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Thread: Jury strut AN bolts, nuts and washers

  1. #1

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    Jury strut AN bolts, nuts and washers

    The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

    Firstly, do I order Cadmium or stainless replacements?

    Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

    Can anyone help? Steve Pierce?

    Thanks in advance,

    David
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    Steve Pierce's Avatar
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    I don't know how strong the stainless is. I would coat with something. Here is my hardware call-out.
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    Last edited by Steve Pierce; 11-23-2018 at 03:56 PM.
    Steve Pierce

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    Grant's Avatar
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    We use this on all exposed hardware on float planes.

    ARDROX
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    Stainless.

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    Steve Pierce's Avatar
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    Quote Originally Posted by stewartb View Post
    Stainless.
    I haven't looked but I guess they are equal in strength?
    Steve Pierce

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    In shear they're stronger than what they're connecting.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by BritishCubBloke View Post
    The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

    Firstly, do I order Cadmium or stainless replacements?

    Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

    Can anyone help? Steve Pierce?

    Thanks in advance,

    David
    Use stainless

    And you need my app I wrote to help you find correct bolt lengths. Very simple to use. http://www.skuptech.com/page4/page4.html


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    You guys are all superb. Thank you!!

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    skywagon8a's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Use stainless
    Mike what does your FAA guy say about the substitution of stainless hardware for the approved AN hardware? I can see it with screws holding fairings but this is a semi structural use.
    N1PA

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    Jury Strut Hardware

    I have cleaned up a relevant drawing (13405) with photoshop and enlarged the labels with the hardware listings, that probably has all the information you need. The system only uploaded a low resolution jpeg/pdf file but I will try and send you high resulotion copies.

    A2/A4 stainless would certainly be more resilient but in the UK we would certainly need specific approval so not really an option.

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    Quote Originally Posted by skywagon8a View Post
    Mike what does your FAA guy say about the substitution of stainless hardware for the approved AN hardware? I can see it with screws holding fairings but this is a semi structural use.
    Corrosion resistant (stainless) hardware is FAA approved. The nomenclature just adds a "C" after the size. So your AN3-5A (undrilled cad plated approved bolt) becomes a AN3C-5A ( undrilled stainless steel approved bolt) They do cost a bit more, and I don't know about weight. I use them on exhaust and floats. Also, nuts are available in corrosion resistant steel, and are also standard, legal approved AN hardware.
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    Quote Originally Posted by Grant View Post
    We use this on all exposed hardware on float planes.

    ARDROX
    This is interesting. I've always used a mix of Paralketone and solvent thinned for spraying inside airframes, and brushed it on exposed fittings and bolts.. but this sounds like it might be better. Is it a form of the same thing? Which I guess is basically a paraffin based coating? I've always figured Paralketone was like Cosmoline, but never sure. I read the website and would like to learn more from real experience. Is this product similar to something like Paralketone but available in different consistencies etc.? Always looking for something better when it comes to salt and airplanes..

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    Quote Originally Posted by 46 Cub View Post
    Corrosion resistant (stainless) hardware is FAA approved. The nomenclature just adds a "C" after the size. So your AN3-5A (undrilled cad plated approved bolt) becomes a AN3C-5A ( undrilled stainless steel approved bolt) They do cost a bit more, and I don't know about weight. I use them on exhaust and floats. Also, nuts are available in corrosion resistant steel, and are also standard, legal approved AN hardware.
    Yes BUT, is the AN3C-5A approved as a substitute for the AN3-5A? The original poster BritishCubBloke is in the UK where the regulations are different than here in the States. Has the FAA approved this substitution? The C hardware is not called out in the Piper parts list to my knowledge.
    N1PA
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    Quote Originally Posted by skywagon8a View Post
    Yes BUT, is the AN3C-5A approved as a substitute for the AN3-5A? The original poster BritishCubBloke is in the UK where the regulations are different than here in the States. Has the FAA approved this substitution? The C hardware is not called out in the Piper parts list to my knowledge.
    Well, yeah.. I suppose you are right about that. I don't know... for that matter I've never looked them up to see if they have equivalent properties.. shouldn't have suggested them.

