Wednesday, July 11, 2018

MPC Lunar Patrol, Part 20 - Glide Trimming

The final process of the Lunar Patrol build is to trim the gliders for flight.
The noses have been left unglued to the body tubes to facilitate this.
For trim weight, I am going with a #6 x 1/2" sheet metal screw and the required number of stacked #6 washers to be attached to the base of the balsa noses.


A quick trip to a local grass-field park, and I'm ready to try it out.
The noses have been inserted so that the attachment pin is oriented to the top of the glider.  I expect several hard landings during trim testing, and I don't want to break them off.


Small delta-wing gliders are notorious for being somewhat difficult to trim out.  I found that giving the birds a good heave in a near vertical trajectory gave them enough altitude to do whatever looping and turning was necessary before they would settle out into a glide pattern.
With five washers installed per bird, I was pleased to observe that they would properly flatten out into a good glide with a very minimal stall pattern.



I did note that they were highly susceptible to even the slightest wind disturbance, but would recover quickly.
Satisfied that the trim of both gliders was well within the desired window, it's off to the work bench to permanently glue the nose cones in place (remembering, of course, to put the attachment pins in the correct orientation!).
Hear are the completed gliders, all ready for their maiden powered flight. 


Any further tweaking of the glide trim will have to be done while observing a real flight, with  judicious placement of additional trim clay.
Also, the hand launch trim testing did not reveal much information about the extent to which the gliders turn, since they did not level out into glide until they were a few feet above the ground.
From my initial observations, they seemed to fly fairly straight.  Again, a powered test flight will reveal if I need to trim for a slight turn.  I don't want to be chasing two gliders into another county (or two different counties 180 degrees apart!).
Anyway, I do believe the Lunar Patrol is officially finished!


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