Fauvel AV-36 and 361 plans project

Discussion in 'Member Project Logs' started by Hot Wings, Jul 7, 2019.

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  1. Oct 16, 2019 #21

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

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    Very slow progress recently. Between taking care of real income producing work, and other distractions, I'm STILL working on the vertical stab and rudder. A couple of the little details between the AV-361/45 and the AV-36 have required more 'blending' work than expected.
    A 7 degree cant in the spar between the 2 versions means the operating rod mounts need to change by the same angle and the loads are not trivial due to the short arm at the hinge line and the need to deflect the rudder 45 degrees in one direction.

    Pretty picture for the day:
    Rudder full loft.JPG
     
    Himat, Vigilant1 and Peter Mican like this.
  2. Nov 5, 2019 #22

    Hot Wings

    Hot Wings

    Hot Wings

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    Thee is some confusion about the ordinates of the Wortmann FX 66H 159. I think I have this figured out now and hopefully this post will clear up some of the confusion about the various AV-36/361/362 airfoils.

    There is the original AV-36 airfoil used by Fauvel. There are 2 versions of the ordinates floating around. One is nothing more than the original set with one batch of ordinates (lower IIRC) offset by one station. This is obviously from someones mistake in transferring the ordinates to electronic format.

    This correct original AV-36/361 airfoil is "Fauvel original nose arcs".
    It has a best L/D of 72 at around .47 CL and according to JavaFoil it still works, maybe even better, with dirt on it.
    The maximum CL is around 1.7 at a pretty high alpha
    It has a nasty bump :oops: as the CL goes up.

    Smoothing the nose arc "Fauvel Smoothed nose" removes the nasty bump in the lift curve and ups the max L/D to 95 and raises the maximum CL to a little over 1.8. There is very little change in the moment or stall alpha.

    Letting JavaFoil smooth the ordinates ups the max L/D to about 105 and the maximum CL to about 1.9.

    Moving on to the Wortmann airfoil(s)
    The ordinates provided by Falconair for the AV-362 "Wortmann from Falconair" are different than the ordinates labeled as being obtained from the university.
    The Falconair version gives a max L/D of only 98 at a CL of around .87 which is little better than the smoothed AV-36 profile and at a much lower speed. It also has a maximum CL of only around 1.6. The drag rise as the speed lowers is not as "notchy" as the AV-36 profile but overall it doesn't seem like a very good option?

    That leaves the last set of ordinates for the Wortmann FX 66H 159 with the notation from the university. It is visibly different than the Falconair version and has a much better L/D of about 196 at a CL of around .96 - or an even lower airspeed than any of the above. It also has a much lower max CL of only about 1.3 at a much lower stall alpha. JavaFoil also says that the L/D goes below any of the above when dirty.

    The point of all this, for me, is that I see no reason to try to incorporate either version of the Wortmann airfoil, even though they were introduced to improve the performance of the AV-36/361. Unless there is real world evidence that the Wortmann airfoil actually increased the performance substantially I see no reason to do any more than smooth out the original flat bottom airfoil?

    A completely different airfoil might work, but it would no longer be an AV-36/361;)
     

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    Last edited: Nov 5, 2019
  3. Nov 12, 2019 at 4:42 PM #23

    Hot Wings

    Hot Wings

    Hot Wings

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    After watching another project here on HBA and the experience of the last couple of days learning just how much of Solidworks I don't know well enough I though this update is appropriate:
    DK progress.jpg .
    A Learned that the AV-36 plans/rights were available and thinking it was pretty close to what I was sketching - "Why not take a shortcut?"

    B Made the deal and thinking "Just 6 weeks or a couple of months to redo the plans in modern CAD. After all I've already done this with another set of flying wing plans. How hard can it be?"

    C The documentation arrives and I have had some time to look over what is there. Master plans are old copies and in poor shape. Get them digitized so I can work with them and think "This is going to be a little harder than the last project. Maybe 3 months?"

    D What have I got myself into?! Dimensions are missing or scattered about on different pages. Some of the metal parts are so complex no modern builder will ever be able to duplicate them in a home shop!
    The landing manners of the AV-36 are obviously quite poor. The various modifications tried don't seem to have been effective.
    Still need a steerable nose gear for a powered version. The various owner modified AV-36s with power do little more than prove that it is possible - not that it is practical.
    The Germans have permanently grounded all of the AV-36C due to inflight failures!! Why? What needs to be fixed?
    No one has actually built an AV-362 with the Wortmann airfoil and the airfoil program says it is not a good match for this plane. So any hope of a significant increase in Lift to Drag is pretty poor. That leaves only the cleaned up Fauvel airfoil.
    I could have probably designed a lookalike flying wing from scratch faster than this project is progressing :(:mad:o_O
    Adding power is going to add another layer of complexity and I'm still weeks from even being able to consider how. :eek:

    E Where I think I'm at right now.
    Got a set of original French plans. I don't read/speak French but the copies are in much better shape and have some information not in the English version.
    The AV-36C had a modification to the wing that was unique to the AV-36C and is not in the plans. Reverse engineering the plans version indicates the plans built version structurally is OK, but just barely.
    Adding a proper steerable landing gear, with good manners, is proving to be possible and practical - with little increase in parts count or weight.
    I'm getting comfortable with some new Solidworks skills.
    I've started the process of converting the Solidworks files to 2D paper prints. Finding that "D" size prints are not big enough for some parts that should be printed full size for templates. This is a minor problem.........I think?
    Thanks to another HBA member the last little problem for the first choice power system has been solved. It may not be the ultimate power solution but it should be practical and reliable - after a reasonable development program.

    I could still be on the D/K line to the left at the same altitude.:confused: At least I have a functional process in place....or so I think.
     
    Himat, cheapracer, mcrae0104 and 4 others like this.

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