Rapid fire questions.

[Paul75Participant @paul75]

[Paul75Participant @paul75]

Hello Everyone.

Can anyone recommend products for the following actions please?:

1) Painting a GRP hull (worried about using paint with the wrong solvent)

2) Wet and dry paper for roughing up the inside of a GRP hull prior to epoxying wooden boarding to carry batteries etc

3) Wet and dry paper for cleaning up electrical contacts prior to soldering

4) Marine grease to syringe in to the rudder post sealing tube

Many thanks,

Paul.

[neil hpParticipant @neilhp]

1).etching primer to start the paint job ( all spray paints from outlet like Halfords ) after wiping down with a cleaner from a car body shop….then onto a filler primer…….and then onto a normal plastic primer grey white or red depending upon colour of top coats…..rubbing down with a 400 grade wet and dry on the first coats and then down to a 600 grade for the final coats of primer before top coats.

2) use normal abrasive papers, ( not wet and dry for the inside of the grp hull………..gives a better rougher key for adhesion.

3) a 200 grade wet and dry used dry for cleaning your electrical contacts.

4) I use a mixture of vaseline mixed with carbon powder dor greasing up shafts, and I sail on salt water…..never get any ingress through the tubes and a full grease up lasts a season in salt water.

hope that helps. neil.

[ashley needhamParticipant @ashleyneedham69188]

Neil has it.

Personally I like to use fine wire wool to clean up contacts..wire ends and so on, if required, but if they are shiny then perhaps a degrease with thinners would be ok. IF the electriocal bits are plated, too rough a scrubbing will take off the plating.

Ashley

[Peter FitnessParticipant @peterfitness34857]

I agree with Neil and Ashley regarding rubbing down a hull, although I use marine grease in my prop and rudder tubes with good results. I sail in salt water, as does Neil, and I have not yet had a problem with marine (outboard motor) grease, although the vaseline carbon powder mix sounds good.

I make my own prop tubes and silver solder a grease tube into them, with a cap, also tube, that slides over it. I fill the cap with grease from a syringe, then gently push the grease into the whole prop tube, giving a good water seal. I know there are those who claim that grease can slow a motor down, and it probably does, slightly, but for the type of boat I operate the power loss is negligible. High performance boats may be a different matter entirely.

I have attached a photo of one of my home made tubes which should explain what I mean.

Peter.

[Paul75Participant @paul75]

Thanks everyone for your replies.

The model has already been painted but I want to change the paint scheme. Would you solely recommend using spray paint? I wouldn't want visible brush strokes in the finished paint job but, on the other hand, since the model is fairly large I'd have to fit my shed out like an automotive paint shop to cleanly do the spraying! Can anyone recommend some brush applied paints fit for the job?

Thanks,

Paul.

[neil hpParticipant @neilhp]

ah, paul you now have a big problem if your boat has already been painted, in that you have to determine what sort of paint has been used to paint it with in the first place………. If it was previously painted with a cellulose paint or acrylic paint, then a rub down of the old paint to give the new paint a key to adhere to will be ok…………..however if it's an older paint job on an older model you might find that (if brush strokes are visible…then it definately will have been) painted with an oild based enamel or house hold paint………………and the spraying of a car spray will absolutely kernacker the underlying paint and act basically as a paint stripper, bringing off the old paint in lumps lick orange peek cracking.the basic rule is…YOU CAN paint enamel or oil based paints ON TOP of celulose/acrylic spray paint, but YOU CANNOT spray celulose/acrylic paints on top of enamel/oil based paints.if you can't find out what the paint was that was used to paint the boat in the first place, then your best bet is to paint it with enamel paints, or rub it down to base wood and start a new paint job totally.neil.

[ashley needhamParticipant @ashleyneedham69188]

I have found that you can rub down Humbrol enamel with very fine wet`n`dry and then T-cut it afterwards to get a "spray gun" finish, just let the enamel harden for a few weeks.

This will be a safe way to repaint if you want the ultimate finish without stripping back

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

The rudder tube is rarely a problen if the inner end is above the waterline, but an application of water resistant grease during the fitting of the rudder invariably lasts until the next time the rudder needs to be de-mounted (say, for prop shaft attemtion).

Cleaning metal prior to soldering. It just needs to be free of grease, paint, dirt and tarnish. The first three respond to a wipe, application of preferred degreaser (meths on a cloth works well and is cheap and readily available), the tarnish just any fine abrasive paper, but glasspaper is preferred since it doesn't leave any conductive residue where its not wanted, and a final wipe. If the component legs are pre-tinned, the tarnish will vanish when it meets the soldering iron and fluxed solder. If the surface is protectively plated, (like a battery) the plating needs to be removed. Gold plating (as some component legs) solders very readily.

It is possible to get a brush stroke free finish using brushed enamel – it just needs a proerly prepared surface, a good brush, properly looked after, and the discipline to not be too greedy or hurried applying the paint. Thin coats, a generous wait for drying and a gentle rub down before the next coat. Much the same as spraying – poor preparation of the workpiece and painting environment can cause a spray job to be just as rough as any brush job. Done properly, both are equally good. Of course, if not stripping back, any blemishes left will be highlighted in the new finish.

[Peter FitnessParticipant @peterfitness34857]

Malcolm, I have to disagree with you regarding the rudder tube, even if the inner end is above the water line (as mine all are) although the problem is probably confined to salt water. I have found, from bitter experience, that it is absolutely necessary to coat the rudder shaft with a thin film of grease, preferably marine type. I had two rudder assemblies corrode together so badly that I had to cut the tubes with a Dremel cutting disc to remove the shafts, and this on brass shafts in brass tubes. As I said, it is very like only a real problem in salt water but, as I sail almost exclusively in salt water, I am now very particular with my rudder assembles, and check them all regularly.

You gave very good advice regarding soldering and painting, and if your protocols are followed there is no reason why excellent results would not be achieved.

Peter.

[Malcolm FraryParticipant @malcolmfrary95515]

Hi Peter

I sail almost exclusively in salt water, (salt and silt, really) and have found that the only time I've had a problem was when the top of the rudder tube was too close to the waterline. Then again, it's a lake, so if the waves are too big, the weather is not what I want to be outside in, so I retire to the pub and think thoughts. The water resistant grease has always done an adequate job for me, and is mostly there to stop the silt working its way in. As opposed to a prop tube, where there is fairly constant rotation and a lot of force (hopefully) and the need to minimise drag, the rudder tube is much less critical.

Obviously, both our solutions work for us. Brass on brass can be tricky – there is nothing to say that their mix is identical and any difference will give rise to the chance of electrolytic corrosion. Having a liking for plastic for tubes and/or bearings in the rudder department, I don't get that problem.

MalcolmF

[Peter FitnessParticipant @peterfitness34857]

I have to say we don't have a silt problem in our small lake, I imagine it could cause problems. I like the idea of plastic rudder tubes, they would certainly not cause a corrosion problem. I will have to look for a source of suitable plastic for future models.

Peter.

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