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

Announcement

Collapse
No announcement yet.

Long wing Bearhawk

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

  • #16
    Very helpful food for thought - thanks.

    I was always expecting a maximum tolerable G-force reduction would be required with such a mod, to avoid putting excessive bending stress on the wing (or are you talking about distributed load per chance?).

    Comment


    • Chris In Milwaukee
      Chris In Milwaukee commented
      Editing a comment
      I came up with that with distributed load calcs, and then those loads become additive as you move inboard. But that also assumed a cantilevered wing, so the bending force may develop at a different rate with a strut-braced wing. But that far out, it may be negligible.

    • Battson
      Battson commented
      Editing a comment
      The load distribution is quite different in a strut braced wing, at least in some areas. Apparently it may not effect the outboard sections - but I am not an expert. At least at a macroscopic level, the analysis is quite easy.
      http://soaringcafe.com/wp-content/up...ilsafefa10.png
      In that regard, lengthening the wing only adds a small force to all the inboard sections, relative to their maximum design load. That is what leads to the small reduction in maximum G-force, assuming you want to maintain the original safety factors.
      Last edited by Battson; 02-22-2016, 08:25 PM.

  • #17
    Jonathon one way fwd would be to build yourself a new set of wings and make all the changes integral rather than a tack on. Also that would give you a chance to use a riblett airfoil and move the ailerons outboard the extra bay and increase the flap length the same amount which is all increasing the effective CL over a longer length of the wing span wise. There was some good info in Pazmanny's design book on it i.e. calculating the effect of longer flaps span wise on slower landing speed. It would only be an incremental increase but it's all working in the right direction so to speak.
    Once you had them completed and fitted you could sell the existing wings.
    Last edited by Peter Bishton; 02-22-2016, 11:30 PM.

    Comment


    • jaredyates
      jaredyates commented
      Editing a comment
      I like this plan. You should be able to knock it out this winter. Take some pictures for a Beartracks article please!

    • Battson
      Battson commented
      Editing a comment
      Hahaha - yes, of course, it's just that easy!

    • Peter Bishton
      Peter Bishton commented
      Editing a comment
      Guys I tried to write a comment today and saved it in the wrong place. I will try and get some numbers for you on the W8 work my dad did with the Riblett airfoil. Dad is in New Zealand at the Hastings fly in with John Corby his mare of Corby Starlet fame. From memory the Riblett airfoil to approximate similar characteristics to the modified 4309 section on the W8 was a GA35 (or 37) Ax12 with the x I am not sure of the value and the 12 may have been a 13. The upshot was several knots more speed at cruise and substantial improved slow speed. Peter

  • #18
    Photo of Riblett wings on W8 with Hoener wing tips.

    Comment


    • #19
      When I was looking a wingtip designs I thought I read somewhere that the Hoerner tip added 4-6" of effective wing length which is why I wanted to use that style. My thinking was to eventually make a fiberglass tip that extended the airfoil 12" then transitioned into the Hoerner tip. That would increase the effective span by 2.5-3 feet. The WingX increases the Cessna span by something like 4' and on some airplanes requires a aluminum and stainless steel reinforcing straps added to the main spar in the lift strut area. Someone should perform the calculations on the BH wing to determine if similar reinforcement would be required; that way I can add them before I close up my wings
      I'm a Tapatalk user so I can't see your "comment"

      Comment


      • kestrel
        kestrel commented
        Editing a comment
        Wing-x adds 3 feet.

    • #20
      Jon, if you are serious about making some longer Hoerner tips like that, please consider me as a potential "customer" for your work on the moulds.
      If you made some moulds, I would certainly be prepared to pay you a premium to lay up a second set of fibreglass tips.

      As I said before, I would go ahead and do it myself, except for NZ is so very far away from 95% of the Bearhawk world - the effort of making the moulds seems to be a waste of time, as they wouldn't be able to be shared with the community. I don't think its worth making moulds just for one plane. Plus I have never made a set of moulds before on that scale, I bet they would be expensive, and you would want to recoup some cost by selling a few extra sets of tips to others.

      I am sure such a product (extended fibreglass Hoerner wing tips) would be a great seller. In fact - maybe that's a market Mark G. or Bob B. should consider tapping into?

      Comment


      • #21
        My dad is set on making our own tips so I'd say the probability is pretty high that they will also add some span. I'll have a bunch of studying to do to figure out the right shape.

