Shafts thru the transom?

Has anyone tried this? Maybe with struts on underside of swim platform W/ conventional trim tabs and rudders?

 

Instead of Surface Drives?? Never heard of it..... You might have a problem with cavitation and would possable need surface props. That is alittle out of my league knowledge

 

If cavitation could be solved w/ surface props, what other issues would be involved>

 

Surface piercing props would not work behing a strut . The eddies formed by the strut would interfere with water flow. Look at the design of all surface drives; they have a streamlined bottom. A tunnel drive uses standard propellers and shafts. They are, however, tricky to design properly.

 

And Gonzo saves the day!!

 

You mean like this?

Nope.

It won't work!

Cheers!

 

In Fact

It runs terrible - doesn't get much over 40 knots at 1900 rpms outta twin 700 Hp turbo Cats.

he he he

Cheers!

 

How about the strut being behind the props hanging from the underside of the swim platform?

 

The surface drive has a structural tube that holds the shaft bearings. If you build a structure that does the same but has more drag and creates turbulence, the performance will be less.
The size of a strut that holds a 3" bearing is huge. How about the rooster tail? Surface drives push a large amount of water up; it is inherent in the design of a surface piercing propeller. It would hit the underside of the platform. I think that if you want to build a drive system, a more standard design may be better.

 

The question that hasn't been asked, of course - is why do you want to run shafts thru the transom?

 

Will, I was trying to get the advantages of surface drives: fuel economy, speed, shallow draft, yada, yada, without the expense. Trying to think outside of the box because of budget

 

Will, I was trying to get the advantages of surface drives: fuel economy, speed, shallow draft, yada, yada, without the expense. Trying to think outside of the box because of budget

 

Surface drives don't give you economy but high speed performance. A set of balanced matched propellers for 1000 HP cost about $20,000. That would buy you a lot of fuel.

 

yep - sounds like a case of false economy to me to. Cheaper to simply buy an off-the-shelf type system and get out and use it - far less risk of building an expensive failed experiment too....

 

Is any one familiar with the Dan Arena Surf Drive? Dan Arena and Howard Arneson were designing a surface drive together prior to going their seperate ways. Howard Arneson decided that a surface drive needed to be able to trim and steer and Dan Arena thought it needed to be affordable to the masses.
Dan, who by the way also built ArenaCraft boats, has long sisnce passed away, but his son runs a marine supply store in San Rafael, CA. There are a couple of ArenaCraft boats with the surf drive setups on them there as young Dan restores the old boats.
They were not much more then a prop at the transom. Stuck out a little and had the rudder behind the prop. No trim or movement of the shaft at all.
I'll see if I can take a picture of one this weekend and post it here.
Dennis