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Zodiac XL Cruise Speed with 80HP

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jim.lanier(at)charter.net
Guest

Posted: Sat Mar 22, 2008 6:17 am Post subject: Zodiac XL Cruise Speed with 80HP

Can anyone tell me the difference in XL cruise speed between the 80hp 

and the 100hp Rotax. The website does not show performance with that 

engine. Also, how about with a 75hp VW conversion?



Jim

MHerder

Joined: 11 Feb 2008
Posts: 143
Location: Fort Worth TX

Posted: Mon Mar 24, 2008 9:07 am Post subject: Re: Zodiac XL Cruise Speed with 80HP

I have wondered about this from time to time, has anyone tried powering an XL with a Jab 2200?



I know the manual calls for 80-120 hp.  My thoughts are that climb would be affected much more than cruise.  I personally like the idea of having the extra power to get you out of trouble, but would imagine that even with an 80hp it would still probably out perform a Cherokee 140.

_________________
Zodiac 601 HD
Jabiru 3300
Wood Sensinich 64x47
Finally Flying

Matt Ronics

Joined: 30 Apr 2007
Posts: 22

Posted: Mon Mar 24, 2008 3:03 pm Post subject: Re: Zodiac XL Cruise Speed with 80HP

Already having on-hand a C-85, I called Zenith about using it in the XL.  In summary, I was advised that I probably wouldn't be pleased with the performance.  At the same time, I was told that this would be an excellent engine in a 601HD/S.



Of note you are asking for "cruise speed" with the 80hp engine.  Note that, generally speaking, it is climb performance, and not cruise, that is effected more by changing cubes.   For example, using Van's numbers for the RV-4, increasing the HP 17% will give you a 6% improvement in cruise and a 25% improvement in climb.  



Having thought this through in the past, I recall coming to the conclusion that the XL with 85hp would perform like a C-150.  I spoke with one 601HD (standard fat wing) owner with a C-85...his numbers were very close to or less than those of a C-150.

John75142

Joined: 05 Dec 2007
Posts: 56
Location: Kaufman, TX

Posted: Mon Mar 24, 2008 3:43 pm Post subject: Zodiac XL Cruise Speed with 80HP

Would you be interested in selling the C-85?



John (Scratch building 701)

Kaufman, Tx

---

_________________
John Short

planecrazydld(at)yahoo.co
Guest

Posted: Thu Mar 27, 2008 4:51 am Post subject: Zodiac XL Cruise Speed with 80HP

you will lose one or the other more than one or the other! The way you select the prop is everything. More diameter and flatter pitch will always yield better climb than smaller diameter and higher pitch - they produce optimized cruise.

   

  There is no reason that everyone in todays Experimental movement forgets that virtually all entry level airplanes used to be frugal gas sippers with extremely poor climb performance. If you chjoose to optimize the prop for climb and are willing to settle for a cruise of 100-110 you can still get great climb with the XL on well less than 100 hp.



ics <e_jocular(at)yahoo.com> wrote:

  [quote]--> Zenith-List message posted by: "Matt Ronics" 



Already having on-hand a C-85, I called Zenith about using it in the XL. In summary, I was advised that I probably  [quote][b]

larry(at)macsmachine.com
Guest

Posted: Thu Mar 27, 2008 6:12 am Post subject: Zodiac XL Cruise Speed with 80HP

Matt,

The analogy to the C150 is pretty close, but I'd think improved by the 

601s weight advantage and wing.  The HD would be less because of the 

thickness of the wing.

On the other hand, a HDS would not be a performer because the 23 foot 

wingspan needs a 100 hp engine to climb and cruise decently.  With my 

Stratus Subaru, the

economy cruise is excellent and climb is very good, but the climb is 

nowhere close to an HD with the same engine.



Larry McFarland 601HDS at www.macsmachine.com



Matt Ronics wrote:

 	  Quote: 	
		   



 Already having on-hand a C-85, I called Zenith about using it in the XL.  In summary, I was advised that I probably wouldn't be pleased with the performance.  At the same time, I was told that this would be an excellent engine in a 601HD/S.



