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ifly4fun2(at)sbcglobal.ne
Guest

Posted: Sun Nov 04, 2007 10:17 am Post subject: Powerplant Choices

All,

I've been looking into powerplants for my 701 even

though I'm not even close to hanging the engine.  Has

anyone considered the UL260i over the 912 for its

direct-drive, Electronic Variable Timing and fuel

injection? A major downside is a $2500 price increase

and un-proven reliability.  With some optimism, by the

time I'm done with the airframe it will probably have

proven itself and the strength of the dollar will be

back up.  I have not found anyone installing it on the

701 but the site says a 601 installation is coming

soon.  Any thoughts?



http://www.ulpower.com/

do not archive

Art

Buttoning up the Rudder

john.marzulli(at)gmail.co
Guest

Posted: Sun Nov 04, 2007 10:46 am Post subject: Powerplant Choices

Taking a look at their performance data, it seems to run at the same RPM as the Jabiru 3300.



http://www.ulpower.com/ul260i-perf.htm

 On Nov 4, 2007 10:14 AM, Art Olechowski <ifly4fun2(at)sbcglobal.net (ifly4fun2(at)sbcglobal.net)> wrote:

 	  Quote: 	
		   --> Zenith-List message posted by: Art Olechowski <ifly4fun2(at)sbcglobal.net (ifly4fun2(at)sbcglobal.net)>



All,

I've been looking into powerplants for my 701 even

though I'm not even close to hanging the engine.  Has 

anyone considered the UL260i over the 912 for its

direct-drive, Electronic Variable Timing and fuel

injection? A major downside is a $2500 price increase

and un-proven reliability.  With some optimism, by the 

time I'm done with the airframe it will probably have

proven itself and the strength of the dollar will be

back up.  I have not found anyone installing it on the

701 but the site says a 601 installation is coming 



	


-- 

John Marzulli

http://701Builder.blogspot.com/



"Flying a plane is no different than riding a bicycle... it's just a lot harder to put baseball cards in the spokes. 

-Airplane The Movie  [quote][b]

psm(at)ATT.NET
Guest

Posted: Sun Nov 04, 2007 1:47 pm Post subject: Powerplant Choices

Hi Art,



I took a look at the web information on the new engine.  I don't know 

how well it fits the 701 since I am building a 601, but I did a 

comparison between the Jabiru 3300 and UL260i specifications.



It seems like the 3300 offers about a 25% power advantage for about 

the same weight as the UL260i.  This weight (and purchase package) 

includes a 20 amp alternator, and I suspect the UL260i doesn't 

include any alternator.  I could be wrong about that, but I didn't 

see it listed on the web pages I examined.  I would imagine the 3300 

runs a lot smoother as well since it has 6 cylinders rather than 

4.  On the other hand, the fuel injection sounds attractive.  I am a 

little reluctant to buy off on the FADEC concept, but I am just old 

and tired and don't want to dig into this concept enough to become 

comfortable with it.



I don't think this engine provides enough power to be a good choice 

for a CH601XL, but it might be a nice amount of power for the 

701.  Rather than considering the Rotax for the 701 I would take a 

good long look at the Jabiru 80 hp engine.



Good luck,



Paul

XL fuselage

do not archive



At 10:14 AM 11/4/2007, you wrote:

 	  Quote: 	
		  



All,

I've been looking into powerplants for my 701 even

though I'm not even close to hanging the engine.  Has

anyone considered the UL260i over the 912 for its

direct-drive, Electronic Variable Timing and fuel

injection? A major downside is a $2500 price increase

and un-proven reliability.  With some optimism, by the

time I'm done with the airframe it will probably have

proven itself and the strength of the dollar will be

back up.  I have not found anyone installing it on the

701 but the site says a 601 installation is coming

soon.  Any thoughts?

secatur

Joined: 02 Nov 2006
Posts: 50
Location: New Zealand

Posted: Tue Nov 06, 2007 1:45 am Post subject: Re: Powerplant Choices

Here we go again..I am Jabiru fan, but will the 2200 pushing a direct drive prop preserve the STOL characteristics of the 701 ? If so why we anyone opt for the much more complicated arrangement of a redrive (geared or belt) to allow a 72 " prop to be used for optimum stol performance ??????

psm(at)ATT.NET
Guest

Posted: Tue Nov 06, 2007 4:04 am Post subject: Powerplant Choices

I'm afraid this thread is getting beyond my experience.  I would have 

thought the primary issues in engine selection involved things like 

horsepower, weight, required accessories (like the PSRU and water 

circulation system needed for the Rotax engines).  I didn't know 

there was an issue in the size propeller indicated to convert the 

engine's power to thrust.



