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Thread: Metal bonding?

  1. #1
    Farmboy's Avatar
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    Metal bonding?

    Quick question for you A&P and Repairmen types - I use a few different expoxies on fiberglass and metal, but I've not really tested much on thin aluminum, vibration and longevity.

    I just pulled off my nose cowl to double up a couple of runaway cracks, and as I was looking it stuck me that maybe I should bond a doubler on it instead of riveting them on.

    Anyone do this, did this, or have good/bad results?

    Thanks,
    Peter
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  2. #2
    behindpropellers's Avatar
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    Sikaflex makes excellent polyurethane bonding solutions. I think it would work well, you probably need to etch and alodine the area first, though.

    Tim
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  3. #3
    cubdriver2's Avatar
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    This is all I will use for auto windshields. Bonds anything that is clean and dry. Even bonded the tires to the wheels on Miss Budweiser's 6500HP pulling tractor

    https://www.amazon.com/Dow-U-418-Sea...keywords=u-418

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  4. #4
    RaisedByWolves's Avatar
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    Metal bonding?

    Go to the auto body store, they bond truck beds and panels together now a Days


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  5. #5
    Farmboy's Avatar
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    I've used beta seal before and that required the primer -- I see you use the primerless.
    I've also used a couple of the products from Loctite and plexus that seem to bond metal very well. Often considered glass bonders due to the hardness factor.


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  6. #6
    Dave Calkins's Avatar
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    3M brand 5200 marine sealant is somewhat of a standard for aluminum aircraft float building and repairs.

    West System brand epoxy has tech data on bonding many different substrates.

    I am with you on bonding rather than just rivets Farmboy.
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  7. #7
    Farmboy's Avatar
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    While I would find 5200 to be a great adhesive/sealant in the Marine world, I would not use it on an aircraft. It's properties are just not what I would want for true "bonding". Besides that it's a pain in the ass to use without covering yourself in it. Nearly impossible to lay a thin coat.

    So far doesn't sound as though anybody has a negative experience though, which makes me lean towards bonding in this application.

    Pb


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  8. #8

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    3M5200 is pretty amazing stuff, as is readily available.
    Remember, These are the Good old Days!

  9. #9
    Farmboy's Avatar
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    My supplier has it in bulk, and trust me when I say I'm pretty familiar with 5200.
    It may be a good option for float application but it's still not going on my cowling.



    On the other hand, I use this product to bond an aluminum sleeve to stainless with no failures.





    Transmitted from my FlightPhone

  10. #10

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    Pete,
    Auto body repair supply or a NAPA will have the auto panel adhesives. I believe that is what they used to put my truck bed side together when they replaced it.
    Chip

  11. #11

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    My experience with 2 part Epoxy is it can get brittle (especially if not used sparingly) and fail in a connection that wants/needs to move a little, gets twisted with use (remember nothing is rigid), or is subject to vibration hence the reason I like 5200. Yes it's NASTY to work with but there is a reason many boat manufacturers switched to it for the deck in the hull joint vs. epoxy.

    You have a shop full of nice rigs and I respect your experience but I learned this the hard way... I sunk one with an epoxy joint that failed!

    OC

    ps. if you want to have some (permanent) fun, stick a couple of coins to the floor of your shop with a dot of it and watch the show, its good for years of entertainment as people come and go.
    Remember, These are the Good old Days!

  12. #12
    cubdriver2's Avatar
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    Quote Originally Posted by OLDCROWE View Post


    ps. if you want to have some (permanent) fun, stick a couple of coins to the floor of your shop with a dot of it and watch the show, its good for years of entertainment as people come and go.
    Poor Eaton, how many times have you gotten him?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  13. #13
    Dave Calkins's Avatar
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    I learned to appy sticky stuff with a notched trowel a few years ago. Is easy to get a uniform film thickness. I buy varied notch sizes in cheapo plastic spatula/putty-knife looking tools for a couple bucks each. have been able to reuse them sometimes.

    The Plexus (not plexiglas cleaner) that I use for secondary bonding of composite structures is very neat stuff, but rigid, maybe even "brittle".

    As I said before, 5200 is used aLOT for bonding aluminum doublers, etc. You dont have to use it. I do alot.

