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gareywittich
08-25-2011, 09:09 PM
Any recommendations for a sealant / caulking material that is paintable, non-acidic (so no corrosion properties) to be used on aluminum skins (not in engine compartment) - ie. butt joints or overlapping skins. I know ProSeal has been used - is there another product similiar to bathtub caulking that comes in tubes ?? Many thanks !!! Garey Wittich Santa Monica, CA

Mike Switzer
08-25-2011, 09:29 PM
Check out DOW 732 silicone, we used it for everything in food processing, i know it can be painted, pretty sure it is non acidic, it is almost as strong as construction adhesive. We used to put safety signs on the walls with it at Kraft in champaign, if you wanted to move the sign half the time the food grade ceramic tile would come off with the sign

I caulked all my windows in my shop with it

if you cant get it local check out mcmaster.com - just dont buy a whole case if you wont use it it will harden in the tube over time

Eric Witherspoon
08-25-2011, 09:41 PM
What are you sealing the joints for? Water? Fuel? Proseal (polysulfide) is a fuel tank sealant.

Mike Switzer
08-26-2011, 06:39 AM
What are you sealing the joints for? Water? Fuel? Proseal (polysulfide) is a fuel tank sealant.

Good question - if he is sealing from fuel the DOW 732 won't work so good, they have another one for that

gareywittich
08-29-2011, 04:18 PM
My QUESTION is for recommendation of a Caulking / Sealing Material that is "paintable', "non-corrosive" (non-acidic) to seal against water and avgas from penetrating aluminum "butt joints" and "overlapping" skins - ie. exterior fuselage and wing skins (NOT for fuel tank sealing). Many thanks, Garey Wittich Santa Monica, CA

Bob H
09-01-2011, 07:40 PM
Try Dow Alex. It's a silicone/latex blend which can be painted.
http://www.dap.com/product_details.aspx?product_id=1
Bob H

Rick Galati
09-03-2011, 05:11 AM
Why try to reinvent the wheel? Proseal is a widely accepted material that has long been used in far more applications than just fuel tank assembly. Proseal, applied under tens of thousands of airframe rivets and exterior mating parts on high dollar military and commercial aircraft is a key component that makes pressurization possible. Readily paintable, proseal is the long accepted industry standard for enhancing corrosion control, butt sealing, filet sealing, fay sealing, and oh yeah, fuel tank sealing. It sounds to me like you are looking for some cheap and easy material you can buy at the local big box store and simply squirt through a caulking gun. If that is so, perhaps you are unaware that some proseal products are indeed packaged for use in a caulking gun. Why experiment with some non-conventional material that in practice may or may not be up to aerospace standards? I'd take the uncertainty out of it and go with accepted practice. Stick with proseal.

David Darnell
09-03-2011, 10:39 AM
Yes, Pro Seal is "proven" and there are multiple places where I would consider nothing else. However, it has a couple of drawbacks IMO. First off- $$$ Second, It's not as readily available as some possible alternatives. Which would you rather use in some not critical areas- Pro seal @ 150$ a pint that you have to order and wait a week (or two), or a $5 tube of caulking that you can get at Home Depot

Rick Galati
09-03-2011, 01:34 PM
......Pro seal @ 150$ a pint that you have to order and wait a week (or two), or a $5 tube of caulking that you can get at Home DepotI would be surprised if that $5 tube of paintable, non-corrosive, non-acidic caulking formulated to endure the rigors of exterior aircraft use even exists. Still, I am curious about your assertion that proseal costs $150 per pint. How did you arrive at that price? For instance, Wicks retail cost for a pint of proseal is nowhere near the price you cite:

http://www.wicksaircraft.com/catalog/product_detail.php/pid=6801~subid=11807/index.html

Proseal can also be purchased in a conveniently packaged tube form:

http://www.aircraftspruce.com/catalog/appages/prosealant.php

Certainly, proseal is a relatively expensive product designed for aircraft use but like everything else in or out of aviation, you get what you pay for.

Eric Witherspoon
09-03-2011, 02:05 PM
Taking Garey's question to the limit, is it even necessary to "seal" skins that are being painted over at all? Perhaps I've spent too much time in the lighter/cheaper side of homebuilding, as I haven't seen any project or build log even talking to this point at all. If they want paint, they just paint the outside. Can anyone else comment w/r/t what lighter certified aircraft do? Anyone ever drill the rivets out of a Cessna, Beechcraft, Piper, or Mooney? What's in there?

What type of storage situation or operating conditions drive the question? Outside, near the ocean? Seaplane?

David Darnell
09-04-2011, 08:51 AM
I was pricing the Pro-Seal 870 series sealant in the cartridges- typically 30-35$ for 2.5 oz, 45-50$ for 6 oz. Canned pints are comparatively cheaper, typically $100 or so (all prices not including S&H) FYI, the 870 series is considered better for use where corrosion resistance and weathering is a factor. Also recommended for anyplace where dissimilar metals are riveted together.

As far as what the manufacturers do, I really can't say for sure. Do know that several of the skins on a UH-60 are riveted and bonded with PS-870. Makes for a very strong joint- I wouldn't recommend doing it on something you may have to go back into