Reply With Quotev-kid most boats slip will be 10 - 20 %. The only true way I know how to figure slip is GPS the boat, then calculate what the speed should be at that RPM.
If you use 20% you can't go wrong.
Back on dec 28 01 you posted info on a prop,speed,gear ratio calculation formula and you guys used the term slippage im guessing thats like traction of the prop ? and how do I figure out the slippage of our 16ft rayson.If I know the %overdrive, RPM,slippage and speed Id like to reach in what order would I use the formula to choose a prop
Thanks Kid
v-kid most boats slip will be 10 - 20 %. The only true way I know how to figure slip is GPS the boat, then calculate what the speed should be at that RPM.
If you use 20% you can't go wrong.
I vote for 25%
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LeE ss13
V-Kid,
Slippage is a "guess" and varies with many conditions. As the others said, the only way to varify it is with a GPS. I did this with my little Beezer and it figured at about 13 - 15%, which seems low compared to some of the others...
S&S
I use 15% slippage for a typical 18' flat with a 11.5 x 15 prop. The smaller diameter prop, the greater the slippage factor on the same size boat. I confirmed the speed with a SFPD radar gun.
Originally posted by Stab-n-Steer:
V-Kid,
Slippage is a "guess" and varies with many conditions. As the others said, the only way to varify it is with a GPS. I did this with my little Beezer and it figured at about 13 - 15%, which seems low compared to some of the others...
S&S
That is one very efficient Biesemeyer !! On a side note.... I have not used a GPS. Has anyone compared their results with say running through timing lights on a closed course? Is the technology absolute? I mean to say is there any + or - percentages? What I used to do was compare the RPM myself and other guys would run at the drags and come up with a percentage, but I know that the "trap speed" is merely an estimate. Just a thought.
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LeE ss13
LeE ss13,
The GPS's are very accurate. My kid has a GPS and a CHP buddy of mine took me for a ride in his black and white and the GPS was dead nuts to his "calibrated" speedo... We took it up to over 100 and it was right on the whole way...
My little Beezer is not like what you guys race, it's a '58 and only 16'with a top speed of about 65mph. It stands to reason that the bigger the boat, with more HP, more pitch and the faster you go, the higher the "slippage" factor would be...
Are you racing this season? I did not see your boat listed on the Super Stock Website.
I did check out the pictures on your website. Cool! I love watching the Super Stocks. I'm planning to go to Burley this year... Hope to ride in a Cracker this season.
S&S
I ran 3 races with my SSRS buddies last year. Parker, Long Beach, and San Diego. I didn't join the SSRS series, (which I will do this year), but they were all APBA races so I got APBA points but no SSRS ones. If you have been following their Web site, they dropped the Parker race in April as a SSRS race even though it will go on as an APBA race. I'm making some calls to find out why? I'm worried about what impact the loss of Lance will have on the series. The other big concern is that APBA may start pushing for 'Reinforced Cockpits' in the Flatbottoms and the GN boats. (again like they did in '95). Lets face it, the Flatbottoms and the GNs are the last boats in circle racing that even look like boats that average boaters might own. This could be bad for these classes, because the numbers of racers would go down.(I think). Just my $.13
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LeE ss13
Hey Larry,
I'll email you direct and let you know what's going on; I was at the meeting in Vegas. Even though it isn't a Series race, we plan on being there to shake down our boat. I'm sure there will still be a strong showing of SS boats there.
Scott
I'm getting almost 30% slip according to gps. My boat rides flat and is stuck to the water. I have 22% gears and a Menkens 11.25 x 17 2 blade. I have found that running into the wind and chop changes rpm by 300 or more with no change in speed. Can someone tell me how to get this boat to air out without bouncing? It is a true flat Sanger, no hook that I can see, motor and prop are in stock position. Look here for pics:
http://community.webshots.com/user/detroitjim
It has always bounced bad over 50 with any prop, gear, small block, big block. I'm running 94 now with the plate locked 2 notches down. It feels like it is going to nose dive.
Any Help?
Jim
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