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Performance of the mark III with 912 or jabiru?

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grantr

Joined: 12 Sep 2007
Posts: 217

Posted: Fri Nov 14, 2008 6:19 pm Post subject: Performance of the mark III with 912 or jabiru?

I know a few of you fly the MKIII C and X models with  912s.



What are your average cruise and stall speeds calibrated to ground speed and your climb rates and fuel burn?

 



Grant

rlaird

Joined: 10 Jan 2006
Posts: 373
Location: Houston

Posted: Fri Nov 14, 2008 6:46 pm Post subject: Performance of the mark III with 912 or jabiru?

MkIIIC w/ 912S & 3-blade Warp Drive prop, at field elevation of 235 msl



Slow cruise : 65mph

Fast cruise:  85mph

Stall:  42mph, no flaps

Climb rate:  on a good day, 1400fpm; average around 1100fpm

Fuel burn:  (at) 65mph, 3gph, (at)85 mph, 4.5gph

On Fri, Nov 14, 2008 at 8:19 PM, grantr <grant_richardson25(at)yahoo.com> wrote:

 	  Quote: 	
		   



 I know a few of you fly the MKIII C and X models with  912s.



 What are your average cruise and stall speeds calibrated to ground speed and your climb rates and fuel burn?

 Grant





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 14294#214294

_________________
~~~~~~~~~~~~~~~~~~~
Robert Laird
formerly: MkIIIc w/ 912ULS & Gyrobee
current: Autogyro Cavalon w/ 914ULS
Houston, TX area
http://www.Texas-Flyer.com

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Fri Nov 14, 2008 8:16 pm Post subject: Performance of the mark III with 912 or jabiru?

> I know a few of you fly the MKIII C and X models with  912s.

 	  Quote: 	
		   

 What are your average cruise and stall speeds calibrated to ground speed and your climb rates and fuel burn?

  

 

 Grant

 
	




Grant:



Help me out.



Are you referring to 912ULS? or 912's?



Also, explain "What are your average cruise and stall speeds calibrated to ground speed ", please.



I fly a mkIIIc with 912ULS:



Cruise 82-83 mph at 5,000 rpm loaded at max gross of 1,200 lbs.



Stalls clean, 10 gal fuel and me, about 38 mph.



With full flaps in ground effect as she breaks in a full stall landing, the needle is coming through 30 mph.



My 912ULS  burns 5 gph at 5,000, 5.5 gph at 5,200.



My 912UL burned 4 gph at 5,000 and 4.25 gph at 5,200, and 4.5 gph at 5400.



john h

mkIII

Mesquite, NV

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Nov 15, 2008 11:34 am Post subject: Re: Performance of the mark III with 912 or jabiru?

Grant,



The Rotax 912 is a vastly superior engine to the Jabiru in both performance and reliability.   The 912 turns the prop slower than the Jabiru and results in much better performance on a Kolb.   My numbers are very close to John and RLaird.     



Climb with a 912-S is about 1300 FPM at 5200 RPM,  Stall at 30, and slow cruise at 70 MPH burning just over3 GPH at 4200 RPM.   I don't do fast cruise, I have no numbers for that.   The 912 is perfect for the airplane...



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Ricochet

Joined: 29 May 2008
Posts: 36
Location: Fresno, CA

Posted: Sat Nov 15, 2008 2:52 pm Post subject: Performance of the mark III with 912 or jabiru?

Wellllll, there are some of us who would disagree that the 912 is vastly superior...and that it provides much better performance.    



Jerry



On Nov 15, 2008, at 11:34 AM, JetPilot wrote:

[quote] [quote][b]

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Nov 15, 2008 8:18 pm Post subject: Re: Performance of the mark III with 912 or jabiru?

[quote="Ricochet"]Wellllll, there are some of us who would disagree that the 912 is vastly superior...and that it provides much better performance. ï¿½ ï¿½



Jerry



On Nov 15, 2008, at 11:34 AM, JetPilot wrote:

[quote]  	  Quote: 	
		  [b] 	




Then you would be wrong...  It has been tried, and the results are in the archives to prove it.     The 912 is a better engine on a Kolb, PERIOD.  If you ended up with the inferior Jabiru on your Kolb, then I'm sorry for you, but that is no reason to try to get others to make the same mistake.



