Pre and Post Hull Fairing performance

<< First  < Prev   1   2   3   Next >  Last >> 
  • January 14, 2015 7:15 PM
    Message # 3200638
    Anonymous member (Administrator)

    Thanks to the efforts of Dave King - Pygmalion received the DLK hull fairing and a used 17" Max Prop in December. 

    Below are motoring only performance figures before and after the fairing. 

    Speed tests are averages between a course to the west then a reversed course to the east in the Alameda Estuary - winds very low in both cases.

    Speed is in knots - Beta 1505 38 HP with 1:2.5 transmission.

    11/15/14 Before Fairing 16 x 16 fixed   RPM KMeter   GPS SOG
     Off Idle 1000 2.75  3.15
      1500 4.25  4.75
     Cruising  2000 5.25  5.70
     Max Throttle  2750 6.30  6.75
           
     1/10/15 After Fairing 17" Maxprop 24 deg pitch      
     Off Idle 1000 3.60 3.55
    1500 5.10 4.85
     Cruising  2000  6.00  5.95
     Max Throttle  2500  6.75  6.55
     Wide Open Throttle - Neutral  3200    







    \


    Looking at the results the Max Throttle at 2500 rpm indicates an over pitched prop.  Fixing the pitch will have to wait until the next haul out in a few years.  

    I also noticed that the "prop" noise seemed louder then the 3 blade fixed.  

    I suspect that the new 17" prop (verses 16" fixed prop) plus fairing resulted with the blade tips being close to the hull and is a cause of increased blade noise.  

    I also suspect that the blade design for the Max prop is noisier then fixed blade - comments from others who have switched? 

    Last modified: January 18, 2015 1:22 PM | Anonymous member (Administrator)
  • January 14, 2015 7:35 PM
    Reply # 3200653 on 3200638
    Anonymous member (Administrator)

    I also took video while the boat was circled.  Forward at 2000 RPM took 40 seconds with tiller hard over.  

    Reverse circles at 1000 RPM with tiller hard over and also about 1/2 over to the stb and port at an average of 85 seconds.  

      

    What I did notice is that in reverse a hard over tiller or 1/2 over tiller didn't seem to chante the time it took to complete one circle...  I suspect that putting the tiller hard over is more like a brake then actually turning any sharper.

    Also the 1/2 over tiller reduced the load on the tiller and pilot a lot.

    Last modified: January 18, 2015 1:04 PM | Anonymous member (Administrator)
  • January 19, 2015 5:20 PM
    Reply # 3204839 on 3200638
    Jay Bietz wrote:

    Thanks to the efforts of Dave King - Pygmalion received the DLK hull fairing and a used 17" Max Prop in December. 

    Below are motoring only performance figures before and after the fairing. 

    Speed tests are averages between a course to the west then a reversed course to the east in the Alameda Estuary - winds very low in both cases.

    Speed is in knots - Beta 1505 38 HP with 1:2.5 transmission.

    11/15/14 Before Fairing 16 x 16 fixed   RPM KMeter   GPS SOG
     Off Idle 1000 2.75  3.15
      1500 4.25  4.75
     Cruising  2000 5.25  5.70
     Max Throttle  2750 6.30  6.75
           
     1/10/15 After Fairing 17" Maxprop 24 deg pitch      
     Off Idle 1000 3.60 3.55

    1500 5.10 4.85
     Cruising  2000  6.00  5.95
     Max Throttle  2500  6.75  6.55
     Wide Open Throttle - Neutral  3200    







    \


    Looking at the results the Max Throttle at 2500 rpm indicates an over pitched prop.  Fixing the pitch will have to wait until the next haul out in a few years.  

    I also noticed that the "prop" noise seemed louder then the 3 blade fixed.  

    I suspect that the new 17" prop (verses 16" fixed prop) plus fairing resulted with the blade tips being close to the hull and is a cause of increased blade noise.  

    I also suspect that the blade design for the Max prop is noisier then fixed blade - comments from others who have switched? 


    Jay,

    You need to reduce the pitch on the prop.  Dividing the in-gear RPM by the out-of-gear RPM, you get 78%.  You had 86% with the fixed prop, which is more in the 85% to 90% range, where it should be.  You should reduce the pitch on the Maxprop to the 22 degree setting, and that should be about right.


