enjoying that fabulous climate, opening another beer, munching on olives AND watching others work is very appealing! The only better thing would be watching the flotilla arrive in a Greek harbour when the evening wind has got up!
Sorry!
Morgan

 

[pvb]

Many boats are re-coated with flow coat rather than paint, it's a lot more work but tends to last longer and the finish on a new coat of flow coat can be made to look spectacular.

Disagree, decent paint (Awlgrip etc) is harder and more durable than flow coat.

 

[vyv_cox]

At the risk of trivialising this thread I have to say that I really like the idea of "watching a couple re-gelcoat a boat in Greece". The thought of enjoying that fabulous climate, opening another beer, munching on olives AND watching others work is very appealing! The only better thing would be watching the flotilla arrive in a Greek harbour when the evening wind has got up!
Sorry!
Morgan

We were next to them in the yard. While they were gelcoating I had the mast unstepped and restepped, rewired it and fitted new masthead lights, fitted new cavita lines and polished the hull, stripped about four layers of antifouling and applied new, installed a new holding tank and toilet and no doubt many other jobs. The beer and olives were saved until after launching.

 

[NigelCraig]

Thanks guys for information on gelcoat - could anyone help me with the repair to rubbing strake?

 

[NigelCraig]

G'day Nigel,

Gel coat is not used when fully coating a hull, 'flow coat' is what is used. Flow coat is in face Gel-coat but has wax added so that it need not be covered to cure.

Many boats are re-coated with flow coat rather than paint, it's a lot more work but tends to last longer and the finish on a new coat of flow coat can be made to look spectacular.

Tiny bubbles in the boot topping area are a sign of moisture under the paint in most cases, but can appear under the gel coat, don't let them worry you, in paint they often go away by themselves, in gel coat they can be cleaned up and re-coated.

Good luck and fair winds.

Thanks mate
but if recoating topsides, where is it normal to finish - at or under the boot top?

 

[alahol2]

Other main issue is repairing a teak rubbing strake, of roughly 5cm by 2cm section - it's lost a big splinter at the aft end which runs through one of the screw holes. I have a short section of teak but the section profile is marginally too small to replace the whole end bit with a scarf joint. Could I just replace part of the end section? i.e. with a scarf joint for the vertical join but a butt joint longitudinally - obviously that means a lot more exposed join for water to get into. (you can see my carpentry skills are non existent!) And what sort of glue to use? I envisaged just unscrewing part of the strake and supporting it, enough to get a tenon(?) saw in to cut a piece out. Any idea how long to clamp the join before I can screw it back?

Yes, you could do a partial insert of new wood. I would probably use Balcotan (or equivalent) because that's what I've got. I guess I would clamp it overnight. Next day put a couple of vertical screws (from the bottom) to ensure the scarfed-in piece of wood doesn't break out when you clamp it back round the curve of the boat.
That's my take on it but I'm not a carpenter.

 

[oldsaltoz]

The answer really depends on what condition the area under the rubbing strake is and also how snugly it fits to the edge of the hull/deck joint.

Needless to say if you can get a good finish right to the edge of the rubbing strake then go it.

You can do full job next time you replace the rubbing strake. By the sound of it's a bit on the thin side anyway so ot my not be too far off.

Good luck and fair winds.

 

[Boo2]

I watched a couple re-gelcoat the topsides of a 38 foot boat in Greece. I was surprised that it was relatively easy, although labour intensive. The final finish was excellent, and of course gelcoat is far more robust than paint in resisting the knocks and scrapes that boats are subject to.

How do you actually do this ? Is it sprayed on, or rollered on or brushed on or what ? It flows to a level surface does it, without drips and runs ?

Boo2

 

[vyv_cox]

They ground out the old gelcoat with an angle grinder, then cleaned up the surface flatness with an orbital sander. The gelcoat was rollered on, I think about six coats but not sure about that. They then used the orbital sander with progressively finer papers, then polished.

He told me it was far easier to do than two-pack painting, which he was using for the cockpit. If any runs occurred they were easy to grind off when cured. It was the topsides of the hull they were doing, so all vertical surfaces, but runs seemed very rare with relatively thin coats.

 

[nimbusgb]

Just vinyl wrap it ........ Far cheaper, quicker, more environmentally friendly and simple to repair.

 

[Avocet]

One good thing about gelcoat is that it's usually coloured all the way through and is far thicker than paint, so at least when scratched, it doesn't show a different colour underneath. There is also the philosophy that sometimes makes buyers wary of painted GRP boats because they start wondering what's underneath!

On the rubbing strake issue, I replaced Avocet's some years ago. I had to join them and a 6:1 scarf joint was barely adequate. If I was doing the job again, I'd try to do an 8:1 scarf. If you're using teak or iroko, it's worth standing the cut ends in some acetone for a bit prior to glueing them to try and get some of the oil out of the end grain. I used epoxy thickened with micro fibres, but it's a good idea to put some neat (and warmed) epoxy on to each cut end first, and let it go tacky, then do the proper joint. That wasy the thin resin will penetrate as far as possible into the wood.