Following are reports which pilots have posted on the IMAC bulletin board since 1999, which may be of interest to those with similar engines trying to determine which propeller to use and what rpm and noise levels to expect, or pilots building new planes who are deciding on a new engine. These are for 100cc to 160cc gas engines only at this time.
There will be variation in rpm for many, many reasons such as ambient air temperature, oil type, oil content, altitude, break in time, needle settings, baffles/engine cooling, mufflers/pipes, differences in tolerances from engine to engine and prop to prop and tach to tach, and more. This information won't tell you what rpm YOU will get on YOUR engine with YOUR prop the day YOU decide to check it, but the data is definitely very useful.
The information is grouped by engine type. These were posts to the IMAC bulletin board and they may have been edited. These are not endorsements by Troy Built Models. These are posted in no particular order.
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I have been running a 26-10 Menz-S on my new 3w-100 in a 35% Carden CAP. Rpm's were about 6200 out of the box, and for the first couple of flights. Haven't checked the rpm's lately, but will do so today. I have about 30 flights on it now. I was running regular gas with Bel Ray MC-1 oil up to about fight 20. (close to 5 gallons). At that time I switched over to Amsoil 100:1. Runs great, seems to like the Amsoil. I know the rpms are up a bit because the prop has a real "snarl" to it on straight and level. Excellent vertical, non-stop. Tried a Fuchs 3 blade, 25 x 12 prop yesterday. With the Menz 26-10 the dB on the ground, at 9 meters was 105. with the 3 blade it was 99. With the Fuchs the RPM was 5400. It sounded WAY to low, as if the motor was being loaded down too much, but it ran pretty good, and after a flight the cylinders were not too hot, so we deduced it wasn't overworking. The vertical was NOT unlimited and "petered out" , but certainly substantial for this years Advanced sequence. the dB reading on the Menz on straight an level, about 50' off the deck and 100 feet out was about 78 dB. With the Fuchs it went down to about 65. Bottom line, in my opinion, the 25 x 12 is too much prop for (this) motor at this time. I think a 25 x 10 would be a good combo. Maybe after another 25 flights when the motor has "come in" a bit more it will pull the 25 x 12 a bit better.
Running a TOC modified 100 on 89 octane and Homelite oil for break-in purposes. The engine has about 4 gallons through it now, call it 20 flights, and these are the RPM figures with Supersonic Mufflers: Mejzlik 28-10. . . 6550-6650 on the ground depending on the weather and a smooth idle down to 1000-1100 rpm. The dB level is UP though because the Supersonic Mufflers are LOUD. . 106 dB at 9 feet on the sides and 107 in front. The engine will rip the prop in the air, level flight, at half throttle!!! and pulls out of torque rolls at anything over 1/2 throttle. This is a Mejzlik 28-10!!! Almost as strong as the "old style" 120. The plane is a 38% Extra 260 that weighs 29-29.5 lbs. No dB levels on flyby's though, but they have to be up there. Kris
3w TOC100 I have turns a CONSISTENT 6750 rpm with a Mejzlik 28-10 and occasionally on a cool day sees the high side of 6800 rpm. Its still not broken in fully as far as I am concerned and I expect it to eventually see 6900-7000 rpm. Future plans for BOTH the BME and the 3w100 include installation of the 3w tuned pipe canister mufflers to abate noise and boost both engines by 2-300 rpm (I HOPE). Also, those of you experiencing difficulties with the Tillotson carbs on the 3w100's, you can swap the Walbro used on the BME and I THINK the Brison 6.4 directly across. I have found it to be smoother in the mid-range, with noticeably smoother transitions at slow throttle opening speeds, and less burbling overall. Kris
Well... though I never owned one of those standard 3W-100's that would turn a standard Mejzlik 28-10 at 6600 or so, a friend of mine had two, one of which would routinely turn 6700 to 6800 with that prop. There were quite a few disbelievers and loads of controversy about it on the list, but these engines were tached with multiple high accuracy tachs at different times and they would routinely turn up in that range with that prop. It's also true that most 3W-100's don't seem to turn like that, but those two stock models did. Ask Branwell about this... For contrast, we had put the same prop on a fairly strong Q100-XL of mine, which at the time could turn a Menz-S 26-10 at 6400. It struggled to hit 6100 with the 28-10 Mejzlik. Those were very strong 3W-100's and ran great with the DA ignitions that were installed on them. Ed
Ed, Kris, FWIW, my 3W100 turns a Mejzlik 26-10 at 6720. Regards, Alan
John, a friend of mine turned 6900 with Mejzlik 26-10, out of the box. Before he sold the engine it was seeing over 7300 with the same prop!!! The 3w100 definitely needs a 27-10 Mejzlik for optimum power usage. These figures are with Supersonic mufflers. Kris^
I think it was more like 6500 with the 28-10 Mejzlik ready to fly and 6550-6600 with the cowling off all warmed up. Not sure why extra rpm's with the cowl off. Will
