VH - SGS Soneri II

[onetrack]

Arron25, use Google search to find it. Use the search term, (sonerai.net: world record plane 12 years on). You need to register or log in to see the discussion.

 

https://www.sonerai.net/threads/world-record-plane-12-years-on.4975/post-37851

[R Austin]

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

[skippydiesel]

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..

[R Austin]

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.

[skippydiesel]

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 !

[skippydiesel]

Robin - When boarders are opened, there will always be a welcome for you at The Oaks. Just say the word !

[R Austin]

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%.??.

[R Austin]

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

 

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

 

Cheers.

[skippydiesel]

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

[skippydiesel]

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.

[skippydiesel]

Hi Robin - just responded to your "private" communique but not sure if got through - please confirm  success/failure?

[R Austin]

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

[skippydiesel]

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.

[skippydiesel]

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

[skippydiesel]

6 hours ago, Arron25 said:

The plane or the Princess?

Your choice I guess.

[puggo1]

Hi Robin, 

I've just read of your fantastic aeroplanes VH-SGS & VH-SRS. I've been planning to build an aircraft for sometime. It'll now be a retirement project due to my other commitments in about 4 years. 

 

My original homebuilt desire was a modified Beachner with a Leyland/Rover V8 ans side by side seating. I bought the plans in 1984 and their so faded, I've been re-inking them and sketching it into CAD. However,  as I live in England and flying to Europe is fraught with difficulty, I'd like a more economic trailerable aeroplane. Your VH-SRS fits the bill exactly. 

 

I've avidly read your articles on the modifications (size, structure, etc) and agree with them. Any chance of documenting these for us builders or may I offer to do it for you? All royaltes you way?

 

regards

Graham

Essex, UK

[skippydiesel]

Hi Graham, Should Robin not see/respond to your enquiry, try reaching out to him on the Sonerai Forum https://www.sonerai.net/