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NEW V/S Modification video Anti-Splat-Aero

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....:eek:

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...:rolleyes:
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CRACK.jpg
 
....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...:rolleyes:
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CRACK.jpg

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.
 
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.

CRACK.jpg


Skylor
Another "armchair" engineer...with an engineering degree
 
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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..:D
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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. :eek:
 
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).
 
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
 
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. :eek:

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!
 
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!
 
If nothing else, if someone gets in a thunderstorm area, by serious mistake, and wings are falling off some of them certifieds..........perhaps the extra strong RV tail (with Anti-Splat), will stay where it belongs.
 
Allen - I have a -12 and (so far) you have no products for it - but I am GLAD you are there! Keep it up.
 
Allen - I have a -12 and (so far) you have no products for it - but I am GLAD you are there! Keep it up.

...Thank you bill! The Vans aircraft are so good and very well designed they have few issues, this makes it somewhat difficult to come up with products. We haven't had access to a 12 and have had very few suggestions for products. The one thing that we were looking to build if the interest was great enough, was a foam filled custom fuel cell like the ones we build for our race cars to replace the stock gas tank. I was talking to a 12 owner that wanted this and he was convinced most other 12 owners would be interested as well. I guess I sort of dropped the ball and got busy with other projects. Perhaps we should re-visit this and if you have need for or have a product idea please post it as we are always interested. Thanks, Allan...:D
 
Allan
Re RV-12 fuel tank.
I would suggest you post that idea on the RV-12 area.I suspect youwould find interest from some at least.
The only thing I would ask is is there a risk over time of foam migration/ disintegration ie a need at a certain time to replace the foam electively?
However, i don't want to ask this question on this thread and potentially hijack it!

John
 
...................... 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..

Unless I am mistaken, (which is a distinct possibility), AC-43, and any other literature you can name, is not mandatory for experimental amateur built (EAB) aircraft. And Van's Aircraft is not the manufacturer, either.

Van is a kit supplier. The manufacturer is the builder.

**Please note that I am NOT suggesting that AC-43 be ignored, and that Vans shouldn't be contacted. Both are excellent sources of information. Just putting a fine point on the issue.
 
I think this comes down to a business model. If your entire model is based upon finding problems with a known successful product, you MUST find new dangers (real or imaginary) to apply your "expertise" to...otherwise your bank account shrinks. The problem, of course, is that you must find fault with a design that is very proven....which leads to resistance.

I suppose one could call to have any who resist his assumptions banned...that could work. Certainly easier than learning analysis of forces or mechanics of materials, but doesn't really go along with the notion of a public discussion forum.
 
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Unless I am mistaken, (which is a distinct possibility), AC-43, and any other literature you can name, is not mandatory for experimental amateur built (EAB) aircraft. And Van's Aircraft is not the manufacturer, either.

Van is a kit supplier. The manufacturer is the builder.

**Please note that I am NOT suggesting that AC-43 be ignored, and that Vans shouldn't be contacted. Both are excellent sources of information. Just putting a fine point on the issue.

You are correct on all points. Vans is the aircraft designer, so substitute that for manufacturer as that is the intent. I use Ac43 as the repair procedures and standards have been engineered by someone at some point and have stood the test of time.

Experimental is just that. You can do almost anything you choose. However, just because you can doesn't mean you should.

Many repair, riveting, torque, etc... type questions I have seen that get posted here often can be answered by reviewing AC43-13-1b.
There are other good resources too.

Point well taken.
 
Good news for you Allen, this controversy has generated your business close to 6700 views!!!! May be an excellent marketing strategy to use from now on. Thanks for doing the work you do.
 
I think this comes down to a business model. If your entire model is based upon finding problems with a known successful product, you MUST find new dangers (real or imaginary) to apply your "expertise" to...otherwise your bank account shrinks. The problem, of course, is that you must find fault with a design that is very proven....which leads to resistance.

I suppose one could call to have any who resist his assumptions banned...that could work. Certainly easier than learning analysis of forces or mechanics of materials, but doesn't really go along with the notion of a public discussion forum.

