Author Topic: Prop Pitch  (Read 1036 times)

KoKoMo

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Prop Pitch
« on: October 29, 2016, 08:35:13 AM »
Sorry we have not been very active on the site but we have been very busy.  We are making great progress with Kokomo "Shepherds Rest" restoration. She has a new engine, a new bow thruster, she is in the water after 12 years on the hard and the mast is up! Many hurdles have been jumped to get to this point and she is looking amazing.
One hurdle we have not been able to overcome is finding the proper prop pitch.  Kokomo is one of those rare CSY's with a V-Drive.  I know the typical transmission ratio is 2.58 to 1 but our Velvet drive has a 1 to 1 ratio.  It throws all the prop pitch equations off.  She has the original 20" 15 prop but could only get 4knots under power.   We have been working with two of the most reputable prop shops in Ft. Lauderdale and neither one can understand how a 1 to 1 ratio transmission would end up on a sail boat. 
Does anyone have any ideas as to what the pitch should be?, as we have it at Lauderdale Propeller and they are awaiting my pitch number.
Thanks,
Norrm

Matthew Balch

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Re: Prop Pitch
« Reply #1 on: October 29, 2016, 05:40:38 PM »
Hi Norm.  My boat does not have your configuration, however I also have never seen a 1 to 1 ratio on a sailboat.  I would suggest if you have not done so already that there should be a metal plate on the top of the transmission that will have the ratio stamped into the metal.  My plate was  covered with paint, so when I was re-propping, I had to do some scraping to see the letters.  I was surprised to find that my tranny was different from what I thought it was.  Mine is 2.91.  Just saying...  Matthew

KoKoMo

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Re: Prop Pitch
« Reply #2 on: October 29, 2016, 06:22:09 PM »
Matthew,
 Thanks for the quick response. I have looked at the plate countless times and it is clearly 1 to 1.  I even took a picture of and keep looking at it in disbelief.  The propeller pitch equations show we should have a 16" prop with a 25 pitch!  Clearly it makes no sense.  I am almost wondering if the v drive has some sort of reduction built into it that would slow the shaft down.  Monday I plan on getting in touch with Walter V Drive and see what they have to say. 
If anyone has any input I am all ears. 
Thanks,
Norm

Soggy Geek

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Re: Prop Pitch
« Reply #3 on: October 29, 2016, 11:00:02 PM »
Dave says that Soggy Paws (CSY 44 WT) had a Perkins 4-154, 60 HP, straight shaft, shallow draft, Borg Warner Velvet drive, 2.91 to 1, and the standard prop for that is a 24" x 15 pitch.  But if you have a different tranny, and a v-drive, it will be different.

I think Warren Daniels (SeaNotes) has a Walkthrough with a V-Drive.  He was talking about repowering, but I don't know if he did.  He hasn't visited the forum in awhile, but maybe I'll give him a nudge by email and see if he'll come up and comment.

Also, I think Ed Marrill also had a walkthrough with a V-Drive, but he repowered a long time ago.  I believe Ed's on the CSY Owners group on Facebook.  You might get some responses there.

Sherry & Dave
Soggy Paws the CSY has been sold but not forgotten!
http://svsoggypaws.com/CSY/

KoKoMo

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Re: Prop Pitch
« Reply #4 on: February 03, 2017, 10:46:55 AM »
Mystery solved! After talking with Walter Machine Company, the manufacturer of the V-drive, the reduction is done in the V-drive, unit not the transmission. Hence the transmission is used only for shifting and all reduction is done in the gearing of the V-drive.  We were able to reach hull speed by increasing the prop pitch to 18.  It probably could have used a bit more pitch but the propeller company, Lauderdale Propeller, recommended against it. Again, thank you all for your input.
Smooth Sailing, Norm