Reply
 
Thread Tools Search this Thread
 
Old 27 May 2008, 23:18   #1
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
Outboard Offsets

What exactly is the purpose? Is this simply to counter poorly distributed weight in the boat or to counter handling tendancys caused by the propellors rotation?

Mark
__________________

__________________
Markyboyo is offline   Reply With Quote
Old 28 May 2008, 03:36   #2
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,194
to counteract the Prop torque! some more than others, the craft manufacturer will advise the offset if any!!
__________________

__________________
matt h is offline   Reply With Quote
Old 28 May 2008, 03:55   #3
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
Thanks for that Matt, makes sense. I'll have to get on to Humber before I have the Etec fitted up...unless anyone can advise on a 5.5 destroyer??!!
__________________
Markyboyo is offline   Reply With Quote
Old 28 May 2008, 05:04   #4
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,194
three quarters to one inch to the right, looking from behind, using a recommended engine within limits, eg weight and power, would be about right, a few millimeters either way is not going to make any difference,
__________________
matt h is offline   Reply With Quote
Old 28 May 2008, 07:44   #5
Member
 
Country: UK - Scotland
Town: Inverness
Boat name: none
Make: none
Length: 5m +
Engine: none
MMSI: none
Join Date: Mar 2007
Posts: 1,908
You will struggle to get more than about an inch depending on the engine width and transom height on a destroyer. I got exactly one inch which was the maximum I could have got without resorting to a saw in the transom cutout.
Its all a compromise, my outboard is slightly offset to stardboard but the fuel tank is offset to port and when I am driving the boat alone I sit to starboard, god knows what direction the boat will end up listing to
__________________
BruceB is offline   Reply With Quote
Old 30 May 2008, 00:54   #6
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
I think my transom is prob rather different to yours Bruce, what with the aux cut out and being for an XL transom. It dosen't have the raised splash plates like yours, I'd post a photo but the boat is 4000 miles away!
__________________
Markyboyo is offline   Reply With Quote
Old 30 May 2008, 07:41   #7
Member
 
Country: Other
Town: Stanley, Falkland Is
Boat name: Seawolf
Make: Osprey Vipermax 5.8
Length: 5m +
Engine: Etec 150
Join Date: Mar 2006
Posts: 3,688
Is there a formula for calculating offset based on HP/hull length/phase of the moon or is it just a trial and error thing and the manufacturer will determine the best setup?

Just wondered as I know of a boat here which is awful (not a RIB) under full power it feels like it is going to sink with probably 15-20 deg of bank to port!
__________________
A Boat is a hole in the water, surrounded by fibreglass, into which you throw money...

Sent from my Computer, using a keyboard and mouse
BogMonster is offline   Reply With Quote
Old 30 May 2008, 08:13   #8
Member
 
Cookee's Avatar
 
Country: UK - England
Town: Salcombe, Devon, UK
Boat name: BananaShark
Make: BananaShark
Length: 10m +
Engine: 2xYanmar 260 diesels
Join Date: Mar 2003
Posts: 4,225
Quote:
Originally Posted by BogMonster View Post
Is there a formula for calculating offset based on HP/hull length/phase of the moon or is it just a trial and error thing and the manufacturer will determine the best setup?

Just wondered as I know of a boat here which is awful (not a RIB) under full power it feels like it is going to sink with probably 15-20 deg of bank to port!
There is no formula as every hull behaves differently - We put every engine in the middle and with careful prop selection and engine height adjustment we have never had a problem - trimming in too much also can accentuate any problem!
__________________
Cookee
Originally Posted by Zippy
When a boat looks that good who needs tubes!!!
Cookee is offline   Reply With Quote
Old 31 May 2008, 18:46   #9
Member
 
Country: UK - Scotland
Town: Inverness
Boat name: none
Make: none
Length: 5m +
Engine: none
MMSI: none
Join Date: Mar 2007
Posts: 1,908
Mark,
I thought yours was XL as well but with a cut out on the port side for an aux?
Mine doesn't have raised anything AFAIK, just made for an XL shaft motor.
Does that mean your transom is different if both are supposed to be XL?
__________________
BruceB is offline   Reply With Quote
Old 31 May 2008, 19:11   #10
Member
 
Hightower's Avatar
 
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
Quote:
Originally Posted by matt h View Post
three quarters to one inch to the right, looking from behind, using a recommended engine within limits, eg weight and power, would be about right, a few millimeters either way is not going to make any difference,
Not all of us have one that hangs from the right
__________________

__________________
Andy

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
Hightower 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 18:46.


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