But this post isn't really about painting - it's mostly about the prep work. Boats are much harder to paint than a house. If you're painting the inside there's wood trim everywhere or very tight spots and odd angles or funny bits of hardware you have to mask off. You (or people who visit your boat) are also likely to be a lot closer to the painted surface than the inside of a house. And you probably are using gloss paint or varnish because it's more scrubbable. So flaws are more readily apparent.
The truism in painting is that prep work is 90% of the job. It doesn't quite take 90% of the time but tge importance is quite true. So here a few thoughts from somebody who has painted more than his fair share of this boat and our last one. Neither boat was a production boat with a molded fiberglass liner. So interior bulkheads and cabinetry were mostly varnished wood (last boat) or painted (this boat).
A lot of the prep work is cleaning the surface before the paint is applied. I often start with spraying the surfaces with an all purpose cleaner and wipe it down well with lots of rags. I'm trying to get off dirt, mold, kitchen grease, and dust. Then I sand to roughen up the surface so the paint will stick better.
We have 3 sanders and an angle grinder on Ceilydh and they all serve different purposes.
A 5" Porter Cable random orbital sander. This is a good all purpose sander, especially if you hook it up to mini shop vac. Hooking it up to a vacuum allows almost dust-free interior sanding. If you're living aboard and moving all your possesions out of the way would be a chore, then this is a great option. If you only have 1 sander aboard, get this style. Note that Porter Cable used to use a 5 hole velcro sanding disc. Everybody else seems to have standardized on 8 hole. So get an 8 hole sander so you can replace the sanding discs in remoter location. Such as Australia I've replaced the velcro pad a few times with aftermarket stick on ones and at least 1 set of the external orbit bearings. It just keeps running.
Note: The vacuum draws 6.2A @ 120V and the sander about 3 A = 9.2A @ 120V or about 100 Amps DC for the the inverter. I can run this combination in direct sunlight (solar panels putting in 16A) for a few hours before the battery voltage starts dropping. I'm not running it continuously. I'm stopping to change sandpaper, move the vacuum, etc. The limiting factor is the inverter; it has a 1000 W continuous rating and it will alarm and stop working after a few hours. You have to let it cool down for 20 minutes before it keeps going.
#2: The Beast
2nd from the left. If you are building a boat, then you must buy this tool or something a lot like it. A 6" Porter Cable random orbital sander makes short work of lots of fairing or rough objects. It's variable speed for when you're trying to be delicate but mostly it runs at full throttle. However I don't dare use it inside. It throws dust everywhere. It uses sticky discs which are much cheaper than velcro discs, especially if you buy rolls of 100 from the autobody supply shop.
#3: The Present
The red one with triangular pad. This was a present (I can't recall if it was birthday or Christmas) When we were living in Annapolis on our last boat Di did a bit of ahem casual work, varnishing on other boats. Varnishing always means sanding, and this little Milwaukee detail sander is great on trim and in tight corners. It's about 90% as good a sander as the Fein multitool without the cost or versatility of the Fein. It's a 'nice to have' sander but unless you own a Taiwanese made teak forest interior it may not be required. Unlike the Fein you can also hook it up to a vacuum.
#4 Angle Grinder
The Skil one on the far right. It's got to be 20 years old now. Not really a sander except in the crudest sense. But when fitted with 24 grit wheels it can take down a bunch of fiberglass in a hurry. If fitted with 50 grit and a delicate touch it is surprisingly good at smoothing down lumps of resin or blobs of glass. Do not use indoors unless you tent the area affected and allow 2 hours or more for dust removal.
Power tools - final thoughts
The tool companies are now making special "big box store edition tools". They look like the regular models but are often cheaper (both in terms of price and what is on the inside). Check the model numbers on the internet and maybe buy from specialist online tool stores. I tend to buy 'contractor grade tools'. They last forever if treated well. I won't buy Ryobi or Black and Decker or Sears. Don't buy 1/4 sheet sanders. They do a good job of vibrating your hand but are seldom useful for decent production. Buy corded tools, not cordless. While a bit more inconvenient to find an extension cord I'm never stopped in a project with a flat battery. The batteries do die and are costly over the life of the tool. Just make sure you have an extension cord that will reach the top of the mast so you can drill that hole up there. You're going to need a long extension cord in whatever boatyard you end up in someday anyway.
Masking Tape - One boatyard quote that I love: "You can tell the professionals from the amateurs by the amount of blue tape they use". It's quite true. Watch boatyard workers working on somebody else's boat sometimes and note the extent they will protect surfaces from paint, dust etc. with large amounts of cardboard, plastic and masking tape. If you are doing a multi day painting job use the 7 day tapes (usually blue or green) but check the label to see if they really promise good multi day performance. Some are just blue! This is really important outside in tropical sun. Beige crepe paper is good for a day or two but shouldn't stay on much longer unless you want to become intimately familiar with Goo Gone adhesive remover. I tried a blue mylar tape for this job and some regular blue paper tape to compare.
The thin mylar tape probably is going to give a nice clean edge - but it doesn't stretch around corners and is much harder to tear cleanly. You need to use your teeth. I'd use it on a nice staight waterline but probably not again inside. I also found out today that the primer doesn't stick to it and breaks off in nice flakes into your nice topcoat. Boo.
Protective Gear - when I was building the boat I was often blowing my nose after a weekends work and finding black or white snot in the tissue (carbon or epoxy bog). I became much more diligent about wearing my mask after that. Get a good protective half mask like the picture. Wear it all the time when sanding or using any 2 part paints. Change the carbon filters every 6 months or if you can smell solvents when wearing it.
If you're sanding inside with a shop vac, use ear muffs or ear plugs. They're quite loud
If you are a contact lens wearer like me, take out the contacts during sanding, and probably during painting too. Dust gets into your eyes and can float between the contact and your eye, really irritating it. I seldom wear goggles while sanding unless it's overhead or in a tight space and I know I'll get stuff in my eyes. A lifetime of contact lens wear has made my eyes pretty impervious to minor irritations but you might not be so lucky so also consider some eye protection.
Rags - after all that sanding you have to remove the dust. I try to be methodical about folding my rags into half, then quarters and then dampening them with water. If I pay attention I have 8 surfaces that I can use by flipping over, unfolding, and then refolding my rags. Change rags frequently. If you are short on rags, rinse them and re-use but use a 2nd clean rag for the final rinse. If you have a choice, use dark coloured rags for light surfaces (like white or light grey primer) and white rags for dark surfaces (like dark topsides paint). The contrasting colour makes it easy to see if you have wiped down a surface enough. One pass is seldom enough by the way. I often carry a rag in my pocket if the painting is in a particulary important place and wipe it down dry immediately before the paint is applied.
Questions or comments as always are welcome.
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