Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Purpose of Cowl Bumps

  1. #1
    Senior Member JoeRuscito's Avatar
    Join Date
    Jun 2018
    Location
    Charleston, SC
    Posts
    361

    Default Purpose of Cowl Bumps

    The manual says optional. Do they provide clearance for a part of the engine? Im installing the 912is. It seems some install and some do not.

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

    Default Re: Purpose of Cowl Bumps

    I simply installed for the looks. I look into the cowl and note that the clearance is very close but likely doable without. Nice thing is, you can get the install of the cowl completed and add them anytime before paint.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  3. #3

    Join Date
    May 2011
    Location
    Green River UTAH
    Posts
    140

    Default Re: Purpose of Cowl Bumps

    The purpose of the bump cowl is to give the plane the look of having a radial engine, some like it others like the smooth look better, It is just an engine cover with drag reducing qualities either way. That's my opinion and I'm sticking to it.

  4. #4
    Senior Member jrevens's Avatar
    Join Date
    Aug 2009
    Location
    Arvada, CO
    Posts
    2,146

    Default Re: Purpose of Cowl Bumps

    Quote Originally Posted by 896tr View Post
    The purpose of the bump cowl is to give the plane the look of having a radial engine, some like it others like the smooth look better, It is just an engine cover with drag reducing qualities either way. That's my opinion and I'm sticking to it.
    896tr - I believe they are talking about the smooth cowl, not the traditional "radial-look" round one. Sometimes "bumps" are needed for engine or accessory clearance with engines other than the standard 912. As far as drag-reducing qualities go, the smooth cowl is definitely less "draggy" and more aerodynamic than the round one.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #5
    Senior Member JoeRuscito's Avatar
    Join Date
    Jun 2018
    Location
    Charleston, SC
    Posts
    361

    Default Re: Purpose of Cowl Bumps

    Quote Originally Posted by jrevens View Post
    896tr - I believe they are talking about the smooth cowl, not the traditional "radial-look" round one. Sometimes "bumps" are needed for engine or accessory clearance with engines other than the standard 912. As far as drag-reducing qualities go, the smooth cowl is definitely less "draggy" and more aerodynamic than the round one.
    Correct, referring to the new smooth cowl. I like the smooth look, just looking ahead and wondering if there was a clearance issue.

  6. #6

    Join Date
    Jun 2018
    Location
    San Diego, CA
    Posts
    75

    Default Re: Purpose of Cowl Bumps

    From Wikipedia:

    "The design was originally intended to use a new radial engine then in development and the early Kitfoxes had round cowls with bumps to accommodate the cylinder heads. Although this radial engine did not materialize, and a Rotaxtwo-stroke engine was adapted instead, the "retro" radial cowling proved popular and was retained on many models."

    Mike

  7. #7
    Senior Member
    Join Date
    Apr 2009
    Location
    Chisholm Mn
    Posts
    1,562

    Default Re: Purpose of Cowl Bumps

    Wikipedia doesn't mention it, but the very first Kitfox 1s had a traditional looking cowl. My serial # 11 kit came with it. It actually was a nice looking cowl. Here is a picture of one, but not mine. JImChuk


  8. #8
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Re: Purpose of Cowl Bumps

    Jim - That cowl is almost a carbon copy of the Model C/Mark 4 Avid "cheek radiator" cowl, isn't it?
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  9. #9
    Senior Member
    Join Date
    Apr 2009
    Location
    Chisholm Mn
    Posts
    1,562

    Default Re: Purpose of Cowl Bumps

    No, they aren't the same. Wonder if some other kit used this Kitfox cowl? My serial # 11 Kitfox cowl came from Kitfox, it was listed in the parts list. Also, I've seen several other early Kitfox 1s with the same cowl. Here is a picture of an Avid MK IV cowl. JImChuk

    PS Hope the Idaho trip was a good time, been waiting to hear more about it.

  10. #10
    Senior Member
    Join Date
    Apr 2009
    Location
    Chisholm Mn
    Posts
    1,562

    Default Re: Purpose of Cowl Bumps

    I found a picture of my actual Kitfox cowl, it's been modified near the back end to fit a Jabiru engine, but this is the one that came with serial # 11. JImChuk

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •