Curious

[floater1]

I know this is a simple question, but the answer is a little more complicated.

On any vessel, why is the propulsion always in the rear. ( a pusher)

On a smaller scale, I have a canoe with a front mounted motor (trolling, 56 pound thust)), and this little booger can spin on a dime and give change, and tracks much straighter than a rear mounted system. It got me thinking, as in the automotive field, a front drive might be somewhat more efficient to pull the vehicle vs. push, can this apply to the boat/ship design industry as well?

I remember Yipster had a craft design with the outboard mounted fore of the passenger compartment.

ANY input would be appreciated.

Mike

[Tim B]

Forward-mounted propellers are around, particularly on ferrys using a Voith-Schneider setup. They do have incredible manoevrebiliy. The problem usually comes in putting a propeller (and kit) at the bow and not having the bow slamming horibbly or getting stuck in every wave. There is also the point of protection, as propellors at the stern rarely take the brunt of any damage from ship-ship collisions.

There are increases to be had in propeller efficiency in "open water" as opposed to behind a hull, but until anyone can think of a way to stop the slamming/burying problem, and get rid of exhaust gasses / coolant or whatever, and keep the boat nicely balanced and manoevreble (because hydrodynamically, we're pushing volume ever further aft)

Interesting idea though, and it would have application in certain ships.

Tim B.

[BulBob]

Motors mounted on the front are for control but the thrust hitting the hull has a thrust nuetralizing affect. In other words there are opposing forces because the thrust is pushing the boat backwards at the same time it is trying ot pull it forwards.

If there was some way to use the thrust hitting the hull to help move it forward you would have something new. Probably impossible though.

[yipster]

Volvo brought us the pulling IPS, who knows what 2006 brings...

[floater1]

Thanks for all the input. Bulbob...As far as the "nuetralizing effect",
something that never occured to me, what about a concave style hull. I have a Jammer Canoe that has a concave hull that seems to be effective by giving it a catamaran profile in the water. Would a hull along these lines work?

Thanks guys

[BulBob]

It may be possible a single or dual hull could be designed to generate additional speed from the dispersing thrust. It would kind of be like riding your own prop's wake to help move forward. It's pretty hard to visualize any significant savings in energy consumption but any is better then none.

[yipster]

tom kane suggested a displacement cat for the idea
or slow turning forward surface props may be able to ventilate the hull?
its as you said before "the answer is a little more complicated"
and it would be intersting to see some push and / or pull comparisons

[BulBob]

If there is current a boat will go the speed of the current but if there is an anchor line the current can make the boat plane to the side at a speed much faster then current. A continuously moving anchor could be the train of thought needed to proceed.

We're getting pretty far out there...I'm getting dizzy...

[BulBob]

If you can ride a self made wake (wave or or under water thrust) and a use a planing or surfing action to excelrate beyond the wake speed you should be conserving some energy. I just find it hard to believe that the energy needed to create the wake can be less then the energy it provides. The perfect prop would move the boat not the water. The perfect boat would use all the energy of the prop to move forward and leave no wake or turbulance.

[floater1]

Paul

Forgive me, could you please elaborate on your last post? I'm not sure I understand.

Mike

[yipster]

visit BulBop's site and you see what he means floater.
something else, if you have a canoe with a front mounted motor; how hard would it be mounting it astern?
i would be very interested in the different data

[safewalrus]

Apart from the obvious damage point of view, plus for larger vessels the comfort for the crew bit (Modern Oil Rig workboats tend to have everthing at the front - tends to be a bit uncomfortable at times but has other advantages, and like a lot of tugs, they tend to run around backwards a lot!) I believe the main reason is the fact that in the beginning, when propellers where first invented they were put on the back! AND being a conservative lot ( seafaring people) we tend to like it like that!

tis the good old cry

"if it was good enough for me dad it's good enough for me"

Yes but....... So will the inovative youngsters have a go and see what they can do (if it falls apart there'll be lots of oldies sucking their teeth and muttering "we told you so"). But ****! man never got to the moon without trying! Actually, now he's there it don't look worth a damn, but you gotta try!

[floater1]

The first Jammer Canoe I had a stern mounted motor, a 40# thrust, it scooted through the water at about 4 knots but didn't track worth a @#$%!
probably due to the concave hull. The one I have now is foot operated bow mount, travels about 7 knots and easy to put just where I need it, but it is a larger motor. Steering is vastly improved and I can hear what sounds like airation(sp?) under the concave part of the hull, and bubbles exit the stern area. By the way, this hull design is the most stable canoe I have ever used.

[BulBob]

OK - I like dreaming - You never know when you'll find that acorn - if your looking!
If I can come up with a patent anyone can. www.bulletbobber.com
One of the uses for my patent is for a life preserver but I am just trying to make fishing bobbers because they are small and reachable with my budget. I sent numerous letters to the Coast Guard and never got a reply.
I know that a life preserever with directional control could save lives.
A 1 million dollar grant would be good, after all what is a life worth.

Anyhow, I am just thinking out loud and if I need corrected please educate me. I'm not an engineer and calculs is beyond me but I tkink I can grasp concepts and find that acorn as well as anyone.

First off props are not as fuel efficient as wheels because they move water and a wheel does not move the road. This problem and the fact that there is a lot more drag in water then in the air. The basic problem with props is they are not positive displacement like a wheel on the road. We will not improve on efficency beyond the wheel but we can try to get closer. I was wondering if a better paddle wheel could be figured out and it brought back an idea I had for a windmill. A powered paddle wheel like this would provide more positive displacement and maybe easier to capture the wake or dispersing thrust to increase velocity. It is vertical shaft windmill with tall foils. This shows the changes to the limited swing foils as it turns. I did a hp conversion once and it looked like a 5mph wind could generate 1/4hp if foils were just 4'x8'. It also looked exponential gain for larger sizes. I don't trust my calcs.

[yipster]

did you read the modern pacclewheels thread?
looking for electricity windmill people told me clumsy (multiblade = less noise) normal windmills give way more efficiency.
drawing looks like a variable pitch savonius design?
so i agree but again think its more complicated than it looks