Which Prop?

[Morph]

OK so have we decided which is the best prop

[alanmack]

I do not profess to be a technical/engineering wizard on props and so I cannot offer to manage tests at this level. Consumers do, on a daily basis, form opinions on modes of transport by taking cars, planes, boats etc for a test drive. This is what I did, I took it for a test drive, and found that the difference is very noticeable. I have to tell you that the climb out is significantly better. To those that would like to feel the difference - contact me and you can take both props for a circuit and see for yourself. Unfortunately, I am not in a position to scientifically analyse the difference.

I genuinely have been in the p-prop corner in many a debate over the years and for this reason I sought the opinions I called for re test results and to see if maybe I just had a bad version of the p-prop and needed to get another? Mine has been repaired but does not have a single nick or scratch on it, if it did, I would have taken it for a service. This is evidenced by the fact that I have over the years done exactly this. I have never underhandedly sought to get accident damage repaired without the full CAA process having been followed and I have never resorted to whispers about any accident - in fact, it is quite the opposite - they are mostly legend!

What was a simple request for the sharing of opinions and facts has taken an unfortunate turn. I have had many phone calls suggesting that I just walk away from this debate and even more suggesting that I should take action against being slandered. I wish Pieter, his family and staff nothing but the best and am sad that he has made it difficult for me to remain a customer. I will however, retain fond memories. I stand by everything that I have said which was offered without any ulterior motive, confirm that I cannot offer any of the advanced technical/engineering testing suggested but do offer to put you in my shoes by offering you a "test flight" with both props so that you can get the look and feel of the significant difference that I have said exists between the two props. I will repeat the static tests if asked to do so and will do this to protect the solid reputations of those that witnessed the tests for the results as provided are accurate if not optimal.

Fly safe and may you enjoy the Chinese New Year tonight - I'll be off to the Chinese festival so why not join me and help pick out some sweet to balance the sour!

Nemo

[AndyG]

And they all lived happily ever after.

Not choosing any sides but hope that this gets sorted amicably. Life is too short and flying hours too few to let this simmer and fester.

Cheers to you all.

[Bugwar]

Why don`t we devise a test to determine the performance factor of a prop on a trike. The results should indicate the performance on a scale for different performance factors.

As with many other items used in all walks of life you make a decision based on the performance of said item under varied circumstances. The same tyre that performs excellent off road will perform terrible on the track and then there are the dual purpose that is average for both etc.

My feeling is that you will have the same when it comes to propellers. Take-off vs cruise speed and so on and so forth.

So if we take a trike and make the specifications known to all interested prop manufacturers and ask them to supply us with a good all-rounder prop, we can test these props scientifically against the pre-determined performance factors and plot it on the performance graph. This should give an unbiased test result that can be published (in Microflight Africa maybe;) and a bench mark to test other and future props.

As far as theory and the math is concerned, I may just be successful in convincing one of my colleagues (http://www.csir.co.za/dpss/aero_overview.html) to assist.
I will take it upon myself to organize the research effort should there be enough interest and input for such a test.

So if you think this may be a worthwhile exercise or have ideas as to what to test or how, give me a shout and we can get the ball on the roll...

[alanmack]

I will happily publish your results in the magazine. I'm sure that the aircraft manufacturers/agents would appreciate a well researched objective opinion on which prop? I would say that they will assist with a variety of aircraft also.

If they do not I'm sure that pilots will offer their aircraft and props for the test. I'm in if needed. In addition I would say that we should set a date for any field tests so that interested pilots can come and see the prop gurus in action.

Fly safe

[Captain Biggles]

Local is Lekker and Use the P-Prop on all my aircraft...Good service from Pieter and even Made a few propellors sorting one for the Skyranger...He made 5 or 6 for us to try out..till the happy medium was achieved...and we were not even charged for all those spare propellers that properly ended up as Braai wood...3 Cheers for Pieter...and P-Props...they work for us...and priced just right...and all Repairs done in a matter of days...Try sorting out your Arblast, Kiev, or any other Imported prop...if you have a problem...It takes a lifetime to sort out...and Lots of Money...We been down that road...soo local is going to be lekker for a long time...and anyway where else could you fit a Clock or Barometer to, once you retire , your wooden Propellor, to your Bar Wall...A Carbon Fibre prop would look so shit there anyway...

[Morph]

Sniff,

I would have had a P-Prop for BosBeFokker but on consultation with Pieter and he discovering I have the 912UL with the 2.27 ratio gearbox, he told me he prefers 2.43 and that was that. I unfortunately did not have the extra R10K needed to change the gearing so I opted to go Woodcomp instead, which was subsequently destroyed at 19 hours when I lost the front wheel and nosed over at Altona . I can account for how badly the Woodcomp prop was put together. So I have had to resort to a 2nd hand WARP I picked up for R2000 and I am very happy with it.

[Biggles]

I think this goes a long way to explain why the results came out the way they did...

