You heard it here first: Low Profile "Hidden" outboards coming soon.

Of course it does.

 

do any of these propeller calculations allow for surfacing props?
an F1 guy would pay you tons of money to design a better system if you are telling him a 12" prop doing 10,000 rpm is not efficient?

 

Surface piercing props are very difficult indeed to model well, as the boundaries between air, aerated water and water around the disc are almost impossible to define with any accuracy, so you really have little idea as to what the density or viscosity of the mixed fluids is at any point across any blade. What's worse, those boundaries change with speed and wave height, adding to the complexity.

AFAIK, most of them have been designed empirically, by people building and testing and finding out what works and what doesn't.

 

thanks Jeremy
yes from my world, props are all art, every world record was made with a prop that when scanned had 3 different blades on it and no 2 have every been made the same

 

The "Outboard cruiser" exist already, I saw it last weekend. Its a great idea and it works very well: http://www.boattest.com/boats/boat_video.aspx?ID=2752

 

That is a great idea when it comes to space-saving and simplicity, but I have this feeling that the bill comes in when the seas get choppy...

 

How is this new? What I see is 10' of boat dedicated to motors and platform. How is this saving space? So the motors are covered. Home builders have been doing that for decades. At over 60K for the engines it ain't cheap either. Like Daiquiri, it would be good to see how the engine cavities would react to pulsing waves. It may be a good idea but the ad copy makes it sound like they invented a game changer.

 

Thats how the OMC Sea drive came in being which had many brilliant engineering advances.

 

Interesting...

1)Great minds think alike (lol)

2)I wonder if they had kick up issues since as I mentioned it requires the whole mass to be lifted somewhat, not just rotated. Thats why I mentioned a I/O style prop. Looks like most boats it was used on didn't have much "kick up" opportunities and were more deep water.

3)Now that improved CAD/CAM has made it cheaper to crank out whole new designs, maybe now we could start with blank sheet of paper.

4)I want something that is 110% compatible with existing outboard mounting regimes (no new holes drilled!!!). The only diff the user will notice is less weight up high and more stability, and no big powerhead in sight....but instead just a nice big sturdy and stable "swim step" platform jutting out from transom about at waterline.

 

I was unfamiliar with the OMC Sea drive so I had to look it up.

Why did it not become a long-term success?
What were the disadvantages?

 

Used thirsty old-tech engines for one thing, these would have returned fuel figures somewhat inferior to petrol sterndrives of the era.

 

I see, thanks. Isn't the concept still a good one?

Would an updated/optimized version be a success?

 

As I recall they used the old cross-flow V6 and V4 engines, which would have been far inferior to a modern type such as e-tec in mpg terms. Other than that, it is a sound enough principle.

 

thats actually rubbish as the gain in drive efficiency fixed that.
25 Bertram with 1.6 sea drives performed as the boat with 2 170 sterndrives.
4 stroke and 2 stokes from that era used the same gal/hr/hp so the outboards had a gain and a bit less weight as you can imagine and a large gain in cockpit and a gain in useable fuel range

I main think that killed it was the boat builders not understanding that as the drive was so far aft needed to be installed much higher than any other so many got installed too deep.
Unfortunately some ***** at OMC designed it with a the trim motor protruding into the transom so lifting the drive created a shift of a hole

 

well yes, used the technology at he time