[MHml] horsepower & sleds

[brian eiland]

So the durajet is more efficient?
Bill
  

Durajet was developed by evinrude for the seals and the likes because they
could not get a rib  up on a plane with men and equipment to much power lost
from the tips of the props. they inclosed it with a tube and the problem went
away. plus no side thrust from the prop
Mike
___________________________________________
Brian responded:
Durajet is not more efficient. It was a solution for relatively ineffective
'small dia prop' outboards to develop more low end thrust. Plus it offered
protection to the Seal guys in the water.

At the upper end the extra drag of the shrouded prop would cut into
performance, just as does a tugboat Kort nozzel.

Cut down on the prop revolution speed as was done with the four-stroke Yamaha
9,9 hi-thrust units (lower gear ratio) and turn a larger dia prop and the
thrust gets better.

As I mentioned earlier there are some interesting possibilties to make 'jet'
units more efficient. They will be coming. 

Meantime I'm fasinated with the latest 'rim-drive' possibilties 
<http://www.yachtforums.com/forums/technical-discussion/3961-rim-driven-propellers.html>


Brian Eiland

beiland at usa.net
www.RunningTideYachts.com
distinctive expedition yachts