There is a really good reason that 80 % of all LSA airplanes today use the Rotax 912 series engine, and not the Jabiru.  It does not take a rocket scientist to figure this one out.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

NeilsenRM(at)comcast.net
Guest

Posted: Sun Nov 16, 2008 9:16 am Post subject: Performance of the mark III with 912 or jabiru?

Jerry/All

  

 A direct drive high RPM engine just can't produce  the same thrust per HP as a reduction drive engine turning a big slow  turning prop. I did a fairly close direct comparison between direct drive and  reduction drive and the differences were drastically better with the reduction  drive engine. The VW engine runs at a slightly higher RPM (3200 (at) cruise and  3500 (at) climb) than a Jabiru so the differences may not be as drastic but the  differences are still significant. The primary consideration is that a big slow  turning prop is more efficient in turning horse power into thrust than a small  higher RPM prop. I have seen a 85 HP Jabiru powered Kolb MKIIIX fly  and was impressed with it's performance but I would guess that this just  adequate performance is due to a no compromise highly tuned prop. Most  of us redrive powered Kolb flyers get sufficient performance that we tend  to migrate more towards durability, smoothness, convenience than ultimate  performance.  

  

 I first flew my Kolb MKIIIC with a direct drive VW.  The direct drive engine was 2180cc Great Plaines engine turning a 60 X 28  two bladed wood prop. I could only fly solo out of my strip and I would get a  65MKH cruise at close to 80% power. After a few years of flying this engine I  switched to a almost identical reduction drive VW engine on the same plane. The  reduction drive is a 1.6 to one drive turning a three bladed 72 inch PowerFin. I  gained two passenger performance, cruise speed increased to 75MKH with 65-70%  power, my oil/CHT temps lowered, my fuel consumption lowered, and all this  running the same engine RPMs as my direct drive engine. Again my  VW turns a bit more RPMs and my direct drive prop might not have been finely  tuned as it could have been but the differences are still vast.

  

 There is at least one kit airplane the offers a  120HP Jabiru as a option rather than offering a reduction drive engine. The  price of fuel will likely return to the $4/ gallon price so I feel it would be  best to get the most performance we can out of the horse power we  are feeding our airplanes rather than increasing the HP to get the needed  thrust.

  

 Rick Neilsen

 Redrive VW powered MKIIIC



 [quote]   ---

Ricochet

Joined: 29 May 2008
Posts: 36
Location: Fresno, CA

Posted: Sun Nov 16, 2008 9:45 am Post subject: Performance of the mark III with 912 or jabiru?

Rick, 

I appreciate your informed input.  I can't speak for Jabs/Rotax 4-cycle engines on Kolbs, but I can on Titans.  The arguments from both sides, I've found, change nobody's mind, typically generating more heat than light.  That said, I had both a Jab 2200 and a 3300 on my Titan and found performance comparable to reported performance of comparable 912s (of course the 100 hp 912 had fewer horses than the 128 hp Jab), and had slightly less fuel burn.  Every sport pilot here in Madera flies behind/in front of a Jab, with one also flying behind a 912S.  I could be a little biased, I've owned five Jab engines, and if buying another engine, that's prolly what I'd buy again, for various reasons, but I wouldn't hesitate to own a Rotax either.  For sure, very early Jabs had teething problems and didn't produce near the power claimed, but that was long ago and far, far in the past.  And, none of us have had to land out because of an engine problem.

Now, back to my cellar....

Jerry 

  

On Nov 16, 2008, at 9:15 AM, Richard & Martha Neilsen wrote:

[quote]Jerry/All

 

