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GSC numbers : Re Propellers

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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Oct 26, 2006 9:14 am Post subject: GSC numbers : Re Propellers

Ok got about an hour in flying a GSC  today so  far . 

  

 Take off same distance approx  200 feet or  so

 Climb about the same 12 to 1300 fpm   

 Cruise about 2 mph slower  at 86 mph now   

  

 Nearest station 

             Loc.     Time (EDT)     Cat.     Vis.     Wx.     Sky Cover     Wind     Temp.     Dew Pt.     Altim.     Hum.     D. Alt.     Remarks        CYXU     12:00 PM     VFR     15 sm           Few 3000', Broken 4600'     Calm     42.8°F     30.2°F     30.25"     61%     -235'     Cu1sc6; Sea level pressure 30.27" Hg

  

 I think I can pitch a little coarser  on the  gsc about 1/4 degree more and get the cruise the same .

 Reason I say this is because the EGT are a tad  higher than I had with the WARP .  And I repitched once already from 16 to  16.5 degrees on the GSC measured at  .69 % radii 

  

 Over all  WARP and GSC are pretty close to be  about the same performance.  Both totally acceptable. 

  

 Lowell -  I did not try the  5/16" bolt  in 8mm  hole-- sorry  I forgot. 

  

 Dave 

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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Oct 26, 2006 9:16 am Post subject: GSC numbers : Re Propellers

Ok got about an hour in flying a GSC  today so  far . 

  

 Take off same distance approx  200 feet or  so

 Climb about the same 12 to 1300 fpm   

 Cruise about 2 mph slower  at 86 mph now   

  

 Nearest station 

             Loc.     Time (EDT)     Cat.     Vis.     Wx.     Sky Cover     Wind     Temp.     Dew Pt.     Altim.     Hum.     D. Alt.     Remarks        CYXU     12:00 PM     VFR     15 sm           Few 3000', Broken 4600'     Calm     42.8°F     30.2°F     30.25"     61%     -235'     Cu1sc6; Sea level pressure 30.27" Hg

  

 I think I can pitch a little coarser  on the  gsc about 1/4 degree more and get the cruise the same .

 Reason I say this is because the EGT are a tad  higher than I had with the WARP .  And I repitched once already from 16 to  16.5 degrees on the GSC measured at  .69 % radii 

  

 Over all  WARP and GSC are pretty close to be  about the same performance.  Both totally acceptable. 

  

 Lowell -  I did not try the  5/16" bolt  in 8mm  hole-- sorry  I forgot. 

  

 Dave 

 [quote]   ---

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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Oct 26, 2006 9:22 am Post subject: GSC numbers : Re Propellers

Ok got about an hour in flying a GSC  today so  far . 

  

 Take off same distance approx  200 feet or  so

 Climb about the same 12 to 1300 fpm   

 Cruise about 2 mph slower  at 86 mph now   

  

 Nearest station 

             Loc.     Time (EDT)     Cat.     Vis.     Wx.     Sky Cover     Wind     Temp.     Dew Pt.     Altim.     Hum.     D. Alt.     Remarks        CYXU     12:00 PM     VFR     15 sm           Few 3000', Broken 4600'     Calm     42.8°F     30.2°F     30.25"     61%     -235'     Cu1sc6; Sea level pressure 30.27" Hg

  

 I think I can pitch a little coarser  on the  gsc about 1/4 degree more and get the cruise the same .

 Reason I say this is because the EGT are a tad  higher than I had with the WARP .  And I repitched once already from 16 to  16.5 degrees on the GSC measured at  .69 % radii 

  

 Over all  WARP and GSC are pretty close to be  about the same performance.  Both totally acceptable. 

  

 Lowell -  I did not try the  5/16" bolt  in 8mm  hole-- sorry  I forgot. 

  

 Dave 

 [quote]   ---

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dosmythe(at)cox.net
Guest

Posted: Thu Oct 26, 2006 11:36 am Post subject: GSC numbers : Re Propellers

Dave,

     Without repitching, what RPM do  you get in level flight with "full throttle"?  

  

 Don Smythe

 [quote]   I think I can pitch a little coarser  on the    gsc about 1/4 degree more and get the cruise the same .

   Reason I say this is because the EGT are a tad    higher than I had with the WARP .  And I repitched once already from 16    to 16.5 degrees on the GSC measured at  .69 % radii 

    

[b]

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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Oct 26, 2006 2:06 pm Post subject: GSC numbers : Re Propellers

Well Don first run at 16 degree I was getting a bit over 6250 rpm static.

WOT  7050 to 7100

Added 1/2 degree  and still about 6150  to 6200 static and 6950 wot .

I  just flew to 1.5 hours horsing around and it seems not bad really.

Decent performance all round but I think another 1/2 degree would do it.

