15 400R news

[Risco]

I had a guy measure and draw up a gear set that has one more tooth on the pinion than a 1.62 : 1 which would make it a 1.48 : 1
Just as a 1.75 : 1 has one less .
It's like everything else , would it be worth the effort , and how many people would buy a set .... ?


[/INDENT][/QUOTE]
Just wait a few years when there used 400r and they we be bolted on anything that will float them. I know there a point where the prop pitch losses effiecenticy vs diameter. Where that is I don't know.

[noli]

Noli,

You better talk to Grant. The only wheels living on the 400s "that have the motors elevated" are the merc CNC and they are pricey.

Joe

The customer is def going the MercuryRacing CNC route.

I just like to get more info on new products. If DeWald is building CNC props that will go head-to-head with MercuryRacing CNC and the price is lower, might be a viable option. DWalds have traditionally performed very well for us and will only be time till he equals/exceeds the best of the best...just my opinion


This is just a "what if".....what if DeWald exceeds MercuryRacing CNC prop by 4MPH? I think a few boaters will be ordering CNC DeWald props.






.

[JPEROG]

That would be great for Dave if he is able to get the alloy compound that they have created. He is a good guy and deserves everything good that happens.

Joe

[powerabout]

So I take it that your answer is .... No , you don't know the range of optimum efficiency .

what are you looking for a ratio based on what?

If that were true , there would be a low pressure area equal to the rooster tail out in front of the leading edge .

What do you expect to see, the suction side of a blade in the air isnt doing much

Yes sir , without question . A new level of cost to go with them will keep them out of most people's hands ..

for sure.

[Chaz]

what are you looking for a ratio based on what?

I never mentioned diameter , area , ratio's of any other misleading criteria .
Here was my question :
Has there ever been any testing to see where the cut off is to where a prop is too small and pushes little water vs. so much angle to where the blades just slap the water and act more like a Mississippi paddle wheel than a screw thru the water ... ?

The theory behind prop sizing is that it will move X amount of inch's for each time it spins one revolution .
Just as an airplane with a variable pitch propeller will be run up with little to no blade angle and then the pilot will throw the blades back and go .. he certainly doesn't go back to 90* and slap the air to get a lot of drag and the same amount of thrust as when the blades were at 0* which is none .
Then the same has to hold true for a propeller in the water ... where has testing proven to be the sweet spot ... ?

What do you expect to see, the suction side of a blade in the air isnt doing much

for sure.

I expected you to prove where a full 50% of thrust is generated by suction . It was your statement , not mine .

[Capt.Insane-o]

I expected you to prove where a full 50% of thrust is generated by suction . It was your statement , not mine .

I used to know a girl........

[Chaz]

With the exception on the progress in the development of airplane engines during World War II, American companies have made very limited contributions to the development of the internal combustion engine. That goes for Otto as well as Diesel engines. They have mostly copied what European companies have pioneered...

Which is probably a good thing for you we did . Unless you wouldn't mind being part of the 1000 year Reich .

A couple years ago , I built a new set of zoomies for Adam Flemholic's Pro/Mod car . He is a fellow country man of your's . I guess you would be shocked to know that they were built for the latest BAE Chrysler head , instead of a Volvo .

Heck , I'll bet there are more Ford's and Chevy's in Sweden than Volvo's ..

How many 1000 cubic inch , multi nitrous kit , motors are put together each year using non American parts .

Something equal to twin turbo LS motor's ... ?

Nope , I guess it's the same old story . We invent it , the land of the rising sun reverse engineer's it ... !

Got crumple zones ... ?

Capt.Insane-o

I used to know a girl........

I think I went to Jr. High with her sister ...

[H2OPERF]

With the exception on the progress in the development of airplane engines during World War II, American companies have made very limited contributions to the development of the internal combustion engine. That goes for Otto as well as Diesel engines. They have mostly copied what European companies have pioneered...

Whaaatttt....Really... and yes be glad we did and still do build the worlds most powerful aircraft/engines or we all would be speaking a different language.. Lets hope there is never another world war....If so I think most of the world will be glad we have what we do here and its allot more than the we see, you don't park SR-71s and space shuttles without replacements...Way off subject but I LOVE MY COUNTRY....

[powerabout]

I never mentioned diameter , area , ratio's of any other misleading criteria .
Here was my question :
Has there ever been any testing to see where the cut off is to where a prop is too small and pushes little water vs. so much angle to where the blades just slap the water and act more like a Mississippi paddle wheel than a screw thru the water ... ?

The theory behind prop sizing is that it will move X amount of inch's for each time it spins one revolution .
Just as an airplane with a variable pitch propeller will be run up with little to no blade angle and then the pilot will throw the blades back and go .. he certainly doesn't go back to 90* and slap the air to get a lot of drag and the same amount of thrust as when the blades were at 0* which is none .
Then the same has to hold true for a propeller in the water ... where has testing proven to be the sweet spot ... ?

Sure its been done all the time, when you cant get on the plane you need more blade.

