REALLY SUPER SANDER
Bob Kopski
The ubiquitous #11 knife and sandpaper are no doubt the most-used tools in an aeromodeler's shop. While the former tool is singular in nature, the latter can take many forms. Anything from a simple piece of hand-held sandpaper to dedicated-shape sanding blocks are common model-building items. Many are available readymade in the hobby marketplace, but often the modeler will make his own.
Just as there are many possible block shapes, there are also several choices of the sandpaper attached to those blocks. These choices include economy grades through more costly materials. Generally, the lowest-cost sanding material is simply not worth using. I normally use various "cabinet" grade papers that cut well and wear well. Tungsten-carbide sanding material is the best I've used.
Of all possible dedicated sander shapes, the most commonly used sanding tool is the simple rectangular sanding block. Classically, this is a convenient-sized handheld wooden block with sandpaper attached.
In recent years a commercial product has been introduced that mimics this classic tool and improves on it. The Products 2000 Inc. Sup-R Sander is really a system of interchangeable tungsten-carbide sanding cartridges and a mating holder. The company also sells a wire cleaning brush.
My Really Super Sander is an adaptation of the Sup-R Sander.
To use the Sup-R Sander, a modeler chooses one of three color-coded cartridges to work with: fine (blue), medium (yellow) and coarse (red). The curved plastic handle is snapped to the chosen cartridge. This results in a comfortable sanding block having a flat sanding surface measuring about 2 5/8 x 5 1/8 inches. The very hard, sharp tungsten-carbide sanding surface makes swift work of all modeling applications I've tried it on, and it never seems to wear out. At most, the sanding surface may become "loaded" with wood dust and reduce the tool's effectiveness. This is easily fixed by scrubbing the sanding surface with the companion wire brush, which digs in and removes the clogging wood dust. Such treatment makes the cartridge good as new.
I found that one interchangeable handle was not enough. Normally I use at least two grades (medium and fine) routinely, and in that order. Switching the handle is easy, but quickly got annoying, so I got another handle.
Even so, something still was missing. I make my own wooden sanding blocks — two-sided blocks with different grits on each side. A simple flip-in-the-hand takes care of a grade transition. There's a block taking up space on the bench I missed when using the Sup-R Sander.
With the Sup-R Sander used as supplied, I noticed a disappointment: the cartridges have excellent sanding material, but the plastic body of the cartridge itself could easily deform during use and produce disappointing results. For example, I often make formers from Lite-Ply birch plywood and usually need to sand four edges straight and smooth beyond saw cuts. Normally I just run two grades on the sides of a normal wooden sanding block diagonally across the edges and a good solid flat sanding block will easily straighten and smooth a wavy saw-cut edge. With the Sup-R Sander used, the resulting former edges bowed out because the plastic cartridge surface yields under applied pressure and becomes slightly concave. The stiffer outside edges of the cartridge tend to cut the work first; the softer middle of the cartridge sands last. The cartridge deforms slightly and becomes a sanding dish. Thus the plywood former edge winds up slightly rounded outward in the middle.
The solution to these problems was a double-sided sanding block made of two Sup-R Sander cartridges assembled back-to-back with internal filler material. The filler makes the end item block-like and unyielding in its flatness. The tool positively makes straight former edges — and straight-and-flat everything else too. It worked well. I made two Really Super Sanders: a medium/fine-grit combination and a coarse/medium combination. Both work well; the medium gets the most use in the shop.
Materials
- Two Sup-R Sander cartridges (choose the two grits you want)
- Modeling knife
- Turpentine-based paint thinner or lacquer/dope thinner
- Wire cleaning brush (optional)
- Gap-filling cyanoacrylate (CyA) glue
- Soft balsa strips, nominally 1/4 x 7/16"
- 120-grit sandpaper
- Small sanding block or flat surface for sanding the balsa strips
Making a Really Super Sander — step-by-step
- Select the two cartridge types you want to mate up.
- Remove the product label inside both cartridges.
- Use a modeling knife to lift the edge of the label and pull it out.
- The durable outer label surface will probably peel away leaving a fuzzy paper layer stuck inside the cartridge.
- Moisten the stubborn label residue with turpentine-based paint thinner, lacquer/dope thinner, or similar and let it soak a few minutes; the label will lift right off.
- Keep thinner away from the sanding surface — it might loosen the sanding sheet from the plastic.
- Blot the paint thinner and wash the inside surfaces of the cartridges. Get all the thinner washed off, then blot and dry the cartridges.
- Prepare the balsa filler strips.
- Cut three balsa strips for each cartridge (six strips total).
- Choose soft 1/4" balsa and cut the six strips 1/16" wide.
- Cut the length to just easily fit lengthwise inside the cartridge (my strips are 5 1/8" long).
- Cut two clearance notches about 3/32" wide and 1/4" deep in each stick to clear the cartridge cross-ridges. Make sure these notches allow the sticks to completely touch the inside bottom surface of the cartridge.
- Optionally, lightly scuff the inside surfaces of the cartridges with a wire brush.
- Glue the balsa strips into the cartridges.
- Place the cartridges sanding face down on a flat work surface.
- Glue the sticks evenly spaced to the cartridge bottoms using gap-filling CyA glue, pressing all sticks flat against the plastic floor.
- Make sure the sticks are spaced about the same in each cartridge since, when assembled back-to-back, the sticks will be held in contact.
- Trim the balsa strips flush with the cartridge perimeter.
- When the glue is dry, confirm all sticks are in full contact and well adhered.
- Note that the 7/16" stick height allows each balsa piece to rise slightly above the plastic border of the cartridge.
- Place the cartridge sanding surface up, sticks down, on a sheet of ordinary 120-grit sandpaper.
- Sand the sticks flush with the plastic cartridge perimeter wall. Do not press down on the middle of the cartridge; hold the cartridge near the edges and apply uniform light pressure while moving the block on the sandpaper. Sand down to the plastic edges, taking care not to significantly sand the plastic.
- Assemble the two cartridges back-to-back.
- Trial-fit the two cartridges and verify a good fit with the two cartridge plastic perimeters in full contact.
- If the fit is OK, apply gap-filling CyA to the balsa strips on one cartridge and bring the other cartridge into contact, quickly aligning all outside edges.
- Press together lightly and let the CyA set up.
- Note: do not use CyA on the plastic perimeters—only on the balsa strips.
At this point you should have your own Really Super Sander: an easy-to-hold, easy-to-use, durable, double-sided sanding block that does not yield under pressure. Former edges, and everything else, will sand straight and flat!
Here's hoping you enjoy using the Really Super Sander as much as I do.
— Bob Kopski 25 West End Dr. Lansdale, PA 19446
Transcribed from original scans by AI. Minor OCR errors may remain.
