Sig 1/3 Scale Spacewalker Review
Tail Feathers
5/7/2002 - The tail feathers are fairly simple to construct. Each piece is constructed of 3/8" x 3/4" balsa, with 3/8" x 3/8" and 3/16" x 3/8" cross members. The biggest problem I had was finding stock balsa in the kit that was straight enough for the leading and trailing edges. I finally bought some good quality 3/8" x 2" x 36" balsa and cut it down to size as necessary.
The elevator is built as a single piece elevator. That is, according to the plans, the two halves are connected by a 3/8" x 3/8" x 4" piece of spruce. The plans call for a single elevator pushrod. I modified the plan slightly to include a control arm mounting hard point on each elevator half. This way, if I decide later on in the construction to use two elevator push rods I can simply cut out the spruce joiner and mount each half independently.
The one thing I didn't like about the elevator construction was the fact the spruce hard-points and the spruce joiner were simply butt-jointed to the balsa components of the elevators. In hind sight, I probably should have created lap-joints for additional gluing area and strength, but hopefully the prescribed method will be sturdy enough. I used slow cure finish epoxy for these joints.
The kit contains a 3/8" balsa sheet with all the curved elements of the tail feathers pre-drawn. You simply have to cut them out and sand them to shape. This simplifies the process of making the curved elements of the rudder and elevators.
One thing that I didn't find in the manual was guidance/directions on how to bevel (or round off) the leading edge of the elevator and rudder. The instructions indicate to round ALL edges of the horizontal stab and elevators. This doesn't make sense to me - I can't see why you would round off the inside edge of the elevator counter-balances. I will have to study this some more.....
The hinge gap between the control surfaces is 1/8". The instruction manual refers to this gap as being almost scale since the gap on the full-size plane is 1/2". The plans indicate that a 3/32" x 3/8" balsa strip can be glued on the trailing edge (leaving the offset for the hinges) to fill this gap. The only issue I have with this method is that the pin hinges will have to be installed before mounting the hinges and then cannot be removed. I inspected one of the Spacewalkers at Top Gun this year and the hinge gap was at least 1/8", so it must be scale as the instructions state. The instructions indicate that this gap does not introduce any performance issues, but my concern is flutter. I will decide shortly which approach to take.
9/1/2002 - See new pictures of tailfeathers mounted and hinged. One thing I did was to add a piece of 3/8" balsa under the horizontal stab where it fits to the fuselage. I cut the balsa to fit between the top longerons of the fuselage. I then cut out a notch to allow the front of the fin to pass through - same as the notch in the horizontal stab. I figured that adding this between the longerons would give a better gluing surface and better structural stability for negligible weight.
9/6/2002 - I installed the flying wires on the tailfeathers today. I used Sullivan flying wire kit (S546). I had to use two of them (ouch - $$$) because each kit did not include enough material to construct 8 wires. The kit comes with both brass wire and kevlar string. I decided to use the brass wire. The kit also comes with brass couplers that you can solder onto the end of the wire. I tried to solder one on, but finally gave up...... So, I used the small copper sleeves that were supplied with the kit. Simply make a loop and crimp the sleeve down tight. Not as clean, but works nonetheless. I used the eyelet screws on one end of the wires to allow for adjustment. When installing them make sure to back the eyelet screw almost all the way out of the clevis since you will need to be able to screw it back in to take up the slack. I drilled holes to accommodate 4-40 socket head screws through the horizontal stab as shown on the plans. I then hardened these holes with some thin CA. I cut the ends off the tabs to which the clevis attach to make attaching the clevis to the tab easier. See pics below.
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