I was getting 6400 with a Mejzlik 28-10 with about 5 gal. through it. After I sold it, Will said it was up to 6650. This from what I hear from other 3W owners is about right or maybe a tad on the high side. I would think a 27" prop would turn more rpm. SAM
Recently I posted some results John Blankenship and I had with our 3W150's, since I had some positive feedback with regards to the results we found, I would like to relate my experiences with the new Nickelsil lined 3W100. The airplane is a 33% Pirate 300L weighing 27 pounds dry with a three battery Nicad system (hence the extra weight). This plane was previously powered for about fifty flights or so with the old chrome lined 3W100. I can now say with conviction that there is no comparison between the two engines. In fact my TOC 3W80 has in my opinion, power comparable (albeit a bit less torque) to that of the chrome lined 3W100. This new engine is, however, in a totally different league and has really made this plane come alive. For the first time I feel like I have current "TOC" power in a 33% airplane. One of the distributors of this engine believes that the power is close to, if not the same as the old 3W120, and after a few hours with this engine, I would say he is not far off the mark. The engine now performs right out of the box as reliably as the Brison 6.4, one of the easiest running engines I have ever seen. To be truthful, I must say that I am not a fan of the old 3W100, but I believe that 3W has finally got it right with the new cylinder supplier. This engine has torque to spare. Believe me, I do not want to sound like a marketing guy, but I have owned quite a few of the twins in this class and have a skeptical eye, but this engine delivers on all fronts. Let me also say at this point that I am not sponsored. Anyway, after the first impressions given above, here are my results with four popular props one might consider for this engine. When these tests were done, the engine had almost 1/2 gallon thru it, with the factory carb settings of 1.5 Lo and 1.0 Hi. All rpm's listed are hot, post ten minute flight. It has been my experience that on most if not all my prop tests (on virtually all the engines I have owned of various manufacturers, both singles and twins), that once the engine is hot (i.e. post flight) it looses around 200 or so RPM from the warm up (after 30 sec or so idling) measurement. Due to this I believe it important for those that report rpm's on various engines to state whether the engine is cold (i.e. pre flight) or hot (i.e. post flight). Here are the results...
Altitude: 603 ft.
Menz 26-10S - 6600 RPM
Mejzlik 28-10 - 6400 RPM
Bolly 28-10 - 6150 RPM
Bolly 26-10 - 6900 RPM
Well in this test, on this day, the Bolly wins hands down. Upline and downline speeds are slower that the other two props, but the overall speed (up & down) with this prop are the most consistent and judged superior by those at the field. Due to the lower RPM this prop is by far the quietest. As always the Bolly seems to resist change while requiring more attention to rudder (big heavy gyroscope) The Menz 26-10S is honestly too small for this engine and I would not recommend anyone consider it. The same can be said for the Bolly 26-10. It is my belief this engine will live in the 28 inch prop range. The Mejzlik 28-10 while a great prop (and worthy of consideration) is much faster in all respects than the Bolly (the Menz was the fastest of the bunch), so if you want to go fairly fast with a big disk, this prop's for you (sounds like a beer commercial), for me, transiting the box at a consistent speed whether level up or down is paramount. The Mejzlik appears to accelerate on downlines, but it is tolerable, and competitive. This prop required the least attention to rudder of those tested. It should also be noted I had a Mejzlik 27-10 available to try, but after flying the 28-10 Mejzlik, I realized that this 27 inch prop would also be too small for this engine and as the sun was getting lower decided not to fly it. Anyway these are my initial findings based on one afternoon's flying. As a side bar (and I don't mean to get off on a rant here), it is my belief that these results are just starting points as everyone's plane is different, even if they are the same type by the same manufacturer (I could relate my experience with jetliners to prove this point), as is each individual's flying style. What works for one may be a paperweight for another, even while flying the exact same plane with the exact same engine. Having said this and beyond the pure entertainment value of this forum (this does beat reading Model Airplane News doesn't it?) I believe the more info we can share the more informed decision we can make before committing our hard earned $$$. These types of comparisons distress of the prop manufacturers I'm sure....but wait a minute if they really cared how much they made, why would they stop making props every year (by taking a long holiday I'm sure, darn those Europeans!!!) thus allowing the supply to dry up just when we need them the most. But I digress, and this forum is not Politically Incorrect (or is it???). Anyway just my opinion, I could be wrong. As I get more time on the engine I will report back, but at this point, the Bolly will be hard to beat.
