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Old 25 April 2003, 04:12   #1
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Twisting Scorpion

My Scorpion 6.5 Optimax 150 twists quite sharply when she comes out of the water on a wave. I quite like getting air but I am not keen on the twisting bit so I guess trim tabs might be the answer.

Any advice on what tabs would be suitable would be most welcome
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Old 25 April 2003, 04:23   #2
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JK can you delete this thread for me please. I did a search for trim tabs and am following Dirks advice and having a look at the Bennett website

< I think I'd better leave it as there's quite a lot more here now . . . JK >

ta
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Old 25 April 2003, 04:48   #3
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Twisting

wavehumper

Does the boat twist to the left on take off, if thats the problem just shift some weight around to the right hand side, ie move the batteries across and that will help keep the boat level in the air, and on take of turn the wheel to the right to conterfit the torque from the engine, should find it lands level then. You may not need tabs.

Julian
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Old 25 April 2003, 05:32   #4
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Or alternatively put a left-handed prop on. That cured my (Scorpion) problem.
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Old 25 April 2003, 07:21   #5
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Thanks guys I have been trying Julians Ideas and it hasn't really helped much, but I could probably try a little harder to redistribute the weight. I am couneracting with the steering wheel, but possibly not enough.

Brian I was talking to Andrew Cox a day or two ago and he was telling me about your solution so I might well give that a go
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Old 25 April 2003, 07:46   #6
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Top man that Andrew.
Came up with the solution that worked for me.
Anyone who needs a top-flight marine engineer in the West Country, contact Andy on:

andrewcox@marineenginering.fsnet.co.uk
Work: 01326 279001
Mobile: 07974 250533
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Old 25 April 2003, 07:59   #7
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Brian, this might sound rather odd but how do you get a left handed prop to make a boat go forwards? run the drive in reverse ?

Another solution might be off setting the engine, think its 1" for every 100 hp. JF might be able to add to this.

Pete
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Old 25 April 2003, 08:25   #8
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Pete
When you put a LH prop on you also have to take out the control box and reverse the lever attachment points. If you didnt do this you would have to pull the gear lever back to go forwards. (If you see what I mean).
Moving the engine one inch is a non-starter with an inboard diesel (and possibly any other inboard as well).
Weight shifting does not always work either because:
-you can't shift enough weight, far enough
-you can't move anything that weighs enough (engine compartment "full", for example)
I believe the torque effect is caused by the flywheel rotation within the engine.

I will now stand back and let someone who actually knows what they are talking about, comment.
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Old 25 April 2003, 08:48   #9
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Brian, thank you. Stu has an Optimax 150 on the Scorpion which is why I suggested moving it to starboard, but yes I agree moving an inboard is a non starter.

Out of interest (as this quite facinating) if you reverse the control box lever does the gearbox still run with the same cogs driving forward ? I am thinking about the way the cogs are machined with a curve (can't think of the correct name for it).
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Old 25 April 2003, 08:55   #10
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Obviously I dont know (because I am a pillock) but if I were to guess............
I would think that the bits which matter in the gearbox are cog wheels and it doesn't matter if they turn clock or anti-clockwise.
But hell, surely someone is reading this who actually knows?
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