A Very Magnetic Tiger Moth


A clear acetate “wing” that keeps stab from vibrating (above left). A carbon fiber rod projects forward and hooks under the horizontal stab; the rudder hinge is reinforced with Blenderm tape, and the trimmed Robart


tached to fishing tackle barrel swivels which are attached to soft aluminum ¹⁄₃₂- inch open ended hooks, that go through the rear cabane struts and are wrapped around their own super magnets which are stacked underneath the main wing hold down magnet. To take off the wing, these magnets are slid to each side, which puts slack in the flying wires, and unhooked from the barrel swivels on the flying wires. Presto! The wings can be removed by care- fully popping them off of their super mag- nets and sliding them forward or backward off the fuselage.


Step by step modifications 1. Cabane struts: Sand down the ply nibs


on the cabane struts (the top ones that key the upper wing into place). You want to re- duce them in vertical size by about 50% and round them off. The idea is to let them locate the wing properly, but we want the wing to come on and off easily, even when attached. 2. Mount the cabane struts to the fuse-


lage. Dry mount them down into their slots until you feel them bottom out, and then check to make sure they line up with each other and are of equal height, measuring from the squared fuselage bottom. To make these ply pieces seat properly in


the fuselage, sand the ends and push them in and out with trial fits until they obvious-


micro hinge that projects into a socket on the tail end of the fuselage. Vertical and horizontal stabilizer assembled (above right). Note the carbon fiber rod that holds the assembly tight.


ly seat as designed. Set the square bottomed fuselage onto your building board and se- cure with blue tape or sewing needles through the foam and then measure to make sure both struts are at the same height at their backs and at their fronts. Do not attach with epoxy, as instructed,


but use canopy glue on the ends of the struts. My first successful R/C trainer, using modern radios, was Dave Thornburg’s L’il Gypsy, which had its wing perched up high with cabane struts attaching it to the cabin. I will conservatively estimate I re-glued and reinforced the cabane stuts fifty times. And although attached by rubber bands, the wing rarely separated in a crash and the struts were always splintering. By attaching the Tiggie’s cabane struts


with canopy glue, you can pull them apart if you have to rebuild them, without taking out their fuselage attachment points, which are hidden inside the fuselage and not easi- ly accessible. 3. Balsa wing supports: Use two pieces of medium hard balsa, approximately 3


⁄16 -inch


thick, to bridge between the cabane struts at their fronts and their backs. Then sand the underneath of the rear piece until it is ap- proximately 1⁄8-inch thick. These will act as a wing support and will be the home to three super magnets. Don’t install the magnets, yet. Use quick setting (5-minute) epoxy to


attach the cabane struts to these bridging pieces. Eyeball things as they start to set up and make any adjustments necessary to keep them square. 4. Mock up the wings on the airframe. We


are about to use the airframe as a wing jig. Use blue painter’s masking tape to keep the wings in place, top and bottom, at their fuselage and cabane strut attachment points. (The blue tape is low tack and less likely to pull paint off of the finished parts. It is also a good idea to further reduce its tack by sticking and unsticking it against your pants or shirt sleeve several times be- fore using it.) Clean the areas around the wing strut assemblies lightly with Windex (alcohol will remove the finish). That is where we will be gluing the whole kit and kaboodle together. Cut out the bottom wing’s strut locating


holes, where the strut nibs will be inserted. Meaning cut through with a sharp tipped ra- zor knife. Put the wing struts in place. Turn the airplane over and put canopy glue on the strut nibs that you can see through the lit- tle connection slots. The ply nibs will nearly push all the way through when you seat the strut assembly against the top side of the lower wing. The canopy glue will act as a “button” to keep the struts from pulling free from the bottom wing. Then run a bead of canopy glue along the


Top view of assembled tail group. The acetate wing (above left) seen just under the fin flash helps aid against flutter. Look carefully and you can see


56


where the Robart hinge (above right) fits in its socket at the tail end of the fuselage. Assembly is accurate each time.


APRIL 2012


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