11-02 -> 11: Empennage Attach

Attaching the empennage began by checking over the previous elevator rod end measurements. I noted that there was still a very slight amount of rubbing so checked the elevator eyebolts again to relieve the slight rubbing - and checked the rod ends again with the camera. I am happy i now have the correct number of threads showing, and there is zero rubbing - right up to the limits of travel.

I checked the limtis of travel again (as individual elevators)
L ELEVATOR: 38 UP and 27 DOWN
R ELEVATOR: 37 UP and 30 DOWN

Drilling the Elevator Horns

I started this step with the left elevator installed, and the counterbalance arms held flush with the skins.

Next up was to reduce the diameter of the "E-Drill Bushing" slightly so it fitted in the centre bearing, and i found i also needed to drill it out slightly to #30. I Then made up some simple spacers to fill the gap between the horn and the centre bearing bracket, installed the bushing and drilled. The bushing wanted to spin of course, so it was a bit of a 3 handed job, but if you go medium speed and pull the bit out the clear the swarf it worked ok. 

This gap must be fileld with a spacer

Reducing the size of the "E-Drill Bushing". Not much was needed. 

These were the sppacers i settled on (there are 2 to clear the rivets). 

Clamped and bushing installed ready for drilling.

First hole drilled. 

Once the left was drilled, i repeated the procedure for the right elevator. I then installed the called out hardware, and needed the following hardware to fill the gaps. The left and the right differed by one thin washer thickness only. I don't really like the Van's steel washers as i can see they are rusting already - i will need to look into getting some large cad plated washers instead - the steel ones are also very very thin and bend easily - doesn't feel like an aircraft part to me. 

No time like the present.... 

I have been thinking about this step for a long time - it's one of those that you just have to do - yet if you stuff it up can mean a major revisit to the project (like rebuilding a new elevator, or at least welding the wrongly drilled hole in the horn!). 

So - no time like the present. 

In setting up the elevators for drilling, i mounted the elevators with both counterbalance arms clamped in the "in trail" position. I ran a string line from the end of one elevator to the end of the other (right in the middle of the trailing edge of both) and noticed that both inboard trailing edges were sitting slightly high. I then held the string in my hand, and made sure it ran true down the left hand elevator trailing edge, and unclamping the right elevator and moving it, found there was no position where it ran true down the right hand elevator trailing edge as well (and vice versa). So somewhere in the system is a little bit of twist or out of tolerance. Having read heaps of blogs, i decided to follow the plans and clamp the counterbalance arms in trail, and drill the horns in that position. 

I first measured as per the plans, and the right horn ended up being BOTH the AFT most and UPPER horn, so this was drilled to #12 first. I then fabricated a spacer block, put it in position using a bolt, clamped it and drilled the left horn. 

In the end, with one counterbalance arm clamped in position the other elevator is maybe 1/16" high or low. I guess something mustve moved slightly during drilling etc. It is as good as it will be and we will see how it flies! (one day, maybe). 

Time to make it look like an aeroplane (mounting onto the aft fuse)

I have been looking forward to this step for a while. I lifted the aft fuse assembly onto the "saw horses" i have, and used a ratched strap to hold it gently down in case it tipped. 

The HS was when placed into position and the front was bolted in place. The aft was clecod in place. To drill the 4 remaining holes, i needed to get creative. I wanted to drill the lower ones first and to do this, ended up using a right angle drill to drill to 3/16", then finally a 1/4" reamer on a very long extension. Bolts were installed as i went along. 

The top holes were initiall drilled with  #12, then upsized using the 1/4" reamer. 

Once this was done, i installed the VS onto the assembly. The VS forward mounting bracket was installed and bolts torqued to 43 in/lbs (15 in/lbs running plus 28 in/lbs torque for MS21042-3 nuts). 

Rudder installation (test fit)

Before installing the rudder, i wanted to check all the brackets. I first checked that all the brackets were 90 degrees to the spar with a square, with spacers underneath it to clear the rivets. I then placed a bit of builders string through the end of  a pen and tied a knot to self-centre the string in the top hole. Pulling downward on it, and placing the string in the middle of the lower hole, i was able to check all the brackets were aligned. 

Top - showing the pen end. 

Middle - pretty close to bang on. 

Bottom. 

Happy with this, i did the same thing to the rudder itself. As a result of this, i wound the lower eye-bolt in by half a turn, and the centre one out by half a turn. Later on, i checked the counterbalance arm gap was parrallel at the top, and it was perfect 11/64 all the way along. 

Top (showing the pen end). 

Middle..

End - another pen end was used to ensure this was centre. 

The rudder was then installed and had almost zero binding that i could detect. This will be re-checked at the final install - and at that time i will tighten the jam nuts. This task has been added to the deferred list, so it is not forgotten. 

The rudder was able to achieve the following deflections - and no offset tabs or filing of the rudder stops was needed:

RIGHT: 34 Degrees

LEFT: 37 Degrees

Elevator Instalaltion (test fit)

The elevators were then installed using all hardware, and all bolts tightened and i was able to check the distance from the rudder as per the plans. These should be approximately 0.75" (close enough). 

