I find it hard to believe that it would be able to create enough power due to it's size. Nice idea, but does it work in practice?

Though it is not the fastest method, outboards arn't made for speed, but rather thrust and this one has a lot of torque. If you include the fact of how much lighter it is, so there is less weight, and the fact it is so easy to use, no pulling cords, etc., I think you would probably make a simular jouney in the same time.

Hi Pirate

The Yanks have used things like these for years as silent motors for lake fishing, great if you want to sneak up on trout. Personally, I can't think of any other worthwhile use for them. 400 watts is only about 1/2 horsepower!!! and it would draw best part of 40 amps at 12v, maybe more, depending on efficiency. An 80 amp hour battery would last about an hour so make your own mind up.

Definatley not the first of it's kind.

One of the things that I found really impressive about this if that it has taken 5 months from drawing board to shop. That's the German's for you!

Hi, I am one of the founders of torqeedo and would like to thank you for your interest. Just a few comments on the topics discussed:

We look forward to having our engines tested by independant authorities. We apologise if this may take a while since we will only start delivery by end of february.

Regarding the power comparison vs. combustion engines, we always refer to effective output power as performance indicator. The power indication of a combustion engine generally refers to the power at the motor shaft. However, a combustion engine of this power class loses some 70-80 percent of its energy alone in the propeller. Our energy loss along the entire drive line including propeller is significantly lower, so our 400 watts engine compares to a 1 HP and our 800 watts engine compares to a 2 HP combustion engine in terms of effective output power.

New to the product is not that its electric. New is that you do not necessarily need external batteries, the high efficiency, the lithium-manganese technology, the folding mechanism, the weight. Certainly, our engines are not suitable for gliding and only for the boat sizes specified.

Please apologise the lengthy answer and please do keep in touch in case of further questions or comments. Our english catalogue will be available by the end of the month.

Cheers
Christoph

Thanks Christoph. Your answer is very helpful and it is good to have the manufacturer helping to enlighten the public on the product. Hope things go well for you at the Düsseldorf boat show this week.

I think I will be sticking to my diesel to be honest. There is a reason why electrics and water shouldn’t be mixed!

The confections on this are really safe. Not a lot of chance of getting electrocuted on this baby! In fact I think it would probably fair to say that this has been manufactured to such a good level, you are more likely to be hit by lighting!

"----Regarding the power comparison vs. combustion engines, we always refer to effective output power as performance indicator. The power indication of a combustion engine generally refers to the power at the motor shaft. However, a combustion engine of this power class loses some 70-80 percent of its energy alone in the propeller. Our energy loss along the entire drive line including propeller is significantly lower, so our 400 watts engine compares to a 1 HP and our 800 watts engine compares to a 2 HP combustion engine in terms of effective output power.----"

Please explain in fundamental terms, the physics behind this as it must have changed since I was at school! Does your drive system not also use a propeller?

Hi Chas, glad to follow your request. I'll use an example.

If you look at a typical 2.3 HP 4-stroke engine, i.e. an engine with 2.3 HP or 1,690 watts at the motor shaft: This motor will generate an effective output power (force times speed) of some 380 watts. This means the propeller has an efficiency of 22%, or put it differently: 78% of the available power is lost in the inefficiency of the propeller.

In comparison, our Torqeedo Travel 800 works on 800 watts that it extracts from the battery - much less than the 1,690 watts that the 2.3 HP engine has available at the motor shaft. This big difference nevertheless is compensated because the Torqeedo engine has an overall efficiency (including all losses, also the losses in the propeller) of some 46%. This is a clear benchmark and results in an effective output power of some 350 watts. Given this output power, the engine is absolutely comparable to a 2 HP combustion engine.

Of course our engines have propellers too. Only: due to the torque characteristics of our motors, we can use extremely high-efficiency propellers. Also we are applying latest knowledge from the field of propeller physics. So, I will not tell you exactly how much higher the efficiency of our propeller is compared to the mentioned 2.3 HP engine propeller. But expect it to be not just a few percentage points higher.

Hope I could answer your question. I believe, when you saw the propellers, it would be even clearer. Nevertheless, if you have other questions, please do not hesitate to contact me.

As mentioned in my earlier comment, we look forward to have our statements tested. We feel quite sure about them because we have done some extensive testing of our and competitor's engines since we started our company.

Hi Roxy: Thank you for your goodwill! :-)
Best wishes to you.

"--- Of course our engines have propellers too. Only: due to the torque characteristics of our motors, we can use extremely high-efficiency propellers.---" DO MANUFACTURERS OF CONVENTIONAL DRIVES NOT OPTIMISE THE AVAILABLE ENGINE TORQUE BY THE USE OF A REDUCTION GEAR BOX!!!

"---Also we are applying latest knowledge from the field of propeller physics.---" WITH THE GREATEST OF RESPECT, THE EFFICIENCY OF PROPELLERS HAS NOT BEEN INCREASED SIGNIFICANTLY SINCE SOME OF BRUNELL'S DESIGNS.

"---So, I will not tell you exactly how much higher the efficiency of our propeller is compared to the mentioned 2.3 HP engine propeller.---" I THOUGHT AS MUCH!!!

You have raised some intresting points Chas. It is good to have someone with your knowledge on the forum.

