New DIESEL outboard.

tell us why you think 2 foil shaped fins would create drag problems. Stern-drive manufacturers are not using belts or chains so they have no reason to look into an idea like this. Robbie sterndrives made here in melbourne before volvo and merc and 1 of their models had a chain drive if I remember correctly. .

 

Mudcrab, it was just a "thought bubble", I'm not trying to peddle the idea, or sell you shares in it ! Even if it did make a belt drive work better, there are other problems like routing of exhaust gases, provision of water pump etc that might render it a no-go. I really haven't thought about it too much. But as to the drag aspect, which of course is very important, it certainly would increase frictional drag, but the form resistance might well be less with the slimmer cross-sections. There may be issues with interference with the propellor. Don't know.

 

I was ready to buy shares too. Seriously I think it is a good thought. I am thinking of something made at home with a small diesel. I have a 14 hp yamaha diesel doing nothing.

 

Hi Guys,
firstly 2 foil lower end drag. The big limitation with outboard speed is appendage drag. the faster you go the more power you consume to push on a cubic(power 3) basis. Twice the speed, 8x the drag.

Mr. E picks up most of the issues - to be honest I haven't pursued the idea in any depth either althougI am sure there is a an old patent with it proposed.

So surface area is one overhead.
Then the gap effect - raises flow challenges that will also contribute to drag, possible stall, cavitation, additional turbulence over prop etc etc.
The motto is less is more.

Re the big boys and belts.
Well if one looks at the patent record, they have all explored these ideas for years and I am sure will look again.
Now I know it's kind of whacky trolling through old patents for no reason - but I have done it(for a reason) and the range of alt ideas is quite astounding. Many more than I would have come up with. But in the end none of the 'others' has survived. Is OXE the game changer?

Mr E. apologies - No intention on my part to sound grumpy or short - more a function of my typing style.
Cheers

 

WP23, you are certainly not going to be bothered by leg drag considerations with that engine and modest speeds.

 

Mudcrab, what was the reason to be looking at old patents ? To see if an idea you have wasn't already patented ?

 

Yep.

Hmmmmmm ...

Kahn!!!

 

I have thought at times that a raked lower drive leg would cut drag, similar to how jet aircraft adopted swept wings to reduce drag. The problem of course is how to achieve that mechanically, if indeed there is a pay-off in reduced drag.

 

As an afterthought, the twin fins meeting the "bullet" might be a world champion at snagging kelp or plastic bags !

 

I have done that trolling also Mudcrab, both for prior art and ideas. Prior to my becoming computer literate I spent some considerable times at the US Patent Office in DC looking up subjects related to marine propulsion. A couple of the illustrations I posted over HERE were found there, and eventually scanned by me for this posting:
http://www.boatdesign.net/forums/propulsion/exciting-new-eps-thruster-propulsion-9432.html#post65512.

I do recall a number of chain drive patents, mostly utilizing old style roller chains, and a number of them with 'dual legs'. I just no longer know where I can find those illustrations

 

http://www.yachtforums.com/threads/new-drive-system-from-volvo-penta.2232/

...and on that discussion I posted
Pulling Prop Belt Drive
http://www.yachtforums.com/threads/new-drive-system-from-volvo-penta.2232/#post-7567

Just found another page of postings from Yachtforums
http://www.yachtforums.com/threads/diesel-electric-propulsion.2229/page-9
...and an close-up image of the silent chain engagement with the sprocket

 

Mr E. I trolled patents for ideas and to see if an idea was covered. Dammed hard doing something novel. So what it gave me was a background for possible direction and the realization that it is increasingly hard for the little guy to do anything new. Actually it;s equally hard for the big guys too but they've got a lot more resources.

But maybe people need to start think about the fact not all the options have been explore yet.

IMO there are plenty of DIY options that will work well.

e.g. Think about how you might make you own stern drive with that engine...

Just occurs to me you could do a crowd design right here. Set your specs and ask for suggestions.

Cheers

 

Something like this:
http://www.boatdesign.net/forums/jet-drives/jet-jet-pump-waterjet-jet-drive-vs-prop-11254.html

 

That was WP23's diesel, not sure exactly what application he had in mind for it.

 

Who ever has the diesel donates it's virtual capacity to the forum then has the massed intellect solve all the issues!
The way forums drift is like in a rapid, so setting well defined outcomes would be essential. You need to know exactly what you want for you ask for help other wise you will not get anywhere.

Example, this thread is about the OXE diesel outboard and now we want design 14hp thingy for a boatie something or other.

Cheers