The sanding block microcosm

General Discussion
1

Dear Sirs,

Please advise me on the following matter:

Such a simple instrument, but given the millions of collective hours
using these things, I bet some Sway brothers out there have some significant design nuances to share about these things. You know, work smarter instead of harder? If it has already been addressed please provide the link.

We beat the crap out of planers, plane shapes, concaves, rockers, densities, etc.  Sanding blocks sound benign, but how many sanding strokes did you make on your last non-computer 6’8"?  500, 1000, 1500? Assuming the cleanest planer work possible, where could efficiencies be gained? Different grits, block dimensions, lighter block material like hollow titanium (ha ha!)? What is optimal? What is your process? Given 1000 revolutions, reduce the sanding block weight by 2ozs and your sanding effort is reduced by 125 lbs- and that is a crude calculation that doesn’t account for all of the complicated physics.

It seemed a simple enough task to go out in the garage and make a couple sanding blocks today until I started thinking about this stuff. I have several strips of 4" x 1/2" x 4’ oak that were previously employed as the ‘skis’ for an old Nordic Track excerciser. They are very straight and don’t require too much truing but I started to think about how heavy white oak is and how much energy it takes to move it back and forth. I intended to make a 22" deck domer (poaching Bud’s design), a 10" block for vees, and possibly one for concaves- all for polyurethane foam.

In the past I have used wood glue to adhere the sandpaper to the blocks. It works well but does not remove easily when the paper wears out. It would be nice to replace the paper instead of having to true up new wood blocks. What is a good adhesive that will allow replacing the sandpaper? Super 77?

What about grits? I was thinking of 80 for a deck domer and maybe 100 or 120 for the 10" block.

This is a seemingly simple matter, but somewhere, some place, there are
some Aipas, Arakawas, Rawsons, or the likes, that have something interesting to say
about this.

 

 

 

2

I have a piece of balsa from a hobby shop. I think its about 12" long, 3" wide, 1" thick. works great. Just wrap a piece of sand paper around it. Very light so you can feel the paper “bite” into the foam, or lap when I sand the free lap.

 

 

 

3

[img_assist|nid=1057812|title=|desc=|link=none|align=left|width=640|height=480][img_assist|nid=1057813|title=|desc=|link=none|align=left|width=640|height=480]

The top one is a piece of plywood with some foam and cloth glued to it,  a great pad for glassed rails.  I also put some 220 on it to do the final sanding on the foam in the flats before glassing.  The other two are from an Automotive Paint store.  A sanding pad works to hand sand a concave.

Fiberglass Hawaii sells a specific adhesive for sanding pads.  Squirt bottle, never hardens,  easy on and off.

4

I always tell people your block should be as wide as you can go and still fit your hand comfortably, and just shorter than the sheet of paper, so no corners stick out. Everybody’s hands are different, so there’s no one perfect size. You want to maximize the cutting area, so go as wide as you can and still have good contol, but don’t have to put a death grip on the block. I have a peice of oak tread material (I like a heavy block…knocks down the bumps faster and keeps the block from bouncing around… balsa no good for me) I cut to fit my hand. One side is hard, the other has multiple layers of life jacket foam glued onto it with 5200. Just enough resistance, and just enough give. When they get flat, I tear them off and glue on more. But that takes years. The edges of the hard side are slightly rounded, and the edges of the foam are cut to make a slight bevel so the paper wraps around smoothly. I don’t use adhesive. I have one block, so I just flip the block and keep using the same paper. I have a few different sized/shaped blocks for different jobs, and I use grits from 36 all the way down to 100 for shaping… higher for finish shaping for resin tints. I’m not interested in a deck domer, because my decks are all different, depending on rail shape and thickness. I never used to use a long flat block (more like a fairing board) for flattening bottoms, but I tried one recently and liked it. Just gotta be careful you don’t put more pressure on one side than the other, and don’t let it rock across the stringer.

Greenlight Brian is making all kinds of cool new blocks and hand tools specifically for shaping EPS. They’ll be out soon…

5

I often used blocks of old board foam with one side laminated. Depending how thick the foam, how long, how wide, and how many layers of cloth, it stiffened and controlled the flex, and build a few for different grits.

Laminate them on a flat reference, vac is good. If a block is not accurately flat it's hard to expect it to do a good job flattening bumps on a lump of foam.

Really effective, accurate, cheap, and you can make as many as you need.

6

I used to make my sanding blocks out of really hard/heavy woods, but found it was not neccesary, noy I used mostly EPS cut offs for my flat blocks and Balsa for concave/contour blocks. Velzy gave me one of his blocks, Oak with leather glued to it and # 24 on top of that, too heavy and unless you are in the early rough out part of the shape, it scratch’s the crap out of the blank and makes more work than needed.

I prefer, really worn out #36 for rough sand, #40, but some worn out #40 to clean up and go right to worn #100 screen for finish and really clean planer work is a plus for not so much elbow grease

7

Virtually all the kneeboards that I have built since 1969 have had concave “wells” for the knees and the lower legs (plus “thumb grip” rails–see attached pics from ~1970).  I found it to be difficult, time-consuming, and frustrating to shape and sand these features. Here’s a description of the process that I discovered works the best for me.

