Steering weak point. - 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 > Skills and Seamanship > Seamanship & Navigation
 Not a Member? 

Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


Reply
 
LinkBack Thread Tools
  #1  
Old 01-06-2007
Banned
 
Join Date: Apr 2006
Location: MS Gulf Coast
Posts: 711
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 0
seabreeze_97 is on a distinguished road
Steering weak point.

When reading about experiences at sea, it seems most of the time in a rescue situation, the steering (among other things) is knocked out after a storm. Now, I understand that there are massive forces involved, but is there a common weakness? What's the most common failure when steering is disabled??
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 01-06-2007
RichH's Avatar
Senior Member
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 2,968
Thanks: 10
Thanked 89 Times in 81 Posts
Rep Power: 15
RichH will become famous soon enough
Such failure is usually from the boat being forced in reverse at speed .... a rudder and its steering structure simply can't handle such forces when going violently astern ... its a mathematical/structural problem.

Similarly, Airplanes dont 'hang-together' too well going backwards and if forced to do so ... usually 'break'.

To build for such anomalies, the structure would be 'massive' that would require a LOT of additional weight.
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 01-06-2007
TrueBlue's Avatar
Señor Member
 
Join Date: Oct 2004
Location: Narragansett Bay
Posts: 4,853
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 13
TrueBlue is a jewel in the rough TrueBlue is a jewel in the rough TrueBlue is a jewel in the rough
Giving the fact that forces against a sailboat's steering gear will be higher in reverse, I presume that due to a lack of bottom support, there is a greater probability of a spade rudder failing before a skeg hung rudder.
__________________
True Blue . . .
sold the Nauticat
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 01-06-2007
RichH's Avatar
Senior Member
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 2,968
Thanks: 10
Thanked 89 Times in 81 Posts
Rep Power: 15
RichH will become famous soon enough
Trigonometry ....

In reverse the forces generated by water flowing across a rudder will generate MORE forces on a pintle hung or skeg/keel hung rudder than on a spade. Spade rudders are usually more hydrodynamically 'balanced', although you can apply many more 'hinges' to a skeg/keel, etc. rudder. Still its the 'trigonometry' of the forces applied to a rudder working in reverse that breaks the system.

If a rudder is 'locked down' when going at speed in reverse its probably safer, as its probably the 'impact' of the rudder hitting the stops that breaks the stock, the internal flanges of the rudder, the quadrant, etc.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 01-06-2007
camaraderie's Avatar
moderate?
 
Join Date: May 2002
Location: East Coast
Posts: 13,877
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 15
camaraderie is a jewel in the rough camaraderie is a jewel in the rough camaraderie is a jewel in the rough
TB...yes but also because there is no skeg to protect the rudder from impact or catching on something and getting jerked. Rudders are usually just foam covered by fiberglass with a metal grid from the rudder stock and are much more prone to damage than say a keel from impacts so many cruisers prefer a skeg to a spade even though the spade is the "speedier" of the two.

On a little different note...another common failure in steering is the wheel cables and pulleys and slack to the quadrant. On a prior boat (with a skeg rudder) we had a bump grounding backing out of the slip and the rudder was thrown over to its stoppers. Everything looked OK externally...but the eye bolt attaching the steering cables to the quadrant was bent slightly from the force and a day later, we lost steerage as the cable jumped off the quarant. We learned 2 things that day:
1. Check and lubricate tension and connections on steering cables annually and after any "events"
2. An underdeck autopilot will steer your boat if the wheel system fails. We ran around looking to get at the emergency tiller when I could have simply pushed a button quickly! (That's called seamanship...lessons from experience!!)
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 01-06-2007
TrueBlue's Avatar
Señor Member
 
Join Date: Oct 2004
Location: Narragansett Bay
Posts: 4,853
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 13
TrueBlue is a jewel in the rough TrueBlue is a jewel in the rough TrueBlue is a jewel in the rough
Rich,
I don't proclaim to be an expert on the dynamics of rudder design. But from a layman's perspective, it seems that regardless of rudder size or shape, the bottom pintle of a skeg-hung rudder MUST have a greater resistance against diametrically opposed water pressures, over a spade.

Spade rudders need to be more hydrodynamically balanced than skeg hung rudders since the only physical connection to the boat is the rudder post and is still the weakest link, thus having a higher probability of breakage.

Edit - Note to self : have morning coffee before posting.
__________________
True Blue . . .
sold the Nauticat

Last edited by TrueBlue; 01-06-2007 at 11:11 AM.
Reply With Quote Quick reply to this message Share with Facebook
  #7  
Old 01-07-2007
Owner, Green Bay Packers
 
Join Date: Sep 2006
Location: SW Michigan
Posts: 10,318
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
Trueblue,
I believe that Rich's point was that the spade rudder is constructed in one of two ways; semi-balanced or balanced. In either of those constructions the rudder post is not at the leading edge of the rudder as it is in most skeg mounted rudders. The objective in balancing the rudder is to get relatively equal masses forward and aft of the rudder post. This eases the strain on all components of the steering system immensely. A rudder constructed in this manner turns almost as easily astern as ahead. The skeg hung rudder, when going astern, acts just like the door that got caught by the wind while open.

Pintles and gudgeons, regardless of mounting location are weaker than the rudder stock itself. With a balanced, or semi-balanced rudder the strain is transmitted via the rudder stock upwards to the bearing. The bearing and quadrant are mounted in such a secure way that no gudg/pint can be. As previously mentioned, the damage to the skeg hung rudder probably occurs more from being slammed over against the stops than the actual force of the water.

A balanced, but more commonly a semi-balanced rudder can be mounted to a skeg or the keel but it does take a little engineering.
Reply With Quote Quick reply to this message 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:

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

 
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
Steering System Spring Checkup Tom Wood Her Sailnet Articles 0 04-26-2004 09:00 PM
Checking the Wheel Steering System Will Keene Gear and Maintenance Articles 0 07-31-2002 09:00 PM
Emergency Steering John Kretschmer Seamanship Articles 0 03-08-2002 08:00 PM
Emergency Steering John Kretschmer Gear and Maintenance Articles 0 03-08-2002 08:00 PM
Emergency Steering John Kretschmer Cruising Articles 0 03-08-2002 08:00 PM


All times are GMT -4. The time now is 09:13 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.