R/C Control Horn

[Marty Hammersmith]

  Last night while Sparky was working on his profile Viper, he mentioned he was using an R/C control horn despite it being a no no. I'm building a 90% Sarpolus Challenger and the hardware I wanted to use isn't going to work out. So, I am tying the two elevator halves together with 1/8" music wire running through a  brass bearing. Then I'll control the elevator by an R/C control horn on the right elevator half. Am I setting myself up for a real problem? Why is using an R/C control horn on control line a bad idea?

     Also, the hinges are 1/8" Robart hinge point pin type. How do I loosen them up a bit? When assembled the elevator won't drop under it's own weight partly because it's light and the rest is resistance in the hinges.

[Jim Svitko]

Years ago, I saw plans for profiles that showed moving a regular control horn (wire brazed to a blade) over to one side so that the blade lines up with the pushrod.  Bend as usual to join the elevator halves.  I might have done that back in the day but I have not messed with a profile in a long time so I can't remember for sure.

I have some of the Robart hinges but I never used them.  They are a bit "tighter" than the Dubro hinges but not excessively so.  I have concerns about the lugs on the Robarts.  They look a bit flimsy but I have heard of some using them with no issues.

[Dennis Toth]

Marty,
You can use the RC horns but you need to add a mount pad (~ 1/2" wide strips the length of the elevator or flap) of 1/32" plywood above and below the surface to avoid crushing problems. I install them with 30 min (or slower) epoxy and clamp them. I then coat them with thin CA to toughen the surface. Never had a failure on 46 size ships (won't use them on full size 60 ships).

The point hinges could be loosened by using a heat gun to get them warm and work them till loose. This should only take a few minutes, work with one to get the feel for how much heat is needed.

Best,    DennisT

[Fred Cronenwett]

I have been using RC equipment for over 20 years now (hinges, etc) without any problems. Just make sure the hinge are pinned or glued in so they don't come out.

I have also converted multiple RC ARF's and kits over to CL with success using all of those parts without any problems.

Fred

[Ken Culbertson]

Never had a problem with Robarts on IC.  They free up in time just fine.  I used them on all of my IC planes but they are too stiff for me for electric.  I used them with pockets so that you can make the surface removable.  RC horns are fine with the reinforcement to prevent crushing.  I don't like them because they place all of the control force on one side of the plane instead of both with the horn brazed to the wire.  Veco made a profile horn and I think Okie has one if you don't mind waiting.

On Robarts Make sure that the center of the flap wire lines up perfectly with the hinge center or they *will* bind.  Glue a tube into the elevator for the flap horn and do not glue the horn to the elevator.  A trick that I used to mount them on solid elevator/stabs was to drill them out and dry mount the elevator.  Work out any binds then drill a 1/64" hole in the stab through the hinge and use thin CA through that hole.  Then I would redrill the hole to 1/32 and put a dowel through it.  Never had one come loose.  Of course you have to do that before the final finish.  I used pockets for the elevator to make them removable.

You probably know all of this anyway but it is fun responding - Good luck - Ken

[Dan McEntee]

   For the 90% Challenger that you are building, I see no problems with using an R/C horn, but these are all not created equal!! Look around at different brands and such, some are a heavier plastic than others. Make sure you use one that is tall enough for some adjustment up or down the horn for control speed and sensitivity. SIG made some heavy horns, and I think Dubro has some for 1/4 scale models that might suit you. If in doubt or can't find what you need, get some hardware store aluminum angle with the sharp corner, and make one from that material using a plastic one as a model for the shape and as make it the size you need. The 1/16" thick legs are plenty strong enough for this.
   I have never used Robart hinge points,
   HAPPY HOLIDAYS!! and Type at you later,
  Dan McEntee

[Perry Rose]

Du-Bro makes an Adjustable Control Horn  DU-493, also sold by Brodak, same number. Extreme adjustability. Must be used outside a full fuselage like a profile. I've used them on full and profiles with great success. Under 5 for a pair. Long ago I started making my own using a 4-40 bolt and up to a 6-32 with a nylon aileron connectors. Change in length by thousandths instead of inches.

[Ken Culbertson]

Long ago I started making my own using a 4-40 bolt and up to a 6-32 with a nylon aileron connectors. Change in length by thousandths instead of inches.

I made a similar one to drive the Canard in my latest adventure.  I had a lot of "fun" making the connector to the pushrod.  It is working great and I love being able to make micro adjustments.  The canard is a "stabilator" type so it doesn't take much force.  I wanted to try one on the elevator but was concerned about the bolt breaking from the back and forth pressure.  How are yours holding up?

Which RC Connector do you use?

Ken

[Perry Rose]

Hi Ken, the proper name is "E-Z Adjust nylon horn bracket" Du-Bro number 557 for the 4-40 and 559 for larger screws.

[Ken Culbertson]

     Also, the hinges are 1/8" Robart hinge point pin type. How do I loosen them up a bit? When assembled the elevator won't drop under it's own weight partly because it's light and the rest is resistance in the hinges.

One thing I missed earlier and it is the key to success with Robarts.  Make tripple sure that they are perfectly straight 90Degrees) and parallel to the hinge line - not rotated.  If they are not they will bind.  If you align them before gluing with the elevator half pointed straight down you can get them perfect on one axis.  The other depends on how the hole was drilled. 

In every bag I have bought there are usually one or two hinges that blind some.  Check for flashing in the hinge area.  It can be flattened by sliding a piece of 600+ sandpaper into the cracks in the barrel then working the hinge.  A little CA on the back of the paper and you have a very thin file!  You might need to use an old fashion double sided razor blade to separate it a little.  Sometimes the razor is enough if the bind is from the hinge wire being crimped too tight.  You can also sand the outside lightly to remove the flash.  I also oil them some before choosing the ones I am going to use.  They should fall by their own weight just as if they had an elevator attached. 

Ken