  • January 20, 2015 7:20 PM
    Reply # 3205951 on 3200638
    Anonymous member (Administrator)

    Thanks Bud - next haul out in a few years - I'll be setting back to 22 Deg... 

  • January 20, 2015 7:31 PM
    Reply # 3205955 on 3200638

    I thought the hull fairing was for sailing performance


    The max prop is definitely noisier than a fixed prop. I sail and care not

    Last modified: January 20, 2015 7:45 PM | Anonymous member
  • January 21, 2015 7:35 PM
    Reply # 3206802 on 3200638
    Anonymous member (Administrator)

    Gary:  The performance tests under power is to show that I didn't lose performance under power with the hull fairing... 

    I'm down to one more project to complete -- and I'll be out on the bay and trying out the sailing with the fairing. 

    I'm encouraged to know that the max prop is normally noisier than fixed prop.  

    Jay

    Last modified: January 21, 2015 7:37 PM | Anonymous member (Administrator)
  • January 22, 2015 12:22 PM
    Reply # 3207986 on 3200638

     

     

     

    Jay, we didn’t do the analysis you did but think the results are similar.  Last year we had to motor form San Francisco to San Diego as there wasn’t a breath of air the entire month. This gave us a lot of motor time to ponder and both of us concluded that our motoring was about 150 RPM less to maintain the same motor speed. No wind was a real bummer as we did the fairing so we could sail a lot more on our next trip to Mexico, notorious for light winds.

    As for sailing, the first time we sailed after the fairing was across San Francisco in front of the Golden Gate.  True wind was 4.5 Knts on a broad reach and Worldwind was doing a steady 4.1 knts on the GPS and knot meter at slack tide.  We had a Kern super Yankee, staysail and full batten Kern Mainsail up.  We both were amazed with the improvement the fairing made. Normally we would have had a drifter up. We sailed to San Leandro for the WS rendezvous in conditions I would normally have motored in.  Duke on Amable was along with us, having the same results.

    Your Max prop will sound different as any change in the prop would. If you call PSE they can tell you exactly what it should be set at. I added a drive saver when we had a fixed prop, relocating it an inch back and it sounded different.  When we first put our Max prop on we thought we had set it to high as the motor seemed to run a little warmer. I called PSE and they said I was actually set to low.  We changed it and the difference was more than noticeable.  Lastly the Max Prop is supposedly just a tiny bit less efficient than a good fixed prop, but we couldn’t tell.

    Jim

  • January 22, 2015 5:30 PM
    Reply # 3208167 on 3200638
    Anonymous member (Administrator)

    Jim:  Thanks for the info... looking forward to the performance under sail.  I was worried that the different sounds indicated something was not right -- but after 70 NM trip and hearing that the different sound is normal - that helps. 

    Looking at the feathered position of the prop below... I don't think I have an inch to move it back. 


    Jay

    Last modified: January 22, 2015 5:33 PM | Anonymous member (Administrator)
  • January 22, 2015 7:51 PM
    Reply # 3208249 on 3200638

     

    Most of your noise is coming from the tip clearance.  I wish I still remembered the formula, but I can tell that you're to close even though it won't cause any harm. Our photo doesn't show the clearance real well but I think you can tell it's more than yours and I remember it still wasn't what it should have been. I had cut the hull and rudder both quit a bit to get as much clearance as possible. This was done ten years before the fairing.

    Jim

     

     

  • February 02, 2015 11:11 AM
    Reply # 3216000 on 3200638

     

     

    I just ran accross these pics showing the first time we sailed after the mods.  Winds were light, fluky and mostly a broad reach.  Although sometimes it momentarily shifted astern. This was crossing San Francisco Bay on a slack tide.

    Our next good test was San Diego to Ensenada.  We logged 67 nautical miles in just over 13 hrs. averaging almost exactly 5 knts. This in wind speeds of 6-8 knts. sometimes a little less. 

    This is why we did the mods, not to race but to extend our sailing ability while cruising. Our only regret is we waited so many years to do it. It pains us to think of the times we would have sailed in light winds in Mexico if we would have just had the added performance.  If we knew this in the beginning it would have been done on our very first haul out.

     

    J&J "Worldwind" 

      

    Last modified: February 02, 2015 11:25 AM | Anonymous member
<< First  < Prev   1   2   3   Next >  Last >> 
Powered by Wild Apricot Membership Software