Pre and Post Hull Fairing performance

  • February 03, 2015 8:53 AM
    Reply # 3216818 on 3200638

    Jim and Jay,

    Jim indicates real performance improvements from fairing and switching to the Max-Prop.

    I wish we knew how much of the performance improvement was from the fairing, and how much from the Max-Prop. Were you switching from a 3 bladed prop?

    The reason I ask is that with my Max-Prop I get very similar performance under sail as you do, and Pablo has not had the fairing done,

    Last modified: February 03, 2015 8:57 AM | Anonymous member
  • February 03, 2015 10:45 AM
    Reply # 3216933 on 3200638

    Steve, Dave King could answer better that than I can, But the major improvement came from the fairing.  We've had a Max prop for 12 years and it helped a little, about 1/2 knot at lower speeds as Dave had told me it would. In the past we would have motored instead of sailing @ 2knts. in four knots of True wind speed. This was with standard sails.  We had  up the staysail, Kern super Yankee and Kern full batten main, no drifter or spinnaker. It should also take off about five knots of wind speed to hit hull speed.  This is with a fully loaded cruising boat. We're not the best sailors out there and only have @20,000 miles under the keel, many Westsailors have ten times that, but it's enough that we could tell that it was a tremendous difference. 

    Actually the first time we sailed we were trying to get to the Westsail rendezvous. We left Sausalito seeing four knots of wind, we started to motor but then decided to throw up sails. We first though our instruments were incorrect until we checked the speed against the GPS and then realized it was the fairing making the difference.

    Maybe Gary Burton can add to the discussion as he has done the fairing and races.

    Jim  

  • February 03, 2015 11:39 AM
    Reply # 3216973 on 3200638

    Steve, can you tell us a little more about Pablo and the conditions at the time? What was the sail configuration, sea state, and state of Pablos bottom? Was this speed through the water or SOG.

    From my own experience, the more fairing tweaks and more time I put into bottom prep, the faster my boat goes. The fairing was a substantial improvement along with the maxprop, and further improvement after last haul out and more fairing and good bottom paint and finishing

  • February 05, 2015 9:49 AM
    Reply # 3218528 on 3200638

    Okay - Let's see - Sail configuration was Super Yankee Jib, Staysail Genoa, full main (not full battened) Pablo's bottom was clean but not recently painted. Sea state very calm. With 10 -12 Knots of steady wind on a beam reach we were running 5.5 to 6 knots SOG (measured in one direction only).

    At a later time with the Drifter/Reacher and reefed main In 10 knots of wind,we went right to 7 knots on a beam reach! 


    Last modified: February 05, 2015 9:58 AM | Anonymous member
  • February 05, 2015 12:08 PM
    Reply # 3218651 on 3200638
    Deleted user

    I wish I had some better data, but what we do have is direct comparison sailing with (racing :)) Saraband:

    In 2011 we sailed from Portland up to the PNW Rondy with Saraband. We already had a Max Prop but no rudder fairing. Although we had no trouble staying with Saraband while motoring, she walked away from us in all sailing conditions. Our bottom was clean. In 2013 we helped Dave King do our rudder fairing. We could tell Konami sailed better, especially in light air. Last summer we sailed up to the San Juans (we missed the Rondy). We met up with Dave and Saraband and sailed back to Portland together. We are now able to keep up with Saraband most of the time.Saraband on the Columbia

    --John

    Last modified: February 05, 2015 4:07 PM | Deleted user
  • February 05, 2015 3:42 PM
    Reply # 3218786 on 3200638
    Deleted user

    In addition to the sail configuration and sail speed, I definitely experience smoother tacking  and the boat maintains speed through the tack, even in the currents.  ~Diane

  • February 06, 2015 1:31 PM
    Reply # 3219627 on 3216818
    Anonymous member (Administrator)
     Were you switching from a 3 bladed prop?

    The reason I ask is that with my Max-Prop I get very similar performance under sail as you do, and Pablo has not had the fairing done,

    Steve: yes the previous prop is a 16x16 fixed... Still no sailing - hopefully Presidents day weekend.. 

