Cavitation Plates

[GTR]

Hi Everyone,

Can anybody explain what the cavitation plates on lower legs do?

Do they act like down elevator on a plane holding the nose down?

Do they provide a place for the water pick-up?

and does size matter(not a question for the ladies LOL)

GTR 8)

 

[duc]

the cavitation plate keeps the prop from cavitating. (Is just reving in a mixture of air and waterbubbels without adding forces to move the hull forward)

Sorry for my bad english....

 

[ggillman]

Oscar,

Your English is much better than my Dutch

Groten, Gene ;D

 

[Kris Flynn]

GT

Nice to see you finnally able to post

just about all OB i see use them to also position the water pickup in a good spot...and id say they would also act like tabs to control the rid angle of the boat

but i dont know much more about them

Kris

 

[GTR]

Hi all,

I guess they should be called anti cavitation plates, but if they stop cavitation why don't full size outboards use them? why aren't they used by inboard driven models? and as the propellors are surface driven they operate in air and water don't they?

Has anyone actually done any measurable research or are we conditioned to having them on the outboards?

The point ZI meant before was when the hull is at full speed and planning the cavitation plate is well above the water surface and may be contributing drag to the hull.

Does this mean overall that we should only run subsurface propellors or is cavitation just the phase of drive (or lack of) that the motor experiences before the prop actually bites?

GT ??? :

 

[ggillman]

Hi Guy's,

The correct term is "Anticavitation Plate" All the full size outboards have them, just above the prop, there is also add on's to enlarge the size of the plate so the hull will trim out faster. The occurance of cavitation on the full size outboards is when the RPM of the prop exceedes the forward momentum of the hull resulting in blowout or cavitation of the prop, usually fixed by lowering the engine height or trim, or changing to a prop with more pitch or larger diameter.

Gene ;D

 

[duc]

I guess you are right about that Gene!! But stil.....

(btw did you see mike's action on the dutch xtreme powerboats forum?? I guess he has bougt a translator from dutch to engish. he understands allmost everything )

cu

Oscar

 

[GTR]

Hi Guy's,

Wgat prompted the question is that the Mercury Champ outboards used in 1:1 scale don't appear to use a cavitation plate like ours do. I wondered about their value when the majority of people run set-up surface drive like full-size.

GT 8)

 

[ggillman]

Oscar, that does sound cool, I will check with Mike and see what software he is using,

GT, I am having a hard time following ya here, you really cant compair the two, because a surface drive strut and rudder has a fixed thrust point, the rudder changes the direction and the outboard has a variable thrust point, the prop swings with the unit, changing the direction,

As far as the Mercury racing outboards, the one's I have seen

have a anticav plate, but it is much smaller than the stock outboards.

Here is a link, click on racing, products and assc, race outboards.

The very small anticav plate is just under the outlet for the exhaust.

Larger on the 2.5 EFI Drag race version

http://www.mercurymarine.com

Gene ;D

 

[GTR]

Hi Gene,

My point was when the hulls are travelling at full plane the 'cavitation plate' is well above the water and so cannot have any effect on actual cavitation. The other element to the query was if 'cavitation plates' are necessary why don't other surface drive models use them as they certainly suffer from cavitation.

I guess I get back to my original point 'are we conditoned to having them?' and has anybody done any research on there effect?

GT :-

 

[james simpson]

all full size o/b that are submerged have anti-cav plates. I beleve they are compleatly usless on a surface drive once they are on plane. I have seen some modified K&B with out them and this allows you to mount bigger props also. So to answer your question, Yes they are just a throw back to when submerged drive was popular. (I belive in my humble opinion)