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To everyone who has ever wished they knew what an engine will turn with a certain prop, I have just done back-to-back tests with 5 (FIVE!!!) different props on the BME 100. NO tuned pipes, Nitro, changed ignition timing from stock or Av-Gas Straight 89 octane pump regular unleaded with 50:1 Amsoil 2000 oil. The engine has approximately 10 hours total run time and has used a Mejzlik 26-10N exclusively since first started. But, being the experimenter that I am I decided to try all the 26-28 inch props that I have ever used on 100 and 80 CC engines just to see what would happen. The jetting was NOT optimized for each prop. I just returned from the field after 6-20 minute flights and decided to do this test JUST to see what happened. Anyone who has a "Thrust" software setup PLEASE feel free to email me back with projected thrust numbers. It would be interesting to see, I think. The engine was not allowed to "cool down" between tests, but one prop was unbolted and the next bolted right on, restarted, then tached 5 times at max rpm, kind of what would happen in the air, in less than 90 seconds. The rpm figures are the range the engine saw during the tests, and the higher of the numbers in the range was always the FIRST pull, giving credence to a slight cooling down while switching over and the subsequent slightly higher rpm figure for the first rpm reading. After the first pull ,the engine consistently pulled the SAME rpm on the next four runs, showing the consistency of power after the engine was hot. As I mentioned above NO optimization of mixture was done. here are the Numbers:
Mejzlik 26-10N (prop usually run).... 6800-6870 consistent 6800 after hot
Mejzlik 26-10 (second preference).... 6650-6750 consistent 6650 when hot
Fuchs 26-10 (VERY wide blade)...... 5900-6050 consistent 5900-5950 when hot
Men-S 28-8 (Going on a TOC100).... 5800-5900 consistent 5800 when hot
Mejzlik 24-10 Three Blade (QUIET!!).. 6400-6500 consistent 6400-6450 when hot
The BME 100 is supposed to turn a consistent 6400 rpm with the Menz-s 26-10, and judging from these figures that is in the ball park. BTW the idle is smooth (sounds like a bus idling) with little "shake". Given my past experience with the BME engine, I can honestly say these are normal figures for the three I have owned. Those wishing to compare the 3w80 to the BME 100 in power, please note I have owned and tested the 3w80 with the Fuchs and all three Mejzlik props and it was a consistent 250-300 rpm slower than the BME.. . Kris^
Its hard to say categorically that a motor will have a specific amount of power. This is due to its run in state, how well the user tuned it, the altitude, the humidity and a host of other factors. Saying all that, at sea level, with a temperature range in the mid 70s and 30% to 40 % humidity, you should expect the following from a BME-100 that is fully run in, i.e. has more then 20 gallons of fuel with petroleum oil. Branwell.
Mejzlik 26-10 6400 / 6500
Mejzlik 26-10N 6700 / 6900
Menz 26-10 U 6800 / 6900
Menz 26-10 S 6200 / 6400
I've been using a Mejzlik 24-12 3-blade on my BME100. It's in an Aeroworks 540T and seems to work well. I tached it along time ago, and it got readings between 5800 and 6100, and since has had more than 15 gallons thru it. I haven't made any readings lately, but it pulls really well. It's definitely quieter than using a 26-10 at 7000 (my opinion) Try it Don
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Dave Johnson, and a few of the people I have talked to at DA, SAY its SUPPOSED to be 5.3 , 5.75, 6, and 6.1 lbs. bare, making it lighter than a comparably sized 3w100 (Which they are NOT ashamed to admit they are targeting). They are also adamant that it WILL out-turn a standard (non-TOC) 3w100 with the same propellers. Horsepower as a number is not the issue, since in-flight dynamics constantly change the loads on the engine. Suffice to say, if the power is what they WANT to get out of it, look for the DA100 to turn 6900-7000 rpm or MORE with a 26-10 Mejzlik, about 6600-6700 (or more) with a 27-10 Mejzlik, and well over 6200 RPM with A 28-10. These are the ballpark power figures for the current run of "standard" 3w100's. Some make a bit more, some less. Anyone wanting to jump in and tell the list how THEIR 3w100 runs with which prop, please feel free to do so. My TOC 3w100 turns 6750-6800 with a Mejzlik 28-10 prop, BUT it has a DA ignition and the Walbro carb off a BME. . . . .and no pipes yet, just standard Supersonics. THEN there is the BME 100 to consider, but that is JUST a little chainsaw motor, right? 6800 with a 26-10N Mejzlik, 6600 with the 26-10, and a Menz 28-8 at 6000. Don't forget the Brison 6.4 or Fox 6.4 either. NO, I'm not biased, I would have GLADLY bought a DA-100 4-6 months ago when they were SUPPOSED to be coming out. I've found, in the past year, that the plane does not CARE what is turning the prop, as long as the prop gets TURNED. You could even put an A&H up front and it would fly pretty darned well. . . . .for a little while.