    Jay

  • February 07, 2015 11:57 AM
    Reply # 3220064 on 3200638

     

     

    Hey Steve, we were in Moss landing the other day, dinner at Phil’s, and saw a WS with burgundy canvas but the name didn’t look like Pablo. 

    It looks like Pablo sails real well but I don’t think we’re comparing apples to oranges. Your speed is SOG and mine is STW which is what the boat is doing in the water, without the help/hindrance of current.  The point is the fairing will double your low wind speed performance which I consider a weak point for the Westsail.  It’s hard to overestimate the drag created by the gap in hull/rudder.  You can see in the photos we’re sailing at near wind speed in light air conditions, something we greatly needed in Mexico were you usually get only light air if any at all, at least that is what we experienced.  We wouldn’t need a drifter at 10-12 knots of wind speed, actually at 12 knots we would be at or near hull speed with working sails.  Once you get 12-15 knots of wind speed the fairing gets less important.  But we loath to run our motor so light air performance is real important to us. 

    Like Gary we’ve found everything done like new Kern sails and Maxi Prop made a difference but noting as much effect as the fairing.  If we were starting out knowing what we know now, the fairing would be done on the first haul out.

    Jim

      

     

  • February 07, 2015 8:15 PM
    Reply # 3220248 on 3200638

    Jim, Everything you said makes perfect sense.. Especially the apples and oranges part.

    That W32 you saw is the newest one in Moss Landing Harbor. I have not yet met the owners. The other 3 of us are quite close togther on C and D docks.

  • February 08, 2015 10:38 PM
    Reply # 3220940 on 3200638

    To anyone still interested, the following are examples of performance gains relevant to this thread.  Some examples and stories have already been mentioned on this thread:

    1)  After the fairing, BUT, using the exact propulsion system unchanged, a .6k gain was realized at the top end motoring, on Saraband..  Worldwind indicated a 150 rpm drop for an equivalent boat speed.  This equals approximately .3k increase at normal motoring rpm.  Thanks for that data Jim.

    2)  A doubling of the sailing speed at the lowest wind ranges.  An example:  Six W-32's all sailing in close proximity at 1.5k to 2k, in very light winds.  A 7th W-32 lapped all the other 6 in one lap, as it averaged 3k to 4k.  Bud T. was on one of the 6 W-32"s as was Ladonna Buback, past editor of Latitude 38, and her husband Rob on another.  At least 30 westsailors witnessed this event.

    3)  In the above story, all 6 of the W-32's were using Drifters or Genoas.  The 7th W-32 was using the small working Jib.

    4)  The performance gain of the fairing is greater than any single sail change you could make.  As an example:  Changing from a working Jib to a Drifter.

    5)  The boat will obtain hull speed in approximately 5k less wind.

    6)  Hull speed will be increased about .15k.  This is due to the effective lengthening of the waterline which is now more effectively including the rudder.

    7)  A faster boat is also faster to weather.

    8)  If you wish, you can sail around at the same speeds as before but use a greatly reduced sail area.

    9)  Typically your boat will now be faster than 30-35% more of the boats than before, in your same sailing area.  As an example:  you will be sailing with Catalina 36's and 38's, not Catalina 30's.

    10) Examples of just some of the boats beaten "Boat for Boat" in sanctioned category 1 races.  ie, "apples to apples":  HC 33 (2), Crealock 37, Erickson 35, Tanton 35, Pacific 40, C&C 37, Cal35,  Pretorien 35, Valiant 40, Islander 36, Cascade 36.

    11) Any faired W-32 will be equal to Saraband.

    12) My belief is that the fairing will be even more effective on the W-28 than on the W-32.

    13) The cost of materials to do the fairing are less than ANY new sail at about $600.us, when using Epoxy.

    14) The boat will be faster no matter which wrong sail you may be using.

    15) A faired W-32 has logged 1774nm in a 10 day period.  Not bad huh?

    16) The average speed gain while cruising will be about 1/2k or 12 miles per day.

    17)  There May be some Real data if Jay ever goes sailing and takes Norm with him.

    Good Luck,     Dave 

     

    Last modified: February 09, 2015 2:33 PM | Anonymous member
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