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LSaupe |
September 6, 2019, 11:15am |
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Flight Leader
Posts: 161
Time Online: 1 days 10 hours 40 minutes
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Anyone here running an F-33 on their Minimax? If so, how has it performed for you? Also, anyone operated both the 277 and F-33 for comparison? Performance, reliability, smoothness? |
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radfordc |
September 6, 2019, 1:20pm |
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Ace
Posts: 1,836
Time Online: 18 days 1 hours
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I don't have any personal experience with either engine. My friend had a factory built Belite ultralight with a F-33 engine. The engine was very under powered for that plane. Once he had to fly under some high voltage lines a half mile south of the runway because he couldn't climb over them. Twice the plane crashed....stalled and spun on climb out due to lack of enough power. Twenty five HP just wasn't enough. |
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nathan.bissonette |
September 6, 2019, 1:21pm |
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Flight Leader
Posts: 118
Time Online: 1 days 9 hours 13 minutes
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I found my 1100 in a barn and have been working on getting it ready to fly. It came with a Hirth F-33. Recreational Power okayed it this Winter.
The engine runs but apparently, I haven't got it dialed in right. At 1,000 rpm, it's literally shaking the airplane apart, but above 2,000 rpm, it runs smoothly. Haven't flown yet.
Radfordc's comment concerns me. I hope the engine has enough power. I'm not exactly lean. |
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radfordc |
September 6, 2019, 4:17pm |
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Ace
Posts: 1,836
Time Online: 18 days 1 hours
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ulbuilder |
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N349LE Ace
Posts: 302
Time Online: 8 days 20 hours 59 minutes
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I have an F33 on my MiniMax and just flew it for the first time last Saturday. My flight lasted only a few minutes because the CHT kept climbing but it did seem a little underpowered. Before the first flight the low RPM vibration managed to destroy the bracket supporting the ignition coils. I relocated the coils to the airframe. From 3000 RPM and up it runs pretty smooth, I keep it over 3000 unless I need it lower. Yesterday I ordered the 'maximal' cylinder head from Recreational Power to address the CHT issue. Maybe I'll have more info to report in a couple weeks. Here is a video of my flight: https://youtu.be/jvSQPFkWaEA |
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beragoobruce |
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Built an Eros - now I'm flying it! Ace
Posts: 1,067
Time Online: 19 days 10 hours 59 minutes
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Great video. I love the camera work: you've done well to pan the camera, zoom etc while flying at low level.
Your plane looks very good in the air. I thought the AOA looked rather high, but maybe that's just an illusion. What is the shroud thingy just forward of the strut pickup?
Bruce |
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Bob Daly |
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Ace
Posts: 888
Time Online: 45 days 22 hours 25 minutes
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The angle of attack was ok provided the ground was dropping away much faster. Not much reserve lift in that flight regime. Maybe ask the farmer to plow his rows parallel to the runway. Great video and flying. |
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aeronut |
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blue sky and tail winds to everyone Ace
Posts: 1,560
Time Online: 28 days 22 hours 31 minutes
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Great job posting your first flight. Is there a breaking in procedure put out by Hirth. Perhaps as you get a little time on the engine it will become run in better and produce a little more power. |
| never surrender; never give-up |
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radfordc |
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Ace
Posts: 1,836
Time Online: 18 days 1 hours
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Beautiful plane...but wow, was that a long takeoff roll and slow climb. You may find that on a warm summer day you won't be able to fly. |
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tdweide |
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Fledgling Member
Posts: 32
Time Online: 12 hours 44 minutes
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I have to say. F33 has never been on my list. I would rather breaking 103 than risk my life with under power. Super excited to see that flight tho! Great job! |
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nathan.bissonette |
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Flight Leader
Posts: 118
Time Online: 1 days 9 hours 13 minutes
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Wikipedia says the Rotax 277 weighs 65 pounds and produces 26 horsepower.
