FlexiTab drive

[LostInBoston]

Does anybody know anything about the flexitab surface drive?
http://www.flexitab.com/
http://www.flexitab.com/img/img_flexidrive_4_b.jpg
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 (http://www.flexitab.com/eng_flexidrive.htm) i see!
was thinking having those tilting props on a sailboat
surface drives on a sailboat, any other crazy ideas? :D

[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.

[Frosty]

Did not say shiny little propellers. I am not complaining of anything. You twist every thing any one says. Do you have any Idea how much damage you must be doing to Arnesons on this forum.

Geeeeeezuz Rik we are discussing the engineering, why and how and what for. You know stuff you don't know about.

It does'nt matter if I dont get to do 100MPH this weekend.

I have a design that follows the principle of Arneson, only the rams bring the prop out of the water. I shall use CV joints and internal rams. A far better usable drive than a fully exposed Arneson.

Arnesons are like the penny farthing of the bicycle world.

[masalai]

Oh Rik, Please make your own thread "Arneson Drives" - I promise to leave it alone for you to pontificate all you like, but dont mis-interpret others words. I think you have great difficulty in reading & understanding what is written in English....

This from Rik: "As for the question of cost for the Flexi Tab Drive. U.S.$ OEM is $120K.",

Appears to be followed by a a reasonable response being from Frosty: "You don't think I can tinker and make modifications without exeeding 120,000 dollars? Each."

implies in no way this, from Rik: "I never said for one to purchase Brunello's Arneson hybrid drive, nor did I say that they are worth the 120K." as no brand was mentioned until you pushed your item, from which I question your motive/integrity.

May I suggest in your response something to the effect "I can however supply (your product) at 1/2 that amount...." Is that what you meant? and not include the first line? which appears to be a "red herring"???:D

Line 3 - Does your organisation hold the patents?

Line 4 - most good cooks would be happy to share their recepies for personal use (except KFC & other purveyors as such)

You presenting Frosty as saying: "He has invented an imaginary problem that all Arneson hydraulics fail due to barnacle growth...."

Is not supported in Frosty's assertion & clarification: "This thread by the way was what is the best surface drive for a marine diesel, not show me some photos of an Arneson Surface Drive with Barnacle damage to a steering cylinder." and goes on to reiterate: "I would like to know how you keep your drives clean of marine growth and to know more about your self cleaning rams. Where can I find this information,-----Sigh ."

[masalai]

I am butting in because I am looking for drive system answers & as a "live-aboard" will be hauled out less frequently than each year. Not many facilities in Melanesia.

The impact of barnacle growth cannot be overlooked in my situation - ergo my interest and questions relating to the steering arm of the hydraulic actuator which is normally (at rest) under the water & subject to attack by marine growth. WHAT IS YOUR SOLUTION IF ANY?

I know not of Frosty, except that he has been very helpful in giving advice and suggestions relating to my interests. He appears to be very experienced, knowledgeable and capable. Like me has a low tolerance for "wankers", spin-doctors, those who divert the truth and behave evasively in anonymity, and others, - - who receive a persistent series of questions.

[Rik]

Then it would be wiser and more productive to stay on topic and avoid the personal attacks.

Like I stated and you did not cut and post, state your identification and occupation. I have done this openly and freely. It takes a bigger man to stand if front of the bullet instead of hide behind the keyboard.

If you need a propulsion device, you need to first declare what your parameters are.

Power, size, speed, objective, application, etc. etc. etc.

I saw your model. TALENT is a small word there as it has to be a major under taking, so why stray from the fixed torpedo that is used upon the other crafts of similar design? Jet pumps.

If you want a propeller, you can torpedo your rear sponson and put a propeller shaft coming out of it. Simple, easy to make, as well as in expensive. A rudder can be mounted somewhere.

Post a picture of your models propulsion on the model.

