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  #21  
Old 02-18-2014, 04:17 PM
kblack kblack is offline
 
Join Date: Mar 2008
Location: Granbury, Tx
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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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  #22  
Old 02-18-2014, 06:44 PM
eddieseve eddieseve is offline
 
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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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  #23  
Old 02-18-2014, 06:48 PM
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Snowflake Snowflake is offline
 
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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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  #24  
Old 02-18-2014, 08:57 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Snowflake View Post
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).
I couldn't have said it better myself.
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  #25  
Old 02-18-2014, 09:27 PM
Frank Smidler Frank Smidler is offline
 
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Location: Stoughton, WI
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Default Also agree

Quote:
Originally Posted by rvbuilder2002 View Post
I couldn't have said it better myself.
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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  #26  
Old 02-18-2014, 10:32 PM
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PerfTech PerfTech is offline
 
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Smile 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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  #27  
Old 02-18-2014, 11:09 PM
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Walt Walt is offline
 
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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.
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  #28  
Old 02-18-2014, 11:20 PM
jongurley jongurley is offline
 
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Location: North Carolina
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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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  #29  
Old 02-19-2014, 03:56 AM
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JanRV6UK JanRV6UK is offline
 
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Factory fix all the way .... No question ...
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  #30  
Old 02-19-2014, 04:14 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by JonJay View Post
Fair enough Dan. However, they did acknowledge that it was done. I misstated that and appreciate the correction.
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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Last edited by DanH : 02-19-2014 at 04:39 AM.
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