11-04: Elevator Trial Fit

Rod End Bearing Installation

Once the leading edges were rolled, i installed the rod end bearings using my PVC tool i made earlier. The tool ended up breaking after a few tries, as the inside tube edges had been worn away, so i ended up using a pair of smooth jaw parallel pliers to gently screw it in.

The plans call for you to install the bearings 13/16" from the spar face, so i used a ruler with a piece of tape at 26/32" to set the middle of an AN3 bolt at that distance.

I have some nifty pins my dad made up for me based on something we found sold by Cleveland, and I used these for the trial fit of the elevators:

The pin is inserted, then the aluminium "nut" is removed. The pin is sized to match an AN3-10 bolt, and the threaded tail is designed to fit inside the skins, so it does not interfere when moving the control.

 

The pins worked well, but i noticed there was a little bit of play, so i thought it would be better to just install them using the called out hardware - AN3-10 bolts. Getting these is however is a little difficult, so i used some scrap and made up a 'don't drop the bolt tool'™:
:

The second bend at the 'handle' end really helps to maneuver the bolt into position more easily.

 

Elevator Rubbing

Once the elevators were installed, i checked the amount of throw i was able to get. According to the manual, it needs to be +30 degrees, and -25 degrees. This was checked by holding the elevator counterbalance level with the skins and zeroing out the iphone level, then moving the surface.

Unfortunately, i was unable to get to the full throw, before the elevator leading edge skins began to rub on some part of the HS rear spar. I got to about +25 and -20 when the rubbing began and i could feel the skins binding. In order to work out where this was, i removed the elevator and placed some blue tape on the area. I then added some chalk to the areas i thought might be the cuplrit and moved the surface until i felt it binding, then checked for evidence of chalk on the leading edge.

Tape added before the chalk was applied

The areas of rubbing can be seen between the 2 lines:

What to do next?

Given the rubbing experienced above, i decided to scrap both elevators and start again...

NOT!

I figured i had 2 options here - the first was to try and reshape the leading edges with a rubber mallet and with my hands to try and stop them rubbing so much. The second was to wind out the rod end bearings a little - but how far can i wind them out?

Unfortunately i was unable to see inside the HS at this time to see how many threads are showing out the back of the nutplates. Instead i reverted to the forums, and ultimately the RV7 manual, which has the following helpful diagram:

Given the RV7 uses the same rod ends, and the same nutplates, and the material is about the same thickness, i figured that i could safely wind the rod ends out to 7/8". I have contacted Van's to check that this is acceptable, and i am waiting for confirmation. Whilst i am waiting, i decided to trial fit the elevators once again, after winding the rod ends out, and after massaging the leading edges somewhat.

See HERE for a post on where i ended up with the rod end bearing distances.

Success!

The combination of the above actions seemed to have worked. To check it all out properly, i skipped ahead and made the spacer block for the elevator horns shown at page 11-04:

I then clamped the counterbalance arms against the skins, so the elevators were "in trail":

With the elevators 'in trail' i was able to compare the 2 elevator horns - in my case they were fairly close together:

I placed a string line in the centre of each trailing edge, a little in from where the ends taper, to check for straightness. I found that for the most part, the elevators were straight, however both inboard ends were around 1 trailing edge diameter "low". They seemed even however, so i guess this is just the build up of tolerances in the build of the elevators and the HS. Each elevator as previously noted was straight in itself, so likely this is the mounting of the elevators on the HS. In any case i don't think this will cause major issues when flying.

Right tip end

Left tip end

Left root end

Left tip end

I was then able to install the spacer block, and clamp the 2 elevator horns together, and remove the clamps from the counterbalance ends, and finally measure the amount of travel i was able to get with no binding. It turns out i can easily get the required travel (+30 and -25) with zero rubbing, and i can in fact to go +35 without any rubbing at all. I can get -26 when one horn contact the lower portion of the HS spar.

Required upward travel

It goes to here without any rubbing

It stops here and is contacting the HS hinge brackets, but is clear of the skins. Ultimately the upward travel of the elevator will be controlled by the angles on the aft fuse deck - so i might even end up taking them to +35 - but that is waaay in the future. 

This is the maximum lower travel

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