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

Announcement

Collapse
No announcement yet.

Feeling the need for speed...

Collapse
X
Collapse
 
  • Page of 2
  • Filter
  • Time
  • Show
Clear All
new posts
Previous 1 2 template Next
  • #1

    Feeling the need for speed...

    ​


    My mission is changing a bit so I'm on the hunt for some speed. Recognizing the type of airplane we fly and my lower horsepower, I'm not going to go crazy. 31s are coming off and being replaced by 850x10s, I'm looking for an 82" prop to replace my 88", the spill-plate wing tips have to go, need a spinner (doubt this will do anything). Any other ideas?

    My plane would do a solid 138mph TAS on 850x6 tires. That's at WOT (typically 21") and 2400rpm; 9gph. During flight testing we tried an 82" prop and it would do 147mph TAS at the same power setting. That computed because the guy we borrowed the prop from said to expect a 10mph speed difference between the 82" and the 88" prop. Now on 31s, it's 130mph TAS at the same power.

    It would be really cool if we could bump 150mph TAS at that same power setting while cruising at our typical 10,000ft.
    Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.
    Tags: None
  • #2
    I'd go even smaller on the tires. I took my bearhawk on 8.00x6 to a lot of places. If you're landing on things that look anything like airplanes land there, that's the biggest tire I'd use.
    • Likes 1

    Comment

    • #3
      Two reasons I don’t want to go smaller than 850x6:

      Prop clearance with my current propeller. It barely passes as legal on 850x6s and even with careful operations the prop get crewed up from sucking up debris.

      The wilderness runways we have here get rutted out and pretty rough when they dry out. I flew off of them on 8.00s in my Luscombe and than was lesson enough for me to know I don’t want abuse my BH like that. 8.50s work good and it what all the commercial guys run here.

      But, I already bought the 850x10 so that’s what I’ll be running for a while which will help keep my prop safe till I find a shorter one.
      Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

      Comment

      • rodsmith
        #3.1
        rodsmith commented
        10-02-2022, 08:43 AM
        Editing a comment
        Just curious about the 850x10s, are you using adapters on your wheels or did you get a set of 10" wheels?
      • whee
        #3.2
        whee commented
        10-02-2022, 04:56 PM
        Editing a comment
        Rod, I got a new set of wheels.
    • #4
      Not sure there is much else to do speed wise, other than the items you mentioned and having fairings installed everywhere. I made fairings for the top of the shock struts, doubt that will gain very much. One thought is after the other changes have someone check that your elevator position is neutral at cruise speed and adjust the incidence angle if necessary.
      • Likes 1

      Comment

      • #5
        Good thought on elevator position. Mine is level at my normal weights and needs some down elevator when the family is loaded up. Seems about as good as I can do.
        Last edited by whee; 10-03-2022, 09:29 PM.
        Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

        Comment

        • Nev
          #5.1
          Nev commented
          10-03-2022, 06:04 PM
          Editing a comment
          That's interesting. Mine needs more down elevator when carrying rear seat pax.
        • whee
          #5.2
          whee commented
          10-03-2022, 09:29 PM
          Editing a comment
          Brain cramp…thanks Nev. Down elevator for sure.
      • #6
        A spinner might reduce cooling drag?
        • Likes 1

        Comment

        • #7
          Wheel pants?
          Tail stinger / wheel Fairing

          Comment

          • whee
            #7.1
            whee commented
            10-03-2022, 09:31 PM
            Editing a comment
            That would be some big wheel pants!

            I’ve been thinking about a TW fairing. I think they look cool so might have to look for one.
        • #8
          8.50 wheel pants are pretty big. Not sure how much that will add.
          Attached Files

          Comment

          • #9
            Is it possible to add a negative, reflexive flap setting, a la Maule? Or, is the BH wing assembled in a way that doesn’t allow it?

