Wednesday, 22 February 2017

C17 Globemaster III build - controls

Some odds and sods from the C17 build this week.  I had the entire fuselage assembly up on the ironing board again to check alignment and gaps, as I had the filler out I knew some bits needed attention :

An elevator pushrod installed.  These are pieced together from M3 studding, M3 ball links, and an M3 quick link.  The ball sits in my tufnol sheet horns, secured (or at least will be when she's done) with an M3 socket head cap screw and lock nut :

Here is the top rudder servo, in place with its link.  I have passed the link through the stern-post and onto an aileron torque rod horn that was let into the rudder and secured with epoxy and plastic tube.  This keeps the rudders completely horn-free externally, and the servo will be covered with a flat plate for access :

M3 pushrod hardware on ailerons next.  These were from RCWorld, listed as an M3 carbon pushrod kit.  I'll be getting those again, they're great!

So, that's all the control linkages done, apart from the starboard flap.  The starboard wing is moving along quickly, and all I have left to do is the flap canoes.  The rear fuselage has now had its 3rd (yes, 3rd..) skim of filler and sanding back, and at this point I think is ready for the brown paper.

Items ready to glass are :
Front fuselage
Port wing
...and as mentioned nearly the rear fus / fin assembly.  I will have to get a move on with printing the engines!

Monday, 13 February 2017

C17 Globemaster III build - Flap and spolier

Even though I had already tested these "loosely" earlier on in the build, I am getting close to closing up everything on the port wing ready for glassing, so I need to finalise pushrods, servo install positions etc.

Most of my time was spent trying to figure out what I had done last time, and going through old pictures on my phone to get that information!  In the end, I build a small test piece on a plank of wood, and proved out the linkage positions and lengths.

Here is a video of the flap operation, using the servo-slow function on my Horus :

Here are a couple of views with the "full stopping power" applied - ailerons and spoiler up, flap full down.  Hopefully that'll make this big beastie pull up quick on the landing run.

I actually think there is a little more down-flap available, so I could get perhaps 5 more degrees down, if required.

Thursday, 2 February 2017

C17 Globemaster III build - elevated horns

I have had delivery of a few extra bits and pieces recently, so I've moved on with the elevator horns.  These are cut from 3mm Tufnol plate, then epoxied in place through to the next skin with plenty of fillet all the way round :

 Some M3 hardware attached to the ball link, which also has an M3 threaded hole.  Nice short pushrods will be used here, see one of the digital HV metal geared servos in place below :

And lastly my 3D printed flap hinge blocks.  These will be mounted in the wing flap canoes, then the ball links will be glued into the flap canoe itself with a short run of M3 studding up it's chuff to secure it :