Mounting & Tail


Getting ready to mount the tail on the fuselage, I have work to do on both the main fuse as well as the tail, in order to get them ready for each other.  First, in order to mount the mechanics to the mounting plate, I made up some aluminum blocks and tapped them so they could be mounted to the plate.


The KDE Direct aluminum base for the Trex 700 is perfect for this, as it gives me a really solid mounting.  Now, I can reassemble the mechanism on top of the plate.


The tail boom gets a bearing-holder end cap, just like on the mechanism.  Here is my trusty lathe turning it out of Delrin:


This mounting, I planned way ahead, and had already milled channels in the tail for the wiring and the gearbox bearing.  The tail skid is not scale, but it is very, very strong, has a 90 degree bend inside the tail fin, which is filled with epoxy for strength.  I wanted a tail skid that could actually handle the energy of a heavy, tail-first touchdown without folding up. 


When I designed the gear mechanics, I made them so that they would absolutely, positively lock in the "Down" position!  With the fragile and detailed ADF Pod underneath, I wanted to take no chances.  What I discovered while working on it, is that it was possible to "hyper-extend" them past the "down" position.  To prevent this, I machined an arm that locks onto the keyed shaft, and limited with a Delrin stop.  


I also needed to make the rudder control rod about an inch shorter.  This was an opportunity to correct something we saw during the flight trials:  The rod was vibrating (just a bit).  I switched from a carbon-over-brass-over-stainless rod to a brass-over-carbon-over-brass-over-stainless combination.  This is incredibly stiff and should eliminate the problem completely.


The horizontal fins are really attached well (I drilled holes in both the body and the fin so the excess epoxy would form "Rivets").  Unfortunately, the body of the tail actually flexes, so I did not get the rigidity I was looking for.  I ended up drilling a 6mm hole through the fins, and inserting a 6mm carbon rod (actually a Trex 700 Tail boom brace) all the way through the body from the tip of one fin to the other.  The high placement of the tail tube in the tail section allowed this rod to pass under it.


Now, with solid horizontal fins to mount to, I filled the vertical fins with epoxy, then milled out recesses for screws.  The vertical fins were then attached with BVM Aeropoxy (god, I really love that stuff) and screws.


After all the prep, attaching the tail was rather anticlimactic.  I  taped everything up, drilled holes for screws, then added epoxy, and set the screws in.  


Some clamps and a prop under the tail skid hold everything together while the epoxy cures.....


And it's starting to look more like a Helicopter!


Here is the join from the inside, after some touching up with an airbrush for the interior color.  I am doing this as I go, as the paint shop will never be able to get complete coverage after other parts are added.


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Professional Photography by Les Bidrawn    |    © 2010