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With very high humidity and temps in the upper 80's, I tached the RCS at a minimum of 6500, flew it, noted the pull in verticals starting from different speeds down to a hover. Very strong performance in all of this. Next, switched to the Menz S 26-10. Tached this at 6200, flew it, still good performance, but noticeably less authority in any verticals that where acceleration was asked for. BTW, for reference, the elevation at this location is under 1000' ASL, probably around 600'. Next test - Squeak's (Tom Lowery) new 42% Weeks Solution bipe. Weight somewhere in the high 20's, maybe low 30's lbs. Also with a Q-100XL, but this one runs stronger with 6400 to 6450 on the Menz S 26-10 (same exact prop - we swapped). Vertical performance is very lacking on this prop, which cannot break a hover and lumbers when a slow vertical speed is used at entry. Switched to the RCS and it tached 6700. Vertical performance did improve, allowing TR's and an ability to break the hover, albeit without much authority. Other vertical performance was noticeably stronger. Hard to say exactly why the RCS outperformed the Menz, but I suspect that the fact that it is laminated maple leads to some advantages. First, the prop is noticeably more rigid than the Menz. The blade sections are milled thinner, but otherwise, from about 1/3 out from the hub to the tips look very much like the Menz. The rigidity and thinner section most likely make for more efficiency, hence higher revs and more thrust. Either way, it's a great prop. Ed
Ed, Kris, FWIW, my Q100 turns a Menz 26-10 at 6340. Regards, Alan
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3w TOC140 with the 3w tuned pipe mufflers and a Fuchs 27.5 x 13 three blade prop. Same amount of run time and oil type. 6050-6100 on the ground and 100-101 dB. The prop does NOT rip in the air and pulls a 38 lbs. 40% DR109 (Hangar One ARC) straight up at will and torque rolls are done below half throttle. In the air if ANYTHING else is flying around you cannot hear the engine except on a close flyby. SUPER quiet! Something to think about Noise-wise. Best Wishes to all Kris^
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Prop Tests with 3W150 Date: Tuesday, September 26, 2000 Elevation 603 ft, OAT 75deg F Humidity 47% Today John Blankenship and I tested a number of props with our 3W150's. John has the twin spark edition of the engine, and mine is the single spark. Both of our engines are new, not broken in and are currently set at least 1/2 of a turn richer on both the low and high end needles than other operators of these engines have told us they will end up at when broken in. My engine only has 2.3 hours total run time, John's approx. an hour more. The needles on my engine are set to a hi of 2.5 and the low 1.5, still very rich in all regimes, so it should gain more RPM as it breaks in and is leaned out. If I recall John's is set about the same. My plane is a 37% Pirate 300L, it weighs 38 pounds dry, John's is the new Fiber Classic 330L which weighs less than mine (although I am not sure exactly how much). Interestingly, both planes appeared to fly the same props with about the same relative performance, this is not to say that the planes are equal in performance only that each individual prop appeared to fly the respective plane in roughly the same manner. Having said that, the comments below are mine alone and relate only to my plane. There is however I believe a relation to both planes, at least with my eye watching John's plane and listening to his comments as he flew his plane. Also, his twin spark engine consistently registered 150 to 200 more RPM than mine with all the props. It is important to note that we have both been amazed with the low RPM torque of these engines, it seems their torque band is optimized in the 53-5900 RPM band. The engines run very smooth and even through out the throttle range. Even at the rich setting we are currently running the engines do not bog down even the slightest on uplines or multiple snaps on the uplines, they just keep pulling. Also throttle transition seems to be much improved over the previous versions of the 3W engine in this size range (maybe due to the Walbro carb). Mid range is great and transition from low idle to full power and back is quick, smooth and consistent. Idles in the 1200 to 1400 range are possible even with these new engines. I will write another note about our experiences baffling the cowls in the future. Finally, we both commented on how airspeed control is a breeze through out maneuvers with this engine, this may be due to the lower torque RPM band of the engine (and using prudent throttle control). One thing is for sure it makes the props better neighbors. Needless to say we can't wait to get these engines broken in and leaned out to see what they can really do! Here are the results (plus tip speeds and mach) all measured when the engine was hot after flying for approx. 6 to 7 min each. We made the assumption the props unload 8% in the air. And again add approx. 200 RPM to get the twin spark engine results.