DO MANUFACTURERS OF CONVENTIONAL DRIVES NOT OPTIMISE THE AVAILABLE ENGINE TORQUE BY THE USE OF A REDUCTION GEAR BOX!!!
The gear reduction for combustion engines ranges typically between 1:1.8 and 1:2.5 - not more. The engine typically turns at 5,000-6,000 rpm. In consequence, typically a 7.25" diameter and 4.75" pitch propeller is turned at 2,000-3,400 rpm.
All this information can be verified easily on manufacturer's websites and catalogues.

In comparison, our Travel 800 model turns a
prop with 12" diameter and 10" pitch at 630 rpm. Do we agree that bigger propellers with higher pitch and a slower turn rate are generally more efficient? If yes, you can tell there is potentially a huge difference in efficiency (and in fact there is).

I have a couple of hypotheses, why propellers of combustion engines of this power class have no better efficiency, but we don't build them ourselves so I don't know (could be because the angular gear they require puts some restrictions, could be because the torque at low revs will always be small, even if you gear it down extremely).


WITH THE GREATEST OF RESPECT, THE EFFICIENCY OF PROPELLERS HAS NOT BEEN INCREASED SIGNIFICANTLY SINCE SOME OF BRUNELL'S DESIGNS. Most of the advantage of our propellers comes from utilising the more favorable torque characteristics of our engines (high torque at low revs) as described above. Some impact comes from utilising advanced calculation methods and modern designs. The total difference is by all means significant.


I am not quite sure if I can convince you in writing anyways. Will you be convinced, when independant test results show the differences in efficiency?

Cheers
Christoph

"---The gear reduction for combustion engines ranges typically between 1:1.8 and 1:2.5 - not more. The engine typically turns at 5,000-6,000 rpm. In consequence, typically a 7.25" diameter and 4.75" pitch propeller is turned at 2,000-3,400 rpm.
All this information can be verified easily on manufacturer's websites and catalogues.

In comparison, our Travel 800 model turns a
prop with 12" diameter and 10" pitch at 630 rpm.---" PLEASE COMPARE LIKE FOR LIKE.

"---Some impact comes from utilising advanced calculation methods and modern designs.---" WOULD YOU CARE TO SHOW ME YOUR CALCULATIONS???

Wow! Hey guys, I never knew all this was so involved. I was just looking for something small and quiet that worked - so we could play my daughter's favourite game and snuck up on a duck with a big bag of bread crumbs. All I know about turn rate is it's either my turn or hers - but you blokes are mighty impressive with the stuff you think about. Thank goodness you are - if it was me designed a motor, I'd be still out there, hollering for the RNLI to come get me. More power to all of you!

Hi Chas,

Regarding comparing like for like: To my mind it is like for like, because both propellers create about the same effective output power. Only our engine needs a lot less energy to produce it.

Regarding calculations: We are working with potential grid methods based on singular solutions of Navier Stokes' equation. This method has been used on propellers for big ships and submarines for quite some time. To our understanding it is not used for small outboards so far.

Cheers
Christoph

PS: I will be at Duesseldorf fair for the next days and will only frequently check my mail/the web. If you should be there too, please look us up.

"---Regarding comparing like for like: To my mind it is like for like, because both propellers create about the same effective output power. Only our engine needs a lot less energy to produce it.---" YOU'VE YET TO PROVE THIS AND I BELIEVE I WILL BE WAITING QUITE SOME TIME!!!

YOU PREVIOUSLY MADE THE STATEMENT "Also we are applying latest knowledge from the field of propeller physics." TO WHICH I REPLIED "WITH THE GREATEST OF RESPECT, THE EFFICIENCY OF PROPELLERS HAS NOT BEEN INCREASED SIGNIFICANTLY SINCE SOME OF BRUNELL'S DESIGNS." YOUR ANSWER TO THIS WAS THEN "---Most of the advantage of our propellers comes from utilising the more favorable torque characteristics of our engines (high torque at low revs) as described above.---" SO WHAT HAPPENED TO THE LATEST KNOWLEDGE FROM THE FIELD OF PROPELLER PHYSICS THEN?? THERE'S NOTHING NEW HERE, SHIP BUILDERS (ENGLISH AND GERMAN) HAVE BEEN USING THESE PRINCIPLES SINCE THE ADVENT OF STEAM SHIPS.

IN YOUR LATEST POST YOU CLAIMED "---Regarding calculations: We are working with potential grid methods based on singular solutions of Navier Stokes' equation. This method has been used on propellers for big ships and submarines for quite some time. To our understanding it is not used for small outboards so far.---" THE NAVIER-STOKES EQUATIONS ARE THE FUNDAMENTAL PARTIAL DIFFERENTIAL EQUATIONS THAT DESCRIBE THE FLOW OF INCOMPRESSIBLE FLUIDS. SO WHAT, WEVE ALREADY AGREED THAT PROPELLOR EFFICIENCY HAS NOT BEEN INCREASED SIGNIFICANTLY SINCE BRUNELL'S DAYS. I'D STILL BE INTERESTED IN SEEING YOUR CALCS THOUGH!!!

THE ONE FUNDAMENTAL LIMITATION FOR ELECTRIC DRIVES IS THE STORAGE OF POWER, IE BATTERIES! i DON'T KNOW THE WEIGHT AND OUTPUT OF YOUR BATTERIES BUT PETROL HAS A CALORIFIC VALUE OF AROUND 44 MJ/KG

Where did I go wrong? I had an electric outboard once but found it very restricting...I couldn't get a long enough extension lead.

Thank you Chas you have really helped to spread some light on the situation, rather than listening to all this rehearsed PR spiel.

You have to find a pretty long lead harry thats got a good waterproof seal that would suit an out board