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Thread: L/D Ratio of an RV 3 ?

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    Re: L/D Ratio of an RV 3 ?

    Autoreply, Thanks again, I'm looking at that now. I will ask Jan what he uses for CDo to get his predicted L/D.
    Fly2kads, So vey true about the program, however it is well worth the asking price, I've had all sorts of fun playing with this. At the very least it gives a guide even with a WAG on L/D. It's good to get feed-back as to the accuracy of the program, I'm very impressed with it overall.
    Thanks for all the comments - it all helps.
    George

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    Re: L/D Ratio of an RV 3 ?

    X-Plane will give L/D in any speed or attitude. If you input correct numbers.

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    Re: L/D Ratio of an RV 3 ?

    Autoreply, I looked up Sadraey for CDo and there are some guides there -'e' should be easy enough with his formula and there is a scale 'from/to' for CDo. I will do some comparisons within that scale and see what eventuates. The JC prop Program does it's own L/D estimates so that may be helpful as a comparison.
    George

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    Re: L/D Ratio of an RV 3 ?

    Autoreply, Well I did the maths and will have to check everything again, but at this stage all I got was 9.42 L/D Ratio -(Bugger!!). 'e' was a little low at 0.64, Sadraey Gave from 0.65 to 0.7, as a guide.
    George

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    Re: L/D Ratio of an RV 3 ?

    Quote Originally Posted by Himat View Post
    The L/D ratio is related to the wing aspect ratio, but not a direct function of the wing aspect ratio. NACA/NASA published a long list of L/D and A/R for different planes.
    Have you a link ?

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    Re: L/D Ratio of an RV 3 ?


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    Re: L/D Ratio of an RV 3 ?

    Thank you !

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    Re: L/D Ratio of an RV 3 ?

    Quote Originally Posted by autoreply View Post
    Good planes have AR>>30
    I am not quite sure a 50+ feet span wing would look right on the RV-3.
    At least one of the great aeroplanes in history did have an A/R below 2.
    That plane did have a best L/D above 12.

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    Re: L/D Ratio of an RV 3 ?

    Quote Originally Posted by Lendo View Post
    Autoreply, Well I did the maths and will have to check everything again, but at this stage all I got was 9.42 L/D Ratio -(Bugger!!). 'e' was a little low at 0.64, Sadraey Gave from 0.65 to 0.7, as a guide.
    George
    Sounds about right. Which CD0 did you use? CAFE tested a few RV's. EFPA was consistently between 1.8 and 2.2. I wouldn't expect the RV3 to be much lower, maybe a clean one at 1.65 or so. Should be straightforward to compare the used CD0 to that value.
    Kennis vermenigvuldig je door het te delen.
    (You multiply knowledge by dividing it)

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    Re: L/D Ratio of an RV 3 ?

    If Van's Nr is correct they usually are, I make a wild guess and say L/D on a slippery RV-3 is 10.6-10.7 without propeller but with spinner, but never seen one like that.
    Jan.

    A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. Antoine de Saint-Exupery
    "Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible." Simon Newcomb, 1902

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    Re: L/D Ratio of an RV 3 ?

    I'm going purely on WAG. 6.5-7.8 L/D.

    I know that's lower than most guesses here, but I'm going "Price Is Right" low ball. If you take the prop off and tape some curved cardboard over the nose & air intakes.... 8.5/1.

    It's a fairly clean design, the RV guys say that landing gear intersection fairings make a big difference, ( a sign the big things are proper ) but it's a fairly low A/R and The Wing Is The Thing.

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    Re: L/D Ratio of an RV 3 ?

    Quote Originally Posted by Jan Carlsson View Post
    If Van's Nr is correct they usually are, I make a wild guess and say L/D on a slippery RV-3 is 10.6-10.7 without propeller but with spinner, but never seen one like that.
    If you take away the propeller, you have to add in the tow hook.

    CAFE developed a zero propeller-thrust sensor that used a proximity sensor to determine when the crank was floating between the front and back faces of the thrust bearing. Scroll down here to read about it http://cafe.foundation/v2/aboutcafe_orderfromchaos.php

    I don't know if they used it when testing the RV's, but the greater-span -9A had an idle power glide ratio of 12 : 1. The -6A had a calculated Oswald span efficiency of 0.851 and a glide of 11.39 : 1.


    BJC

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    Re: L/D Ratio of an RV 3 ?

    The 10.6 - or so L/D I got from my propeller design software, is a result from the performance page, the L/D with propeller stopped isn't useful for propeller calculation, only important when it stop spinning.
    Jan.

    A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. Antoine de Saint-Exupery
    "Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible." Simon Newcomb, 1902

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    Re: L/D Ratio of an RV 3 ?

    Quote Originally Posted by Jan Carlsson View Post
    The 10.6 - or so L/D I got from my propeller design software, is a result from the performance page, the L/D with propeller stopped isn't useful for propeller calculation, only important when it stop spinning.
    Yup, lots of things suddenly get important when the propeller stops.


    BJC

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    Re: L/D Ratio of an RV 3 ?

    Is that 10.6 at best L/D speed or cruise speed?
    I would think the prop is designed for cruise speed.

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