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H/S Spar Mod Slide Show from A.S.A Now Up!!!

PerfTech

Well Known Member
... We now have parts available and a small slide show up for viewing on our website, http://antisplataero.com/Videos.html showing the fix we have created for the H/S spar crack issue. The slide show also gives some basic information as to installation and what is involved to compare with the other method that is available. This mod is somewhat less intrusive, and for that reason may appeal to many. If you like what you see and want more information just give us a call. Thanks, Allan... :D
 
Allen, I have a problem getting any audio on the slide show,volume is way too low,so I missed the explanation on why there is no finger extending to the top and bottom of the rib flange?
 
Any data?

Can we get some engineering data that shows this fix is at least as good as the one Vans has approved? I know stainless steel is stronger than aluminum, but I would sure like to see some of that element analysis mojo to show the spar will be stronger and that this particular patch will prevent crack propagation and spar failure.
 
Audio Problem

Allen, I have a problem getting any audio on the slide show,volume is way too low,so I missed the explanation on why there is no finger extending to the top and bottom of the rib flange?

....Sorry Guys!!!!
Something must have gone crazy when it was uploaded. I will have my computer whiz address this as soon as he comes in today. Again "Sorry for this issue". Thanks, Allan...:eek:
 
Maybe it's me - the recording volume seems so low that on playback it's pretty much impossible to hear what's being said during the presentation.

Dan
 
Audio

I listened to it my Mac and the audio was fine.
Would also like so engineering type data that this fix is equal to or better than Van's.

To my untrained eye, it looks good and is very creative.
 
Well - tried it on two PCs and on a iPad and the result is the same. Lead in music is fine, the voice over is muted to the point of not being able to hear it.

Dan
 
I heard it, but had to go to max volume on the computer.

Here is my $0.02

To me as a non engineer type, the mod looks good------I like the fact you can still see the area where the cracks are occurring in the spar, so you can monitor the condition of things.

Looks to be much easier to install that the factory setup, but as has others folks have mentioned, is there any data to verify the setup?

If I had a plane subject to this SB, I would most likely install this as a preventive measure if there were no existing cracks-----and the factory setup is there were existing cracks.

Good job Allan.
 
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I am sure you address this in your repair, but you will need a layer of pro-seal in between the stainless and aluminum to prevent/minimize dis-similar metal corrosion. There are other issues related to the use of stainless the people may want to think about before using it as well.
 
OK! Fixed!

.... We boosted the audio and uploaded it again. You can hear it now but audio is not as good as it should be. Again, sorry for the delay. Thanks, Allan.:eek:
 
If I had a plane subject to this SB, I would most likely install this as a preventive measure if there were no existing cracks-----and the factory setup is there were existing cracks.

Good job Allan.

What if you had a crack later, after you installed this. Making this area stronger without carrying the load into the rest of the structure might move whatever stress is causing the crack to someplace else. Might....

Thus far, there has been no evidence, engineering, study, modeling or anything else to assume that this will reduce the chance. Many people have asked, but no answer...
This has been the same as the other mods from Alan. We have had this discussion before. So, as Alan says, this may not be for everyone.....

If you believe it will fix it based on your own intuition and "common sense", it might be for you. I prefer to see the engineering data behind airframe modifications before I make a decision, just like the factory did for their only approved SB mod.... but that is just me.

I mean no disrespect to Alan and anyone who wishes to support him and his company. I simply won't modify the basic airframe without substantial engineering data to show I am not doing more harm than good. I don't trust myself to know....
 
What if you had a crack later, after you installed this.

I would probably build a new stab which would have the factory fix in it.

Making this area stronger without carrying the load into the rest of the structure might move whatever stress is causing the crack to someplace else.

Exactly my thoughts, which is why I made the distinction between installing it in my theoretical airplane based on if there was already a crack. The factory fix has the swallow tail extensions riveted to the spar, and this one does not. I do recognize the difference and the possible effect------but I do not have the training/knowledge to asses this difference.

The factory fix.

12524182143_aa47f8404e_c.jpg


The Anti Splat device.

watch
 
A little more info!!!!!

I am sure you address this in your repair, but you will need a layer of pro-seal in between the stainless and aluminum to prevent/minimize dis-similar metal corrosion. There are other issues related to the use of stainless the people may want to think about before using it as well.

