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Engine choice Sonerai I

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user 116312

Member
Joined
Aug 20, 2020
Messages
16
Was wondering whether 80 hp (Jabiru 2200 or Rotax 912) is a viable option for Sonerai I airframe?
 
I would say that both are viable. The Jabiru would be easier because it is a direct drive, air-cooled, wet sump engine. The 912 is a dry sump, liquid cooled so you have to find a place to mount the oil tank and radiator. The 912 is also gear drive to the prop, so really it likes a larger diameter prop whereas the Sonerai generally uses a short prop (52-56 inches). If going with a 912 you might need taller landing gear for more prop clearance which would hurt visibility in the 3-point attitude. Both would require modifications to the fuselage and cowling at a minimum.
 
Here are some mock ups of both the Rotax and the Jabiru.
I asked Sonex for a more accurate drawing of the cowl, but they did not answer me, so I have had to use the line drawing in my set of plans. I am guessing Sonex is not really all that interested in the Sonerai anyway.jabiru sonex.JPGSonerai jabiru.JPGRotax sonerai.JPGSonerai rotax.JPG
Straight away, the Jabiru is not conducive to the line drawing of the cowl without significant extension to the prop shaft because of the deep drop of the sump line.
It may be even more significant given the weight difference between the Jabiru and the VW derivative that I am assuming the line drawing is done on.
 
Can't speak for certain but I think a member here Cosmic is running a 3300 Jabiru on his S1 that I've heard is a hot rod. His fuselage is covered with sheet aluminum which I'm sure helps the CG issue hanging a larger engine off the front. Curious to know what he had to do to make it work???

I'm working on something similar but using a standard 2276cc VW driving an engineered coaxial reduction mounted to the "right" side of the engine. No bearing adder/modifications to the engine/case needed and mounts to the existing transaxle bolt holes. Only adder is a second stage to the oil pump for thrust bearing/planetary lube/scavenge. I'm at 18lbs added weight to a "flywheel drive" install but can run as large a prop as I want - have to stay within MOI numbers the reduction was designed for. Calculated thrust numbers not confirmed but almost double what a direct drive will put out with prop size and HP limits. Max engine RPM 4000 (should consevatively top 90hp at max RPM) and prop output "standard aircraft" 2750rpm. Shooting to have the reduction completed this summer. I have all this drawn in Solidworks (Tks to EAA) and some parts finished including custom flywheel with inertia ring with planetary that is loctited and ready to install. S2 tube fuselage (solo only) and RV 3 gear in the model now with 65" prop but I do have a complete S1 airplane (not currently flying) I may modify to make all this work. And don't ask about the wing...tapered trailing edge and increased chord significantly on root side to allow for larger spar section. Comes out to same wing loading with additional weight. Same engineer who did the reduction will run FEA's on multiple spar configurations I have drawn. Just having fun! (Working on exhaust now - mirrored just to see what it would look like)
Sonerai2_ReductionComplete.pngCompleteParts.jpgSide.pngtopengine.png
 
What program is it that you're using for your 3d modelling?
Rhino
Beautiful rendering - i'd like to learn to do the same!
Thank you, but only one of the screenshots is a render. The others are an emap on the surfaces, with the surfaces set to 40% transparency.
Where would you locate the radiator , oil cooler and muffler?
Good question. This is only at concept stage, so while the thrust line is basically set, the rest isn't. Drawing the cowls using a surface modeller means that once a concept is decided upon, it can (within limits) be scaled in any direction, and at any point to accommodate a fitment. One real concern I have is the weight differential between a Rotax/Jabiru installation and a VW one. If the line drawing that came with my plans is correct, a Rotax/Jabiru fitment will need to be significantly forward of the VW one.

I am planning to build a Sonerai and to that end, I have bought a set of plans. Living in Australia means I do need to consider other powerplant options. Sonex offer a cowl set on their website, but as I previously mentioned they don't even answer genuine queries anymore.
 
Can't speak for certain but I think a member here Cosmic is running a 3300 Jabiru on his S1 that I've heard is a hot rod. His fuselage is covered with sheet aluminum which I'm sure helps the CG issue hanging a larger engine off the front. Curious to know what he had to do to make it work???

