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Thread: J5A with A-75 Scat Hose Issues

  1. #1
    rrb's Avatar
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    J5A with A-75 Scat Hose Issues

    Recently noticing some ratty scat hose, I decided to replace it. Mistakenly, I dutifully ordered the hose I thought was specified in the parts list -- it was indicated as 2 1/8 I ordered the 2 " hose from spruce and as it turns out it doesn't fit over the fittings. I've heard of similar problems occuring with old cubs and old engines. I'm trying to determine what the usual course of action is -- I've heard recommendations of getting a mechanic to fabricate an insert and I suppose another option would be to just purchase larger scat hose and really clamp it on.

    Any suggestions or any ideas why the hoses don't fit (i.e. has something changed in the manufacturing process or in 1941 did Piper use something other than standard scat hose?)

    Trying to get this project tackled so I can move on to the next -- bungees.

  2. #2
    behindpropellers's Avatar
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    Try cutting the wire out of the hose where it goes on the fitting. Sometimes you can get it to stretch over.

    Tim

  3. #3

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    Thats what we did on our J5A, stretched it after cutting and folding back the inner wire. Takes a little effort but will go on.

  4. #4
    Steve Pierce's Avatar
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    Piper originally used an aluminum tubing that is still available from Univair. I have seen people use 2 1/4" and use silicone baffle material to make up the difference or just cut the wire back and clamp it.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  5. #5

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    Everybody uses the Scat hose with the wire moved back. Put a nice radius on the wire, or it might poke through.

    Next question: Is it legal? They didn't have Scat tube when the Cubs were built. Sounds like a minor mod to me, but it does have to do with the induction system.

    And a comment: If these are the ducts from that hole in the cowl to the muffler muff, have you ever wondered just exactly what they do? And if the airplane would actually crash if they were left off?

  6. #6
    Steve Pierce's Avatar
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    I don't run the hose from the cowl to the heater muff in the summer. Someone on the Short Wing site said it helps cool the muffler. I think it helps blow hot air in the cabin.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  7. #7
    Jon B.'s Avatar
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    Steve Pierce:

    I leave the tubing in place from the nose to the muffler shroud but remove the muffler-to-cabin heat hose from the cabin heat 'valve'. The open end is wired to the engine mount, dumping the hot air out the bottom cowl exit.

    The muffler and shroud stay cool and the heat stays out of the cabin.

    I struggled mightily with the SCAT tubing 'til I was told about removing the wire. After that, it went over the fittings with ease! I bent a radius in the end of the wire to keep it from poking through the tubing. Presto!

    Jon B.

  8. #8
    Steve Pierce's Avatar
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    My muffler shroud exit is right on top of the cabin heat valve on the firewall so it is a real pain to get a hose on and off.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  9. #9

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    Not sure I follow you - If you are using what amounts to ram air on that muff, then the only outlets should be to cabin heat and carb heat. An outlet to the outside world might rob just enough heat to allow carb ice, and that might be bad.

    If, on the other hand, the scat tube was not even there, then the carb heat would be sucking air from all openings, and would be warmer. Be careful in there, and think it through.

  10. #10

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    Like Steve said, Piper used 2" aluminum segmented tubing that fit inside the fittings and was held by a PK screw. To use 2" Scat hose on J-3, J-5 and PA-12's, I take a 1" wide piece of aluminum and roll it to fit iniside the Scat hose to make a 1" wide ring. We then glue it inside the tubing with red silicon and a couple of pop rivets to hold it in place. The Scat hose will now fit insde the original fittings and you can then srcew a PK screw into the aluminum to hold it in place like the original. Univair still sells the proper Aluminum tubing which works like it is supposed to also.

  11. #11
    Jon B.'s Avatar
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    Quote Originally Posted by bob turner
    Not sure I follow you - If you are using what amounts to ram air on that muff, then the only outlets should be to cabin heat and carb heat. An outlet to the outside world might rob just enough heat to allow carb ice, and that might be bad.

    If, on the other hand, the scat tube was not even there, then the carb heat would be sucking air from all openings, and would be warmer. Be careful in there, and think it through.
    Bob:

    If this was directed at my setup, don't be alarmed. The K-A Champ has two (Hanlon-WIlson) mufflers. Carb heat is on the right side, cabin heat on the left. I leave the carb heat alone!

    Jon B.

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