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I spoke to Mr Monnett senior and junior at Oshkosh in 2011. Not specifically on that specific idea, but I did offer to get involved with the onex in a drag reduction role. They seemed little interested so I left it at that.
It’s not unusual for designers over the years to seem perhaps quietly offended by others messing with their design. 
I detected that may have been the case here, but couldn’t be sure.

 

 

 

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Hi Skippydiesel. Sorry, embarrassingly your name escapes me even though you’re my number 1 fan! Thank you sincerely for that and the kind words you write. I’ll let you know if I discover a

Hi. Here is the description of SRS that I promised. Apologies for the formatting.    SERA-173 (VH SRS) is the 3rd aircraft in my journey of developing evolutionary aircrafts originally based

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Hi skippydiesel and anyone else interested.

That sounds bad, can I ask your first name please?

i will respond to your prop question soon. 
Also. Thought you may be interested, I’m having a parallel conversation on the Sonerai.net site under “world record plane 12 years on” covering similar subject matter if you wish to tune in.

cheers

Robin

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Too bad about the Monnett family attitude - If the Sonerai does not evolve, it will ultimately disappear from the sky and become a footnote in the history of small aircraft aviation. I will certainly "check out" the Sonerai Forum

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Hi Robin, Which forum section is it under on Sonerai.net... Their search is suss and cant find it...

Cheers

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Hi SkippyD.

In reply to your prop query.
You are in the speed range where you might just justify a CS prop. But you will have the same expense as a faster plane, with less benefit, this makes it a hard decision.

I imagine that’s why Cessna couldn’t quite justify one on the 172, but made it standard on faster models.
On yours, depending on where you are pitched now, I t will give a bit more go, or at least liveability at both ends, but another benefit is that you can always find a smooth spot for cruise at any speed. Something that fixed props don’t always do.

re 3 vs 2 blade. From my experience, the biggest benefit with a 3 blade is even more smoothness. Buy expect to pay more and on your plane, lose just over 1 knot.

Hope that’s helpful.

Regards

Robin

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I forgot to mention - I have politely challenged the Airmaster recommendation of a 3 blade. They have come back to me, agreeing that the 2 blade may be a better bet.

I find myself a little discomforted by their rather too quick & easy capitulation and have sought further debate/argument - have heard no more at this time..

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I only went 3 blade cause this is my last major project and I didn’t want any compromises this time around. Spare no expense! Ha ha!

Also, as I get older, comfort and smoothness is getting more important to me.

Prior to this I have always gone with 2 blade. 
For ultimate performance, 2 blade is ahead based on all my testing., no question. 
As they say, 2 for go, 3 for show!

But (I might be biased) that 3 blade does look good!

 

Last thought. On some planes, the 3 blade makes the bottom cowl really hard to get off, particularly Sonerai non stretched versions.

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Thanks Robin

 

FYI Cessna did have a 172 with CS prop & retractable undercarriage - I did my endorsements in one. The one I hired was pretty old and tired and looked it but even so it seemed to get of the ground faster, better climb out and if memory serves me right , capable of about +10 knots on the fixed pitch version (the POH said more ).

 

When the time comes and the decision to/not purchase is made it will be under the assumption that I can preserve my existing excellent TO performance, while expanding, by at least 10 knots my cruise speed. Anything less will be a decision not to purchase.

 

The Airmaster cost of 2 versus 3 blade CS is very close - this was a surprise to me. The only slightly cheaper.

 

Just to clarify - in your opinion the 3 blade is smoother and is slightly slower (1 knot) than the 2 blade - have I got it right?

 

Somehow this communication seems to have got out of wack !

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It’s hard to predict what effect a CS will have on your plane.

if your existing prop is really fine, then it will be all in cruise and top end. If it’s really coarse, then the improvements will be in TO and climb. 
it also depends on target cruise density altitude among other things. I’m pretty sure you understand that.
It can be calculated if you have accurate MP, RPM and density altitude for a particular max speed scenario now.
If you are running out of revs badly now, 10+ kts is quite plausible. 
Just don’t have enough info and don’t want you to have unrealistic expectations if you hand over your dough.

 

From memory, the Airmaster 2 blade uses a more expensive hub, perhaps milled from an exotic alloy or not as large a production run or something, and that offsets the blade saving.

 

I suspect most 10+ knots Cessna gained over the “all round” fixed pitched was in the U/C drag reduction. I’m estimating Maybe 70%.??.

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Your interpretation of my explanation of 2 blade vs 3 blade Is correct.

 

And thanks for the invite. I may even do that!

 

Cheers.

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1 hour ago, R Austin said:

It’s hard to predict what effect a CS will have on your plane.

if your existing prop is really fine, then it will be all in cruise and top end. If it’s really coarse, then the improvements will be in TO and climb. 
it also depends on target cruise density altitude among other things. I’m pretty sure you understand that.
It can be calculated if you have accurate MP, RPM and density altitude for a particular max speed scenario now.
If you are running out of revs badly now, 10+ kts is quite plausible. 
Just don’t have enough info and don’t want you to have unrealistic expectations if you hand over your dough.

 

From memory, the Airmaster 2 blade uses a more expensive hub, perhaps milled from an exotic alloy or not as large a production run or something, and that offsets the blade saving.

