How to Prep a hull for paint?

[Apples1]

Hey all,

I am sure this has been covered previously but i couldnt find it in the search,

What is the best way to prep a hull for paint, IE, wet and dry? grade?, do i sand the primer also what grade?

and also what type of paint is ok enamel? this will be a Spray can Jobby.

Cheers Blokes.

[egneg]

Clean the hull thoroughly with soap and water then follow up with wax and grease remover. Wet sand (add a couple of drops of dish soap and soak the paper for 10-15 minutes) with 800 grit (use brown scotch-brite in the corners and tight spots). The hull should be completely dull - no shiny spots.. Wash the hull again followed by wax and grease remover. When it is dry use a tack cloth just before you paint (hint - air out the tack cloth for a while before use). Good scratch is all that is needed unless you have pinholes or other surface irregularities if so use a sandable primer. Enamel is ok but I prefer a lacquer for spray bombs. Make sure the paint is compatible with everything. Even custom painters will shoot a test panel before the final paint.

[Apples1]

whats a tack cloth?

[egneg]

It is like a cheese cloth that is sticky. It is used to get dust and small bits off the surface before you paint. Good to use between coats to remove overspray as well.

[Apples1]

cheers bloke

[Flying Scotsman]

Enamel is ok but I prefer a lacquer for spray bombs. Make sure the paint is compatible with everything. Even custom painters will shoot a test panel before the final paint.

Very good advice from a Fembot twit . Chuck, I would also suggest a prime coat in all cases and a wet sand prior to the finish coats.

Douggie

[Apples1]

....so clean surfaces and start sanding surface with 800 grit till smooth, clean again, prime and then sand with 800 grit again? then paint, does this sound ok? BTW i found some nice laquer to finish to hull in. thanks guys.

[egneg]

....so clean surfaces and start sanding surface with 800 grit till smooth, clean again, prime and then sand with 800 grit again? then paint, does this sound ok? BTW i found some nice laquer to finish to hull in. thanks guys.

Sounds about right - but I can't stress enough to do a test panel first. That way you learn on something besides your boat.

[Jeff Wohlt]

800 is too fine... Use some 400. You need that level for paint to bite well. Also...use block sanding where possible for nice straight areas.

For really straight blocking you can shoot a light mist of dark paint over it and then block sand lightly to see where the paint is left...low spot...use some spot puddy to fill these and then finish and prime that area again. All you need is a light fog over the hull to do this. This how a nice paint job is put on a car.

I like a high build sealer/primer. Then wet sand with some 600 and get it masked and ready shoot. Use some decent paint like duplicolor or a gun for great jobs.

Color sand (if it is not a flake paint) bewteen coats then with 800 between color and the clear coats except the last two coats.

Always use a tack cloth...any auto parts store should have them...buy several.

At leat this is how I do it. Just got a new gun so since the weather is getting better I have about 5 boats to paint. Cheaper paint out of a gun is still much better than rattle cans...duplicolor has the better nozzle than krylon and will be a better paint for FG hulls. Use their clear as well.

[egneg]

The difference is a boat flexes where as car panels don't. The deeper the scratches more paint buildup is needed to fill. I try to keep the paint layers as thin as possible because I believe this gives you better adhesion and less chance for flaking and chipping. 2 or 3 thin coats are far better than 1 thick coat. I also do not wet sand between layers unless there is a problem with the paint. If you allow the paint to flash off but not completely dry the new layer will meld with the previous layer giving you a chemical bond. The 2 types of bonds are chemical and physical. You start with the physical bond with scratch to give the paint more surface area to bond to. After that as long as you paint within windows (depends on the paint) you will have a chemical bond. That is why I prefer lacquers as there are no windows you will always get a chemical bond. Unlike uros that are now used to paint autos you have small windows (24 hours) if this is exceeded then scratch is required for a physical bond as the time has passed to get a chemical bond.

Clear as mud right? This is how I paint and I am not saying that any one way is right or wrong as there are as many different methods as there are painters.

[Apples1]

yep thanks... MUD, makes sense though.

[Blackjack-sven]

When I do paint jobs, I basically do a first scratch with 400, dust with black for low spots, and continue this process through the 600, 800, 1000, 1200, paper. When I get ready to use the 1500, 2000, 3000 paper I don`t bother with the scratch anymore and use the chem bond technique. *NOTE* That the chem bond technique should be started between the 1200 and 1500 papers. Only scratch if there are problems with the paint. I also use clear coat for two coats at the end to keep the paint from becoming damaged at any time during runs.
I use a lot of thin paint layers to keep the surface light, and an insanely fine paper in the end to keep the surface as smooth as possible.

[Blackjack-sven]

The difference is a boat flexes where as car panels don't.

As a mechanic I would disagree with this part of the statement. A car flying down the road has an incredible amount of wind `fluttering` the metal surfaces. BUT this is why they do their paint the way you explained it. Boats just flex more and the bonding concept you outlined helps keep the boat looking great for a great deal of time.

[Jeff Wohlt]

Unless you are melting laqu paint into the hull...which you might on some Abs these are all mechanical connections.

There are no body shops using that fine of paper to begin the primer stage or even the first coat of color.

[Boatman]

my 2 cents... 220grit, prime, 400grit, paint. cleaning before each step with either soap and water and or tack rag. not much to it really. If it were for "HOTROD" magazine maybe finer but not for my boats. Thin coats is about the most important. paint has "flash" time in which it starts to tack and thats the time you take between each coat. just take your time so you dont have to do it twice.