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Ultrastar speeds

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Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Tue Apr 08, 2008 6:24 pm Post subject: Ultrastar speeds

Ya gotta love a plane where you can leave work at 4:30, drive to an airport 

1/2 hour away (with a stop at home to pick up a forgotten toolbox), get 

there, unfold the wings, then completely remove the wings, mess with some 

stuff, put them back on, finish setting up and preflight, and still get in 

a 35 minute flight and have everything folded and back in the trailer by 

sunset!  But I digress...



What kind of speeds do people see with the US?  Like best climb and cruise 

(at what rpm)?



I think I finally have my plane rigged right.  As mentioned in the 

discussion of the leading edge joiner slip tube, my wings didn't seem to be 

quite aligned right.  Last weekend, I noticed that one of the holes in the 

RH wing universal was not on the centerline of the square tube, but about 

1/4" off.  That orientation just meant that the right wing was 1/4" farther 

back, which is still within the range of the rear spar attach point.  The 

crossmember that the universals mount to is also not quite straight on my 

plane, whether due to old damage (the plane was crashed and rebuilt many 

years ago) or welding warpage I don't know... but the plane's been flying a 

long time that way through several previous owners.  Today I took the wings 

off, and swapped the universals, using the offset to raise the front of the 

left wing (compensating for the bent tube).  Now the leading edge joiner 

tube slips over both easily with no stress, and the plane flies hands off 

at 40 mph.  A cruise around the local area, a few takeoffs and landings... 

life is good!



I also cross checked the ASI with a borrowed Hall meter, and it's right on 

at 40 mph... I get 40 mph level flight at 5000 rpm.



What rpm and speed do other US pilots cruise at?



I do intend to temporarily fit a Tiny Tach to cross check the combo 

tach/EGT on the plane, and also check the prop rpm with an optical tach 

(any old R/C'ers remember the old Heathkit "Thumb" Tach?)  Should be OK 

though, as I get 6500 rpm static.



And what about the best climb speed?  Best climb (550-600 fpm) seems to be 

only a bit over stall speed (the stall starts at 30 mph and the nose drops 

a bit below that).



-Dana

--

  In general, liberalism consists of A & B getting together to see what 

they can make C do for poor old D.

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Wed Apr 09, 2008 11:58 am Post subject: Re: Ultrastar speeds

While I was testing my engine Cuyuna UL-202 I was initially getting up to 6500 rpm that would settle down mysteriously to 6200 rpm.



I discovered that it was due to reduction belt slippage.



Once I tightened the belts a bit more I could only get 6000 rpm.



There was no indication of slipping other than me noticing the initially high rpms that would settle slightly and the fact that they were higher than the manual stated. 



You might want to check your belt tightness as a slipping belt is going to cause it to wear through prematurely.



I guess the prop your using? might also account for the difference instead of the belts.



Mine is a 50x30 2 Blade wood Ritz prop.



I have noticed that the sand and small gravel has really tortured my wood prop.



I wonder if a composite prop would resist that better?

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Wed Apr 09, 2008 2:50 pm Post subject: Ultrastar speeds

At 03:58 PM 4/9/2008, jb92563 wrote:



 	  Quote: 	
		  You might want to check your belt tightness as a slipping belt is going to 

cause it to wear through prematurely.


	


That's on tomorrow's agenda, belt check and prop rpm with the optical tach.



 	  Quote: 	
		  I have noticed that the sand and small gravel has really tortured my wood 

prop.



I wonder if a composite prop would resist that better?


	


I dunno, wood nicks easily but it's all small damage, which can be 

repaired.  Damage a composite prop and if there's internal damage it could 

fail.  I witnessed Todd Thompson (he used to post on this list) crash his 

MKIII when his Powerfin prop exploded on takeoff after being repaired... he 

had a lot of small dings from rocks thrown up by the wheels, so it's not 

unique to the Ultrastar.



I'm thinking the best might be a wood prop with inset polyurethane leading 

edges, but I don't know if that can be done on an old prop.



On the PPGs we put polyurethane tape on the leading edges to protect 

them.  Gravel of any size will go through the tape but it does a good job 

of protecting the prop against small sand particles.  I've been meaning to 

add it to the US prop but I never get around to it; I fly off pavement so 

it's not that urgent.



-Dana

--

  Dyslexics Untie!

