Efficiencies for Surface drives.

efficiencies

Do outboards really have all the speed records, I must not be keeping up with
that info, I will need to do a bit of reviewing.

 

In 1976 Mercruiser sold their one millionth sterndrive.
Sure shaft is simplest and cheapest in the long run but cant do what a sterndrive can do.
Each system has pro's and cons
Sterndrive is the best all rounder hence it outsells all others combined.
Pods are showing signs of sterndrive type longevity ( good when they are new)and expense.
The Volvo with the forward facing are hopeless in Asia due to all the junk in the water, almost a prop repair everytime you go out.

I think they should be removable with the boat in the water to have a unique selling point.

 

All upto when you need more horsepower
2 way average kilo records:
Single outboard at 176mph
Unlimited prop 205mph
( of course drag boats have higher top speeds with 2 shaft drives)
It would surprise me if a surface drive has ever held a kilo record?
The 4 engined cat phenomenon was having a go but project halted.

 

efficiencies for surface drive

Full size Helicopters shake a lot with multi blade rotors.
A full size version of the single blade helicopter should be smoother than a model as the big heavy Helicopter is less susceptible to the air disturbance and currents.
The design of the single blade surface prop would be interesting. I think the way a conventional screw propeller works and creates swirling eddies is a waste of useful power and reduces efficiency for the purpose it is intended for surface propulsion.
Just moving as much water from the rear of the boat, at the velocity and volume required with least amount of drag to do the intended work using least possible energy is what is required.
Screwing through the water with little resistance is not doing much work, you have to have reaction.

 

Have you seen this boat? https://youtu.be/ZDatcZulmP8

https://youtu.be/Ov_2fR1ISTM

You really need to broaden your horizons a bit as I don't know of any large speed records held by an I/O, be that Mercury, OMC, Volvo, Suzuki, Yamaha or ?

Popularity is not a sign of superiority, rather its a sign of what's cheap and easy. A boat manufacturer has an easier time selling the customer one package rather than multiple players in the same package, (engine outdrive package) so this is what moves the #'s to the point whereby economy of scale can be realized, which in turn drives the #'s. Not to mention it generates one hell of a parts supply business.

 

All true Rik
But i do remember when Mercury had the tie up with Arneson and did several installs on what would normally be I/O boats in Australia.
Sure they went faster a major pro but i guess the cons didnt warrant it?
Do you have any details about that deal 30 years ago?

No question a Magnum 53 is a great package with Arnesons.
And as Howard showed us years ago its a marriage made in heaven when you use a turbine for power.
There are plenty of boats out there that could break world records, never understood why they dont have ago?
Spirit of Qatar up for tender right now.

 

The term Surface Propulsion I think is misused in that surface propulsion means just that.
A propeller driving a shallow draft boat piercing the surface of the surrounding water level as in a tunnel and hydroplane at speed and not a deep v hull making a deep grove down to denser water.

 

Yes. It's called partial or full supercavitation. 'Base ventilation' means merely that the blade's tip vortex ends on the air-water interface and is filled with air. There is no air cavity on the low pressure side of the blade. Supercavitating blades run with only a fraction of the thrust of a base ventilated blade.

 

Incorrect. Fastest prop driven boats have surface drives.

 

The outboard world speed record is about 177mph with an Evinrude V8 on a Karelsen cabover hydro in 1989. The problem was to keep the boat on the water. Therefore a tunnel boat could not be used, and so far as I know that was the last record attempt. The rig now sits in a museum in or near Seattle, having been towed from a bar in Fla. to a friend's body shop in Houston before going to Washington.

 

Cool!

 

Hi,
to get the right position , it takes a lot of time to adjust the propeller position , the high , the angle of the propshaft, the design of the strut ( rectangular or round and the dia) . Have a look at the record setting modelboat. The angle of the propshaft and the high are adjustable and to ab thin shims will show big results how the whole boat is doing.
. First run loos of propellerblade , broken blade because of very thin blade and razor sharpe . Propeller turn up over 100000 rpm and there is space to rise as the propellertipspeed is lower than that of dragboat propellers. Dragboatpropellrs do over speed of sound tipspeed. Such propeller worke only with the pressure surface and belong to the reduced drag of the drive , no strut and no driveshaft in the water the efficancy is higher than full submergerd drives. At lower speed full submerged drives have higher efficancy belong to the propellerdisce load. Single blad have highest efficancy as they have only one tip loos wirl and high wingspan to blade deep like a slope plane.
All airplane aerodynamic is like the hydrodynamic when submerged . Only cavitation is not in the air.
Forgot: the modelboat use a wire drive with a slitly bend pianowire that only allow to small adjustment. The JAG s Team try to set the all over propeller driven Boat record .
But yes this is not to compare with topspeed of a full scale boat.

Happy Amps Christian

 

Fastest speed in a prop boat is 338.17 mph, roughly 550 kmph. Brittany Force , Las Vegas, 2019.

 

@sandhammaren05 , @powerabout, would that record breaking outboard have the prop raised to the point that it was a surface drive, or would it have been fully submerged?