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elevator control horn drilling

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indigoonlatigo(at)msn.com
Guest

Posted: Mon Sep 25, 2006 10:10 am Post subject: elevator control horn drilling

I finished the drilling of the elevator horns yesterday and followed the 

direction to the tee.  I indexed one of the horns(the most aft horn with the 

size hole which was specified, then made the block of wood for betwen the 

two horns to keep the drill bit going pependicular to the horn faces.  All 

went well, however once complete, I noticed in addition to there being a 

front/aft discrepancy, there also was a up/down descrepancy.  This means 

that although the length of each horn is the same, one is higher than the 

other. This must be due to the jigging and welding up of the horns.



In anycase, the hole on the second horn ovbiously has a different spacing 

than the first hole which was used as an index.  The edge dimension on the 

first horn are called out as 1/2" from the L.E. of the horn and 3/8" from 

the bottom edge of the horn.  The hole on the secong horn was okay on the 

front/aft spacing which is probably the most critical, but the spacing from 

the bottom edge of the horn was only 6/32". 6/32 vs 3/8, roughly 50% less 

material.



As stated above the main forces on the horn will be in the pull-front edge 

or push-rear edge of the horn.  The bottom edge distance should not be so 

critical, but I obviously would hate to have a crack form down the line in 

this right horn.  I imagine everything is sinched tight with washers and a 

bolt, but has anyone else noticed something like this?



 	  Quote: 	
		  From my analysis, nothing I did would have caused this. This is simply the 

variation in the fabrication of these control horns and the V which is 
	


riveted to the elevator spar and the inboard elevator rib.



There are a lot of welds making up these parts.



John G. #409

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indigoonlatigo(at)msn.com
Guest

Posted: Wed Sep 27, 2006 7:51 am Post subject: elevator control horn drilling

Hi Richard,



I just got off the phone with Van's and asked them to have the powers that 

be review the building manual and make a comment about being careful to 

respect the up/down dimension of where the drill will exit out of the second 

hole on the second horn. Not jus tbe concerned about the most aft horn being 

the designated guide.



I wanted to ask you the minimum edge distance as you stated, is that in 

steel or in alluminum?



I discussed the issue of welding on a plate and  and he did not think that 

was necessary, there also could be a weakening of the original material at 

the intersection of the new plate and the horn.



Just for discussion, (If I could not sleep because of this) he discussed an 

alternate remedy, riveting another plate of similair material(4130 steel) 

with say 6 rivets using the same hole, just to extend the gap between the 

hole edge and the bottom edge of the horn.



As I have stated, I have 6/32 of material on the bottom edge from hole edge 

to horn bottom edge, and when this is all torqued down with washers pinching 

this together I wonder how exposed to stresses this 6/32" of material will 

be.  still need to review the connection, but alteast there are a couple of 

alternative remedies other than rework



JOhn G. 409

 	  Quote: 	
		  From: "Richard Garforth" <richard(at)hawk.flyer.co.uk>

To: "\"John Gonzalez\"" <indigoonlatigo(at)msn.com>

Subject: Re: elevator control horn drilling

Date: Tue, 26 Sep 2006 12:40:50 +0100



John,



I fell in the same hole ! I finished up replacing both horns to get the 

required edge distance. Its a pain Vans don't tell you to look for the 

highest/lowest as well as the rearmost horn. My bet is there is a lot of 

RV10 horns out there with inadequate edge distance to the control rod hole. 

BTW the replacement horns were exactly the same and if I had followed the 

instructions the same thing would have happened again.The recommended 

minimum edge distance for a 3/16" hole is 3/8" (hole centre to edge). see 

AC43.

Ironically the fore and aft edge distance is already increased by the small 

flange so its the vertical that's more important. If its any consolation 

changing the horn was easily achieved it just cost time and money.



Regards



Richard (UK builder 40368)

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