Not sure what you mean by a finish sander.  We're putting the finishing touches on our first boat building project, the Skerry.  All our sanding was either by hand (for the finishing work) or with a random orbital variable speed sander for the rest.  We bought a 5" DeWalt and it worked fine.  We used grits from 40 to 220 for machine sanding.  The sanding between coats of paint on the hull was with 400 grit wet sanding and all by hand.  We'll varnish the interior in the same manner.  A useful attachment is a shop vac that you can attach your orbital to when sanding to eliminate dust in your shop or garage.  Hope this helps.  Bob H

I use a number of different sanders and methods depending on what I am working on. I begin with a 5" random orbital sander on the flat areas, and then a 'mouse' detail sander to get into the corners and narrow spots. For the inside curves of the fillets, I wrap sandpaper around a sponge sanding block, and I also use a rubber hand sanding block in a number of situations.

My 5" random orbital sander is a Rigid brand, from Home Depot.  It has a soft start and variable speed for excellent control.  It also has a good dust collection canister, or you can hook up a vac hose to it.  - Ron

I have had a Makita Orbital Sander for a number of years and recommend it with no reservation. It has given years of hard service and is still going strong.

Christine

I can second Christine's comment on the Makita.  I've used it for sanding on probably 6-7 kayaks.  Good dust control when attached to a shop vac via smaller diameter hose.

I have a Porter Cable that I definitely would not recommend.  It's the reason I purchased the Makita.  Also Home Despot's Rigid line of tools are great in my experience (drills, 6" jointer planer, oscillating sander, thickness planer) but I've no direct experience with their ROS (random orbital sander).

 Jim

If you take care when applying your epoxy, handing sanding the entire kayak is not that bad of a job.  I power sanded 2 CH16 for a bright finish and hand sanded an entire MC16.5 project for a painted hull.  The advantages of hand sanding are: no swirl marks, better control over cutting through the glass, less heat build up under paper, less dust, less expensive.  You will spend 4-5 hours more on sanding but it's time well spent.  It's very easy to complete a S & G kayak with no power sander at all.  Chris

I agree with Chris J. Especially if you don't have much experience sanding epoxy and fiberglass, it takes a little while to understand what you are seeing. And I find that the areas that have subtle concave curvature along the hull, where a ROS will tend to quickly cut into the glass on the outer edges, are quite large.

I think on the first kayak I sanded, because I had wired the hull rather tightly, large sections of the side panels had very slight concave curvature because the chines were slightly "pinched". This curvature was imperceptible until I laid a straight edge vertically along the panel. It was enough curvature to make it very easy to sand through the glass on the outer edges while trying to get at the shiny patches in the center. 80 grit paper on a random orbital sander will cut through the glass very quickly so you need to use great care, avoid concave sections of the hull, and watch very carefully. I wasted much more time trying to patch and feather small sand-throughs than I would have taken just sanding the hull by hand.

Second kayak, I just have used 3m stikit sandpaper on a flexible fairing board, sheets of sandpaper folded down the center with a little contact cement in the center, and some sanding blocks, hard rubber and various softer foam blocks. This was a little slower but not bad, much more peaceful and easily controlled.

If I ever go back to a ROS, I will restrict its use to those few areas that are convex, or  very flat, such as the top center of the deck, and center sections of the bottom and side panels.

--

Ogata (eric) 

Good point eric, about using the ROS on a kayak.  I built the Jimmy Skiff, which has relatively large, relatively flat areas, where the ROS is very useful.  I also used a foam interface pad on my ROS, which did a nice job where there was a slight curve to the surface.  This allows the sandpaper to conform to the surface, and avoid flat spots and edge digging.  I bought this at Newfound Woodworking, as CLC does not sell these. - Ron

A handy sanding trick I learned was to squiggle magic marker on the fill coats before sanding.  That gives you a accurate visual reference and makes it easy to sand off just enough without cutting in too much.

That's pretty cool JimKoz.

And Ron, I agree a Jimmy skiff, or any boat with large sections of flat or convex plane surfaces would make me much more enthusiastic about pulling out the ROS, dust collector and ear protection.