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    Quote Originally Posted by 46 Cub View Post
    The nomenclature just adds a "C" after the size. So your AN3-5A becomes a AN3C-5A
    I've been looking for some numbers for this hardware and have only found the shear strength of the AN-3 bolts as being 75,000 psi.
    Does anyone know what the shear strength of the AN-3C is?

    I suspect that it is less.
    N1PA

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    Quote Originally Posted by skywagon8a View Post
    I've been looking for some numbers for this hardware and have only found the shear strength of the AN-3 bolts as being 75,000 psi.
    Does anyone know what the shear strength of the AN-3C is?

    I suspect that it is less.
    Curious now, I typed it into Google "AN3C shear strength". I don't know how to share links, but the first page was from Coast Fabricators. By their specs they list the AN3 and AN3C as 125,000 tensile, and 75,000 shear, with a 450 degree temp rating. At least on that page, there did not seem to be a distinction between the two in their properties.
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    www.SkupTech.com mike mcs repair's Avatar
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    Are the stainless bolts (AN3C) the same tensile strength as the cad plated ones?
    The tech data sheet does not list a separate tensile strength for corrosion-resistant steel bolts. That would indicate they would be rated the same per the TDS.

    Hex head aircraft bolts are made of high-strength type 4037 or 8740 alloy steel (type 8740 is most commonly used). The bolts are centerless ground and threaded after heat treatment. Minimum tensile strength 125,000 PSI. Cadmium plated per specification QQ-P-416A, Type II, Class 3. Available with shank drilled for cotter pin or undrilled for stop nut application, and with or without drilled head for safety wire. Specify bolts to have undrilled shank by adding letter "A" after the dash number. For bolts with drilled head add letter "H" after the AN number. (AN3H-15) See illustrated examples. "C" represents Type 431 Stainless Steel (contains iron which is magnetic). The length of AN aircraft bolts is measured from under the head to the end of the shank. The "grip" is the unthreaded portion of the shank. See table for conversion of length and/or grip to proper AN callout. "C" stands for stainless. Others are cadmium plated.



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    Jury strut tubing is what.... 20 ga? Maybe thinner? You flatten the tube ends and drill a hole to pin with a bolt in shear. What's the tear strength of the flattened tube ends? Common sense favors the bolts being stronger than the tube ends. Especially 50 year old tubes with internal corrosion. Arguing structural properties of the bolts seems silly.
    Last edited by stewartb; 11-24-2018 at 12:24 PM.
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    Quote Originally Posted by stewartb View Post
    Jury strut tubing is what.... 20 ga? Maybe thinner? You flatten the tube ends and drill a hole to pin with a bolt in shear. What's the tear strength of the flattened tube ends? Common sense favors the bolts being stronger than the tube ends. Especially 50 year old tubes with internal corrosion. Arguing structural properties of the bolts seems silly.
    Well, it was about whether it is the same part to satisfy the controlling authority. Here, under the jurisdiction of my own PMI, I know I can use my own judgement where to use them. I would use them in jury struts, but would want to have paperwork by the manufacturer stating identical properties before using them in, say, a gear bolt. And, of course everyone recognizes there are qualities such as ductility, hardness, toughness.. beyond simple strength. I agree it won't make a difference in a jury strut but the point made by skywagon8A is a good one.. In England he may be stuck with the precise part number. He could just buy 10 of them and change them out when not pretty..if he doesn't want to paint them or goo them up with wax. I like to use wet paint for assembly on the parts that are going to stay together for a long time.
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    It's actually just cheap entertainment for me. I've never bothered to look up the difference, and I find it interesting to learn more.. so reading the input here is the sort of thing I like about this site... It is likely esoteric knowledge for many, but I enjoy learning a little here and there..

