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Thread: Pre testing issues

  1. #1

    Join Date
    Oct 2016
    Location
    Nairobi
    Posts
    21

    Default Pre testing issues

    Hi Guys,

    Hope you are all well.

    I have just finished building my S7 in Nairobi, and am now at the testing phase. The air temp here is about 30 degrees celsius and the altitude is 5,600 ft.

    I am finding that my temps are a bit higher than I would like when running up. The CHT and oil temps are at the upper limit of normal and I am a bit nervous to try flying until they come down a bit.

    I am therefore planning to move the oil cooler tomorrow from in front of the radiator at the back to just behind the cowling at the front. I have made some brackets and will try and route the oil pipes around the gearbox. Hopefully this will improve the oil cooling a bit. I have also enlarged the air entry hole in the cowling to the water radiator to try and get some more air in. has anyone else had similar problems with overheating and have any tips please?

    I am also getting a lot of noise from the lexan turtle deck. it vibrates and flexes and makes an awful rattling noise. I was going to add a rubber strip to the front where it engages in the windscreen in case that is where the noise is coming from, and then also rivet some aluminium angle bar across the very front and back on the inside to give it a bit more rigidity and stop it flexing in the wind. has anyone else had similar problems and have any tips please?

    Many thanks in advance for your replies, and fly safe.

    Kindest regards

    Amer

  2. #2
    Senior Member Dave S's Avatar
    Join Date
    Oct 2008
    Location
    St Paul, MN
    Posts
    1,833

    Default Re: Pre testing issues

    Amer,

    I believe the oil coolers have been mounted in various places with different models of kitfox aircraft. Our S7 is an early version for which the construction manual designated locating the oil cooler behind the cowling in the front. Photo attached.

    A couple other thoughts.

    1) Rotax way back recommended using Evan's waterless coolant (100% propylene glycol). More recently Rotax included 50% Ethylene glycol as an approved coolant. Everyone I know who made the change from the Evan's coolant to 50% Ethylene Glycol realizes a reduction in both CHT and Oil Temperature.

    2) Early radiators were traditional brass/copper construction. More recently Kitfox has been producing been using aluminum radiators. These also have better heat transfer.

    In our case, I did two things at once (so I have no idea which contributed what) - changed the radiator from the original old version brass to the newer aluminum (due to condition issues); AND, changed from Evans coolant to 60% Dexcool....very significant reduction in both CHT and oil temp. If you check the products review section of this list, I reported the details there.
    Attached Images Attached Images
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3

    Join Date
    Jul 2016
    Location
    Reddick, FL
    Posts
    82

    Default Re: Pre testing issues

    For what it's worth. I used propolene glycol in a Ford engine mod for an aircraft and suffered extreme rusting of internal iron and steel parts. Learned later that many auto engines showed similar problems. Using dexcool ethylene glycol since. Dexcool was recommended on this forum...excellent choice.
    On air through the radiator, opening the inlet side should not get it more than 1/3 the size of the exit side opening to create the drafting of the air AWAY from the backside of the radiator. Pushing air through the radiator is a loser... Note, auto radiator fans pull air away from the radiator. I am frustrated that so few homebuilders can recognize this. Try it, it works.
    Bud
    IV Speedster
    912 UL
    IVO ground adjustable

  4. #4
    Senior Member efwd's Avatar
    Join Date
    Jun 2015
    Location
    Yorba Linda, CA
    Posts
    2,817

    Default Re: Pre testing issues

    I recognized it as soon as I tried the fans on the cabin heat radiator. I figure It would overheat the fans if they were reversed though.
    Eddie

  5. #5
    Guy Buchanan's Avatar
    Join Date
    Mar 2009
    Location
    Ramona, CA
    Posts
    119

    Default Re: Pre testing issues

    Bud's right. Ignore the inlets. Work on the outlet. Increase it's size or add vertical deflectors to lower the pressure at the exit. Also make sure air is not going around the radiator/cooler following an easier path. A significant chunk of the air going in the inlets must go through the radiator.
    Guy Buchanan
    San Diego, CA
    Deceased K-IV 1200 / 912uls / 70" Warp 3cs

    gebuchanan@cox.net

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