Prop Selection

[skippydiesel]

All laws are there to be challenged -

 

Tell me how Robin Austen's Sonerai VH-SRS, can have a high speed cruise of 170 knots, an every day economy cruise of 160 knots and a stall speed of under 40 knots, all in a little  2 seat aircraft, powered by a Rotax 912 ULS, that can easily fit into RAA standards ?

 

His Sonerai is 50 -60 knots faster than my aircraft, is limited by the same power potential & fuel consumption constraints as mine. Sure his airframe may be optimised for efficiency/speed, the Zephyr is non to draggy by everyday standards either,  though not in the Sonerai class , so all I would like is a miserly extra 10 knots. Where is the problem?

 

As yet, not one contributor to this conversation has provided any constructive advise, regarding CS propeller suppliers and their products  - after all I did open with the "Hope I will get some great factual criticism to the following:"

[M61A1]

8 minutes ago, skippydiesel said:

All laws are there to be challenged -

 

Tell me how Robin Austen's Sonerai VH-SRS, can have a high speed cruise of 170 knots, an every day economy cruise of 160 knots and a stall speed of under 40 knots, all in a little  2 seat aircraft, powered by a Rotax 912 ULS, that can easily fit into RAA standards ?

 

His Sonerai is 50 -60 knots faster than my aircraft, is limited by the same power potential & fuel consumption constraints as mine. Sure his airframe may be optimised for efficiency/speed, the Zephyr is non to draggy by everyday standards either,  though not in the Sonerai class , so all I would like is a miserly extra 10 knots. Where is the problem?

 

 

What that means is that the Zephyr must be aerodynamically dirtier than you think.

The laws of physics remain....Increase thrust or reduce drag.

For something with a broad range of speed like your Zephyr the CS prop is likely to give some good gains. At which end, and how much you won't know until you try.

[M61A1]

Skippy....What RPM do you get at WOT takeoff and what RPM do you get at WOT straight and level?

 

[skippydiesel]

12 hours ago, M61A1 said:

What that means is that the Zephyr must be aerodynamically dirtier than you think.

The laws of physics remain....Increase thrust or reduce drag.

For something with a broad range of speed like your Zephyr the CS prop is likely to give some good gains. At which end, and how much you won't know until you try.

"dirtier than you think" - how so? my POH (which is conservative in all other specifications) says my aircraft can cruise at 124 knots but clearly not with a ground adjustable prop set for TO advantage.

 

I accept the laws of physics - if I didn't I would expect Robin Austen type performance. My modest + 10 knots in cruise is a clear understanding of this.

 

I never actually asked for a rational on the purchase of a CS prop - I know it is an extravagance, with little cost/effect justification (as is owning a LSA for recreational purposes) - what I asked for was feed back on the CS props in the market place (performance gains/ ease of maintenance/TBO/manufacturers support/etc) - something that the respondents seem unable/unwilling to impart.

[kasper]

But you are not comparing apples to apples.  The soneri that is the speedster is limited to 300kg for people and fuel - it is a single seater in effect. And it gets down to the Raaus stall area with full span electric flaperons.  And it’s damnably clean in particular the engine cooling etc.  

mid you have bugger all drag increase with speed increase then your advantage of cs over fixed is limited and the relatively low wing load at the 600kg mtow with full span flaps Means it’s really nothing like your aircraft in terms of lift n drag.
 

You limit yourself to a low wing load and get full span flaperons then your sort of comparing apples and apples.

[skippydiesel]

1 hour ago, kasper said:

But you are not comparing apples to apples.  The soneri that is the speedster is limited to 300kg for people and fuel - it is a single seater in effect. And it gets down to the Raaus stall area with full span electric flaperons.  And it’s damnably clean in particular the engine cooling etc.  

mid you have bugger all drag increase with speed increase then your advantage of cs over fixed is limited and the relatively low wing load at the 600kg mtow with full span flaps Means it’s really nothing like your aircraft in terms of lift n drag.
 

You limit yourself to a low wing load and get full span flaperons then your sort of comparing apples and apples.

