Alltrikes

I'm not a technician but in my opinion there are a lot of different factors which determine what prop to use. The most effective is 2 blade prop. But, why the pilots (manufacturers) are using multi blades props? As Bill wrote one blade prop will be the best but they aren't balanced. Then 2 blades are the best?  Maybe yes, but we are restricted by their diameter. Bigger is better, because - very roughly - for every 10 cm bigger diameter = 10 kilos of additional static thrust. For example: I  tested a new SkyGlider 12,8meter wing with Verner VM-133MK engine. It was a manufacturer demo trike, demo engine 84HP/5500RPM with WarpDrive 2 blades with ground setting prop diameter of 192cm. It was a special trike with high mounted engine. With Verner's test pilot in the back seat we had stabilized climb of 7,5m/s at 75km/h speed. Alone I had stabilized climb of 11,5m/s (!!!).  My actual trike is ordinary trike- Low mounted engine (VM-133MK) because low center of gravity is better for flying and for moving on ground. So I must use a smaller prop - 170 cm. Two 170 cm prop blades don't have enough power, or I would have to change the gear reduction.  Then I used a slower rotation (by reduction gear) with a 3 bladed prop. I had to use another setting and now my engine is operating at 80HP/5000RPM. My stabilized climb is around 4,5m/s with passenger and about 7m/s alone.

The next factor we must to know is RPMs. If prop RPM is 3000/min or more, the blade tips exceed the speed of sound. It's more noisy and its dangerous to the prop's structure. Because a lot of small aviator engines are 2 stroke (Rotax, Hirth) and they operate at high RPM, we must to use a gear reduction to decelerate the prop. High RPM blades making an air vortex behind and high speed blades entering into this vortex will rapidly lose efficiency.  A bigger reduction gear can greatly reduce the prop's speed and we can then use multi blade props, because their blades won't enter the air vortex of the blade before.

Next factor is torque. Torque on 2 stroke engines depends on RPM.  More RPM = more HP = more torque. Look at a power diagram of 2 stroke engines to see for yourself... 4 stroke engines have better torque, and the design and profile of the prop is different. For better torque, some people are using a motorcycle or car engine (BMW,Honda, Yamaha, Subaru, Suzuki, Nissan...), but they are heavier. These are factors you should know when deciding what type of prop to use.

I think, these factors can be much more, which I don't know... I'm a pilot only, not technician :)

Jozinko, White Eagle,

  The engine is where I see we have room for great improvements. The Revo and Tanarg have very nice chassis designs (IMHO), there are a few great prop designs out there to choose from, we have some sweet wing choice now (Riva "S", Quest, Mako, etc),. Our engine choices are abysmal! Rotax has the market cornered and it's nice but OLD, OLD, school tech. They just gave us fuel injection,,, REALLY!? How long have the benefits of fuel injection been out there? I've had high hope for Wankel rotary engines for a long time. They just can't seem to crack the fuel efficiency problems. I still have hope though. Other rotary designs are on the horizon. Take a look at the RadMax by Regtech. Very cool design! Already demo-ed and doing well. The ICE engine is a dinosaur that won't die easily! Reliability, Torque and horse power need to be maintained while you reduce engine weight. It can be done! Thermal management can also be done without tons of complicated cooling loops (Yes Rotax I'm taking to you!). Ok, venting over...

wow scott  ul jozinko the information just blows my mind . i was talking with mike theakie discussing my engine changeover on my soaring trike. he was explaining to me why a rotax 447 puts out to much thrust for me at 40 hp  and why its not the same with a kawasaki 440  40 hp, it depends on the length of the compression stroke.  rotax 447 has a longer cylinder and piston compression per rpm hensss more thrust. so it looks like a balancing act in reliability.i can use the kawasaki 440 and will translate into much better climb rate we calculated the 340 and there just wasnt enough gain in thrust to translate into a significant climb rate. but the 440 should do the job  just cant use the rotax 447 id risk bending battons.iam not much of an engine guy ,i can do complexed michanics i just prefer to get mad and kick a dent into my car door.when looking at changing out a engine it seems prettty ambiguous on what to do , at some point you halve got to make a decision and hope you come up right.

For both ends of plastic tubes I made a metallic end (tubes). One is heading in carburater and next end is heading on ribs of cylinder. It draws mix of air - cold and hot. But the carb will be never icing. Its mine as cheaper solution as heating carbs are...

I really appreciate these Propeller repair articles Ken !!  Thanks for posting stuff like this you guys--  if we all do, this site can be so much more  (don't just lurk, post interesting things, get the ball rolling).

Putting the link in for your previous article too so people can more easily find both:

DIY Propeller repair

Link to Ken's other article  More Radical Prop Repair

FAA Article on Prop care and Inspection as well:

http://alltrikes.com/elgg/pages/view/4327/faa-safety-tip-propeller-basics#.UrM2Y41Q1YI

These are a great series Ken. Thank you!!  We need some triker opinions here !!  So basically, it looks like once any prop is pitched to the same bite (max RPM for that motor), the "Power" will be the same!?  That makes some sense BUT you certainly couldn't bolt a couple flat sticks on the hub and expect performance-  so there has to be some effect of good/optimized design-  no?

Why is it generally acknowledged that the Q-Tip prop on the Tanarg ES (quiet version) is less efficient than the noisier Arplast prop on the standard Tanarg?  If they were pitched to the same bite, then they should be the same based on the above excellent, hard to refute, data?

Here's some results from the Static Thrust Contest.  These were not standardized as Ken's results were however.

I can't find now the article I read that discussed the trickle down to GA of all the research going back into good old propeller technology due to UAV/Drone development.  I did find this article though- discussing advances in propellers, especially silent technologies.  AND they mention "energy scavenging" systems to power the UAVs (including, get THIS Infrared photovoltaic cells for gather electrical power for UAVs at NIGHT !!!!!)

UAVs / Drones lead to improvements in GA / Trike propeller market-- story HERE

Hey @Yarraft, @Cburg,  what do you think?