I was merely trying to answer the original poster's question with a 

specification review.



I did do a little further research on the web and learned the Jabiru 

folks do offer a complete firewall forward kit for the 701.  Perhaps 

Pete can make more informed comments on the performance for this 

engine and airframe combination.



Paul

XL fuselage

do not archive

At 01:45 AM 11/6/2007, you wrote:



 	  Quote: 	
		  Here we go again..I am Jabiru fan, but will the 2200 pushing a 

direct drive prop preserve the STOL characteristics of the 701 ? If 

so why we anyone opt for the much more complicated arrangement of a 

redrive (geared or belt) to allow a 72 " prop to be used for optimum 

stol performance ??????

notsew_evets(at)frontiern
Guest

Posted: Tue Nov 06, 2007 6:06 am Post subject: Powerplant Choices

I built an Avid Flyer years ago and it had a Rotax 582 with a 3/1 gear box. 

The thing had torque up the ying yang.

I hated it!  It swung a 72/42 prop and climbed like a scalded cat.  I still 

hate Rotax.  I swapped out the Rotax for a 2200A Jabiru.  I loved that 

Jabby.  It was like flying behind a sewing machine.  Very good engine, just 

not the torque without the gear box..  My 2200 swung a 62 inch prop.  Now I 

m totally a Jabiru believer..

My Zenith 601 has the 3300 and I expect the same good flying as with the 

2200....

What I m saying is that the bigger the prop you can swing, the better torque 

youll have.

I just dont like gear boxes.

Look at the Cessna 175....  not popular to most....

GEAR BOX...



SW

---

larry(at)macsmachine.com
Guest

Posted: Tue Nov 06, 2007 7:23 am Post subject: Powerplant Choices

The 2200 has enough horsepower for fast light aircraft, but may lack the 

torque to deliver great climb power for a 701.  A re-drive is often one 

way to match the best peak horsepower rpm with a larger prop to deliver 

better climb performance. 

Larry McFarland  601HDS at www.macsmachine.com

do not archive



secatur wrote:

 	  Quote: 	
		   



 Here we go again..I am Jabiru fan, but will the 2200 pushing a direct drive prop preserve the STOL characteristics of the 701 ? If so why we anyone opt for the much more complicated arrangement of a redrive (geared or belt) to allow a 72 " prop to be used for optimum stol performance ??????

larry(at)macsmachine.com
Guest

Posted: Tue Nov 06, 2007 7:48 am Post subject: Powerplant Choices

Steve,

I agree, the 2-cycle Rotax delivers the most raw power per pound, noise, 

vibration and high fuel usage. The gear box is something most 

experimenters are unable to repair

or deal with. Belt drive systems can be very reliable, quiet, easy to 

inspect and aren't much to maintain. 



I disagree with the comment that putting a larger prop on an engine 

equates to more torque.  It doesn't.  Matching the horsepower curve to 

the correct prop provides

the best means to selectively extract speed or torque from the engine. I 

fly a Subaru and the belt drive is well matched for the performance I 

need. It's quiet and very economical to own and operate.   Not as simple 

or as fast as the Jabaru to be sure, but a great performer.



Larry McFarland  601HDS at www.macsmachine.com



steve wrote:

 	  Quote: 	
		   



 I built an Avid Flyer years ago and it had a Rotax 582 with a 3/1 gear 

 box. The thing had torque up the ying yang.

 I hated it!  It swung a 72/42 prop and climbed like a scalded cat.  I 

 still hate Rotax.  I swapped out the Rotax for a 2200A Jabiru.  I 

 loved that Jabby.  It was like flying behind a sewing machine.  Very 

 good engine, just not the torque without the gear box..  My 2200 swung 

 a 62 inch prop.  Now I m totally a Jabiru believer..

 My Zenith 601 has the 3300 and I expect the same good flying as with 

 the 2200....

 What I m saying is that the bigger the prop you can swing, the better 

 torque youll have.

 I just dont like gear boxes.

