PDA

View Full Version : Slip Question



Sweet Cheekz
04-20-2009, 09:56 AM
What are the drive ratio's for an Alpha ss? I am trying to get a feel for the slip on my boat with the performance runs I have so far. 4900rpm's 73.2 mph 26 pitch 14 3/4 diameter prop Any opinions? Thanks

VetteLT193
04-20-2009, 10:15 AM
should be a 1.5 that puts you around 8% slip

Sweet Cheekz
04-20-2009, 11:11 AM
Seems a little low?

VetteLT193
04-20-2009, 11:23 AM
Seems a little low?

what seems low, the slip?

Conquistador_del_mar
04-20-2009, 11:29 AM
If the drive is 1.5 ratio, I calculate a theoretical speed of 80.43MPH. 8% is about right - very efficient if the numbers are right. Bill

mattyboy
04-20-2009, 11:32 AM
I would say you are pretty much dialed in there

Sweet Cheekz
04-20-2009, 11:38 AM
Alright then On to the next detail
Thanks Guys

Just Say N20
04-20-2009, 11:45 AM
Alright then On to the next detail
Thanks Guys

Hmmm. . . .

So, if you could turn the engine to say, oh I don't know, 5,600 rpms with about the same slip, top speed would be . . .

. . .a really big number (84.6 mph). THAT WOULD BE VERY IMPRESSIVE!

Sweet Cheekz
04-20-2009, 11:55 AM
Hmmm. . . .

So, if you could turn the engine to say, oh I don't know, 5,600 rpms with about the same slip, top speed would be . . .

. . .a really big number (84.6 mph). THAT WOULD BE VERY IMPRESSIVE!

Motor dynoed at 5600 r's The boats not loose at all yet so I am thinking I have a ways to go. It was bumpy Saturday Maybe early morning Lake Cumberland in a few weeks? NK

VetteLT193
04-20-2009, 12:30 PM
if the prop is cupped, the slip is higher... what kind of prop?

Alphas are not high rpm friendly.... I'm not sure if the SS is much different.

mattyboy
04-20-2009, 12:41 PM
if the prop is cupped add an inch of pitch when doing your calculations, Rootsy ran his SS on his 16 up to 80mph I think there is a heavy duty gear set?

Sweet Cheekz
04-20-2009, 06:19 PM
Grizz says it's a TXP I think 14 3/4 x 26 3 blade

BigGrizzly
04-20-2009, 06:31 PM
Relax people He is getting seat time. He has not run in premium conditions and he has a giant gas tank. This guy will not do something stupid ha has gone faster then 90% of us and loves life. Trust me on this he has put $$$ more fuel in his last go fast boat in one summer then he has money in this boat. This is a new era for him and is having more fun then he has imagined in building this once was wreck.

Sam
04-20-2009, 09:23 PM
I'd say your your doing ok given your RPM. If you choose to stay where your at 4900 rpms will give you a long service life. I have an Alpha SS on my 16 and see 5000 to 5100rpm's with speeds from 70 to 73 mph. I currently run a 4 blade Hydromotive (24.5"). If you feel confident in you motor running at 5600 rpm I'd say your leaving some speed on the table. I'd be interested to see what Griz may have for you to try. I know I'll be looking for some test wheels at AOTH......hint hint Griz :yes:.

Sweet Cheekz
04-20-2009, 10:09 PM
Hey Sam
Looking forward to meeting you at aoth. Griz and I talked about another test prop but he's right I have yet to get the right day to really ring it out. You mentioned to me a while back about some chinewalking at high end Do your top speeds reflect some hairy moments? When trimmed properly my boat is running on rails between 70-74 which makes me think I have a ways to go. I have yet to make a speed run with less than 30 gallons of fuel and I have had really choppy water. I will have one more weekend before aoth to run it and get a speed run b4 heading south we'll see what happens with a little more seat time See you there and your welcome to try my prop down there
Parnell

BigGrizzly
04-21-2009, 09:49 AM
Sam you say the sweetest things. I love talking to Parnell, the joy he has about this new territory he has entered is nothing short of inspiring. On a bad day he is happy.

Sam
04-21-2009, 06:57 PM
Parnell, driving the sixteen at high speeds (68mph +) is just that, you have to drive the boat. From my experience I get a better ride with some chop, it's also a faster ride. When I was prop testing hot and heavy I was seeing speeds right around 74mph using a variety of 3 blade props. I have to tell you that at that speed and using those props it was darn right hard to keep the boat in a safe mode. It was like the boat was on crack :eek:. Give me a shout anytime in the meantime I'll be looking forward to seeing you, Griz and all my Donzi friends in a few weeks.

Sweet Cheekz
04-21-2009, 07:38 PM
Thanks for the info Sam See you in a few weeks
Parnell