Hi Kasper - Robin Austen's Sonerai 2 VH-SGS is the world speed record holder I quote from http://worldrecordplane.com/ :

 

 "carries 2 X 90Kgs (200lbs) people, 2 tents & sleeping bags, air mattresses, doonas, pillows etc and all personal belongings on 1000+ Nm trips. With 103 litres (27 USG) usable fuel, SGS can remain airborne for over 14 hrs and could fly across the entire mainland USA at its widest part with only 1 fuel stop."

 

A tad more than 300 kg dont you think?

 

Oh! and I am not comparing my aircraft with SGS or with SRS, his latest Sonerai development (& quit a bit further from the original Sonerai plans see this Forum, AU/NZ General Discussion, VH-SGS Sonerai II) just  pointing out that considerable improvements in cruise speed are possible, subject to airframe limitations

 

[skippydiesel]

3 hours ago, M61A1 said:

Skippy....What RPM do you get at WOT takeoff and what RPM do you get at WOT straight and level?

 

 

Hi M61A1 - Never tried WOT in strait level - Waaay toooo scary seeing the RPM climb so quickly into the red. Take off, I get 5800 RPM  easy - never stay there for long , throttle back as soon as I get to 2000 ft. Static WOT is 5200 RPM @ my current prop settings.

 

See data attached:

 

Propeller Selection Info.docx

[skippydiesel]

For those who dont read other areas of this Forum: Robin Austens Sonera2 VH-SRS:

 

Broadly speaking the SERA 173 specs and differences from a standard Sonerai 2 are as follows (all solo)

• Max continuous cruise speed 173 Kts

• All day everyday cruise speed 165 Kts (24”/4800rpm)

• Economy cruise - 160 Kt at 15.2 L/hr 

• Aerobatic +6G -5G

• VNE 180Kts (testing included full range flutter testing up to and including 200Kts)

• 300Kg empty - 600KG MTOW – 300Kg payload 

• RV10 cockpit dimensions - comfortable for 6’5” pilot, 6’2” PAX (Sonerai volume +67%)

• Centreline flying from front seat

• High strength crash resistant zone around pilot (2.5X FAR23 requirements)

• Airframe structural strength = Sonerai +25%  

• Airframe efficiency = Sonerai +72%

• Stall speed slightly less than Sonerai II (minimum solo 39Kts)

• 1250 NM range at 160 Kts 

• 1700 NM range at 100 Kts 

• Also comfortable at 70 or 80 Kt “loitering” speed

• Constant speed propeller with latest Sensenich high speed blades

• 23” prop clearance for gravel strips

• Full span (30 degrees deployment) electric flaperons

• Horizontal Stabiliser - electric inflight adjustable

• Rotax 912 reliability and operating costs

[M61A1]

37 minutes ago, skippydiesel said:

 

Hi M61A1 - Never tried WOT in strait level - Waaay toooo scary seeing the RPM climb so quickly into the red. Take off, I get 5800 RPM  easy - never stay there for long , throttle back as soon as I get to 2000 ft. Static WOT is 5200 RPM @ my current prop settings.

 

See data attached:

 

Propeller Selection Info.docx 15.93 kB · 0 downloads

Then, I think that a CS prop is probably going to provide some benefit. 

The Rotax owner website recommends setting up for Max continuous (around 5500 RPM) at WOT straight and level.

If the Zephyr is a clean as you reckon, there may well be another 10 kts to be gained.

The only CS prop I have had a few hours behind is a 3 blade Airmaster in another slippery airframe. I think that it does a great deal for the aircraft. It gets full power on takeoff and climbout around 60 kts while knuckling down  with speeds over 130kts at times. It is also simple to operate and can be feathered in case of engine failure.

That is a bit subjective though, as in, If I had to spend $12k on one I might look to see what else I could do

[kasper]

1 hour ago, skippydiesel said:

Hi Kasper - Robin Austen's Sonerai 2 VH-SGS is the world speed record holder I quote from http://worldrecordplane.com/ :

 

 "carries 2 X 90Kgs (200lbs) people, 2 tents & sleeping bags, air mattresses, doonas, pillows etc and all personal belongings on 1000+ Nm trips. With 103 litres (27 USG) usable fuel, SGS can remain airborne for over 14 hrs and could fly across the entire mainland USA at its widest part with only 1 fuel stop."

