Plastic prop issue - SailNet Community
Reply
 
LinkBack Thread Tools
post #1 of 13 Old 05-07-2009 Thread Starter
I don't discuss my member
 
Fstbttms's Avatar
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,183
Thanks: 5
Thanked 26 Times in 26 Posts
Rep Power: 13
 
Plastic prop issue

I have a customer with a Catalina 320. We replaced his Martec folder with a 2-blade, 15X11 Perfect Pitch plastic prop. When the owner took the boat out for a test putt, he noticed a loud "thrumming" resonance seeming to come through the transom at a certain RPM range. Inspection underway indicated no problems, nothing loose or vibrating in the drive train or stern of the boat. Thinking it may have been a cutless problem, he hauled the boat and had the yard manager look it over. Everything seemed fine. On the assumption that the problem was a tip clearance/vortex issue, the owner bought the "Extendo" version of the same prop (see photo), which moves the blades further aft and away from the hull. I installed it yesterday and to the owner's great dismay, the same problem occurred, but at a different RPM range and much louder now.

Talking to a local prop shop owner, he suggested it may be a harmonic problem or something similar (although he did admit to never having come across this issue with the Perfect Pitch props) and suggested a fix might be to file the leading edge of the blades down.

Has anyone else experienced anything like this with these props?

Fstbttms is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 13 Old 05-08-2009
Reward for lost Kraken!
 
hellosailor's Avatar
 
Join Date: Apr 2006
Posts: 11,481
Thanks: 5
Thanked 132 Times in 129 Posts
Rep Power: 11
   
" a fix might be to file the leading edge of the blades down."
I'd be scared to do that, outright scared. If the prop maker did ANYTHING right, the odds are that they also put some effort into how they mold or shape the edges, and randomly attacking them with a file will just ensure the maker won't take them back. And no one else will really want them.

Thrumming resonance? Well, yeah, pulses of water shooting off the prop and hitting the hull. Heard of that with many "wrong" prop installations, either a matter of clearance, or balance, or always something very basic but simply wrong for that combination or prop and hull.

Has Perfect Pitch made any comment?
hellosailor is offline  
Quote Quick Reply Share with Facebook
post #3 of 13 Old 05-08-2009 Thread Starter
I don't discuss my member
 
Fstbttms's Avatar
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,183
Thanks: 5
Thanked 26 Times in 26 Posts
Rep Power: 13
 
Quote:
Originally Posted by hellosailor View Post
Has Perfect Pitch made any comment?
Yes, they suggested he buy the "Extendo" model.
Fstbttms is offline  
Quote Quick Reply Share with Facebook
post #4 of 13 Old 05-08-2009
Senior Member
 
nightowle's Avatar
 
Join Date: Aug 2006
Posts: 226
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 9
 
commerce at it's best! THe mfg. recommends an upsell. Perfect!

________
S/V Don't Panic!
O'Day 27
Seattle, WA

“Navigare necesse est, vivere non est necesse” To Sail is vital, to live is not.
nightowle is offline  
Quote Quick Reply Share with Facebook
post #5 of 13 Old 05-08-2009
Telstar 28
 
sailingdog's Avatar
 
Join Date: Mar 2006
Location: New England
Posts: 43,290
Thanks: 0
Thanked 14 Times in 12 Posts
Rep Power: 14
         
How much clearance does the prop have on the boat??? Do you have a photo of it in-situ???

Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
sailingdog is offline  
Quote Quick Reply Share with Facebook
post #6 of 13 Old 05-08-2009
Senior Member
 
timebandit's Avatar
 
Join Date: Sep 2002
Posts: 928
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
 
Why was the original prop changed, did it make the noise too?

If nothing else was changed but the props then I think that RULE 1 applies here and for some reason these props are just not suitable for this application.

Rick
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Mac 25
Copernicus
Southern California
I am not a prejudice racist sexist bigot. I just hate stupid people.
timebandit is offline  
Quote Quick Reply Share with Facebook
post #7 of 13 Old 05-08-2009 Thread Starter
I don't discuss my member
 
Fstbttms's Avatar
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,183
Thanks: 5
Thanked 26 Times in 26 Posts
Rep Power: 13
 
Quote:
Originally Posted by sailingdog View Post
How much clearance does the prop have on the boat??? Do you have a photo of it in-situ???
No pix. The first plastic prop had about 3 1/2 fingers clearance. Didn't check the second one, but it's more than that.
Fstbttms is offline  
Quote Quick Reply Share with Facebook
post #8 of 13 Old 05-08-2009 Thread Starter
I don't discuss my member
 
Fstbttms's Avatar
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,183
Thanks: 5
Thanked 26 Times in 26 Posts
Rep Power: 13
 
Quote:
Originally Posted by timebandit View Post
Why was the original prop changed, did it make the noise too?
The original prop was a Martec folder. It was replaced because it was undersized and also not the correct pitch for the boat. Before the introduction of these plastic props, this issue did not exist on this boat.

It has been suggested to me that the plastic blades may be changing shape under load and causing the harmonics or resonance or whatever it is.
Fstbttms is offline  
Quote Quick Reply Share with Facebook
post #9 of 13 Old 05-08-2009
Learning the HARD way...
 
eherlihy's Avatar
 
Join Date: Jan 2007
Location: Boston / Ft Myers Area
Posts: 4,023
Thanks: 158
Thanked 105 Times in 102 Posts
Rep Power: 9
 
How is the alignment at the drive coupling?...

Before filing anything down, I would consider unbolting the coupling, turning the propshaft 1/3 or 1/2 a turn relative to the drive side of the coupling, and re-test. If the symptom changes, it's not the prop.

I suspect that the alignment of propshaft may be out.

Did you get paid to swap props twice?
eherlihy is offline  
Quote Quick Reply Share with Facebook
post #10 of 13 Old 05-08-2009 Thread Starter
I don't discuss my member
 
Fstbttms's Avatar
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,183
Thanks: 5
Thanked 26 Times in 26 Posts
Rep Power: 13
 
Quote:
Originally Posted by eherlihy View Post
How is the alignment at the drive coupling?...

Before filing anything down, I would consider unbolting the coupling, turning the propshaft 1/3 or 1/2 a turn relative to the drive side of the coupling, and re-test. If the symptom changes, it's not the prop. ?
I will suggest this to the owner, but if the alignment was not as issue with previous props, why would it be now?

Quote:
Originally Posted by eherlihy View Post
Did you get paid to swap props twice?
Of course. And I'll get paid again to effect whatever remedy the owner decides upon. I don't work for free.
Fstbttms is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Fixed vs. Free Wheeling Prop - Test Data Maine Sail Gear & Maintenance 18 01-26-2010 12:45 AM
harmonics vs vibration prop issue rdunncpa Gear & Maintenance 2 06-18-2008 03:46 PM
plastic thruster prop jms2550 Gear & Maintenance 3 11-09-2007 11:24 AM
Choosing the Right Propeller Sue & Larry Gear and Maintenance Articles 0 02-04-2003 07:00 PM
plastic prop grey99 Gear & Maintenance 7 12-19-2002 01:43 PM

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome