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Beechcraft D-18 Scratchbuild

Old 07-09-2012, 02:47 PM
  #26  
pmullen503
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I finished fitting the nacelle shells. Their combined weight was only 30g. The top was glued into place and the underside will be secured with screws so I can service the retracts and gear doors.

I made the cowl mold and shrunk 3 liter bottles around it to make the cowls. The mold is made of 5 pieces held together with screws. Because the middle of the cowl is a larger diameter than the ends I couldn't use a simple one part mold. The center section of the mold features a wedge that can be removed after the bottle is shrunk and the screws removed allowing the rest of the mold pieces to be removed. A detailed decription of how I made the mold is here

I'll add plywood rings with locating pins and magnets to secure them to the nacelles.
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Old 07-11-2012, 10:13 PM
  #27  
pmullen503
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Gear legs. The leg is made from 1/8" piano wire. I bent the lower part and mig welded it to the leg. I didn't know if it would be strong enough but I clamped the first one in the vise and tried to break it and the wire bent first.

I took some DuBro collars and ground a flat spot on then where they touch the wishbone and cut some brass disks (simulates disk brakes) to reinforce the joint. All the parts were clamped into the jig shown below and silver soldered together. Note the allen wrench used for the axle. A round axle would have been soldered in and impossible to remove. The wrench only touches at the corners and so wasn't permanently soldered in. Somehow I kept the solder out of the allen screws threads so both collars still work.
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Old 07-11-2012, 10:26 PM
  #28  
pmullen503
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Gear doors. After carving out a recess in the wing for the retracted wheel I marked out the door locations on the nacelle shells.

Then I cut slots to accommodate the hinges. I removed the hinge pins and put the pair of hinges on a single long wire to keep them aligned. After epoxying them in I cut the doors free.

I used a simple torsion spring through both hinges to open the doors and a link to pull them closed. The spring was made from 0.012" stainless guitar strings.

The closing mechanism while simple enough, took a lot of fooling around to get the geometry correct. The two curved arms are pushed down by the gear leg as it retracts. The arms in turn pull the doors closed.
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