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Thread: Updated photos of Twin JAG

  1. #1

    Join Date
    Oct 2011
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    29

    Updated photos of Twin JAG

    Here are a few new photos of my twin engine project. More to come shortly at www.homebuiltdirectory.com.
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    Last edited by jimdc8; 08-24-2013 at 08:29 PM.

  2. #2

    Join Date
    Oct 2011
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    Newest photo as of today (bottom photo)! Engines being built shortly.
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    Last edited by jimdc8; 08-24-2013 at 08:26 PM.

  3. #3

    Join Date
    Nov 2011
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    3

    Finally! I wondered when this sort of thing would happen

    Quote Originally Posted by jimdc8 View Post
    Newest photo as of today (bottom photo)! Engines being built shortly.
    That is a very interesting project! I have been toying with the idea of designing a light twin for some time now, given the rapidity with which engines are growing more efficient, airframes are getting lighter and stronger, etc...

    Looks like you've adapted an RV-7 or something(?)

    Would love to see more photos! Keep up the good work. Can't wait to see that fly!

  4. #4

    Join Date
    Oct 2011
    Posts
    29
    Thank you for the kind words! I will be adding more pictures very shortly. I am currently finishing the instrument panel/center console installation, minus avionics for now. Used to be a RV-6A. Now it is called a Twin JAG.

    More coming soon.
    Jim

  5. #5

    Join Date
    Sep 2011
    Posts
    282
    Quote Originally Posted by jimdc8 View Post
    Thank you for the kind words! I will be adding more pictures very shortly. I am currently finishing the instrument panel/center console installation, minus avionics for now. Used to be a RV-6A. Now it is called a Twin JAG.

    More coming soon.
    Jim

    Now that's thinking outside of the box! COOL Project. Best of Luck!!
    Last edited by RV8505; 09-08-2013 at 07:53 PM.

  6. #6

    Join Date
    Oct 2011
    Posts
    29
    Here are some more recent photos. Trial fitting the burlwood panels on the center console. More pics coming soon...
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  7. #7

    Join Date
    Dec 2011
    Location
    Mt Pleasant, NC
    Posts
    8
    What engines are you planning on using?
    -Jim

  8. #8

    Join Date
    Oct 2011
    Posts
    29
    Quote Originally Posted by wildhorsesracing View Post
    What engines are you planning on using?
    I am building custom 120hp Corvair based flight engines. They are direct drive 6 cylinder air cooled and are very smooth running engines. They contain a fifth bearing to handle loads imposed on the crankshaft by the props. My engines will use the following brand new custom parts:

    1. 4340 billet ion-nitrided crankshafts
    2. Custom pistons & cylinders
    3. 4340 connecting rods
    4. Falcon machine heads
    5. High volume oil pumps
    6. Weseman 5th Bearing
    7. ...much more!

    I will begin building these engines in the next few weeks.

    Jim
    Last edited by jimdc8; 12-25-2013 at 08:44 PM.
    Please showcase your homebuilt aircraft or project to the world at www.homebuiltdirectory.com...it's free!

  9. #9

    Join Date
    Jul 2011
    Location
    NW FL
    Posts
    237
    Very nice project!
    .
    Your Dec 17 post included a picture of your console with the #1 & #2 PROP BRAKE controls. I had only seen passing reference to brakes in obscure texts. A recent forum thread regarding the Bally B-17 replica had pictures of those powerplants and some folks thought the brake drum looking things aft of the props were freewheeling devices. There were some opinions expressed that a free wheeling prop on a shut down engine was desirable.


    Could you bring us up to speed regarding the relative drag of a feathered prop vs a braked prop vs a free wheeling prop. I can't wait to see pictures of your brake system. It could turn out to be lighter than a cs feathering prop. As if there were one even available for a 120 hp Corvair. Can't go wrong with the Corvairs.


    Bob

  10. #10

    Join Date
    Oct 2011
    Posts
    29
    Thanks Bob!

    As you know, a constant speed prop is both heavy and complex. It is also a failure point and it's weight puts stress on the crankshaft. My concept of a prop brake is a simple one...I will install a mechanical brake caliper, identical to a bicycle's, which will stop the windmilling prop using the machined surface of the flywheel (just under the teeth where the starter meshes with).

    Here are a few of my thoughts for this setup:
    1. A feathered prop, using a constant speed prop, effectively reduces drag approximately 97% compared to an unfeathered windmilling prop.
    2. A stopped unfeathered prop, using my proposed braking system, effectively reduces drag approximately 93% compared to an unfeathered windmilling prop.
    3. I feel that with a simpler and lighter setup, I would be willing to live with the 4% degradation in performance. I can makeup the difference by setting limitations to the operation of the aircraft (ie. minimum runway lengths).

    These are just some generic thoughts of mine that describes why I am choosing this route. It is much more in depth than I can describe on this forum. Hope this helps.

    Jim
    Please showcase your homebuilt aircraft or project to the world at www.homebuiltdirectory.com...it's free!

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