...First of all our business model is not based on finding problems with a trouble free successful product. We tackled a well known gear issue that was of concern to many when using their aircraft on unimproved surfaces and very well documented in incident reports. We were the only ones willing to do the research, spend to time, effort and make the sizable investment in finding a viable solution. We didn't find the problem, it found us via requests. Most of the products that ASA offers are accessories, tools etc. As for the statement of my bank account shrinking, believe me that isn't a problem. We donated far more to charity last year than ASA total sales. ASA is a very small side line for us (just 1% of sales) and I do it for enjoyment, an excuse to fly, camaraderie, (99.9% of RVers are great people) and it also allows us to wright off all our airplanes, flying, fuel, hangers, insurance etc.
...Our primary business is manufacturing turbine engine parts, turbine blades, hot sections, turbo-compressors and related parts for the worlds largest turbine engine manufacturer. Our materials knowledge, engineering expertise and quality control are good enough for Garrett and are well documented. The insinuations made here are definitely out of place in this forum and completely unsubstantiated.You are correct! This is a public forum, but not a place to defile, demean or make false statements as factual information...:confused:
 
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We were the only ones willing to do the research, spend to time, effort and make the sizable investment in finding a viable solution. We didn't find the problem, the FAA did. :

Allen,
I support you in the context that unsubstantiated insinuations have recently been made against you... inappropriate for the VAF forums, but I will also take the opportunity to point out that you are doing the same with the above statement.

I am not aware of a single NTSB RV "A" model accident report (the FAA has nothing to do with accident data reporting BTW) where the probable cause lists the nose gear design as faulty.
 
Allan - Although we have a fundamental difference in what I believe is acceptable for modifications and repairs of airframe components, our discourse has been civil, albeit a bit contentious at times. However, others on both sides of "the argument" have been less than kind. I hope I am in that 99.9%. :)
 
Allan - Although we have a fundamental difference in what I believe is acceptable for modifications and repairs of airframe components, our discourse has been civil, albeit a bit contentious at times. However, others on both sides of "the argument" have been less than kind. I hope I am in that 99.9%. :)

....Yes Jon! You are definitely in that 99.9% and I commend you for saying what you believe. That is what makes this all work. Thanks, Allan...:D
 
Allen,
I support you in the context that unsubstantiated insinuations have recently been made against you... inappropriate for the VAF forums, but I will also take the opportunity to point out that you are doing the same with the above statement.

I am not aware of a single NTSB RV "A" model accident report (the FAA has nothing to do with accident data reporting BTW) where the probable cause lists the nose gear design as faulty.

.....Yes Scott, you are correct and thank you for pointing this out to me as this was not my intention. What I intended to say was the incidents were documented by the FAA and that was where I got many photos and information I considered when trying to help prevent future incidents. Nothing I saw indicated the gear leg was faulty or for that matter the cause or even a contributing factor. The problem is mostly pilot technique and the environment that the gear legs were subjected to. The vast majority of small, fast aircraft with small wheels aren't landing on grass and golfer holes. Just think of what the statistics would look like if lancairs and Ceruses were landing where RVs land regularly. I in no way feel it was a design flaw or a blemish on the Vans organization and will defend them wholeheartedly. I sincerely wish to apologize for not stating this properly in my former post. I will attempt to edit and correct it. I don't want to be in that .1%. Thanks again, Allan.....:eek:
P.S. Below are the links to information that I was referring to when I made the incorrect statement.
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http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20051006X01588&key=1



http://www.ntsb.gov/doclib/reports/2006/RV_study.pdf



http://www.ntsb.gov/doclib/reports/2006/RV_PHOTOS.pdf
 
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Tail Reinforcing-M35 V-Tail Bonanza

My formerly owned N9859R had a reinforced V-Tail modification that made me feel only a little better about turbulence, and I cannot recall any reluctance on anyone's part to try to make sure these tails did not depart the aircraft.

But depart they did, and eventually the FAA took action despite many opinions that the original design was adequate and that the pilot induced the tail departures by exceeding the engineered design strength of the assembly.

I think Allan might be onto something here. My non-engineer view has been that IF there were any weaker area of my RV6, it would be the tail. Maybe it is the hours worrying about my Vtail, but it does cross my mind occasionally in rough air.

