New prop causes veer to port - solution?? - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #11  
Old 06-10-2008
Plumper's Avatar
Sailor
 
Join Date: Nov 2007
Location: Vancouver Island
Posts: 845
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
Plumper is on a distinguished road
If the prop is turning in a clockwise direction (in forward) when viewed from astern then the bow swinging to port may be because the clearance between the top of the propeller and the bottom of the boat is insufficient and the prop is cavitating at the top. That might cause the boat to veer to port at higher speeds but be less noticeable at slow speeds because there would be no cavitation. It would likely be less noticeable when going astern because the revs are usually much lower (no cavitation).

That is my guess......

Thinking about it some more, the fact that you went from a three blade to a two blade may also contribute to the new cavitation. With two blades, the top blade may be cavitating while the bottom blade is biting introducing the prop walk. Of course with the three blade, whenever there was a blade straight down there wasn't one near the hull so cavitation was minimized.
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217

Last edited by Plumper; 06-10-2008 at 04:13 PM. Reason: More thought!
Reply With Quote Share with Facebook
  #12  
Old 06-10-2008
EO32's Avatar
Senior Member
 
Join Date: Jan 2008
Location: Fremont, WA
Posts: 165
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
EO32 is on a distinguished road
Just another guess, but it sounds like prop walk in forward. Could be the difference from a three blade to two blade.
__________________
If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps better than most. A small sailing craft is not only beautiful, it is seductive and full of strange promise and the hint of trouble.

- E.B. White
Reply With Quote Share with Facebook
  #13  
Old 06-10-2008
Junior Member
 
Join Date: Oct 2000
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
sailingdeacon is on a distinguished road
Conceivably it could be cavitation However the manufacturer, on viewing the photos showing the large space from the blade end to the hull, gave up on that possibility. Yet this prop has an extremely efficient blade and is not shaped like most folding blades - so perhaps it is cavitating due to that. So I am back to my original question on this thread. Would a reduction of 1" pitch help the problem? Let's assume both cases: that it is cavitating and that it is not cavitating. Or would a reduction in diameter be better? That was the thrust of my original question...
Reply With Quote Share with Facebook
  #14  
Old 06-10-2008
Junior Member
 
Join Date: Oct 2000
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
sailingdeacon is on a distinguished road
One more note... If I turn the rudder over to the other side... to the right, at a certain point, the force changes and starts pulling the wheel the other way.... indicating that the "not so balanced" rudder is being pushed much harder and unequally by water force that it was formerly. In other words the water flow from this prop is not equal on both sides of the rudder (for whatever reason, perhaps cavitating???) , and the rudder becomes unbalanced. So... a smaller pitch or a smaller diameter... or will it make no difference at a give speed.
Reply With Quote Share with Facebook
  #15  
Old 06-10-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
Is the rudder rectangular in shape or is it foil shaped? Has it been faired recently? Is it symmetrical in profile???
__________________
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.
Reply With Quote Share with Facebook
  #16  
Old 06-10-2008
Junior Member
 
Join Date: Oct 2000
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
sailingdeacon is on a distinguished road
Rectangular, narrower at the bottom. Has not been faired.

Not exactly sure of your symmetrical question, but viewed from the side it is symmetrical per vertical angles. Slightly longer aft edge leading to the upturn of the hull aft.

I also just noticed a single article on the web discussing the paddle-wheel effect which turns boat sideways... as opposed to torque. No solution given.
Reply With Quote Share with Facebook
  #17  
Old 06-10-2008
Junior Member
 
Join Date: Oct 2000
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
sailingdeacon is on a distinguished road
Another clue that may be key: even with the strong pull to port, the rudder is aligned straight foreward and aft. To me this implies a right hand paddle wheel effect rather than an imbalanced rudder under power.
Reply With Quote Share with Facebook
  #18  
Old 06-10-2008
Junior Member
 
Join Date: Oct 2000
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
sailingdeacon is on a distinguished road
JB2: keep in mind that this new design prop has almost no reverse prop walk. It is only a "problem" at higher speeds forward. All in all, a super 2 blade folding prop that eliminates your reverse prop walk problem
Reply With Quote Share with Facebook
  #19  
Old 06-10-2008
Plumper's Avatar
Sailor
 
Join Date: Nov 2007
Location: Vancouver Island
Posts: 845
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
Plumper is on a distinguished road
It still sounds to me like it is cavitating and not getting enough clean flow at the top dead centre position when moving ahead. I would try reducing the pitch (if that is easy and inexpensive) first. The boat may go a little slower but it also may solve the problem.
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
Reply With Quote Share with Facebook
  #20  
Old 06-11-2008
Idiens's Avatar
Larus Marinus
 
Join Date: Jan 2007
Location: Brussels
Posts: 1,756
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Idiens is on a distinguished road
Quote:
Originally Posted by sailingdeacon View Post
So I am back to my original question on this thread. Would a reduction of 1" pitch help the problem? Let's assume both cases: that it is cavitating and that it is not cavitating. Or would a reduction in diameter be better? That was the thrust of my original question...
I don't think it will, I changed my Maxprop pitch to get the max revs up and it made no difference the effect on the rudder at max power. If anything I think the higher rpm produces more effect. I somehow doubt the cavitation effect in this, as the cavitation only occurs close to the propeller and you say your rudder and hull are well clear. I think it is more to do with the difference between the boat speed flow and the prop wake flow at the rudder. If you shut down the engine at max speed, the effect goes away, so it's certainly either prop walk or prop wake effect on the rudder.
__________________
Jonathan-Livingston
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Number of race entrants up from 2006 - Port Huron Times Herald NewsReader News Feeds 0 07-16-2007 07:15 AM
Changing prop underwater trantor12020 Gear & Maintenance 16 03-03-2007 12:02 PM
Max prop on a saildrive levenezia Gear & Maintenance 16 09-20-2006 12:07 AM
Choosing the Right Propeller Sue & Larry Gear and Maintenance Articles 0 02-04-2003 07:00 PM
Choosing a Prop Sue & Larry Gear and Maintenance Articles 0 12-24-2001 07:00 PM


All times are GMT -4. The time now is 04:54 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.