            Comment

            • #10
              How about these, do they make much difference in speed?
              https://backcountrypilot.org/images/originalphotos/125/4102/24c298a18c0c824e334415f0.jpg

              Mark
              Scratch building Patrol #275
              Hood River, OR

              Comment

              • #11
                Originally posted by Light&Sweet View Post
                Is it possible to add a negative, reflexive flap setting, a la Maule? Or, is the BH wing assembled in a way that doesn’t allow it?
                I'd pondered that in the past, but after looking at both systems including the one on my Maule, the Bearhawk flaps aren't closed loop. They use cables to pull the flaps down and springs to pull them back up. If you adjusted the "up" position of the Bearhawk flap to roughly the reflexed position of the Maule, wind speed forces would push the flap down out of that position. Maule flaps are literally pulled up and down allowing the torque tube to be turned upward. I'll need to see if I can find a mechanical diagram so we can see how it works. It's been a while since I've seen it so my memory is a little fuzzy.
                Last edited by Chris In Milwaukee; 10-04-2022, 03:31 PM.
                Christopher Owens
                Bearhawk 4-Place Scratch Built, Plans 991
                Bearhawk Patrol Scratch Built, Plans P313
                Germantown, Wisconsin, USA
                • Likes 1

                Comment

                • #12
                  Guys, its a bush plane.
                  • Likes 2

                  Comment

                  • whee
                    #12.1
                    whee commented
                    10-05-2022, 03:12 PM
                    Editing a comment
                    I understand that perspective but I see it differently. Bob wasn't trying to design a "bush plane" when he came up with the BH. Neither was Cessna when they developed the C180. But they fit that mission quite well and with little effort. That doesn't mean they can't be set up to cruise a bit faster than average. The unofficial world's fastest C180 would cruise at just over 200mph but the owner had to work at it to get there. 150mph is achievable in my BH; small tires, smaller prop and some wing tips would get me there. I think I can get there on 25" tires...we will see.
                • #13
                  Look... there's guys that have those front air dams, towel-rack spoilers glued onto the hard tonneau covers over their 4.5' beds, and 50 profile tires on 18" wheels on their F-150's. I'm thinking 'dude... that's a TRUCK... go buy a purple metallic Hyundai and hang a cat-back and that other crap on it instead of the Ford.' The F-150 owner is thinking 'It's my DREAM... how cool is this?'

                  A seat for every butt... a butt for every seat.

                  But seriously... my thinking on the Patrol was that if I needed something faster and bigger, I'd rent it. Whee's thinking appears to be to squeeze out some additional efficiency from the BH to make it a more viable replacement for renting a 182 or - gasp - a Cirrus where time is a factor. I can see that. And those wheel pants? Serious Westland Lysander mojo there in the pic... and guessing that even at the size required for a good shape, there's a few mph to be had there (despite the potential PITA factor on hauling a payload of mud and gravel around inside the pant after ops on something stickier than you thought).

                  Some refs below...

                  The Drag of Airplane Wheels, Wheel Fairings, and Landing Gears: I - NASA Technical Reports Server (NTRS)
                  https://ntrs.nasa.gov/citations/19930091559
                  Tests were made in the 7- by 10-foot wind tunnel and in the 20-foot tunnel of the National Advisory Committee for Aeronautics to determine the drag of a number of airplane wheels, what fairings, and landing gears designed or selected for an airplane of 3,000 pounds gross weight. all tests were made on full-sized models; those in the 7- by 10-foot tunnel were made at air speeds up to 80 miles per hour and those in the 20-foot tunnel were made at air speeds up to 100 miles per hour. Although most of the landing-gear tests were made in conjunction with a fuselage and at 0° pitch angle, some of the tests were made in conjunction with the fuselage plus wings and a radical air-cooled engine and at pitch angles from -5° to 6° to obtain an indication of the general effect of these various items on landing-gear drag. All tests were made in the absence of propeller slipstream. The results of the investigation show that the lowest drag recorded for any landing gear tested was 13 pounds, at 100 miles per hour and 0° pitch, and that it might be possible to reduce this drag approximately C pounds by totally encasing the wheels of this gear in fairings. The highest landing-gear drag recorded was 98 pounds. Other points of interest brought and were: Fitting-plus-interference drag of ordinary types of landing gears averages about 44 percent of the drag due to these gears; low-pressure wheels and tires may be used with little or no increase in landing-gear drag; the proper wheel fairing may reduce the drag due to a landing gear more than any other refinement; fairing of all struts is of great importance; and landing gears having a single supporting strut have less drag than any other types of nonretracting gears. Also, the substitution of low-drag or retractable landing gears for conventional types on high-drag airplanes results in a negligible increase in high speed. Low-drag or retractable gears used in place of conventional gears on low-drag airplanes result in a substantial increase in high speed or saving in power at the same speed, the low-drag gear accomplishing a large percentage of the gain obtainable from the use of the retractable gear.