 Look at the Cessna 175....  not popular to most....

 GEAR BOX...



 SW

notsew_evets(at)frontiern
Guest

Posted: Tue Nov 06, 2007 8:33 am Post subject: Powerplant Choices

OK Larry,

I m not a for real expert so I ask this:

Why was it that my Rotax 65 horse power engine would easily swing a 74 inch 

/ 46 pitch prop and my 85 horse power Jabiru would only handle a 62 / 28 

prop ?

Torque ?  Gear box ?



Ever see a P 51 with that ol 16 foot prop ?

Talk about torque...  Absolutely full right rudder on take off....



SW



---

larry(at)macsmachine.com
Guest

Posted: Tue Nov 06, 2007 9:19 am Post subject: Powerplant Choices

Steve,

The Rotax and its gear box were matched to optimize power for the larger 

prop.  The 80-hp Jabiru measures its horsepower at the peak of the power 

curve

which is probably an rpm that is too high for the limited rpm of the 

propeller.  Lots of engine makers advertise hp that is greater than the 

rpm we can use.

On the P 51 you only need to count the 12 huge cylinders to understand 

the torque available to the 16-foot prop.  I believe all that torque was 

really

only available at top speeds too, despite the fact that Merlin had a 

gear reduction drive to the prop shaft.



Larry McFarland



steve wrote:

 	  Quote: 	
		   



 OK Larry,

 I m not a for real expert so I ask this:

 Why was it that my Rotax 65 horse power engine would easily swing a 74 

 inch / 46 pitch prop and my 85 horse power Jabiru would only handle a 

 62 / 28 prop ?

 Torque ?  Gear box ?



 Ever see a P 51 with that ol 16 foot prop ?

 Talk about torque...  Absolutely full right rudder on take off....

n801bh(at)netzero.com
Guest

Posted: Tue Nov 06, 2007 4:37 pm Post subject: Powerplant Choices

Guys, the main reason for a larger diameter prop on the 701/801 STOL series of planes is to have a greater blast of air off the prop to hit the rear tail feathers, that makes them more effective at lower airspeeds. High speed planes don't need this,or at least to a reduced extent. There is a guy in Wis that is building an 801 and had the idea to use the 8 cyl Jabiru. That motor only makes max power at 3300 rpms. Definatly not a good match for an 801.



ack the 

torque to deliver great climb power for a 701.  A re-drive is often one 

way to match the best peak horsepower rpm with a larger prop to deliver 

better climb performance. 

Larry McFarland  601HDS at www.macsmachine.com

do not archive



secatur wrote:

[quote] --> Zenith-List message posted by: "secatur" <appraise1(at)bigpond.com>



 Here we go again..I am Jabiru fan, but will the 2200 pushing a direct drive prop preserve the STOL characteristics of the 701 ? If so why we anyone opt for the much more complicated arrangement of a redrive (geared or belt) to allow a 72 " prop to be used for optimum stol performance ??????



  &nbs========================       -- Please Support Your Lists This M                        ==================================================================================================================================================

    	  Quote: 	
		  [b]

ifly4fun2(at)sbcglobal.ne
Guest

Posted: Tue Nov 06, 2007 8:19 pm Post subject: Powerplant Choices

Larry,

When comparing the 912S to the UL260i the UL should have adequate torque to pull the 701 through

those high angles of attack.  I used these two sources for my quick analysis:

http://www.ulpower.com/downloads/UL260%20brochure%20EN.pdf

http://www.zenithair.com/pdf-doc/912uls-100hp.pdf 



All atmospheric conditions set aside the UL260i produces ~150lb/ft of torque (at)3300rpm and 95hp 

and 912S produces ~83lb/ft or torque(at)5500 and 95hp.



However I believe the key for this installation to work would be prop pitch and swing combination

to obtain a compromise of thrust to accommodate all phases of flight.  Would you agree? or am I

way off?



do not archive

Art

--- LarryMcFarland <larry(at)macsmachine.com> wrote:



 	  Quote: 	
		   

 <larry(at)macsmachine.com>

 

 The 2200 has enough horsepower for fast light

 aircraft, but may lack the 

 torque to deliver great climb power for a 701.  A

 re-drive is often one 

 way to match the best peak horsepower rpm with a

 larger prop to deliver 

 better climb performance. 

