Sanding rounded corners?

[Zach]

Hi guys.

I'm befuddled as to power tools to do the corners of the cockpit, and along the sides of the deck at the cabin top and inside curve of the toe rail. The diameter of my sander is larger than the radius of the corners... and my little mouse palm sander doesn't bite rounded corners. Hmm...

Any suggestions?

Zach

[Tim]

I always do those inside corners by hand. Tape up your fingertips and get ready for a good time.

[CharlieJ]

lol- Zach- I must have 15 different sanders around the shop, but like Tim, I always wind up hand sanding those corners.

One thing you might try to help a bit- get yourself a computer mouse pad and cut some sanding blocks from that. Make it so a 1/4 sheet will wrap around so you can hold the edges. Then go to it.

I've also used chunks of radiator hose, chunks of plastic drain hose, whatever had the correct radius.

But in some places, the old fingers wind up being the tool of choice.

[Rachel]

I've seen carpenters use little scrap bits of those -- well I'm not sure what you call them, but when you take a board of about 2" x 2" and rabbet it for two end-grain pieces of wood to meet at a corner and then have a rounded edge on it at the outside of the corner -- corner boards?

Anyway, a 6" or so offcut of one of those makes a nice little corner sanding block for some spots.

R.

[Noah]

The Fein multimaster is really nice for these areas - either with the detail sanding kit, or creating your own custom sanding pad to fit a specific area if you have a lot of it to sand.

[Zach]

I was afraid of that... (Grin)

Reminds me of a summer spent in a machine shop polishing dies... Emory cloth and a fingertip. Coulda robbed a bank, no fingerprints!

Thanks for the tips guys. That multimaster calls my name every time I'm at woodcraft, but the price is just to much.

May have to borrow an ultrasonic polisher from work... hmm. <Cues Flight of the bumblebees>

Zach

[Hirilondë]

I've seen carpenters use little scrap bits of those -- well I'm not sure what you call them, but when you take a board of about 2" x 2" and rabbet it for two end-grain pieces of wood to meet at a corner and then have a rounded edge on it at the outside of the corner -- corner boards?

Anyway, a 6" or so offcut of one of those makes a nice little corner sanding block for some spots.

R.

The one on the left is cherry and covered with sandpaper. It is the left over from a cabinet job. The one on the right is for the nav station cabinet I am building now. Yes Rachel, they do make great corner sanding blocks. I don't know what they are called either, corner board works.

[Rachel]

That's them! Thanks for the photo-illustration.

Rachel

[Zach]

Saw this the other day on west systems website, wonder how it'd work on toe rails and the like.

Contoured sanding pads
G/5 also works great for creating contoured sanding pads. A molded-to-shape sanding pad can be helpful when you need to sand lots of identical wood molding. You can make contoured sanding pads by laminating with lightweight fiberglass or cotton fabric and G/5 epoxy. To do this, prepare a section of molding from which you want to pull an image by covering it with 2" wide shiny cellophane tape. The tape acts as a mold release, allowing removal of the sanding pad after the epoxy cures. As described above, apply multiple layers of fabric and epoxy to create a stiff sanding pad. Remove the molded sanding block by forcing wood wedges between the plastic tape and the epoxy.








To use the sanding block, hold the sandpaper in position with two-sided tape or with feathering disk adhesive. For greater comfort, attach a wood handle to the back of the sanding tool with G/5 Adhesive.

[Zach]

I'm pondering the curves... wonder if a real curved part of the toe rail was molded, and cut off the overhang to the outside with the exception of a finger in the middle so it could pivot, yet still be trapped up tight.

Used to use a strip of rubber from one of those orthopedic mats warpped in sandpaper for working curves on cars, where a rubber block wouldn't go, and fingers would groove.



You know... This boat is consuming way to much space in my brain...

[bcooke]

Before you know it the boat will be saying, why do I still keep this person in here with me?...

[Tim]

All the complex ideas on creating custom sanding blocks are great and all, and make good sense in some situations. But almost never in the situation you're actually in, it seems.

On these little, basic boats, by the time you fool around with conceiving, building, and perfecting a little block or other potentially labor-saving device, you could have had the whole job done by just doing it. Nothing will make sanding tight inside corners much easier, unfortunately. No tool can as effectively get into a 90° (or similar) corner as can a few human digits.

