seafury drives

[mobydick]

hi all

I am looking at putting twin diesels around 350 to 400 hp in a 10m rib, what do ye think of seafury surface drives?
thanks phillip

[Frosty]

Seafury are Ok if you need an agricutural sytem that you wish to antifoul and leave in the sea. May not be the case with a RIB.

They are heavy too.

[mobydick]

witch other surface drive would you sugest ? I like the shape of the seafury and the 45 deg transome idea. I am doing a few endurance record attempts soon, I want to move away from petrol to diesel and I am not gone on the bravo legs the boat will start in June.thank you
Phillip

[xrudi]

Maybe our LD SD 280-300 would be the right drive for you. A 45 degree transon is required. We have also a new propeller (see photo gallery).

Rudi
Levidrives

[mobydick]

sent email through your website ,would there be extra drag with the two rudders in the water?
regards Phillip

[Jarrod]

Dear Phillip,

I would highly recommend the Seafury drives. Well designed & manufactured, with a long track record.

[Frosty]

sent email through your website ,would there be extra drag with the two rudders in the water?
regards Phillip

Twin tunnel rudders= 4 rudders in total there is drag and alignment probs. The Flexitab drive which looks just like the levi drive has only one rudder. They have simply cut one side off.

I have recently bit the bullet and done this to my 2 tunnel rudders. Cut one off and increased the aspect ratio of the remaining rudder It put 3 knots on the top and corners much much better.

Power cat 2x250HP 14 tons 44 foot.

The drives are nothing, they simply hold the prop in the right place.

Whilst I use the Seafury props which are the sonny Levi diamond backs, I have experimented with rudders behind the surface prop. I eliminated vibration by not doing so.

Surface props by thier nature potrude a long way out of the back, having to attach a rudder as well makes it difficult.

For a twin drive boat rudders do not need to be behind the props.

[mydauphin]

Frosty,

Do you have some pics and performance data on your boat. I am trying to do similar and slowly achieving it. Rudders are a problem- went all over on them. Even thinking of a single rudder in middle of boat leaving propellers completely clean. Are your rudders offset of shaft or completely outboard
thanks

[Frosty]

Here is one of the best surface prop threads.

There is a picy of my rudders but those rudders were modified years ago. Same place though.

http://www.boatdesign.net/forums/powerboats/shafts-thru-transom-2155-8.html

With bulbous bows it is my thoughts that I get a bit of bow steer, it is for this reason I am keeping on the "larger" rudder idea.

Aspect ratio (deeper) is very performance enhancing.

Try to google up the Atlantic Challenger her rudders are forward and of course to the side of the props on the hulls. However this boat was made to do one job only and steering was'nt really one of them.


This is the Flexitab http://www.flexitab.com/eng_flexiboat.html

I have copied this one legged approach and adopted the removable rudder blade. I have also gone for the wedge rudder which I should have done years ago instead of messing with a foil shape.

I am 2x250 HP Yanmar 6LP. Hurth A 630 gearboxes with down 8 degrees max RPM 4200 ,-2 inch shaft of cutlass bearings fed from exhaust feed. 24 x 24 x 4 blade Nibral diamond back by Seafury.

3400 RPM is 20.2 knots (GPS) 35 liters per hour ( both )