Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 26-07-2011, 09:12   #1
Registered User

Join Date: Dec 2009
Location: Hong Kong
Posts: 118
Exclamation Need a New Propeller, Please Help

Hi

How can I know what propeller would suit my boat best??

I have a Shipman 28 with a 20 BHP Yanmar, but I am sure the propeller could be improve, any tips??

Do you have a similar engine?
What propeller do you use??


Thanks for taking the time to reply

Regards
Andres
__________________

__________________
andreshs1 is offline   Reply With Quote
Old 26-07-2011, 09:45   #2
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
One starts with two pieces of valuable info. First, what is on there now? Second, what is the performance now?

The performance check is done with the boat in proper clean condition. One should be able to get nearly full power rpm tied to the dock (or stern anchor for proper sailors) and full power rpm at cruise speed.

Without that info one must rely on an identical boat or a numerical computation.
__________________

__________________
daddle is offline   Reply With Quote
Old 26-07-2011, 09:52   #3
Registered User
 
Target9000's Avatar

Join Date: May 2009
Location: New Orleans LA
Boat: 74 Westsail 32
Posts: 1,379
Re: Need a new propeller, please help

Also please note your transmission gear ratio.
__________________
Let your heart tell you where to go, but let your brain tell you how to get there.

Sundowner Sails Again
Target9000 is offline   Reply With Quote
Old 26-07-2011, 09:55   #4
TOM
Registered User

Join Date: Mar 2008
Location: On our yacht Byamee
Boat: Footloose 40 steel cutter
Posts: 316
Images: 1
Re: Need a new propeller, please help

There are a number of good prop calculation websites ,they will ask you to enter things like boat lenght,gearbox ratio ,displacement etc,etc they give a fairly accurate answear .I used one when i repowered .

www.byamee.com
__________________
TOM is offline   Reply With Quote
Old 26-07-2011, 10:00   #5
Registered User
 
Astrid's Avatar

Join Date: Oct 2008
Location: Northern British Columbia, part of the time in Prince Rupert and part of the time on Moresby Island.
Boat: 50-ft steel Ketch
Posts: 1,885
Send a message via MSN to Astrid Send a message via Yahoo to Astrid
Re: Need a new propeller, please help

If you write to prop manufacturers and give them information found on the following questionnaire. The manufacturer will then know precisely what kind of prop you need tailored to your boat. While the question sheet is for a feathering type prop, the information requested will do for any prop, fixed or otherwise.

Size Questionnaire

Also check out this page:

http://mysite.verizon.net/resqp86c/p...lers/id20.html
__________________
'Tis evening on the moorland free,The starlit wave is still: Home is the sailor from the sea, The hunter from the hill.
Astrid is offline   Reply With Quote
Old 26-07-2011, 10:22   #6
Registered User

Join Date: Dec 2009
Location: Hong Kong
Posts: 118
Hi guys

Thanks for the info and the links. I'll get on the water this weekend Nd get the measurements

I am very new at sailing, only had the boat for a few months, so I dont know much about boats.

What propeller do you have installed or you recommend??
folding, fixed pitch, self pitching, high vortex, etc

Regards
Andres
__________________
andreshs1 is offline   Reply With Quote
Old 26-07-2011, 11:36   #7
Registered User
 
Astrid's Avatar

Join Date: Oct 2008
Location: Northern British Columbia, part of the time in Prince Rupert and part of the time on Moresby Island.
Boat: 50-ft steel Ketch
Posts: 1,885
Send a message via MSN to Astrid Send a message via Yahoo to Astrid
Re: Need a New Propeller, Please Help

I use a VariProp.
__________________
'Tis evening on the moorland free,The starlit wave is still: Home is the sailor from the sea, The hunter from the hill.
Astrid is offline   Reply With Quote
Old 26-07-2011, 12:02   #8
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,363
Re: Need a New Propeller, Please Help

The Max Prop is probably the most well proven variable pitch prop out there. Doesnt mean others arent good. But it will cost you probably $2000-3000 US. Otherwise a 3 blade Michigan is good. at probably $300 (?) You need to do the RPM test though.
__________________
Cheechako is offline   Reply With Quote
Old 26-07-2011, 13:16   #9
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
Re: Need a New Propeller, Please Help

Here's something that's been around the block a few times that might help. Read all the way through and check out the graphs.
Proper Prop Size
kind regards,
__________________
John
SkiprJohn is offline   Reply With Quote
Old 26-07-2011, 16:36   #10
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
Before spending big...

Changing propellers is an expensive complicated process. You really need to check the performance of your existing propeller first.

My suggestions: -
1) If you don't already have a GPS get one. Plotters are best but a plain GPS that reads in knots or, even better, tenths of a knot will work fine.
2) Next time you go out check your GPS speed and engine RPM. Make notes in your log. Check your engine as you go and don't use more than 80% power unless you have to.
3) After you get a feel for how the boat is look for a quiet calm stretch of water and do a couple of runs up and down it at various engine speeds. Average the speeds in each direction. Make note of the results.
4) Now calculate your boats theoretical maximum hull speed. This is often taken as 1.4 times the square root of the waterline length in feet.

Now, did your boat get anywhere near its hull speed? Half a knot is probably not worth worrying about. More than that and you've got something to chase over the next few years...
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 26-07-2011, 17:29   #11
Registered User
 
Astrid's Avatar

Join Date: Oct 2008
Location: Northern British Columbia, part of the time in Prince Rupert and part of the time on Moresby Island.
Boat: 50-ft steel Ketch
Posts: 1,885
Send a message via MSN to Astrid Send a message via Yahoo to Astrid
Re: Need a New Propeller, Please Help

As a thought, how clean is your hull and prop--that would affect how well your boat does on a trial run.
__________________

__________________
'Tis evening on the moorland free,The starlit wave is still: Home is the sailor from the sea, The hunter from the hill.
Astrid is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: 16” Diameter x 12” Pitch RH 3-Blade Bronze Propeller Target9000 Classifieds Archive 4 21-07-2011 21:02
For Sale: Maxprop Propeller Mylady Classifieds Archive 2 05-07-2011 07:10
For Sale: Michigan Sailor 2-Blade Propeller Undine Classifieds Archive 1 27-06-2011 03:07



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 21:47.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.