... This product is made of 301 stainless and this is austentic rather than martensitic material. These parts also go through a process after completion to help stop galvanic corrosion. The process, called "passivation,"this in conjunction with the choice of material virtually cancels the corrosion concerns. I do however recommend a film of dielectric grease on the mating surfaces before final assembly and riveting. This is just in case one surface is somehow contaminated and adds a little extra insurance were that the case. This material is widely used throughout the aircraft industry for highly stressed parts where strength is required. I will include here a materials specification sheet for those interested. Thanks, Allan...:D
.
 
I would probably build a new stab which would have the factory fix in it.

The factory fix has the swallow tail extensions riveted to the spar, and this one does not. I do recognize the difference and the possible effect------but I do not have the training/knowledge to asses this difference.

The factory does not recommend, nor do the many mechanics and builders who have chimed in, building a new HS. It would be very difficult to match drill a new HS to an existing airframe.

In regard to your second comment, me either. I will trust the one that has done the engineering.....

Like Alan said, his product might not be for everyone.... I think you know where I sit on the fence.

By the way, I have bought some of Allen's products. I just won't buy un-engineered airframe components from anyone... I have nothing against his company or him....
 
I have nothing against his company or him....

Me either, and I did enjoy talking to him at the last Homecoming.

I am just rendering an honest, and unasked for opinion, about hypothetical questions to an aircraft I do not even own------mental masturbation at its best;)
 
Me either, and I did enjoy talking to him at the last Homecoming.

I am just rendering an honest, and unasked for opinion, about hypothetical questions to an aircraft I do not even own------mental masturbation at its best;)

Funny. How did you get that word past the filter.
 
I prefer to see the engineering data behind airframe modifications before I make a decision, just like the factory did for their only approved SB mod.... but that is just me.

To be perfectly precise, Vans has not shown anyone their engineering work either.
 
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To be perfectly precise, Vans has not shown anyone their engineering work either.

Fair enough Dan. However, they did acknowledge that it was done. I misstated that and appreciate the correction.
 
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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?
 
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.
 
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.
 
Also agree

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.
 
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...:D
 
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 :D

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.
 
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.
 
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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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Are some people just hoping for a short cut for fear of drilling out a few more rivets? You already took the tail off, how about spend a few more hours and actually comply with the SB. Vans for me!
 
I'm not taking a stand either for or against since I don't have a dog in this fight but it would be interesting to know if a simulation for testing this part/material could be performed to see if it is as suitable as Vans.

But Van's would be the one to do this and I seriously doubt that will happen.

Glenn Wilkinson
 
Galvanic corrosion between stainless and aluminum always ends up with aluminum being sacrificially corroded. Stainless is the more "noble" material. Passivating the stainless help nothing to prevent this, if anything it will make the matter worse. This is only a problem in marine environments. Without salt the combination of stainless and aluminium is perfectly safe.
 
Galvanic corrosion between stainless and aluminum always ends up with aluminum being sacrificially corroded. Stainless is the more "noble" material. Passivating the stainless help nothing to prevent this, if anything it will make the matter worse. This is only a problem in marine environments. Without salt the combination of stainless and aluminium is perfectly safe.

Exactly. Passive 301 stainless is further away from 2024 Aluminum on the galvanic series than active 301 stainless. Meaning greater galvanic potential and corrosion risk.
 
HS

I wonder why these cracks started in the first place if the engineering and stress tests where done?
 
Not an exact science

I wonder why these cracks started in the first place if the engineering and stress tests where done?

Because engineering is not an exact science and not every calculation results in the exact answer. Too many variables. Kinda of why their are test pilots:D
 
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 :D

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.


But do we prime the SB parts??? :D:D:D
 
Speaking of the possible galvanic action of stainless and aluminum...
What is our firewall made of again, and what fasteners do we use to rivet them on with? Is this really an issue? Someone is offering a substitute, take it or leave it but don't bash him for offering it.
 
Speaking of the possible galvanic action of stainless and aluminum...
What is our firewall made of again, and what fasteners do we use to rivet them on with? Is this really an issue?

If it is an issue or not depends on where you are going to fly. Galvanic corrosion problems in aluminum is generally no issue at all, or only a minor issue. However, in marine environments, galvanic corrosion problems is THE issue of ALL corrosion issues. This is common knowledge to every boat owner (salt waters), and to the US Navy.
An estimated 90% of corrosion damage to our F/A-18 aircraft is due to galvanic interactions
The point is that galvanic corrosion, if left to develop, can destroy parts within a few months close to the sea, days even. Still, only a few miles inland and the problem is non existent.