 

 

 Larry McFarland  601HDS at www.macsmachine.com

 do not archive

 

 secatur wrote:

 > 

 <appraise1(at)bigpond.com>

 >

 > Here we go again..I am Jabiru fan, but will the

 2200 pushing a direct drive prop preserve the STOL

 characteristics of the 701 ? If so why we anyone opt

 for the much more complicated arrangement of a

 redrive (geared or belt) to allow a 72 " prop to be

 used for optimum stol performance ??????

 >

 >   

 

 

 

 Click on

 about

 Admin.

 browse

 Un/Subscription,

 FAQ,

 http://www.matronics.com/Navigator?Zenith-List

 Forums!

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Wed Nov 07, 2007 12:56 am Post subject: Re: Powerplant Choices

Art,



I use the 2200 in the 701 and it is adequate. I expect the ULpower to do slightly bettter but its unlikely to overtake a geared setup like the 912S.



Reading these figures thru, you will not see 3300 rpm in the steep climb attitude, with the ULpower it will likely make  2900 - 3000 rpm so you are getting 85 hp to 90 hp & 150 ft/lb torque into a 64" prop? 



The Rotax should manage 95 hp under load with 2.43 reduction makes the 83 ft /lb into 201 ft / lb driving a 68"  or 72" prop. The larger prop being also more efficient is why Zenair recommend the 912 as a starting point.



I'm changing to a 64" x 30" prop to get a better match for climb rate, as the only other 2200 (previously HKS then Corvair) 701 in NZ has just done. The standard prop supplied by Jabiru was 60" x 38". I do not expect it to climb like a homesick angel with the new prop, and it was my choice to go direct drive air cooled for many reasons. Perhaps one good feature of the ULpower is compatible engine mounts, because once you decide on a powerplant the FWF kit becomes locked in and expensive to change later.



Ralph

_________________
Ralph - CH701 / 2200a

larry(at)macsmachine.com
Guest

Posted: Wed Nov 07, 2007 6:35 am Post subject: Powerplant Choices

Art,

The largest prop for the hp, adjusted for a best pitch is probably the 

best compromise.

The final choice on prop length and pitch setting is best answered by 

Warp Drive as they

would have the most direct experience with the combinations for the 701.



Larry McFarland  601HDS at www.macsmachine.com

do not archive



Art Olechowski wrote:

 	  Quote: 	
		   



 Larry,

 When comparing the 912S to the UL260i the UL should have adequate torque to pull the 701 through

 those high angles of attack.  I used these two sources for my quick analysis:

 http://www.ulpower.com/downloads/UL260%20brochure%20EN.pdf

 http://www.zenithair.com/pdf-doc/912uls-100hp.pdf 



 All atmospheric conditions set aside the UL260i produces ~150lb/ft of torque (at)3300rpm and 95hp 

 and 912S produces ~83lb/ft or torque(at)5500 and 95hp.



 However I believe the key for this installation to work would be prop pitch and swing combination

 to obtain a compromise of thrust to accommodate all phases of flight.  Would you agree? or am I

 way off?



 do not archive

 Art

 --- LarryMcFarland <larry(at)macsmachine.com> wrote:



   

> 

> <larry(at)macsmachine.com>

>

> The 2200 has enough horsepower for fast light

> aircraft, but may lack the 

> torque to deliver great climb power for a 701.  A

> re-drive is often one 

> way to match the best peak horsepower rpm with a

> larger prop to deliver 

> better climb performance. 

> Larry McFarland  601HDS at www.macsmachine.com

> do not archive

>

> secatur wrote:

>     

>> 

>>       

> <appraise1(at)bigpond.com>

>     

>> Here we go again..I am Jabiru fan, but will the

>>       

> 2200 pushing a direct drive prop preserve the STOL

> characteristics of the 701 ? If so why we anyone opt

> for the much more complicated arrangement of a

> redrive (geared or belt) to allow a 72 " prop to be

> used for optimum stol performance ??????

>     

>>   

>>

ifly4fun2(at)sbcglobal.ne
Guest

Posted: Wed Nov 07, 2007 11:03 am Post subject: Powerplant Choices

Thanks for your in sight Larry.  Are you still planning on installing the VW on your 701? 



Art

--- LarryMcFarland <larry(at)macsmachine.com> wrote:



 	  Quote: 	
		   

 

 Art,

 The largest prop for the hp, adjusted for a best pitch is probably the 

 best compromise.