I'm working on something similar but using a standard 2276cc VW driving an engineered coaxial reduction mounted to the "right" side of the engine. No bearing adder/modifications to the engine/case needed and mounts to the existing transaxle bolt holes. Only adder is a second stage to the oil pump for thrust bearing/planetary lube/scavenge. I'm at 18lbs added weight to a "flywheel drive" install but can run as large a prop as I want - have to stay within MOI numbers the reduction was designed for. Calculated thrust numbers not confirmed but almost double what a direct drive will put out with prop size and HP limits. Max engine RPM 4000 (should consevatively top 90hp at max RPM) and prop output "standard aircraft" 2750rpm. Shooting to have the reduction completed this summer. I have all this drawn in Solidworks (Tks to EAA) and some parts finished including custom flywheel with inertia ring with planetary that is loctited and ready to install. S2 tube fuselage (solo only) and RV 3 gear in the model now with 65" prop but I do have a complete S1 airplane (not currently flying) I may modify to make all this work. And don't ask about the wing...tapered trailing edge and increased chord significantly on root side to allow for larger spar section. Comes out to same wing loading with additional weight. Same engineer who did the reduction will run FEA's on multiple spar configurations I have drawn. Just having fun! (Working on exhaust now - mirrored just to see what it would look like)
View attachment 15809View attachment 15808View attachment 15810View attachment 15811
That is great work!
I am aiming to build a Sonerai I as close to the original as I can reasonably manage, but the limited support options for a VW fitment is the reason I am considering other power plant alternatives.
Another concern I have is to whether or not 80hp is too much for the basic design.
 
That is great work!
I am aiming to build a Sonerai I as close to the original as I can reasonably manage, but the limited support options for a VW fitment is the reason I am considering other power plant alternatives.
Another concern I have is to whether or not 80hp is too much for the basic design.
I would consider 80hp barely adequate. Can I assume you are familiar with Robin Austin's machine?
He has posted information about it here.
https://www.sonerai.net/threads/world-record-plane-12-years-on.4975/#post-37851
Where in Australia are you, if I may ask? I'm in South East QLD
 
I would consider 80hp barely adequate. Can I assume you are familiar with Robin Austin's machine?
He has posted information about it here.
https://www.sonerai.net/threads/world-record-plane-12-years-on.4975/#post-37851
Where in Australia are you, if I may ask? I'm in South East QLD
I live in the Blue Mountains NSW.
Perhaps I didn't quite understand, but I understood that the original Sonerai I would have had around 65HP, and the Sonerai II was designed for 80HP. Is this correct?
Yes. I have seen Robin's website and it is very impressive!
 
I live in the Blue Mountains NSW.
Perhaps I didn't quite understand, but I understood that the original Sonerai I would have had around 65HP, and the Sonerai II was designed for 80HP. Is this correct?
Yes. I have seen Robin's website and it is very impressive!
It is my understanding that they were designed for VW engines and 80hp is about all you can get out of them reliably in an aero application. They don't really have enough finning to get rid of the heat and when you add typical Australian temperatures, it doesn't get any better.
Jabiru seem to be a mixed bag. Some love them, others hate them. There did appear to be some reliability issues, but again, some say it's because of poor manufacturing while others say it's poor maintenance. I would say have a look around and see how many Jabs you can find with engine hours that match airframe hours.

Rotax are expensive, but as has been mentioned, it's very rare that you see one that just stopped because it fell apart. Most Rotax failures seem to be the result of poor installation.
The 100hp rotax , I would think is about perfect for any Sonerai, if you can afford one. People are starting to ask ridiculous prices for TBO engines, which can still go another 2000 hrs if you choose wisely.

I mentioned Robin's aircraft, because you can see where the radiator and such are located and the clean design of the cowl.
 
I have a Hornet STOL with a 914/Airmaster prop combination installed. It was very expensive at the time, but with hindsight it was well worth the expense. I think the UL engines may prove to be a good long term choice too.

I have hesitated with building a Sonerai because:
  • The cowl and canopy are problematic.
  • Although I have the skills and experience to build my own cowl, the process is long and expensive for a one off.
  • I have no experience with the moulding skills needed to form a clear canopy.
  • I am very doubtful of the support I might receive from Sonex should I opt for their parts.
On the plus side:
  • I have experience with TIG welding light gauge 4130.
  • I have a CNC router and I have experience in producing hole matched flying surfaces with 6061 T6 sheet.
 
Love your work.I might cop some criticism for this but early stages of a S1 build here in Brisbane. Also planning a 3.3 jab like cosmic then on copying the carbon rear like Mike Patey did on scrappy.
 
Love your work. Might cop some criticism for this but early stages of a S1 build here in Brisbane. Also planning a 3.3 jab like cosmic then planning on copying the carbon rear like Mike Prat did on scrappy.
 
Love your work. Might cop some criticism for this but early stages of a S1 build here in Brisbane. Also planning a 3.3 jab like cosmic then planning on copying the carbon rear like Mike Prat did on scrappy.
The Jabiru engine does polarize opinion. I owned one of the original Jabiru's that came with a 1600cc engine. A few months later the 2200 became available so I upgraded. I instructed in that Jabiru for around 1500 hours and it was worked very hard. The only problem encountered was the original valves needed some work at around 400 hours. What some may not realize is that there are 4 phases of Jabiru engine. Phase 1 used solid lifters and it was reliable. Phase 2 and 3 used hydraulic lifters and these engines were less reliable but still satisfactory for many people. Of course if you have had a failure then your opinion will be negative. Phase 4 is the current engine and I have only heard good things about it.