                  The Drag of Airplane Wheels, Wheel Fairings, and Landing Gears II: Nonretractable and Partly Retractable Landing Gears - NASA Technical Reports Server (NTRS)
                  https://ntrs.nasa.gov/citations/19930091591
                  This is the second paper giving the results obtained in the N. A. C. A. 20-foot wind tunnel on the drag due to landing gears. The first paper presented the results of tests made with full-scale models of wheels, wheel fairings, and landing gears intended for airplanes of approximately 8,000 pounds weight. The present report gives the results of tests of nonretractable and partly retractable landing gears intended for heavier low-wing monoplanes of the transport and bomber type. The tests were made on 1|2.8-scale models of gears with a capacity of 16,000 pounds total weight. The landing gears were mounted on a wing of a 5-foot chord, 15-foot span, and thickness of 20 percent of the chord. The effect of a radical-engine nacelle mounted in the leading edge of the wing on the drag of the landing gears was also investigated. Propeller tests were made in conjunction with several types of landing gears in order to ascertain the effect of the landing gears on the propeller characteristics. The tests indicated that in general, the presence of the engine nacelle did not appreciably affect the drag due to the landing gears. The retractable landing gears were at least one-half retracted into the wing or fairing before the drag became less than that due to the best nonretractable landing gears. Landing gears that were partly retracted into a nacelle near the maximum section or into the wing near the leading edge had a much higher drag than landing gears that were partly retracted farther aft on the wing. The drag due to the streamline wheels used on partly retracted landing gears was less than that for low-pressure wheels. Landing gears that were partly or fully retracted into streamline fairings below the wing had only slightly greater drag than those that were partly retracted in the wing or nacelle. The propulsive efficiency was reduced from 1 to 3 percent by the presence of landing gears tested in conjunction with the propeller.


                  Hoerner Fluid Dynamic Drag (should be PDF versions available online for a quick look)
                  Last edited by SpruceForest; 10-05-2022, 07:09 AM.
                  • Likes 3

                  Comment

                  • #14
                    These bad boys should save me a good 1/2 kt
                    (Wire cutter, profile boards and technique all courtesy of Graham Johnson.)

                    23869462-22CC-4B57-99F8-3AC5E135D987.jpg

                    8DC4E1C8-15BC-4AF9-AE5D-06609D6B83F5.jpg

                    219EB1C8-CE65-445C-A26C-F8AA68DA2A3A.jpg

                    DCDADBA4-9BF6-4D26-9420-65C27F2FD5A0.jpg

                    Last edited by Nev; 10-05-2022, 01:40 PM.
                    Nev Bailey
                    Christchurch, NZ

                    BearhawkBlog.com - Safety & Maintenance Notes
                    YouTube - Build and flying channel
                    Builders Log - We build planes
                    • Likes 4

                    Comment

                    • #15
                      Originally posted by Light&Sweet View Post
                      Is it possible to add a negative, reflexive flap setting, a la Maule? Or, is the BH wing assembled in a way that doesn’t allow it?
                      It is my understanding that my original 4 place was built with reflex capability. When I bought it, the reflex had been adjusted out. I don't know the history, but someone actually flew it and decided against it.
                      • Likes 2

                      Comment

                      Previous 1 2 template Next
                      Working...
                      X