 

I suspect most 10+ knots Cessna gained over the “all round” fixed pitched was in the U/C drag reduction. I’m estimating Maybe 70%.??.

This is why people like me talk at length with people like you and of course the propeller suppliers. When talking to a supplier, I like to not only get their recommendation but also their rational/justification. After all the best part of $12 k is not small change to a person like me. When no justification is forthcoming or the answers glib and possibly dismissive, I get a tad sceptical (do Airmaster read this Forum ?).

 

Attached is an information document I have prepared, after seeking information from a number of suppliers, to send to a potential CS Propeller Selection Info.docx Supplier

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Hi again Robin ; have just received costed recommendation from MT-Propeller; Very expensive at $16,600 for the electric CS. The hydraulic , at $13,700,  is still a bit above even the  most expensive electric alternative supplier.

 

Have you any comments on Hydraulic versus Electric ??

 

Both props are2 blade  MTV-1 -A . plus some other numbers & letters which may relate to hub type, not sure. No rational given for recommendation. No suggested performance figures. No explanation as to high cost or cost differences - have asked for all.

 

What little I know is that the hydraulic is very light at 7.5 KG including governor. Got nothing on the electric - dont even know what the slip ring arrangement or controller look like.

 

One MT plus is that they have a dealership/workshop at Bankstown NSW. Other than Airmaster in NZ, I dont know if any of the other LSA CS prop makers have "local" service provisions.

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  • 2 weeks later...

A few clarifications re VH-SRS resulting from recent questions off this thread....


- The target maximum continuous cruise speed (MCCS) for VH-SRS was 168 knots.

The actual MCCS has exceeded this and is currently 172.3 knots using Rotax’s latest maximum continuous cruise power for 95 RON fuel (91 US), or 174 knots using 98 RON (93 US) or avgas, if you like an average of 173.1 knots (199 MPH).


- All stated performance numbers are at favourable weights and CG. Variations to these parameters eg adding a passenger will reduce performance.

- The aerobatic weight is 430Kg (or 450Kg using part filled wing tanks), not 600 Kg gross.

Cheers
Robin

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Great achievement Robin - there are only a very few aircraft, in this (light) class ,that are claimed to be able to achieve 150 knots. I think all are retractable/CS  " fast glass" from Europe. I did see one, ultra sexy unit, that appeared to eclipse your achievement but when I double checked, it is using the Rotax 915 engine. Further investigation revealed that the same airframe powered by 912ULS, was still way behind SGS & SRS.

 

If there was a way to follow your build (even to get a 150 knot cruise) I think I might buy Sonerai 2 plans/kit tomorrow.

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7 hours ago, skippydiesel said:

If there was a way to follow your build (even to get a 150 knot cruise) I think I might buy Sonerai 2 plans/kit tomorrow.

The Sonerai is a wonderful plane to experience... I did 150 hours in 6 months...

but not to put a damper on ambition....

Just be aware, that this slippery little plane is a VERY sensitive plane to fly and its landing and ground handling has Major variants to most all of the tail draggers you may have flown

 

I intend to have the name 'Fiona' on the cowl of mine when she is back... Fiona from Shrek.. Treated right she is a Princess.. get rough and ham fisted and she becomes an Ogre and bites hard

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3 hours ago, skippydiesel said:

"I intend to have the name 'Fiona' on the cowl of mine when she is back"... Do tell what is happening to Fiona??

The plane or the Princess?

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Hi Skippy,

The Shrek Princess.. watch the movies..

 

My Princess Fiona... hasn't been christened yet ..  I am 4th owner... Built in SA as a GA.. Only did 35 hours with VH-WLF ( remember what I said about them being 'sensitive')  on it before it was sold to a Vic as 23-0826. .. then on to a Tas..

My first plane , so the learning cycle was high, and I hadn't realized the cooling baffles that had been install were for Canada, not Outback Western Qld.. so I literally cooked the motor..

Most of the 150 hours was over Winter so the lower ambient helped.. When it expired, pulled the motor, had it rebuilt by a VW specialist, as bulletproof as a standard VW could be.. but decided to go to the 2.2 Jab.. Bought the FF kit from Jab, but didn't like the design of the WA developed kit.. Was doing a redesign when life got in the way and it was parked in the back of my shed.. redesign is back on track all be it slowly. Had even bought a set of Doug's cowls as used on SGS ( picked them up from Robin) which I have never used, and probably won't as my redesign with maintain the originals. (for sale when need them....)

 

My second plane  the Terrier. I rate as an underrated ( and under stressed) plane, is the farm station wagon, compared to Soni, 'boring to fly', and already has all the performance you are looking for, 110-15 cruise yet a low stall speed with  take off in under 100m land in around 80 if pushed. I have landed and turned around in under 200 at Gross.. after one of my GPSs decided to be cantankerous, right at the start of a flight up into the Gulf. The Subaru, puts some people off, while it is a good motor it is getting on in years, something like an Aeromomentum would make it just that bit better.. There is even a pic on the website of your pricey preference in the front of one http://www.foxcon.com/Rotax-912.html... 

 

Cheers Lyle

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