F/FSport I
by david mitchell You can reach David Mitchellat 230 Walnut St. NW, Washington, District of Columbia 20012, or via e-mail at
davedge@me.com
n the process of building an RWD-4, I needed to come up with a pair of bent axles for the landing gear. I try to avoid music wire on F/F models as much as possible; it’s certainly strong, but it’s very heavy—especially in a gauge thick enough to look properly to scale! Bent aluminum tube is a relatively lightweight, viable op- tion, and I had just run across a promising thread on the Yahoo F/F listserve (www.
groups.yahoo.com/group/ffcookup/) that ex- plored ideas on how to bend soft metal tube without kinking or collapsing the bend. One idea was to fill the tube with fine sand or sugar, securely cap the ends, and carefully make your bend in the expectation that the compressed particulate will prevent the tube from collapsing. This can work pretty well, but I had concerns that, after all that, one hard landing could easily damage the axles. I wanted something better, a ma- terial possessing reasonable lightness, flexi- bility, and strength.
You’ve probably wanted that same thing at some point. Unobtanium? Nah. Just grab your handsaw and pruners and sneak over to your neighbor’s yard—you know, the guy who thought he would plant a little bamboo screen a few years back and whose house is now barely visible. Clip some fine and medi- um diameter green tips; while you’re at it, cut a few pieces from the heavier growth as well, and carry it back to the shop. You should also raid the pantry for some bamboo barbecue skewers, and by all means save those chopsticks that came with your carry-out. Whether green or dried, bamboo deserves a place in your arsenal of materi- als. When green, it can be bent quite easily; when dry, not quite so easily, but with care very satisfactory results are possible. All you need is a source of heat, water, and a bit of patience.
Your heat source could be nothing more than the barrel of a well-warmed, always-on soldering iron strapped to your workbench,
PHOTO: DAVE MITCHELL
Close up of the bamboo landing gear on the RWD-4 lightplane. Note the bend in the main axle piece, light scorching on the top of the bend. Joints are hit with thick CA and wrapped with thread.
or a MonoKote trim iron with a rounded foot set on high. For those of you who sold off your MonoKote irons when you swore off R/C and forever cast your lot with stick ’n tish, a satisfactory tool is easy to cobble up. A propane torch running inside a short piece of iron pipe of an appropriate diameter, clamped in a metalworking vice, provides a great indirect heat source.
I’m fortunate to own a guitar maker’s bend- ing iron, a plug-in device with a heavy alu- minum post and a rheostat that provides sev- eral radiuses and adjustable heat. Whatever your tool, secure it so it won’t move about, warm it up and let’s start experimenting. Note I said “experimenting”. Bending any
wood is a bit of an art, and bamboo is no ex- ception. In every instance, you need mois- ture in the wood to make it work. If the bam- boo is green, you’ve got some of your moisture built in to begin with. Green bam- boo is also easiest to bend, so if you’re new to heat-bending you might try it first. I recommend starting with some of the fine tips you cut. Gently passing the wood over the radius of the heat source while lightly bending the desired curve in will “bake” the curve into the material, so that you can form a piece of, say, 1⁄16-inch diame- ter bamboo into a splendid wing tip for an 18-inch model. Could it really be that easy? Well, no. Because the wood is green and
PHOTOS: DAVE MITCHELL
A bamboo skewer is chucked in a drill and run carefully through a hole (above) drilled in a piece of thin sheet metal. Note the two smaller holes to the right; the skewer will be run through these next until the desired diameter is reached. The RWD-4 (at right) strikes an epic pose. The ends of the tough bamboo struts have wrapped and glued wire pins, that insert into small lengths of tubing at the fuselage attachment points.
30 SEPTEMBER 2013
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