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  #1  
Old 12-03-2012, 01:26 PM
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mvidalr mvidalr is offline
 
Join Date: Aug 2011
Location: Monterrey, Mexico
Posts: 121
Default Tip: Elevator Trim Tab Riblets

Sooo, after extensive search online and my first E-619-1-020 Elevator Trim Tab attempt was ruined thanks to Van's bad sense of humor with the procedure of bending the side flaps, I decided to go for the highly debated riblet method. Here is my procedure to all of you who look for an easy (yet not so quick) way to do it with beautiful end results.
I'm building an RV-8, but I believe the same principle applies to most models.

Disclaimer First, DO NOT, under ANY circumstance cut the flaps until you are DEAD SURE you know what you are doing and have measured everything and also have the riblets fabricated and ready to fit. If you have already trimmed the little buggers, there may still be a solution.
I-Miguel Vidal (mvidalr), Van's Airforce Forum, website, webmaster, and owners will NOT be held responsible for which ever way you may choose to use this information, its effects and its end results.
Like all boring disclaimers: This is for informational purposes only.
You build your airplane at YOUR OWN RISK.
If you agree, then read on..

I mentioned it is an easy way, yet not so quick because you have to order 3 E-703 Elevator End Ribs (or which ever similar end rib uses your Elevator). One for the Inboard and one for the outboard sections of E-619-1-020 Trim Tab, and the third one for the inboard of the Trim Tab on the Elevator side.

Here's a visual representation of what I did:

Measure and cut each rib's tip to its final size. It is always better to cut more than the minimum, in case of any screwup.


The same goes for the Trim Tab and Elevator Skin Flaps


Deburr edges and corners.

Measure the distance where the rivet holes will be drilled. Minimum edge (margin) distance is important here, so measure according to a reliable reference, such as MIL-R-49196A.

Draw the rivet line and rivet-to-rivet distance separation (pitch) (remember to measure from rivet center)


Drill the rivet holes on the skin first. These will later be used as pilot holes to drill the riblet's rivet holes.

If you decide to attach the riblet to any Spar and it's holes (highly advisable), you will have to bend both riblet flanges and drill a relief hole for each of the bends.


Finished machining of one of the riblets. This one attaches one flange to a spar, as you can see there is only one bend. An extra 1/8" hole was also drilled at the center of the riblet web. It's used to attach a 1/8" cleco which will serve as a grip to handle and move the riblet in place.


Next thing is to position the riblet in place and hold it secure with cleco clamps. Drill/match-drill the rivet holes.

(picture taken BEFORE the relief bend and hole) It certainly looks good!

You then need to deburr and dimple the edges and holes, and prime as required and as usual.


And begin final fitting and installation.




Where regular solid rivets are hard to squeeze, Life saving MK-319-BS or CS4-4 blind rivets can be used.


Final product..



Sorry for the HUUUGE pics..
I really hope you find this information useful.
Always remember: Safety First!
Cheers!
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  #2  
Old 12-04-2012, 07:25 AM
Brad_in_Indy Brad_in_Indy is offline
 
Join Date: Sep 2011
Location: Carmel, IN
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Yeah, it seems like just about anything goes. For some reason, Van's just won't produce ribs in these areas. It's OK if you nail the bends perfectly, but get any little variation in the bends, and they stick right out.
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  #3  
Old 12-04-2012, 09:16 PM
rv8gibbo rv8gibbo is offline
 
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Location: Maitland, Australia
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I used this method to bend down the tabs with perfect results, then I done the final bend on the trailing edge but be careful not to crease the ends of the skins with the tabs when bending trailing edge down!!!

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  #4  
Old 12-04-2012, 11:18 PM
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mvidalr mvidalr is offline
 
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Default I failed twice, didn't go for a third one...

Quote:
Originally Posted by Brad_in_Indy View Post
Yeah, it seems like just about anything goes. For some reason, Van's just won't produce ribs in these areas. It's OK if you nail the bends perfectly, but get any little variation in the bends, and they stick right out.
You are right. And one thing is screwing up the trim tab (mis-alignment, creasing, uneven bending, over bending), but screwing up the elevator skin is a totally different ballgame.

One thing I'm learning from the build is how to comfront different situations with proper solutions and open your mind to new viable options.
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  #5  
Old 12-04-2012, 11:22 PM
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mvidalr mvidalr is offline
 
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Default Nice bends!

Quote:
Originally Posted by rv8gibbo View Post
I used this method to bend down the tabs with perfect results, then I done the final bend on the trailing edge but be careful not to crease the ends of the skins with the tabs when bending trailing edge down!!!
That is exactly the same way I did it, but couldn't achieve those grest results. Building an airplane is a challenging adventure. Why not make it a bit simpler whenever given the chance within the margins of safety? Specially when I certainly don't have your same craftmanship... yet
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Last edited by mvidalr : 12-04-2012 at 11:31 PM. Reason: Close quote
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  #6  
Old 12-05-2012, 03:45 AM
rv8gibbo rv8gibbo is offline
 
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Location: Maitland, Australia
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Quote:
Originally Posted by mvidalr View Post
That is exactly the same way I did it, but couldn't achieve those grest results. Building an airplane is a challenging adventure. Why not make it a bit simpler whenever given the chance within the margins of safety? Specially when I certainly don't have your same craftmanship... yet
It took 3 to get it right but with good results, It doesn't take long to discover how minor something is when the next hurdle arises. Your ribs look great!!! and good luck with the build.
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  #7  
Old 05-18-2013, 02:26 AM
xblueh2o xblueh2o is offline
 
Join Date: Apr 2011
Location: SF East Bay
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I am prepared for the manufacture of riblets, should it come to it. Part of it is the adventure.

That's about the fourth or fifth builder I have seen that has bent the edges before doing the trailing edge bend. For those who have done it, did the bent ends interfere with the final bending of the trailing edge?
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Last edited by xblueh2o : 05-18-2013 at 02:47 AM. Reason: clarification of question
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  #8  
Old 05-18-2013, 08:36 AM
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tkatc tkatc is offline
 
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I don't think the bends will interfere with the trailing edge bend as long as you don't rivet the side bends together. Make your side bends, then make your trailing edge bend. When you are satisfied, dimple and rivet.
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  #9  
Old 05-18-2013, 09:34 AM
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wjb wjb is offline
 
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Location: Half Moon Bay, CA
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Default Homebrew riblets...

After reading all the treads on this, I decided to fabricate my own with form blocks they turned out very nicely in the end, but a bit time consuming since there was a lot of learning going on. Here's a link to my adventure:

http://www.mykitlog.com/users/displa...=165210&row=22
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