Tantrum

There is no universal set-up on a "cat". With regard to rotation a 30' outboard cat and a 40' I/O cat have the opposite effect. This This discussion is worthy of its own thread. I would like to hear what the experts have to say, Im interested in learning more about this.

glassdave

iTrader: (1)

True and i understand there is no universal rule for rotation. I am also interested in general info regarding this topic on cats. I know in the cats i have raced the first one that we decided to spin in on we got wet, that sucked for many reasons and the worst being it was the first race my parents ever attended On Ed's Talon if she gets into a slide or otherwise loose just feed her the coals and she settles right down. On the AMT i raced with Wahoo it handled great spinning props out but was very lazy on acceleration (three blades). We tried four blades spinning in and it was like we added another motor, she took off like a bullet but high speed handeling suffered. Ultimately the flip was a result of our inexperience in both setup and running and i am glad we both came away with just a lesson learned and a few days worth of cleanup. You are correct we may need a separate thread on this.

wot

First, I disagree w/your analysis; lots of great information in this thread, and I appreciate the history, facts and humor of it all.

Second, That Miss America X w/the Quad Allison's (maybe Merlin's?) is amazing!

Third, we spin out w/our cat outboard; but hear spinning in is faster; sacrificing handling.

Finally;

Who had the first (production) stepped hull?

"After trying several designs, his engineers discovered the stepped hydrofoil hull"

"In January 1912, Curtiss debuted his first successful flying boat, The Flying Fish, which incorporated the stepped hull"


Glenn Curtiss & The Curtiss Company
Like every other technological leap, it origins are military. Albeit a Flying Boat, it is a boat and the first production power boat w/a Stepped Hull.


http://www.centennialofflight.gov/es...tiss/Aero2.htm

glassdave

iTrader: (1)

i believe they are Packard Silver Cups (predecessor to Allison/Merlin) and yes that thing is amazing. Ed has it at his shop once in a while and i get to take a close look.

Funny thing is when we first tried the four blades over the threes on the AMT it would not turn at all with the props rotating out. I mean AT ALL. We were testing and running down the St Clair river at roughly 115 and Dean turned the wheel lock to lock with almost no response. Tried several different prop heights and nothing seemed to work with those props. Spun 'em in and she took right off, rode ruffer but would turn. Problem was when we initiated a turn it started to set then grabbed/hooked and Dean would have to over correct big time. We tried to figure it out but ended up wet. After that i looked into it further and got a lot of opposition to spinning in on race boats. I will say this though i do see many teams spin in successfully, its the first thing i look at in the pits.

T2x

Sorry about that ...Senior moment and I corrected my original post....I meant "spinning in" which in both hull types , cats and vees, produces the dynamics I posted earlier.

This age thing is a pain in the *ss....

glassdave

iTrader: (1)

gotch'a and point noted. (glad i only hafta remember one fact now)

T2x

Wrong...... Somehow some nonsense about inboards being immune from the laws of physics crept into the mess.

In reality torque is torque, props are props, leverage is leverage and there is no difference in the handling problems created by spinning in for either type of powerplant. A good friend of mine, who I otherwize respect, once postulated that a 36 Skater sterndrive can never run with the drives spinning out..........which is absolute nonsense. Sadly a number of other riggers and throttlemen picked up this mantra and ran with it (more "monkey see--monkey do", a phenomenon that has been around as long as boat racing). As a result of so many guys running their props "bass ackwards", certain hull builders have tweaked their bottom tuning to gain some speed with reverse rotation (sacrificing some lateral stability in the process), but to me....2 wrongs don't make a right.

phragle

iTrader: (3)

Miss America X motors


They are Packard 4m-2500's

12 cylinder, gear driven superchargers, unmodified produced between 1100 and 1500 hp (depening on mfg. date), max unmodifed rpm: 2400, weight 2900 lbs.

the engine was based off of the Liberty aircraft engine.I have piks and specs, but I cant post them.

Also on this boat, the rudder was mounted about a 1/3rd of the way back from the bow as opposed to the stern and foreward of the step.

Tantrum

Physics are mathematical facts. Torque is torque, props leverage...Im with you here. My statement was there is know universal set-up for a cat. From my experience in cats that Ive owned...
30' AMT Outboards, spinning out was the safer more stable, better handling set-up. If you wanted to hang it out and go for a top end number, hold on and spin them out I spun mine in.
39' MTI and 42' MTI I/O's
Spinning IN is the more stable better (overall) handling option. To get a top end number spin them out, put on big wheels, hold on and run it loose to the top. I spin them in.
There is a balance between physics (facts/text book) and real world running (reality).
Design, rigging, etc obviously play a part, this discussion would make a great thread which I know I could learn a lot from.

Coolerman

The new 388 Skaters are spinning the props out.

I will say, when spinning out on our 43' BT, the boat drives like a go cart to 100mph. Past 100mph, the thing chinewalks all over the place. The props just lift the stern too far out of the water past a certain point. We tried many bottom mods trying to make it work spinning out, and no matter what, past 100mph, it just didn't work.