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  • Whee out Bearhawk’in around.

    Thought I’d start a thread so I have a place to drop pics of my everyday boring flights😉

    First pic isn’t so boring though, at least not to me. Recently I took my Grandpa up for a flight. He’s approaching 94 and is slowing down a fair but. Last week we had some great weather so we decided to go for a ride. He learned to fly in 1947 but loat his medical a long time ago. I blame him for my flying adddicition.

    045C3ECC-B464-4F2F-87BE-66C9BB9061C3.jpeg

    Today my dad and I did a quick trip to visit a friend. The air was smooth and cold, perfect. We need tighten up our baffles a bit as one cylinder kept getting hot but opening the cowl flaps a touch cooled it right off. The fairings my dad just finished make a real difference. It’s hard to quantify without real testing but gps speed was 138mph going and 142mph coming. That’s about a 5mph increase I think. Wind was reported as light and variable and the local wind turbines weren’t turning. I’m quite happy. 26771AB8-9088-4640-99C0-127FC40F7861.jpeg

    E582ADFF-694A-41AB-9AF1-D8B57BB53162.jpeg
    Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

  • #2
    Beautiful pics Jon. Hard to see how a cylinder would get hot with all that white stuff on the ground all around you.

    The 88" prop is longer than on any other Bearhawk flying as far as I know. I think the 84" on the 540 powered Bearhawks is the most common.

    From the little I know - the longer prop should give you better take off and climb, but hurt your cruise. Seems like a lot of prop for a 210 HP engine. Knowing you from your postings here on the forum, you studied up on all this. Tell us what you think about the engine/prop combo and the performance expectations and the reality. Mark

    Comment


    • Bcone1381
      Bcone1381 commented
      Editing a comment
      ....also, maybe what you learned, improvements you would do if you built another.

    • whee
      whee commented
      Editing a comment
      Brooks, I don't think "improvements" is how I would label it but I know what you are getting at. There is a few things I would do differently. I'm noting them and will eventually post in the 'what would you have done differently' thread.

  • #3
    Originally posted by Mark Goldberg View Post
    Beautiful pics Jon. Hard to see how a cylinder would get hot with all that white stuff on the ground all around you.

    The 88" prop is longer than on any other Bearhawk flying as far as I know. I think the 84" on the 540 powered Bearhawks is the most common.

    From the little I know - the longer prop should give you better take off and climb, but hurt your cruise. Seems like a lot of prop for a 210 HP engine. Knowing you from your postings here on the forum, you studied up on all this. Tell us what you think about the engine/prop combo and the performance expectations and the reality. Mark
    Thanks Mark. #3 is the cylinder that was getting hot and it is also the leanest. A bit richer mixture setting than the book calls for also cooled off the cylinder. We have a few known gaps in the baffles I need to close which I'm pretty sure will remove the need to crack open the cowl flaps. Or I could burn a bit more fuel.

    My understanding on prop length matches yours, longer prop for better takeoff and climb but it will slow you a bit in cruise. Most of the C180 pilots I talked to reported about a 5mph speed loss when going from an 82" C203 to an 88" C203. I'm sure the long length is costing me some speed.

    I'm loving this engine/prop combo. Takeoff performance is good, speed is good, and the economy is impressive. Yesterday while cruising at 62% power we were burning 8.5gph and seeing those ~140mph ground speeds. I'm still unsure of my actual airspeed as I think we may have developed a pitot system leak which I'll be investigating today.

    I expected this combo to perform well, pull hard on takeoff, but be noisy. I did not expect this engine to turn this prop to full rpm during a static run-up since the prop is setup for a 230hp (@2600rpm) O470R. However this engine will spin the prop to 2600rpm during a static run-up. On takeoff it turns up to 2800rpm within a couple seconds but that was expected. The noise is deafening, when standing near the airplane during a static run-up it literally hurts your ears and chest. All that noise is wasted power and unfriendly to neighbors. But the takeoff performance is great, 300ft is enough with my poor but improving skills. The prop also pulls really hard. The double puck ABI brakes barely hold during a full power run-up. Climb performance is great, it's no 540BH but an easy 1500fpm climb is great to me. I've yet been brave enough to do a full power stall. The deck angle gets scary steep, the ASI get's uncomfortably low, and the airplane is still climbing at 500fpm. At what point does a prop turn into a rotor?

    Prop clearance is also an issue. On 800 series tires we didn't have the minimum prop clearance. On 850s we have just over the minimums but is still isn't enough. The prop is way to close to the ground, is picking up rock chips and I think I could smack it on the ground during a botched wheel landing. We are switching to 29" Bushwheels but I think the better solution will be to trim the prop. I think 84" is likely a better fit for the engine and is the right length for this air-frame.

    Soon we will try out an 82" prop so we can see what length to cut our too. I'm almost certain 84" will be the best fit.
    Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

    Comment


    • #4
      Dec AOPA Pilot has a 1 page article about prop performance. Apparently when the prop tips go past .84mach, drag rises very quickly. They tested a C180 with a seaplane prop at max rpm for take off distance and time to climb to 1000'. Then retested at 2500 rpm, full throttle, and both take off and climb numbers improved. Unfortunately they never gave the numbers for prop length or max rpm but I thought this was rather eye opening.

