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Workshop Build-Along — Douglas Skyraider Part 7 — Tailwheel

Discussion in 'Giant Scale News' started by GSNadmin, Oct 17, 2016.

  1. GSNadmin

    GSNadmin Staff Member

    While the fuselage is being sheeted, I work out the installation of the scale Tailwheel unit (custom made by Earl Aune), and install the new plywood former and reinforcement doublers while I still have access to the parts in between the applied pieces of sheeting. The sheeting helps keep the fuselage structure ridged during the work as I remove it from the supports.


    I start by simply laying the tailwheel unit over the plans and then I take measurements to zero in on the exact location for the new plywood former.


    I also check the retracted position of the gear to see if there is any modifications needed. In this case with the wheel retracting in the scale “forward” direction, I do have to trim away some of the F-10 former. Much easier now than when the gear is installed.

    The plans shows a standard Robart tailwheel unit which retracts aft similar to a P-51 Mustang.
    The first step is to rough cut the former from 1/8-inch A/C birch plywood and to draw a centerline to keep the tailwheel centered when the unit is finally installed. I did much of the design work with my CAD program and used it to locate the attachment holes for the mounting bolts and blind nuts.


    The drawing about shows the basic layout and parts of the scale tailwheel unit along with the mounting plate and the bolt hole locations.


    I was also able to determine measurements for various parts. I originally was going to add a scale tailwheel well, but this interfered with the steering cables so I did away with the idea. This also saves some weight.


    Here you see the unit bolted to the new former which has been glued in place along with lite-ply reinforcement doublers on either side of the former. Also you see the Former F-10 has been trimmed to shape to allow the gear to swing forward when retracted. Here is the geat in the down position. The tail-hook mechanism has removed to get to the new former.


    Here the Tail-hook mechanics are in place and the wheel-well framework has been installed along with 1/32 inch belly sheeting to add some toughness to this section of the belly.


    So once the mechanics are in place, you can then install your servos in the area above the wing saddle and run your pushrods and control linkages for the tail. For the tailwheel steering, I used Sullivan Products Kevlar pull-pull cord.


    This is a view of the retraction actuator arm linkage. To eliminate slop in the setup, reinforcement doublers will be added to support the red pushrod guide tube.


    You can see here that I used large loops to connect the cords to the tiller arm. This places the knots away from any hardware items where they might get chaffed because of vibration.


    The cords travel through the fuselage and I used a couple of guides to direct them over chaffing areas in the fuselage structure. The servo you see at the bottom is the tailwheel retract servo.


    Here the pull-pull cords are attached to tension springs that I attached between the cords and the pull-pull hardware. This allows the cords to remain in tension so they do not snag in the tailwheel structure when the gear is retracts. Usually the cords would go slack but better safe than sorry. This also softens the steering a bit and prevents taxiing shocks from being transmitted to the servo. As you can see, I am using heavy duty servos from HitecRCD.

    Now that the servos and control linkages are in place, the rest of the fuselage sheeting can be applied.

    Stay tuned for more updates to come.

    For the previous post CLICK HERE

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