Prop Selection

[skippydiesel]

Great video - Bolly seems to be doing the job but cant find one anywhere on the web

[skippydiesel]

10 minutes ago, FlyBoy1960 said:

The Bolly in-flight adjustable is being tested/developed at our airfield. There have been a couple of blades that have let go and the other day (about three weeks ago) the propeller went into beta mode at about 200 AGL after rotation requiring the aircraft to crash land into a pond. I am not sure if they are going to keep going with the project

Wow!!!!!

[Kyle Communications]

I was told a few weeks ago they are having major dramas with the electronic control...cant get it working well enough. Need some pretty good software guys to get it sorted and that takes a lot of money...believe me I know...The software guy we use for the stuff I develop at work is amazing but he is also paid accordingly

 

Bolly should just start with the IFA  much simpler and easier and you can start getting some bucks back in for your development. I am pretty sure a lot of people would just like the manual IFA

[kasper]

Sorry to hear Bolly have lost blades and had beta range issues on the IFV prop.

 

I recall watching the tests on the three blade prop in the UK to get it accepted for certification - 100hp limit on the prop and 2800rpm max use required the prop to be spun up to 150% rev limit ... it took dull throttle on the landrover V8 to get there and I can assure you nobody was willing to be anywhere in the propr disc as we went through the power runs to just over 4,200 rpm.

 

 

 

[Kyle Communications]

Just had a email back from Eprop...they will be offering a manual and a electric and a hydraulic system for their units

[skippydiesel]

31 minutes ago, Kyle Communications said:

Just had a email back from Eprop...they will be offering a manual and a electric and a hydraulic system for their units

Good-oh! Sooner rather than later I hope.

[Kyle Communications]

mid 2021 she says so you might have your nosewheel fixed by then 

 

[skippydiesel]

2 hours ago, Kyle Communications said:

mid 2021 she says so you might have your nosewheel fixed by then 

 

I wish it was just the nose wheel BUT look on the bright side without the insurance  $$$ I would not be fantasising about propeller selection

[Kyle Communications]

When the noseleg of the sav was ripped off it was bottom cowl and floor and oil cooler and radiator also a prop and spinner and a gearbox inspection rebuild. Beauty was the insurance paid for all the parts and even paid me to fix it. One of the advantages of building your own

 

[RFguy]

Of course the  unwanted configuration of that Bolly CS prop in the previous post should be taken in context- all R&D, and shouldn't reflect anything, since we  know few facts.

 

After flying in a CS prop aircraft yesterday,  an RV, and seeing the additional workload for all but a simple flight (takeoff, cruise, land)  I think you have to really , really want it, to justify the large increase of complexity compared to a fixed prop. 

 

SkippyD, may I naively suggest  a coarser prop and a turbo  on your Rotax to improve your short takeoffs ????  There are a few 912ULS engines around with non factory turbocharger setups on them. They're only very small turbos...Or get a 914... You don't need alot of extra performance....

 

 

 

 

 

 

 

 

Edited October 16, 2020 by RFguy

[skippydiesel]

1 hour ago, RFguy said:

Of course the  unwanted configuration of that Bolly CS prop in the previous post should be taken in context- all R&D, and shouldn't reflect anything, since we  know few facts.

 

After flying in a CS prop aircraft yesterday,  an RV, and seeing the additional workload for all but a simple flight (takeoff, cruise, land)  I think you have to really , really want it, to justify the large increase of complexity compared to a fixed prop. 

 

SkippyD, may I naively suggest  a coarser prop and a turbo  on your Rotax to improve your short takeoffs ????  There are a few 912ULS engines around with non factory turbocharger setups on them. They're only very small turbos...Or get a 914... You don't need alot of extra performance....

 

 

Thanks RF - I dont know where/when the perception that I have a TO concern has come from - "Fake News" - couldn't be further from the truth. My sub 100 m ground roll and 1500+ft/min climb out is okay with me - I am looking for a higher cruise speed while maintaining my TO performance

Refer your comments on CS Prop Management - As a fugitive from GA I have my CS endorsements, so am well aware of and accept the additional knowledge/skills required BUT (isn't there always) technology can, if you choose, make the demands less - if you purchase one of the electric prop control systems, it is (almost) as simple as selecting, using a rotating knob/switch, TO - Climb  -Cruise - Hold (econamy cruise). Its a good idea to have a manifold vacuum gauge but not absolutely necessary (unless you start to use the manual adjust) Not too onerous in my book.

1 hour ago, RFguy said:

 

 

 

 

 

 

[RFguy]

Hi Skippy.  I agree. The CS prop is the ideal. 

Maybe a catapult launch ? OK, not helpful. Seems from my own enquiries, you wont get much change from $11k, which is about turbo cost.. The $64 question is will you get 15-20% out of the CS prop? (putting aside the useful cruise improvements afforded with the CS prop for cross country) 

I've made a few enquiries of my own with Airmaster, they are very responsive and helpful.

 

[skippydiesel]

RF - You have it in the "nut shell" - Will I get a significant increase in cruise performance, while preserving my already excellent TO performance????

 

My own Airmaster enquiries have been responded to with great efficiency HOWEVER they seemed somewhat generic to me. I have written back asking for a justification of their recommendation - I wait in anticipation of their reply.

 

The quote(s) from Airmaster were in the $11+k range, including delivery but not GST.

 

In the mean time I have contacted MT-Propeller who have responded equally fast but with a different emphasis - They require a detailed questionnaire to be completed on all matters regarding the subject aircraft (so far a bit different to Airmaster). 