[Rik]

Did not say shiny little propellers. I am not complaining of anything. You twist every thing any one says. Do you have any Idea how much damage you must be doing to Arnesons on this forum.

Geeeeeezuz Rik we are discussing the engineering, why and how and what for. You know stuff you don't know about.

It does'nt matter if I dont get to do 100MPH this weekend.

I have a design that follows the principle of Arneson, only the rams bring the prop out of the water. I shall use CV joints and internal rams. A far better usable drive than a fully exposed Arneson.

Arnesons are like the penny farthing of the bicycle world.

Fost, I've asked in the past you stop your personal attacks and stay on topic. Initially it was cute, but like a puppy it quickly grew old.

I'd rather risk your negative view than risk you releasing a negative inaccurate unsubstantiated opinion on Arnesons for others to believe as truth.

[masalai]

I can't really be bothered re-typing it all again, but if you click on >members List> then click on <M> then click on <masalai> then click on <all posts started by masalai>

Or click on "masalai" in the header of this post & then make your selection. If you would like a pdf file of my current projects in development send my your email address (not yahoo etc) and you will get a reply - it is about 662.2Kb in size.

What are your personals???? PM is OK

[Rik]

I can't really be bothered re-typing it all again, but if you click on >members List> then click on <M> then click on <masalai> then click on <all posts started by masalai>

Or click on "masalai" in the header of this post & then make your selection. If you would like a pdf file of my current projects in development send my your email address (not yahoo etc) and you will get a reply - it is about 662.2Kb in size.

What are your personals???? PM is OK

Nope, lay it on the line like I have done.

The swath use a torpedo with a propeller.

http://www.swath.com/concept.htm

[masalai]

What line? - - - are you CIA or something? - I can't see what you have presented for viewing. (invisible ink).. No website, No images in gallery of your boat or your personal projects, No summery of likes/dislikes etc., (I missed a bit on that).... What is that swath stuff about, I had more imagination than that when I was six, now nearly 11 times that...

[Frosty]

[QUOTE=Rik;I'd rather risk your negative view than risk you releasing a negative inaccurate unsubstantiated opinion on Arnesons for others to believe as truth.[/QUOTE]

And what would be that inaccurate unsubstantiated opinion be Rik ????

You know Im sure you do have some worth while input that we can all benefit from. If you would just slow down and read posts properly and reply without condescending and control that huge ego.

Many here are fabricating their own drives and its very difficult to move forward when little is understood.

Its very unlikely any one will buy an Arneson from you here on this forum, you will just have to accept that you would be helping some one.

In your e mails to me 4 years ago you said that your drives can get as much as or better than 10% slip . what props were you using to achieve that.

[Rik]

What line? - - - are you CIA or something? - I can't see what you have presented for viewing. (invisible ink).. No website, No images in gallery of your boat or your personal projects, No summery of likes/dislikes etc., (I missed a bit on that).... What is that swath stuff about, I had more imagination than that when I was six, now nearly 11 times that...

Masa, just as your too busy to list your identity, search my post. Even Frosty can help you there if you need. He keeps referring to it in his replies.

Sorry to offend you but your design looks similar to the SWATH design. You have, according to your model photos, a flat bottom sponson design vs a rounded keel design. Both have small surface area to support the displacement of the hull.

Have a CFD done on your design and see what the #s say. It will determine everything else you will need in your design parameters.

[masalai]

It's just a displacement cat working towards becoming quite fuel efficient to give me a 2500 mile range at 15 knots - nearly there - 12m W/L I don't go for acronyms, use strikes me as lazy writing, (which I too, am sometimes guilty of using).

Would love to have numbers done through Michelet/godzilla but cant get those apps to work on my machine (I use "linux mint" and rely an "wine" to interpret the win2000 interface needs as michlet is a windows application.)

Other windows 2000 applications work, such as DelftShip & Free!Ship, quite well....

