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Thread: Exhaust systems and Federal Skis

  1. #1
    WindOnHisNose's Avatar
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    Exhaust systems and Federal Skis

    In November of 2019 Grant Wallace was kind enough to install the Sutton exhaust system in Santa's PA18. Shortly after that we installed the Federal 2200 hydraulic skis, just as we have for many years. The skis were made in 1957 and you may recall the thread Darrel Starr and I posted here regarding the renovation of those skis. The skis employ a large spring on each side, attached at the motor mount aft and the tip of the ski.
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    Grant suggested that I purchase the removable tail pipe from the Sutton's, and I did. We chose to angle the exhaust laterally, so as to avoid having the exhaust entering the cockpit.

    When I removed the skis in the spring of 2020 I noticed the right spring was "sprung", so to speak, in one distinct area.
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    I attributed this to the age of the springs (we chose not to replace these when we renovated the skis). I promptly forgot about the spring until I installed the skis just before Santa's flyin in December and I called Grant to ask where one would order new springs. I described the defect and he speculated that the defect most likely resulted from the exhaust stream, which was aimed right at the spring. Of course, it wasn't an issue when the skis/springs were not installed.
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    I spoke with Dave Sutton and he acknowledged that this can be a problem not only with the spring installations, but also with those skis with bungees instead of the springs. He suggested re-indexing the removable exhaust (which we did) vs purchasing the extended exhaust pipe). I spoke with SJ regarding this and he pointed out that this might now cause increased levels of CO in the cockpit, and I will keep an eye on this. The solution may still be using the extended exhaust pipe.
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    I have since ordered, received and installed new springs. All is good now, but I thought this is something that should be mentioned here.

    Randy
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    55-PA18A's Avatar
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    That spring must have gotten pretty hot to stretch like that. Do you think it did anything to the cables?

    Jim
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    RaisedByWolves's Avatar
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    I have Sutton and springs for my skis, going to the front gear fitting, there is exhaust stain on them but thatís all. Maybe with it on the engine mount itís that much closer?


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    cubdriver2's Avatar
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    My buddy Dave had a funky right side spring on his Summit skied Super Cub after 2 ski seasons. Cooked by the exhaust. Good catch Randy

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    cruiser's Avatar
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    Perhaps a piece of fire sleeve or other steel type sleeve would help mitigate that problem Randy.
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    Mattpeed's Avatar
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    We used to sleeve then right side flying wires on our AgCats with 321 stainless. They were right in the ex stream.


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    Matt
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    aktango58's Avatar
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    Quote Originally Posted by RaisedByWolves View Post
    I have Sutton and springs for my skis, going to the front gear fitting, there is exhaust stain on them but that’s all. Maybe with it on the engine mount it’s that much closer?


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    Engine mount as the attach point has a much lower angle, requiring less spring tension when deflected down, especially for retractable skis.
    I don't know where you've been me lad, but I see you won first Prize!
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    TVATIVAK71's Avatar
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    I can imagine it throws that heat pretty far. In powdery snow our right lower gear leg around brake caliper always gets caked up like a block of rime ice. Starting our third ski flying season bungee still seems fine but does have a grayish color in that exhaust outlet area. That exhaust staining pretty much covers lower half of gear leg. Toyed around putting some fire sleeve, not sure it would help or not. Havenít seen any sleeve on any similar setups, around ANC area anyway.
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    WindOnHisNose's Avatar
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    Quote Originally Posted by 55-PA18A View Post
    That spring must have gotten pretty hot to stretch like that. Do you think it did anything to the cables?

    Jim
    I don't think so, but didn't take a chance....I rebuilt all the cables! Learned about swaging stainless steel cables...despite what Aircraft Spruce says, one needs to use tin plated sleeves on stainless steel cables, NOT zinc plated sleeves (per Nicopress).

    Thanks for asking this question!

    Randy
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  10. #10
    WindOnHisNose's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    My buddy Dave had a funky right side spring on his Summit skied Super Cub after 2 ski seasons. Cooked by the exhaust. Good catch Randy

    Glenn
    Glenn, thank YOU for your advice on rigging the skis. I appreciate your expertise very much!

    Randy

  11. #11
    WindOnHisNose's Avatar
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    By the way, the Sutton's are a real joy to work with. It is a great family operation, and they have always been very receptive to my calls and questions.

    I'm going to call them today and order the extended detachable tailpipe. While I think the Alaska Bush Pod does a pretty good job of sealing up the bottom of the aircraft, I don't want to take a chance and will use the extended pipe.

    Have a great day, folks!

    Randy

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    skywagon8a's Avatar
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    Quote Originally Posted by WindOnHisNose View Post
    While I think the Alaska Bush Pod does a pretty good job of sealing up the bottom of the aircraft, I don't want to take a chance and will use the extended pipe.

    Have a great day, folks!

    Randy
    Randy,
    The exhaust ingression to the cockpit generally comes in through the openings at the tail, then migrates forward. The cockpit due to the shape of the fuselage, creates a slightly lower air pressure which draws the fumes forward. This flow is often arrested with a barrier across the fuselage aft of the baggage compartment. Your 210 likely has this barrier. The 180/185s have two scoops high on the aft fuselage to pressurize the fuselage with clean exhaust free air for this purpose.

  13. #13
    WindOnHisNose's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Randy,
    The exhaust ingression to the cockpit generally comes in through the openings at the tail, then migrates forward. The cockpit due to the shape of the fuselage, creates a slightly lower air pressure which draws the fumes forward. This flow is often arrested with a barrier across the fuselage aft of the baggage compartment. Your 210 likely has this barrier. The 180/185s have two scoops high on the aft fuselage to pressurize the fuselage with clean exhaust free air for this purpose.
    Thanks for this note. I assume this explanation also applies for why the back seat is relatively cold. I modified a blanket that extends from the aft top of the cockpit down and behind the rear seat, extending laterally to the side of the cockpit. Julie keeps much warmer with that configuration.

    Have any of you noticed CO levels being elevated in the rear seat?

    Randy

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    akavidflyer's Avatar
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    You can get a cheap CO monitor from ebay, amazon or lowes etc. For around 40 bucks you can monitor the levels in real time and see what your getting instead of guessing at it.

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    Quote Originally Posted by WindOnHisNose View Post
    Have any of you noticed CO levels being elevated in the rear seat?

    Randy
    Nope and I have moved the portable around that I use in my 180 a good bit in the Cub to confirm the readings from my hard mount probe which is located under the panel and annunciates on the CGR30P.
    Remember, These are the Good old Days!

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