 The final choice on prop length and pitch setting is best answered by 

 Warp Drive as they

 would have the most direct experience with the combinations for the 701.

 

 Larry McFarland  601HDS at www.macsmachine.com

 do not archive

 

 

 

 Art Olechowski wrote:

 > 

 >

 > Larry,

 > When comparing the 912S to the UL260i the UL should have adequate torque to pull the 701

 through

 > those high angles of attack.  I used these two sources for my quick analysis:

 > http://www.ulpower.com/downloads/UL260%20brochure%20EN.pdf

 > http://www.zenithair.com/pdf-doc/912uls-100hp.pdf 

 >

 > All atmospheric conditions set aside the UL260i produces ~150lb/ft of torque (at)3300rpm and 95hp

 

 > and 912S produces ~83lb/ft or torque(at)5500 and 95hp.

 >

 > However I believe the key for this installation to work would be prop pitch and swing

 combination

 > to obtain a compromise of thrust to accommodate all phases of flight.  Would you agree? or am

 I

 > way off?

 >

 > do not archive

 > Art

 > --- LarryMcFarland <larry(at)macsmachine.com> wrote:

 >

 >   

 >> 

 >> <larry(at)macsmachine.com>

 >>

 >> The 2200 has enough horsepower for fast light

 >> aircraft, but may lack the 

 >> torque to deliver great climb power for a 701.  A

 >> re-drive is often one 

 >> way to match the best peak horsepower rpm with a

 >> larger prop to deliver 

 >> better climb performance. 

 >>

 >>

 >> Larry McFarland  601HDS at www.macsmachine.com

 >> do not archive

 >>

 >> secatur wrote:

 >>     

 >>> 

 >>>       

 >> <appraise1(at)bigpond.com>

 >>     

 >>> Here we go again..I am Jabiru fan, but will the

 >>>       

 >> 2200 pushing a direct drive prop preserve the STOL

 >> characteristics of the 701 ? If so why we anyone opt

 >> for the much more complicated arrangement of a

 >> redrive (geared or belt) to allow a 72 " prop to be

 >> used for optimum stol performance ??????

 >>     

 >>>   

 >>>

ifly4fun2(at)sbcglobal.ne
Guest

Posted: Wed Nov 07, 2007 11:31 am Post subject: Powerplant Choices

Ralph,

Thanks for your response I'm just trying to get educated maybe its time to for me to do some more

reading...but is it not true that RPM is controlled by throttle input and prop pitch and limited

by HP?  I guess I don't understand why the pitch of the prop could not be adjusted (reduced pitch

angle) such that 3300rpm can be obtained during climb with the result of decreased climb

performance? Now this definitely defeats the capability of STOL flight profile but still possible,

right? 

do not archive

Art 



--- jetboy <sanson.r(at)xtra.co.nz> wrote:



 	  Quote: 	
		   

 

 Art,

 

 I use the 2200 in the 701 and it is adequate. I expect the ULpower to do slightly bettter but

 its unlikely to overtake a geared setup like the 912S.

 

 Reading these figures thru, you will not see 3300 rpm in the steep climb attitude, with the

 ULpower it will likely make  2900 - 3000 rpm so you are getting 85 hp to 90 hp & 150 ft/lb

 torque into a 64" prop? 

 

 The Rotax should manage 95 hp under load with 2.43 reduction makes the 83 ft /lb into 201 ft /

 lb driving a 68"  or 72" prop. The larger prop being also more efficient is why Zenair recommend

 the 912 as a starting point.

 

 I'm changing to a 64" x 30" prop to get a better match for climb rate, as the only other 2200

 (previously HKS then Corvair) 701 in NZ has just done. The standard prop supplied by Jabiru was

 60" x 38". I do not expect it to climb like a homesick angel with the new prop, and it was my

 choice to go direct drive air cooled for many reasons. Perhaps one good feature of the ULpower

 is compatible engine mounts, because once you decide on a powerplant the FWF kit becomes locked

 in and expensive to change later.