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Apr 10, 2008 6:17 pm Post subject: Ultrastar speeds

At 03:58 PM 4/9/2008, jb92563 wrote:



 	  Quote: 	
		  While I was testing my engine Cuyuna UL-202 I was initially getting up to 

6500 rpm that would settle down mysteriously to 6200 rpm.



I discovered that it was due to reduction belt slippage.



Once I tightened the belts a bit more I could only get 6000 rpm.



There was no indication of slipping other than me noticing the initially 

high rpms that would settle slightly and the fact that they were higher 

than the manual stated.



You might want to check your belt tightness as a slipping belt is going to 

cause it to wear through prematurely.



I guess the prop your using? might also account for the difference instead 

of the belts.


	


Flew again tonight.  I don't think it's slipping.  Static rpm is indeed 

6500, which is correct according to the Cuuyna manual, if not the US manual 

(which says 6200-6300).  Anybody know what the redrive ratio is?  At 3000 

engine rpm I have 1400 prop rpm which is 2.14:1; same at 6000/2800; at 6500 

prop is 3000 which works out to 2.17, I think the difference is within the 

accuracy of my old analog Heathkit optical tach.  I didn't fly out of the 

traffic pattern tonight so I didn't have a chance to let it settle down at 

cruise at other rpm's.



I _do_ get a cyclic humming that others have mentioned, a kind of 

mmmm...mmmmm...mmmmm, about a 1 second period, almost like a twin with a 

"beat" when the engines aren't quite synched.  Could be an interplay 

between exhaust pulses and an odd prop ratio.



-Dana

--

  Sex in a Volkswagen = Farfergnookie.

jbhart(at)onlyinternet.ne
Guest

Posted: Fri Apr 11, 2008 3:32 am Post subject: Ultrastar speeds

At 10:09 PM 4/10/08 -0400, you wrote:

 	  Quote: 	
		  

I _do_ get a cyclic humming that others have mentioned, a kind of 

mmmm...mmmmm...mmmmm, about a 1 second period, almost like a twin with a 

"beat" when the engines aren't quite synched.  Could be an interplay 

between exhaust pulses and an odd prop ratio.




	


Dana



Could be it is your round wing lift struts strumming.



Jack B. Hart FF004

Winchester, IN

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Fri Apr 11, 2008 8:44 am Post subject: Ultrastar speeds

At 08:30 AM 4/11/2008, Jack B. Hart wrote:

 	  Quote: 	
		  Could be it is your round wing lift struts strumming.


	


That's a thought... I'll reach back and grasp them in flight next time, see 

if that's it.



I've considered fairing them at some point like you did.  A buddy of mine 

has a CNC hot wire cutter for R/C wings, which should make short work of 

shaping the fairings.  Did you actually see any speed or economy 

improvements with the fairings?



-Dana

--

  Duelling is legal in Paraguay as long as both parties are registered 

blood donors.

Possums

Joined: 03 Nov 2007
Posts: 247

Posted: Fri Apr 11, 2008 11:08 am Post subject: Ultrastar speeds

At 12:37 PM 4/11/2008, you wrote:

 	  Quote: 	
		  



At 08:30 AM 4/11/2008, Jack B. Hart wrote:

>Could be it is your round wing lift struts strumming.



That's a thought... I'll reach back and grasp them in flight next 

time, see if that's it.


	


You can see them - kinda a blur when they get going good & that humming noise.



 	  Quote: 	
		  I've considered fairing them at some point like you did.  A buddy of 

mine has a CNC hot wire cutter for R/C wings, which should make 

short work of shaping the fairings.  Did you actually see any speed 

or economy improvements with the fairings?


	


You would pick up at least 4 MPH with fairings and probably more.



 	  Quote: 	
		  -Dana

_________________
Possum

jbhart(at)onlyinternet.ne
Guest

Posted: Tue Apr 15, 2008 9:15 am Post subject: Ultrastar speeds

At 12:37 PM 4/11/08 -0400, you wrote:

 	  Quote: 	
		  



I've considered fairing them at some point like you did.  A buddy of mine 

has a CNC hot wire cutter for R/C wings, which should make short work of 

shaping the fairings.  Did you actually see any speed or economy 

improvements with the fairings?




	


Dana,



I have not been concerned about top speed.  I don't like to fly much faster 

than 55 mphi with my head sticking out in the air stream.  What I am 

interested in is reduced fuel burn rates and increased range.