On the one side:
N 2399 – originally designed 1988, built 2004, Aquilla airfoil, 4 x overhauls / services / repairs - made by hand – not CNC to an accuracy of 1mm or less .of which 2 of the overhauls where of such a serious nature that we recomended that the propeller should be scrapped. 75mm x 45mm x 0.5mm stainless steel wrapped over the leading edge.
On the other side:
A brand new Aeroprop, designed probably round 2000, built probably 2008 or later, Clark y or 99% similar airfoil, nil overhauls / services / repairs. Molds made by CNC probably to a tolerance of 0,3mm or less. A section of stainless??? Steel 290mm long x 25mm wide x 0.5mm thick FLUSH fitted to the leading edge. Tip vortex fins to combat spillage of airflow from the airfoilt to

a comment I picked up:

If you compare Michael Selig's polar of Clark Y to the Aquila's polar, the Clark Y polar shows a fraction less of the Aquila's lifting capabilities at low speed but it is far superior at higher speeds.

So aeros has superior aerofoil, vortex fins, more precision manufacture, smoother (triblade) and it weights less. It is more prone to destruct. And its impossible to hide repairs under a layer of paint.

I do like a wooden prop, but I would rather fly with a comp prop. I remember then I first flew with DNP (it was the first comp prop I flew with) and it was like the heavens opened up and angels started singing. It was just too smooth, I thought the pitch was set wrong or the air on Johannesburg was alot thinner than CT.

South africa must have a wind tunnel somewhere? a trike without wing, a thrust measurer and a digital prop rev counter should settle this. Then you could test from static to cruize thrust!!

[Biggles]

The lucky trike volunteer could also have thier pitch tuned to perfection.

[Boet]

Static thrust test. Mmmmmmm. You can make a prop that will give a moerofa lot "static thrust". The aerie fitted with this prop will run out of oompf somewhere around take-off, because the PITCH is too fine.. Case in point: Oom Piet and Geo, and Oom Trevor were testing a "new" prop on a Blunderturd. A static load test was done with BEEEG smiles. Louis was the test pilot on the ensuing crash test....... er...I mean flight test. The TB pulled away out of the blocs like a Champion olympic sprinter, but............. I think I`d rather leave this one to oom Pieter for explanation. You guys will not belief me anyway.

[Biggles]

Static thrust test. Mmmmmmm. You can make a prop that will give a moerofa lot "static thrust". The aerie fitted with this prop will run out of oompf somewhere around take-off, because the PITCH is too fine.. Case in point: Oom Piet and Geo, and Oom Trevor were testing a "new" prop on a Blunderturd. A static load test was done with BEEEG smiles. Louis was the test pilot on the ensuing crash test....... er...I mean flight test. The TB pulled away out of the blocs like a Champion olympic sprinter, but............. I think I`d rather leave this one to oom Pieter for explanation. You guys will not belief me anyway.

Dynamic thrust test... a wind tunnel will simulate true flying conditions. Starting at static you record the thrust developed in steps of airspeed through the full rev range.

So into 10Mph wind, thrust developed through the rev range. at 20Mph the full rev range. at 30 mph the full rev range, and so on, up to say 60mph.

Static thrust measurement has a few problems and is only representative of the first few seconds of the take-off run. After that the angle of attack of the prop will change as will the resulting thrust.

[pprop]

Dear Gentlemen,

I sincerely apologize, without any reserve or hidden feelings, in front of all present here in the forum, to Alanmack . I hope that you will accept this apology and that it will mend our relationship to what it used to be. I did not intend to assassinate your character, nor did I intend the letter to be a rant. The wiser route would probably have been to PM you for an explanation on the 2 questions.

I ask that the moderator of this thread remove ASAP any needless references to Alanmack as well and to strike it from the record so as to remove any fingers I have pointed in anger.

Now having said that, I have to state that I have been verbally diagnosed, by friends, family as well as “Rent A Crowd”, to have multiple personalities – (about 7) each personality ranging from serious pathological psychosis through being a mild mannered pervert right down to a scitzo combined with paranoid tendencies. I find it hard to control all 6 guys and one hell of a bitch – inside this head….. I would wager that most of the forum members instantaneously arrived at (more or less) the same conclusion after having glanced at my “Best picture ever taken”

Now back to the business of testing propellers.

I have read and re-read ALL the letters written by the members of the forum here.

I have to ignore some letters guys, but, please, please, please don’t feel bad.

Gents, please accept the fact that these tests will cost LOTS and LOTS of money, time and effort. The USA spent $2 million from 1927 to roughly 1934 to figure out exactly what you want to figure out now.

Understand that the factors that influence the design of a propeller from theoretical concept, to drawing board to CNC to the practical finished product has a HUGE quantity of seemingly endless variable influences, decisions and last minute recalculating certain aspects. Please believe me if I say that if I should start writing here it would probably take about 200 to 300 A4 folio pages. And that would be the shortest condensed version ever….

Understand that a WARP DRIVE airfoil is different to an ARPLAST. Understand that the ARPLAST AIRFOIL is different to the AEROPROP. Understand that AEROPROP is different to the WOODCOMP, BOLLIE, DUC, SENSENICH, GT, P PROP, BRENT THOMPSON, GEO KILLEY and HM propellers.