 

 Ralph

 

 --------

 Ralph - CH701 / 2200a

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=144369#144369

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Wed Nov 07, 2007 9:16 pm Post subject: Re: Powerplant Choices

Art,



I'm not sure how to answer that one - my understanding is that if you set the pitch so low that the engine is producing full rated hp 3300 rpm in climb, then you indeed get the best rate of climb.  The problem comes when you try to cruise, you cannot go any faster. the 701 is slow enough as it is, without limiting it to 50 mph.  With a CSU, you get best possible climb because full fine pitch allows the engine to rev to full ratings - If I recall correctly sometimes we had to limit the throttle on TO run to keep the mp in limits (Cessna 207) depending on the day.



So in real life the prop is set to allow rated max. rpm when full throttle is applied in level flight. For all my previous aircraft this was the situation. I had geared 503s and warp drive props, and a metal sensenich on an 0-200 and I had that one repitched and got 2750 in level and better climb rate. A 2 blade 68" warp drive was better than a 3 bladed 62".



This is all very easy if using adjustable props the trouble is only the hollow carbon fibre  sensenich is suitable for the Jabiru and most direct drives, so the option I've taken is to buy one more wood prop with different numbers, now that I've had plenty of experience with the 60", and see how that runs. If its any help, my landing run is much longer than any takeoff, so the less efficient prop is more a nuisance than a problem. 



Ralph

_________________
Ralph - CH701 / 2200a

psm(at)ATT.NET
Guest

Posted: Thu Nov 08, 2007 7:58 am Post subject: Powerplant Choices

Hi Art,



I think the whole subject of prop pitch vs. rpm vs. horsepower and 

torque is a bit too complicated for the simple statements you made.



The ideal solution to all this would be to have a variable pitch 

propeller with a governor that adjusts the prop pitch to give the 

desired rpm at the current engine setting and flight condition (climb 

or descend or level flight).  Such a device already has been invented 

- it is called a constant speed propeller.  All high performance 

planes with propellers are equipped with this gizmo.  This is clearly 

the ideal solution for performance at the expense of complex 

equipment with corresponding cost.  It also gives a poorly trained 

pilot the opportunity to break the engine if he sets the controls 

improperly.  I presume it is for these reasons (cost and risk) that 

this wonderful equipment is denied to Sport Pilots.



If you are limited to fixed (or ground adjustable) propellers then 

you must find a compromise between climb and cruise performance.  If 

you use a propeller that gives you maximum rpm during climb then it 

will exceed the rpm redline if full throttle is applied under cruise 

conditions.  This is not a good choice.  Usually a prop is chosen 

that allows for maximum cruise rpm with a reduced climb capability or 

maximum climb capability with reduced cruise speed.



I hope this helps you understand the basic problem of propeller 

choices.  If you know which type of performance you want most then a 

salesman from the propeller company can tell you which prop to 

purchase.  That is the easy part.



Paul

XL fuselage

At 11:28 AM 11/7/2007, you wrote:

 	  Quote: 	
		  



Ralph,

Thanks for your response I'm just trying to get educated maybe its 

time to for me to do some more

reading...but is it not true that RPM is controlled by throttle 

input and prop pitch and limited

by HP?  I guess I don't understand why the pitch of the prop could 

not be adjusted (reduced pitch

angle) such that 3300rpm can be obtained during climb with the 

result of decreased climb

performance? Now this definitely defeats the capability of STOL 

flight profile but still possible,

right?

ifly4fun2(at)sbcglobal.ne
Guest

Posted: Fri Nov 09, 2007 7:15 am Post subject: Powerplant Choices

Paul,

Since I'm asking such elementary questions, I'm a bit embarrassed to mention this at this point

but I do have an A&P, so several years back I was quite familiar with the concept of fixed,

ground-adjustable, controllable, constant speed etc...props.  However, I've never practiced with

my A&P in the GA world only on heavies.  With that said, I'm trying revive all that good info I

was taught in school relating to GA because as the old saying goes "if you don't use it, you lose

it".

I do agree a constant speed, controllable or a two position controllable pitch prop would be the

ideal solution to match the UL engine rpm with prop pitch to obtain the best climb and cruise

performance.  

I still believe that the UL could achieve 3300RPM in climb with the correct prop pitch and swing

but the inability to increase prop pitch at cruise would jepordize your speed capability as

mentioned by Ralph and if power was not reduced at straight and level the engine would be over

redlined as you mentioned.  At this point, I'm not certain I would want to tinker enough to find

the best performance comprimise but the UL engine features sure do look appealing...

