Cavitation Plates

[GTR]

Hi Guys

A new question - I have noticed that quite a few of the K&B 45 OBs have enlarged Cav plates on them. Can anybody explain why? What are the benefits - real or imagined.

GT B)

 

[GTR]

Bump

With all the experts on this board does nobody have any input? :blink:

 

[Tunnelbill]

Well GTR,

I have run them on my 7.5's. They make the boat faster,LOL . If you get them to large, it will lift the back of the boat in the turns and you spin out. I have no idea, Just because they look COOL... TB

 

[boaterbill]

Keeps the nose down. Works for me. I also bend the end down. Don't get too crazy with the bend or will pick up rear too much. See one in the back of my Leecraft in the post "Whose got pic of there boats" in General RC boating just about the end of the posts #12. Also added deflectors inside the pickle forks on each side. Got to Keep that boat down the Nelson is awsome.

Bill

 

[TimD]

Here is a pic of Bill's nelson and the large cav plate.

 

[[email protected]]

Gary,

Yeah the bend works good. Funny you posted that because my Sundowner has no Cav plate. Check this out.

 

[boaterbill]

Thanks, Tim.

Rodney,

I have no plate like yours in my Prather outboard with turn fin same as yours, it works.

Bill

 

[snowdog-2112]

Here's a thought I haven't seen addressed. Has anybody ever run an outboard without a cavitation plate? I know the full-scale guys don't but they can adjust their height on-the-fly so it's not needed. Any thoughts or experience?

One downside to running the cav plate is the loss of roostertails that outboard tunnels are famous for and personally, I miss them.

Snowdog

 

[hg-md]

refering to an outboard in general-

A better term for the item you refer to would be an "Anti-ventilation" plate. The principle of it is to prevent air from being sucked into the prop from the surface. This is especially important when accelerating from a stand still or a slow movement. Once on plane, the prop will be piercing the surface and the plate is no longer in effect. These plates have another big misconception about them. They are not a planning surface, nor are they intended to be. They can effect the running characteristics of a boat, but only at very low speeds. Once again, when on plane, they are well out of the water.

 

[Kevin_R_Clark]

I am sure you will get some feedback, so here is a little. The spray from the prop hits them at speed and that most certainly will affect things.

 

[Kris Flynn]

I know of people who have run without them (Dick Crowe for example) and said they didnt affect it much...i know that my electric outboard without the caveplate cavitates alot on the start before the prop 'bites' but once it is going it throws a nice rooster

 

[snowdog-2112]

Kris,

How "long" does it take for the prop to bite? If it's not too long, I have an extra lower unit I may test this with...I LOVE those roostertails.

Snowdog

 

[Kris Flynn]

if you have an extra lower, i say go for it but on the other hand i dotn know if this cavitation was caused by not having the caveplate or because the prop was huge (48mm) or anyhing like that.

I also think to get the rooster you need to trim the motor out (positive)

 

[snowdog-2112]

Positive is cool but blowing over ain't! :angry:

 

[Kris Flynn]

just add more wieght to the nose

 

[Kez]

I had the same question about the cavitation plate and posted a thread a while back.

My Webpage

I have since tried cutting the plate off one of my 3.5's. Without any trim changes (and same prop, everything etc), the tunnel definitely ran looser and more prone to blow over. Yes, the rooster tail was a lot more visible.

I suspect the cavitation plate, although well out of the water when up on plane, still generate some lift (and drag) from the prop spray. I guess with a larger plate the effect would be more pronounced.

Kez

 

[Ron Olson]

From my experience with full-sized boats (I had a Bass boat), the small stock cavitation plate didn't allow to get the boat up on plane as fast as it did with an aftermarket add-on that I installed. We really don't have that problem with our R/C boats. One of the new members in here, THE CAVITATOR installed a modified plate on his 7.5 tunnel and the roostertail went down and it handled much better. His mod had a larger plate with halved tubes going lengthways curved down to help direct the water flow. You'd really have to see it to get what I mean.

 

[boaterbill]

It's back to the misterys of boats, what works on one boat does not necessarily will work on another. Test, test , if it works for you go for it. That is one of the things that keeps me going in boating, when I think I know it all, I really don't know much, because someone or myself is always experimenting and making or not making something thing work.

Bill