      Comment


      • #5
        Originally posted by rodsmith View Post
        Dec AOPA Pilot has a 1 page article about prop performance. Apparently when the prop tips go past .84mach, drag rises very quickly. They tested a C180 with a seaplane prop at max rpm for take off distance and time to climb to 1000'. Then retested at 2500 rpm, full throttle, and both take off and climb numbers improved. Unfortunately they never gave the numbers for prop length or max rpm but I thought this was rather eye opening.
        This site has some great info: Prop speed calculator here: https://pponk.com/props/#1463774934977-1d7f57b4-6b2b and static pulls here https://pponk.com/props/#1463774935085-a6c14c04-3b8d

        The IO520 installed on C185s have a max rpm of 2850 but when an MT prop is installed the limit rpm to 2700 claiming the performance is improved. IDK if that is true or not.

        What I do know is that my airplane is outperforming the numbers provided to me by Maule and C170 pilots that have this same engine and same model of prop but in a shorter length. However, when I dial my prop back to 2600rpm after lifti off you can feel the airplane accelerate. I'm really looking forward to trying the shorter prop.
        Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

        Comment


        • #6
          You're spinning at Mach .96 on a standard day. At -6C you hit 1.0. You need a shorter prop for sure. Even the 84" is .91 on a standard day.
          I've always guessed the 185s with 520s and 86-88" would benefit from slowly rolling the prop back to 2700 or so on the takeoff roll(slide) before they even rotate. That way they get the hole shot, but don't lose most of their thrust on the outer half of the prop as they go.
          If money were no object I think that engine is a prime candidate for a 3 blade prop.
          Last edited by zkelley2; 11-15-2019, 03:57 PM.

          Comment


          • whee
            whee commented
            Editing a comment
            Quite a while back I called Flight Resource to talk props. Part of that conversation was when a 3-blade should be considered. The guy told me 230hp was about the minumum power you want if running a 3-blade. I asked about the Huskies, Scouts, etc and he said people think they look cool...

            But a C401 off a C180 would improve my CG so I’ve been wondering about seeing if I could fond one to try. A 3-blade is slower in cruise but pulls harder on takeoff and in the climb. Maybe not worse than my 88” 2-blade.
            Last edited by whee; 11-23-2019, 10:40 AM.

          • zkelley2
            zkelley2 commented
            Editing a comment
            There's a lot more to it than horsepower. There's a reason almost every rotax 912 has a 3 blade and it sure isn't because they are putting out 230+hp. The airfoil and chord of the blade matter a lot. Odd blade numbers have a smoother output and are better balanced as well. Length is not everything. You can make a 75" prop that puts out more thrust at a horsepower than a 80" and vise versa.

            Prop tip speeds and ground clearance are both a large consideration. .96 is too fast, so it would be beneficial to be shorter. If you lose thrust to the shorter blades, then you need another blade to keep putting power to the air.
            On the kind air 200s I used to fly we swapped all of the 3 blades to shorter 4 blades. Lost a few kts in cruise but we stopped picking up so many rocks off the gravel runways. It also accelerated faster, despite being shorter.
            Last edited by zkelley2; 11-17-2019, 07:27 PM.

        • #7
          A friend and I went for a ride yesterday.

          E0098C85-AD93-4369-9B00-0CC931CB25D1.jpeg

          CA67B0E9-5F8D-4F0C-A2B3-A7419BCCFAD8.jpeg

          6EFAEB55-1B4E-468B-AF78-B0BAC6D66636.jpeg
          Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

          Comment


          • rodsmith
            rodsmith commented
            Editing a comment
            Very nice, why we build Bearhawks.

        • #8
          Yesterday we borrowed a prop off a C180. Same model as our current prop but 82" long (6" shorter). Flew both props within a couple hours of each other, same OAT and baro. I fully recognize that our approach is unscientific but really this comparison was just to satisfy my own curiosity.

          The three things we looked at were IAS, climb rate at WOT/2600rpm/70mph, and climb rate at WOT/2800rpm/50mph. With the sorter prop we gained a solid 10mph IAS, lost ~200fpm of climb at 70mph and lost ~500fpm of climb at 50mph.

          The speed increase was awesome but the loss of thrust is too great. We might trim it down a little but for now we are sticking with the 88" prop. I need to get some bigger tires, I'll look like a poser but at least my prop won't be in the dirt anymore.
          Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

          Comment


          • svyolo
            svyolo commented
            Editing a comment
            I would say wow at both the 10 mph speed increase, and the 500 fpm loss of climb rate. I guess that explains why seaplanes are so loud.

        • #9
          We had a 172 that we put a big catto propeller on and then did a thrust test to compare the old aluminum and the new catto. The catto had about 120# more thrust. Made a big difference getting off the water.

          Comment

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