PHOTO: MIKE STUART
Partial bones shot of the King Air. Now that’s some nice building! Note the nacelles (above left), built in at the knock-off wing junction. Mike Isermann’s KO
Whoa big fella Lest you think magnet and pin knock-off systems are the stuff of small models only, take a look at Matt King’s 54-inch Comet Taylorcraft. A model as big as this presents its own set of challenges! In Matt’s words: “There are three magnets in the root rib of the wing and the rib in the fuselage. Two holes in the fuselage rib line up with two 1⁄16- inch pegs in the root rib. Also the lower spar fits into the fuselage rib. It’s worked well for me, but I fear windy days. The wings come off on a hard landing, but have done well on a gentle landings; I added one extra magnet setup just for good measure. It’s worked so far. I had considered rubber bands too. I think that I would be inclined to fly in a bit of wind if I had used the rubber bands.” Clearly, Matt is relying on the struts to keep the wings from folding up, so technical- ly no carbon fiber spar (such as that used by Mike Isermann) is required. I don’t have in- formation on how the struts are attached. It sounds like the momentum of the wings on a hard landing is too much for the magnets he used, though, so perhaps stronger magnets would do the trick?
Failing that, as Matt suggests, a pair of PHOTO: MIKE ISERMANN
PHOTO: MIKE ISERMANN
(knock-off) method on his Martlet. Note the rear dowel (above right), which keeps the wing alignment stable. Magnets are recessed into the root ribs.
suitably stiff rubber bands could be run through the fuselage between the two wing halves, attached at each end to hooks mounted into the root ribs of each wing half at the wing spar locations. Rubber bands would allow the wing a measure of shock ab- sorption, but would probably keep a given wing half from detaching entirely. Indeed, in a discussion on this general top- ic, Rich Weber noted the following: “The last time I tried this (a knock-off wing)
...the whole wing popped off in one piece. The first setup relied on the magnets and a positioning dow- el. After a bad landing where the wing popped off as it should have while the prop continued to spin and chop holes in it, I switched to us- ing a rubber band on a couple of internal hooks to keep it from going astray. It could still be easily disassembled, and it allowed the wing to slew around when it hit terra firma.” Makes sense, though as a dubious coun- terweight to this excellent, been-there- done-that observation, I will note that my own Miles Magister, which features just the sort of magnet-and-positioning-dowel- whole-wing pop-off arrangement that Rich describes, went into a very tall tree a few weeks back. The wing and fuselage separat-
ed completely on impact, and I have no doubt that this is the only thing that al- lowed both components to eventually wiggle down through the branches (assisted by a stiff breeze) for retrieval! Had there been a rubber band holding it all together, I’m cer- tain I’d be staring glumly into another bit- ter beer mug, and the trees would have had yet another prize.
Tip top tip
Speaking of rare earth magnets... Larry Kruse (oh yeah, remember him?) sent this in to me the other day. “This workbench tip may be old to readers, but it was new to me and worked great! If you have small screws that fit into tight places and don’t have a magnetic screw driver of the right size, sim- ply place a small rare earth magnet near the tip of the screw driver you are using. It will hold the screws in place nicely and can be re- moved and used again for future applica- tions.” Thanks Larry!
In closing, I’d like to wish everyone a hap- py, healthy and fulfilling holiday season. Recognize your blessings, help those less fortunate where you can, and remember: it’s the people in your life that count!
A finish shot of Mike Isermann’s pretty Martlet. Note the clean wing joint (at left). Weathering and details like the landing lights and nifty prop hub are Isermann trademarks. Matt King’s big ol’ Comet Taylorcraft. At 54-inch wing span (above), Matt thinks he might have pushed the useful limit of using magnets for knock-off wing assemblies.
FLYING MODELS 53
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