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  #1  
Old 03-19-2018, 10:53 PM
StressedOut StressedOut is offline
 
Join Date: Jun 2017
Location: Fullerton, CA
Posts: 40
Default Countersinking the Rudder Trailing Edge Wedge

I'm trying to machine countersink the rudder trailing edge wedge, but I'm running into a problem. I'm hoping you guys who've been down this road already can offer some advice.

Per section 5.5 (machine countersinking), it says to go 0.007 in. deeper than flush if you're putting a dimpled skin on top of the countersink. On a scrap sheet of 0.063 in. aluminum I set the countersink cage per instructions. Then I took a scrap piece of wedge and countersink both sides.

When I examine the two sided countersink, it appears there is a knife edge condition and the hole is enlarged slightly. To confuse matters further, on page 5-12 there is a cross section of the wedge/skin assembly and it alludes to a significant and decidedly non-knife edged hole with both countersinks.

Furthermore, in section 5.8 (riveted trailing edges), there is no indication that you should cut differently than specified in section 5.5. Section 5.8 deals with setting up the proper angle on the wedge to use your drill press for countersinking. I'm using the Cleaveland Tools drilling guide for the RV-14 wedge so that allows me to get a nice perpendicular angle for this countersinking.

Can anybody clue me in to what I should do?
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RV-14A Kit#140433
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Member of EAA Chapter 92 (KCNO)

Last edited by StressedOut : 03-20-2018 at 01:18 PM. Reason: Correct spelling errors
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  #2  
Old 03-19-2018, 11:02 PM
rvbuilder2002 rvbuilder2002 is offline
 
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What you are seeing is normal and acceptable in this specific application.
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  #3  
Old 03-20-2018, 06:19 AM
iwannarv iwannarv is offline
 
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Location: Stafford, KS
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I think in most cases, you will see some knife-edging, per most experiences on the board with the trailing edge wedge. I experienced this as well, but had no issue getting the assembly together and good quality rivets on the TE when all was said and done.
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  #4  
Old 03-20-2018, 11:45 AM
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sbal0906 sbal0906 is offline
 
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Location: Winnipeg, Canada
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While I haven't committed to completed the trailing edges yet because I want to do a bunch of trailing edges at the same time, I've practised and experimented a lot countersinking that wedge and could never find a perfect countersink that yielded no knife edge and yet was deep enough for the rivet. Further reading on this forum told me that that's as good as it will get. And with the addition of a bonding adhesive, the connection will be sound.

Cheers,
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  #5  
Old 03-20-2018, 01:15 PM
StressedOut StressedOut is offline
 
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Default Summary

So these are my takeaway points from this T.E. wedge discussion:

1. Done per the plans, there is no way to avoid a knife edge condition and an enlarged hole.
2. It is better to have a good fit on the wedge for the skin dimples than a shallow countersink to avoid the knife edge.
3. The wedge is acting more like a filler than a structural component so it is acceptable in this specific instance to have a knife edge condition.
4. The adhesive bond is very necessary to lock the wedge into position because it may not be mechanically locked into place because of the slightly enlarged holes.

Does that about sum it up?
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RV-14A Kit#140433
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Construction log - mykitlog.com/ajackson
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  #6  
Old 03-20-2018, 02:30 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by StressedOut View Post
So these are my takeaway points from this T.E. wedge discussion:

1. Done per the plans, there is no way to avoid a knife edge condition and an enlarged hole.
2. It is better to have a good fit on the wedge for the skin dimples than a shallow countersink to avoid the knife edge.
3. The wedge is acting more like a filler than a structural component so it is acceptable in this specific instance to have a knife edge condition.
4. The adhesive bond is very necessary to lock the wedge into position because it may not be mechanically locked into place because of the slightly enlarged holes.

Does that about sum it up?
I would agree with 1 - 3, but not 4.
Because the wedge is technically a spacer tightly riveted between the two skins with the skins dimples loading in shear within the countersinks, with a properly formed shop head, it is a strong joint even without any adhesive.

The primary purpose of the adhesive (whether it be tank sealant of VHB tape) is to be an aid to getting a nice straight training edge.
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  #7  
Old 03-20-2018, 06:02 PM
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sbal0906 sbal0906 is offline
 
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Ah, ok. I had thought that there might still be a risk over time of lateral shifting if the holes were slightly enlarged and that's why the adhesive was used.

Thanks!
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  #8  
Old 03-23-2018, 10:22 PM
StressedOut StressedOut is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post

The primary purpose of the adhesive (whether it be tank sealant of VHB tape) is to be an aid to getting a nice straight training edge.
I let this little gem roll around in my head the last couple of days and suddenly it all made sense. I was very confused as to the exact steps one needed to do to button up the trailing edge even after multiple readings of section 5. I've heard other builders use a piece of aluminum angle and cleko the trailing edge to it for straightness, but I couldn't figure out how to do the final riveting. When you said the adhesive was an aid for straightness it all came together.

I picked up a 1 in. x 2 in. x 0.10 in thick rectangular steel tube about 5+ feet long that's dead straight. I'll match drill holes in the tube and that will be my jig for the T.E.

I've decided to use ProSeal on the T.E. after I got some great tips on quick and easy sealant application from our AOG (aircraft on ground) team at work. I'll proceed per the plans but I'll cleco the T.E. to the steel bar and let the sealant cure fully.

Once the sealant is cured, remove it from the tube and rivet the T.E. per section 5. I'm counting on the edge to be dead straight after the sealant is cured.

Does this sound about right?
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Art Jackson
RV-14A Kit#140433
Completed: Vertical Stab
Working on: Empennage (Rudder/HS)
Construction log - mykitlog.com/ajackson
Dues paid on 2 November 2017
Member of EAA Chapter 92 (KCNO)
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  #9  
Old 03-23-2018, 11:23 PM
Tom023 Tom023 is offline
 
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The bar should give you a straight TE, that is how I did mine and it is perfectly straight (i.e., not wavy or bowed). The real challenge for perfection is to build the rudder without any twist, as it is possible to have a straight trailing edge but also have twist. Small amounts of twist are acceptable (e.g., if I recall correctly mine has about 3/32 and should be fine). There are some threads discussing this topic.
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  #10  
Old 03-24-2018, 07:06 AM
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M McGraw M McGraw is offline
 
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Location: Greenback, TN
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Quote:
Originally Posted by StressedOut View Post
I let this little gem roll around in my head the last couple of days and suddenly it all made sense. I was very confused as to the exact steps one needed to do to button up the trailing edge even after multiple readings of section 5. I've heard other builders use a piece of aluminum angle and cleko the trailing edge to it for straightness, but I couldn't figure out how to do the final riveting. When you said the adhesive was an aid for straightness it all came together.

I picked up a 1 in. x 2 in. x 0.10 in thick rectangular steel tube about 5+ feet long that's dead straight. I'll match drill holes in the tube and that will be my jig for the T.E.

I've decided to use ProSeal on the T.E. after I got some great tips on quick and easy sealant application from our AOG (aircraft on ground) team at work. I'll proceed per the plans but I'll cleco the T.E. to the steel bar and let the sealant cure fully.

Once the sealant is cured, remove it from the tube and rivet the T.E. per section 5. I'm counting on the edge to be dead straight after the sealant is cured.

Does this sound about right?
Art,
I did something very similar. I used the tape, as per the plans, left it clecoed together while I went to work. A week later I did the rivets. The trick to using the tape or proseal is to let it sit for a bit and get a good grip on the parts.
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