A direct drive high RPM engine just can't produce the same thrust per HP as a reduction drive engine turning a big slow turning prop. I did a fairly close direct comparison between direct drive and reduction drive and the differences were drastically better with the reduction drive engine. The VW engine runs at a slightly higher RPM (3200 (at) cruise and 3500 (at) climb) than a Jabiru so the differences may not be as drastic but the differences are still significant. The primary consideration is that a big slow turning prop is more efficient in turning horse power into thrust than a small higher RPM prop. I have seen a 85 HP Jabiru powered Kolb MKIIIX fly and was impressed with it's performance but I would guess that this just adequate performance is due to a no compromise highly tuned prop. Most of us redrive powered Kolb flyers get sufficient performance that we tend to migrate more towards durability, smoothness, convenience than ultimate performance.  

 

I first flew my Kolb MKIIIC with a direct drive VW. The direct drive engine was 2180cc Great Plaines engine turning a 60 X 28 two bladed wood prop. I could only fly solo out of my strip and I would get a 65MKH cruise at close to 80% power. After a few years of flying this engine I switched to a almost identical reduction drive VW engine on the same plane. The reduction drive is a 1.6 to one drive turning a three bladed 72 inch PowerFin. I gained two passenger performance, cruise speed increased to 75MKH with 65-70% power, my oil/CHT temps lowered, my fuel consumption lowered, and all this running the same engine RPMs as my direct drive engine. Again my VW turns a bit more RPMs and my direct drive prop might not have been finely tuned as it could have been but the differences are still vast.

 

There is at least one kit airplane the offers a 120HP Jabiru as a option rather than offering a reduction drive engine. The price of fuel will likely return to the $4/ gallon price so I feel it would be best to get the most performance we can out of the horse power we are feeding our airplanes rather than increasing the HP to get the needed thrust.

 

Rick Neilsen

Redrive VW powered MKIIIC



[quote]---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Nov 16, 2008 5:20 pm Post subject: Performance of the mark III with 912 or jabiru?

 	  Quote: 	
		     Wellllll, there are some of us who would disagree that the 912 is vastly superior...and that it provides much better performance.    

 

 

   Jerry

 
	




Does Jerry have a Jab powered Kolb?



I have a 912 powered Kolb and have had a chance to compare performance between John Williamson's Jab powered Kolbra and my mkIII.  I said "a chance", but that translates into many hours and days flying long cross country flights together when John W had the Jab.  To be quite honest, there was no comparison, except in cruise flight.  Cruise flight was comparable.  Takeoff and climb, the 912 powered mkIII ate the Jab powered Kolbra up.  



2005, I met John W in Canon City, CO, enroute to our annual flying at Monument Valley.  John had upgraded to a 912ULS.  He led me out of Canon City and I had to keep asking him to slow down and wait for me.  We were on our way to Leadville, CO.  Really irritated me that John W's Kolbra outperformed my mkIII.



I have known other direct drive Kolbs in the past.  Performance sucked with Jab, Subaru, and VW.  Haven't heard from our BMW powered Kolbs lately, but I don't think they will blow the doors off our 912 powered Kolbs either.



Any time you all want to go wing to wing and see which system outperforms which, Hauck is more than ready.  



john h

Mesquite, NV

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Nov 16, 2008 5:25 pm Post subject: Performance of the mark III with 912 or jabiru?

---- Jerry Jones <maderah2(at)sbcglobal.net> wrote: 

 	  Quote: 	
		   Rick,

 

 I appreciate your informed input.  I can't speak for Jabs/Rotax 4- 

 cycle engines on Kolbs, but I can on Titans.   > 

 Jerry

 

 
	


Jerry:



There is no comparison between a Titan and a Kolb.  



Direct drive may work on a Titan, but it does not work on Kolbs.



Would have saved some typing had you said you were a Titan guy and not a Kolb guy.  



Take care,



john h

Mesquite, NV until tomorrow...

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Ricochet

Joined: 29 May 2008
Posts: 36
Location: Fresno, CA