It takes me about an hour per side to hand-sand (to bare gelcoat) the tight coves and related areas at the base of a Triton (or similar) molded rubrail--say 2-3 hours total. It's not a fun or pain-free few hours, but it's quick. Work takes work, after all. Doing all the cockpit corners and curves takes about the same amount of time, overall. The cockpit's less fun than the toerails, but what can you do. It's the nature of the beast.

Some things just aren't worth trying to simplify because they're already simple. Don't lose sight of the simple approach: it's the key to getting through these projects successfully. Save the thought and complexity for where it's needed (and there are plenty of such opportunities).

[CharlieJ]

What Tim said.

Building molded sanding blacks is great IF you are in production- for "one-of" work, by the time you conceive the block and build it, you could probably be done with the sanding.

It's not a fun job, but if you just bite the bullet and DO it, you get it done fairly quickly.

[Zach]

I'm bad about over thinking things, its only compounded by being four hours away from the boat too. (Big grin)

Thanks for your thoughts guys.

Zach

[feetup]

Hey, an Ipod with a selection of tunes at about 120 beats per min really helps with sanding, and you won't even be distracted by the onlookers sayng "Sanding huh?"
Just got to remember NOT to sing the harmony parts too loud!

Feetup

[Summersdawn]

Hey, an Ipod with a selection of tunes at about 120 beats per min really helps with sanding, and you won't even be distracted by the onlookers sayng "Sanding huh?"
Just got to remember NOT to sing the harmony parts too loud!

Feetup

Best sanding advice I've ever read ;-)

[feetup]

I'm going to post another one of my hard to read, nerdy, "How To" posts on this. Take it or leave it.

For inside corners, or for all that matter for any compound curvature, such as fairing out the jaws of a chock or fairlead, or for complex compound curved joinery there is a trick that tool and die makers use that is one of my favourite techniques.

Get a roll of abrasive tape in the grit you choose, or perhaps one grit finer since the stuff is pretty aggressive. About 1" wide seems to work best although I buy it in 2" rolls and rip off whatever width I need. Don't go cheap, it never pays. I find that the 3M Gold is about the best, although other brand's best will be fine.
Rip off about 12 to 14 inches X 1" wide and drag it, abrasive side up over a sharp, hard edge, like a counter top (I use my table saw) a couple of strokes end to end, starting at each end. This will soften the cloth, and open the grit to help prevent clogging. This is a first step with any sand paper.
Now, if you have thumbs like a brick layer you can dispense with this part. Wrap your left thumb (if you are right handed) with 5 or 6 layers of masking tape and squeeze it in tight till you get a ball of tape. Finish off the last wrap over your thumbnail.
Now, holding the abrasive tape between the thumb and first knuckle of your right hand (You south paws are used to reversing directions, I'm sure) lay it over the area to be sanded so that the knuckle of you index finger is right at the edge of the area to be sanded. Place the taped up thumb on top of the tape (gritty side down) and pull the tape out from under your thumb, long wise, while at the same time sliding your thumb along the area you are sanding. You don't need too much pressure on the thumb, but if you really want to dig in you can push a bit. If you leave the thumb stationary you will put a finger groove in the work, and this is sometimes good if you want to remove a lot of material, moving the thumb around for each pull of the tape, puting a lot of closely spaced grooves, then smoothing those out later.
At first it is a bit slow and awkward, but after a while you get a rhythm going and actually throw the tape back across the work area and trap it with the other thumb all in one move.
The trick is in the movement of the taped thumb, and in pulling the tape from different directions to fair everything out.
Stop every few strokes to feel the area with your finger tips. You can feel things you can't even see, if you concentrate on your finger tips. I often close my eyes and run a flat hand over the work, feeling for highs and lows, and when I find a high, I stop and mark it with a pencil, and then sand away just the pencil marks, then feel again.
I wish I could post a video of this but it's really simple, just a bit hard to explain. Kind of like explaining a dance move in print.
There is also the old "shoe shine" technique for outside curves, but I'm sure everyone knows that.
I know I come up with these long winded posts from time to time, and I often imagine the "deer in the headlights" look that readers will get, but I have spent over 35 years on or about the shop floor, working with some real fine old world craftsmen, hence I picked up some of these little gems almost by osmosis, and some of them I never see any one else use and wonder why they do things the hard way.
I certainly don't mean to test your patience.

