Best Sander for the Bottom

[Amorita34]

Every couple of years we like to go through and sand the bottom really well before a new coat of vc17. What we use is a couple of Porter Cable 5" random orbitals. They works good but seem to lack power to really get the job done in a timely manner. I have done to searching and have read people talking about the Festool 150. Is this really a faster tool? I am looking for something between the random orbital and a 7" grinder :-) . And the festool sounds like it has great dust collection for sanding inside the storage barn. Thanks for any feedback.

[Greggegner]

I like newmatic sanders, they are light and can be aggressive if needed. Get the stick on adhesive paper and you can get the job down. It doesn't take a huge compressor. Make sure you lubricate the sander before each use.

[Dsanduril]

If your budget can afford it the Festool really is a great piece of equipment. Their gear-driven "aggressive mode" is pretty much exactly what you describe, somewhere between a sander and a grinder. It does leave a lot of sanding marks (like a grinder), so you'll have to follow with finer grit in random orbit mode in order to get a good finish.

The dust collection is about the best I've seen, as long as you use Festo sanding discs. So, you have to be prepared to pay for those through the life of the tool as well. The hole pattern and extra holes are not usually found in aftermarket discs.

Having said that, I'm with Greggegner, I usually go pneumatic and wet for bottom paint.

[rognvald]

Amorita, I have a 25 year old Porter Cable 5" sander that does everything from light sanding to bottom removal. You might want to go to a heavier grit (40) if your bottom paint is thick and in bad shape as the lighter grits(60 and 80) will defintely take longer and use more paper. When you get close to the original gelcoat/barrier coat, switch to the 80 grit to finish your job. I don't think the problem is the sander. Good luck and good sailing.

[Exile]

It seems like there are fewer & fewer DIY yards these days and the ones that are OK with it often require dust extraction, esp. for toxic stuff like bottom paint. I've been looking at the Fein MultiMax oscillating tool. They have a 4.5" sanding disk attachment and dust extraction. Less $$$ than the Festool but still more than what can be had at Lowes & HD. The multi-tools are much more versatile and can be used in many other applications. Of course, Harbor Frght. has one on sale right now for $20(!), but you'd be on your own with the dust extraction.

[Exile]

BTW, how does one know when you're getting close to the barrier coat? Is it normally a different color, for e.g.? Often not necessary to sand that far but it would be good to know. Thanks.

[minaret]

The Festool rocks, but for bottom sanding a plastic tent and an 8" softpad are the way to go. Festool is much better than the Fein for not much more money. I own both.

[rognvald]

Originally Posted by Exile

BTW, how does one know when you're getting close to the barrier coat? Is it normally a different color, for e.g.? Often not necessary to sand that far but it would be good to know. Thanks.

Exile, it is normally a different color (grey,white,opaque) which is quite a contrast to your VC17. However, I used VC17 on my last boat for 16 years on Lake Michigan during the Summers and if you have a sufficient amount of paint on your bottom, you don't have to paint every year. You can lightly scuff the bottom with a drywall sander and 80-100 grit to expose the fresh copper/toxicant and relaunch. Its a slow sloughing paint and will eventually wear away. I never painted my bottom for the last 5 years I owned the boat and never had a fouling problem. You might just save yourself from a big job. Good luck and good sailing.

[Exile]

Originally Posted by rognvald

Exile, it is normally a different color (grey,white,opaque) which is quite a contrast to your VC17. However, I used VC17 on my last boat for 16 years on Lake Michigan during the Summers and if you have a sufficient amount of paint on your bottom, you don't have to paint every year. You can lightly scuff the bottom with a drywall sander and 80-100 grit to expose the fresh copper/toxicant and relaunch. Its a slow sloughing paint and will eventually wear away. I never painted my bottom for the last 5 years I owned the boat and never had a fouling problem. You might just save yourself from a big job. Good luck and good sailing.

Thanks for the info on the different color barrier coat. That VC17 looks like good stuff for fresh & low fouling waters but I went with Pettit Trinidad SR the last time and it's still holding up well in the high-fouling areas of the SE U.S. after 2.5 years. At $250/gal., however, I may have to make a different choice the next time!

FWIW, I'm now re-thinking the $$$ Fein multitool for removing bottom paint and will more likely go with a much less expensive 5 or 6" random orbital from one of the big box stores. The multitools are handy but I thought it better to go with something more purpose built for the job at hand. I don't put my power tools through the type of day-to-day abuse as someone like Minaret who works on boats for a living.

[keepondancin]

I have a Festool Rotex 125, 5" sander. Has both a Rotary/Orbital mode and a Random Orbital mode, and I have two vacs. It can be very agressive, or finish quality while capturing almost 100% of the dust. I haven't done the bottom yet, but have used it extensively, and always wonder why I didn't get it sooner. Thinking of all the sanding dust I have inhaled over the years, this system is a pleasure to use. I went with 5" rather than 6" as it is lighter, and time is starting to gain on me, and lighter is better than faster.

[Efraim]

BTW, no matter which way you go be sure to buy good quality sandpaper, makes all the difference in the world.

[Exile]

Originally Posted by Efraim

BTW, no matter which way you go be sure to buy good quality sandpaper, makes all the difference in the world.

Is "Mirka" a good quality sandpaper brand? That's what pops up on Amazon.

[minaret]

Originally Posted by Exile

Is "Mirka" a good quality sandpaper brand? That's what pops up on Amazon.

It's more about type of grit than brand. Open coat or closed coat is the biggest choice, closed coat is much more expensive and lasts much longer. Type of abrasive and type of adhesive used to make the grit matter too. Mirka makes decent grit. If you want high end, especially good closed coat, you go with 3M.
Indasa is cheap but actually gives good bang for the buck. I use a lot of closed coat for aggressive sanding like longboard fairing. The green 3M Imperial or even better the purple stuff are awesome. Purple cut is bonded closed coat with epoxy, it cuts like crazy. I always go up a grit with it.


3m Imperial™ Sandpaper Products (Purple) - 3M Sandpaper

[SailFastTri]

I've been using a Porter-Cable 97466 6-Inch Random Orbit Sander with Dust Collection Amazon.com: Porter-Cable 97466 6-Inch Random Orbit Sander with Dust Collection: Home Improvement

Been very happy with it. Owned it about 5 years.

For taking down bottom paint I like to work with 60 grit. It's fast and consistent. If I just want to smooth out a few bumps or chips, or put some tooth in the surface for a new coat of paint I prefer 80 grit. I never go finer than 80 on bottoms.

The coarser grits like 40 or 34 are too much like sanding with inconsistent pebbles, and I don't want to scratch through the barrier coat.

[billr]

Beware of sandpaper for multi-tools from McMaster Carr. We got a bunch of that last summer that must of come from China. It was hook-and-loop, and that hook-and-loop backing fell apart after 5 minutes of use. Normally, they are a good source, but obviously not for everything.