    Maybe "Hysol" (not sure about the spelling or which product) epoxy would make you happy. Its that pink stuff you see on Cessna Caravan cowlings for sheetmetal bonds. Very good product.

    Let us know how it goes. any bonder will perform better than "just" rivets.
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  14. #14
    Bearhawk Builder's Avatar
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    3m 8115 Automix Panel Bonding Adhesive. Don't get it on yourself
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  15. #15
    aktango58's Avatar
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    Quote Originally Posted by Farmboy View Post
    My supplier has it in bulk, and trust me when I say I'm pretty familiar with 5200.
    It may be a good option for float application but it's still not going on my cowling.



    On the other hand, I use this product to bond an aluminum sleeve to stainless with no failures.





    Transmitted from my FlightPhone
    See if I offer you to ride in a float plane now! Insults abound. At least now I know what to bring you next trip!

    I always masked off areas prior to using 5200. Cut it with alcohol and apply with a solvent brush. Messy, but things do not leak after
    I don't know where you've been me lad, but I see you won first Prize!
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  16. #16
    Farmboy's Avatar
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    Metal bonding?

    Ha! George, I already know you better than that.

    And don't take it the wrong way guys, if I was fixing a pair of floats I'd be all over the 5200. It's an excellent sealant and adhesive combination. Lifeseal is very similar without the adhesive.

    Like somebody mention, the plexus we use when bonding fiberglass is a structural bond and it can break free if the surface isn't prepped. Depending on the number, it can have brittle results.
    But a good sealant is on the other end of the bonding scale, retaining flexibility to ensure the seal. Since I am not sealing out water, I just don't see the need for the bonding agent to be flexible when the patched cowl will have 3 layers of aluminum sandwiched on. Flexible agent or not, it's going to end up pretty rigid.

    Pb


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  17. #17
    Gordon Misch's Avatar
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    I think a flexible bonding agent might help damp out vibrations. It's the vibrations that aggravate cracking. Therefore, the flexible stuff might be advantageous?
    Gordon

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  18. #18
    aktango58's Avatar
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    Just a nice even bead about 1/4" thick from the front of the hinge down the front cowl, back along the top of the bottom cowl, then up the boot cowl to the hinge.

    Close and secure cowl, maybe need to use a little more 5200 to fill the gaps.

    Wait 12 hours and your vibration of the cowl will no longer be an issue


    But, on the other hand, consider that vibration is transferred easily through a firm solid surface, but is dampened by a soft surface. By adding some form of flexible sealant, (even cheap silicone), you would create a vibration dampener; by doing the three plates of aluminum you might just be building a thicker pice to amplify the vibrations.

    So run her how you wish, then head to Glenn's and switch cowls when your's is done
    I don't know where you've been me lad, but I see you won first Prize!
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  19. #19
    Farmboy's Avatar
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    Metal bonding?

    I am definitely not a harmonic engineer, nor have I played one or stayed at a holiday inn express.

    My perception of this scenario from a vibration standpoint is that we are not trying to dampen vibration from being transferred. If we were attaching a bracket to the firewall and said bracket has the possibility to vibrate, then a flexible bond would seem like a good idea to separate the vibration from transferring to the firewall.
    In this case the cracks on the nose cowl typically stem from a corner point where the stresses become concentrated or a once hard point that has become loose. Or a third case of an outside influence such as a corner of a side cowl rubbing.
    I could be wrong here, but my perception is that trying to allow the cowl to vibrate between the doubler layers isn't the solution, as we aren't trying to isolate the vibration. We can't, it's all one piece.
    I have a nice patch already that has not caused any stress cracks or fatigue in any nearby region. At the moment I like a stiffer cowl over a less stiff one.

    And if that doesn't work, I know where Glenn's is. You guys just need to invite him back to Alaska for a bit.