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    Quote Originally Posted by 46 Cub View Post
    Curious now, I typed it into Google "AN3C shear strength". I don't know how to share links, but the first page was from Coast Fabricators. By their specs they list the AN3 and AN3C as 125,000 tensile, and 75,000 shear, with a 450 degree temp rating. At least on that page, there did not seem to be a distinction between the two in their properties.
    I found that and it does indicate the same. Yet there are two separate alloys involved which would imply that there ought to be different numbers however slight. Yet this document is only a parts catalog.
    Quote Originally Posted by mike mcs repair View Post
    Are the stainless bolts (AN3C) the same tensile strength as the cad plated ones?
    The tech data sheet does not list a separate tensile strength for corrosion-resistant steel bolts. That would indicate they would be rated the same per the TDS.
    mike do you have a link to the tech data sheet?
    If in fact they are the same, then the bolts would be interchangeable. Yet we as aircraft mechanics would need this proof in order to back up our use of a substitution.
    N1PA

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    www.SkupTech.com mike mcs repair's Avatar
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    this is the weakest link in jury strut system

    http://supercubproject.com/drawings/pdfs/A3290163.pdf

    and the other components below
    http://supercubproject.com/drawings/pdfs/A3290162.pdf

    this actually older welded, not rolled from round
    http://supercubproject.com/drawings/pdfs/A3290425.pdf

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    musket's Avatar
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    This website http://everyspec.com/ contains specifications on just about any piece of hardware made in the U.S. (I think).

    If one searches for AN3 a four page PDF file is available giving a tremendous amount of info on that bolt.
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    Quote Originally Posted by BritishCubBloke View Post
    The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

    Firstly, do I order Cadmium or stainless replacements?

    Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

    Can anyone help? Steve Pierce?

    Thanks in advance,

    David
    David,

    I worked on a supercub that lived in the Bahamas 3 months out of the year. A few points:

    1. Hot salt water environments seem to increase corrosion.

    2. We changed all external hardware to stainless.

    3. The wings and aft fuselage received a boeshield fog every year.

    4. Every year we removed all of the float parts (brakes & actuators)- (amphibs) and cleaned the salt off. If you did not do this the salt water would get in between all of the surfaces and corrode over time. Imagine running a slat water power washer over all of the amphib cub parts.

    Tim
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    Quote Originally Posted by behindpropellers View Post
    David,

    I worked on a supercub that lived in the Bahamas 3 months out of the year. A few points:

    1. Hot salt water environments seem to increase corrosion.

    2. We changed all external hardware to stainless.

    3. The wings and aft fuselage received a boeshield fog every year.

    4. Every year we removed all of the float parts (brakes & actuators)- (amphibs) and cleaned the salt off. If you did not do this the salt water would get in between all of the surfaces and corrode over time. Imagine running a slat water power washer over all of the amphib cub parts.

    Tim
    Kinda like this?
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    Steve Pierce

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    skywagon8a's Avatar
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    Quote Originally Posted by musket View Post
    This website http://everyspec.com/ contains specifications on just about any piece of hardware made in the U.S. (I think).

    If one searches for AN3 a four page PDF file is available giving a tremendous amount of info on that bolt.
    Thanks, I looked at this. It gives the shear strength for AN-3 steel at 2,125 pounds and aluminum AN-3DD at 990 pounds. It does not address the corrosion resistant steel. Without knowing the specific alloy of these bolts it is not possible to determine the actual shear strength. In my experience the stainless hardware has a lower shear strength. As a result I would have no ammunition to justify using the AN-3C as a substitute for an AN-3. If someone can document the -3C number which will prove that it is at least as strong as the -3, then I would without reservation recommend using the AN-3C as a substitute for the AN-3.

    It is likely that using the AN-3C bolts as a substitute for the AN-3 for attaching the jury struts on a Cub will be satisfactory. I just can not prove that it is.
    N1PA
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    The jury struts only stabilize the lift struts. They aren't really directly subject to flight loads. So in my opinion that AN3 bolt is simply the smallest readily available "bolt", and its stress capability really isn't important. It would be interesting to compute for comparison the edge pullout strength of the thin jury strut material. I'd be surprised if it's even close the bolt strength. But I've been wrong before - - -
    Gordon

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    The jury struts only stabilize the lift struts. They aren't really directly subject to flight loads. So in my opinion that AN3 bolt is simply the smallest readily available "bolt", and its stress capability really isn't important. It would be interesting to compute for comparison the edge pullout strength of the thin jury strut material. I'd be surprised if it's even close the bolt strength. But I've been wrong before - - -
    I agree on the part that the bolt is too big for its use...

