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Nitroplanes Skymaster 337, Build Tips
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04-22-2010 | 08:09 PM
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steve1mac
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New Lenox, IL
RE: Nitroplanes Skymaster 337, Build Tips
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<u>Servo Install</u>
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There are no control rod holes through the firewalls so you are on your own as far as lining up your hardware. The servos are close to the fuel tanks so pre-fit everything in that area before you bend and cut to length your control wire for throttles and steering wheel.
Since I am using Magnum .91 XL engines I decided to upgrade to 20 oz. fuel tanks for longer flights. I mounted the front tank flat in its place with foam and balsa twigs glued around it for support. The steering pushrod is under the tank and under the X braces holding the tank. I used short pieces of tubing glued in at certain places to help guide the pushrod under the tank and through the firewall. The rear tank is on its side and fits in real snug. This also leaves plenty of room for the rear throttle servo and piano wire. Three servos! That’s all you’ll find in this big fuselage.
On my plane, ailerons and flaps are Y harness hookups. CAUTION: Make sure your ailerons are mirror image (i.e. both servo arms are facing inwards). And your flap servo arms should both be on the same side (i.e. both arms face the left wingtip). It doesn’t matter inwards or outwards, left tip or right tip as long as the aileron servos are opposites and the flap servos are the same.
The plans call for two servos to control the elevator. Well, since I have read about all the weight other builders added to the nose I decided to install just one elevator servo. For better control I installed 2 control horns and a dual servo arm. This mod had a large effect on the balance. It’s a standard Futaba S3004. Maybe under powered (might change it to something stronger). Another option is to use flexible pushrods and put the servos farther forward near the main wing somewhere. If anyone has success with this method let us know.
Since we are talking about the rear of the plane I want to add that I only used the bolts and blind nuts for horizontal stabilizer attachment. I should be able to move the tail booms out about an inch, one at a time, to expose the joint so I can add epoxy. I’ll let you know when it happens.
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