Prop tip q-tip winglets?

[lukibob]

I had a thought on propeller design. Use winglet like tips to reduce vortecies on a prop.

I will test this one tonight if there is no wind. I just got it out of the printer.

It is a 150 x 75mm size. I use it on my 80g Ghost Bipe 180 with a UH 10g motor and 250mah battery.

Any thoughts?
Any experience with this?

Here is a picture.

Matt

[HugePanic]

weight at the ends results in higher loads for the hub....

keep it away from you at the test run....

[MCarlton]

I think there's a big potential for an out of balance prop too.

Winglets on wings are usually aerofoil sectioned and are not abrupt 90 degree endplates, the idea being to generate and throw the tip vortices as far from the main wing as possible.

Endplates on flying wings work effectively as the wings are usually quite swept and swept wings can suffer from airflow flowing in a spanwise direction, the endplates can help with this (like wing fences do)

It's worth a shot, but I don't think you'll notice an improvement in performance, you have still got tip vortices being generated by the endplates as far as I can see.

Now, if you continued the endplates all the way round in a circle, so the prop had a thin "ring" around it, that might have some mileage.

[N74463]

Matt,

Hartzell makes full size propellors with a bent-over tip, sort of like a small winglet. They're called Q-tip props. Scroll down to the bottom of this page: http://www.hartzellprop.com/product_support/support_faqs.htm

Joe

[MCarlton]

Indeed, but as per winglets, this is a bend in one direction rather than a flat section end plate. I can see how that might work, as the 90 degree bend is a continuation of the blade, but somehow an end plate seems different to me.

I'm not an aerodynamicist, I just have "hunches" about how I think things might work, but they are often wrong :)

[vintage1]

I have a hunch that going to a larger blade at less RPM would gain you far more..

[lukibob]

I threw it on the plane just to see what it looked like rough. I still need to sand it smooth.

I think I changed too many things from the original design, I added chord to the blades, added 10mm to the diameter and the tip plates.

The old prop pulled 3 apms, this one pulls 4. It has a lot more inertia, spins longer after power cut. It does feel like more thrust though, have not measured it yet.

I'll keep this updated when I get more testing done.

It does look different though, not many people have one of these :)

[ghoti]

I would think that aerodynamic forces on the prop winglets would exceed those caused by the weight difference from the two end plates. Any asymmetry will show up as vibration but with this arrangement there are now two vibration sources: weight imbalance (easy correction with any prop balancer) and aerodynamic imbalance from geometry differences in the two end plates that will be greater in magnitude and probably impossible to correct. Bill

[mnowell129]

There are some studies that showed for tip plates to be effective, they have to be really huge. A ring doesn't do much either as it extends the tip plate size in the wrong direction. If you really want to increase the prop efficiency you need to put in in a duct with some sufficient depth. The problem with this is obviously structural and usually the weight and drag penalty of the shroud is more than the gain in prop efficiency.
Usually you only see shrouded props where noise reduction is a really important design criteria.

[eflightray]

I have vague memories from my control lines days where a single blade prop, (counter balanced), was the most efficient for the speed fliers.

It could be based on single blade could be a slightly bigger diameter than a twin for the same power input.

I remember flying a single bladed free flight rubber model, but that was usually because carving two identical prop blades was rather tricky, (and time consuming).

[Rodney]

The Canadian government also did some experimenting with single blade props back in the 40's/50's for light aircraft. The results were that single blade props were more efficient insofar as thrust per unit horsepower went but other design factors were to troublesome to continue the experiments.

[Julez]

A bigger wingspan is always more effective than winglets.
Winglets are only a solution when your wingspan is limited.

[Jurgen Heilig]

A bigger wingspan is always more effective than winglets.
Winglets are only a solution when your wingspan is limited.

That is correct, but still does not stop the quest for the "perfect prop tip shape". ;)

:) Jürgen

[Pinecone]

Actually the data I have seen shows that winglets perform the same as lengthening the span by the same amount.

BUT, with winglets, you can use a shorter span. This can be important to meet rules (15M sailplanes), or ground clearance (Q-tip props), or for ramp space (most airliners using winglets).

[MCarlton]

I thought the "marketing" for the Q-tip was to reduce vortices and "suck up" of debris rather than out and out efficiency?

I'm not claiming to be an expert, nor telling Hartzell that they are wrong, but sometimes manufacturers tend to "elaborate" on the benefits of a new idea, because they need a point of difference from other manufacturers to sell their goods.