Wikipedia says the Hirth F33 weighs 45 pounds and produces 28 horsepower.
Not seeing much advantage for the extra weight. Is this more a matter of confidence in the Rotax brand name? |
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Bob Daly |
October 25, 2019, 10:49pm |
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Ace
Posts: 888
Time Online: 45 days 22 hours 25 minutes
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The engine runs but apparently, I haven't got it dialed in right. At 1,000 rpm, it's literally shaking the airplane apart, but above 2,000 rpm, it runs smoothly. Haven't flown yet.
Radfordc's comment concerns me. I hope the engine has enough power. I'm not exactly lean.
The idle rpm for the Rotax 277 is 2000. It's likely the same for the F33. Operation below that rpm is ill-advised. Setup your carb so the engine idles at 2000. Climb angle is determined by surplus thrust and weight. If we assume similar thrust for similar power, R277 v. F33, then it follows that for a given airplane, differences in climb performance are due only to weight. Ulbuilder's plane is certainly heavier than the Minimax R1100 which was designed with the 277 in mind. |
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nathan.bissonette |
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Flight Leader
Posts: 118
Time Online: 1 days 9 hours 13 minutes
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Thanks, Bob. I wonder if I have my tach set up correctly?
It's an electronic tach with a lead that wraps around one of the spark plug wires (similar to the Tiny Tach). The software gives me choices: 1P1R, 2P1R, etc., depending on the firing pattern of the engine.
I know the engine has two spark plugs in a single cylinder and they both fire every revolution. I know the engine has two magnetos, one for each spark plug wire. I assume the engine generates two sparks per revolution - one for the front plug and one for the back.
The tachometer's sensor wire wraps around one of the spark plug wires. So should I be measuring the sparks in that wire (one per revolution) or the sparks produced by the engine (2 per revolution)? Naturally, the tachometer manual doesn't say.
I selected 2P1R even though the sensor lead only wraps around one spark plug wire. Am I doing it correctly?
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Bob Daly |
October 26, 2019, 10:11pm |
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Ace
Posts: 888
Time Online: 45 days 22 hours 25 minutes
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Thanks, Bob. I wonder if I have my tach set up correctly?
It's an electronic tach with a lead that wraps around one of the spark plug wires (similar to the Tiny Tach). The software gives me choices: 1P1R, 2P1R, etc., depending on the firing pattern of the engine.
I know the engine has two spark plugs in a single cylinder and they both fire every revolution. I know the engine has two magnetos, one for each spark plug wire. I assume the engine generates two sparks per revolution - one for the front plug and one for the back.
The tachometer's sensor wire wraps around one of the spark plug wires. So should I be measuring the sparks in that wire (one per revolution) or the sparks produced by the engine (2 per revolution)? Naturally, the tachometer manual doesn't say.
I selected 2P1R even though the sensor lead only wraps around one spark plug wire. Am I doing it correctly?
You would only need to count the spark from one plug since they must fire together. One plug, firing once per rev, 1p1r. If it's wrong, I would think you'd see either double or half the expected reading. The idle setting, the low speed where the engine begins to run smooth, should be 2000 rpm. The maximum will be 6500. |
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ulbuilder |
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N349LE Ace
Posts: 302
Time Online: 8 days 20 hours 59 minutes
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Beautiful plane...but wow, was that a long takeoff roll and slow climb. You may find that on a warm summer day you won't be able to fly.
