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  #51  
Old 12-06-2012, 09:18 AM
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PerfTech PerfTech is offline
 
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Quote:
Originally Posted by MauiLvrs View Post
After everyone buys the ....
Wing attach support bracket
Horiz attach support bracket
Flap attach support bracket
The main gear skid

Hurry get on the list now....

The original issue could likely be fixed with a large area washer.
And that doesn't cost $54
....I could be mistaken, but it seems even for someone like yourself it would require an extremely large and very sophisticated washer to solve the problem. It would most likely need to look like ours and after you spent a few thousand on a structural analysis of your washer it may get far to expensive for anyone to afford, perhaps as much as $55. I will look foreword to seeing the magic washer that will fix or prevent this. Thanks, Allan...
.
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  #52  
Old 12-06-2012, 09:31 AM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by PerfTech View Post
....I could be mistaken, but it seems even for someone like yourself it would require an extremely large and very sophisticated washer to solve the problem. It would most likely need to look like ours and after you spent a few thousand on a structural analysis of your washer it may get far to expensive for anyone to afford, perhaps as much as $55. I will look foreword to seeing the magic washer that will fix or prevent this. Thanks, Allan...
.
Uh oh, arm chair engineer chiming in again. This part looks to have been under a lot of stress judging from the witness marks from the washer digging into the oval hole. It does not look like anything I would expect even from an over torqued bolt. Perhaps no washer was installed? Something is not right there. What do you think Allan?
Personally, I have to agree on one point at least, I don't like the idea of an oval hole. The previous models like my 6, you drilled in place. If it didn't line up without stressing it, you backed it with a filler plate.
Thanks for posting the pic.
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  #53  
Old 12-06-2012, 10:00 AM
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skylor skylor is offline
 
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Quote:
Originally Posted by JonJay View Post
Uh oh, arm chair engineer chiming in again. This part looks to have been under a lot of stress judging from the witness marks from the washer digging into the oval hole. It does not look like anything I would expect even from an over torqued bolt. Perhaps no washer was installed? Something is not right there. What do you think Allan?
Personally, I have to agree on one point at least, I don't like the idea of an oval hole. The previous models like my 6, you drilled in place. If it didn't line up without stressing it, you backed it with a filler plate.
Thanks for posting the pic.
Also, if you look closely at the end of the spar channel, it looks like no attempt was made to deburr it after it was trimmed to length. I don't think it's any coincidence that the crack in the attach bracket occurred exactly where it's laying against the sharp, un-deburred edge of the spar channel.



Skylor
Another "armchair" engineer...with an engineering degree

Last edited by skylor : 12-06-2012 at 10:03 AM.
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  #54  
Old 12-06-2012, 10:43 AM
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PerfTech PerfTech is offline
 
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Quote:
Originally Posted by JonJay View Post
Uh oh, arm chair engineer chiming in again. This part looks to have been under a lot of stress judging from the witness marks from the washer digging into the oval hole. It does not look like anything I would expect even from an over torqued bolt. Perhaps no washer was installed? Something is not right there. What do you think Allan?
Personally, I have to agree on one point at least, I don't like the idea of an oval hole. The previous models like my 6, you drilled in place. If it didn't line up without stressing it, you backed it with a filler plate.
Thanks for posting the pic.
....Vans used the oval holes so you could freely adjust the incidence on the horizontal stabilizer on the 9s without disturbing the V/S. I see nothing wrong with this other than as previously stated a large washer would be in order here. The other crack is the bigger issue to me and it is very possible you are correct about the burring issue. I didn't build the 9 that I currently fly so consequently had no control over the process. It could have many places that weren't finished properly or for that matter finished at all. I do feel if this area, considering the importance of the V/S, is that sensitive and definitely wasn't overbuilt or too strong that a little help here can't hurt. Perhaps that explains why Caterpillar doesn't build airplanes? I just feel better with it now, after the mod. With the plates and washers installed we can't conceive of this area ever being a problem. Thanks for the post, Allan..
.

.
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  #55  
Old 12-06-2012, 10:59 AM
Flying Scotsman Flying Scotsman is offline
 
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Quote:
Originally Posted by LifeofReiley View Post
Yeah... the last "engineer" I had dealings with in construction screwed everything up... went back to a common sense mode after that, everything went well with the project. YMMV....
Thanks. Your opinion of my profession is noted.
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  #56  
Old 12-06-2012, 11:19 AM
Scbado Scbado is offline
 
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Default Your Choice

Bottom line is take it or leave it. No one is making you do this mod. If you like it buy it, if not don?t buy it. Allen saw a problem and came up with a solution he believes will work. Again buy it or don?t it is all up to YOU!

