Which Prop?

[alanmack]

So as to focus on the props I've left names and places out of the report below. Has anyone else done a thrust test on a variety of props?

Ok, I'm fishing for more test results for a story!

I recently had to eat my words ( fortunately it was not my hat) and so did a few other seasoned pilots with many '000's of flying hours. Folklore included I have always believed that a wooden prop makes slightly more noise but outperforms others re thrust.

Using a calibrated hang scale, the same trike same day, same pilot etc with the only variable being a change in prop. Engine 582 with tests witnessed by trike pilots with some 35,000 hours who maintained that the Aero Prop would take the day - Pilots with about the same number of hours stayed at the club braai as they felt that the P - Prop needed no help.

RESULTS
Least Thrust - de Necker P-Prop 89 kgs
Other - three blade 120 kgs
Most Thrust - Aero Prop 126 kgs

The inflight test between the de Necker and the Aero prop was an absolutely awesome improvement in lift with the Aero Prop on vs the P -Prop.

Is this a bad P-Prop and a good Aero Prop or is this the new rule of thumb?

I for one have been a staunch supporter of the de Necker P-Prop but I sure had to eat my words!

Fly safe and Merry Christmas
Nemo

[Cloud Warrior]

I fitted a three bladed Bolly prop to my Aquilla a couple of months ago. I have always flown with a P-Prop before that. My perception is that the Bolly produces more thrust and is more "balanced / smoother".

My main concern has always been what effect the weight of a P-Prop has on your gearbox and engine on start up. I wonder if anybody has done a study showing relation between crankshaft and other mechanical failures and type of prop you are swinging?

So my P-Prop has gone off to a better place - she will grace the front end of a Cubby over here some time in the near future.

[Big-D]

Interesting Alan Mack - Thank you for sharing

[justin.schoeman]

Static thrust measures nothing except initial acceleration.

Within limits, for the same diameter prop, more blades = less pitch = better take off = slower cruise, burning more fuel.

The same trade-off can be acheived by using a longer prop (i.e. more lenght, instead of more blades).

If you ask Oom Piet for a take-off prop, I am sure he could make you a longer, finer pitched prop to match the performance of the 3 bladers (if you have enough clearance to swing a longer P prop, that is).

[alanmack]

I'm sure that someone will offer me a home for my P-Prop but I now am the owner of an Aero prop and the P-Prop is in its cover waiting for someone to make me an offer I cannot refuse! I already have a wooden prop with a clock in it.

I certainly enjoyed the lively debate of the "wizards" about the pro's and the con's of the P-Prop vs the rest. There were two schools of thought including a debate on the validity of the static test.

What sold me was the sheer inflight difference - greater climb rate on take off and greater airspeed ( which I only experienced after buying the Aero Prop on the strength of the static test results). Anyone with a serious interest in this matter is invited ( by arrangement) to fly the trike with both props at Petit.

PS If you want to see the P Prop it is proudly featured on the cover of the Xmas edition of Microflight Africa. It was in fact this photo shoot that got the ball rolling on the debate about the thrust that a P Prop generates. Actually I cropped the picture to focus on the Xmas theme so you do not actually see the prop. After the photo shoot a "wizard" took my trike for a "flip" and suggested that it would perform better with an Aero Prop. The rest is now history!

Merry Christmas

[Ranger]

Very interesting post .Who are the agents for the Aero prop? Anybody got any photos of this prop?

[alanmack]

I'm not sure who supplies them - I bought mine through Hans Schouten / Mervyn Reynolds ( Sky Riders) - it is a hollow carbon fibre prop that has the turned over tips.

I did an internet search:
This propeller is offered on Apollo trikes. After extensive testing Apollo North America, Inc. has found the Aero prop to be better than all other props Apollo tested on 912, Suzuki 4-cylinder conversion, Suzuki 3-cylinder conversion, Rotax 582 and Rotax 503 engines. Apollo welcomes you to prove them wrong. The anti-vortex tips help reduce noise and give it its cool look. Black or black with white tips (on some models) and riveted solid stainless steel leading edge protection (not tape).

see: http://skyboundlsa.com/aero_prop.htm

Fly safe

[Cloud Warrior]

If I remember correctly they are produced by a fairly small company in the Ukraine. When I first bought my Aquilla in 2004, it was fitted with an Aero(s?) prop. Unfortunately two of the blades were badly dinged which I did not pick up on until after the money changed hands - the previous owner only took off the prop cover of the blade that was still whole when he showed me the trike. So leer 'n mens........maar die wiel is rond en hy draai.........