        It shouldn't be too difficult to make the molds. Back in the early days my dad used to make molds for kayaks. As long as we get the design right I'm sure he can make them.
        I'm a Tapatalk user so I can't see your "comment"

        Comment


        • #22
          I found the following information about the Isham Piper PA28 wingtips interesting. Their Hoerner tips add 2' 2.5" of span but don't decrease ground roll or stall speed.




          I'm a Tapatalk user so I can't see your "comment"

          Comment


          • #23
            ‚ÄčI would say there could be certification / POH related reasons why they don't claim higher performance.

            Comment


            • Chris In Milwaukee
              Chris In Milwaukee commented
              Editing a comment
              Wow, you have a Commander? Drooool. It's one of my favorite GA airplanes. I've never been in one, but I remember reading an article in P&P a number of years ago that a guy restored a 112 to beautiful condition. They certainly have managed to keep their value over the years, too.

            • JimParker256
              JimParker256 commented
              Editing a comment
              Not meaning to hijack the thread, but yeah, the Commander is very cool. Largest cabin interior among all 4-place GA aircraft (by far!), two doors for easy entry/exit, built like a tank, and trailing-link landing gear that turns every landing into a squeaker... And the ramp-appeal is second to none, though some V-tail Bonanza owners will argue that point.

              I'm selling it (contract pending) to fund the Patrol build, because the Patrol better suits my post-retirement flight mission statement. I'm having a lot of fun building, and can't wait to start flying it. My demo flight at OSH was absolutely amazing! Bob designed an awesome airplane, and Mark puts out a great kit.
              Last edited by JimParker256; 03-01-2016, 05:01 PM.

            • Battson
              Battson commented
              Editing a comment
              Thanks Jim - that's some very interesting information you provided!

          • #24
            By the by, I spoke to Bob about lengthening the Bearhawk wing. He was not keen on the idea, which is not surprising.

            He cited a number of factors which would need to be considered regarding the strength of the spars and a few other factors. He didn't think there was any "fat" in the design, any room to increase the design loads without reducing safety factor below the stated limits. He thought the wing would need extra cap strip material at the strut attach point, if I recall correctly.

            He notes the Patrol wing, which is longer, has a deeper profile and this considerably increases the 4th moment of area - which means the wing would be stiffer and stronger if the spars were exactly the same on both models. Of course that's not the case in reality, both wings are probably about the same strength.

            Comment


            • #25
              Battson, Didn't Bob reluctantly agree that 15" extensions probably wouldn't hurt anything? I thought you were perusing the idea of 15" long Hoerner tips.

              I'm a Tapatalk user so I can't see your "comment"

              Comment


              • #26
                Originally posted by whee View Post
                Battson, Didn't Bob reluctantly agree that 15" extensions probably wouldn't hurt anything? I thought you were perusing the idea of 15" long Hoerner tips.
                He agreed to a 15" full-chord lift generating wingtip, which he said was the longest he could approve at full chord. He said a Wittman W10 style wingtip would be acceptable with a longer span, because of their much shorter average chord length.

                He wasn't prepared to approve any extension of the wing structure itself.

                Comment


                • #27
                  Has anyone done a tailwind style wing tip on a Bearhawk. The wing tip makes a lot of difference in the performance of a tailwind.

                  Comment


                  • #28
                    Originally posted by tailwind View Post
                    Has anyone done a tailwind style wing tip on a Bearhawk. The wing tip makes a lot of difference in the performance of a tailwind.
                    Mark told me that Bob originally intended to use a Tailwing style wingtip on the Bearhawk, but it never happened for some reason.

                    Comment


                    • #29
                      I may have shared this before...someday I hope to factually discover the advantages of different wing tip desings...using a different and peculiar way. I plan to get the aircraft rigged so that it flies straight, then install one of the subjects to be test on one of the wing tips. Then flown in cruise flight, the wing tip with the lower drag will induce a measurable yaw force. We can test a Standard tip, Hoerner tip, Tailwind Tip, Round/Square, then the Mooney "Cut off" tip...which is best? Do they really make a difference? No question if the power was set differently that day, or if the atmosphere's vitals were measured accurately to determine density altitude. We get simple, raw, side by side comparisons, kind of like a drag race with one wing tip compared against the other.

                      I also sense the tailwind tip may be least draggy....kind of ugly/boxey/trapazoidie, but it looks like it minimizes tip losses to me.
                      Brooks Cone
                      Southeast Michigan
                      Patrol #303, Kit build

                      Comment

                      Working...
                      X