The takeoff roll was long, I think mostly because I did not pull on the stick to rotate. Just accelerated until she lifted up on her own. The climb was slow, i was keeping the airspeed between 50 and 60. Once I know the actual stall speed I'll see what the climb rate can be but the F33 will likely prove to be a little underpowered for this airplane. Knowing what I know today I would have purchased an F23. But since I already have the F33 I decided to see how it performs and then decide if swapping the engine is necessary or a luxury. I appreciate the congratulations from everyone. I don't want to hijack this thread with my first flight, just wanted to share my experience with the F33. Weather permitting I should have some useful performance numbers to share soon. |
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toliver66 |
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Ace
Posts: 208
Time Online: 3 days 7 hours 3 minutes
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Whats your total weight ready to fly Ace? |
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ulbuilder |
November 21, 2019, 3:06am |
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N349LE Ace
Posts: 302
Time Online: 8 days 20 hours 59 minutes
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Ready to fly with me and gas is about 590lbs. The Hirth F33 has a two blade UltraProp II at 60" with 8 degree pitch blocks. Static RPM is 5700, in flight 5900-6000 Climb rate is 280-320fpm, calculated from GPS. Stall is 31mph, without flaps. Full throttle level flight is around 55mph At 5400 RPM level flight is around 50mph Seems to climb best around 40-45mph. The mph figures above are calibrated airspeed Some other notes on the F-33 - My engine is mounted inverted
- I use BlueMax oil at 80:1 with ethanol free 91 octane mogas
- The stock cylinder head run too hot, had to replace it with the 'maximal' head that cools considerably better.
- Under 3000 RPM this thing shakes bad, imagine a bad vibration, double it and you might be close. That said above 3000 RPM it runs really smooth. To avoid the vibration I only go lower than 3000 if needed. Staying above 3000 might be difficult on pavement without brakes, on grass I can idle at 3000 without moving.
- The engine came with the dual CDI coils mounted on a bracket behind the cylinder. The vibrations caused multiple cracks in this bracket allowing the coils to flop around and rip wires in half. I moved the coils to the airframe, this seems to be a common suggestion with this engine.
- I've seen a few people who had the boot connecting the carb to engine is rip, likely because if the vibration. I've not had this issue but checking it is part of every preflight.
After addressing the issues noted above and getting the carb jetted right she starts easy, runs well and so far has been reliable. The engine has a total of 10.8 hours, 5.3 in the air. |
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Bob Daly |
November 22, 2019, 6:17pm |
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Ace
Posts: 888
Time Online: 45 days 22 hours 25 minutes
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Ready to fly with me and gas is about 590lbs. The Hirth F33 has a two blade UltraProp II at 60" with 8 degree pitch blocks. Static RPM is 5700, in flight 5900-6000 Climb rate is 280-320fpm, calculated from GPS. Stall is 31mph, without flaps. Full throttle level flight is around 55mph At 5400 RPM level flight is around 50mph Seems to climb best around 40-45mph.
Very interesting. So your climb angle is about 0.08 radians or 4.5°. What is your drive reduction ratio? 2.5? With a drive reduction of 2.5 your max thrust should be about 158 lbs. I had calculated a drag for the Minimax at 42 mph of about 102 lbs so the surplus thrust would be 56 lbs and the climb angle should be 56/590 or 0.095 radians or 5.4°. Maybe my drag estimate is a little low but certainly ballpark. You might fair your struts and wheels to improve your climb performance. I'd be interested to learn your observed best glide speed and angle. If we assume best glide is also 42 mph then the glide ratio would be about 102/590 or 0.17 radians or 9.9°. |
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ulbuilder |
November 23, 2019, 11:52pm |
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N349LE Ace
Posts: 302
Time Online: 8 days 20 hours 59 minutes
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Yes the belt drive is 2.5:1 This video has altitude, ground speed and slope displayed, one trip around the pattern: https://youtu.be/wYZt4NT_kNQI've been thinking of streamlining the struts, might be a good winter project. |
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toliver66 |
December 22, 2019, 10:03pm |
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Ace
Posts: 208
Time Online: 3 days 7 hours 3 minutes
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You have a beautiful Mini Max ulbuilder and I really enjoyed your build vlog and videos. But I was wondering if anyone is running an F-33 on their Minimax that is not 90 lbs over weight? And has been able to achieve these 1030F specifications taken from the Team MiniMax web site?