The combination of aluminum and stainless is a special case, this combination is 100% safe away from the sea (no salt). These alloys will not interact in fresh water environments even though the galvanic potential between them is larger than aluminum and copper. In a marine atmosphere they will interact instantly where aluminum will corrode rapidly.

Besides, 301 stainless will not last long in a marine environment if left untreated, passivated or not. It is definitely not a metal you would ever put on the deck of a boat (316 stainless and lots of other alloys are made for marine use). Untreated 6061 aluminum will last for years and years in marine environments, but connect it with a piece of 301 stainless and corrosion starts within days. I have a test piece of 6061 riveted with 304 stainless using various protection methods that will be permanently fitted to my boat for some years, just to see how it develops.

Corrosion of aluminum is entirely decided by the environment. Practically speaking it is a problem that exist exclusively for marine environments. Inland, the problems are virtually non existing.
 
I wonder why these cracks started in the first place if the engineering and stress tests where done?

Because the engineers didn't build it. Amateurs did, and amateurs tend to do things like just stretching it to fit. I don't mind an amateur building my airplane as long as a professional, qualified and proven engineer designed it. Notice that very small cracks have been found in very few planes. Professional enineering.

What causes me great concern is people talking about modifying a structural member designed to flex by putting a nonflexible material in it. Corrosion be damned, the scarey part is where does the stress go and how is it dealt with? If you flex a span of aluminum a hundred times it has no visible affect. If you grab it close and flex one spot a few times it breaks off. Putting a rigid piece in a flexible structure concentrates that flex right at the end of the ridgid piece.

I'll ask you this. We have seen several professional engineers state extreme concern over this mod for several reasons. How many have endorsed it? Alan is a great guy, truly and I have purchased more than one of his products....but this one scares me to death.
 
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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.

I'll fourth this, or whatever we're up to now, then add....

We're working on a repair/modification design for a C-130 door at work right now and are having a hard time getting the part stresses and fastener loads down because of these very issues. This stuff can be VERY non-intuitive when working with complex structures, especially where bending and shear is involved (i.e. beams...aka spars).

Alan's mod might be perfectly good, or the inboard-most of the holes might crack in a few hundred hours. The truth is that his mod certainly increases the static strength of the assembly, but unless there's been a fastener-load analysis that includes the relative stiffness's of the layers, there's no way to know if it will help or hurt fatigue life.

From my brief look at the vans mod, you'll see tapering widths and a stiffness compatible with the existing structure (an .032 piece of stainless is ~3X as stiff as an .032 piece of aluminum, no one would suggest repairing an .032 piece of aluminum with .090 aluminum).

USAF uses this stainless in .032" on C-130 wing repairs, but those wing skins are >.125" thick and are attached to the substructure with 3/16 or 1/4 steel taper-lok pins, to give you an idea.
 
I wonder why these cracks started in the first place if the engineering and stress tests where done?

As a general rule of thumb steel and aluminum have different behaviors regarding fatigue. Highly loaded steel structure can be made to last forever if the dynamic stress amplitudes are within certain limits. Many critical parts are in fact designed on purpose to "last forever". Aluminum on the other hand have no such lower limit. Aluminum will sooner or later crack even from the smallest dynamic stress amplitude. It is impossible to design an aluminum part to "last forever" regarding fatigue. Several of the stainless alloys also do not have this limit, and will sooner or later crack.

Carbon fiber structures also shows signs of being able to "last forever" fatigue vise, but no one really knows where the limiting loads are or are able to calculate them in any consistent manner.

If you want something to last forever, steel and carbon fiber is the way to go. All aluminum structures will sooner or later crack apart.

Anyway, "sooner or later" is a key statement here. It's the designers job to assure that cracks develop later rather than sooner. Vans have not told us why these cracks occur. It could be due to dynamic loads in flight, but it could also be due to severe vibrations during start/stop of the engine or something else.
 
Slight drift...

A previous poster said that match drilling a new HS would be difficult.

I thought so, however my local - very experienced Engineer gave me a straightforward method using reference pins installed in the fuselage. Requires basic lathe work.

I would rather spend an hour getting the match drilling correct on a new HS than either rip structure apart or put a non Van's mod on.
 