Understand that blade areas, trailing edges, leading edges, hub designs, materials used, weight and momentum, pitch settings, tip design i.e. swept tips, scimitar tips, square tips, elliptical tips, round tips, winglets up, winglets down, Rectangular blades etc. etc cause absolute chaotic havoc with computations and performance predictions.

Understand that ½ of 1 degree Celsius difference in temperature blows the whole shebang to hell and gone.

Understand that ½ a bar increase or decrease will influence the engine , propeller and wing performance to invalidate results.

Understand that each propeller manufacturer – to be totally open and fair – should have a honest representative present that would do the setting up of each propeller. We can’t just have ANY BODY in the flying fraternity handling all the aspects of the testing phase. It will have to be a committee of some kind with members that are capable of analyzing the results that will be obtained.

Understand that the experiment will have easy, somewhat easy, somewhat difficult and then somewhat expensive phases. This needs to be done to do justice to the various propellers that may be present. The greater the variety the more reliable the end result will be.

How can I explain this?

Imagine holding a round ball the size of an orange in your hands. Imagine the ball is made up of hundreds of little rubber bands.
Now it would be ridiculous and totally unacceptable if one should peel 2 rubber bands from the ball, stand back and proclaim to the world “These two rubber bands represent the ball on the table”

It should be obvious to you gentlemen that this is just not on!

Let’s investigate why?

What about the little red rubber band in the ball? What about the blue one? And the yellow one is thicker – and that orange one over there is longer – and wait this green rubber band is already showing signs of age by the tiny cracks? Shouldn’t we unwind all the rubber bands from this ball to be able to inspect, detect, test etc. etc. to get to an honest, overall, sane meaningful average result of the qualities of the myriads of rubber bands that make up the ball?

Do you agree?

I am busy compiling the very outside envelope of propeller testing. The list has +/- 18 requirements, so far. Each requirement has about another 10 or 15 divisions – I am sifting through the relevant factors. It’s taking a hell of a long time due to working in the evenings
Once I have compiled the rough outside parameters I shall ask the following people to adjust, add, subtract, suggest or change the endless aspects that will eventually arise. It is going to take at least 2 to 3 weeks to compile and edit the requirements to make the tests as practical and meaningful as ever can be done in SA

So far I wish that the following gentlemen partake in the analyzing aspect.
1) Tailspin – Gavin v/d Berg
2) Justin Schoeman
3) Kingfisher
4) John Waterson
5) Donald Hicks
6) Gunter Rostek
7) Tumbleweed
Paul de Kock
9) Biggles
10) Open - any Boffin or egghead from DE NEL or the CSIR is most welcome or any gent from this forum that will contribute positive practical aspects or thoughts

Partaking is voluntary. The reason I have asked these gentlemen is because of the sound remarks made, between the clutter (please don’t anybody take this as an insult) I am trying to sift jokes, snappy remarks, quips and funny faces from the little gold nuggets left in the pan. These guys mentioned above = little gold nuggets I found in the clutter.
If you guys think one should open a new thread called maybe “An introduction to the practical, sane testing of propellers on light aircraft with speeds not exceeding 135mph”
What do you guys think?

I don’t want to make the rough list available here – not yet, at least not until I have AT LEAST these 9 levelheaded guys look at and edit the requirements in a SANE manner.

OR

How many of you guys would like to see this rough list here?

I must ask you that comments must be analytical, practical, safe suggestions and within scientific accepted methods. Please keep the clutter as little as possible

If any of you guys feel that you do not want to partake – nobody here will hold it against you. However, through the sane suggestions some of you made I am very, very confident that a complete envelope of testing a propeller shall rise like the proverbial “Phoenix from the ashes”
Show your support by stating it here, in plain view of everybody to see, your YAY or NAY

Pieter de Necker

PS: The thing that everybody hates to do – pay!!
Once I have gathered a sane, intelligent, fair and honest team here I shall ask one of the gentlemen or one of the forum members to have a look see at the total predicted costs involving a full set of testing parameters agreed upon the proposed comittee. Maybe the members of this forum can find serious sponsors (with thick wallets) to share our enthusiasm in finding meaningful results.

[AndyG]

Pete,

You are a scholar and a gent. Nice to see the hatchet is buried and everyone moves forward.

Hope that the gents get involved as requested.

Cheers,

Andy

[Grumpy]

Admirable Pete.

[John Boucher]

I have the utmost respect for both Pieter & AlanMack and that is not about to change because of some tongue in cheek remarks made and do believe the air is now cleared.

I must add that Pieter was the one gentleman that without any qualms or queries sent me a loan prop (and I didn't even own a P-Prop at the time) to assist with a problem I had. His knowledge with regards to prop dynamics and manufacture is endless. We are surely privileged to have such expertise at our beck and call! He also never refrains from answering your question even though you might be using a different manufacturer's blades!

I urge that personal slander rant and rave be put to bed and regard it as water under the bridge! I do have a serious problem with product bashing which turns personal. Compare apples with apples albeit be it Granny Smith with Star King variety.

I am all for the testing and trust that the process shall be done in a orderly and controlled fashion and that we all may benefit from the results!