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  1. Sep 20, 2004 #1

    nickofhf

    nickofhf

    nickofhf

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    My corvair powered Twin might not be a standard config twin.Mabey it will be like a single thrust-line or crazy boom config.Does anyone have any info on Rutans boomerang?
     
  2. Sep 21, 2004 #2

    wsimpso1

    wsimpso1

    wsimpso1

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    EAA Member? If yes, no problem. It was on the cover of Sport Aviation, I think about three years back, and there was lots of data. Go to www.eaa.org, find the Sport Aviation page, and you might be able to just order a back copy. If not, the library can get you copies of the article. If you are not a member, shame on you...

    Remember though, it was made of pre-preg carbon on molds, and so is lighter than what any of us can hope to build using moldless methods and fiberglass. A lot of the extra weight would end up aft too. Once you get past the concept sketch, you would have to engineer everything and adjust things like wing spar position, sweep, dihedral, etc to get a useable CG.

    Billski
     
  3. Sep 22, 2004 #3

    nickofhf

    nickofhf

    nickofhf

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    Thanks,I am a member and I will look into that article.I was thinking of something like it but I didnt want to make the boomerang because I figured it was beyond my scope of technology.
    I read somewhere that there are more deaths related to twin engine aircraft than single engine.If thats the case than there goes the saftey factor of a twin.
     
  4. Sep 22, 2004 #4

    wsimpso1

    wsimpso1

    wsimpso1

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    nichofhf,

    Well, the joke used to be:

    Q- What is the good engine for when an engine dies in a twin?
    A- It carries the airplane to the site of the crash...

    At one time, twins had startling levels of fatalities, then certain improvements were made. Blue line speeds were established for each model, and engine out training was developed around blue line knowledge. Insurance requirements for the level of training forced more extensive training too. This reduced the frequency of airplanes departing from controlled flight and reduced the number of pilots stowing the good engine, both of which helped out immensely.

    And then, Burt Rutan started looking for safer configurations, resulting in the Defiant and Boomerang. The Defiant worked well because of centerline thrust, but its efficiency suffered some, as with all push-pull twins.

    Boomerang is designed to have aerodynamic symmetry despite the inherent asymmetry of prop torque and q forces, etc and outstanding engine-out charecteristics. The Sport Aviation article described how little rudder it takes to center the ball with either engine feathered, blah, blah, blah. Burt knows his topic... One of the biggest issues is just that he has a smaller lever arm between the two engines for when one is dragging and the other is pulling, but he had lots of other things going on too. The article is loaded with info...

    I think that you could design and build a safe and excellent twin using his basic scheme.

    Now limiting yourself to 240 HP seems a bit light (unless your bird will have only two or three seats) - you have to come up with acceptable single engine climb performance when one is caged, and that means wing loadings low enough to climb 300 fpm or so on 120 HP at whatever max airport altitude you select...

    The world of airplane design and development awaits you...

    Billski
     

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