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02-18-2014, 04:17 PM
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Join Date: Mar 2008
Location: Granbury, Tx
Posts: 30
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I am an engineer, but not structures. The AntiSplatAero fix may be fine. However, I suspect part of the reason for the shape of the Van's doubler (someone called it "swallow tail") is to spread the reinforcement over a larger area and reduce the chances of concentrated stress leading to a crack in a new location. In this case, there may be little chance of a new crack location due to a doubler. I don't know. Maybe a structures guy can comment?
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Kliff
Granbury Texas
RV-7 QB (N74KB) - Flying
RV-10 QB - Empennage Started
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02-18-2014, 06:44 PM
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Join Date: Mar 2009
Location: Sydney, Australia
Posts: 617
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Hi Allan
What is the price of these parts, can't find it on your website
Cheers
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Eddie Seve
Sydney Australia
First Flight 16th July 2012
RV-7 Phase 2, 30 Oct 2012
1100 hrs Feb 2020
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02-18-2014, 06:48 PM
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Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
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As an aeronautical engineer, this mod raises concerns in my mind from a number of angles.
1. The reinforcing plate ends on the hidden side of the shear web of the rib. That not only makes a stress concentration, but it does it *just* out of sight... Very hard to inspect in the future. The Van's SB has dovetails that extend out and taper, distributing load and reducing any stress concentrations.
2. The mod requires "making space" between the rib and the spar. "Just stretch it" is horrifically bad engineering advice. Bending the flange further to make room will result in the existing rivet holes in the flange not lining up with the existing holes in the spar. If you flex the shear web enough to get the flange back into place, you preload the corners at the front of the rib, that have the same geometry as the corners that were cracking on the horizontal stab originally. Is that really what you want? (as an aside, I found a crack in this rib right at that exact corner as a result of the SB inspection)
3. Galvanic corrosion, previously mentioned. Passivating will improve the situation, but it won't alleviate it entirely.
4. Resale. Factory approved fix with factory supplied parts = Service bulletin complied with, signed off, and no further inspections required = warm fuzzy feelings in prospective buyers. Aftermarket fix with aftermarket parts = unknown.
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Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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02-18-2014, 08:57 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by Snowflake
1. The reinforcing plate ends on the hidden side of the shear web of the rib. That not only makes a stress concentration, but it does it *just* out of sight... Very hard to inspect in the future. The Van's SB has dovetails that extend out and taper, distributing load and reducing any stress concentrations.
2. The mod requires "making space" between the rib and the spar. "Just stretch it" is horrifically bad engineering advice. Bending the flange further to make room will result in the existing rivet holes in the flange not lining up with the existing holes in the spar. If you flex the shear web enough to get the flange back into place, you preload the corners at the front of the rib, that have the same geometry as the corners that were cracking on the horizontal stab originally. Is that really what you want? (as an aside, I found a crack in this rib right at that exact corner as a result of the SB inspection).
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I couldn't have said it better myself.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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02-18-2014, 09:27 PM
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Join Date: Feb 2005
Location: Stoughton, WI
Posts: 473
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Also agree
Quote:
Originally Posted by rvbuilder2002
I couldn't have said it better myself.
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The modulus of the SS is much higher than aluminum. This means that the loads will transfer into the stiffer SS plate from the aluminum immediately where attached thus causing a stress riser that may in fact increase the potential for aluminum cracking.
Another Engineer with aluminum structure design and testing experience.
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Frank Smidler
N96FS, RV-6
Flying 1/11/09
1085 hr
2WI6 Stoughton, WI
Formally of Lafayette, IN
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02-18-2014, 10:32 PM
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Join Date: Sep 2010
Location: Redlands, Ca.
Posts: 1,458
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I said it before!
... As I said, this may not be for everyone and obviously I was correct. As Clint Eastwood expressed so elegantly, "A mans gotta know his limitations" I guess many do not share these views as we have sent out all but a few of our first run of this part. The $25 cost and ease of installation looks very attractive to many and we have been inundated with calls, e-mail and orders. It seems that mixing the pot is good for everybody. Thanks, Allan... 
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Allan Nimmo
AntiSplatAero.com
Innovative Aircraft Safety
Products, Tools & ServicesInfo@AntiSplatAero.com Southern California (KREI)
RV-9A / Edge-540 
(909) 824-1020
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02-18-2014, 11:09 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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I normally try to refrain from entering discussions like this but what the heck, my wife tells me all the time I don't have any "filters" since retiring so I'm gonna throw my 2c in here
I would highly recommend owners just bite the bullet and install the Van's approved SB with no deviations and do it exactly as written. I've seen quite a few major repairs in my day and the Van's fix looks like what I would expect a typical repair to look like. On the other hand, Alan's repair does not even follow what I would consider to be standard practice from 43-13.
I appreciate the effort and ingenuity that Allan put into this, but this is not a mod/fix I would endorse.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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02-18-2014, 11:20 PM
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Join Date: Dec 2011
Location: North Carolina
Posts: 94
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If im riding in it. Ima listen to factory. simple as that. and price point doesn't matter in the event of life or death.
Last edited by jongurley : 02-18-2014 at 11:46 PM.
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02-19-2014, 03:56 AM
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Join Date: Jul 2009
Location: England
Posts: 470
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Factory fix all the way .... No question ...
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Jan
Slooow RV6, no hole, builder in UK
Paid up for 2015 ...
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02-19-2014, 04:14 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by JonJay
Fair enough Dan. However, they did acknowledge that it was done. I misstated that and appreciate the correction.
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Good man....and like you, I fully believe them. Let's just remember that believe is the operative word. Trusting any manufacturer without disclosed data is a belief system, not a decision made on fact. It is usually all we have. Again just to be precise, a fully qualified engineer designed the spar in question and considered it adequate. Same is true for V-35 tails, yes? It's really a game of probabilities.
Returning to point, I'm not a professional engineer, but I have studied enough fundamentals to understand the issues in this case. Please see comments from Rob and Frank. Put politely, the Vans doubler design is the superior choice.
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Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 02-19-2014 at 04:39 AM.
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