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joseph m. hahnl
05-24-2005, 03:31 PM
has any one ever seen a donzi with a anti cavitation plate?

Sam
05-24-2005, 03:46 PM
All IO's and outboards have cavatation plates. Are you talking about an after market "Whale Tale" :confused: .

Formula Jr
05-24-2005, 03:48 PM
They all come with an anti-ventilation plate if its an outdrive. There is no such animal as an anti-cavitation plate. Do you mean the whaletail attachment some people put on drives? This does nothing for a donzi but slow it down. It does have a place though for people that want to cruise just past planning off. They act like trim tabs. Really old guys, with baggy grey trousers and hats with fishing flys in them, use these. :biggrin.:

joseph m. hahnl
05-24-2005, 03:54 PM
after market "Whale Tale" :confused: .

Yes: there is also a slightly smaller style called SST hydrofoil

joseph m. hahnl
05-24-2005, 04:32 PM
This does nothing for a donzi but slow it down.. :biggrin.:

are you talking fact as in you have seen one tried and it actually slowed it down.
as was stated all lower units have cavitaion plates. what bolt on's are for is for when your prop rides high in the water it gives it more to drink. they help keep the prop from slipping"cavitating" which i beleive is the root of porpoising, and chine walking>
ps: if one does'nt exist i'll make one and then there will be such a thing called an anti cavitation plate:bonk: .

joe

MOP
05-24-2005, 04:53 PM
The prior owner of my 16 had a Dolphin on the drive for about a week, when he would trim up at speed the stern took a dive and the boat slowed down. Trim tabs are the way to go especialy on a 16, you will plane faster, eliminate porpoising and be able to handle rougher water. Another plus is being able to level the boat side to side no matter where a Lard Butts sits!

Phil

MOP
05-24-2005, 04:56 PM
Ooops! Forgot another real biggy! When you are in tight quarters these V hulls tend to wag from side to side requiring a lot of steering effort, with tabs all you do is put them in the full down position and the boat tracks DEAD straight. But don't forget to raise them when you hit the throttle!

Phil

gold-n-rod
05-24-2005, 05:23 PM
Ooops! Forgot another real biggy! When you are in tight quarters these V hulls tend to wag from side to side requiring a lot of steering effort, with tabs all you do is put them in the full down position and the boat tracks DEAD straight. But don't forget to raise them when you hit the throttle!

Phil

Now I'm confused. On my 24' cuddy, I get the same effect of eliminating the wandering, but when I throttle up to planing speed, the tabs stay down. It comes to plane faster. Upon the boat breaking over, I raise the tabs and then trim out to the perfect cruise.

Are you saying that "tabs down" won't aid my 16 Classic to plane?

If I ever get a nice weekend, I'll be able to experiment, but in the mean time, I'm very curious.

The Hedgehog
05-24-2005, 05:35 PM
My father has one on his 16. It elminates porpusing and does not really seem to slow it down.

I am trying to convince him to take it off and use tabs. Once the remaining performance mods are implemented I think that it will be a liability.

boxy
05-24-2005, 05:36 PM
Randy your 16 doesn't need any help to plane off, therefore not raising them will only slow you down. Your 24 needs help (power/weight ratio) to plane off, therefore the tabs help get you on plane faster....
If the actuators were fast enough, full tabs down, then full tabs up on your 16 would probably help it plane faster, but it would happen so fast it would be tough to tell.

Formula Jr
05-24-2005, 06:04 PM
All lower units have anti-VENTILATION plates. These Whaletales are just cheap trim tabs. I've put them on boats before, but for their stated purpose. They are not a perfomance item. They will not increase speed or do anything other than let you Cruise just past planing a little better than without it. We have had this conversaion before on this board. The whaletale takes 2-3 MPH off top speed. I am not saying they are good or bad. But they won't make you go faster. If you don't care about top speed, these make sense as they are very inexpensive. Yet, real trim tabs give you the option of list control and you can pull them up if you want to go fast. Cavitation is the low pressure boiling of water at the front of the prop. The plate on lower units isn't there to prevent this. It is there to keep air from being sucked into the prop. The plate creates a high pressure area over the prop. Most props suck, but a few push. If you are running a surface piercing prop, and a high X, you don't even need this plate, if you also have tabs. Most of us here are running four point. By that I mean, alittle of the keel: Point One, On the tabs, Points Two and Three, and the plate of the drive, point four. The boat doesn't matter after that.

DON N.
05-24-2005, 08:03 PM
Look Under Registry Shahbas 19' "wa" "lo" Is That A Cavatation Plate ?

MOP
05-24-2005, 08:20 PM
Qoute::
Now I'm confused. On my 24' cuddy, I get the same effect of eliminating the wandering, but when I throttle up to planing speed, the tabs stay down. It comes to plane faster. Upon the boat breaking over, I raise the tabs and then trim out to the perfect cruise.

Are you saying that "tabs down" won't aid my 16 Classic to plane?