 Of note you are asking for "cruise speed" with the 80hp engine.  Note that, generally speaking, it is climb performance, and not cruise, that is effected more by changing cubes.   For example, using Van's numbers for the RV-4, increasing the HP 17% will give you a 6% improvement in cruise and a 25% improvement in climb.  



 Having thought this through in the past, I recall coming to the conclusion that the XL with 85hp would perform like a C-150.  I spoke with one 601HD (standard fat wing) owner with a C-85...his numbers were very close to or less than those of a C-150.

Mainwheels

Joined: 29 Oct 2007
Posts: 5

Posted: Thu Mar 27, 2008 8:23 am Post subject: Zodiac XL Cruise Speed with 80HP

Hi;

The CH-601HDS easily outperforms the C150 with an 80 hp 912. Of course, 

even more so with the 100hp.

Mike

CH-601 HDS

1200+hours



LarryMcFarland wrote:

 	  Quote: 	
		   

 

 

 Matt,

 The analogy to the C150 is pretty close, but I'd think improved by the 

 601s weight advantage and wing.  The HD would be less because of the 

 thickness of the wing.

 On the other hand, a HDS would not be a performer because the 23 foot 

 wingspan needs a 100 hp engine to climb and cruise decently.  With my 

 Stratus Subaru, the

 economy cruise is excellent and climb is very good, but the climb is 

 nowhere close to an HD with the same engine.

 

 Larry McFarland 601HDS at www.macsmachine.com

 

 Matt Ronics wrote:

 

> 

>

> Already having on-hand a C-85, I called Zenith about using it in the 

> XL.  In summary, I was advised that I probably wouldn't be pleased 

> with the performance.  At the same time, I was told that this would be 

> an excellent engine in a 601HD/S.

>

> Of note you are asking for "cruise speed" with the 80hp engine.  Note 

> that, generally speaking, it is climb performance, and not cruise, 

> that is effected more by changing cubes.   For example, using Van's 

> numbers for the RV-4, increasing the HP 17% will give you a 6% 

> improvement in cruise and a 25% improvement in climb. 

> Having thought this through in the past, I recall coming to the 

> conclusion that the XL with 85hp would perform like a C-150.  I spoke 

> with one 601HD (standard fat wing) owner with a C-85...his numbers 

> were very close to or less than those of a C-150.

>

>

jim.lanier(at)charter.net
Guest

Posted: Tue Apr 01, 2008 5:12 am Post subject: Zodiac XL Cruise Speed with 80HP

I chose to work the numbers to get an approximation of the cruise performance of 100hp vs 80hp engines.

 The Cd x A product was chosen to equal the Zenith website results for 100hp. If 100hp yields 134mph, then

 80hp would achieve 124.35mph. This will at least get you in the ballpark. There are so many variables, that it is difficult to

 get exact figures.

 

 The Cd x A product would be greater at reduced velocity due to increased angle of attack. The wing lift is greater at reduced velocity

 due to the lift vector angle deviating more aft of the normal force. The thrust vector angle also deviates slightly. 

 The weight of the 80hp engine would be (you would think) lower though.

 

 

 [img]cid:part1.06000300.04080300(at)charter.net[/img]

 

 

 [img]cid:part2.01090109.07030905(at)charter.net[/img]

 

 

 Jim

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ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Fri Apr 04, 2008 9:41 am Post subject: Re: Zodiac XL Cruise Speed with 80HP

That's an interesting equation. Do you have more info on it. Reminds me of the rule of thumb, 25% more power to go 10% faster.



 	  jim.lanier(at)charter.net wrote: 	
		  I chose to work the numbers to get an approximation of the cruise performance of 100hp vs 80hp engines.

 The Cd x A product was chosen to equal the Zenith website results for 100hp. If 100hp yields 134mph, then

 80hp would achieve 124.35mph. This will at least get you in the ballpark. There are so many variables, that it is difficult to

 get exact figures.

