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Old 10-17-2009 | 09:44 AM
  #63  
Stuart Chale
 
Joined: Jul 2005
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From: , NY
Default RE: Comp ARF Valiant

Real life has left me with just small time blocks to work on the plane
Next up was to finish the stabs. Comp ARF provides phenolic horns meant to glue into a slot that you cut into the elevators (same for ailerons) There is a balsa block in the elevator which can be seen by holding it up to a bright light source. It is large enough that most horns can be used. I am not a fan of single phenolic horns when the servo is mounted in the normal fashion. As the servo rotates the clevis on the phenolic horn will twist to either side. I would prefer a ball link but you are not supposed to use them on phenolic horns. I know lots of people do and I know lots of people have no issues with the clevis twisting on the horn with no added slop over time. It just doesn't seem like the best way to do it so I don't If the servo were mounted on its side with the arm sticking through the skin I would have less issues with it. Of course if the hole in the horn does wear it will be a pain to fix as they are glued in place.
I like the MK horns but choose to try the new Central Hobbies horn that can adjust to an angled surface. (The elevator). They go through the surface with the screw in an aluminum button on the top. The button supplied was rather large so I substituted a couple of smaller ones from MK horns that I hadn't used in the past.

I chose to have my servo arm perpendicular to the linkage at the neutral point. I know some prefer to have it perpendicular at the extremes of travel. I doubt it really matters with the strength of the servos we use. The cutout in the stab is parrallel to the stab root and not the hinge line. I drew a line perpendicular to the hinge line (I used the edge of the stab skin) to the servo arm for my horn position. I marked top and bottom at the same point and drilled a hole from both sides hopefully meeting in the middle. A length of 1/8" carbon rod placed through the hole helps to see if it is perpendicular to the elevator. Adjust as needed. Placing the horns in the same spot relative to the hinge line and at the same angle are crutial to getting identical throws on each elevator half. I made a small ply template for one horn and then made sure the second was set at the same angle. For control rods I like the 2mm titanium rod ends that Central Hobbies sells with 1/8" CF tube for my pushrods. The 2mm end are strong enough for our planes and have a very fine thread for easy adjustments. And they are light.

Final weigt for the stabs with servos and hardware is 161 gms for the right and 159 for the left.
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