No way tabs improve planing on all boats some just being there and some need a bit of down, on a slow planer you can run them down quite aways and bring them up as it rolls onto plane. But with a 16 in the full down position and full throttle it is scary the bow comes within inches of going under a real freaky feeling. I had the small Bennets on my 16 it had a lightly juiced bored and mild cam V8 and really did not need them to plane even with passengers. With the tabs full down when you nail a 16 it jumps then tries to dive, I gave a few the oportunity to stain my seats!

gold-n-rod
05-24-2005, 08:38 PM
Thanks, Boxy and Phil. Seems I have a lot to learn about driving my 16 vs my 24. Good thing I have all summer.

:rlol:

MOP
05-24-2005, 09:26 PM
Thanks, Boxy and Phil. Seems I have a lot to learn about driving my 16 vs my 24. Good thing I have all summer.

:rlol:

First time I screwed up and forgot the tabs I near S#(% and they heard me scream all the way back at the ramp. Tabs will be one of your very best mods!

Phil

gold-n-rod
05-24-2005, 09:39 PM
First time I screwed up and forgot the tabs I near S#(% and they heard me scream all the way back at the ramp. Tabs will be one of your very best mods!

Phil
Oh, tabs I have. That's dfunde who needs the mod. I already have 'em, plus the indicators and auto-retract. Good thing for a 50 yo old fart who has a forgetfullness impairment (not that anyone here can relate......) :bonk:

MOP
05-24-2005, 10:03 PM
Oh, tabs I have. That's dfunde who needs the mod. I already have 'em, plus the indicators and auto-retract. Good thing for a 50 yo old fart who has a forgetfullness impairment (not that anyone here can relate......) :bonk:

You are a Pup truely not eligable for the Old Farts Club! There are a couple of of us that hold that title! We have the best fun behind the scenes!

MOP

gold-n-rod
05-24-2005, 10:16 PM
You are a Pup truely not eligable for the Old Farts Club! There are a couple of of us that hold that title! We have the best fun behind the scenes!

MOP

I dunno..... my dreams are dry and my farts are wet...... don't I qualify???

joseph m. hahnl
05-29-2005, 08:34 AM
[QUOTE=Formula Jr]. These Whaletales are just cheap trim tabs. whaletale takes 2-3 MPH off top speed. I am not saying they are good or bad. But they won't make you go faster. Yet, real trim tabs give you the option of list control and you can pull them up if you want to go fas

Cavitation is the low pressure boiling of water at the front of the prop. The plate on lower units isn't there to prevent this.


cavitation is air bubbles in the path of the prop.and the prop spins with no resitance as a tire on water is to a prop to air. you missed the point the trim tabs are to maintain an attitude on the hull . the "ventilation plate" is to keep
air out of the prop> the problem is not that the're cheap trim tabs that is not the're purpose at all it is a coincidence this effect takes place. you failed to consider these are generic plates and are quite large. with modification i,m sure you could eliminate the trimming effect and keep the prop wet with the
hull at minnimum surface contact.

joseph m. hahnl
05-30-2005, 02:58 PM
They all come with an anti-ventilation plate if its an outdrive. There is no such animal as an anti-cavitation plate.. :biggrin.:

I use to make up words too. the whoma ga? fadush!!! . ive yet to see any thing called an anti ventilation plate. you almost had me goiing!!!!
is that kinda like rubber spinners you put on your car?. sorry: i could'nt resist!!!!!!!!!!!!!!!

Last Tango
05-30-2005, 06:34 PM
My first Donzi was a brand new 1999 Classic 16 with the 190hp V6 and Alpha drive and trim tabs. I was not a very good performance boat driver then but I will tell you that the combination stated was a handful for eveyone. Boats' top speed was 55MPH indicated. I was not happy with the sensitivity of the drive trim to control porpoising, etc. Trim tabs had ZERO effect on this other than to drag in the water. I spent time reading all the purported "expertise" on this board, and then decided to just go ahead and see for myself. I installed the large black plastic wing on the outdrive. All of a sudden the boat was immediately far more controllable as to anti-porpoising, far smoother in all aspects and STILL ran an even 55MPH indicated. My friend with an identical boat and identical handling problems in identical water, put one on his boat. Lo' and behold he had the same improvement in handling and the same exact speed numbers. Now all of you "experts" can say what you want. I endorse this addition for any Classic 16 with V6.
My 2001 18 does not need a foil on the drive for control. And on this same 18 I have almost never needed the trim tabs in any other position than full up.

MOP
05-30-2005, 09:43 PM
Mark it worked on your V6 but certainly did on my V8 16 made the azz end dive at speed when trimmed up, maybe the added weight of the V8. I totally disagree with you saying your tabs did not stop the inherent problem with all 16's low speed porpoise problem, like you said you had little experience, I feel you may have needed more time and a few tips on tab usage, if your tabs were dragging they were not installed correctly. Do a search there have been several posts by more then a few knowledgeable people on how to properly mount them. And no I am not saying that tabs are a cure all but when used properly there is no other item that can control the attitude of a boat better then trim tabs, also unique to deep V's tabs will allow the boat to track straight in tight quarters where as one without wanders like crazy. There are very few boats that do not benefit from trim tabs, I have installed a many sets, every single customer said tthey were happy some damn near estatic. No purported expertise here just nearly 40 years of being a marine mechanic, shop forman and a factory trained tech, no hobbyist here I have damn sure worked on a more then a few.

MOP