Allen keep on thinking up ideas and solutions ? I like to have choices. Isn?t that a big part of EXPERMANTIAL? If I like it I will buy it, if I don?t like it I won?t buy it or I will come up with my own idea. Sure is nice to have choices. Or you can just purchase a certified aircraft and have it their way and then pull out your wallet to have the mandatory AD done at your expense.
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  #57  
Old 12-06-2012, 11:44 AM
Flying Scotsman Flying Scotsman is offline
 
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I'd *rather* know what the *actual* root cause of the failure (or incipient failure) *was*.

It's not in my nature to make decisions based on guesswork.

I've heard: overtorque; slotted hole; stress on the part due to alignment with mating part; unfinished edges; overstressed airframe; and probably a few others I can't think of at the moment.

WHAT CAUSED THIS CRACK?

Knowing THAT should drive any proposed mitigation(s).
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  #58  
Old 12-06-2012, 12:04 PM
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Av8torTom Av8torTom is offline
 
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Default Two things

When an apparent failure like this occurs, you have at least two choices of action. (i) Try and identify the cause or causes so that you can avoid them in the future, or (ii) modify the structure so that continued exposure to such "likely" causes cannot cause the part to fail. The advantage of the latter is that you don't have to know the exact cause of the failure to address the problem (and as was stated above, we can probably debate those causes ad nauseam) but can go with a hypothesis (or several hypotheses).

I think it's an excellent mod - makes complete sense. Is it the ONLY way to address the issue? - probably not, but looks good to me.


Tom
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  #59  
Old 12-06-2012, 12:14 PM
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mark schoening mark schoening is offline
 
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Quote:
Originally Posted by Scbado View Post
Bottom line is take it or leave it. No one is making you do this mod. If you like it buy it, if not don?t buy it. Allen saw a problem and came up with a solution he believes will work. Again buy it or don?t it is all up to YOU!

Allen keep on thinking up ideas and solutions ? I like to have choices. Isn?t that a big part of EXPERMANTIAL? If I like it I will buy it, if I don?t like it I won?t buy it or I will come up with my own idea. Sure is nice to have choices. Or you can just purchase a certified aircraft and have it their way and then pull out your wallet to have the mandatory AD done at your expense.
I agree wholeheartedly! I would like to think most of us building RV's have enough common sense to separate "snake oil" from good and reasonable products with out intense analytical analysis to the "nth" degree, which seems to be an excessive behaviour on this forum. You are all intelligent people, but please, after reading all the criticisms for a safety related product I need an asprin. AND, I feel no animosity towards someone who has invested time and money developing a product that makes him a few bucks----Ah, I think it's called being an entrepreneur--(not a label people look upon as "good" in this political climate) Kudo's Allen, like your product and will be purchasing!
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  #60  
Old 12-06-2012, 12:57 PM
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JonJay JonJay is offline
 
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Again, I respect Allan, his innovation, his products, etc... but I think people have a huge misunderstanding when it comes to how to deal with airframe issues, Experimental, or not.... at least in my not so humble opinion.

You can follow recommended practices, such as AC43-13-1b, or you can consult the manufacturer and follow their recommended repair or modification procedures.
AC43 makes it clear that when it comes to a spar, the only authority is the airframe manufacturer. They are a lot more lenient on ribs, web, etc...

If it was me, I would repair this per AC43-13-1b. Re-prep the parts properly elliminating the obvious burrs, stop drill the crack, and install a doubler per the thickeness called out (which for this type of repair is the same thickness as the original material). I would insure that the part is not under stress and installed properly (with a washer). I would also consult the airframe designer, Van's, to insure that my repair was "blessed". This would keep the original design intact.
After consulting a couple airframe manuals, most accept a crack that does not exceed 10% of the width of affected spar if repaired per AC43...... or per their own documented repair procedure. (they show nice drawings, mostly copied right out of AC43.....)
Some do not accept any defect in a spar period, but they are not a simple spar construction like this.

I am sorry I don't agree that "beefing up" a part is a good idea. Yes it seems obvious but you do not know if you have created a new stress point somewhere else or introduced another problem. I seriously doubt Allans product will cause any harm or introduce any stress somewhere else but that is beside the point.

People are buying the product, even after 1200 hours of operation with no apparent issue. I am fine with that, but let's make sure everyone is educated on what "normal" procedures, in my opinion, should be. It is not strapping on a fix that has not been analyzed. (If it aint broke, dont fix it.)

I do not believe any manufacturer, supporter of Doug's or not, is immune from question, especially when they agressively market on this site. Allan has been good to address the questions. I thank him for that. I also believe Allan is the type of person who can agree to disagree. I hope his loyal supporters can do the same. My flame suit is warn out, but I must say I have kind of enjoyed it!
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