There was a 6 month wait for replacement blades so I decided to switch to the P-Prop. It cost only a little bit more than what the two replacement blades would have cost and was ready within a couple of weeks. The Aero prop blades are easily damaged and once they are you might as well toss them. Very hard to fix if at all with that "sexy" little winglet at the end and the way they are constructed. I don't know if the delivery times have improved since then either. The P-Prop could be easily repaired (unless the damage was really bad) and the back up is local.

So for me the thrust issue comes second.

Service backup was the main reason I gave up on my P-Prop when I moved here. There are a few guys over here and in NZ that can repair wooden props but they are few and far between. So I went the Bolly route as they have excellent blade protection on their props and their back up is superb.

The other reason for letting go of the P-Prop was http://www.sportplanedesign.com/prop_in ... atters.php - something to think about?

[Kingfisher]

Excuse my ignorance , but what is the relation between static thrust and flying thrust ?
If you read the post of Oupa G building the Safari , when he fitted the new coarser P-prop, says that it cavitates up to about 15 mph but gives him the top-end speed he requires on the plane. My logic tells me if he does a "static thrust" test on that specific prop the reading would be on the low side.
The payoff would be less climb rate with added top end speed or more climb rate with less top speed.
The only thing that would really make a difference is if the prop has a type of pitch change to give it a wider effective operating range.
Help me out here, I am now disconfuzzled ......

[ZS-NEL]

Alan, Why don't you put that P-prop in the red bag and come and drop it down my chimney!

[Rudix]

I agree the Aero prop is very efficient but.....

I have 2 of them, both no longer in use because the blades split/de-laminated. Both props did this in exactly the same way, splitting first on the trailing edge and then on the leading edge. Neither prop ever had a strike or any other damage before the split. I looked at using epoxy to rejoin but the result was not good...

Maybe I was just unlucky ?

I then started using NC and Warp drive props, the NC is more efficient and the Warp is stronger, take your pick

Fly safe,
Rudi

[German]

Daar's net een prop en dis n P PROP

[Boet]

Ek stem. 'You can always trust a tree". Nog nooit gehoor van n P-prop wat n blade gegooi het of op sy LE of TE oopgebars het nie..........

[Tailspin]

HI Guys

Just my $2Zim worth.

Was the pitch of the 3blader set to the same as the P-Prop
What was the Lengh of the composite prop in relation to the P-Prop
What was the width of the Composite prop in relation to the P-Prop (were they the same width)
How much more Flexible was the Composite prop compared to the wood Prop

If all the numbers were exaclty identical then you are working with two completely different props - never mind if they were different pitches, Sizes etc.
There are so many factors that could cause a prop work differrently it is just not funny.
I will take your word for it that you did get better performance etc with the comp prop but there are way too many factors that need to be taken into account when doing tests like this. Each prop has it good points and its bad points. It is definately not an exact science.

But NOTHING looks as good as a Wood Prop

[Biggles]

Just to put my 2c in. I have the aero prop and I find it very smooth and efficient. No comparision though but I average about 12l per hour and i tend to fly with the wing in abit (I realise the wing has a bit input into this). As far as the delaminating goes... you may recall a few weeks ago I posted about fixing a delaminating "winglet". It glued with no issues. I have taken a few stone hits on the prop but i find the steel leading edge takes alot of the stone chips and any delamination can be sorted out as it starts.

Static thrust will differ from thrust developed while flying. This will depend on the pitch set of the prop. AFAIK fixed pitch props have a pitch that changes down the lenght of the blade to get optimum thrust through the full speed range so by setting it to cavitate low down it won't be optimum at cruize?

I have wanted to play with the pitch on my blade because I think its set slightly too coarse for thick creamy coastal air (set up for Highveld) . At climb, if I floor it, it just touches onto the orange (5700rpm, I think).