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Old 23 April 2006, 06:21   #1
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Country: UK - England
Town: West Wickham
Boat name: Aries IV
Make: Scorpion
Length: 8m +
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To list or not to list?

Ok, now I'm confused ...

I am told by those illustrious people at Scorpion that my boat needs to have a list to counteract the engine/propellor torque (8.5 mtr boat, 250hp Etec).

Apart from the fact that I shall be keeping my boat in a marina and a list will not look or feel great, I am interested to know members of the Forum's views on whether or not you believe that having a list is a good thing and if it actually makes a positive difference.

I thought that engine offset was all that was needed to offset propellor or engine torque.

I am not an engineer (I guess that's obvious!) but it doesn't seem entirely logical to me that a boat should intentionally be built with a list. In my case, this will be caused by 2 x 120ah batteries on the same side.

I would welcome your thoughts.

Thank you!

Chris.
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Old 23 April 2006, 06:40   #2
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Quote:
Originally Posted by Chris Murray
I thought that engine offset was all that was needed to offset propellor or engine torque.
Engine offset will create a list. On my previous boat I used engine offset, consol offset and my weight to counter prop torque. Plainly the boat would have a list at rest but it ran straight. However, I feel trimtabs are a better way of dealing with the problem because listing will develop in beam sea situations and this can be countered irrespective of which side the wind is blowing from. I find there is also another plus. If the tabs are mounted along the hull V rather than horizontally, there is a slight steering moment generated with a tab down. So, when countering the list generated by the wind, the tab also causes the boat to steer slightly towards the wind and this prevents the driver having to constantly compensate for drift.
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Old 23 April 2006, 06:45   #3
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this is how i see it...

If you don't have some weight on one side to counteract the prop torque, the boat will list while at speed, which is worse than having a list at rest/slow speed. I don't think it would be that noticable on a rib that size anyway?

The other thing to do would be to have two engines like the scorp I saw in yarmouth yesterday...twin 275hp verados!
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Old 23 April 2006, 06:50   #4
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Or buy a boat that doesn't need a list to make it run straight?
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Originally Posted by Zippy
When a boat looks that good who needs tubes!!!
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Old 23 April 2006, 07:02   #5
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What boat would that be, Cooks?

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Old 23 April 2006, 07:08   #6
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Quote:
Originally Posted by Cookee
Or buy a boat that doesn't need a list to make it run straight?
Cookee has got in there first, Andre will be along in a minute
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Old 23 April 2006, 07:15   #7
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Followed by Leeway. That'll be why there's a hook on one side...


Oops, did I say that?
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Old 23 April 2006, 07:21   #8
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Quote:
Originally Posted by jwalker
Followed by Leeway. That'll be why there's a hook on one side...


Oops, did I say that?
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Old 23 April 2006, 07:34   #9
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I don't know anything about the science of this so I should probably keep quiet but....

Mine doesn't list at any stage from rest to full speed (well it didn't until the backside fell out of the tube on one side...) it doesn't have any trim tabs on the hull, and the engine is mounted in the middle. Admittedly it "only" has a 115 on the back, but it doesn't appear to have any negative effects from prop torque, you don't notice anything apart from if you take off from rest to full speed you need a very small steering input to keep it in a straight line.
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Old 23 April 2006, 07:50   #10
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Country: UK - England
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Thanks JW,

This is the sort of info that is most helpful.

I do have trim tabs fitted - not much else at the mo but yup, the tabs are there - along with an awesome radar arch and "Tri-lens".

Further comments would be appreciated - Thanks!

Chris.
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