I was then able to check the elevator deflections as a whole unit for the first time. In this case, the elevator horns were hitting their stops in the aft fuse - i will leave these as they are, and file them at a later date with final installation of the empenange. 

Section Complete!

So with that, we can call the empennage attached! 

11-04: Elevator Rod End Bearings

In a previous post i trial fitted the elevators, and found that the leading edge of the elevator was rubbing on the HS elevator mounting brackets.

Based on the RV7 manual, i elected to wind out the bearings to 7/8" from the spar face, in order to stop some of the rubbing (in addition to some massaging of the leading edges themselves) and i contacted Van's to get some assistance as to how far out i can wind the rod-ends, to make sure i was doing the right thing (newbie paranoia i think - in the end i had to work it out myself!).

RV 7 Build Drawings

Below is the email i sent to Van's - in essence seeking approval to wind out the bearings to the same distance as the RV7:

I have finished the elevators and I’m trial fitting them as per page 11-02.

I set the rod end bearings accurately to 13/16 from the spar face, and the leading edges were rubbing against the HS hinge brackets between 20-30 degrees nose up. There was no rubbing nose down.

I removed the elevator and reshaped and flattened the leading edge a little with a rubber mallet. I reinstalled and it was better but still just rubbing approaching -20 and +25.

I have managed to get it not to rub by backing out the rod ends a turn and a turn and a half. The rod ends are now at 7/8 outboard and 29/32 inboard. At these settings there is no rubbing until -30 and +40 - which I think is good. (They are slightly different to even the gap at the counterbalance skin).

I’m just worried about the number of threads showing out the back of the nutplate.

Can you advise what is the maximum distance the rod end bearings can be taken out to?

I note the RV7 has the same rod end and nutplate - I don’t know if the thickness of the spar and spar reinforcement plate is the same but perhaps you would know this?

  And here is the reply from Sterling:

I am afraid I do not have a max tolerance for this measurement. I can however say this assembly can be treated the same as a nut/bolt combination meaning if you have one or more threads protruding through it is acceptable. The trouble here is that without a borescope it’s a little difficult to see this.

On quick inspection I believe the parts build up in the 14 is thinner as they do not have the forward E-00001 doublers.

So where to next?

I decided to check on the RV7 manual and parts list, and work out what parts made up the build up where the rod ends were installed, and calculate the total thickness:

RV7 Parts list

E-610PP - Hinge Doubler - 0.063"

E-702 - Elevator Spar - 0.032"

E00001A - Front Face Doubler - 0.063

TOTAL: 0.158"

I then compared this to the RV14:

E-00902-1 - Elevator Spar - 0.032"

E-910 - Hinge Doubler - 0.063"

TOTAL: 0.095"

So the RV14 is 0.063" or 1/16" thinner than the RV7, with the same nutplate and the same rod end. 

Get out the calculator...

The RV7 plans ask you to set the rod ends at 13/16 (same as the RV14), but give a maximum value of 7/8":

On the RV7 - this presumably means, that with the rod end set at the maximum 7/8", and with a material thickness of 0.158", there would be the required one thread showing out the back of the nutplate. 

On the RV14 therefore, with the same nutplates and rod ends, but with 1/16" thinner material, the rod ends could be wound out 1/16" more than the maximum permitted by the RV7, which is 7/8". 

So doing the maths: 7/8" + 1/16" = 15/16", or 30/32". 

Given this, i marked my ruler and wound one rod end out to 30/32". 

Borescope time

Here is a picture of the back of the rod end, wound out the 30/32":

Note: the blue paste is Boelube from installation of the rod ends.

As you can see there are ZERO threads showing out the back of the nutplate!!! 

Meaning?

This means two things:

1. This is not an acceptable distance for the RV14, and i will need to wind the rod ends in a little, so i achieve at least one thread out the back of the nutplate. 

2. With regard to the RV7, where the material is an additional 1/16" thicker, if a builder set their rod ends to the maximum distance of 7/8", the end of the threads would be 1/16" inside the end of the nutplate. (this doesn't sound right to me!). Please send me a comment if you think i have made an error here (a highly probable occurrence!)

Final decision

So moving forward, i wound the rod end in a full turn and had another look at the end of the rod end:

This seems to be a much better situation. I then measured the distance i ended up with:

As you can see above, it is about 29/32". I ended up working on 28/32", which is 7/8" as my final decision, and then checked all the remaining 3 rod ends to make sure they were showing one thread:

Conclusion

This was an interesting exercise. I the end, i have finished up with elevators which do not rub at all, and i am happy that the rod ends are at the correct distance for my aeroplane. I hope i have made an error in my calculations regarding the RV7, or i have missed something. Overall i am surprised that Van's didn't publish a maximum value on the RV14 for the rod ends, especially since Step 4 of 11-03 (where you are drilling the elevator horns) they ask you to wind out the rod ends - but how far is too far?

11-03 Step 4:

"NOTE: Verify the minimum distance from the Horizontal Stabilizer Rear Spar web to the Elevator Torque Tube is 1 5/8 [41.3 mm] as shown in Figure 2. Readjust the Elevator rod end bearings as necessary to achieve this distance prior to drilling." 

Anyhow, moving onto the aft fuse!  

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

~~~