Reply
 
Thread Tools Search this Thread Display Modes
 
Old 03-27-2019, 07:56 PM   #1
Guru
 
Lepke's Avatar
 
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 2,337
Gate Rudder

A read about gate rudders awhile ago, and now there's a couple Youtube videos. Two single screw ships were built in Japan to the same size, design and machinery except for the rudder. One has a single conventional rudder and the other with twin rudders alongside the prop with expanded movement ability. Besides enhanced rudder effects, they claim a 14% energy savings with the gate rudders in an early trial and now claim 20-30%.
I've used Kort nozzles and they give a lot more thrust with the same engine. The twin rudders confine the thrust and probably duct it like a Kort. I don't know what the rudder machinery looks like, complicated I'm sure. But if used with simple twin rudder machinery and just for the added thrust and energy savings it looks worth the effort for a 20% savings over the life of the vessel. You could run at the same cruising speed with lower rpm or cruise faster at the current rpm. On new builds, a smaller engine.

__________________
Advertisement

Lepke is offline   Reply With Quote
Old 03-27-2019, 08:55 PM   #2
Guru
 
Seevee's Avatar
 
City: st pete
Vessel Model: 430 Mainship
Join Date: Sep 2016
Posts: 2,904
Sounds interesting. Wonder how it performs on smaller boats. And I hate videos with no voice.
__________________

__________________
Seevee
Seevee is online now   Reply With Quote
Old 03-27-2019, 10:47 PM   #3
Guru
 
City: Port Canaveral
Join Date: Jun 2012
Posts: 2,005
It looks similar to the Kitchen rudder.
Mako is offline   Reply With Quote
Old 03-28-2019, 01:41 AM   #4
Guru
 
Sailor of Fortune's Avatar
 
City: St Augustine,Fl
Join Date: Sep 2009
Posts: 3,414
Never heard of this rudder configuration but looks interesting. I also have Kort nozzle experience and am not a fan, Yes they give more bollard pull and all but prefer open wheel propulsion.
__________________
Jack ...Chicken of the sea! 1600 ton Master of towing/Oceans. 1600 ton Master/Oceans.
Sailor of Fortune is offline   Reply With Quote
Old 03-28-2019, 10:01 AM   #5
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,115
I’ve talked about a cruder version for years. Just two rudders. One on either side of the propwash.

Just like w airplanes the propwash if passing over part of the boat can be a drag. The rudder is pulling the boat backwards when underway. The relatively high velocity of water over the boat’s rudder causes a lot of drag and that drag is pulling backwards on the boat. Imagine trying to hold onto a rudder holding it in the propwash or go 25 knots and thrust your rudder down into the water alongside. It’s a drag man

Also the propwash is not straight. It cones in on aircraft and may do so on a boat. And rudders that aren’t flat plates will experience some interplane drag similar to biplanes. Two pilings in a river have more than twice as much drag of one if they are close to each other.

Thanks very much for posting Lepke.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 03-28-2019, 11:14 AM   #6
Guru
 
Seevee's Avatar
 
City: st pete
Vessel Model: 430 Mainship
Join Date: Sep 2016
Posts: 2,904
Quote:
Originally Posted by Nomad Willy View Post
I’ve talked about a cruder version for years. Just two rudders. One on either side of the propwash.

Just like w airplanes the propwash if passing over part of the boat can be a drag. The rudder is pulling the boat backwards when underway. The relatively high velocity of water over the boat’s rudder causes a lot of drag and that drag is pulling backwards on the boat. Imagine trying to hold onto a rudder holding it in the propwash or go 25 knots and thrust your rudder down into the water alongside. It’s a drag man

Also the propwash is not straight. It cones in on aircraft and may do so on a boat. And rudders that aren’t flat plates will experience some interplane drag similar to biplanes. Two pilings in a river have more than twice as much drag of one if they are close to each other.

Thanks very much for posting Lepke.
Good points. And seems like there's some merit to a ducted prop, essentially a rudder that wraps around the prop. Planes have these, too. However, in boating, not sure what the tradeoffs are.

Also, the flat rudder may not be the most efficient. The fishtail rudder certainly has better handling and my understanding that it doesn't significantly affect the speed..... but may at high speeds. Perhaps better for trawlers. The NACA 23000 wing in aircraft is similar, fat front and skinny back, but is not symmetrical, and has great performance characteristics.

Now, here's a question...... why don't we see more hydrofoil trawlers? Seems like once you get it up, it becomes fast and efficient?
__________________

__________________
Seevee
Seevee is online now   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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



» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 03:06 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×