Results 1 to 14 of 14
Thread: Prop calculation chart
05-09-2003, 10:33 PM #1
Prop calculation chart
Does anybody know if there is a chart for calculating props with RPM and slippage. Or is there just a formula?
05-09-2003, 10:35 PM #2
This is my favorite:
I have it saved in my favorites. It sure beats gettin' out the calculator. For gear ratio, just type in the first number. Example, for 1.87:1 as in Mercs, just type in 1.87
05-09-2003, 10:47 PM #3
Thanks it could become a favorite of mine also.
05-09-2003, 10:57 PM #4
I have that in my favorites too. 1 thing I noticed though, if you want to figure out your slip at anything over 100mph, it cant calculate it for some reason.Helmut
05-10-2003, 01:04 AM #5
I use this one
But it has the same problem as what stvhelm was saying.
upon further review. They look very similar to each other. HEHEHE. Oh well you have more boat sites you can go to now.
Last edited by outboards4life; 05-10-2003 at 01:07 AM.
05-10-2003, 09:57 PM #6
This is the one I've always used-- Gear ratio, If you've got 1.87-----1 divided by 1.87=.535 x .000946 x pitch x rpm = mph with no slip. you can take 10% off for slip normally. An example is my yellow flamer: .535 x .000946 x 32 x 8300 = 134.34 mph. My actual speed on GPS was 124 mph. to calculate slip, divide 134 by 124 = 1.08. The slip is 8%" IT'S NOT HOW FAST YOU ARE, IT'S HOW COOL YOU LOOK!!! "
Check out my new website. (IN PROGRESS) liberatorpowerboats.com
Things owned. NOTHING!!
Ain't got no toyz, Ain't got no money! I is jus a poor Florida boy!
Visit My Liberator and Checkmate Boats Website
Rent our Log Cabin in Pigeon Forge, TN. http://www.vrbo.com/419205
05-11-2003, 06:22 AM #7
Thanks for the links and formula, that is really helpful.
96' STV Euro
Smarta$$ of the Sunshine Syndicate,
How to upload pics (click here)
05-11-2003, 09:14 AM #8
If you want a real good one http://www.aeromarineresearch.com has an excellent one. You have to buy it but does all the crap without back and forth stuff. Change pitch or rpm or slip ratio what ever without refilling the boxes. Change anyone and all the others change to the new speed.
There is one thing about the calculators, they generally have one peice of garbage info (garbage in garbage out.) The prop is a guestimate of it's pitch, also the style changes the amount of slip that is "good".
Don't get carried away with them just use em as a rough reference, and forget about slip. High slip is sometimes the fastest props. Figured from emperical evidence.
Any prop comparision, same boat many props and styles will result in a very wide unreasonable slew of results. The props are a variable that can't be predicted with a number. The slip that results changes the speed that you get so it aint exact.
Slip can be ~14% - ~5 % Try both extremes and you'll see a big change.
The formula is actually a short hand version of the real thing. Rpms are measured in minutes and MPH in miles and hours, prop in inches. Convert the thing to the same units (miles and hours) and you can do it without the .000946 number- which is a conversion of those.'90 STV
for far too long
05-15-2003, 07:55 AM #9
I like this one.
93 STV Mod VP/MERC 2.5 200
"Do not take revenge, dear friends, but leave room for God's wrath. For it is written, Vengeance is mine; I will repay, saith the Lord."
“Resentment is like taking poison and hoping the other person dies.” St. Augustine
05-15-2003, 08:21 AM #10
damn, that one stops at 31pitch and 120mphHelmut
05-15-2003, 09:38 AM #11
That board has a download for the best I've seen.
05-15-2003, 10:02 AM #12
That is the one
The one on the Hydrostream site is the one I like too
05-15-2003, 07:17 PM #13
I want to thank all you guys for your help. All these sites are really cool. Thanks again Dave
05-16-2003, 11:08 AM #14Member
- Join Date
- Mar 2002
- Vero Beach Florida
- Thanks (Given)
- Thanks (Received)
- Likes (Given)
- Likes (Received)
- 0 Post(s)
- 0 Thread(s)
can any 1 tell me if the same formula applies when twin motors are used