1030F Specifications Build time 300-350 hours Engine Hirth F-33, 28 HP Fuel Capacity 5 Gallons Flight controls 3-Axis Wingspan 25' Wing area 112.5 sq. ft. Length 16' Height 5' Empty weight 250 lbs. Gross weight 500 lbs. Design load factors +4.4 -1.8 G
1030F Performance Top speed 63 mph Cruise speed 55 mph Stall speed 26 mph Vne 90 mph Climb rate 650 fpm Take-off Roll 150 ft. Landing Roll 180 ft.
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Jimwing |
December 22, 2019, 11:44pm |
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Fledgling Member
Posts: 6
Time Online: 1 days 12 hours 48 minutes
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I’m curious, has anyone done a thrust comparison, Hirth versus Rotax single cylinders? I’ve seen many maxes fly with a Rotax 277 and they did pretty well. I do recall seeing a 277 achieve 200 pounds of thrust. Not too bad for one lunger. |
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mullacharjak |
December 23, 2019, 12:06pm |
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Ace
Posts: 281
Time Online: 3 days 21 hours 12 minutes
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I got this from somewhere.No mention of thrust though.
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textailwinds |
December 24, 2019, 3:29am |
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Fledgling Member
Posts: 43
Time Online: 1 days 3 hours 17 minutes
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Gyro Jeffro on the WEB is flying a himax now with the F33. You may message him for comparable comparison. |
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Keith103 |
December 29, 2019, 8:49pm |
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Ace
Posts: 632
Time Online: 13 days 6 hours 31 minutes
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Some other notes on the F-33 - My engine is mounted inverted
- I use BlueMax oil at 80:1 with ethanol free 91 octane mogas
- The stock cylinder head run too hot, had to replace it with the 'maximal' head that cools considerably better.
- Under 3000 RPM this thing shakes bad, imagine a bad vibration, double it and you might be close. That said above 3000 RPM it runs really smooth. To avoid the vibration I only go lower than 3000 if needed. Staying above 3000 might be difficult on pavement without brakes, on grass I can idle at 3000 without moving.
- The engine came with the dual CDI coils mounted on a bracket behind the cylinder. The vibrations caused multiple cracks in this bracket allowing the coils to flop around and rip wires in half. I moved the coils to the airframe, this seems to be a common suggestion with this engine.
- I've seen a few people who had the boot connecting the carb to engine is rip, likely because if the vibration. I've not had this issue but checking it is part of every preflight.
After addressing the issues noted above and getting the carb jetted right she starts easy, runs well and so far has been reliable. The engine has a total of 10.8 hours, 5.3 in the air.
I have a question on 2T oil to fuel mix ratio. On a general basis, what would be ideal fuel to oil mix ratio for 2 cycles ? I use 40 : 1 and feel I am running with too less of oil. Recommended per engine mfr for my engine is 20:1 for break-in of new engine and 32: 1 thereafter, which I feel is too much oil. |
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toliver66 |
December 30, 2019, 12:22am |
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Ace
Posts: 208
Time Online: 3 days 7 hours 3 minutes
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I always follow the manufacturer's recommended fuel oil mix ratio. I'm no engineer or 2-stroke engine expert but they are and they did all the testing and r&d on the engine they designed and built. So they should know what Oil mix is best for their engine. You could also void you warranty by not following the recommended fuel/oil mix. |
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Keith103 |
December 30, 2019, 1:00am |
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Ace
Posts: 632
Time Online: 13 days 6 hours 31 minutes
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toliver66 |
December 30, 2019, 5:25am |
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Ace
Posts: 208
Time Online: 3 days 7 hours 3 minutes
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Very interesting read indeed, thanks. I was referring to the newer engines like the Hirth F-33 with its Nikasil coated cylinder. Don't want to mess around with that. With an older engine and the newer synthetic lubricants, who knows. You could certainly get away with running less synthetic lube than oil but I would still rather someone else do the r&d. |
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