Best CPC to use on bolts in wood spars

Discussion in 'Handy Resources' started by Lotahp1, Sep 28, 2018.

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  1. Sep 28, 2018 #1

    Lotahp1

    Lotahp1

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    I’m ready to start bolting back pieces to my new lower right wing and while I’ve used “Clear Coat” (system three penetrating epoxy) to coat inside the holes in the spar (I used a Q-Tip soak in the resin....let dry...reamed hole with correct size reamer for bolt and then re applied a second coat of the Clear Coat penetrating epoxy using a Q-Tip again. I then allowed to dry and reamed the hole a final time and all holes appear well sealed) I’d like to use some sort of Corrosion Preventive Compound (CPC) on the bolt shanks that will live inside the spars. I assume this is overboard and not everyone does this? When I disassembled wing I did have a few bolts with corrosion (rust) on the shanks that were inside the spar. I’d like to avoid that and “do it right”.

    What’s the best product for this? I’ve heard some just use a tiny bit of grease on the shanks and I’ve heard some use something made for this but don’t know the name.

    Recommendations welcome!
     
  2. Sep 29, 2018 #2

    IanJ

    IanJ

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    The canonical Good Stuff seems to be Mastinox, which is about $150 for the smallest tube (5 oz?). A much cheaper alternative is Lanocote, which is based on lanolin and is about $15 for a small tub that would last a lifetime. I'm planning on getting some Lanocote for my wing compression tubes, when I get to the point of assembling things. I imagine it would work just as well for bolts through a spar.
     
  3. Sep 29, 2018 #3

    TFF1

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    My father in law uses something like the lanokote in a spray for rusty bolts. It works really well. Smells like hand lotion.
     
  4. Sep 29, 2018 #4

    Lotahp1

    Lotahp1

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    Thanks for the reply’s. It seams like there’s nothing specific for metal in wood so any of the good CPC products would be ok. I read on another forum of lightly coating the hole/bolt shank with the same epoxy/varnish you used to seal the hole and installing the bolt wet. That also sounds like a good idea and it wouldn’t make for any issues when you go back and re varnish the completed wing after it’s all together. I guess if you are clean with the CPC/grease it wouldn’t be an issue but I could see an issue of the CPC/grease not allowing the final seal coat to stick wherever you get the CPC/grease.

    I dunno...I’m leaning towards just using the same System Three Clear Coat applied to the shank of the bolts lightly as I install. That would seal the moisture out and wouldn’t create another problem with adhesion of the seal coat down the road.

    I’m sure 99% of these planes flying are lucky to have the holes sealed much less worry about the bolts?
     
  5. Sep 29, 2018 #5

    wzm

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    I have a set of the Pitts assembly instructions for a S-1E kit, and I have not seen any mention of coating bolts prior to installing hardware on the wings. Lubrication instructions are called out for other fasteners and cables. I don't imagine it would hurt, but isn't that the point of the cad plating on AN hardware? Have people noticed a tendency for AN hardware to corrode in wood over the years?
     
  6. Sep 29, 2018 #6

    cwilliamrose

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    Yes, the bolts going through wood often corrode in service. I don't think I'd use epoxy on the bolt, wax or some sort of lube would be better IMHO.
     
  7. Oct 3, 2018 #7

    Larry Lyons

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    I would hesitate to use epoxy on the bolts to. I know thing aren't supposed to move once assembled but I like the idea of a preventative better. Something that allows everything to breath/settle in, etc.

    PS: Another option is go to a phenolic bushing like they use with the STC to increase the gross weight of Taylorcrafts. The purests even debate about epoxing the bushing in there too! If you don't epoxy the bushing in it will slide out and can be replaced at a later date.
     
  8. Oct 4, 2018 #8

    taff

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    I used bees wax (at times I remembered!)
     
  9. Oct 4, 2018 #9

    Kiwi

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    If you're over 40 I wouldn't bother. I pulled bolts out of a 60 year old Tiger Moth and put them straight back in they were so clean. The worst ones had just lost the WW2 cad plating. Too much stuffing around and you'll never get it flying. Gotta leave something to deteriorate so your boy has something to rebuild when he's your age.....
     
  10. Oct 4, 2018 #10

    planebuilder

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    We always used wet epoxy on bolts and fittings as a bedding when installing. It eliminates the chance of movement and wear, especially on highly loaded fittings with reversing loads. It also prevents the moisture in wood from corroding the bolt, although in my opinion that's a minor concern. The argument that you can't get it apart later for repairs is not true. A shield can be placed around a bolt head and a small heat source applied to heat it up, it only needs to be too hot to touch comfortably to soften the epoxy/bolt interface to allow the bolt to turn and be removed.
     
  11. Oct 4, 2018 #11

    taff

    taff

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    There is a boat loads of CPC's on line, throw a dart to find one.
     
  12. Oct 6, 2018 #12

    Lotahp1

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    Thanks for all the responses. I ended up kinda doing a combination on the spar to wing attach plates. I lightly sanded the plywood doublers on the spars where I had previously applied System three clear coat as a sealer under the fittings. I then squeegeed on a very thin coat of System Three Clear coat and sat the flat plates on the wet clear coat...this coat was VERY thin. As thin as a squeegee/bondo spreader would allow. I then lightly coated bolt shanks in some CPC and installed and tightened everything up. There was so little epoxy present there wasn’t even any squeeze from around the flat metal plates but my thought is the plates will now be better water proof between. Probably a lot of wasted time and effort vs slapping the plates on with dry bolts. I dunno. But really didn’t take much more effort.
     

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