Fred and Tom,

Good to see you back Fred! Says alot not only about your integrity but the guys running OSO as well.

You know, if the engineers on this board are laughing at what you said Tom, then I'd imagine Fred and I are road kill on the highway to the math lab.......

As to labbing, that process essentially sharpens the leading edge, reduces the thickness of the blades, and makes each blade as close to identical as possible.

I still believe there is some black art to prop design and thus the secrets that may exist are secrets that work on a particular set up, but don't stand up to universal application. I can tell you that Benny and I shared our props all season with any other team that wanted to try them, and I know that many of the other teams would let us try their props as well. We figure there is always something out there that is faster (whether built by someone else or from our own torch and hammer than what we have and if we stop testing, we'll never know.

Same goes for my Unlimited Hydro ride. We've bought props from our strongest competitors, and lent ours to them as well. In Unlimited Hydros, we run surface piercing 3 blades. Max diameter is 16" and average pitch is between 24 and 26 inches. Average rake is between 20 and 25 degrees. With less than 20% of the blade area in the water at app. 200 MPH and app. 9,000 shaft RPM we're down to about 5% slip?? That kind of makes the graphs and charts tough to correlate......

Tom, if you can graph the data, the next time I'm testing props, I'll keep accurate RPM/Speed notes from 3,000 RPM up to WOT and maybe from that info we'll find the most efficient RPM and speed. I can also give you the numbers from our dyno runs for the correlating RPMS so you can plot torque/HP/RPM and speed.

We hope to be on the Dyno within 3 weeks and on the water two week later.

Thanks again!

Hi Steve, Interesting what you said-- small pitch 24-26", fast shaft rpm, 'high X'-20% blade in the water, low slip-5% and at peak torque-- turbines have a flat torque curve. What does this say we should do to our pleasure boats. Your testing and results are allways so interesting and helpful. Marty.

Hi Steve:

How does this work when applied to a propeller beanie?

T2x

T2X,

You know darn well what happens with a high X dimension beanie How are you buddy? Please give my regards to Darren and get one of our Unlimited races on your travel schedule this season.

Take care,

Steve

Marty, I'm afraid what works on the Unlimited doesn't translate very well to our pleasure/performance boats. The closest comparison would be the Arneson drive which works great on some hulls, but isn't real friendly in terms of family use IE: You wouldn't want to jump off the transom to go swimmming ..............

Steve,
What are you going to be running this year? Are you going to run both series, sbi and hydros?
Until we can simulate how much deflection occurs when the prop enters and exits the water, we are guessing. It would be very interresting to see what your props look like at 9000 rpm
In all the good props we ever had that we tried to have duplicated they were never the same.
We digitized a pair of props once. There was not one blade front or back enen close. We were looking at making 10 props to try to find out which blade was right. not cost effective. There seems to be a lot of black majic and cohursing when a prop is made. We are still looking for the best though.
Every boat does seem to have a perfect prop though. We try to adjust the ratio to match the conditions but when we start getting close to some good data we loose the prop. Oh well... take it easy.
pat W

Hi Pat,

Interesting what you experienced in prop design and near impossibility of duplication. Our unlimited wheels most definitely fatigue. The trick is catching it before it throws a blade. THey are magnafluxed after each run. We also check "lay back" of the blades, which becomes measurable after only a couple of laps. When it does throw a blade, all hell breaks loose, normally taking out the strut, prop shaft, shaft log, sometimes a gearbox, and sometimes an engine, as well as some section of the boat bottom and transom. Our props are over 40 pounds, so when one blade goes the out of balance inertia will knock your fillings out.

When we're in San Diego this year, drop by Pat, and our prop guy, John, will take you thru the die check and magnaflux process.
We would appreciate your input on any improvements we could make.

I'll be driving the U-6 again this season, our sponsor O Boy! O Berto sausage company of Seattle has re upped for the 2002 season. I'll be throttling the FOUNTAIN GMC F-2-75 boat with Bennie at the wheel, at SBI races that don't conflict with the Unlimited events. This is the canopied 35 FOUNTAIN we ran last season.

Thanks for writing Pat, look forward to seeing you guys again.

Steve

I love reading posts from you guys. Much of it reminds me of how little I know, but I still find the posts educational and interesting. If you keep writing, I'll keep reading.

Steve, good luck this season. I'll be cheering for you and when you're in NYC, please call me. Would love to show you and your better half around and go out to dinner. I'm sure I can get some of the guys from CT and the surrounding area to join us.

Rich, can't wait to see your 28 when it's finished. I'm sure it will be awesome.