But we got colder wx coming and  snow soon plus my plugs at about 60 hours

and I  have to pull cowl off soon so I think I reptich then again.  Who

know  I might repitch tomorrow.



Also if you got multiple mails from me today,  my outlook express is

sending everyone extra mails for some reason ( maybe early xmas gifts ? )

and I might have to do a format of it soon.  So if I don't rely to quick 

you will know I melted this pc.   

Dave



PS  I am sending this from my webmail  so it should just arrive once   : )



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propellerdesign(at)tele2.
Guest

Posted: Fri Oct 27, 2006 12:33 am Post subject: GSC numbers : Re Propellers

Propeller

  

 16 deg at 69% is 42,2" pitch.

 16,5 is 43,66"

 17 is 45,0"

  

 16 deg at 75% is 45,9"

 16,5 is 47,5"

  

 What the pitch is at 75% on the GSC don't have to  be, or more exact isn't the same as on 69% (depends on the blade twist and the  angle)

  

 Normally a propeller don't have true helix, meaning  the pitch isn't the same along the whole blade, if the prop was sitting an a  long shaft 10-20 feet ahead of the fuselage it might be ok, but at the nose the  air is slowed down (pushed forward) by the fuselage, gear, wings ...) this make  a propeller with less pitch near the hub better, on "normal" propellers the  thicker airfoil near the hub also work better at smaller angles, and the  opposite, the thinner blade near the tip work better at higher angles. (angles  relative to the air)

  

 Aspect Ratio.

 Why is the warp doing so good? even with the wide  tips on the standard blade.

 Normally a propeller have a AR of 6 or 6,66 on an 2  bladed prop, the Warp is around AR 6 on 3 blades, meaning it would be AR 9 on 2  blade, a rather high aspect ratio.

 We all know that a glider plane with AR 20-25 have  better performance L/D then a plane with a AR of 6-7, same on propellers, the  prop with AR 6 on 3 blade will have thinner blade in mm or fraction of inch,  then a 2 blade with AR 6 if the airfoil(s) have the same percent thickness, and  the losses at the narrower tip and blade is less with high AR. The 3 blade will  have less diameter then the 2 blade with same blade, this also reduce the high  drag from the higher Mach nr on the 2 blade.

 Note that a 3 blade with AR 6 will have same  diameter as an 2 blade with AR 6.

  

 This may be the case with the Powerfin F model, it  looks like it is wider then the Warp and GSC, this force it to have shorter  blades to come to its optimum.

 The pitch distribution maybe isn't optimal either.  (I don't know)

  

 Stuart at Powerfin say that it is not perfect to  have just a few models and cut the length to perform, it might be so that the F  model isn't designed for this speed/RPM/diameter VnD but better blade will  come.

  

 >The last  few years I have been designing a manufacturing process that enables me to make  drawings and toolpaths for molds very quickly with CAD/CAM. Just having a few  blades and cutting them down to size is not a very good way to get efficiency  when the main factors in efficieny seem to be proper lift distrubution and  advance ratio to achieve the correct alpha angles. Since the optimal design for  each application is unique, it is in my interest to figure out how to make molds  and prototypes quickly. That’s been my main focus for a number of years.<  Stuart.

  

 Tests.

  

 To make accurate tests, following test will be interesting, Take  off distance (difficult to measure exact) time to take off might be better,  but wind make a lot differences.

 climb speed say at 60 MPH timing  with the clock the climb from say 1000 to 2000 feet starting at 500 keeping  the speed constant. feet AGL that is so we don't hit any Sitka  spruce's.

  

 cruise speed at say 5800 and 6000 but this mean the prop's have to  be adjusted to exact the same WOT RPM others the cruise RPM will represent  different HP's

 and then WOT speed, all at same density alt. this have to be made  same day on a calm day. (days are short this time of the  year)

  

 there is other aspects too, like vibrations and  wear.

  

 would be interesting to test the taper Warp and the standard on  the same airplane/same day also.

  

 Jan

 www.jcpropellerdesign.com

  

  

  

  

  

  

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lcfitt(at)sbcglobal.net
Guest

Posted: Fri Oct 27, 2006 11:10 am Post subject: GSC numbers : Re Propellers

Jan,



I've always thought one issue with the Powerfin and the round cowl Kitfox is 

that the thickest part of the blade is just a fraction of an inch from the 

blunt end of the ring cowl.  I think this is one issue with the Jabiru also. 

It usually will use a shorter prop to get the RPMs in the proper tip speed 

range and that leaves the bulk of the prop battling the cowl.



This doesn't seem to be a problem with the more streamlined Sonex, etc.



The Warp prop on my Model IV has a longer neck at the root and the widest 

part of the blade begins right where the cowl face rounds to the cowl side 

very little of the prop is blanketed by the cowl.



Lowell

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