Actually the data I have seen shows that winglets perform the same as lengthening the span by the same amount.

I'm sure there IS an effect, but I'm not convinced it is that linear. Otherwise I am pretty sure that we would see a great deal more (and bigger) winglets.

Example, why not have winglets on a carrier borne fighter aircraft rather than folding wings?

It could be based on single blade could be a slightly bigger diameter than a twin for the same power input.

Also, on a conventional prop, each blade is always working in the dirty air behind the other. Thus a 4 blade propeller does not produce 2x as much thrust as a 2 blader.

I think

[mnowell129]

Example, why not have winglets on a carrier borne fighter aircraft rather than folding wings?

Because they don't increase the wing area, they only reduce drag.

[MCarlton]

Thats my point, contary to;

Actually the data I have seen shows that winglets perform the same as lengthening the span by the same amount.

Hence, the Q-Tips of a prop only have a drag reducing function, and are not increasing thrust in the same way as higher pitch/diameter for the same RPM.

[mnowell129]

Thats my point, contary to;
Hence, the Q-Tips of a prop only have a drag reducing function, and are not increasing thrust in the same way as higher pitch/diameter for the same RPM.
Your quote really should read,

Actually the data I have seen shows that winglets perform the same, in terms of drag reduction, as lengthening the span by the same amount.

Which I think was the intent of the writer.

[lukibob]

I am printing two versions as I type. I have one with the tips, and one without. Same area, pitch and dimensions otherwise. I will try to conduct thrust measurements tonight with a scale.

I have flown the prop I printed earlier with the tips on it. It was very well balanced straight off the printer. It is larger in surface area than my original design and makes more thrust, I can hover at half throttle vs 3/4 with the smaller prop and not tips. It is also quieter than the smaller one.

[Troy]

lukibob indeed, you get to play with a RP 3D printer ;) I just got back from the Rapid Prototyping show. Keep up the good work. Experiment all you want. I had always wanted to try that... BTW, what machine is it?

[lukibob]

I get to use this printer at work. We just got the upgrade to use the stronger ABS. My prototype props are stronger than ever! I still have to sand them by hand for about 30min each then balance them.

Here is the printers page

http://www.dimensionprinting.com/3d-printers/printing-productspecs1200series.aspx

[ziomatrixacs]

I recently got a cap 580 flat out and it included a propeller with some unusual tips. Im not sure If I should sand them or not, the plane flies fine with them.

The last 4mm of the blades are bent 90 degrees back toward the airframe. Im not sure if this is a molding flaw but they are very close to be balanced. I feel its too close to be a coincidence so I havnt cut them yet...and its a cool looking prop, so id rather just use and APC. This is a 10x3.8 slow flyer prop by the way

If any one wants, I can try to do some test on it..

[lukibob]

ziomatrixacs,
I would be interested in seeing a picture if possible :)

[ziomatrixacs]

Here they be...:)
I took as many as I could and painted the tips silver so you can see. Its a great planes 10x3.8 sf. Its slightly thinner at the root and wider at the tip than my APC 10x4.7 sf. I dont own n 10x3.8 in APC to test it thought but the blades are similar.

+The APC 10" is the same length as the GP 10" even with the winglets on the GP 10, so the winglets on the propeller cant be a problem with the mold and some how got bent down that lenght. If I were to make the GP 10" flat, I would have a 10.5x3.8, not a 10x3.8.

+The tips are exactly the same size on both sides.

+The prop is actually balanced

- There is no mention of this in the manual, not even a "trim r up!"

-Never seen any other prop like this

So it may be on purpose, but not for efficiency reasons. They may have put it there to protect it or something or they may have put it there for us to trim until the prop is balanced (but it already is)

[Brandano]

I wonder if the purpose of those tips is to make th prop quieter. I know that on some full size helicopter the rotorblade tips are studied in order to reduce the noise footprint, see for example the EH101

[ziomatrixacs]

Noise reduction..that is possible because I am using a brushed motor and it sounds like a .30 size helicopter! Its really loud. My neighbors are used to me flying around with brushless motors, so when I took this thing out, they thought I had a flying lawn mower or something!

I am going flying today, if you guys want I can switch betwen the 10x4.7 APC and 10x3.8 GP and tell you the difference although they are different pitch props..