jetski engine in a sailboat?
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jetski engine in a sailboat
I see that braking is now available on some jet skis. I would imagine it could give you reverse. The beauty of the concept is an inboard motor that allows steering like an outboard. The downside would probably be more drag. Another negative would be it is fueled with gasoline which is not as safe as diesel and it would be fairly loud.
http://www.youtube.com/watch?v=7JHBsV_vUR0&feature=related
I see that braking is now available on some jet skis. I would imagine it could give you reverse. The beauty of the concept is an inboard motor that allows steering like an outboard. The downside would probably be more drag. Another negative would be it is fueled with gasoline which is not as safe as diesel and it would be fairly loud.
http://www.youtube.com/watch?v=7JHBsV_vUR0&feature=related
jetski engine in a sailboat
I don't think power would be a problem. These jetski motors put out plenty of horsepower. Depending on the model they can range from low 100 to close to 300 hp. I don't know how that translates to a traditional prop but I'm sure it's sufficient to push Txtowman's Catalina 22 to hull speed. A Kawasaki single passenger jetski puts out almost 700 pounds of thrust.
I don't think power would be a problem. These jetski motors put out plenty of horsepower. Depending on the model they can range from low 100 to close to 300 hp. I don't know how that translates to a traditional prop but I'm sure it's sufficient to push Txtowman's Catalina 22 to hull speed. A Kawasaki single passenger jetski puts out almost 700 pounds of thrust.
A jetski engine is nothing but a two or four-cycle gas engine. . . .usually. Because it could just as easily be a diesel( http://youtube.com/watch?v=aSMcaYmCPrI&feature=related ). What is key is what hangs on the end of the shaft. In this case a jet pump. So you would need a big inlet in the bottom of the C22 for water in. The pump would be straight out the stern. I think that you could do without a steering pump outlet and use the rudder. This would significantly reduce the complexity. I think there might be room under the C22 cockpit for such an arrangement.
P.S. interesting concept so went looking. Found this discouragement: http://www.oceannavigator.com/content/jet-drive-not-best-auxiliary-sailboats
P.S. interesting concept so went looking. Found this discouragement: http://www.oceannavigator.com/content/jet-drive-not-best-auxiliary-sailboats
jetski engine
All U Get
How about a two-speed rear end?
I thought about this idea for a while, something like "Red October", but the diplacement hull killed the idea for me. Ed's link sounds on the money as far as engineering goes.
All U Get
How about a two-speed rear end?
When your jetski powered sailboat starts buzzing around in the anchorage it would be the "night of doom".
Ray
Ray
I'm sure it's possible.... I just can't think of any advantage over traditional power set ups. You're essentially talking about pump vs. prop..... not gas vs. diesel.. Which is more reliable, effecient, cost effective.. and so on?
I just can't see WHY?
I just can't see WHY?
Another problem with jets is fouling and corrosion. It doesn't take much to mess up the pump performance. That's why jet powered boats like the Hinckley Picnic boat are often stored on lifts in southern waters.
The next major step in sailboat auxiliary power is hybrid systems. Electric drive (conventional shaft, or in a saildrive/outdrive/outboard mounting), sufficient batteries for maybe 30 to 60 min of electric running, plus an efficient gas or diesel generator capable of driving the electric motor to hull speed directly.
Actually, all auxiliary sailboats are hybrid. Wind power came first - then the carbon fueled engine (steam).
A modern diesel engine connected to a standard shaft running at 50%-70% RPM is about 20% more fuel efficient than running a genset to run an electric motor to run that shaft and more than 50% more efficient than running a genset to charge batteries to later run an electric motor to run that shaft. Everytime you convert energy you lose.
30hp equals 22 killowatts. Ignoring conversion losses in both types of systems (and if I'm doing the math right), this would mean you'd completely empty 4 fully charged type 31 100amp hour 12v batteries in 15 minutes of running.
Carl
A modern diesel engine connected to a standard shaft running at 50%-70% RPM is about 20% more fuel efficient than running a genset to run an electric motor to run that shaft and more than 50% more efficient than running a genset to charge batteries to later run an electric motor to run that shaft. Everytime you convert energy you lose.
30hp equals 22 killowatts. Ignoring conversion losses in both types of systems (and if I'm doing the math right), this would mean you'd completely empty 4 fully charged type 31 100amp hour 12v batteries in 15 minutes of running.
