[prkaye]

I'm trying to route the scat tube from my heat muff to the heater box. It seems impossible not to have the tube touch the fuel line coming out of the gascolator, and the wires going into the relays. Is this bad practice, having the SCAT tubing touch wires and fuel lines? THe only way I can see to maybe avoid it would use about twice as much length of SCAT...

 

[noelf]

Do not let them touch...

...EVER!! A friend has an RV-7 that was just starting to leak brake fluid. We found that the SCAT tubing was just touching and the engine vibrations allowed the steel wire spiral of the SCAT tube to wear a hole in the brake line. The interesting part is that the SCAT tube red silicone rubber material did not get punctured or worn through.

 

[N941WR]

...The interesting part is that the SCAT tube red silicone rubber material did not get punctured or worn through.

That is correct. What happens is as the two things rub together, microscopic pieces from the harder material get pushed into the softer material. Then the softer material acts just like a saw and cuts right through the hard material.

In my case, I used zip-ties to secure the SCAT tube to the engine mount, up out of the way. One zip-tie around the engine mount and another around the SCAT tube, and yet another zip-tie on an upper engine mount tube held it firmly in place with no rubbing. When I removed it for the engine swap there was no wear on any component after 250 hours.

 

[rglick]

What works for me.....

is a piece of .020 3/8" wide and long enough to wrap around the Scat tube. Drill a hole in the two ends then attach a #12 (I think) adel clamp to the engine mount. This should keep the Scat away from everything.

 

[prkaye]

Ok thanks guys.

1) The routing I have come up with is about a 30 inch lengh. Will I lose all my heating effectiveness by having the scat tube from the heat muff being this long?

One zip-tie around the engine mount and another around the SCAT tube

Must be one heck of a long ZIP tie to make it around that SCAT tube. The longest ZIP ties I have are just a bit too short.

is a piece of .020 3/8" wide and long enough to wrap around the Scat tube

2) Is that what this part is for? SS304-26GAX1/2X9 SCAT CLAMP? It says "Caution - Sharp" on it, so I wonder wouldn't this cut through the SCAT tube?

 

[N941WR]

...Must be one heck of a long ZIP tie to make it around that SCAT tube. The longest ZIP ties I have are just a bit too short.

I used two zip-ties to go around the SCAT tube. What wasn't clear in my post above is that I secured the scat tube to two engine mounte tubes so it wouldn't move around.

The tip with using a band and Adel clamp to hold the SCAT tube in place will also work fine. As you heard, just make sure it doesn't touch anything.

One other tip, wrap just your heater muff in exhaust wrap, available on line or from your local speed shop. That will help keep the heat in. You could also try doing the same to your SCAT tube.

 

[frankh]

Ok thanks guys.

1) The routing I have come up with is about a 30 inch lengh. Will I lose all my heating effectiveness by having the scat tube from the heat muff being this long?



Must be one heck of a long ZIP tie to make it around that SCAT tube. The longest ZIP ties I have are just a bit too short.



2) Is that what this part is for? SS304-26GAX1/2X9 SCAT CLAMP? It says "Caution - Sharp" on it, so I wonder wouldn't this cut through the SCAT tube?

The reason its ys "sharp" is becausse its probably stamped out of a piece of stanless..You have to debur to use.

In fact I made a few more stainless clamps out of a piece of old SS duct I found in the dumpster at work...They work rather well and are light weight.

Frank

 

[prkaye]

OK thanks guys. Final question - what about the length. Does a 30" routing seem unreasonably long?

 

[gasman]

OK thanks guys. Final question - what about the length. Does a 30" routing seem unreasonably long?

That sure sounds a little long. Do you have a picture? On a guess, I think mine is about 15 to 20 inches from muff to heater control.

30" = expensive scat!

If that was the shortest distance that you could make it, then you don't have mutch of a choice. You should be ok. Be sure to block the air flow from the wing root and any other canopy leak ahead of the cargo bulkhead.

 

[prkaye]

I got it down to 27 or 28 inches, but the length is required to loop it up and over the fuel hose. If i try to go under the fuel hose my control cables interfere. Hard to get a clear picture, but here are photos from two different angles. In the first photo it's the scat tube that's further back...

 

[Tom Martin]

I use little spots of RTV between items in the engine compartment the might rub together. Tie wraps will also wear through Scat hose if you do not somehow stop the chaffing. Try RTV, works great, a little dab will do ya!

 

[AlexPeterson]

I use little spots of RTV between items in the engine compartment the might rub together. Tie wraps will also wear through Scat hose if you do not somehow stop the chaffing. Try RTV, works great, a little dab will do ya!

I'll vouch for the RTV method - it is simple, light and completely effective. Easy to carve off when necessary also. Use something temporary to put a little (1/8" maybe) space between the parts, then put a dab of the rtv in the gap. When cured, remove the temporary something. In my plane, this has lasted more than 1100 hours so far, with zero problems.