To form the knee/leg wells, I draw the outline of the wells on the top of the deck foam, then rough out the hollows using a 4" Makita sander-grinder with coarse sandpaper (or even a grinding wheel). I control the depth of each “cut” into the foam by the grider/sander by laying the board on the ground, then straddling it, and bending over at the waist (arms extended). At the same time, I’m controlling the angle of inclination of the grider-sander (to control the depth to width ratio of the cut), and moving my arms (primarily pivoting at the shoulders) along the desired path of the cut. On long hollows, one may find it best to reposition one’s feet along the length of the board a few times. I do multiple passes (usually only takes a couple), decreasing the amount of material removed as the edge of the cut approches the desired (i.e. marked) width.

After this rough shaping, the hollows will generally have some (hopefully small) ridges and dips and somewhat resemble the surface of a machine shaped blank. These artifacts of the process are removed by sanding. What I have found works best for me to smooth out these corrugations is to take a scrap block of foam and (approximately) shape it to into a convex, three-dimensional sanding block that is a rough approximation of a mate to the desired hollow (Note: sharp edges, if present, are rounded off). The foam sanding block itself is then used to sand the hollow to the desired final shape and smoothness.

During the sanding process both the foam in the hollows being sanded and the foam of the sanding block are being removed. If/when the sanding block becomes too worn I just take a new piece of scrap foam and shape a new sanding block (the worn sanding block may serve as a finish sander).

** Note 1:  I have not tried this techinque on EPS or XPS, but I would guess that this method will not work as well (if at all)  compared with urethane foam.

** Note 2:  An alternative to a foam sanding block may be to coat a spherical body (e.g. a ball) with coarse/fine sand (resin the ball…sprinkle dry sand on it…dump excess sand off… wait till resin cures before using).

 

728×546 79.3 KB

196×600 22.1 KB

8

Plenty of interesting responses while Ive been sick and away from the computer. I guess everybody and their dog is sick right now- the entire cold/flu/sinus section at CVS was down to about 10% of normal stock!

So, turns out a bunch of you guys had some interesting input. Thanks to everyone for their responses.

mtb- It looks like you really have to go through some foam to make those kneewells. I am not taking away foam to necessitate a grinder but I like your foam sanding block suggestion. By the way, why did you scoop out the nose as well? Looks like you put a leash on the nose as well- how’d that work? Wildy- I dig your angle on changing flex with lamination thickness.

Jim & Pico- I suspected balsa might be worth looking into- going to try that for sure now.

NJ- 5200? I only know of 3M 5200- expensive caulk that cures underwater. Is that what you are referring to?

I was surprised you guys are going down to 36 grit. I don’t think Ive have ever gone below 80 grit. That will definitely save some time in the early stages.

 

 

9

i use shapers foam blocks in medium and soft. i might invest in a hard shortly. they are velcro backed for swapping paper grits and changing when they wear out. i use these for shaping and far sanding my rails.

10

i use shapers foam blocks in medium and soft. i might invest in a hard shortly. they are velcro backed for swapping paper grits and changing when they wear out. i use these for shaping and far sanding my rails. http://www.shapers.com.au/categories/Surfboard-Shaping-Tools/Shaping-Blocks/

11

I picked up a tool-making disease from my time working with Jim P, so I (sometimes compulsively) fabricate all my own ''blocks''. Most of them are flexible to some degree. I almost always glue a single surface of the tool with paper, anytime you wrap paper around a block it can't flex without wrinkling the paper.

Good paper is important. For my 36 grit work, I like a 3M adhesive backed auto/marine product. Sorry I don't know the part #, I just steal a few pieces from my boatbuilder friends. (I glue it with PU anyway, the adhesive is for temporary stick only. On foam the grit lasts far longer than the supplied adhesive.) For 40 grit and up, the Indasa brand Rhynalox paper is the best I've ever seen.

12

 

Most of the foam in the nose is scooped out to diminish the forward buoyancy and enhance duck-diving capability.

The forward attachment point of the leash minimizes the length of leash in contact with the water, and hence drag, when paddling and when riding on a wave. It also minimizes the pull on the leash and rider when the rider and board have parted ways (e.g. after bailing/wiping out) by aligning the board with the flow past it so as to streamline the board (vs fighting the fin/board drag as the board veers from side-to-side) when there is a pull on the leash.

There are some obvious disadvantages that one needs to consider. One is to not allow the leash to go over a rail and across the bottom of the board (esp when catching a wave) as that causes substantial drag and it is difficult to correct once it occurs. I avoid that by holding the leash captive between my left thumb and the left thumb grip channel during a take-off. Another drawback is that since a pull on the leash streamlines the board, the closure rate between the board and the rider doesn’t lose speed as quickly as would be the case if the leash were attached at the back of the board. Hence the board can be traveling faster back toward you if the leash has been stretched out after a wipe-out etc. That’s rare, but it has happend to me a couple of times since I first began using a leash attached to the nose of my boards (~ 1970 or 71). Both times the only consequence was a bruise on my forearm(s) where the board impacted.

 

13

old thread i know. just wondering how you guys feel about the ezshapepad. i know foamez is on sways. looks like a solid product. just getting opinions. probably goin to buy this within the next couple days.

http://www.foamez.com/ez-shaping-pad-combo-p-861.html

14

Don’t even hesitate.     I have and use both.   Very user friendly.   Get a full range of grits.

15

I agree with Bill, those are good pads for those who don’t care to make their own… also this is a nice thread for those who didn’t read it the first time around, and includes good stuff from Terry/MTB (RIP).