Menz 32-10S 5550 (5995 air), 837 ft/s, 502 nm/h, .70 mach
Fuchs 32-12 (wide blade) 5300 (5724 air), 799ft/s, 479nm/h, .67mach
Mejzlik 32-10 5800 (6264air) 874ft/s, 525nm/h, .73mach
Bolly 32-12 6200 (6696air) 932ft/s, 559nm/h, .78mach
Fuchs 30-12 3 blade 5250 (5670) 791ft/s, 475nm/h, .66 mach
Overall the Menz has fairly comparable performance to the Mejzlik in all respects with the noticeable exception that the Mejzlik. breaks the airplane better. OK here are my impressions on each prop with my 37% Pirate 300L.... The best overall prop was the Fuchs three blade, good up and downline speed (but the worst downline braking of any of the props tested), least vibration and noise, and the least p factor of any of the props resulting in less rudder needed for maneuvers (an interesting outcome!). It did wrap the plane up tighter in snaps than any of the other props. Second best overall was almost a tie with the Mejzlik slightly edging out the Fuchs 2 blade, followed by the Menz and the Bolly. Best upline performance of all was the Fuchs 2 blade (and it is interesting as it was the second slowest of all the props measured in overall aircraft speed the Bolly being the slowest) Second in upline performance was the Fuchs three blade, followed by the Mejzlik, Menz and Bolly. The Bolly had the best downline braking followed closely be the Fuchs 2 blade with the Mejzlik being third, Menz forth, Fuchs 3 blade fifth. Overall consistent speed was the Bolly, but this prop does take some getting used to as all the speeds are very slow, in fact almost too slow. Overall aircraft speed from fastest to slowest was: Fuchs 3 blade, Mejzlik, Menz, Fuchs 2 blade and Bolly. Noise pretty much follows the mach speed, (Lowest to Highest noise) Fuchs three blade, Fuchs two blade, Mejzlik, Menz, Bolly (of course even though the Menz has a slower tip speed than the Mejzlik, it is a noticeably louder prop). Acoustics were interesting today as it was dead calm. Some of the props had more noise from all angles, yet others only made significant noise as the aircraft approached. The two Fuchs were the quietest and only made noticeable tip noise when passing abeam our ears. The two blade Fuchs had a different "report " than the three blade (more "sharp" if you will) but surprisingly not a whole lot louder, it would be interesting to do a decibel comparison. I will be anxious to try these props again as the engine breaks in so we can see how each prop really performs (upline snaps etc.)as we didn't get a chance to try as many maneuvers as we wanted too as the sun was going down, so we limited ourselves to up and down lines, loops, and horizontal/vertical snaps Also interesting to note that the composites seemed to work the engine more and the mid range seemed smoother because of it. Wally
Richard we tested most of the 150 sized props, the Fuchs 32-12 is hands down the quietest (comparable to the 3 blade props) followed by the Mejzlik 32-10. The Bolly 32012, Fuchs 32-10 and Menz 32-10 are all very noisy props, destined to turn many a head at the flying field Wally
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I just borrowed a AirModels 28x12 3 bladed prop from Desert Aircraft. I had been running the Fuchs 27.5x13 3 blade and the Menz 32x10. The prop available through Desert Aircraft (AirModels) is Awesome! It is very quiet and very powerful! It is made of solid carbonfiber so you don't have to worry about it throwing a blade. The downline speed are SLOWER than a Menz 32x10! I really don't think there is a better prop choice for the 40% planes/150cc engine combo's if your looking to run a 3 bladed prop. The prop is slightly heavy though, I don't remember the weight but I needed the extra weight up front. For those of you attending the Nats, I will be running this prop on my 40% edge 540. The Fuchs prop available through Cactus Aviation offered too much downline speed and was not as quiet as the AirModels one. I highly recommend contacting Desert Aircraft and get on the list for the next shipments of props! Bill Hempel
Bill, It's the 28 X 12 AM that it turns 6400 RPM. Just tried the 32 X 12 Menz S this past Sunday. I like the way it flies....mainly the braking. I didn't necessarily notice a lot more vertical...about the same I'd guess. It turns the Menz at 5500 RPM but the prop noise is still too much. If I go to a field where noise isn't an issue, I might fly it for fun. Ron A
