High Trust

[JamesG161]

To be honest about prop thrust...
It is only the efficiency conversion of engine Horsepower to water pumping.

Since most sailboat designs are limited by their hulls speed, the only time Trust is import to me is when I need..
REVERSE
to back off a stuck keel.

A three blade propeller will significantly slow your under sail forward speed.
Jim...

 

[Will Gilmore]

It is only the efficiency conversion of engine Horsepower to water pumping.

That is true but also misleading. Engine HP is a rating measured at the crank shaft (how strong is the engine), thrust is measured at the propeller output (how much push does it produce). They can be equated in a general way but they don't exactly measure the same thing.
- Will (Dragonfly)

 

[JamesG161]

HP used is directly related to the RPM of the engine. As you noted the gearing changes the engine RPM to propeller RPM.

Propeller design, pumps water as it rotates thus converting Diesel fuel into thrust. I would not think rated HP has anything to do with efficiency which is defined as

Efficiency = Work OUT / Work IN

If you run your engine at half rated RPM, that would be the Work IN. Typically, half RPM is half Rated HP.

The resultant Work OUT is determined essentially by the Propeller propulsion, limited by the drag of the hull, etc.

Propeller design, cuts the water, pitch to pump, thin edges to discharge water without cavitation.

A two bladed prop is preferred to reduce drag when there is no engine running.
Jim...

 

[SwitchintoglideIII]

Thank you SwitchintoglideIII, Yes, just what I needed, first hand info and it does really help. Have you any info on the dia and pitch please.
The only one I can find in the UK is this 3 blade High Thrust prop View attachment 144708
9 3/4 x 8

Solas Amita 4 Aluminum Blade High Thrust....10" x 7 pitch if I remember correctly. Designed specifically for Heavy Loads & Kicker Motors

 

[FastOlson]

I thought the the subject was outboard motors, and when you tilt it up when sailing there is no drag.
At least there never was for me.

 

[GBGraham]

Thanks for all your inputs. Looking on the UK Amazon site there is an American site advertising props. Anyone out there that may know these people please, Polastorm and the quality of their props.

 

[justsomeguy]

Chinese manufacturer, FWIW.
https://company.metstrade.com/?a=FEY9pLHXWFV1XHUy5r0nDqz3QHFVJSg1bUxOnsJffJk=

 

[GBGraham]

Thanks, Thought it had to be because of price, although not that all Chinese is sh one t ! but I wouldn't want to be the guinea pig . . . .anyone out there used them?

 

[justsomeguy]

but I wouldn't want to be the guinea pig . . .

Somebody has to!

 

[Crazy Dave Condon]

YOu were smart opting out of the 15 as it would have been too much causing the bow to raise and you would have had to throttle it back down. I note the Hunter Legend 260 which meant the boat was built at the Hunter plant in England. There was another Hunter company in England, so Hunter Marine in the U.S. had to rename their company in England as Hunter Legend.

Most know who I am but I know this boat oh to well. Feel free anytime to contact me. Now if we could get rid of the corn crap in gasoline.

 

[GBGraham]

Mmmm Only certain things I like to be first at and spending money is very far from the top of that list
I suppose when only buying for testing purposes 55 USD is a lot better than 135 USD for the UK Yamaha 3 blader. But it's a Catch 22, if the size does work well for you, then you'll wish you'd bought the better one.
I can't find a four blade prop here in the UK other than by special order or off your home sites and by the time the post has been paid for it makes it expensive especially if I get hit with a customs import tax too.

 

[Crazy Dave Condon]

Based on experience a three blade was fine for me without getting so darn technical which most folks here are not technical savy. I just go by experience but the two blade has worked for years and a lot hinges on each area where to use any engine and simply go out and practice with it which will help a lot in the beginning. In the U. S. I sold nearly 20 to 25% of the entire 260 line. I go back to experience teaching me.

 

[justsomeguy]

...customs import tax...

One-world gov't should clear up that stupidity.

Oops.

 

[GBGraham]

Crazy Dave Condon, Thank you for that snippet, The yacht broker told me the owner had imported it. I knew it was supplied by Opal Marine but now I look further into the paperwork there is a Builders Certificate stating it was built in Alachua. When I viewed to boat I thought for an imported boat it was strange that it was on a UK trailer, so this may be a clue.
Thanks for the offer of help to any further info, I am sure I will be
I'm sure that corn fuel job here in the UK was a con to extract money and grants out of the greens, tree huggers and our government because I am sure all now have gone bust.

 

[GBGraham]

One-world gov't should clear up that stupidity.

Oops.

Brave statement And who would you like to be the President of your fantasy World. Trump, Putin, Kim Jong-un?

 

[justsomeguy]

Brave statement And who would you like to be the President of your fantasy World. Trump, Putin, Kim Jong-un?

Doesn't matter.

 

[Crazy Dave Condon]

Folks, politics has no business here and as for Kim Jung-un, many from all walks of life are concerned he will start something that the world will never recover from.

 

[justsomeguy]

Perhaps I'll get a time-out, but not from you, @Crazy Dave Condon .
I'm just proposing a way to obviate importation tarrifs.

 

[Will Gilmore]

If import taxes aren't levied, it will come out of our income tax.
Just saying

- Will (Dragonfly)

 

[Crazy Dave Condon]

Justsomeguy; No intent for harm but merely letting folks know this site is for helping fellow sailors, not politics as it can be explosive. You know being a college graduate looking for a job, I had to don on Shoney's Big Boy costume during manager training and several friends stopped by looking for me which I was pointed out. Needless to say in that fantasy world of wearing that costume, I had some different nicknames to include Big Boy. I left that short job duration for something more becoming, Crazy Dave.

I will say though before the U.S. was forced into WWII, many tend to forget that we were an isolationist country coming out of the Great Depression taking care of ourselves with war waging in the Pacific rim and in Europe without much of a military force except for the naval contingent at Pearl. Most military strategians would say we could not win a two front war but we did. I had the honor of knowing Pres. Reagan personally. We may or may not be on the right path but only time will tell but looking at the Reagan policies, I think we are.