Posted: Sun Nov 16, 2008 10:16 pm Post subject: Performance of the mark III with 912 or jabiru?

John, no disagreement with you here about the difference between a  

Kolb and a Titan.  Was just responding to an imprecise, unqualified  

statement.  Like I've said previously, wish I still owned by 503 DCDI  

Firestar, but it is no more.  The new owner rolled it up in a ball  

when his tail caught the top wire of a barbed wire fence.  That said,  

me thinks you too may be a bit imprecise when you say direct drive  

doesn't work on a Kolb.  I've seen them work on even draggier  

pushers.  How about won't work as well as geared engines?

Okay.  That's it.  Now back to my hole until I see my shadow...

Jerry

On Nov 16, 2008, at 5:25 PM, <jhauck(at)elmore.rr.com>  

<jhauck(at)elmore.rr.com> wrote:

 	  Quote: 	

 ---- Jerry Jones <maderah2(at)sbcglobal.net> wrote:

> Rick,

>

> I appreciate your informed input.  I can't speak for Jabs/Rotax 4-

> cycle engines on Kolbs, but I can on Titans.   >

> Jerry

>

 Jerry:

 There is no comparison between a Titan and a Kolb.

 Direct drive may work on a Titan, but it does not work on Kolbs.

 Would have saved some typing had you said you were a Titan guy and  

 not a Kolb guy.  

 Take care,

 john h

 Mesquite, NV until tomorrow...

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Mon Nov 17, 2008 7:01 am Post subject: Re: Performance of the mark III with 912 or jabiru?

 	  Ricochet wrote: 	
		  

Was just responding to an imprecise, unqualified  

statement.  

Jerry



	




Jerry,



There was nothing imprecise or unqualified about my statement, I did my research very well before I decided to put the Rotax 912 instead of the Jabiru on my Kolb.  My information was correct, and your statement in response is wrong PERIOD.  When someone asks a question, I give them good information in a very clear and direct manner so there is no room for misunderstanding.   



You trying to dismiss accurate information as unqualified or imprecise just because you did not want to hear it, or because you have an axe to grind with the person posting is nothing short of childish and disservice to those reading and trying to make good choices for their Kolbs.   



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Mon Nov 17, 2008 8:10 am Post subject: Re: Performance of the mark III with 912 or jabiru?

 	  John Hauck wrote: 	
		  



Jerry:



There is no comparison between a Titan and a Kolb.  



Direct drive may work on a Titan, but it does not work on Kolbs.



Would have saved some typing had you said you were a Titan guy and not a Kolb guy.  



Take care,



john h

Mesquite, NV until tomorrow... 	




Don't mean to jump in, but forced to agree. I've flown both (tho my Kolb time in all in an FS II) and the airplanes fly quite a bit differently.



The titan is a slipperier plane with a wider speed range, so a small prop turning fast can work really well. The Kolb is more of a heavy-lifting plane with a flat bottomed airfoil. So you don't have to contend with as wide of a speed range, and slower turning, large props work better there.



I.e. I ran a 68" 3 blade warp drive on my FSII (3.47:1 gearboxed 503) and that was just about the perfect combo for the plane.



For what it's worth, my Titan has the 912ULS on it and only the jab 3300 with more than 20hp more can equal the climb I get (1800 to 2000fpm solo at about 2000' MSL). I could smoke a similar plane fitted with the 2200 .



LS

_________________
LS
Titan II SS

james.clayton(at)quantumw
Guest

Posted: Mon Nov 17, 2008 12:17 pm Post subject: Performance of the mark III with 912 or jabiru?

Greetings all.  

 

This conversation on direct drive vs. reduction drive resurfaces

periodically as new folks come onto the list.  The issue as so well

explained by several posters with experience flying Kolbs is the speed range

and parasitic/aerodynamic drag profile of a Kolb is vastly different than

say a Titan, or other slippery speedster.  



I posted an examination of these factors in 2004 and thought it might be

helpful to repost:



--

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