xcrmckenna Posted August 3, 2020 Report Share Posted August 3, 2020 I’m replacing my wing walk. I stripped it to bare aluminum to help reseal a few fuel leaking screws. Wondering what good mixing techniques or tips on application so I don’t have to do it again anytime soon. The ratio on the cans say 100:10, the smallest order I could make was 15oz’s but that seems like overkill for a few screws so I was only going to mix half at a simpler 10:1. Always appreciate any help I can get for the first time I do something with the plane. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 3, 2020 Report Share Posted August 3, 2020 There is a specific method of mixing this kind of stuff... The kind of stuff that is high viscosity.... Often seen when doing fiberglass projects... where the activator is a small amount that needs to be blended in.... generally, stirring gets the accelerator distributed within the mass of the other stuff... But this doesn’t get it mixed down to the molecular level where you would like it to be... Enter the shear mixing method.... like using a butter knife...... to spread the stuff out really thin over a large area like on a pad of paper.... spread, scrape up, spread again, scrape again, a dozen times....(?) Most likely the Accelerator is one color, and what it is being blended into is another color... This is done intentionally to see how uniform the mixing is... keep mixing and shearing until you don’t see any striations.... Quite possible you can find this on a YouTube video... Shearing the material is a 3D method of mixing stuff at the molecular level... as the knife squeezes the materials, molecules roll around in an eddy current inform of the blade, before they get stretched really thinly over a distance... Shearing is a method of stretching the mixture into thin layers to improve on what the distribution did.... Stirring is a method of distributive mixing... distributing the stuff around... In the end it’s like Convection and conduction... or turbulent and shear flows... Unfortunately, I was unable to clearly define the basis of the two types of mixing.... so, I went with the unclear version.... Did that help any? PP thoughts only, stuff I learned working in a dental office... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Awful_Charlie Posted August 3, 2020 Report Share Posted August 3, 2020 (edited) Only a short reply as on a phone, but *dont* use extra accelerator - it will become unworkable too quickly (particularly as you have the a1/2) Use an old clean tin can to mix it with using a paddle mixer in a slow/medium speed drill. Don't scrape the tin out when applying it - this will be the unmixed stuff from the walls of the tin. The tin will be junk afterwards, but keep it until it has gone off so you can check it. Like many jobs, it is all about the preparation of the underlying materials - don't even think about scrimping on that, so mae sure you have plenty of lint-free rags and MEK before you open a panel. I used digital kitchen scales to measure the mix Edited August 3, 2020 by Awful_Charlie 2 Quote Link to comment Share on other sites More sharing options...
Steve2 Posted August 3, 2020 Report Share Posted August 3, 2020 For mixing small quantities I mix in a cat food can and measure the 2 parts using gram scales. https://www.amazon.com/AMIR-Upgraded-500g-0-01g-Stainless-Batteries/dp/B01HCKQG7G/ref=sr_1_7?crid=YJW1CA1ER2EV&dchild=1&keywords=scales+digital+weight+grams&qid=1596446810&sprefix=Scale%2Caps%2C234&sr=8-7 1 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted August 3, 2020 Report Share Posted August 3, 2020 I use Dixie cups and Popsicle sticks. I use the big tongue depressor sticks for the sealant and the stir stick ones for the activator. Getting a similar sized dollop on each one is about the right ratio. With two sticks, you can scrape the stuff off the other stick and use the edge of the Dixie cup to scrape the sealant off the sticks. After mixing for a bit transfer the sealant to a fresh Dixie cup and finish mixing. This way there is no unmixed sealant on the sides and corners of the cup. The Dixie cups are not affected by MEK if you want to thin it a bit. When you are done set the cup aside and the next day you can see how you sealant cured. 1 Quote Link to comment Share on other sites More sharing options...