    BUT, take a rear jury strut out and lift or push on a wing tip and watch the rear spar flex!! amazing amount... best illustrated before you put the leading edge on....

    when we patch up a plane to ferry back, jury struts MUST be there... even if wing is all bent up...

  30. #30
    Gordon Misch's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    I agree on the part that the bolt is too big for its use...

    BUT, take a rear jury strut out and lift or push on a wing tip and watch the rear spar flex!! amazing amount... best illustrated before you put the leading edge on....

    when we patch up a plane to ferry back, jury struts MUST be there... even if wing is all bent up...
    Agree completely.
    Gordon

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  31. #31
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    Quote Originally Posted by Gordon Misch View Post
    The jury struts only stabilize the lift struts. They aren't really directly subject to flight loads. So in my opinion that AN3 bolt is simply the smallest readily available "bolt", and its stress capability really isn't important. It would be interesting to compute for comparison the edge pullout strength of the thin jury strut material. I'd be surprised if it's even close the bolt strength. But I've been wrong before - - -
    I agree Gordon, but when you have an A&P license and you have to place your name and number in a log book you have to be able to back up doing such.

    IF an A&P gets in the habit of making minor substitutions such as this, what else does he do without justification? What happens when Mr. FAA happens to notice the substitution while he is wondering about the airport and decides to look into who did it? What if that Mr.FAA is an a$$ h--- (There are some you know) and decides to put you, the A&P on his s--- list? You are using your A&P license to earn a living. Do you really need this hassle just because you used an AN-3C bolt on a jury strut in plain sight?

    In this example it would be relatively easy to set up a test rig to find out which would fail first, the jury strut, the attachment to the lift strut or the AN-3C.

    I can tell you from personal experience how much pleasure is derived when one of these above mentioned Mr.FAA types is put in his place. In the end Mr.FAA will come to you asking for your assistance, never harassing you again.
    N1PA
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    Quote Originally Posted by skywagon8a View Post
    I agree Gordon, but when you have an A&P license and you have to place your name and number in a log book you have to be able to back up doing such.

    IF an A&P gets in the habit of making minor substitutions such as this, what else does he do without justification? What happens when Mr. FAA happens to notice the substitution while he is wondering about the airport and decides to look into who did it? What if that Mr.FAA is an a$$ h--- (There are some you know) and decides to put you, the A&P on his s--- list? You are using your A&P license to earn a living. Do you really need this hassle just because you used an AN-3C bolt on a jury strut in plain sight?

    In this example it would be relatively easy to set up a test rig to find out which would fail first, the jury strut, the attachment to the lift strut or the AN-3C.

    I can tell you from personal experience how much pleasure is derived when one of these above mentioned Mr.FAA types is put in his place. In the end Mr.FAA will come to you asking for your assistance, never harassing you again.
    Well said Pete. I read lots of posts from people who have nothing to risk like their A&P license and Inspectors Authorization. It makes you think differently especially when you sit across the table from the FAA and their lawyers because none of it has to do with what really happened and what caused it. It's about hanging out to dry.
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    The AN3 thru AN20 drawing does not differentiate between steel and stainless steel as far as strength. Both the AN3 and AN3C have to meet the same strength requirements. An AN3DD has lower strength requirements, so it would not be acceptable as a replacement part. That’s what you call a Minor Alteration, and is within the preview of an A&P to do using “acceptable” data (the AN drawing). Of course you should also consider the galvanic action between the steel tubing and the stainless bolt, washer, and nut. By changing to a stainless bolt, you are changing from the bolt (cad plating) being the sacrificial material to the jury strut becoming the sacrificial material. The AN3 thru AN20 drawing was canceled in December 1999, and was replaced by NASM3 thru NASM20.