Jack B. Hart FF004

Winchester, IN

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Tue Apr 15, 2008 1:12 pm Post subject: Ultrastar speeds

At 02:14 PM 4/15/2008, Jack B. Hart wrote:



 	  Quote: 	
		  I have not been concerned about top speed.  I don't like to fly much faster

than 55 mphi with my head sticking out in the air stream.  What I am

interested in is reduced fuel burn rates and increased range.


	


Same here... though I'd like to get a tad more cruise speed; 5000 rpm only 

gives me 40 mph , the US is pretty draggy.



-Dana

--

  Friends help you move.  *Real* friends help you move bodies.

John Hauck

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

Posted: Tue Apr 15, 2008 1:54 pm Post subject: Ultrastar speeds

 	  Quote: 	
		   Same here... though I'd like to get a tad more cruise speed; 5000 rpm only 

 gives me 40 mph , the US is pretty draggy.



 -Dana


	




Dana:



All the two strokes I flew used a standard tuned expansion system for 

exhaust.  That was the Cuyuna and Rotax two strokes.



My preferred cruise rpm was 5,800 for both brands of engines.  That's about 

75% power.  IIRC max continuos rpm was 6,500 rpm for both brands.  These 

engines were designed to operate continuously up to and including 6,500 rpm.



Both brands seemed to "come up on the pipe" at 5300 to 5500 rpm.  At this 

rpm band, the engine would not want to settle down, requiring constant 

throttle changes to attempt to maintain constant rpm.  Above 5500 the 

engines smooths out, gets a crisp feel, as they start producing power in 

their tuned power range.



I am a firm believer in running engines hard and making them work in their 

designed power range.  I think this keeps them cleaner and they will last 

longer.



Flying around bogged down, producing carbon and loading the crankcase with 

oil residue, IMHO is much harder on the two stroke.



At 5800 rpm my US cruised 65 mph with a 50X30 Jim Culver two blade wooden 

prop.  My FS cruised the same with a 40 hp 447 and a 60X30 Jim Culver two 

blade wooden prop.



Both aircraft flew quite well at slow speeds, stalling at 25 mph.  However, 

like their big cousin, the MKIII, they had a sweet spot that was quicker and 

much more comfortable to fly and play.



john h

mkIII

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

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Tue Apr 15, 2008 2:37 pm Post subject: Ultrastar speeds

At 05:52 PM 4/15/2008, John Hauck wrote:



 	  Quote: 	
		  My preferred cruise rpm was 5,800 for both brands of engines.  That's 

about 75% power.  IIRC max continuos rpm was 6,500 rpm for both 

brands.  These engines were designed to operate continuously up to and 

including 6,500 rpm.



Both brands seemed to "come up on the pipe" at 5300 to 5500 rpm...

At 5800 rpm my US cruised 65 mph with a 50X30 Jim Culver two blade wooden 

prop...


	


Thanks John, I'll have to play some more.  I had been thinking 5800 seemed 

kind of high, what with the Ultrastar manual talking about 4500 being a 

"nice comfortable cruise."  90% of my flying so far has been in the pattern 

(I want to get more comfortable with being able to always put it down where 

I want to before venturing farther afield), so I haven't had much time to 

experiment.  Seems unlikely I'll see 65, though, if 5000's only giving me 

40 (where my ASI matches a borrowed Hall ASI).



Do you recall what kind of fuel burn you got at 5800?  Or what speeds you 

used for climb and approach?



-Dana``



--

  We all know that engineers love to play with expensive toys.

Especially when someone else is paying for them.

John Hauck

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

Posted: Tue Apr 15, 2008 3:15 pm Post subject: Ultrastar speeds

> Do you recall what kind of fuel burn you got at 5800?  Or what speeds you

 	  Quote: 	
		   used for climb and approach?



 -Dana``


	




Dana:



Thinking it was around 3.0 gph for the 35 hp Cuyuna ULII02 and 3.5 to 3.75 

gph for the 40 hp 447.



I climbed at whatever felt good and shot my approaches at about 40 mph.



john h

mkIII

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

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Tue Apr 15, 2008 4:18 pm Post subject: Ultrastar speeds

At 07:12 PM 4/15/2008, John Hauck wrote:



 	  Quote: 	
		  I climbed at whatever felt good and shot my approaches at about 40 mph.


	


Thanks, that's about where I am right now.  35 "feels good" on climb and 40 

feels right on approach.



It's so much fun to see my airplane skills slowly returning... the PPG's 

which I've been flying for the past 7 years are a blast, too, but it's a 

completely different skill set.



-Dana



--

  There are 3 kinds of people: those who can count & those who can't.

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