BTW I replace my 6 entire tail assembly after inadvertently decoupling the autopilot in cruise, stupidly, without holdng the stick, and I zoomed almost straight up because the trim was not where it should have been. The autopilot overcame that trim setting and I was not aware. It rippled the skins of my elevators, both, but the tail held on fine. The part Allan is reinforcing was not obviously damaged, nor did I expect it to be from that maneuver.

My replacing it all should help convey how important I think my tail is.

My 2 cents. Flame Suit On.

Montanamike
N918MB RV6 O-360
 
Vert. Stab. Mod. / AntiSplatAero

Allen, great speaking with you on Thur. 12/6 regarding your latest product, Vert. Stab. Mod. Received it on Monday installed that night, DONE in 30 minutes. You were right perfect fit for rivet and hole alighment. Plus you can just feel how tough this stainless steel is, I dont think I have a drill bit in the tool chest to put a hole in it.. This is all about peace of mind, in 10,000 hours you shouldnt see stress cracks in the Vans stock part. The mod is a no brainer as I continue the build. Thank you sir!!
Mark C. 119RV
 
Allen, great speaking with you on Thur. 12/6 regarding your latest product, Vert. Stab. Mod. Received it on Monday installed that night, DONE in 30 minutes. You were right perfect fit for rivet and hole alighment. Plus you can just feel how tough this stainless steel is, I dont think I have a drill bit in the tool chest to put a hole in it.. This is all about peace of mind, in 10,000 hours you shouldnt see stress cracks in the Vans stock part. The mod is a no brainer as I continue the build. Thank you sir!!
Mark C. 119RV

...Thank you for the heads-up on the parts and we are glad to see you are pleased. If you or anyone else sees a way to improve any of the products or have a suggestion for a new one, please let us know. Thanks, Allan...:D
 
I just stumbled across this part, and was wondering if it will cause any problems to a magnetometer/GMU44 mounted on the rear deck just forward of the vert stab.

I had some concerns about the strength of the vert stab attach bracket after I mounted mine, I don't think the bottom row of rivets has enough edge distance, and this seems to satisfy some of my concerns.
 
I just stumbled across this part, and was wondering if it will cause any problems to a magnetometer/GMU44 mounted on the rear deck just forward of the vert stab.

I had some concerns about the strength of the vert stab attach bracket after I mounted mine, I don't think the bottom row of rivets has enough edge distance, and this seems to satisfy some of my concerns.

.... The stainless parts are non magnetic so I don't believe the would have any effect on your equipment. The standard bolts that are used in this area from vans are steel and don't appear to cause any problems, I think? Thanks, Allan....:D
 
.... The stainless parts are non magnetic...
Not all stainless is non magnetic ...


BTW are you going to make a support bracket to reinforce the all aluninum horiz stab attach parts with SS. Ya know it might just break ... :eek:

Even the bird thought that was funny...
 
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Wow. Allan, I just read this entire string. It seems that Dave and Trina have it out for you. I think you stated that Your SS Part is non magnetic. Thanks Dave and Trina for pointing out an irrelevant fact that not all SS is non magnetic. This guy has subscribed to the thread for seemingly the sole purpose of attacking every time the subject comes up.

For the record, I probably will not be buying this part because I am not convinced it is necessary. Others who disagree are welcome to do so. I will, however, be buying several others that you are making. Please keep up the good work! We need folks like you that are constantly looking for ways to improve the safety on our planes. If we keep this up we MAY get to keep our flying freedoms.
 
Oh yeah...Dave and Trina, you already made the joke about the wing attach bracket back on page 6. I doubt it gets funnier a second time. The bird is probably laughing in pity, not humor.
 
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Installed Last Night

I got my empenage bolted up this weekend and installed the mod last night. As simple as it was to install; i cant think of a reason not to. Extra piece of mind when i kick this thing into a side slip. It took less than an hour, and that included an extra step of removing each piece for deburring the holes and clearing out the aluminum shavings from drilling the holes.
 
Not all stainless is non magnetic ...


BTW are you going to make a support bracket to reinforce the all aluninum horiz stab attach parts with SS. Ya know it might just break ... :eek:

Even the bird thought that was funny...

WOW! look what I found, Not that funny now with the new SB!
 
tiresome

I installed the stainless before all this hot headed chatter showed up on my computer. Well engineered, easy to install and low cost. I somehow get the impression that someone at their keyboard wants desperately to be the smartest guy in the room. Anyone know how to make my leg less tired when I slip hard now?
 