 

Turbocharging ?? - Hmmmmm??? I am a diesel freak, so am enamoured of turbo charging, as a way of improving volumetric efficiency, while potentially reducing pollution (cleaner burn) BUT turboing an engine not specifically designed for it, has a whole range of potential problems that must be addressed, if you are hoping for significant power increase and service  longevity/reliability of the engine. In short, no matter what anyone says, its not a magic bolt on power improvement

[spacesailor]

Skippy

Try

Jato or Rato, seems to work wonders !. LoL  spacesailor

 

 

[Thruster88]

Skippy,  if a turbocharger has no appeal perhaps a shot of nitrous would help you clear the terrain 😂 

[RFguy]

Catapult launch to get out of his short  strip and a cruise prop....

Is there any specific rule in the regs that prohibits catapults to launch RAaus aircraft ?

Sorry Skippy, thread drift. But it does sound like you want another 20 hp. change the 912 for a Jab 3300.

 

 

[skippydiesel]

Ha Ha! its great to hear the jokers are all on song.  By all means have your fun but have you read about Robin Austen's most recent masterpiece VH-SRS,  in General Discussion VH-SGS Soneri II -

 

Look what you can do with a humble Rotax 912 ULS & a CS prop and a massive dollop of talent

 

• 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 

•  

• 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

Puts are plebeian effort into perspective

[Thruster88]

Skippy, one way to get some idea how much extra performance a constant speed prop will give you is to look at aircraft that have fixed and VP option. The Tecnam p2010 is one such example, a little faster than yours so more to gain from VP. 

 

P2010 performance from their website.  180hp lycoming.

                                                    Fixed          constant speed.

Max cruise                                   134knots     137knots

Take off to 50ft                            626m           595m

Climb rate                                    764fpm         841fpm

Range                                          591nm            600nm

 

So the max cruise only 3knots better, the take off advantage is negligible, the climb rate is better but the engine is working harder and using more fuel because that is what the constant speed allows it to do. The range says it all, there is no magic efficiency gain.

 

I am sure you can find other examples.  

[skippydiesel]

Thanks Thruster - Certainly gives a tightwad like me cause to think again. My instinct, probably wrong, is that the main limiting factor is the airframe - assuming of course that the engine power is appropriate/adequate.

 

If you look at what Robin Austen has been able to achieve, with the same engine I use, it suggest to me that a meticulous clean up of the draggy bits ( anal attention to detail) will yield great incremental potential gains . However these gain can only be realised if the engine can translate its power into thrust over the speed range.  Robin's first Sonerai, VH-SGS, needed  the help of a CS prop to break World Records.

 

The 180 hp Tecnam power to weight ratio is lower than my aircraft and its climb rate a lot lower - is this an indicator of unused power potential?

 

With my existing prop/setting, I can just make about 120 knots @ 5500 rpm for a fuel burn of about 17 L/h - The POH max cruise is 124 knots. The low fuel consumption (if correct) indicates the engine may be lightly loaded  (potential for pitch coarsening) & the potential cruise suggest some  ruise performance increases may be possible.

 

Robin's aircraft  are about 50-60 knots faster than mine is today. I will be positively ecstatic if I achieve a 10 knot increase in econamy cruise.

[facthunter]

IF you get your prop exactly correct for  cruise it will be better at cruise than an adjustable one is. ALL of the sea plane racers (Schneider Trophy) of the 30's had fixed pitch props and took off from water (with great difficulty due the large torque ) but went nearly 3 times the speed of what you are dealing with. A  C/S's is a compromise too.  

[skippydiesel]

4 hours ago, facthunter said:

IF you get your prop exactly correct for  cruise it will be better at cruise than an adjustable one is. ALL of the sea plane racers (Schneider Trophy) of the 30's had fixed pitch props and took off from water (with great difficulty due the large torque ) but went nearly 3 times the speed of what you are dealing with. A  C/S's is a compromise too.  

I understand fully but unlike a Schneider Trophy sea plans with  prop optimised for speed, that have an almost limitless take off run and can climb out very slowly (if desired) without fear of any obstructions,  I must perform a short field take off followed by a steep climb to minimise my already substantial risk.

[Yenn]

If a CS prop is too complex for you and you find it hard to keep up with, should you really be flying?

[Flying Binghi]

Would one of them Borer props work ? Used by some on the Super Cubs.

 

 

 

 

.

[Thruster88]

7 hours ago, skippydiesel said:

 

With my existing prop/setting, I can just make about 120 knots @ 5500 rpm for a fuel burn of about 17 L/h - The POH max cruise is 124 knots. The low fuel consumption (if correct) indicates the engine may be lightly loaded  (potential for pitch coarsening) & the potential cruise suggest some  ruise performance increases may be possible.

 

I will be positively ecstatic if I achieve a 10 knot increase in econamy cruise.

If the figures above are with your prop set for a safe takeoff from your farm I think you will be disappointed with a cs prop. Your current 120knot cruise is occurring at about 65% power, the 5500rpm being the limit. Yes the cs prop will allow a higher cruise power setting but the fuel consumption will go up alot for only a little gain, all aircraft work this way. You don't seem like the guy who will burn 5lph to go 5-6 knots faster.

[RFguy]

At the end of the day  you cannot break laws of physics which means x1.1 increase in airspeed will required (1.1 * 1.1) = x 1.21  increase in thrust...

That assumes the airflow does not get more turbulent around the fuselage etc at higher airspeeds (more drag)

This is probably TRUE for Skippy's plane. at least to a point.....

 

if 65% power  is current, then going to 75% power  will yield  a 7.4% increase in airspeed, all other things being equal. (and 15% increase in fuel consumption, all things being equal and proportional) . (and also that propeller efficiency is constant- which it is NOT).

 

Edited October 22, 2020 by RFguy