Fairing w/ Belt sanders

[cs]

Not to take anything away from you guys. Most of you know way more than me when it comes to this sorta thing and in fact I still consider myself a butcher of wood rather than a woodworker.

Why not fair with a belt sander? Is the problem that it takes off so much wood so fast? With a little practise and a steady and light hand a good quick knockdown of un-fair surfaces can be accomplished.

You do have to be careful or you will grind hollows or if you get on the edge of the belt a little it will dig in. But with practise and patiance a belt sander does a good job.

Please give your advice on this. I'm always open to learning new techniques and learning why mine aren't the best.

Chad

[Mike Vogdes]

It depends what your fairing I guess, if your working on a flat surface, and you can see your work, sometimes a belt sander will work ok. You get into trouble when you start to get tired, and your grip on the sander gets inconsistant. A belt sander can do a lot of damage quickly if your not carefull.

Sometimes a better choice would be a random orbital with some very aggresive paper, then work thru finer grits of paper to get your finish. I made the switch to air powered sanders a few years ago and they make all the difference. My Makita random orbital still gets a lot of use when air isn't practical.

[Ian McColgin]

I have a friend, cabenit maker by trade and very good boatwright, who can fair say the bevel for a scarf with either belt or disc, but large surface fairing is really for a bigger surface. On medium sized surfaces a belt sander is more likely to make ripples than a RO or disc.

The best use of belt sanders remains belt-sander races - long extension cords, squat on the sander and pull the trigger.

[Dan McCosh]

I actually do use a belt sander for fairing, and have even done the topsides. I also generally use a belt sander to fair in new planking. The trick is developing a touch, as you point out. The sander can gouge, dig in and run away. If kept moving in a circular pattern with a light touch it can do a good job. It takes practice. If there is a trick, it is keeping your eye on the surface being faired, not depending on the tool to do it's thing.

[Bill Perkins]

I'd make a distinction between surfacing and fairing .I've done "random orbit beltsanding " on bottoms to remove old paint or smooth out a rough surface . I don't see how you can fair with a beltsander since it has a ridgid foot that's only about 12 in. long .

When I built a cedar strip canoe ( which I think you may be doing )I found the strips were pretty much self fairing .I just had to smooth the surface with a R.O. sander ,which was fast enough. I think I would only damage the fairness of most strip planked boats with a beltsander ,not enhance it .If you intend to varnish the hull you'll regret any dings as well.

[ 02-06-2004, 11:11 AM: Message edited by: Bill Perkins ]

[JeffH]

Using a power plane for rough fairing large boats is pretty standard practice, so I suppose a belt sander would produce somewhat similar results (side rant: will somebody please make a decent power compass plane). The usual procedure is to run the plane is large sweeps in an X pattern, diagonal to the planking lines. This does a pretty good and fast job of knocking the ridges and high spots off. There is, however, no real good way around the elbow grease needed for a good final fairing...

Edit to add: I'll agree with Bill, in that a belt sander may be a bit extreme for a strip-planked canoe.

Jeff

[ 02-06-2004, 11:08 AM: Message edited by: JeffH ]

[cs]

Let me add that yes I'm doing a strip canoe, but it is not cedar. I'm doing it out of Douglas Fir so its not as soft as cedar.

Chad

[Todd Bradshaw]

Though it's certainly possible to sand a strip canoe with a belt sander, it will never be the tool of choice or the tool most likely to give you good results and a boat that you're proud of. Other than maybe walking along the gunwale, cutting the top down flush or working on seat frames, I've never met a professional strip-builder that had any real use for one.

It's unwieldy due to it's bulk and weight and when you get it on a curved surface it's often hard to be certain exactly which part of the belt is doing the cutting and exactly where it's doing it. Your Micmac is either straight or a convex surface everywhere. When you get to boats with hollows in their shape, the belt becomes even more difficult to use.

One false move on any canoe hull and you may have grooves cut by the belt's edges and there is no good way to ever repair them without making something pretty ugly. The same is true of flat spots and they often don't show up until you put the varnish on the hull - and then it's too late.

Since belts usually cost $2-$4 each, people also tend to use them longer than is ideal, still sanding well after the thing has lost much of it's bite. This leads to uneven surfaces as you go over an area more times than you should. Disks are substantially cheaper. You use them while they cut fast and cleanly and then toss them at the first sign that they are no longer doing so. There is too much time and money invested in the project to screw it up for the price of some sandpaper.

When you get to the stage of sanding the fiberglassed outside of the hull (and don't tell me you're one of those who doesn't sand it smooth as a baby's butt before varnishing - Pet Peeve - I'd personally like to take all those folks out and drown them and can't for the life of me see how they can leave a rolled or squeegeed epoxy surface and consider it ready for varnish, cause it looks like hell) the belt has to cut something much harder, but much thinner. You can go through it, or well down into it in a heartbeat.

Sand with whatever you want, but if you really want to be a good strip-canoe builder a belt sander isn't going to get you there.