 

A tad more than 300 kg dont you think?

 

Oh! and I am not comparing my aircraft with SGS or with SRS, his latest Sonerai development (& quit a bit further from the original Sonerai plans see this Forum, AU/NZ General Discussion, VH-SGS Sonerai II) just  pointing out that considerable improvements in cruise speed are possible, subject to airframe limitations

 

Your own post Several after mine shows it - stall speed around 40 is ONLY if flown solo ... therefore it’s only raaus possible if it were solo so much less than the 300kg possible load

 

[skippydiesel]

18 minutes ago, kasper said:

Your own post Several after mine shows it - stall speed around 40 is ONLY if flown solo ... therefore it’s only raaus possible if it were solo so much less than the 300kg possible load

 

So what are you saying - cause the stall speed may be at solo /minimal weight (not RAA 600 kg) the aircrafts performance is not truly gobsmacking ?????.

 

I am not  interested in trying for  SGS/SRS performance  - I would just like to maintain my existing TO/Climb, while having a bit more cruise (+10 knots would be nice/acceptable)

 

[skippydiesel]

1 hour ago, M61A1 said:

Then, I think that a CS prop is probably going to provide some benefit. 

The Rotax owner website recommends setting up for Max continuous (around 5500 RPM) at WOT straight and level.

If the Zephyr is a clean as you reckon, there may well be another 10 kts to be gained.

The only CS prop I have had a few hours behind is a 3 blade Airmaster in another slippery airframe. I think that it does a great deal for the aircraft. It gets full power on takeoff and climbout around 60 kts while knuckling down  with speeds over 130kts at times. It is also simple to operate and can be feathered in case of engine failure.

That is a bit subjective though, as in, If I had to spend $12k on one I might look to see what else I could do

 

MS1A1 - I understand all of what you have said my question are:

 

What reputable CS propeller suppliers are there out there

What are the relative merits of the above

 

On your comment "WOT 5500 RPM" - if I were to set my existing ground adjustable prop for this, I have no doubt that my high speed cruise would be in the vicinity of 125 knots (an improvement of about + 6 knots) BUT my take off role would be very much longer and my climb less - in my situation this puts my life at risk.

 

 

[skippydiesel]

Some CS propeller suppliers have answered my letter of enquiry:

 

MT- Propeller:

·         The MTV-1-1A/170-51 Electric, Weight? Cost $16,606 Au

·          MTV-34-1-A/170-202 Hydraulic, Weight 7.5 kg Cost $13,700.00 Au

 

Comment: Both 2 blade configurations. Expensive. No rational or detailed information/photos, etc. CS prop must be returned to service shop at 600 hrs (?) I do not know the relative merits of electric versus hydraulic but do know that my Rotax will require modification ($$) to facilitate the hydraulic propeller.

 

Airmaster:

·         Originally AP332S fitted with blades WWR68W by Whirl Wind Weight 11.5 kg without controller, Cost $11,540

·         Revised AP420 with blades SNR70E by Sensenich. Weight, 9.1 kg without controller Cost $11,370

 

Comment:  Both are electric. AP33 -is a 3 blade & AP420 a 2 blade. Airmaster were very fast & professional in their response but left me a bit disquieted in their all to quick change to a 2-blade recommendation. CS props seem to be a bit on the heavy side. No suggested performance changes with CS. Bit odd that the 2 blade is almost the same price as the 3 – would have thought there would have been a more significant price difference.  At this stage pricing seems about mid-range for a CS Electric.

 

Helix- Carbon GmbH

Performance data using FK14 aircraft:

·         Comparing fixed 2 & 3 blade props with their hydraulic CS, H60A 1.75m R-SI-22-2, there was a +7 Knot improvement in climb and a - 5 Knot decrease in cruise (go figure).

·         No weights given or other details. Cost $10,826 – I have no idea if the controller comes with this.

 

So to date-

I am getting some feed back but its quite limited (other than price).