Carl
hybrid power, the next step
I'd have to disagree Kenn.
"the next step" is ALWAYS driven by cost.
If an engine=generator=battery=motor=transmission=prop was cheaper than an engine=transmission=prop then folks would get on board right now. The price of fuel favors the latter due to the reasons carlf mentioned. The cost to build favors the former only when you can get buy with a much smaller motor used to supply your base line power needs and use the batts for those high power intermittent loads. you don't use a sailboat like that. The base load is the full power load. It is not crusing at 10% power on the interstate and some acceleraton to get to speed and handle hills. The hills sort of factor out as you can get some regeneration as you coast down them.
I see lots of folks look at auto hybrids and think they could do that to a sailboat when the usage just does not support it. And probably never will. Your electric motor has to be sized to handle the max load of hull speed and you opperate near that most of the time. There is no "getting up to speed" (high load acceleration) followed by a loafing along at hull speed (interstate driving) type of use. The load just goes up with speed. So you either have to lower the speed you want to use the boat at or don't embrace hybrid tech in boats.
With all that said, I think most boats are a) overpowered motor wise and b) not very good sailboats. If you only want to sail and just need the motor to get back to harbor then this may be a cheeper alternative as you can just forgo the gas motor all together and use the batts and a shorepower charger. That is really dependant on how you use your boat and limits what you can do with it. Now if your boat sails pretty well you can drasticly reduce the need for a motor in the first place......... and all you need is a little putt-putt motor.
So I see the next step being either nothing or a move to smaller motor hybrids in much imporved sailing capabilities boats.
I would note that we have a pretty long history of sailing into and out of harbors with out motors.
I'd have to disagree Kenn.
"the next step" is ALWAYS driven by cost.
If an engine=generator=battery=motor=transmission=prop was cheaper than an engine=transmission=prop then folks would get on board right now. The price of fuel favors the latter due to the reasons carlf mentioned. The cost to build favors the former only when you can get buy with a much smaller motor used to supply your base line power needs and use the batts for those high power intermittent loads. you don't use a sailboat like that. The base load is the full power load. It is not crusing at 10% power on the interstate and some acceleraton to get to speed and handle hills. The hills sort of factor out as you can get some regeneration as you coast down them.
I see lots of folks look at auto hybrids and think they could do that to a sailboat when the usage just does not support it. And probably never will. Your electric motor has to be sized to handle the max load of hull speed and you opperate near that most of the time. There is no "getting up to speed" (high load acceleration) followed by a loafing along at hull speed (interstate driving) type of use. The load just goes up with speed. So you either have to lower the speed you want to use the boat at or don't embrace hybrid tech in boats.
With all that said, I think most boats are a) overpowered motor wise and b) not very good sailboats. If you only want to sail and just need the motor to get back to harbor then this may be a cheeper alternative as you can just forgo the gas motor all together and use the batts and a shorepower charger. That is really dependant on how you use your boat and limits what you can do with it. Now if your boat sails pretty well you can drasticly reduce the need for a motor in the first place......... and all you need is a little putt-putt motor.
So I see the next step being either nothing or a move to smaller motor hybrids in much imporved sailing capabilities boats.
I would note that we have a pretty long history of sailing into and out of harbors with out motors.
(Forgive my hybrid derails, but hey it's more practical than a jetski engine 
)
1) a modern generator's combustion engine is optimised for the small range of RPM needed for efficient generation, whereas a marine propulsion engine has to work at a wider range of RPMs
2) batteries can be topped up by solar panels, wind generators or shorepower, meaning the generator is run just to recharge batteries or to directly power a sustained motoring run.
I believe it's already possible to spec a diesel generator/electric motor combo that approaches the efficiency of a diesel alone, due to the increased efficiency as a generator. I can't find the link, sorry.
I'm very impressed by today's marine diesels, but one of the main reasons we love them is that the designs are old, simple and dependable. And think on how the average cruiser is using them - putting in and out of their slip or mooring, topping up the batteries during an extended cruise. They're not always running at 80%, which is where they're most efficient (and happy)
)Do you have a source for those efficiency numbers? I'm still working through various possibilities, but I do know that your analysis isn't taking into account:
1) a modern generator's combustion engine is optimised for the small range of RPM needed for efficient generation, whereas a marine propulsion engine has to work at a wider range of RPMs
2) batteries can be topped up by solar panels, wind generators or shorepower, meaning the generator is run just to recharge batteries or to directly power a sustained motoring run.