I have scanned most of your posts, reading many carefully - only 43, If you read 250 of mine You will know me, but you may end up scanning through 1100 to get them :D :D :D. Scan through Frosty's almost 3000 and you will appreciate his experience & wisdom..... (learn to learn from experience and be humble enough to be able to ask questions.)

This match is not a gain for you - especially as you are prone to "going off half cocked" or as septics seem to be prone to, "shoot first & ask questions later". - this leads to regular injuries of the foot & mouth. :D

You strike me as being soo full of your own self impotence (deliberate mis-spelling), Calm down, listen quietly so that you UNDERSTAND EXACTLY what is being presented to you by text-words or spoken-words. Do NOT be ready to take offence at IMAGINED insults or WRONGS. Do your homework before opening your selling mouth and you will sell more by being recommended more often. Advice your mother & boss should have given....

Best wishes for your future

[Rik]

Masa, within my first 7 post on this web forum I had already established who I was and what my web site is. I've asked you and Frosty to do the same, but neither has yet to come forth.

I am not hiding, nor am I full if Bravado for nothing. I originally stated a response to Frosty and then you and him tried a game of gang bang, but instead of facts you used personal attacks and misconceptions.

Not a wise way to make ones point.

Respect is earned both ways. The number of post one has does not reflect anything other than the amount of free time one has, absolutely no correlation to anything else.

You have not been able to spot my information post yet apparently, so I am starting to think your not a native English speaker.

You are going to have to hire a professional to do your CFD analysis. It might just turn out to be the least expensive and at the same time most valuable information you will ever have on your design.

[Frosty]

Again Rik I have to correct you. You did not establish yourself as who you were ,it was I that spotted the enthusiasm for Arnesons and put 2 and 2 together and challenged you that you were the Rik that I had talked to at Arnesons some 4 years back.
Why you want to know about me I cant imagine I am no one, I have no web site. I speak for myself ofcourse.
Ille bet your a real foot in the door ,never give up, sparkling white teeth salesman. Although you may have a wall of salesman of the year certificates perhaps you should consider that we are a different culture and your methods are completely useless with us.

Im sure that there is a more genuine person underneath. I will try a little longer to meet him, but its getting a bit -- you know.

[Frosty]

Dear Brunello disregarding the previous rubbish submitted above I would like to tell you of a little modification to a sonny tunnel rudder I did recently. After studying the Flexi tabs very unusual one legged tunnel rudder I bit the bullet and cut my sonny rudders to similar.

I had often wondered of the drag associated with the (4) rudders and the consiquential misalignment of them.

The results were nothing less than incredible. Firsly I noticed a more positive response whilst manouvering from the beach under 4KTS. The normal cruising of 17 @3400 jumped up to 19.8 and a vast improvement in cornering where as before the boat would slow. With the one legged tunnels she did not and responded to a tighter turn with less rudder angle slowing to only 17KTS.
I notice that you use the long leg to the center of the hull. I suppose that is to keep the rudder in some water in deep v hulls, but I wonder if there is any rotation of the prop reasons?

Due to the configeration of my hydraulic steering system and the hydraulic tie bar I had to use the long leg on the outer side. Being a cat I don't suppose there is much difference is there?

[marshmat]

Hey Frosty,

It's interesting to see results like that from moving to the one-legged tunnel rudder.

Which way do you have your props spinning now?

On the Flexidrive, it looks like they always have the prop spinning so that the blade that's in the water is moving towards the rudder. I would guess this is somewhat more effective than having the bottom blade move away from the rudder, which I think would tend to aerate part of the rudder face due to the air that gets drawn in with the upper blades as they enter the water.

It would be interesting to see a comparison between mounting the asymmetrical tunnel rudders with blades pointing inboard versus outboard of the props. Your cat looks like it has more-or-less symmetrical hulls, so I'd think the only difference you should see if you switched the side of the long blade would be the difference (if any) due to prop rotation....