SB complete

I completed my SB repair and test flew yesterday. The job is not that difficult. but it did take a little longer than "Just a few Hours". It took me an hour and five minutes to disassemble the Doll's empennage. It took most of a day to put it back.

Since you will have to remove the tail anyway, I vote that you go ahead and install Van's SB repair kit. The cost is just $15 dollars plus shipping.
I did all my learning building my HS. I made the mistake of installing the #4 rivets from the front instead of following the rule of manufactured head on the thin material side. "I had a lot to learn then". Fourteen years later I paid the price for that mistake. Having to drill off the rivet heads and punch the shank out in the small space forward of the spar was much more difficult, but I was able to do it without damaging any holes. (If any of you made the same mistake, contact me and I will explain how I did it)

I had two very small cracks in the top side that were less than 1/8 inch in length. I feel confident in the structure now, and doubt there will be any more cracking in that area.
 
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drilling rivets

I did all my learning building my HS. I made the mistake of installing the #4 rivets from the front instead of following the rule of manufactured head on the thin material side. "I had a lot to learn then". Fourteen years later I paid the price for that mistake. Having to drill off the rivet heads and punch the shank out in the small space forward of the spar was much more difficult, but I was able to do it without damaging any holes. (If any of you made the same mistake, contact me and I will explain how I did it)

Danny
i did it too. PM sent
 
Slight drift...

A previous poster said that match drilling a new HS would be difficult.

I thought so, however my local - very experienced Engineer gave me a straightforward method using reference pins installed in the fuselage. Requires basic lathe work.

I would rather spend an hour getting the match drilling correct on a new HS than either rip structure apart or put a non Van's mod on.

If I had to re-drill for a new HS I would take a few bolts - find a machinist who could put a #40 hole .. and the biggest holes possible that he could drill in bolt. Then clamp the new HS in place with the old spacers - Then insert the bolt with the #40 holes and use it has a pilot guide .. drill #40 into the new HS .. then I replace with the other bolt ... drill whatever size hole the machines have put in the bolt .. Then remove the HS and ream the hole .. Just remember to paint the bolts RED ... and put them in your tool box .. Not the strongest bolts to use for anything else but drill guides !!
 
If I had to re-drill for a new HS I would take a few bolts - find a machinist who could put a #40 hole .. and the biggest holes possible that he could drill in bolt. Then clamp the new HS in place with the old spacers - Then insert the bolt with the #40 holes and use it has a pilot guide .. drill #40 into the new HS .. then I replace with the other bolt ... drill whatever size hole the machines have put in the bolt .. Then remove the HS and ream the hole .. Just remember to paint the bolts RED ... and put them in your tool box .. Not the strongest bolts to use for anything else but drill guides !!

Jan I like your idea, brilliant !!
 
If I had to re-drill for a new HS I would take a few bolts - find a machinist who could put a #40 hole .. and the biggest holes possible that he could drill in bolt. Then clamp the new HS in place with the old spacers - Then insert the bolt with the #40 holes and use it has a pilot guide .. drill #40 into the new HS .. then I replace with the other bolt ... drill whatever size hole the machines have put in the bolt .. Then remove the HS and ream the hole .. Just remember to paint the bolts RED ... and put them in your tool box .. Not the strongest bolts to use for anything else but drill guides !!

These are all good ideas being presented on how to match drill a new horizontal stab except they don't account for one critical variable.

They all assume that the holes were drilled perfectly straight and square to the structure in the beginning. It is likely that in many builds they were not. If a match drilling process is used that aids alignment during drilling, and the original holes were slightly miss-aligned, it will result in oversized hole in the fuselage portion. How much, and will it be bad enough to be a problem? It all depends how missaligned the holes were in the first place.
A slight missalignment the first time was not an issue as long as the bit wasn't wobbled... the bolts would still be a tight fit in the holes (just not quite square to the surface). If these holes are now used to match drill, but at a slightly different angle, depending on the variation, it could result in oversized holes.
 
I made the mistake of installing the #4 rivets from the front instead of following the rule of manufactured head on the thin material side. "I had a lot to learn then". Fourteen years later I paid the price for that mistake. Having to drill off the rivet heads and punch the shank out in the small space forward of the spar was much more difficult, but I was able to do it without damaging any holes.

THIS post has instructions for a rivet removal process that doesn't require access with a punch and hammer, and can be used regardless of which way the rivets are oriented.
 
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