Reply
 
Thread Tools Search this Thread
 
Old 14 August 2009, 13:40   #21
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: 2 stroke YAM 20 HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 10,114
Quote:
Originally Posted by codprawn View Post
Yes but the new super tankers and container ships have a single screw!!!

Some of the older massive ships had multiple screws though.

Here is the Emma Mærsk's stern end............
Because of course the pros/cons of anything on a supertanker is directly transferable to a RIB.
__________________
Poly is offline   Reply With Quote
Old 14 August 2009, 13:43   #22
Member
 
Country: UK - Channel Islands
Town: Guernsey
Make: Pending
Length: 8m +
Join Date: Aug 2005
Posts: 296
Some great comments

flying around, but I don't yet see a solution to Willk's (implicit) question:

"If you find a nice tidy solution for mounting an auxie on a single diesel outdrive rig - please share!"
__________________

__________________
cuttlefish is offline   Reply With Quote
Old 14 August 2009, 16:36   #23
Member
 
Country: UK - Wales
Town: swansea
Boat name: Too Blue
Make: BLANK
Length: 8m +
Engine: Suzuki DT225
Join Date: Mar 2004
Posts: 12,791
Quote:
Originally Posted by Polwart View Post
Because of course the pros/cons of anything on a supertanker is directly transferable to a RIB.
Indeed - maximum efficiency and best performance/less drag to save fuel.
__________________
codprawn is offline   Reply With Quote
Old 14 August 2009, 17:06   #24
Member
 
Bigmuz7's Avatar
 
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,068
Quote:
Originally Posted by severncoxswain View Post
Depends what you are wanting to do with the actual boat, if its pleasure one engine, work, saftey or anything else I would have to say two!
Ive always thought that about girls
__________________
Bigmuz7 is offline   Reply With Quote
Old 15 August 2009, 03:50   #25
Member
 
Country: India
Town: Mumbai
Boat name: Pathfinder
Make: Zodiac
Length: 7m +
Engine: 2 X Yamaha F115s
Join Date: Feb 2009
Posts: 66
while you can still make the choice...

have a look at this thread http://rib.net/forum/showthread.php?t=31652, these are twin 115s on a transom rated for twin 150s or a single 250.

I would have imagined the transom would have been in better shape had it been a single 225.

Otherwise I would imagine it's basically speed, economy and cost of maintenance Vs redundancy and handling
__________________
shahid is offline   Reply With Quote
Old 15 August 2009, 04:03   #26
Member
 
Country: UK - England
Town: Mighty Penryn
Boat name: Little Joe.
Make: Avon Searider
Length: 4m +
Engine: Honda BF50
Join Date: Aug 2005
Posts: 8,841
Quote:
Originally Posted by Bigmuz7 View Post
Ive always thought that about girls
Best they're not related though.
__________________
Mollers is offline   Reply With Quote
Old 15 August 2009, 04:08   #27
Member
 
Country: India
Town: Mumbai
Boat name: Pathfinder
Make: Zodiac
Length: 7m +
Engine: 2 X Yamaha F115s
Join Date: Feb 2009
Posts: 66
Quote:
Originally Posted by Mollers View Post
Best they're not related though.
Well we were talking about Twins
__________________
shahid is offline   Reply With Quote
Old 15 August 2009, 17:55   #28
JSP
Member
 
Country: UK - England
Town: Southport
Boat name: Qudos
Make: 5.4 Searider
Length: 5m +
Engine: Yam 115 V4
MMSI: 235068784
Join Date: Sep 2008
Posts: 3,930
Quote:
Originally Posted by shahid View Post
Well we were talking about Twins
Good stuff
__________________
JSP is offline   Reply With Quote
Old 15 August 2009, 19:01   #29
Member
 
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,962
With twins, you do have immediate redundancy in that one engine is likely to stay running should the other one stop. Also you don't have the faff of deploying the auxiliary motor, however, although your single motor will be capable of half your power while both engines are running, it wont be able to produce that half power if one engine fails. This is because it will immediately become over propped. With a planing hull, it is quite likely that one engine of a twin setup will not be able to get your boat planing so you will be little better off, in terms of speed, than you would be with a decent sized auxiliary motor. It would be possible to carry a spare prop of a correct pitch for one engine but then you're back to faffing around at sea trying to swap props. Probably not what you want to be doing.

What twins will give you, in performance terms, is good grip on the water at low speed and good acceleration because there will be considerably more prop blade area on two props than on a single, albeit a larger single.
__________________
JW.
jwalker is offline   Reply With Quote
Old 15 August 2009, 19:44   #30
Member
 
chewy's Avatar
 
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
Quote:
Originally Posted by jwalker View Post
Also you don't have the faff of deploying the auxiliary motor, however, although your single motor will be capable of half your power while both engines are running, it wont be able to produce that half power if one engine fails. This is because it will immediately become over propped. With a planing hull, it is quite likely that one engine of a twin setup will not be able to get your boat planing so you will be little better off, in terms of speed, than you would be with a decent sized auxiliary motor.
Strange that because an Atlantic 75 will plane on one engine easy enough and reach max rpm too.
The Aqua 27 I use would make 13kts flat out and on one engine 8kts again reaching max rpm.
__________________

__________________
chewy is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 18:00.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.