[masalai]

Hi Frosty and welcome back :D:D:D:D see you in Drivel as soon as I catch up - only 4 posts since I left to go to church :D

[Frosty]

Hi Marsh,--I very exited about it because I have a bit to go yet in so much as there was a tendancy on my part to be conservative with the cutting and I can cut some more off to get the parasitic drag to zero on the unused leg.

I also increased the aspect ratio of the rudder blade and made it removable. I did this on both sides, now that the cut was successful that part can be totally removed. I also went to a lot of trouble to make a wedge rudder as perfect as possible.

This brings in your point. My rotation is as normal, ie- right is right or to be correct STB is right. I was hoping for a little discussion with Brunello on exactly this point.

I agree with you about the rotation being better towards the rudder but for a different reason,--I was thinking that the pressure front from the rotating prop would be better managed if the rudder was there to deflect thrust rear. But Arneson and Flexi series 2 and 3 don't have such tunnels along with many others.
It is just a gut feeling that I have.

When I first fitted the drives I fitted the props the other way round and have to admit to feeling no difference in any way.

Before cutting the rudders I tested the boat with no rudders at all. This resulted in not so surprisingly being unable to steer the boat at all meaning I could not hold throttles open long enough to get onto the plane. I was expecting to be able to steer with throttles,--not so.

I am now unsure if the boat could not get on the plane because of the throttles not being held open long enough or the lack of the tunnel rudders giving some effect I am unaware of.

[masalai]

Is your top speed still the same or where?

[Frosty]

Well I assume it is much more. If it was 17 at 3400 and is now 19.8 at 3400 and the engines will pull 4200 I suppose it could be as much as 24-25 ish.

Im getting a bit out of my depth here but it appears to have brought the prop slip from 28% down to 16%. I would imaging to have increased economy also.

[masalai]

Speed freak - I think my current option will do less than 10knots and more? with all sails in a gale? -

[Frosty]

Damn I was hoping some one would have wanted a conversation on tunnel rudders and propeller rotation. Personally I think It very interesting, their must be something in it with a surface prop running close in a tunnel.

Would there be some advantage to the rudder being on the entry side of the propeller blade or the exit?

[masalai]

Well, what is your take - I was looking forward to something upon which to comment? - - seeing as how I am still a learner in this matter.... I feel both views expressed so far on location of remaining half rudder have merit and end with the same result....

How about taking your boat out fro a run and post a list of engine speed and speed through the water.... and gut feel on turning and handling response ?

[Frosty]

Oh cripes mas --take the boat out!!! Ive got to take the satelite dish off first and then all the plants on the dock. The missus will go bannanas.

Ille have to dive on it and clean it up,--maybe next year.

Once the good weather comes in (thats not today) I intend to beach it again and go the whole nine yards and cut some more having just the one rudder in the water.

At the moment I can unbolt the rudder blade and simple bolt it onto the other side of the tunnel. This is achieved with 8 countersunk high tensile 6 mm bolts. So Ide better make my mind up wich leg gets the rudder blade.

As it seems, the experiment although very labour intensive is a success it is unknown what the effect would be other wise.

You are aware of course that changing the rudder blade side would mean dismantling the hydraulics to accommodate for the hydraulic tie bar to be in compression between the rudder rams. It can be done --ive done it but it means all the pipes off from upper and lower helms and re bleeding. Not a nice job.

[masalai]

Why not make another rudder that has both sides removed to just above the water flow when you are sort of planing so it still gets some resistance from the upper half of the prop travel wash but not the drag? would that work?

[marshmat]

Oh cripes mas --take the boat out!!! Ive got to take the satelite dish off first and then all the plants on the dock. The missus will go bannanas.
Good point Frosty ;)

It would be interesting to discuss the issue of tunnel rudders and prop rotation in more detail. Exam season is about to hit and so it'll be a couple of weeks before I can really take a good look at this though.

[Frosty]

No problem,-- Ill wait.