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Permatex Red RTV

Cardiff Kook

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Put some new scat tube in 185- it was resting on engine mount. Tubing I took off had some perfectly globbed silicone of some sort on those places.

A&P suggested permatex red rtv. I tried it and it made an absolute mess.

See my application vs on scat i took off. What gives? The one on the scat i took off were probably a quarter inch thick perfect gobs (see pics)- mine is just a mess (see pics)- and i am unsure if it will even prevent rubbing on engine mount.

Super frustrating! Probably need to order new scat again so it doesnt look like crap.
 

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The thick glob was likely placed there to prevent chafing. It is difficult to prevent chafing of that scat tube because of it's length and routing. If you clamp the scat to the engine mount tube using two clamps like these, the chafing issue is prevented.
1738493848881.webp https://www.aircraftspruce.com/catalog/appages/ms21919clamps.php?clickkey=887465

Also, before and when the scat is clamped at it's ends, rotate it to a position where it will lie relaxed without being pressed against the mount. It's frustrating but doable.
 
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Red RTV is commonly used to prevent chafing against a tube that it crosses. Not sure why your attempt didn't work, it should come out of the tube much thicker than toothpaste and a blob should stand up on it's own. It will dry in the form it takes. If a tube of RTV has frozen it doesn't act right, I'm guessing yours did.
 
If the scat is so tight to the tube that it squishes the silicone out? The scat needs to be a little longer. Make a temporary shim to maintain the clearance you want while the silicone cures.
 
The permatex is very hard to squeeze out of the tube. Is that normal? Or was it frozen as someone mentioned?

I cannot figure out how anyone could get a perfect dollup like that pictures.

Stewart- there is very little space between tube and engine mount due to the nature of the routing
 
Common high % rubbing alcohol on rag can remove uncured RTV. Your RTV tube belongs in the dumpster, get some replacement. It separated from its carrier for some reason. I've seen that before.....it separates and some liquid/some RTV comes out. Best to mechanically clamp as some RTV can separate over time from components due to mineral solvents. The ultra black RTV claims better fuel/mineral resistance. The red is more for high temps.

Edit: There's a cure period required for it to set up and stick.

Gary
 
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The permatex is very hard to squeeze out of the tube. Is that normal? Or was it frozen as someone mentioned?

I cannot figure out how anyone could get a perfect dollup like that pictures.

Stewart- there is very little space between tube and engine mount due to the nature of the routing
There is a red Permatex and a high temp orange! I find the high temp orange is better. The red stuff always seems hard to get out of the tube as you have noticed. Orange high temp permatex p/n 81422
 
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I've used hi-temp but for most chafe blobs I use clear. No need for hi-temp in most cases. I still say lengthening the tube to create some space is the answer. If the tube is squeezing the silicone out? It's pulled too tight and is set up to fail.
 
I've used hi-temp but for most chafe blobs I use clear. No need for hi-temp in most cases. I still say lengthening the tube to create some space is the answer. If the tube is squeezing the silicone out? It's pulled too tight and is set up to fail.
Excellent observation.

My neighbor was looking at my engine install the other day and mentioned the need for shrink wrap on the ground cable crimped ends. While everything looks just ducky sitting in the hangar, he reminded me of the vibration and movement of the engine with torque loads for flight, and how even the small movements requires attachment stuff to have flex.

Scat hose would have the same needs!
 
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