Max Speed Attainable with These Fgures

[phillnjack]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill

[phillnjack]

wow im shocked that nobody reading these cannot answer a simple question like this.

come on prop guru's...put down your answers...

and dont forget its miles per hour not kilometers per hour or knotts. mph is what i want.
it can then help settle a dispute.

[capnzee]

wow im shocked that nobody reading these cannot answer a simple question like this.

come on prop guru's...put down your answers...

and dont forget its miles per hour not kilometers per hour or knotts. mph is what i want.
it can then help settle a dispute.

@my guess is about 34 mph, @ 100% not much pitch and no rrrrr,s @2.9:1 Lucky to get 30mph on a boat Rod

[ima75man]

o.k. i like trick question. 29.8 mph at 8 % slip.. u might have faster water than we got over here.. or 32.1 at .01 % slip..

[phillnjack]

These are exactly the answer i was expecting .

its just a guy on this very forum with these exact figures says his boat is doing 39. ??mph
i said its impossible with that ratio,that revs and that prop.

others have chimed in and also say 40 is easy with that set up !!!!!!!!!
i think a touch of the niagra falls would be needed ha ha

but im glad that someone else sees it as around the 30mph mark and not me going mad

thansk guys


phill

[ima75man]

a lesson i learned early in life,never bet against the man making the bet.he knows something u don't.

[phillnjack]

ima75man
what would you call realy good slip figures for a race boat ?
and any idea what the average speedboat slip would be ?

[ima75man]

on a good race boat just a quess 6 to 10 % maybe 8 %.on a speed boat don't know to many varible to consider. just one person opinion

[zul8tr]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill

Max speed zero slip = pitch x engine rpm / (1056 x gear ratio) = 13 x 5500/ (1056 x 2.09) = 32.5 mph
If slip was 10% speed = 32.5 (.90) = 29.3mph.

For other data including slip use this

http://continuouswave.com/cgi-bin/propcalc.pl

[phillnjack]

these were the same speeds i got when i calculated it, and i also used the continuous wave gizmo as well to verify.
its juts that on another part of this forum someone said they have these very figures and the boat goes to 40mph on his gps !!!!!
i said its impossible with these figures and people have jumped on me saying its easy done and ofcourse its possible.

now being the stated engine and props figures etc the only thing i could see to make it possible was it being
measured in kilometers per hour and not miles per hour by the guys gps.
but he claimes his gps is 100% accurate etc and definitely miles per hour !!!!!!.
now a few other people chimed in and said i was totaly wrong, and with these figures 40mph is not uncommon,
and mathmatics is nothing compared to a gps reading ha ha ha

to my mind, everything speed related has to be a mathmatical piece to even get the speed, and a turning propellor at a given pitch and revs can only achive a certain maximum speed.

i know im from england and many things between our language can easily be mis-interpreted, but im glad that the guys
who do know their stuff agree that its only a possible 32.5 at best with these figures.

the boat is on this site and from the usa by the way,not in england, we have slow water.
thanks for all the input on this one,
youve all cheered me up and helped me re-gain a little bit of sanity


phill