Bravoman Posted August 3, 2020 Report Share Posted August 3, 2020 I write a check to my A&P 1 3 Quote Link to comment Share on other sites More sharing options...
xcrmckenna Posted August 3, 2020 Author Report Share Posted August 3, 2020 I write a check to my A&P Lol, that works the best I hear.... Sent from my iPhone using Tapatalk 1 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 3, 2020 Report Share Posted August 3, 2020 Summary of some interesting points... 1) good mixing is critical... 2) avoid using material that didn’t get the good mixing... Cure rate may slow on that stuff towards infinity.... 3) Changing the ratio of materials will change the cure rate to something unusable... 4) Poor mixing changes the ratio at the local level... 5) keep the excess mixed material on hand... this allows you to see how well it chemically cured... 6) Use clean and dry disposable materials to do the mixing in.... or mixing with... There is no saving them... 7) Preparation of the sealing surface is very critical too... don’t get distracted by this mixing challenge... 8) Check the expiration dates on the materials before using... Things can get stale over time or once opened... 9) outside of the ‘Best used before’ dates... let’s you do all the work and not get the desired results... Setting up for a big cleaning job... PP summary only, not a mechanic... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Jblanton Posted August 3, 2020 Report Share Posted August 3, 2020 If you don't want to redo it anytime soon, you need to pull the panel and inspect the sealant on it. It likely has the domed nutplates blown out because sealant got into the nutplate on last installation. I would use a slower, thinned B2 sealant so the bubbles will work out. You should use CS 3330 for the panels so they can be removed in the future without damage. I use a a 3 oz tube, or a syringe and make a bead around the panel, and use a plastic sealer roller to spread it out. This method keeps the sealant out of the nutplates. Its all in the Maintenance manual too. Jeff 1 Quote Link to comment Share on other sites More sharing options...
Missile=Awesome Posted August 3, 2020 Report Share Posted August 3, 2020 Or write a really big check to Paul at Weep No More. I love that do it yourselfers have the tenacity and patience to “go there”. GOOD on ya for that! Hope it goes smoothly. Nothing nicer than a “new” looking wing walk! Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted August 3, 2020 Report Share Posted August 3, 2020 @xcrmckenna, if it's just a few screws, you'll save a few years of your life just using Permatex 2 on them. No mixing required. IIRC for screws you're not supposed to apply it to the threads (I can't remember where I read that), just the face and the seat of the screw, so we're talking a TINY amount of sealant needed... 1 Quote Link to comment Share on other sites More sharing options...
xcrmckenna Posted August 3, 2020 Author Report Share Posted August 3, 2020 Summary of some interesting points... 1) good mixing is critical... 2) avoid using material that didn’t get the good mixing... Cure rate may slow on that stuff towards infinity.... 3) Changing the ratio of materials will change the cure rate to something unusable... 4) Poor mixing changes the ratio at the local level... 5) keep the excess mixed material on hand... this allows you to see how well it chemically cured... 6) Use clean and dry disposable materials to do the mixing in.... or mixing with... There is no saving them... 7) Preparation of the sealing surface is very critical too... don’t get distracted by this mixing challenge... 8) Check the expiration dates on the materials before using... Things can get stale over time or once opened... 9) outside of the ‘Best used before’ dates... let’s you do all the work and not get the desired results... Setting up for a big cleaning job... PP summary only, not a mechanic... Best regards, -a- I concur.Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
xcrmckenna Posted August 3, 2020 Author Report Share Posted August 3, 2020 [mention=12769]xcrmckenna[/mention], if it's just a few screws, you'll save a few years of your life just using Permatex 2 on them. No mixing required. IIRC for screws you're not supposed to apply it to the threads (I can't remember where I read that), just the face and the seat of the screw, so we're talking a TINY amount of sealant needed... I’ve used permatex on a friends tank and the screws still leaked. I didn’t want to deal with this again after I put down my new wing walk so I figured actual tank sealer would be the way to go. That way the wait time on the permatex to dry just enough to run it in isn’t as critical because the sealant will still dry without o2. But maybe I’ll be due for a complete reseal job if I screw it up enough:)Hope all is well. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
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