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RV-14 Cowl Hinge

KeithB

Well Known Member
I?m on Sec 29-08 ? drilling of Cowl Hinge to Firewall flange and Fuselage Side Skin. I have measured and cut the hinge as described on Sec 29-07 including the pilot hole for alignment, then match drilled the hinge as described in 29-08 steps 5 to 7. However, what I get seems to be very poor alignment of the end-most holes on the hinge ? basically a half hole on each end of the hinge rather than a proper ?edge distance?. I?ve measure this at least 5 times and its all correct.
Picture shows hinge on skin, removed from the firewall.
izlxjr.jpg


Possibilities:

1. Maybe this is right ? but the half holes on the hinge ends are really hard to machine countersink and rivet and it just does not seem right.
2. Hinge should be lower. Figure 1 on 29-08 would ?suggest? (not totally clear) that the hinge should line up end-to-end with the Hinge Shim and over the 2nd bottom-most skin hole. However, the rivet diagram on 29-16 would suggest that the bottom hole of the hinge is above the 2nd bottom skin hole (2nd lowest hole is AN426AD3-3.5 vs AN426AD3-4.5 for all the others). This would mean the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is incorrect.
3. Hinge should be higher. Moving up approx 1/4 inch eliminates the ?end holes? and the rivet length in 29-16 is now logically consistent with the thickness difference at the bottom, but the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is again incorrect.

My vote is #2 ? lower the hinge and lengthen it by about ? inch to match the Hinge Shim and change the bottom rivet to AN426AD3-4.5.

Any advice from you pioneers out in front?
 
Not sure your issue , but are you looking at the diagram, picturing the loops up. If memory serves me correctly, I had them wrong in my head for a while then realized that the loops are facing away from you in the diagram. I'm not looking at the manual, I'm not sure this may be your issue, and I'm not sure I remember these steps correctly. Just thinking out loud, may be I should stop.
 
After re-reading the thread that GeraldC referenced (I had it printed out for my small "errors and omissions collection"), and then re-reading (and sleeping, and re-reading), I have seen the light. RVBuilder2002's measurement of 4 3/16" below the upper edge of the skin moves the hinge higher by approximately 1/4", eliminating the edge distance problem at both ends. It would appear that the measurement for the pilot hole is off by that 1/4" - should be ~3 7/8" from the upper end of the hinge rather than 3 21/32 as indicated.

Thanks Ron and GeraldC.
 
I am on this section as well. I have already drilled the pilot but have not match drilled the whole hinge. Would there be a problem with drilling a new pilot hole 1/4" above the already drilled pilot hole? The edge distance will be close but should be in tolerance correct?
 
After re-reading the thread that GeraldC referenced (I had it printed out for my small "errors and omissions collection"), and then re-reading (and sleeping, and re-reading), I have seen the light. RVBuilder2002's measurement of 4 3/16" below the upper edge of the skin moves the hinge higher by approximately 1/4", eliminating the edge distance problem at both ends. It would appear that the measurement for the pilot hole is off by that 1/4" - should be ~3 7/8" from the upper end of the hinge rather than 3 21/32 as indicated.

Thanks Ron and GeraldC.

Keith,
What is the Rev. level of the manual pages you are using?
 
I am on Rev 1. I increased the end measurement for the pilot hole (at the top) to 3 15/16". (I re drilled a second hole.). This results in a lower hole, thereby raising the hinge approximately 1/4". The hinge then ends above the shim at the bottom, consistent with a shorter rivet in the last rivet in the shim (3rd from bottom = hinge+shim+skin, 2nd from bottom = shim+skin, bottom = skin+firewall flange).

While checking for glitches/errors, on 29-09 in Figure 4, some of the holes around the left-most "do not dimple" call-out at the bottom left are out of place in Rev 1. It only causes a little confusion. It would appear to have been created in going from Rev 0 to Rev 1 - when figure 4 was shifted lower, a small collection of holes did not get moved with the rest of the figure (Rev 0 has an unambiguous layout).
 
Hi Scott,

Not a big deal, just curious. Working off of Rev 1. The distance from the top of the hinge to the pilot hole causes a mis-alignment as mentioned by KeithB. I basically did the same as him for alignment. Hopefully this will work come "cowl" install time.

Jim
 
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