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    Quote Originally Posted by dgapilot View Post
    The AN3 thru AN20 drawing does not differentiate between steel and stainless steel as far as strength. Both the AN3 and AN3C have to meet the same strength requirements. An AN3DD has lower strength requirements, so it would not be acceptable as a replacement part. That’s what you call a Minor Alteration, and is within the preview of an A&P to do using “acceptable” data (the AN drawing). Of course you should also consider the galvanic action between the steel tubing and the stainless bolt, washer, and nut. By changing to a stainless bolt, you are changing from the bolt (cad plating) being the sacrificial material to the jury strut becoming the sacrificial material. The AN3 thru AN20 drawing was canceled in December 1999, and was replaced by NASM3 thru NASM20.


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    Was going to go dig thru all my books and see if I remember or even knew how to find all that stuff. Where do you get all the info like that.
    I may be wrong but that probably won't stop me from arguing about it.

  35. #35

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    DLA quick assist has most of the AN drawings on line, along with the cancelation notices. The new NASM drawings are only available if you pay for them.


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    Thanks. Found my way to the bolts. Not sure I'll ever need it but nice to know where it is.
    I used to have a little black book I got from Spartan with some of that stuff on it.

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    Last edited by S2D; 11-27-2018 at 09:52 PM.
    I may be wrong but that probably won't stop me from arguing about it.
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    This has been interesting to follow and it's made me do some reading. AC43.13 doesn't differentiate between AN bolts in general use. I've read through the bolt section several times and can't find any reason not to use corrosion resistant bolts where they're beneficial.

    From AC43.13-1B-
    7-41. STANDARD AIRCRAFT HEXHEAD BOLTS (AN3 THROUGH AN20).These are all-purpose structural bolts used forgeneral applications that require tension orshear loads. Steel bolts smaller thanNo. 10-32, and aluminum alloy bolts smallerthan 1/4 inch diameter, should not be used inprimary structures. Do not use aluminum boltsor nuts in applications requiring frequent removalfor inspection or maintenance.
    Since corrosion was mentioned, and we're talking about mild steel parts being pinned by stainless steel bolts, is galvanic corrosion a threat? We're bolting painted parts together so the corrosion cell potential would be unimportant, wouldn't it? At least in this application?

    How are you guys seeing the ASSIST bolt specifications? I can't get into that site using search criteria that I've tried.
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    When looking at the galvanic chart, cadmium is more anodic compared to steel, so the cad plating on normal AN bots becomes the sacrificial material. When comparing steel with all the nickel alloys, steel is anodic as compared to stainless, and is farther apart than cad/steel, so the corrosion the steel becomes the sacrificial material, and it corrodes faster than the cadmium would. I hope that makes sense.

    Best option would be not to scratch the cad plate on regular AN bolts, and coat with a protective coating to keep moisture out. If you use stainless hardware, without adequate protective coating, you will likely be replacing your jury struts and clamps before the bolts and nuts.


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  39. #39

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    When you get to quick assist site, in the document ID field put AN3, first item in the list is AN3thruAN20, click that, then on the next page click revision 12 to get the drawing.


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  40. #40
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    I'd stay away from stainless hardware in that application. When you put two dissimilar metals in contact, the "lesser" metal is going to corrode. In the case of stainless hardware attaching a jury strut, the jury strut becomes the "sacrificial" part..... I'd rather have the bolts corrode, because a) they're cheaper than jury struts and b) with the specified steel bolts, there's no question about legalities.

    I ran a Beaver and a Super Cub, and owned a J-3, all on floats, and operated regularly in salt water in Kodiak. All external hardware was coated with Paralketone and/or the heavy LPS. These airplanes (except the J-3) were subject to 100 hour inspections, and the mechanics hated cleaning them up at each inspection, but our Chief of Maintenance told me to keep gooping them up....no corrosion.

    When that Super Cub went in for recover, I fully expected it to require major repairs. It was a 1969 model, and was recovered in 1984 (original factory cotton). When the fabric came off, everything looked new under.

    I'd stick with steel hardware, and apply some sort of anti corrosion coating, like paralketone.

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