    Pb



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  20. #20
    Gordon Misch's Avatar
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    All good points, I think. But also, you're trying to reduce amplitude of vibration. Changing the stiffness will change that - maybe more, maybe less depending on harmonics - but dampening will only reduce amplitude. I don't see it as an isolation issue. But of course, I've been wrong before - - -

    Furthermore, a brittle substance (epoxy?) might fail, whereas when subjected to the same circumstances, a visco-elastic substance (5200?) might absorb more strain energy and therefore be more effective?
    Last edited by Gordon Misch; 10-23-2017 at 11:19 PM.
    Gordon

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  21. #21
    skywagon8a's Avatar
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    When you change the amplitude of the vibration as Gordon suggests, consider that you will be changing the characteristics of the entire part. It is possible that you will solve the original cracking issue only to find that due to your altering of the natural amplitude of the vibration of the part that it could crack elsewhere. Adhesive would be better than rivets in this case since it helps by absorbing and changing the vibrations.
    N1PA

  22. #22
    nanook's Avatar
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    https://www.westmarine.com/buy/west-...dener--9223132

    A more flexible epoxy and very tough.
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  23. #23

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    A few suggestions, 1.) I'm sure you've already done this; review manufacturers data for your choices. Consider factors of elevated temperature, solvents, etc. 2.) Try some rudimentary testing by bonding some test samples for a peel type test to see how well they perform. Bend one piece into an L (1/2" to an 1" wide should work) then bond to a plate. A crude test would be hit them with a hammer in a vise. Adhesives are weakest in shear, generally. Not real scientific, but this could provide some idea on how each type performs. 3.) Call or email the manufacturers and explain your application. They may have some ideas.

  24. #24
    www.SkupTech.com mike mcs repair's Avatar
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    we used to glue the Gar-Aro wheel adaptors on with scotchweld... worked good, but that had a minimum thickness required to cure right... I forget the scothweld number... only failures were the people who didn't follow the directions and remove the paint from the 6" wheel & such, then it was only as strong as the paints adhesion to the wheel

    https://www.3m.com/3M/en_US/company-...94857497&rt=r3

    anyone remember the number???

    we would bake wheel to 400 degrees if we needed to disassemble the assembly and have tho use a sledge hammer & wood blocks to separate them still..

  25. #25
    behindpropellers's Avatar
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    Quote Originally Posted by RaisedByWolves View Post
    Go to the auto body store, they bond truck beds and panels together now a Days


    Sent from my iPhone using Tapatalk
    This is one of the products they use: https://www.amazon.com/Sikaflex-252-...flex-252&psc=1

    I used to use it to bond lead shielding to plastic, fiberglass, and aluminum on cardiac imaging machines. It stays flexible. You won't remove your doubler!

    Tim
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  26. #26

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    New product bonds metal, rubber, and most plastics. Commercial shows a locomotive pulling a train with a drawbar bonded by this adhesive.

    http://na.henkel-adhesives.com/produ...=8841907863553

  27. #27
    Farmboy's Avatar
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    As a member sent me a note asking what I ended up using for this, I thought I'd share my results since repairing the nose back to a serviceable standard.
    I did not take the time to sand, fill, paint match and shoot it, as I expect to be modifying more cowl parts for heat issues and so I can paint all items at once at a later date.

    As I had experience with the Loctite E-30CL, and as a "glass bonder" it's approved/recommended by the mfg for bonding metal, aluminum and other "hard" materials, I used it in this application.
    The use here was to bond doublers on the inside of the nose, to stop the wild cracking that had happened from various fastener locations or corner stress points. I did not use any mechanical fasteners, and relied only on the adhesive to bond the doubler to the nose. Prep is often everything, so I ensured that the area was prepped and the doubler fitted the contours as was possible prior to clamping. Most adhesives have some requirement of pressure to provide the best bond, and while I don't clamp my tubes when using E-30, I did clamp all of the areas for this repair.

    To date I've flown the aircraft 35 hours since re-installing it with no change in the cracks, nose, or any part of the repair or surrounding area.

    I'll add some photos which will be self-explanatory. When we get to paint it a little filler to smooth out the cracked areas on the front side will make it beautiful again.

    pb

    Nose - 1.jpg

    Nose - 2.jpg

    Nose - 3.jpg

    Nose - 4.jpg

    Nose - 5.jpg

    Nose - 6.jpg

    Nose - 7.jpg

    Nose - 8.jpg

    Nose - 1 (1).jpg
    Last edited by Farmboy; 01-12-2018 at 07:34 PM.
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