I expected you to prove where a full 50% of thrust is generated by suction . It was your statement , not mine .

Its a fact of life , testing comes from the commercial world doing bollard pull tests then towing. It called current inflow, once water is being pushed onto the suction side of the prop the thrust Bollard pull drops off dramatically, hard to prove its 50% but thats the rule of thumb.
Any Naval Architect will know this.
I work in the offshore industry with Dynamic Positioning vessels, the designs always shows how much thrust the prop looses in current which could be something like 6%/kt

[H2OPERF]

Power I can understand your point its all about high and low pressure areas but I would think the hydrodynamics of a submerged contoured prop at 75 or 100 rpm would be totally different than a prop half out of the water at 5000 rpm. Chaz i bet those top fuel/unlimited guys have the sweet spot figured out.. I was told by one of the unlimited guys way back in t marine stadium days they didnt use big pitch props, its more efficient to spin an small prop faster, think he said they turned them like 15000. Dave

[powerabout]

Yes but i dont think you can change the theory of a prop
You cant compress water and throwing it into the air is wasted energy.
Lets just make sure nobody uses the term efficiency in a prop discussion. Its either a tug boat or it goes fast
The ideal prop would be variable diameter and pitch and maybe rake to match the torque curve of the engine that hopefully matches load from the boat.
F1 tunnel boat small pitch and 10k, wont pull a waterskier though as blades will be overloaded and it will cavitate even if it was deep.
Add some blades or diameter or reduced pitch etc maybe lower the ratio to get your skier out and it wont be the fastest any more

[XstreamVking]

It's not scientific, and put in very simple terms, but I was told by an old outboard racer that after about 28'' of pitch the prop loses the "screw" effect to some degree. And the lower pitch, higher r's race boat setups seems to illustrate that principle.

[H2OPERF]

X stream agree. Power Not trying to argue or anything like that this is all interesting to me an i'm not an engineer by any means and wish we were drinkin a beer having this conversation lol, just hard in my mind to compare the two, so basically best thrust is at the point just before cavitation begins..low pressure on the front side but not low enough for the air to come out of the water and cavitate giving you more thrust on the positive side of the blade due to pressure diff. I think i"m getting it... our boats are so light they move foreward at the rate to keep the cav away, smaller prop not enough blade to move the boat and water cant fill the void fast enough cav and off plane you go. Never really though about it that way. Ok you guys can have your verado thread back PS i just rebuilt a stupid prius engine for a friend hope you guys know what your getting into.. you can have the cam buckets chain tensioner and all that crap , i would rather rebuild 10 v6 two strokes than another one on of those freakin things. Dave

[Chaz]

once water is being pushed onto the suction side of the prop the thrust Bollard pull drops off dramatically, hard to prove its 50% but thats the rule of thumb.

Any Naval Architect will know this.

Water being "pushed" . Somehow it must know the prop is coming along any moment and produces an artificial high pressure area ..

Funny thing happened the other night . I had a piece of Key Lime pie after dinner .
(they didn't have canoli's)
As I sliced downward thru the pie with my slightly angled fork , the larger portion ( the whole ******* ocean) stayed put , while the small portion that I cut off , moved rearward the thickness of the fork initially and then followed the contour (angle) of the fork.

To a much lesser effect , there is a low pressure area created on the back side of the blade that will never move enough water to have it join back together in the same place it was sheared from . It is the same principal that gives an wing it's lifting (or downforce) characteristics .
To prove this drop a piece of paper 1' behind a fan , then at 3' . At some point early in the game , the paper will become lazy and will no longer be drawn into the fan . While on the thrust side , the same piece of paper will be affected on the other side of the room .
At that point divide the smaller number into the larger one to get a "real world" ratio .

While I'm no Naval Architect , I attend the school of GOBIT ( that's the Good Ole Boy Institute of Technology ) on a daily basis ...

Power , just curious . Does the rest of the Engineering / Architectural community ignore 90% of the fact's presented , while after careful analysis respond to the remaining 10% with a totally benign non relevant response ... or is it just you ..

XstreamVking

It's not scientific, and put in very simple terms, but I was told by an old outboard racer that after about 28'' of pitch the prop loses the "screw" effect to some degree. And the lower pitch, higher r's race boat setups seems to illustrate that principle.

Just as I was told that when Mercury Marine spent a small fortune developing their propellers , that 24" was the sweet spot and 28" was the edge of efficiency .
Maybe not as fast as electronics go out of date , but much of what is known about props seems to change pretty rapidly . Hard to tell if they have bent the laws of physics , or working on their used car salesmanship skills ...
Hard for me to understand it , but guys are willing to buy a few sets of prop's that are built to the extreme side of what is considered the normal range , yet wouldn't dare explore moving into a gear set that brings you back to the sweet spot .. maybe that's part of the reason that one company's 32" is tighter than the next one's 34" ....


H2O , a Prius , a friend , she must be a very nice young lady for you to get involved in that ...

[FORBESAUTO]

But Chaz, I don't understand. On paper it works!