Bearhawk Aircraft Bearhawk Tailwheels LLC Eric Newton's Builder Manuals Bearhawk Plans Bearhawk Store

Announcement

Collapse
No announcement yet.

VG's on the hor stabs

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • VG's on the hor stabs

    As we continue the flight testing of the Model 5, forward CG limit is one of the items yet to be settled. According to Bob - the limit is set when elevator control authority in the flare is inadequate.

    I have been told different things from builders about the results of putting VG's on the hor stabs. Comments across a wide range. From it was terrible and made the plane unstable. To they really helped get more elevator authority. I do remember a couple builders of the original BH (flat tail ribs) had very good luck rectifying a forward CG problem caused by too heavy a prop on the front of a 540. 3 blade metal props can be problematic if you fly with little in the back - according to those owners. They said VG's on the bottom of the hor stabs really helped.

    So please let me know what you saw placing VG's on the hor stabs. Best info would be from a Patrol or Model B with airfoil shaped ribs. Or even the Model A with the wood strips glued on the flat ribs to make them airfoil. I think a few are flying around now with those wood strips in place.

    If the VG's helped please describe their placement. And if you can quantify the difference - that would be good. Meaning a before and after with just the VG's on the hor stabs. Not placing VG's on the wings at the same time. The info would really help us as neither Bob or me know a lot about VG's. And it seems possible that the forward CG limit could be different with VG's installed. Easy to test and find out.

    Thanks to several of you we now understand where VG's on the wings are best placed. We intend to try the VG's on the wings and tail surfaces of the Model 5 after preliminary testing is done. Thanks in advance for your help. Mark

  • #2
    Mark,

    Contact Scott direct, he does not check the group often. Very good results with the VG activity. Took both the wing and tail installations to dial it in.

    Kevin

    Comment


    • Mark Goldberg
      Mark Goldberg commented
      Editing a comment
      If you could put me in contact with Scott - that would be helpful. I know I visited with him. But do not have contact info. Mark

  • #3
    Mark,
    Have you tried gap seals in the elevators? There are a couple of foam versions on the market. Cub Crafters sells one and I believe the other that I saw is marketed towards the Pitts market. I am not sure if they fit. You can also make your own out of fabric. Oratex trim tapes would make it pretty easy.

    Comment


    • Mark Goldberg
      Mark Goldberg commented
      Editing a comment
      On the original tail surfaces of the Model A the kits from the factory did benefit from a gap seal as the opening was wide enough there was a benefit. I do not think that is the case with the Model B production as the gap shrunk quite a bit. Mark

    • svyolo
      svyolo commented
      Editing a comment
      Wide masking tape or Gorilla tape makes a pretty cheap experiment. It only has to last a couple of hours. The sailplane crowd also sells some products that function both as gap seals, and "turbulators". Not as big an effect as VG's, but a similar idea with less drag.

  • #4
    If only someone had tuft-tested with and without gap seals...
    https://youtu.be/NB0kh3Z4OVM

    Comment

    Working...
    X