Geekdom

[noah45]

I need to know who has any knowledge of Hydrodynamic Shapes and how i can make some hydrodynamic simulations to prove that a Personal Watercraft that I designed works!


I am a designer that banged his head on this major problem, to demonstrate if my shape works.

 

[tor*p*do]

scale models.


make some of your design and incumbent designs and compare in a water tank. use strain gauges to measure drag, lift, etc

 

[gj_fx1]

working with scale models takes a lot of expertise and in the end gives you only an approximation of how the hull will behave at full scale. For something as small as a PWC you might as well just do full scale testing.

 

[noah45]

Yeah, already have the SOB in full scale, @ 220lbs. (including) a 750cc modded engine. It's based on the 650sx hull, cut down to 5' long, but I extended the back out to where it tapers to 4' (sounds retarded, but I had my reasons)

I thought a 750cc @ 220lbs PWC could have pulled almost anything up on plane, but it won't pull this shape up.

Knowing I'd have to deal with cavitation later..

Design isn't easy, especially when your trying something radically different from convention, I have a new respect for 'water'....

 

[tor*p*do]

well noah,
post some pix of your ark
and maybe someone will post a meaningful suggestion.

 

[Speedfreak]

I thought a 750cc @ 220lbs PWC could have pulled almost anything up on plane, but it won't pull this shape up.

Wow sounds like you forgot to pull the anchor up. A modded 750 SXI will pull a small ski boat up on plane. So that sounds like something is really wrong.

 

[noah45]

Wow sounds like you forgot to pull the anchor up. A modded 750 SXI will pull a small ski boat up on plane. So that sounds like something is really wrong.

That's what I thought, I even had Impros repitch a prop to 9/17. The hull is a shortened version of the 650sx. I don't have any shots of the hull.
But what could be "really wrong" besides the drag of the hull. (5'long 4'wide)

Engine misalignment?
Enough air intake?
pump bearings?

 

[Speedfreak]

Engine misalignment?
Enough air intake?
pump bearings?

Could be any of those things. I pulled a 15 or 16 foot runabout with 2 people in it and maybe a 75 HP outboard. I pulled it across the lake and at the end of their tow I just hammered it and it took a while and they helped by moving from the rear to the front of the boat but I pulled them up on plane.

Can you give up a description of the design?

 

[BlueBreadTruck]

wow....a stock 750 dual carb engine puts out roughly 75hp stock.....modded quite a bit more! something is really wrong if it cant pull a 650 modded hull....unless there is some SERIOUS drag. post pics so we can possibly help

 

[noah45]

Someone told me, dude strapped 10hp on inverted dining table, and it planed

As much as I appreciate the help, we've only slightly protected this w/ a patent pending, I can't publicly disclose the idea. My partners/investors would crucify me.

I can shoot a simple diagram, of the hull. This 'arrow shape' I think is what's causing all the problems. The next step, is to 'clip the wings'. Th reason is; even if the all the mechanical problem are happening, (side note; engine runs really strong), The fundamental problem is how this 'shape' is pushing and dragging the water.

 

[thegoldenboy]

It your design a cement block?

Good luck with it. I'm not smart enough to post in this thread anymore.

 

[noah45]

It your design a cement block?

Good luck with it. I'm not smart enough to post in this thread anymore.

to the blond canadian, " how is that respectful?"

Radical design isn't something for pusses, unless your doing a whimsical
something.

 

[gj_fx1]

Someone told me, dude strapped 10hp on inverted dining table, and it planed

I believe it was Carl Kiekhaefer pulled that stunt and used it as an ad for mercury outboards in the 50's.

 

[gj_fx1]

so does your wedge point nose high or stay flat and plow?

 

[sflsurfrider]

it looks like the problem is that the 'wings' are trying to 'push' the water out of the way instead of 'climbing' on top of it.... but thats without seeing the hull.

could you post some pics of the bottom of the hull?

 

[Speedfreak]

it looks like the problem is that the 'wings' are trying to 'push' the water out of the way instead of 'climbing' on top of it.... but thats without seeing the hull.

That seems like it would cause a major problem if the hull was a flat surface but if there is any kind of a v hull to it it should climb on top of the water easily. My tunnel hull has a center section shaped exactly like that. We need a profile drawing

 

[sflsurfrider]

That seems like it would cause a major problem if the hull was a flat surface but if there is any kind of a v hull to it it should climb on top of the water easily. My tunnel hull has a center section shaped exactly like that. We need a profile drawing

if it is a vee hull, it would have to get progressively wider toward the back which would cause drag.

the only way i can see that working is if its a tri-hull.

 

[noah45]

the 'wings' are trying to 'push' the water out of the way instead of 'climbing' on top of it....

I think that's exactly what's happening, the 'push' combined with increased 'wet' area towards the back.

I'm 'clipping' this birds wings....

thx for the input

Stayed tuned

 

[Speedfreak]

I was talking about being a deep "V" so basically is would have the same footprint so to say as a regular fishing boat when sitting in the water. Sitting low or deep in the rear and just the point in the front.

 

[noah45]

off subject.....gj_fx1, I noticed your avatar.... (I'm an old man, 48) and saw Kansas at a small venue in Buffalo, year 1976. great show, they were touring with Todd Rungren.

for what it's worth....