[alteran]

So Todd are you saying a random orbital to start, then hand sanding with a fairing board, epoxy and then finish wet sanding with 2-4-600 or some such with a random orbital?

[cs]

Thanks Todd. I really do listen to your advice and take it to heart.

When I say fairing I'm not being fair. What I'm doing is cleaning up some spots. The belt sander was the just the first pace to get every thing on the same plan. Kinda like a big fast whirring hand plane. As far as it being heavy and hard to handle, I've used it enough that it feels comfortable.

After that first pass it is time for the more gentle means. I will be using my random orbital sander and my hand to truely fair it.

The belt sander won't touch the canoe again. From here on out it is ROS.

Chad

[Dan McCosh]

I wasn't thinking in terms of a canoe. A typical plank installation to me involves removing about 1/8 in. of material from a 4 in. x 8 ft. or so mahogany board, and fairing it into the surounding planking. I use a pretty aggressive approach, finishing off mainly with a random orbit sander.

[Todd Bradshaw]

I learned strip canoe building from guys who were doing it for a living, so efficiency and streamlining the process was important. For a home builder who has months (or even years) to complete a single boat, you may want to find a more peaceful solution, but big power, when applied properly, can do an awfully good job of fairing and sanding a stripper. I have yet to see any strip canoes which are fairer or smoother than those turned out with big disks, but I've seen a hell of a lot of them that aren't.

The tools: All, or nearly all, sanding is done with either 7" or 8" right-angle disk sanders (big suckers). I use an old Black&Decker 4500 rpm "Wildcat" with a 7" hard phenolic back-up plate and an 80 grit resin-backed floor sanding disk for initial wood fairing. It takes a couple hours maximum to fair the outside of a typical 17' canoe. Part of the reason that this thing fairs so well is that it cuts really fast and doesn't think twice about plowing down the ridges where strips meet as if they're not even there. Most other types of sanders won't do that. A good modern R.O.S. will do pretty well and is probably the best bet for home building, but the ridges still often take some extra attention, which can lead to wavy surface if you don't watch it carefully.

After the 80 grit pass with the big disk, the pad is changed to an 8" automotive "feathering disk". It's a hard plastic plate with about 1" of soft, closed-cell foam glued to it's working surface. The sandpaper, usually around 100 grit disks (paper this time) are glued to the pad with "feathering disk adhesive" (of course, but buy type-2 because type-1 heats up too much and bonds the paper onto the pad). These are quick passes and do more smoothing of the surface than fairing. Twenty minutes is about all it takes to do the canoe's outside. If you want an even smoother surface, following the 100 grit pass with a 150 grit pass will actually put a shine on bare wood. It probably also weakens the resin bond, so I wouldn't generally bother with the fine grit on a stripper.

Another thing which is important to this process is the glue used to do the stripping. Glues like TightBond and Elmer's Carpenter's Glue tend to get sticky and smear when they're heated from friction. This plugs-up disks and also does not sand smoothly and cleanly, which again can lead to a lumpy fairing job. Epoxy and Weldwood are harder and sand better with big power. Weldwood is what I've always used and it's worked great. Good color, too (brown).

We always used the same big sander to sand and fair the insides of the hulls, but this time we used a 7" rubber back-up plate made by Black&Decker called a "Super-Flexible". It really isn't all that flexible, but it will bend to fit the contours if you really lean on it. I can't seriously recommend this part of the process though. You can get as good or better results with smaller, easier-to-control sanders or hand-scrapers and have much less chance of sanding through the hull from the inside (been there - done that) or cutting yourself by touching the edge of the disk while trying to force it to conform to the shape.

Once the glass in on, the first step is to REALLY fill it. Add filler coats until the cloth texture is totally gone - and then add one more to sand off. With some resins, this may mean five or six filler coats, but skimping on them usually comes back to haunt you. The guys who don't sand the outside before varnishing spend hours primping their filler coats, trying to chase down and eliminate any drips or sags. In the end, they wind-up with a canoe covered by little humps and valleys of epoxy, which look just like what they are even with the best application job. I'd rather not be aware of the resin but look through it to the wood with as few distractions as possible and the best way to do that is with a truly smooth surface. This requires sanding.

I never dread the sanding process because I know I can get the boat really smooth. What I do dread is the varnishing process, because I'm not all that good at it and if there is something that's going to screw-up my smooth finish, it's varnish sags, not resin sags.

My filling process is to use fast hardener, a foam roller followed by a tip-out brush and thin coats. You roll one on, try to get even coverage tip it out and walk away. If it drips, it drips - ignore it. The critical factor is not adding a lot of bubbles. About 45 minutes later, you check to see if it's hard enough for the next coat and as soon as it will take it, you add it. Glassing and filling is all done in one long day where most of the time is spent watching resin cure.

Once the filler coats are cured, the resin is sanded smooth using the feathering disk again, usually with 80-100 grit paper to start with. I still use a big sander, but this time it's a Milwaukee that only runs 1750 R.P.M. The Wildcat used on the wood is too fast and smears epoxy. It used to work fine on the early polyester boats, but when we switched to epoxy we had to go to a slower one. Even so, just like on the unfinished wood, the speed of the big disk levels drips and sags in a heartbeat. Final finishing is done by switching to a 150-180 grit disk on the same pad. No hand sanding is needed.

