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Old 06 March 2018, 03:51   #11
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,422
>>>Thundercats definately run short shafts check the specs

Yep my thought while I chomped my toast this morning. Folks tend to take dramatic pics of them catching air and it's quite hard to find one running fairly normally to demonstrate how the design works Lee. But the one I've attached below shows fairly well that in normal running their central "deck" the transom is on plays no part in contacting the water hence the cav plate relationship to the deck is nothing to do with getting the prop in the right place or best shaft length.

>>> SIB power boaters who want to thundercat

You can't Thundercat a SIB... different beasts completely.
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Old 06 March 2018, 06:50   #12
Roflhat's Avatar
Country: UK - Scotland
Town: Isle of Lewis
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 685
Definitely short shafts on thundercats...
If you try a long shaft you either have the engine 5" too deep in the water and the boat will handle terribly and be slow with too much drag, or if you run the engine 5" up on the transom you'll have an excessively high centre of gravity and potentially roll the boat during high speed turns.

The cavitation plate is roughly in line with the bottom of the hijackers on a thundercat

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Old 06 March 2018, 12:30   #13
dubrus's Avatar
Country: UK - Scotland
Town: Glasgow
Make: Ribcraft 6.8
Length: 6m +
Engine: Suzuki df200
Join Date: Jun 2010
Posts: 2,364
I tried my long shaft on a suzimar sib and I thought the transom was going to fold into the water if you went near the throttle. I figured it was due to the engine but maybe wasn't enough pressure??....too late to find out as the sib went ages ago.
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Old 06 March 2018, 17:25   #14
Country: UK - Wales
Town: Cardiff
Make: Avon
Length: 3m +
Engine: 2 stroke
Join Date: Aug 2014
Posts: 921
Originally Posted by Lee1 View Post
, my post was how I keep the prop in the water planning or wave jumping at 30+knots by having the extra 5 inches length of a long shaft over a short shaft.
Iím sure you appreciate/the extra 5Ē but I think you kind of missed the point of wave jumping there..... drop 300 horses in a 3m hull and a negative shaft length and try wave jumping pushing 50knts and youíll know what I mean......

Having fun and going fast arenít the same, maximum thrust & minimal drag doesnít make for exciting pictures.....

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