It's unclear what type of boat the original poster was considering and I tend to have kayaks on the brain. The two kayaks I have worked on, a Chesapeake 17LT and a Shearwater 16 hybrid do have significant sections towards the center of the boat on the bottom and side panels, and a lot of the deck that could be handled with a ROS. Probably could take those down quite quickly, maybe an  hour or less. But seems to me it is all those fiddly sections near the bow and stern where the curves get complicated where the ROS becomes less useful, possibly dangerous and where the majority of time is spent. And in my case, even significant sections of the side panels, that looked flat to the naked eye did have just enough curvature on my 17lt to cause me some problems even where I wouldn't really have expected it. Using a thicker pad on the ROS would have helped me there. But this is how I learn:)

And, I think I was lulled into a little ROS trouble by the "Zen of Wooden Kayak Building" DVD.  John Harris just makes it look a little too easy there! You just whip out the ROS and with the tinkling of little bells, and a star dissolve, you magically have a kayak ready for varnishing! :)

Bottom line, if it is my boat, and my time, I'll tend more towards the honest, hand-sanded labor, at least until I have more experience. It's really not all that bad. If it was someone else's boat, well what the heck, get 'er done! 

 --

Ogata (eric) 

Something I found to work great for hand sanding is a Sand Devil.  I found it for sale at Amazon.com.  it uses 3X21 sanding belts and is pretty comfortable on the hands.  I always end up with hands cramping with the smaller blocks.  It fills the niche between a small block and a larger fairing board.  Costs about $20. 

The one problem I have with hand sanding is the dust. My power sanders all have vacuum connections, but I haven't figured out how to efficiently hook up my shopvac to a sanding block. That's one reason I like wet sanding so much - it's quiet and dustless, in addition to all the other hand-sanding advantages.

Laszlo

Yep, for me it;s fairly simple. Top-quality sandpaper, the right block for the task, and all sanding done by hand.

Clean (relatively), quiet enough to listen to music (and to do while the kids are asleep), and pinpoint control over pressure and surface finish. I wouldn't sharpen a plane with a grinder, so I wouldn't sand a surface with a whirring engine.

But, keep in mind, I don't use a power tool for any part of a boat. Even my drill is a hand-cranker. The price is a little time, the benefit is a workshop with potted plants, a sofa, art on the walls, music, a rug and a glass of Australian red on the bench. A fair trade, I say.

Hey Laszlo, I am impressed!  If you can hand sand fast enough to kick up dust then I need to learn your method.

Even thou I only have one kayak under my belt (2 more in progress), I have been making fine furniture for years.  At the wood stage I plane, use a long board, and a vibrater sander.  With the epoxy I used my right angle Porter Cable DA (dual action).  You can get a sponge pad for the curved edges and use 150-220 grit.  With the varnish, it is strictly wet sanding by hand.

The difference between a DA and a ROS is that a DA has a right angle body, comes in electric or air power, is much faster, speed is adjustable, and you have more options.  It can be more aggressive so you have to be careful, and they are a lot more pricey.  But once you master the use of a DA, you will laugh at ROS's.  Auto Body Shops have been using DAs for 40 plus years.

Kev

For what it's worth, I have a recommendation. A good HEPA vacuum dust collector is a must have. Before I built my Peeler Skiff, I questioned many builders at the Woodenboat Show and the always mentioned vacuum dust collection. Many recommended Festool products. One of the best decisions I made was to buy a HEPA dust collector, a 5-inch orbital sander, and a finish sander -- all from Festool.

-Dick-

   Mirka  sanders are made in Finland. Therefore they are Finish sanders. 
 

George K

   The Mirka abranet sanding net is the stuff to use on epoxy, no clog and lasts far, far longer than paper.

   Laszlo - Mirka do some great little hand sanding blocks that vac connect.

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I have a10-year old DeWalt ROS, and it works well (on my second boat now), but it has one annoying characteristic: after you switch it off, it takes a long time (maybe 7 seconds) to come to a stop.  So I am forced to stand there holding it, patiently waiting until I can set it down.

Has anyone found a ROS that has some sort of braking when shut off, so it stops quickly?  I also have a DeWalt miter saw, and it comes to a halt within one second after you release the trigger.  I just wish my sander was like that...

Doug