 

 The Cd x A product would be greater at reduced velocity due to increased angle of attack. The wing lift is greater at reduced velocity

 due to the lift vector angle deviating more aft of the normal force. The thrust vector angle also deviates slightly. 

 The weight of the 80hp engine would be (you would think) lower though.

 

 

 [img]cid:part1.06000300.04080300(at)charter.net[/img]

 

 

 [img]cid:part2.01090109.07030905(at)charter.net[/img]

 

 

 Jim

jim.lanier(at)charter.net
Guest

Posted: Fri Apr 04, 2008 12:10 pm Post subject: Zodiac XL Cruise Speed with 80HP

Hi Andy,

 

 Sure. Here it is...

 

 Fd = (1/2)(dens)(v^2)(A)(Cd)

 Pwr = (Fd)(v) or Pwr = (1/2)(dens)(v^3)(A)(Cd)

 

 

 dens = 1.293 kg/m^3 at 0°C and 1 atmosphere

 Fd = drag force in Newtons (kg m/sec^2)   (Isaac and I go way back..we used to go to different schools together  )

 v = velocity m/s

 A = cross sectional area in m^2

 Cd = drag coefficient 

 Pwr = power in watts (kg m^2/sec^3)

 

 [img]cid:part1.02060307.01030401(at)charter.net[/img]

 

 [img]cid:part2.07080208.03080203(at)charter.net[/img]

 

 I don't know what Cd is (or A for that matter), but they are a product in the formula. So although they may both be wrong, their product is OK.

 You could say that this is a normalized solution. 

 

 Note: You can convert the drag and power formulas to Engish units if you want, but I prefer to do everything in metric and convert afterwards. Note in the spreadsheet examples above

 that I converted Watts to HP after the equation was resolved.

 

 Jim

 

 

 

 

 

 

 

 ashontz wrote:  	  Quote: 	
		      	  Quote: 	
		  --> Zenith-List message posted by: "ashontz" <ashontz(at)nbme.org> (ashontz(at)nbme.org)



That's an interesting equation. Do you have more info on it. Reminds me of the rule of thumb, 25% more power to go 10% faster.

jim.lanier(at)charter.net wrote:

        	  Quote: 	
		  I chose to work the numbers to get an approximation of the cruise performance of 100hp vs 80hp engines.

 The Cd x A product was chosen to equal the Zenith website results for 100hp. If 100hp yields 134mph, then

 80hp would achieve 124.35mph. This will at least get you in the ballpark. There are so many variables, that it is difficult to

 get exact figures.

 

 The Cd x A product would be greater at reduced velocity due to increased angle of attack. The wing lift is greater at reduced velocity

 due to the lift vector angle deviating more aft of the normal force. The thrust vector angle also deviates slightly. 

 The weight of the 80hp engine would be (you would think) lower though.

 

 

 [img][url=cid:part1.06000300.04080300(at)charter.net]cid:part1.06000300.04080300(at)charter.net[/url][/img]

 

 

 [img][url=cid:part2.01090109.07030905(at)charter.net]cid:part2.01090109.07030905(at)charter.net[/url][/img]

 

 

 Jim

    	
   



--------

Andy Shontz

CH601XL - Corvair

www.mykitlog.com/ashontz





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=174819#174819

frankroskind(at)HOTMAIL.C
Guest

Posted: Fri Apr 04, 2008 12:48 pm Post subject: Zodiac XL Cruise Speed with 80HP

I don't know what is wrong with the calculatinos, but something would have to be.  If all the power were used to offset parasitic drag, then the drag increases with the square of velocity.  The ratio of velocities would then be the square root of the ratio of power, or (at)sqrt(80/100), using quattro pro, which is roughly89.44%, resuting in an 80 hp velocity of 119.85 mph if the 100 hp velocity were 134 mph.  The other main component of drag, induced drag, decreases with increased velocity but is small at velocities significantly above stall speed, so the actual 80 hp cruise speed would likely be a little less than 119 mph.