The MT-Proppeller hydraulic weight is very attractive even if the price is high.

Airmaster is still probably the leader, being local and all that.

Anyone care to expound on the relative merits of electric versus hydraulic and why one is so much lighter than the other.

[M61A1]

1 minute ago, skippydiesel said:

 

MS1A1 - I understand all of what you have said my question are:

 

What reputable CS propeller suppliers are there out there

What are the relative merits of the above

 

On your comment "WOT 5500 RPM" - if I were to set my existing ground adjustable prop for this, I have no doubt that my high speed cruise would be in the vicinity of 125 knots (an improvement of about + 6 knots) BUT my take off role would be very much longer and my climb less - in my situation this puts my life at risk.

 

 

Aware of that Skippy, that's why I said a CS prop would be beneficial.

Airmaster is the only significant experience I have. No problems with them and they are available with different blade type options. If I was buying one , they would be my choice.  

If you don't understand the merits of the CS pop, don't get one.

[skippydiesel]

1 minute ago, M61A1 said:

 

If you don't understand the merits of the CS pop, don't get one.

Its the relative merits of the suppliers and their offerings NOT the merits of CS props of which I am well versed in the theory and have some experience.

[kasper]

My two cents in summary

- a CS prop will provide a modest imprvement in TO roll over any fixted pitch/ground adjustable unless that prop is absolutely optomised for take off (and has crap cruise) - most aircraft coompares I can find only give around 10% improvement in TO performance ... useful if you need 800m to get off the ground, do so great if you get off in under 250m already

- a CS prop will provide a modest imprvement in cruise speed over any fixted pitch/ground adjustable unless that prop is absolutely optomised for cruise (and has crap TO) - most aircraft coompares I can find only give around 5% improvement in cruise performance ... useful if you need to get somewhere 3 minutes quicker per hour of cruise ...

- as far as I can see all available CS props are 4-5 times or more than the equivalent ground adjustable prop and involve another system to monitor and maintain

 

I can only comment on the variable pitch proprs I have tried over the years - thats in my posts above - but my position stands that I would rather take the $8k plus saved in the ground adjustable prop and either put it throgh the engine as fuel or use it in other operational ways on a fixed pitch/ground adjustable prop. 

[skippydiesel]

Thank you for your council Kasper - you have repeated all that I already know.

 

 

What I dont know is who supplies the best CS prop for my aircraft and objectives.

 

Are there no CS drivers out there, who wish to have their opinions aired in this Forum ?

[RFguy]

Skippy

 

My suggestion is put a ground adjustable prop on it , go and find a long runway to play with (Cowra)  so TO performance does not matter, and pitch it for max cruise at 5500. Above 5500 the engine starts to run out of breath it looks like .

 

That's tell you a bit about what might be achieved with a variable pitch.

 

Have a look at figures 4,5 and also the variable pitch prop table in the rotax manual. Fig4 suggests there isnt that much extra to be got .

 

Be sure to have some manifold pressure indication.

 

You hit the nail on the head when you told us the engine goes into the red red red so easily in WOT straight and level. Just how far will it go ? > 6000 ?

That margin I guess you dont know.

 

Your airframe is slippery and it might get close to the pure  speed increase  proportional to sqrt(thrust).  You are still a long way from Vne at 130 kts in that aircraft.

 

 

 

 

 

 

[facthunter]

Speed increase is never proportional to thrust It's A squared relationship. Twice the speed needs four times the thrust. Nev

[skippydiesel]

Quite extraordinary! We are now getting to the end of page 4 of this conversation and as yet not one contributor has addressed my original questions.

 

So far the conversation has, for the most part been negative, tending to focus on the  poor cost to effective ratio of a CS propellers in this class of aircraft, rather than performance characteristics? 

 

There does not seem to be any knowledge as to the merits of hydraulic versus electric CS props OR why hydraulics seem to be considerably lighter?.

 

It would appear that the few who actually want to discuss CS props are of the opinion that I wish to improve my TO/Climb despite refuting that several times?

 

It seems no one can imagine a CS prop improving cruise speed?