Thanks for the refresher course, if we cross paths in the future I owe you both a beer.

do not archive

Art

--- Paul Mulwitz <psm(at)att.net> wrote:

 	  Quote: 	

 Hi Art,

 I think the whole subject of prop pitch vs. rpm vs. horsepower and 

 torque is a bit too complicated for the simple statements you made.

 The ideal solution to all this would be to have a variable pitch 

 propeller with a governor that adjusts the prop pitch to give the 

 desired rpm at the current engine setting and flight condition (climb 

 or descend or level flight).  Such a device already has been invented 

 - it is called a constant speed propeller.  All high performance 

 planes with propellers are equipped with this gizmo.  This is clearly 

 the ideal solution for performance at the expense of complex 

 equipment with corresponding cost.  It also gives a poorly trained 

 pilot the opportunity to break the engine if he sets the controls 

 improperly.  I presume it is for these reasons (cost and risk) that 

 this wonderful equipment is denied to Sport Pilots.

 If you are limited to fixed (or ground adjustable) propellers then 

 you must find a compromise between climb and cruise performance.  If 

 you use a propeller that gives you maximum rpm during climb then it 

 will exceed the rpm redline if full throttle is applied under cruise 

 conditions.  This is not a good choice.  Usually a prop is chosen 

 that allows for maximum cruise rpm with a reduced climb capability or 

 maximum climb capability with reduced cruise speed.

 I hope this helps you understand the basic problem of propeller 

 choices.  If you know which type of performance you want most then a 

 salesman from the propeller company can tell you which prop to 

 purchase.  That is the easy part.

 Paul

 XL fuselage

 At 11:28 AM 11/7/2007, you wrote:

 >

 >

 >Ralph,

 >Thanks for your response I'm just trying to get educated maybe its 

 >time to for me to do some more

 >reading...but is it not true that RPM is controlled by throttle 

 >input and prop pitch and limited

 >by HP?  I guess I don't understand why the pitch of the prop could 

 >not be adjusted (reduced pitch

 >angle) such that 3300rpm can be obtained during climb with the 

 >result of decreased climb

 >performance? Now this definitely defeats the capability of STOL 

 >flight profile but still possible,

 >right?

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Mon Nov 12, 2007 12:22 pm Post subject: Re: Powerplant Choices

Does 20hp really make that much of a difference? The 601HD was originally designed for 65hp if I'm not mistaken.



I've heard that it takes 25% more power to go 10% faster. Personally, I'd guess that an 80hp engine, even on a 601XL is sufficient.



Just an analogy here. I used to have a 18' aluminum starcraft boat. Originally it had a 140hp engine on it, It did about 48mph with that arrangement, maybe 50 tops. I took that off and mounted a 70hp evinrude. With the 70hp engine, the boat went a solid 36mph, or about a 25% reduction in speed for a 50% reduction in power, there was no major noticable difference in getting it up on plane either. From everything everyone is describing of the 601XL with a 100hp engine and how it has about double the climb numbers of a Cessna 152, I'd have to imagine an 80hp instead of 100hp is not that big of a difference, certainly not to the point that it would be a safety concern. The 601XL is considerably lighter than a Cessna 152, and if I'm not mistaken, an O-200 is actually rated at like 90hp, not 100hp. So an XL with an 80hp engine would still seem 'zippy' by comparison I'd have to imagine.



In regards to a 701, you're probably getting less than 10% increase in speed for an additional 25% power between an 80hp and a 100hp and from the way that thing climbs anyway, I'd say it's probably not an issue.



Also, isn't a larger diamter prop more efficient than a smaller diameter prop. Right there I'd say a larger diameter prop is where you're climb is, not so much the horsepower. True, you need that horsepower to turn that prop, but the intersect of the curves would probably indicate a larger prop turning slower, that could be done by a 80hp engine, is where your climb performance is. Another rule of thumb I've heard, that outside 10% of the propeller blades do 90% of the work. That larger that disc section is, the more you're getting out of the prop.



Just an interesting sidenote, fastest propeller driven airplane ever, 575mph, the propellers were insanely large. There was an article in one of the old Experimenters years back about the propeller design and theory of this plane, but most importantly it's just outright the size of the props, and they don't spin fast at all, they just move a lot of air.

http://en.wikipedia.org/wiki/Tupolev_Tu-95#Specifications_.28Tu-95MS.29



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