Cracks

I for one would like to thank Allen for his selfless time and effort in addressing this crack problem. I didn't see anyone else even suggresting an alternate "fix" for the problem. I bought and am thoroughly enjoying my -8 in these latter years of my life. I am not an engineer nor a designer, I just love to fly and am grateful for people like Dick VanGrunsvn and Allan Nimmo that have contributed so much to the Experimental Aircraft industry and this fantastic aircraft that we all enjoy so much. The key word here is experimental which means trying new things and making things better. That's why we fly RV's instead of certified aircraft that are mired in bureaucracy.
We will have more cracks in the years ahead and I hope Allan and those like him will be looking over us. Meanwhile lets enjoy that which we share in common......that RV Grin.
 
AntiSplat Horz Stab Mod

So, for those of you that put Allen's mod on the Horz Stab, I have some questions:

1. Did you have to remove the Horz Stab (Actually the whole tail) to do this mod?

2. How long did it take you?

I have an RV-7A that I'd like to do this mod too, and need to schedule some down time.... I also have another friend with an RV-7A that wants to do the same mod, and another friend with an RV-6A that want's to do this mod... So we're all interested in hearing some answers...

I for one would like to thank Allen for his selfless time and effort in addressing this crack problem. I didn't see anyone else even suggresting an alternate "fix" for the problem. I bought and am thoroughly enjoying my -8 in these latter years of my life. I am not an engineer nor a designer, I just love to fly and am grateful for people like Dick VanGrunsvn and Allan Nimmo that have contributed so much to the Experimental Aircraft industry and this fantastic aircraft that we all enjoy so much. The key word here is experimental which means trying new things and making things better. That's why we fly RV's instead of certified aircraft that are mired in bureaucracy.
We will have more cracks in the years ahead and I hope Allan and those like him will be looking over us. Meanwhile lets enjoy that which we share in common......that RV Grin.
 
ASA HS Mod

I am also about to install Allan's vertical and horizontal mods and I am interested in the same questions. To install both mods (4 pieces), do I have to remove the HS from my RV7? I understand from the video that to do the VS, I leave everything but the fairing installed, Looks to me, though, in the video of the HS mod installation, the HS is on a bench but I can't see why it had to be removed. Thoughts?
 
I have a coup,e of comments after reading this rather strange thread. I am an aero eng with over 20 yrs experience.

For those who scoff at engineers, van is an engineer and without that skillset there would be no RVs. Period.

We are not talking about an over load issue here. It is a cracking issue so it is fatigue. Fatigue analysis is at best a rough estimate as every airplane is built and flown a bit different. The designer is always walking a fine line between keeping it light and providing adequate fatigue life.occasionally a week spot shows up after many hrs on many aircraft. This is the case for all aircraft including Boeing, Airbus and any military or recreational aircraft. So this is not an indictment of Van, it is a normal occurance. That is why we do inspections. And Vans aircraft have had several of these situations on various models.

AC 43.13 is an Advisory Circular. An AC is an acceptable means of compliance, not a mandatory standard. Mfgs can and do deviate if they can show justification. A mandatory instruction is an Airworthiness Directive.

This SS beefup from ASA is not to increase the static strength, which is adequate in the initial design, it is there to increase the fatigue life. And the designer is not stating that this is the critical load point on the Vstab. It is simply a location where cracks are known to form for the reasons stated above.

So you can inspect and repair as per the AC or you can take these conveniently made parts and increase the fatigue strength and most likely never have to worry about cracks forming and it will involve less work than a repair. Or, you might put 10000 hrs on your airplane and never need it. It depends on where and how you fly, how much power you have up front etc etc.

As for all the other surface mounting points, if there has been no service history of cracks forming there would be no need for any modification. So suggesting that installing a beefup on the vstab mount is the same as beefing up every other part of the airplane just doesn't make any sense.

This part has been offered as a service to the community in good faith and we are all free to take it or leave it.
 
This part has been offered as a service to the community in good faith and we are all free to take it or leave it.

Very good point.