Feetup.

[Ancient Race]

I know I come up with these long winded posts from time to time, and I often imagine the "deer in the headlights" look that readers will get, but I have spent over 35 years on or about the shop floor, working with some real fine old world craftsmen, hence I picked up some of these little gems almost by osmosis, and some of them I never see any one else use and wonder why they do things the hard way.
I certainly don't mean to test your patience.

Fear not; I'd venture you don't try many of the souls that hang here. I think most of us are aware that the tenets of craftsmanship take years to obtain: the wisdom you impart are not only appreciated, but recognized as a gift of time and experience.

So another great technique. Thanks! At least on my part.

Greg

[Rachel]

Oh, absolutely - this is cool! Thanks for taking the trouble to write it down, feetup.

I think I can visualize what you're talking about - it sounds something like what you do with scissors and a bit of ribbon, to make it curl. But let me check to see if I have it: So you trap the end of a "ribbon" of sandpaper between the wrapped left thumb and the work, with the free end hanging out the "back," away from you. With right thumb-and-forefinger, you pull the sandpaper (this is the part I'm not sure about) from the base to the end of the wrapped thumb (i.e. "sideways), all the while moving the wrapped thumb (and the whole works) towards you..?

Even if I don't use this part tomorrow, just the "breaking and softening the sandpaper" part will be useful right away.

Thanks!

(A YouTube video would be great for this, wouldn't it.)

[feetup]

Yes Rachel, the ribbon/scissors analogy is the best one yet. I wish I had thought of that. The "backing " thumb, (I think that would be a good name for it) can move in any direction, although it is much easier if you move it along the length of the tape, since it is harder to make the tape stay under your thumb when moving it transversely. I tend to move the backing thumb away from the other hand, but that is just me. Kind of a rubbing stomach,tapping head thing. You can even make the thumb move in small circles. The trick is, and I see that is not well explained in the other post, is the thumb only moves a small amount for each stroke or pull of the tape, maybe an inch or so, two at the most, and if you are sanding a corner that has 3" of surface you would cover it in say 5 overlapping pulls. It helps to anchor your left hand to the work with your index finger or the heal if the hand, whatever works and gives you some flexibility. Also the direction you pull from should vary, if you have the room for your elbows, and if your body will work that way for you. When the stroke is done you kind of "throw" the tape back into place and trap it with the backing thumb and pull again, all with a bit of rhythm. A bit of Ziggy Marley or Fleetwood Mac helps here.
Actually, thinking of ribbons, that would be a good way to teach the technique to those neurons responsible for such things.

As far as the "Breaking" of sandpaper goes, if you pull the paper over the edge (so that it wraps down at 45 degrees or better) from each of the four sides, then diagonally from the corners, it will be very flexible and easy to wrap around any sanding block, and it will last longer, cut more evenly with more even "scratches" and clog way less.
Funny how something as mundane as sanding has so many tricks to doing it right. The other day I was mixing a batch of epoxy and silica and wondering what the "correct" way to do it was, and how long it was going to take me to stumble across a better way, without fighting the lumps or the stuff becoming airborne. I even thought of asking Tim, but decided he surely must have better things to do than discuss mixing in thickeners.

Feetup

[Rachel]

... and how long it was going to take me to stumble across a better way, without fighting the lumps or the stuff becoming airborne.

The last few times I mixed up some thickened epoxy I had the "lumpy thickener" problem. What a pain! Do people "mash it up" ahead of time? Even though it's so fly-away? I'd never had this problem before, but then I've never lived in such a den of humidity either - maybe that's part of the problem.

[Tim]

The other day I was mixing a batch of epoxy and silica and wondering what the "correct" way to do it was, and how long it was going to take me to stumble across a better way, without fighting the lumps or the stuff becoming airborne.

Mix, mix, mix. Eventually you'll develop the Popeye-like arm required for the proper mixing pressure. It helps to "fold" the lighter thickeners into the resin; pull the resin up from the bottom of the pot with the mixer and sort of force it over the thickener, and repeat.