 

My references, in the CS context, to the amazing work of Robin Austen enlists nothing much more than silence?

 

What collisions can be drawn from this:

 

• There is no member of this Forum, with a level of experience  that gives then the confidence to respond to the original and repeated question, recommend a supplier /product ?
• The "opinionated" would rather indulge in negative thread drift than give constructive advice  Or admit ignorance?

I am disappointed in the 'Brains Trust"

 

[M61A1]

Here is someone who used an MT CS prop.

Perhaps there is generally silence because your responses are abrasive and bordering on rude.

It appears that every response is met with ridicule.

 

Edited October 24, 2020 by M61A1

[Paul davenport]

skip I feel your frustration. On the occasions that I have asked questions hoping to get some one who has actual experience, I get the same answers from I am sure we’ll meaning people who have an opinion but no hands on experience. You have my phone number call me and I will give you the name and number of some one who has actual hands on experience with what you are asking

[RFguy]

2 hours ago, facthunter said:

Speed increase is never proportional to thrust It's A squared relationship. Twice the speed needs four times the thrust. Nev

that's right, as I said  speed proportional to square root (thrust).

best case.... maybe approximated by a slippery plane where airflow is still mostly laminar at the increased speed

 

Boxy shapes will be increasingly turbulent hence what thruster said, alot of extra lph for not much IAS..... 

 

Skippy- maybe it is just that people cannot give you an answer.

I think I have given you the most simple answer :

 

- slippery plane will approximate square root rule

 

- put a ground adjustable prop on it  , and pitch it coarse, see how you go. 

 

That is the ONLY way you are going to know just how much you can wring out of that Rotax and that Airframe

 

Cowra is a good place to do it. Lachlan Valley Aviation  is right there, lots of people who know what they are doing, and a nice 1700m  asphalt strip and 1000m cross grass, and nothing to run into in any direction. even if it takes you 1000m to get airborne, plenty of room to play with the pitch.

 

you can do low level circuits on 33 to your hearts content. or go off up into the northern training area at 4000' and knock your socks off.

 

Edited October 24, 2020 by RFguy

[skippydiesel]

Guys! Guys! I apologize if my tone has been a bit off and offence taken but really not one person has come close to answering my question's. (MASSIVE FRUSTRATION))

 

I have a constant speed propeller endorsement and some limited real word experience of the same. So I have at least a basic understanding of how they work. 

 

I have never optimised my existing ground adjustable prop for high speed or cruise - just not practical in my circumstances.

 

Yes RFguy I could relocate to my local airfield or a host of others both near & far, just to find out how fast she will go with the prop so adjusted.  I know it will probably true out at about 125 knots. This is not the question - the question is about CS propeller supplier/manufactures and their products.

 

The question is not about my aircrafts performance per say but the reputation of the CS prop (delivering the goods) that I may purchase & fit in a few months time - so far no answers.

 

I have tried to stimulate the conversation & keep it a little on track by posting data/information/costs, on a small number of propeller suppliers/products - got virtually 0 response.

 

I have asked about the merits and weights of electric versus hydraulic - 0 response.

 

To be fair there have been one or two who have come close to making a constructive criticism.

 

To finish on a positive note - the conversation has, in general been stimulating, even if not to the point.

[skippydiesel]

3 hours ago, M61A1 said:

Here is someone who used an MT CS prop.

Perhaps there is generally silence because your responses are abrasive and bordering on rude.

It appears that every response is met with ridicule.

 

Great video M61A1 - If only  could afford a Rotax 915 IS Plus a linked/FADEC type ? propeller system. 

 

A comment on the marriage of a 141 Hp turbo  engine/CS prop motivating a little Kitfox - Everyone has different motives/pleasures in recreational aviation. This guy is obviously into the STOL world.

 

The MPH & US Gallons all sound good, until its converted to my comfort zone, litres and knots. So for a cruise of about 110 knots he is using about 38 L/hr  - doesn't "press my buttons"

 

If I had this power plant, optimised for altitude, I would stick it in something with a lot more speed/econamy potential but then I wouldn't be able to land on a mountain top with a 50 m ground ole..