I believe it's already possible to spec a diesel generator/electric motor combo that approaches the efficiency of a diesel alone, due to the increased efficiency as a generator. I can't find the link, sorry.
I'm very impressed by today's marine diesels, but one of the main reasons we love them is that the designs are old, simple and dependable. And think on how the average cruiser is using them - putting in and out of their slip or mooring, topping up the batteries during an extended cruise. They're not always running at 80%, which is where they're most efficient (and happy)
(Sustaining my derail, sorry.)
(Cost... heh. We're yachters. What is this "cost" thing?) From a cost perspective, it becomes alot more interesting to consider the boat's total energy needs - propulsion plus all onboard power. Let's compare complete systems:
Conventional:
- propulsion diesel + transmission + alternators
- separate generator (sized for electrical loads + recharging)
- batteries
Hybrid:
- one (or two) generators - sized for propulsion (directly powering boat at hull speed)
- electric drive motor
- batteries, sized for 30 to 60 min of electric powering at hull speed
You can already see that for a larger boat which would definitely have a separate genny anyway, having two identical generators would be a great safety factor.
It's also clear to me that a higher initial cost would be offset by lower operating costs, when shorepower, wind, solar can keep the batteries topped up for the short runs to/from the dock. Electric motors are simpler and more reliable than diesel + transmission, and they vibrate much less, all of which could translate to lower wear on stuffing-box, shaft, cutless.
I don't currently have the links to back this, but I believe that a generator diesel spends most of its life under optimum rpm and load, which means greater efficiency and potential for reduced wear. Generators can be located just about anywhere on the boat which could simplify maintenance. Assuming that industry standards emerge for size, mounting and output, it would become a breeze to swap out generators, even from a different maker. Compare this to the current hassle of repowering.
Battery technology cost and weight make the all-electric aux mostly impractical, and anyone other than the daysailor doing short in/out powering will too often find themselves in a jam when the charge runs out.
[update] Here's Nigel Calder's blog with some details of a hybrid project he's undertaking tfor the EU. He goes into detal about some of the generator efficiency factors I've mentioned.
[update #2] More links on electric propulsion in general.
Again, apologies for fouling the jetski engine thread.
I touched on efficiency above (and I do need to find those links again that support this). I also note that some of the larger cruise ships are driven by generators + electric motors, which suggests that efficiency has been proven at that level, anyway.
(Cost... heh. We're yachters. What is this "cost" thing?) From a cost perspective, it becomes alot more interesting to consider the boat's total energy needs - propulsion plus all onboard power. Let's compare complete systems:
Conventional:
- propulsion diesel + transmission + alternators
- separate generator (sized for electrical loads + recharging)
- batteries
Hybrid:
- one (or two) generators - sized for propulsion (directly powering boat at hull speed)
- electric drive motor
- batteries, sized for 30 to 60 min of electric powering at hull speed
You can already see that for a larger boat which would definitely have a separate genny anyway, having two identical generators would be a great safety factor.
It's also clear to me that a higher initial cost would be offset by lower operating costs, when shorepower, wind, solar can keep the batteries topped up for the short runs to/from the dock. Electric motors are simpler and more reliable than diesel + transmission, and they vibrate much less, all of which could translate to lower wear on stuffing-box, shaft, cutless.
I don't currently have the links to back this, but I believe that a generator diesel spends most of its life under optimum rpm and load, which means greater efficiency and potential for reduced wear. Generators can be located just about anywhere on the boat which could simplify maintenance. Assuming that industry standards emerge for size, mounting and output, it would become a breeze to swap out generators, even from a different maker. Compare this to the current hassle of repowering.
Sure. But those factors suggest that alot of owners are already prepared to pay more for perceived improvements in safety and dependability. A well-chosen hybrid system is going to be more efficient to run than an oversized diesel plus a genny. It's easier to distribute and mount the weight components of a hybrid system, which should facilitate better-balanced boats with improved sailing characteristics.
... So we're not that far apart
Battery technology cost and weight make the all-electric aux mostly impractical, and anyone other than the daysailor doing short in/out powering will too often find themselves in a jam when the charge runs out.
[update] Here's Nigel Calder's blog with some details of a hybrid project he's undertaking tfor the EU. He goes into detal about some of the generator efficiency factors I've mentioned.
[update #2] More links on electric propulsion in general.
Again, apologies for fouling the jetski engine thread.
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