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I'm getting close to painting the hull and I'm wondering a few things about sandpaper and paint. I've never known what the difference is between wet sanding and dry sanding and what are the pro's and con's of each. I need a little enlightenment here! On the paint (I will very likely go with the Severe Weather from Valspar), how many coats do some of you recommend. In between coats what sandpaper should I be using? What grit? Dry or Wet or both? The way things are going I should at long last have her turned upright again in a few weeks. I may even get a good bit of prep work done on the deck, etc before the wet weather gets here. Usually the first of November.

Tom,
Here is a link to what is basically the same process that I go thru to finish out a boat building project.
Good information and he knows what he wants from his finishwork.

http://duckworksmagazine.com/05/columns/...6/free.htm

Dry sanding, you know what that is. Garnet paper or aluminum Oxide, paper back. Surface of the paper gets clogged quickly with resin or paint. So that needs to be removed or you change paper surfaces more often. Then using a tack cloth remove any and all residue before applying primer or paint. Also between coats.

Wet sanding requires a Wet/Dry paper or cloth backed sanding surface. Also it is the use of a liquid applied to the surface to be sanded so that the sanding material is flushed away as you work and the paper remains clean so it cuts thru the surface more evenly and quicker. This can be water, mineral spirits or other liquid that is compatible with the paint. Generally with the later coats of primer, and/or paint a wet sanding with clear water and Wet/dry paper (150-180 grit will really leave a nicely prepared surface for the rinal coat of paint. Rinse down with a wet lint free towel and ring out and wipe again until it is free from any residue, then let dry completely. A hair dryer run over the surface where there are any joints or places where moisture might remain will help to dry that out more quickly. If you are going for a really nice, High Gloss surface finish, then move on to 220 grit/wet/dry paper and then 400 or even finer depending upon how far you want to take it.

Wet sanding the final coat of primer will leave a really nicely prepared surface for your paint. I apply at least two coats of high build primer before I sand it. Letting it dry completely before sanding. When I sand this surface, I'm looking for any uneven spots, high/low places as well as rough spots. If necessary I fair these out with the long board before going on further. If they are just a little low, I apply additional coats of primer to build them up and then sand even with the surrounding areas.

Depending upon how particular and how nice you want your finish to be this can take some time. But if you are particular about a fair surface and a nice 5' finish is what you are after then it is worth the time and effort at this point. Once the primer coats are all sanded and you feel it is ready for paint, I will apply a tinted coat of primer overall just to get it all even and really see what I'm going to paint over. This I wet sand with 120-180 grit wet/dry paper and water. Doesn't take long at all at this stage. Just to make it nice and even overall.

Then the paint goes on with at least two coats applied in thin coats rather than a thick one. That will assure better coverage overall. I often wet sand after this and apply a thin finish coat with a roller and tip it out with a brush or spray it on. That will hold up well over a long period of time and be a nice even finish coat. I will often apply an additional coat or two on those areas that will likely take the most abuse. Chine, Keel, stem, between the rails and rails themselves if painted. Let them dry completely before you sand or use. Remeber a Latex based paint will not be completely hard and cured for several months. An alkyd will dry and cure over a few weeks total. But follow the Mfg recommendations on the can for recoat and sanding times.

The best way to see if it is sticking well is to apply a coat to a scrap surface or out of sight surface first, let it dry and take a razor blade and draw a cross hatch on it. Then take a piece of Scotch tape and stick it down over the cross hatch and lift it up. If the tape comes off clean, the paint or primer has a good bond and will hold up quite well. If it comes off on the tape, the surface either needs to be a bit rougher or the primer/paint is not compatable with the underlying surface. That is one reason I like the Kilz II Primer. It is compatable with almost everything.

Good luck and have fun. Might as well, patience and a little extra effort in those hard to get to places make me feel a lot better even if I'm the only one that knows I did it.

I understand fully what you are facing, I had to interrupt the building of my Weekender back in 2002. It hung in a storage unit for 3 years and I was able to get it on a trailer last summer only to have to have it sit outside over the winter unfinished. But covered. When I uncovered it in May, there had been some water sitting inside the cabin. So there was mold and mildew that I had to take care of before I could do anything. Along with quite a bit of raised grain and a little panel damage to repair. This year, I've managed to get 99% of it finish painted before I've had to cover it up. Just have the seat backs and cockpit sole to apply a finish to and if the weather is nice in October, I might be able to get that done first too.

Just keep on going, it will all get finished in good time. And it will float! :wink:

A good rule of thumb is you'll need more primer if the surface is particularly rough or if you want a mirror finish. Mirror finishes require ten times more effort. Most folks can live with a 120 grit under paint and 220 under clear.

Knocking down a surface is pretty easy with the right tools and techniques. The problems I see most people having are; trying to use the wrong tool for the task. An example would be using a jitter bug (1/4 sheet palm sander) to do heavy material removal or surface flattening. It's just too small a gizmo to do a reasonable job. Another common problem is continuing to employ a spent piece of sand paper. The paper will clog and dull very quickly. I buy it by the case and on big rolls. I use a lot of it and change it often. This saves a lot of effort, because the paper is always cutting and I'm not dragging chunks of whatever is clogging the paper around on the surface, which can do damage as well. After a while you'll feel when the paper isn't cutting like it should. Change it then, don't wait, it will not get any better and you'll be wasting time.

If you're knocking down a large surface in the beginning stages of the finish effort, use course enough grit to get the high spots, but not so rough that it digs up the low spots too. Flatten the surface with a boogie board (long board) using opposing 45 degree angle passes. This tool (you can easily make one) will hit the highs, but leave the lows alone, which eventually will get filled with paint, filler or have the highs brought down to meet them.

The random orbit sander is a finishing tool. Below 120 grit, you're wasting time with this machine, so don't try to make it remove lots of material.

The belt sander is course material removal tool and will quickly remove a lot more than you wanted it to. I don't use it with anything finer than 60 grit, but some will use 80. I'm on to the orbital by 80.

The bigger the sander, the easier it is to make a surface flat or smooth. I have a jitter bug that has a 14" foot screwed to it. I use it as a finishing sander on large areas.

In the end, finishing boils down to the effort and time you'll willing to invest in playing around with the thing. Finish work is 90% prep and 10% actually applying paint, varnish or other coating material. The "brush in hand" time is minimal compared to the surface prep. The finest clear finishes I've done have 20 plus coats of varnish, sanding between each coat, etc. This was after countless hours of smoothing the surface before a drop of varnish touched it. A reasonable finish can be had with four coats of varnish, but it will not last long in a southern sun.

I personally like four coats of primer, much of which gets sanded off during the smoothing process. When all is said and done, two clean, fresh coats of primer go on, before paint. This gives a good base.

Let the machine or paper do the work. Don't try to speed things up by bearing down on the tool. It will only kill the tool sooner than necessary and the paper will die very quickly.

Buy good paper, not the el cheapo stuff from the local hardware store. The good stuff will cut much longer then the cheap stuff. I like Norton products, but this is a personal preference kind of thing, you'll have to sort out for yourself. Ceramic papers are the best, but cost more. These papers will last 5 times longer than conventional papers.

Wear a mast, a good one, not the cup and elastic thingies, but a real mask. Unless you're into upper pulmonary disorders or sneezing up what ever color you were working on that afternoon, wear the damn mask, trust me. Hacking up yesterday's 100 grit session with your cabin color, floating around in the sink, isn't any good for you. Many builders have learned this the hard way. Generally, it affects career boat builders, but it can do you harm too, so be warned and good luck.