No one ever said it was "easy" to properly mix thickeners into epoxy resin, but it's not hard either: experience just points you to how much to mix in, how long to mix, and how smooth it should be. Yes, the stuff flies about the air terribly, particularly cabosil. Wear a mask. I hate everything about cabosil (except for its effect on epoxy resin), but it's just one of those things.

It doesn't take long to mix a pot of thickened epoxy, but it does take an appropriate mixing effort to get these lightweight, fluffy materials to properly incorporate. If there were an easy way, what fun would it be? Clumps of microballoons are commonplace, but don't stand up to proper mixing at all, so they shouldn't be an issue. Get some real stir sticks for larger batches; small stir sticks are (well) too small a lot of the time.

Not every process has a shortcut or "tip" to make it suddenly a cinch, though few processes, at their core, are actually that difficult. I sure don't have any mixing "tips" other than to just say "mix it"; if you do it, the experience will come, and only the experience makes any process easier, tip or no tip. I know how to do it without issue, but I wouldn't know how to explain it to someone else in any other way.

[Rachel]

I've never had much problem mixing fillers before (and I never touch Cabosil without wearing a mask), so I was just curious if people in humid areas pre-mashed it or something (i.e. before adding it to the epoxy). I was probably rushing it a bit because it seemed so hot out for epoxy work (of course I'm from Northern Minnesota, so it seems hot out for everything here). Next time I'll mix more.

The other difference from what I'm used to was that the Cabosil was pre-mixed with something else (it seemed "cotton-ey") that I'm not used to working with.

In this case it was no big deal, because I was just mixing up the initial thick stuff to fill an abandoned through-hull hole, before I got down to the business of actually grinding and fiberglassing it.

I'll work on my Popeye arm ;)

R.

[Zach]

Thanks for taking the time to teach us Feetup. Excellent explanation and examples, I love that kind of stuff.

Reminds me of when I was working polishing dies, we would take a 1 inch roll of fine emory cloth and spend a few days working the inside of a tool to a mirror. First you'd tear it the strip in half in half, fold it over on its self width wise and slip it through the die, and run it back and forth in the direction of the flow. Tearing it down it down to an 1/8th of an inch would work inside some incredibly tight spaced. Abrasive cords cut faster... which on tight radius details is a bad thing... even on tool steel. Wrap both thumbs, or index fingers and pinch down and run it back and forth parallel to surface you are polishing, and to the direction of flow. Pressure angled up or down from parallel would put a radius at the intersection of the internal geometry and the surface ground face where the face plate bolted on. With the radius, molten plastic would get stuck and overheat. Those little brown and black specs in a white PVC pipe happen because of that... (Haven't thought about doing that in a long while!)

I'll have to order a roll of emory cloth to take down to the boat and give this a try! Thanks Feetup.

[Peter]

Colloidal silica ... interesting stuff that's not good to breath, but apparently it's a common ingredient in ketchup, shampoo, cake mixes, and as a filler in medical pills. Makes one want to start reading the ingredients list on the food we buy!

[feetup]

I can see this thread is becoming a ramble.
The company I work for does a fair bit of contracting to a pulp mill way up on the North end of Vancouver Island. Beautiful place, but the mill was origionally built in 1913-18. Much of the equipment there is of that vintage, and the entire mill is old and crumbling. They make a special pulp that is used to make explosives and the fibre additive that is in everything from apple pie filling to the special fibre suppliments people take to keep them healthy. Your eyes run and your throat hurts when you are at the mill site, and they seem to have an evacuation for some dangerous spill every week or less, but they make a product that is in almost every prepaired food.
Kind of makes you think.

Feetup

[Onrust1368]

One trick I've used to sand concave areas is to get a big sponge and hold a piece of drywall screen on it - various grits are available down to about 220 or so - it worked well, I thought -

[Hirilondë]

One trick I've used to sand concave areas is to get a big sponge and hold a piece of drywall screen on it - various grits are available down to about 220 or so - it worked well, I thought -

Hmmm, I bet it does. Going to try this. We are now using lots of screen sanding discs on our dustless systems. They work better than holes for dust collecting and sand well on bottom paint and fiberglass. I never tried using them for hand sanding.