The problem with that is that within this community, 99.9+ % of the people don't have your aero engineering background (or any engineering for that matter), so taking it on faith is about all they have.

Sometimes that works.... some times it doesn't.
 
AC 43.13 is an Advisory Circular. An AC is an acceptable means of compliance, not a mandatory standard. Mfgs can and do deviate if they can show justification. A mandatory instruction is an Airworthiness Directive.

Yes and no. A manufacturer is never required to do anything in AC43.13. On the contrary, AC 43.13 is an acceptable means of compliance only in the absence of manufacturer's guidance. Nothing in it can be substituted for manufacturer's guidance. From the seldom-read very first page:

This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions.

Confirmation was direct from the top, FAA AFS-300 in DC, the office responsible for AC43.13.

This SS beefup from ASA is not to increase the static strength, which is adequate in the initial design, it is there to increase the fatigue life.

Given hard analysis, does it in fact increase fatigue life? Or is it the classic eyeball design beef-up, many of which may worsen or relocate the fatigue issue?
 
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Yes and no. A manufacturer is never required to do anything in AC43.13. On the contrary, AC 43.13 is an acceptable means of compliance only in the absence of manufacturer's guidance. Nothing in it can be substituted for manufacturer's guidance. From the seldom-read very first page:

This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions.

Confirmation was direct from the top, FAA AFS-300 in DC, the office responsible

Totally agree. It is Advisory only. I don't see anything in your post that contradicts what I said.

As for a eyeball beefup, if you have a crack and stop drill it and put a patch on it as per 43.13, that's exactly what you will have, an eyeball beefup.

Anytime you beef up an area you are likely going to make some other area fail first. Rare is the structure where every single part fails simultaneously. But as long as all the parts stay within the static and fatigue load envelope you'll be ok.
Suggesting that putting this part on is going to weaken some other part of the airplane is pretty far fetched.

Now if Van comes out and tells you to do something different then that's another story.
 
Now if Van comes out and tells you to do something different then that's another story.

That is exactly what happened with the horizontal stab, actually. Van says one thing, AntiSplat says "no, that's too complicated - here's another piece of SS to use instead".
 
Given hard analysis, does it in fact increase fatigue life? Or is it the classic eyeball design beef-up, many of which may worsen or relocate the fatigue issue?

I do fatigue analysis on aircraft structures for a living, primarily for repair work due to things like cracks and shop errors. Dan as usual you make valid points. Yes this is an eyeball design and all it is going to get is an eyeball analysis (from me anyway). I have no dog In this fight, just giving my objective observations. Looking at the damage picture earlier in this thread I think it is obvious that the root cause is as stated, the bracket was bearing on a sharp edge, probably with some misalignment preload caused by improper shimming, causing a crack initiation, further irritated by the typical flight loading. The crack did show up in the right spot from a load path perspective. I honestly don't like the design of the original vans bracket, from an installation perspective, because of the tolerance stackup involved, which leads to installation misalignments that are hard to overcome, especially for more novice types or know it all types of builders. Likewise, the splat bracket is pre-bent and again you are matching angles that are different on every aircraft, causing preload situations unless carefully dealt with. Also the new bracket is dependent upon frictional clamp up to remove loads from the original bracket. I'm not trying to give an answer, just raising the points that a room full of fatigue engineers might raise. There are other points to be made, but I will stop here for now.

As a note, good fatigue analysis requires sound experience, judgment, and often test data that helps quantify loads and unforeseen load paths. I make no claims that I have the experience or judgment to approve or disapprove the design. In my experience, the loads used to analyze a part are developed from a very involved process of instrumentation and test, and correlation of the them with an FEA model. (I mean, putting strain gauges on an aircraft or structures in a test rig, and then comparing the resulting strains with a finite element model). With that you can make more meaningful calculations of fatigue life.
 
Asa mod

So, if I have no cracks in my h/s and I install the ASA patch, AND keep flying the same minimal occasional aerobatics, have I made anything worse?
 
So, if I have no cracks in my h/s and I install the ASA patch, AND keep flying the same minimal occasional aerobatics, have I made anything worse?

That's really what it comes down to. With the case of the ASA patch, nobody really knows since it's essentially a guess as to whether it actually mitigates a potential issue or simply moves a fatigue problem somewhere else.
 
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