Have owned 2 VW powered aircraft (Tipsy Nipper and Corby Starlet) and in my opinion the Jabiru is superior. The VW engines can only produce around 80hp reliably as M61A1 says. When I sold the Tipsy Nipper, the new owner put a Jabiru 2200 in it and it was smoother and performed a lot better.

With regard to the best engine for a Sonerai, the Jabiru 3300 seems a perfect match. Using a standard length engine mount (but stronger) the CG came out exactly where I wanted it. The plane will do 190 knots flat out and cruises around 175. Handling is similar to a Pitts Special that I used to own but the Sonerai feels a lot lighter. I have not spun my Sonerai so cannot comment on how the longer engine and nose affects spin recovery. Bill from Canada has a 3300 in his Sonerai 2 so if he sees this he may care to make his own observations about the suitability of the engine.
 
The Jabiru engine does polarize opinion. I owned one of the original Jabiru's that came with a 1600cc engine. A few months later the 2200 became available so I upgraded. I instructed in that Jabiru for around 1500 hours and it was worked very hard. The only problem encountered was the original valves needed some work at around 400 hours. What some may not realize is that there are 4 phases of Jabiru engine. Phase 1 used solid lifters and it was reliable. Phase 2 and 3 used hydraulic lifters and these engines were less reliable but still satisfactory for many people. Of course if you have had a failure then your opinion will be negative. Phase 4 is the current engine and I have only heard good things about it.

Have owned 2 VW powered aircraft (Tipsy Nipper and Corby Starlet) and in my opinion the Jabiru is superior. The VW engines can only produce around 80hp reliably as M61A1 says. When I sold the Tipsy Nipper, the new owner put a Jabiru 2200 in it and it was smoother and performed a lot better.

With regard to the best engine for a Sonerai, the Jabiru 3300 seems a perfect match. Using a standard length engine mount (but stronger) the CG came out exactly where I wanted it. The plane will do 190 knots flat out and cruises around 175. Handling is similar to a Pitts Special that I used to own but the Sonerai feels a lot lighter. I have not spun my Sonerai so cannot comment on how the longer engine and nose affects spin recovery. Bill from Canada has a 3300 in his Sonerai 2 so if he sees this he may care to make his own observations about the suitability of the engine.
Just to clarify. 120hp in a Sonerai I airframe and (probably more importantly), a Sonerai I wing. Is that correct? If so, what are the dimensions of the propeller?
 
Reliability is obviously the common thread here. My only concern with going Rotax (new) is that you will never get the investment back out of the engine/plane if and when you sold and/or moved on to a different airframe. These Sonerai's are not valued high enough to warrant 20-25k on a new Rotax (not sure what Rotax is going for these days) as they may get $15k max for a flying plane?!? My early years of flying were all behind two stroke 447/503's - I hear the same gear reduction rattle in the $60-$100k Rotax powered airplanes on the ramp at idle. My personal opinion is to go for the lower RPM reliability and rebuild the VW every 200hrs. The way I fly, an engine will last several years. In that time I can build another engine and have on a test stand for less than a 1/4 of the Rotax cost. Just replace worn parts after the two cores are setup. No reduction noise, no added radiator and oil catch can to worry about mounting, etc. Just my 2 cents...
 
The Jabiru engine does polarize opinion. I owned one of the original Jabiru's that came with a 1600cc engine. A few months later the 2200 became available so I upgraded. I instructed in that Jabiru for around 1500 hours and it was worked very hard. The only problem encountered was the original valves needed some work at around 400 hours. What some may not realize is that there are 4 phases of Jabiru engine. Phase 1 used solid lifters and it was reliable. Phase 2 and 3 used hydraulic lifters and these engines were less reliable but still satisfactory for many people. Of course if you have had a failure then your opinion will be negative. Phase 4 is the current engine and I have only heard good things about it.

Have owned 2 VW powered aircraft (Tipsy Nipper and Corby Starlet) and in my opinion the Jabiru is superior. The VW engines can only produce around 80hp reliably as M61A1 says. When I sold the Tipsy Nipper, the new owner put a Jabiru 2200 in it and it was smoother and performed a lot better.

With regard to the best engine for a Sonerai, the Jabiru 3300 seems a perfect match. Using a standard length engine mount (but stronger) the CG came out exactly where I wanted it. The plane will do 190 knots flat out and cruises around 175. Handling is similar to a Pitts Special that I used to own but the Sonerai feels a lot lighter. I have not spun my Sonerai so cannot comment on how the longer engine and nose affects spin recovery. Bill from Canada has a 3300 in his Sonerai 2 so if he sees this he may care to make his own observations about the suitability of the engine.

Curious on what your gross is Cosmic?
 
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