  	  Quote: 	
		    Date: Fri, 4 Apr 2008 16:06:05 -0500

From: jim.lanier(at)charter.net

To: zenith-list(at)matronics.com

Subject: Re: Re: Zodiac XL Cruise Speed with 80HP

 Hi Andy,

Sure. Here it is...

Fd = (1/2)(dens)(v^2)(A)(Cd)

Pwr = (Fd)(v) or Pwr = (1/2)(dens)(v^3)(A)(Cd)

dens = 1.293 kg/m^3 at 0°C and 1 atmosphere

Fd = drag force in Newtons (kg m/sec^2)   (Isaac and I go way back..we used to go to different schools together  )

v = velocity m/s

A = cross sectional area in m^2

Cd = drag coefficient 

Pwr = power in watts (kg m^2/sec^3)

[img]cid:part1.02060307.01030401(at)charter.net[/img]

[img]cid:part2.07080208.03080203(at)charter.net[/img]

I don't know what Cd is (or A for that matter), but they are a product in the formula. So although they may both be wrong, their product is OK.

You could say that this is a normalized solution. 

Note: You can convert the drag and power formulas to Engish units if you want, but I prefer to do everything in metric and convert afterwards. Note in the spreadsheet examples above

that I converted Watts to HP after the equation was resolved.

Jim

ashontz wrote:   	  Quote: 	
		   	  Quote: 	
		  --> Zenith-List message posted by: "ashontz" <ashontz(at)nbme.org> (ashontz(at)nbme.org)

That's an interesting equation. Do you have more info on it. Reminds me of the rule of thumb, 25% more power to go 10% faster.

jim.lanier(at)charter.net wrote:

   	  Quote: 	
		  I chose to work the numbers to get an approximation of the cruise performance of 100hp vs 80hp engines.

 The Cd x A product was chosen to equal the Zenith website results for 100hp. If 100hp yields 134mph, then

 80hp would achieve 124.35mph. This will at least get you in the ballpark. There are so many variables, that it is difficult to

 get exact figures.

 The Cd x A product would be greater at reduced velocity due to increased angle of attack. The wing lift is greater at reduced velocity

 due to the lift vector angle deviating more aft of the normal force. The thrust vector angle also deviates slightly. 

 The weight of the 80hp engine would be (you would think) lower though.

 [img]cid:part1.06000300.04080300(at)charter.net[/img]

 [img]cid:part2.01090109.07030905(at)charter.net[/img]

 Jim

--------

Andy Shontz

CH601XL - Corvair

www.mykitlog.com/ashontz

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=174819#174819

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ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Fri Apr 04, 2008 1:22 pm Post subject: Re: Zodiac XL Cruise Speed with 80HP

Thanks.



Actually, the 25% more power=10% faster is pretty accurate. Let's say the 80hp speed was 122, 100hp speed would then be 122 x 1.1 = 134.2mph. Scaling backwards, the ratio is .9090909090 on speed and a 20% reduction in power, 100hp down to 80hp.



Would that mean a 65hp VW could push an XL at 110mph? Maybe.



An old boat I used to have at one time had a 140hp Johnson on it, it did 50mph in that configuration. With a 70hp Evinrude, it did 36. That was a measured fact, the boat did in fact top out at 50 with a 140 on it, and it topped out at 36 with a 70hp on it.



140hp X .80 = 112hp x .8 = 89hp x .8 = 71.2hp

50mph x .909090 = 45.5mpg x .909090 = 41.3mph x .909090 = 37.5mph



Damn, those numbers are pretty close. Interesting isn't it.



At some point this would have to cease to be a linear? (logrythmic?) relationship though because I can't imagine a 601Xl going 80mph with a 33hp engine on it.  LOL And definitely no 60mph with a 16hp engine on it.



