avoiding cavitation
 

Hello Everyone
Currently testing out my BJ26. Once again the system is 14 cells, hydra 120, 7xl, and a 34-37 prop currently.

I tried a proboat prop(link below) and I got about 35 mph w/temps a little on the high side. (I really should use 12 cells, 14 is turning out to be kinda high)
http://www.proboatmodels.com/Product...ProdID=PRB0150

I then tried a carbon Y535 (miss vegas prop) and I got a ton of cavitation. The midline of the prop was about 3/16 inch above the bottom transom edge and neutral angle.

To avoid cavitating should I simply try different strut heights and angles? Should I angle/lower the strut a little bit lower w/a Y535?

RE: avoiding cavitation
 

Getting the prop deeper in the water may help BUT it may also cause the system to run hotter too. I think you just need to find the right prop for the hull. Does it cavitate just on take off and then hook up and go fine? I have had some custom made props that would cavitate real bad on take off and then once the hull was on plane it was fine. I have also had some props that would cavitate any time I let off the throttle. On a 7XL with 14 cells I am not sure I would trust those carbon props, you might want to get a Octura metal prop instead. That is a pretty hot setup even on Nimh cells in my opinion, you might be better off with a 9XL and a larger prop which will also help with the cavitation.

RE: avoiding cavitation
 

If you mean aeration rather then cavitation of the prop, I would first look at the system you are trying to run. A 35mm prop is a bit on the small size for a cat hull of that size. Most run props over 38mm.

Aeration is normal for surface driven props. If your hull can get on plane I wouldn't worry about it too much. Once it is there keep it there. Getting more prop in the water will help but increase your heat which is what you are trying to avoid. I agree with Raydee that setup is pretty hot, going with a 9XL would be much better suited in terms of dropping heat and allowing a larger prop to be used.

Ryan

RE: avoiding cavitation
 

That's intresting. I have yet to run my cat but I have expected that take off cavitation would not be a broblem because the prop would be completely submerged. I have this problem with the SV27 but there are wierd flow patterns around the transom and the top blade is out of the water pretty fast. With a cat I'd expect that this wouldn't be a problem. That is a small prop for a 26" boat IMO.

RE: avoiding cavitation
 

Thanks guys.

I'll try tweaking w/the strut for a little first and then I'll see If I can get a 9XL or 8XL.
I'll try using 12 cells too.
I forgot to say that the boat wouldn't get on plane, it would just keep on cavitating(w/a CF Y535).

If I use a 8XL or 9XL what would be a good prop size? 40-42mm?

RE: avoiding cavitation
 

Or what about a prop size for a 10XL w/14 cells? Around 42-45mm? Cuz I got one hanging around that turned out to be kinda small for my sport 40.

RE: avoiding cavitation
 

keep your motor and try an x438. It might be a bit big, but it should work.

Here:
http://www.offshoreelectrics.com/pro...rod=octsb-x438

RE: avoiding cavitation
 

42-45mm would work for a 10xl. 38mm will be too big on a 7XL and would not work.

Ryan

RE: avoiding cavitation
 

It's really hard to find smaller props for 3/16" shafts. This should tell you a little bit about your motor selection.

RE: avoiding cavitation
 

It's easy to make smaller props out of big ones:D

RE: avoiding cavitation
 

yes and it is way too difficult to make bigger from smaller ones :D :D