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Thanks, where did you find the steel streamline tubing?
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After measuring twice the temptation was too great so a set of temporary wing struts were made from 1/2 square spruce stock so the wings could be self supporting. Then the weather turned nice for a few hours so Dean's Ka-3 airframe with wings saw daylight for the first time since entering the shop last year. It was then back to the mundane work of scale modeling with the placement of the floor mounts. Then the full size print of the canopy was printed, scanned, enlarged, reprinted and checked against the fuselage before making a form template for the upper canopy bows. Once steamed the 3/16†dia dowels will hold shape.Comment
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I’m not one that likes to spend a lot of time assembling a sailplane at the field. Plug and fly is more to the point. To accomplish this simple rigging is essential with wing to fuselage and stab to fuselage plugs for the flight control servos.
Starting with the 6mm dia X 182.5mm wing attachment pins that pass thru both fuselage and wing attach points. They are retained by a spring clip made from 0.015 1020 half hard shim stock. Using a low tech forming tool the offset in the spring clip for the pin retainer is formed. The formed 1/16th wire retainer is silver soldered in a slot at one end of the wing pins with a bevel at the other. The shape of retainer allows for the wing pin to be rotated by hand and if necessary a place to grab hold and pull. But after final reaming of the mounts this latter issue will unlikely be necessary.
The lower strut attachment is similar to the wing pins but much shorted. Being located inside the fuselage an easy to install strut pin was essential. Using a 6mm x 45 cap screw the pins were turned, beveled and drilled for the 1/16th retainer pin. Soft silver solder was used to solder the retainer to the pins. Again the low tech tool was used to form the retainer clips.
Progress at the moment is rather slow on both Ka-3 fuselages but proceeding.Comment
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Outstanding Gene! Great ideas...Gunny
Aviation Concepts rcComment
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Spent some of the day making the wing mounting plates for the fuselage pretty. The sharp edges of the water jet cut stainless steel parts were broken and polished with a abrasive disc using a dermal tool. The parts were then glass beaded to a matte finish. When reassembled on the fuselage it was time well spent.
As for the lanyards on the wing mount pins not likely but a good idea for the lower strut pins. I’d hate to drop one down in the void while in the process assembling.Comment
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There are some de-burring discs my father used to use when he worked at a machine shop, resemble a flapping wheel, and others looked like an earplug. They would insert into a die grinder, polishing the edges in no time, making it smooth and slightly eased. I have some in my cabinet I use every once in a while. Great to see you had the same result, it looks great.
LenLen Buffinton
Team Horizon HobbyComment
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After getting all the wing mounting hardware cleaned and glass beaded it was time to get up the courage to mix up the epoxy and set the rear wing mount locations. After clamping a long straight (I mean very straight) 8 ft 1†x 3†Oak board to the leading edge from the back of the wing spar to insure both wings were in line, measurements were then taken from the trailing edge. This was done at several points on each wing to a location at the hinge line of the stab and center line of the fuselage. Once these were recorded it was possible to work on just one wing at a time. Allowing for multiple measuring while the epoxy set. The other wing followed the next day. After rechecking both wings at mutable points all is well. So after both stabs are assembled from the kit parts, mounting of the stab mount bulkheads can be done and measured from the wing for squareness.
There was enough epoxy left to try a test layup of the canopy wing frame bracket. More refinement will be needed here before it will be suitable but the test was positive progress.Comment
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ARUP,
The German CNC routed wing kit uses a HQ 3.0-15 airfoil, so a positive 1.5 degree decollage will be used on the stabilizer in relation to a 0.00 degree wing incidence.
Mating a set of per-built wings to a scratch built fuselage is a lot different than mating a new set of wings to a scratch fuselage. The main reason is that the root ribs are not installed until after it is mounted to the fuselage per the German instructions.
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Switched gears for a time to work on the Ka-3 control stick assemblies for the two airframes. Using the full size print for the assembly it’s just a matter of scaling, cutting, drilling and bending. Then comes the soldering phase of the build. Using soft silver solder that melts at a lower temperature than regular silver solder but provides up to 1200 psi tensile strength will bond the assembly together. A small Butane torch works great for the application. Work is still progressing so more photos will appear soon.
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Working on both Ka-3 control stick assemblies at the same time took a bit of organization to keep the parts separated during the soldering stage. Although the fuselage was assembled in a jig there are a few discrepancies between the two fuselages. To insure proper operation of the control stick, each was soldered in relation to it’s airframe. The control stick cap was turned from an Oak dowel. With a final trip to the glass bead unit, to clean it all, it will be ready for painting.
I have also worked out the stick control unit using two micro servos but need to do some testing before it is bolted in place. Just something more to look forward to.Comment
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Between forming the fiberglass flanges for the canopies there was the skids to laminate. On another building binge there were the two stabilizers to build from the Ka-1 kit before trying to set the tail groups. With that just about accomplished Dean’s fuselage and wings were assembled and set on the workbench to try fitting the stabilizers to his airframe. First leveling and blocking to insure the wing was at “0â€degrees incidence and the fuselage level from side to side, it was back to the stab bulkheads. My first attempt did not turn out in the measuring department, just too many errors, so new bulkhead templates were made and after repeated fittings and adjustments all is looking good. The next step is to make new bulkheads from the templates out of 1/4†5 ply and repeat the process of measuring once again.
Scratch building is so much fun, the smell of fresh cut wood, band saw a singing, shavings on the floor and finally you get to hand sand the finish products. Whither they will work or not is yet to be determined. That’s scratch building.Comment
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Gene, Let me know when you are ready to sand those skids into shape, and I'll make sure the spindle sander is at your disposal.
LarryComment
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After many ups and downs the V tail stabilizers were finally set in place. The bulkheads with there brass tubing were positioned in place with epoxy. A mixture of slow cure West Systems 105 epoxy, milled glass and WS 410 filler was used to set the V tail stabilizers. This provided the time to recheck the measurements and make final adjustments. Surprisingly accomplished without permanently affixing the stabilizers to the fuselage. Cross bracing removed to position the bulkheads will be now refitted.
While the epoxy was curing attention was turned to the tail skid. Although not strictly to print it is close.Comment
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The canopy frame, not unlike the full size, is a composite of materials that when fitted provide the strength and rigidity required. The 3/16 dia. Poplar doweling alone without the clear 0.040 petg is not ridged or will hold proper form outside the fuselage. At this stage care must be used in handling the frame.Comment
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With the canopy frame fitted to Dean’s fuselage, attention was turned to the metal streamline strut fabrication. Using 0.500 x 1.18 x 0.035 wall 4130 streamline tubing to make the Ka-3 wing struts is rather straight forward until you get to the ends. After comparing a few ideas to the full size drawings for the strut, a plan was made. Steel tubing 0.3125 dia x 0.040 wall was trimmed to length and set aside. These will be the pivot attachments for the struts as a 6mm bolt just passes thru. The ends of the streamline tubing were sanded to shape with a 1†wide belt sander and the ends annealed back a 1/4 “ from the end with a butane torch so they could be bent around the 5/16 dia tubing. Using a temporary strut as a pattern, a soldering jig was assembled. 6mm bolts were trimmed to size and threaded into blocks for the height differences and bolted to an aluminum channel to set the pivot distances. After spending some time shaping the ends the parts were glass beaded, cleaned and fluxed for assembly.
After silver soldering the ends, we are talking the hard silver here, the open faces will be capped with 22 ga steel plate soft silver soldered to the strut. Total weight for the pair is just under one an a half pounds.
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