FlexiTab drive

[LostInBoston]

Does anybody know anything about the flexitab surface drive?
http://www.flexitab.com/

I believe it is used on the Donzi P1 raceboat. Anybody care to ballpark the cost in USD?

[Pericles]

Send them an email and ask who distributes the equipment in the US. info@flexitab.com

Pericles

[Frosty]

I have a sonny levi type of drive. I intend to cut half the tunnel off leaving only half the tunnel to have the rudder. The flexitab has exactly this and well,--not so surprising is that it was a levi design.

I have always been concerend about the drag of using basically 4 rudders and the obvious alignment problems that would go with it.

Looking at the flexidrive in the picture below it seems to be a simple modification with a removable stainless bolt on blade rudder with a higher aspect ratio ( big words for longer).

I would be interested to hear any opinions on the use of 4 rudders compaired to two by chopping the tunnel rudder?

As you can see in the picture bottom right I intend to cut the inner leg off and lengthen the other.

I shall cut the inner leg off so as to keep the hydraulics in compression.

[masalai]

Frosty, Have a look at the flexitab site, seems they have adopted inside for "rudders" - done in conjunction with "Sonny".

[Frosty]

Im sorry mas I don't understand what you mean?

[masalai]

In your prev post you said you would remove the inner leg of the tunnel rudder, in the pics from the flexiTab they have the half tunnel rudders with the outboard part removed. Hang on I will post edit

http://www.flexitab.com/eng_flexiboat.html - here

[yipster]

first available slow turning surface drive props i see!
was thinking having those tilting props on a sailboat
surface drives on a sailboat, any other crazy ideas?

[Frosty]

Thanks for that mas Infact thats the first real picture of a reall drive I have seen. I have the web site on my favourites and thought I had seen every picture!!!

The reason I wanted to cut of the inners is to keep the hydraulic tie bar in compression. I had this problem before that took weeks to solve where the hydraulics when not in compression would boil the oil and oil would spill out of the upper helm. I just couldnt work this out at first. This infact proves the effect of the prop rotation on the tunnel rudder.
I Changed round the whole Hydraulic line system and cured the problem. Changing prop rotation did the same thing but then I had to change the control cables round.
Although I have since fitted much larger rams since then as well I would just rather keep it that way ,---but now since I see your post,---mmm--mmm Ile have to think about cutting the outside off and reversing the lines again.

Does any one think which leg did the steering mattered ?

For a power catamaran and not the deep V in the picture I would have thought that the rudders would be better as far apart as possible?

Mas read your PM

[masalai]

Later last night, I got to thinking, (it doesn't hurt much), those screws are rotating bottoms inward, & somewhere I seem to recall someone saying cats may be best in another direction to mono's? Consider your rotation! - It appears to my un-skilled brain that the "flexboat" arrangement is to reduce screw induced rooster.....?

Frosty, I seem to have got points... Are you trying to say I get more.? Shades of Dickens!

[masalai]

Yes Yipster, but sadly designed for more horsepower than I need or could use. The assembly may weigh more than my 2 engines (500kg)?

Stand by - General Motors boss, in declaring his doubts on US recession and affirming electric cars also stated "PEAK OIL" had been reached!!!!

[Frosty]

This is what happens when you develop your own systems , you have no one to turn to. I have tried opposite rotation than normal and to be honest it made no difference exept to the forces on the rudder.

The only way I have found to move forward is make the modification you want without going so far as to make it un-reversable. If its not a success it can be replaced.
The thing is I dont have problems,--- Im quite happy with them . I just cant resist the urge to tinker and improve.

[masalai]

Aaaaah to be at the cutting edge of technology & science!

[Rik]

This is the exact reason one should go with a reputable company.

Going in only thinking there must be a cheaper way of doing things always cost far more in the end.

As for the question of cost for the Flexi Tab Drive. U.S.$ OEM is $120K.

[Frosty]

I tried to buy Arnesons. I told you once I talked to you by E mail. You told me Arnesons would not guarantee being suitable for my hull.

I made my own ,--A picture above,-- they produce a little more than the factory with normal shaft drives with 100HP less.

If you read the e mail 'slowly' you will see that I said I was happy with them but cant resist tinkering.

Again if you read slowly no one is buying a Flexitab. We are discussing the engineering of them.

I am not a Californian, I do not walk into a showroom with a cheque book and a huge cigar and shout "Gimme a god damned 100MPH boat now"

You don't think I can tinker and make modifications without exeeding 120,000 dollars? Each.

[Rik]

I never said for one to purchase Brunello's Arneson hybrid drive, nor did I say that they are worth the 120K.

I sell the original version for 1/2 that amount.

You want someone to tell you how they engineer their product so you can make it yourself.

I guess you go to restaurants and ask how they cook the food and go home and cook it yourself and then complain about the taste.

Once again, your misconceptions of what Arneson's are used upon. 99% of our applications do not have the shinny little propellers you refer to, are used upon a 100 mph boat as you put it, nor are they used upon anything near your misconception.

Sure we have those applications too, but those are only a small % of the overall picture.