So that's how you fair and sand a stripper when time is money and if you practice enough it will do a great job. I chopped the hell out of the surface of the first boat I ever used a big disk on, and you probably will, too. After a while though you get pretty good with one and the results improve dramatically.

If you want more info on disk sanding search the old WoodenBoat issues for articles about a guy named "Giffy Full" who was a master with a big disk. Why I can remember his name when this afternoon I couldn't remember my own zip code is a mystery to me. I'm seriously starting to wonder if I'm getting "old-timer's" disease.

[ 02-06-2004, 07:10 PM: Message edited by: Todd Bradshaw ]

[George Roberts]

cs ---

After seeing Todd's post, I will make few comments. Along the lines of different strokes for different folks:

With a canoe the strips should lay fair, all you need to do is knock the edges off.

A 1/3 sheet stiff sanding board with 100 grit paper should fair an outside in a few hours. Follow it with a 1/2 sheet foam covered sanding board with 150 grit for about an hour.

Use a finer cloth (2 to 4oz) as your last layer. Just lay it over your hull after you have squeeged. For most people it will wet its self out without any additional epoxy. A single fill coat and you can get on with sanding.

There are a lot of ways to get your work done. There are a lot of ways to mess up. Try to more of the former and less of the latter.

[cs]

Great information Todd! Went out today trying to find a flexable back-up pad for my 4-1/2" side grinder and couldn't find one, but I will and when I do I will practise with it before it touchs any boats.

Chad

[Daniel Wolf]

I'm new to this forum and really enjoying the exchanges.

This won't work on f-glass, but when working with wood an "auldie but guidie" can work very nicely to fair surfaces. It's called a slick chisel, it's usually 1-1/2 to 2-1/2 inches wide, and it has a long handle. The only ones I've seen have been quite old. I have one that is kind of on the short side but using it is like shaving a soft beard with an old straight razor, even with hardwood. You can get really fine control, even better than with a plane (and certainly better than with an electric plane or a sander), because the long handle allows you to make really tiny incremental changes in the angle of attack. The only downside is that you have to sharpen them really, really well to get such performance. With a slight sideways cut, you can cut a path so straight that it glistens.

There is an ode to slick chisels in the book _Tools of the Trade: The Art and Craft of Carpentry_. All you auld wood guys would appreciate it. I got my copy cheap at Amazon.com.

[cs]

Hey Jim, you might want to add this one to your FAQ. There is some good advice here.

BTW got to spend some quality time with my canoe this weekend and despite all the warnings about using the belt sander I'm quite satisfied with the way she is turning out.

Chad

[cs]

Wanted to add again that I'm using Doug Fir as opposed to cedar. There is quite a bit of difference in hardness between the two. Don't know if I would have tried the belt sander approch with a softer wood.

Chad

[Bill Perkins]

Sounds good Chad ,can't argue with success. If you want to check further before glassing I've found it helpful to turn the shop lights off ,leaving just a clamp light to light the hull alone .Then you can stand back and sight along the hull at different angles with its' profile highlighted against the dark shop background .You might pick up an off spot or two that will show when finished .

[cs]

Got a back-up pad and a sanding disk for my side grinder today and man does it cut scary fast. :eek: About afraid to use it on my canoe.

Chad

[Paul Scheuer]

Fear of scary cuts is a good thing. Practice where it don't count until you're comfortable. Sometimes there ain't no "un-doing".

[alteran]

I just finished fairing one. Ten minutes first with a paint scraper to take off glue bits and high edges. Then about five minutes with an orbital sander to take off a few more "plane catchers". Then I took about two hours with a very sharp, shallow set block plane going over the whole thing two times. Once in one direction and then the other at an angle to the strips. Then about an hour with an orbital sander with 80 grit.

And now there a few detail spots to touch up but I think with about an hour with the plane and sander and a little glue spot scrapeing I'll be done. A big help was misting it with water from a windex bottle to see what it will look like with epoxy on. Showed a lot of spots that needed cosmetics.

[brian.cunningham]

When I worked on this boat, we used epoxy fairing compound. We started off hand longboarding it, but had to give up and use power tools, one of which was a belt sander.

http://www.warrenmultihulls.com/images/W32lc.jpg
Even with this hard material, we needed to BE VERY CAREFUL with the belt sander.

A better tool for the job is a powered long board.

[ 02-10-2004, 02:39 AM: Message edited by: brian.cunningham ]

[cs]

Paul I will defintly practise with this before it touch anything of value.

The paper that came with the back up pad was 50 grit and they had nothing else at the store. When they get some more stock in I will try some 80 grit, but still I have never seen anything cut that fast.

Chad

[Popeye]

I can't stands it no more.

Take it outside in the daylight and have a look at your handy work, now let us pray.