And definitely not 45mph with an 8hp engine on it. But for anyone who just barely wants to get off the ground and keep it local, you could try installing an 8hp Briggs and Stratton and report back how it worked out.

 	  frankroskind(at)HOTMAIL.C wrote: 	
		  I don't know what is wrong with the calculatinos, but something would have to be.  If all the power were used to offset parasitic drag, then the drag increases with the square of velocity.  The ratio of velocities would then be the square root of the ratio of power, or (at)sqrt(80/100), using quattro pro, which is roughly89.44%, resuting in an 80 hp velocity of 119.85 mph if the 100 hp velocity were 134 mph.  The other main component of drag, induced drag, decreases with increased velocity but is small at velocities significantly above stall speed, so the actual 80 hp cruise speed would likely be a little less than 119 mph.



  	  Quote: 	
		    Date: Fri, 4 Apr 2008 16:06:05 -0500

From: jim.lanier(at)charter.net

To: zenith-list(at)matronics.com

Subject: Re: Re: Zodiac XL Cruise Speed with 80HP



 Hi Andy,



Sure. Here it is...



Fd = (1/2)(dens)(v^2)(A)(Cd)

Pwr = (Fd)(v) or Pwr = (1/2)(dens)(v^3)(A)(Cd)

dens = 1.293 kg/m^3 at 0?C and 1 atmosphere

Fd = drag force in Newtons (kg m/sec^2)   (Isaac and I go way back..we used to go to different schools together  )

v = velocity m/s

A = cross sectional area in m^2

Cd = drag coefficient 

Pwr = power in watts (kg m^2/sec^3)



[img]cid:part1.02060307.01030401(at)charter.net[/img]



[img]cid:part2.07080208.03080203(at)charter.net[/img]



I don't know what Cd is (or A for that matter), but they are a product in the formula. So although they may both be wrong, their product is OK.

You could say that this is a normalized solution. 



Note: You can convert the drag and power formulas to Engish units if you want, but I prefer to do everything in metric and convert afterwards. Note in the spreadsheet examples above

that I converted Watts to HP after the equation was resolved.



Jim



ashontz wrote:   	  Quote: 	
		   	  Quote: 	
		  --> Zenith-List message posted by: "ashontz" <ashontz> (ashontz(at)nbme.org)



That's an interesting equation. Do you have more info on it. Reminds me of the rule of thumb, 25% more power to go 10% faster.

jim.lanier(at)charter.net wrote:

   	  Quote: 	
		  I chose to work the numbers to get an approximation of the cruise performance of 100hp vs 80hp engines.

 The Cd x A product was chosen to equal the Zenith website results for 100hp. If 100hp yields 134mph, then

 80hp would achieve 124.35mph. This will at least get you in the ballpark. There are so many variables, that it is difficult to

 get exact figures.

 

 The Cd x A product would be greater at reduced velocity due to increased angle of attack. The wing lift is greater at reduced velocity

 due to the lift vector angle deviating more aft of the normal force. The thrust vector angle also deviates slightly. 

 The weight of the 80hp engine would be (you would think) lower though.

 

 

 [img]cid:part1.06000300.04080300(at)charter.net[/img]

 

 

 [img]cid:part2.01090109.07030905(at)charter.net[/img]

 

 

 Jim

    	
--------

Andy Shontz

CH601XL - Corvair

www.mykitlog.com/ashontz





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=174819#174819



  	
	


	
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Last edited by ashontz on Fri Apr 04, 2008 1:29 pm; edited 2 times in total

jim.lanier(at)charter.net
Guest

Posted: Fri Apr 04, 2008 1:22 pm Post subject: Zodiac XL Cruise Speed with 80HP

jim.lanier(at)charter.net
Guest

Posted: Fri Apr 04, 2008 2:03 pm Post subject: Zodiac XL Cruise Speed with 80HP

Hi Frank,



Those formulas are correct and are standard . In my first post I noted 

some of the problems with the comparison dealing with vectors. One thing 

to note is that Cd changes with velocity (particularly close to mach). 

At the difference in these velocities the Cd change due to velocity is 

insignificant, but the Cd change due to attack angle may be significant. 

Drag increases with the square of velocity. Power requirement increases 

with the CUBE of velocity. Power =(Fd)(v) and since Fd included a 

square..it is now a cube.



Jim

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