Scat Tubing for Air Vent Replacement

[Jeff_S]

Hello all. This is in an Ovation but it's really a general Mooney question so I'll post here rather than in the Modern forum.  Today I noticed an unusually strong breeze coming through my knees on takeoff, and traced the source to the scat tube that comes in off the right-side vent behind the firewall.  One of the metal ribs has completely escaped, putting a rupture in the tube, and there are several other holes.  I've attached the photo below.

So the quick question is, can I just get the appropriate tubing from Aircraft Spruce and replace this, or do I need an official Mooney part? The tubing has special treatment on both ends, but I don't know how important that is.  I actually tried to remove it myself but while I could undo the clamps, the tubing itself seemed to be stuck on there in some way and I didn't want to force it and break something else.

I appreciate your thoughts.  The photo is difficult to put into perspective, but you can tell on the right it's coming in from the sidewall and then connecting to a junction box up under the panel.  The main rupture is closer to the junction box...you can see the wire the busted out of the tube if you zoom in.  Thanks!

Jeff

[ArtVandelay]

I just went to Spruce, BTW...you might want to take a look at your defroster vent hoses as well.


Tom

[LANCECASPER]

@GEE-BEE might be able  to make a vastly superior one piece silicone hose for you

[hypertech]

I don't think the stuff from Spruce has the ends done.  I think Gee Bee can do that.  I know customducts.net can do it too.

[RLCarter]

Similar to firesleve dip? When I was replacing my fuel, oil lines and installing firesleve on all, an old A&P told me to mix red RTV with MEK till it had the consistency of water to use as a dip for the firesleve. Black RTV might work the same? Be warned it took 2 days for the MEK to completely dissolve the RTV (use a glass jar), and once dipped another day for the firesleve to dry. If your a roll your own kinda guy this might be an option, the dipped end do add to the fit and finish making it look custom

[carusoam]

@Jeff_S

Hey Jeff,

Looks like your tube answer may have arrived...   ^^^^

Something to consider.

Best regards,

-a-

[Jeff_S]

10 hours ago, GEE-BEE said:

We have 2” cuffs

black sceet

double wall 

with lined clamps

 

made to your spec

 

were the only mfg that can add a molded elbow.

 

GB

Thanks GEE-BEE.  I'll send a PM to continue the dialogue.

[mike_elliott]

Jeff, I replaced the same on the Bravo a few years ago, just ordered the Mooney part from Maxwell. It wasn't that outrageous, and helps keep the factory fed to make us parts. I might have paid $50 or so, cant remember so it wasn't much.  No research, no owner produced part, no hassle, a simple phone call and done.

[Jeff_S]

@mike_elliottThanks Mike.  I'm happy to support the factory as well and if it's really only $50 it would probably cost that much in my time and effort to get one fabricated. I did my normal MSC and they were the ones who suggested that any scat tubing would work, but again, the total cost seems like it would be close to the same.  I'll give Don a call.

[PT20J]

The problem with SCAT is that it is single wall with the wire exposed inside. Sooner or later, the wire rubs a hole through the thin wall. Also, without finished ends, the wire is loose at the ends and this is where the wire usually come loose and starts making a hole. You can bend the cut end of the wire away from the wall or run it out around the end of the tubing and bend it back to clamp it under the hose clamp. Neither method is as good as a finished end, though. 

SKEET is double wall and encases the wire between layers making it much less prone to vibration wear. With finished ends, it should last a very long time. SKEET is stiffer than SCAT and may require more or less support to get it to go where you want depending on the application. 

Skip

[Immelman]

+1 for the suggestion above. SKEET/SCEET is a much better product. Worth the few extra $$ per foot.

Edited June 25, 2019 by Immelman

[hypertech]

Sceet is better but it is also true that it is much stiffer.  I don't have any hands on experience with gee-bee's bent duct, but if you are going sceet for the replacement, I'd be curious if you could send the broken one and have it reproduced with the bends already formed in the proper place.  It would make it a lot easier to reinstall.

That tube should also just come off of there.  Its probably just stuck.

[Yetti]

For being open and available workspace, that is an incredibly hard tube to replace.   The oval vent on the side and being upside down with long arms and other such.   Spent an hour when it should have been 5 minutes.

[ArtVandelay]

For being open and available workspace, that is an incredibly hard tube to replace.   The oval vent on the side and being upside down with long arms and other such.   Spent an hour when it should have been 5 minutes.

It’s a lot easier with the seat removed. I proactively changed my hoses when I already had seats and glare shield removed for other maintenance.


Tom

[Yetti]

4 hours ago, ArtVandelay said:

It’s a lot easier with the seat removed. I proactively changed my hoses when I already had seats and glare shield removed for other maintenance.


Tom

Not much.   It has to do with the backside of the duct being short and the round tubing not fitting well over the oval hole.    I think I resorted to some aluminum tape to make it work.

[ArtVandelay]

Not much.   It has to do with the backside of the duct being short and the round tubing not fitting well over the oval hole.    I think I resorted to some aluminum tape to make it work.

Must be model dependent, don’t remember having a problem, maybe I just got lucky


Tom

[Jeff_S]

I appreciate everyone’s comments. I’ve learned a lot in my investigation, especially the difference between CAT-CEET-SCAT-SCEET!  I hadn’t realized there are four different types of this stuff.  From studying the damaged duct I’ve determined it is CAT tubing, where CEET (or SCEET) may be preferable with double lining to prevent the wires from being exposed to moisture.  I had hoped I could use some good old fashioned duct tape for a temporary repair whilst waiting for something permanent, but in attempting this I caused the very brittle material to break all the way in two. Time to spend a bit of money!

[skykrawler]

Late to the party....

 

When I changed mine the cuff was stuck to the  large nipple of the airbox and there was a lot of corrosion on this aluminum part. Moisture comes down that duct so the double wall made sense and it was a pain to replace.  There is a tendency misjudge the length with the bends and cut that host too short.  I think the cuffs are just a silicon tape.

I did the defroster vent hoses during last years annual the were dry rotted and spewing black fragments on top of the glare shield.  The hard part was there is a single screw holding the CAT to the defroster vent with a corroded head (after 37 years).  I used the original type hose here for its flexibility.  37 years after all.