Branwell, I tached my DA-150 Monday. The engine is brand new with only about two gallons through it. the temperature was about 104 and the humidity was high. The weather has been VERY hot here on the gulf coast. The engine showed 5760 on a Mejzlik 32-10. Fuel is Shell 92 octane and Lawnboy ashless at 50:1 for break-in. Being brand new this engine is very loose compared to other twins I have run. My other twins were not this loose until there was around 60 or 70 flights on them. I LIKE THIS ENGINE. Have a good one, Lloyd Sullivan
Wait 'til you get those 60-70 flights on it!! Mine is now turning a Menz 32x10 S at over 6200 rpm. -Doug
Hey all, Sometime ago, someone asked what the DA-150 was typically turning.. This weekend, we put a tach on my DA-150 with the 32x10 Menz S. 5500 rpm, on regular gas and 100-1 Amsoil. Nothing scientific for sure.. but it's at least a ballpark figure for reference. I don't think anyone could argue with the performance of my G-300 this weekend :-) -Doug
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Some time ago there was a discussion about this subject and I promised I would report my experience with the ZDZ 160 engine when flown. The plane weighs 27.7 lbs. I flew this plane last Sunday with the ZDZ 160 fitted, I have flown overpowered planes before but this one takes the biscuit, the aircraft was airborne within 10 feet and going vertical at full speed without any apparent need to take any time to accelerate first. The power/thrust to weight ratio is about 3.0 :1 + , Though no real notice of too much torque during transition from low to high throttle that I expected during level flight. Lots of right aileron needed for attempting to hover at something just above tickover setting. Completely effortless vertical climbing authority almost like gravity and inertia did not exist. I flew with a 30 X 12, the engine tached during test at about 6,300 with 32 X 10 Flytech & 6,000 32 X 10 Menz. Not noisy at all but a nice deep sound with the pipes.
Only made two flights due to broken exhaust flexible coupling, the engine performed very reliably but I had it running slightly rich, much easier starting than the ZDZ 80, vibration level higher than I would like, this was confirmed by comments from each of the three people it took to hold the plane down that it was like a very effective massage machine. This is possibly due to the high torque engine coupled to a lightweight airframe. Wish I could see a 3W 150 or DA 150 in real life to compare it with, or does anyone know what prop might reduce this torque induced vibration, for example a heavier carbon prop of smaller diameter ? John Phillips
Name - Luciano ( looks like a cross between a Sukhoi and a pattern plane )
Wing span - 106 inch
Length - 92 Inch
Wing Area - 1950 Sq. Inch
Weight - 27.7 lbs.
Engine fitted 160 cc ZDZ twin + two tuned pipes
Prop - 30 X 12 Flytech wooden
Fuel - 95 RON & Castrol synthetic @ 50:1
Ignition - Vlach
I promised I would let those interested know any further running information on the ZDZ 160. Last week I had replaced the Flytech 30 X 12 prop with a Menz. Still only about four gallons through this engine. Due to some tip damaged caused by someone's pet cat chewing it away and also to get more ground clearance, I cut down a Menz Standard 32 X 10 down to 30" so is now something like a wider than normal blade 30 X 10 Menz S. Due to my concerns about the vibration level, I gave the tips the same shape as the original and spent a lot of time in making sure it was balanced perfectly. The result was significantly less vibration at full throttle on this lightweight 28 Lb airframe but the low RPM shake was still there. On Amelung full length pipes it tached at a solid 6,400 RPM on the ground. In the air there was some burbling during pick up that I think is due to the carb bay getting pressurized or the ignition advance needs adjusting, I will fix this. Ambient was about 32 Centigrade and 85% ish high humidity. At full speed in the air during level flight the thing howled violently, sounds like the prop tips must be near or past Mach 1, it is a good job we don't have a noise sensitive site (This might be hard to believe by some but in fact the locals said they wanted more noise) I could also be that the pipe lengths are too short. I will be trying some three blader's when they arrive, should be soon. Regards John Phillips
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