Like Tree0Likes

Tips for driving stepped bottom boats

Reply
Old 04-25-2003, 10:19 AM
  #31
Enjoy the show
VIP Member
 
Ron P's Avatar
 
Join Date: Feb 2001
Location: The Joisey Shore
Posts: 10,353
Default

This was posted by T2x on the cat thread and I thought it really belonged here......
====================
From: T2x

Ron P.--My thoughts on "spinning" in..... Simple physics.... Right hand rotation propellers,torque (lean) the boat to the left. Left hand rotation propellers torque the boat to the right. In a twin engine boat spinning outboard or , RH on right side, LH on left, the torque of the propellers tends to return the boat to level when one side or the other leans outward. When props are spun inboard RH on left, LH on right, or counter rotated the torque tends to make the lean worse. This occurs because as a boat(Cat or Vee) leans to one side, the prop on that side buries deeper and exerts more force, while the prop on the other side rises (in some cases out of the water) and exerts less force. So...... If a RH prop is spinning on the right side of a boat leaning to the right, the prop tends to push the hull back over to the left. (spinning Outboard). If, however, the left hand prop is on the right side in a right hand lean , the prop tends to continue to roll the boat over. I submit that this is why there has been such a dramatic increase in barrel rolls (even in straight-aways) in races in recent years. When I flew over races for 16 years, I could always spot the counter rotated boats, because they behaved very differently (and definitely not better)than their properly spun (outboard rotation) competitors.
The reason that many people spin them "backwards" is the fact that on some hulls the boat may gain a mile or two per hour at top speed....or..... the boat has a bottom tune that needs more bow lift. The speed can generally be achieved in other ways without using an unnatural rotation as a "bandaid" (This is particularly problematical on stepped bottom boats that skid first, then catch suddenly, then roll outward......get the picture?)
One can re-tune most bottoms to add rocker to provide bow lift without resorting to ill advised prop rotation changes.

Counter rotation is adviseable on SINGLE engine race boats when the courses change from counter-clockwise to clockwise. LH props like right turns and handle better, RH props like left turns. Since the Bravo drive allows for a simple flick of a lever to reverse rotation, one would expect that Factory 1 racers would have a supply of left and right props depending on the course ....... up until this year most F1 racers don't...... I guess nobody has "invented" this yet.
Ron P is offline  
Reply With Quote
Old 04-25-2003, 10:22 AM
  #32
Enjoy the show
VIP Member
 
Ron P's Avatar
 
Join Date: Feb 2001
Location: The Joisey Shore
Posts: 10,353
Default

I posted this from the Great Moments in Cat History.

I have spoken to many people about this and it seems that V bottoms will become a handful to drive with the props spinning inward.

If your manufacturer stuck the drives on with an inward direction, you might want to swap them to spin out for safety reasons. And yes, you might give up 1 mph if you do so. You might also enjoy a better handling boat.
Ron P is offline  
Reply With Quote
Old 04-25-2003, 10:26 AM
  #33
Registered
 
BODYSHOT1's Avatar
 
Join Date: Feb 2001
Location: Freehold, NJ. USA
My Boats: Thoroughbred/Velocity 32'
Posts: 5,367
Default

..Vin & I just mounted our drives last weekend..spinning out..per Velocity & all that I've heard from the "experts"....

my .02
BODYSHOT1 is offline  
Reply With Quote
Old 04-25-2003, 10:37 AM
  #34
Rough Seas Lie Ahead
Gold Member
 
Reckless32's Avatar
 
Join Date: Feb 2002
Location: Virginia Beach, VA
Posts: 2,465
Default

mlitefan glad to hear you got to go out and run it a bit. Can't wait to hear impressions/thoughts on the possibilities...

As far as the step driving goes, the Sunsation is a tad unique in that it's step is only partial and runs inboard only to the first strake. Sort of gives the best of both. I believe the Sunsation step is more for planing a little quicker than for WOT advantages. If you've ever seen a picture of a 288/32 running trimmed up you'll notice the "semi-steps" are running out of the water...

But the Sunsations do have a little nuance and that's bow steer. Their noses are long and therefore requires a tad trim up to cut it hard otherwise the nose will dig in and cut hard.....I learned this within the first few days of operating it while dialing in the operating envelope. If you lift the bow a tad she'll turn as hard you want it to...
Reckless32 is offline  
Reply With Quote
Old 04-25-2003, 10:38 AM
  #35
Registered
 
Join Date: Jun 2001
Location: Michigan
My Boats: It's how well you go fast
Posts: 3,345
Default

you may want to test for yourself...again...stop looking for absolutes.

if the manufacture set it that way...ask them why...they may have just done some testing??what center are the drives at??...what percentage of the blades are exposed on what stroke??...how was the propeller designed...a boat that bow steers is EVERY bit a handful as a boat thats ass is too light.
audacity is offline  
Reply With Quote
Old 04-25-2003, 10:46 AM
  #36
T2x
Allergic to Nonsense
Platinum Member
 
T2x's Avatar
 
Join Date: Aug 2001
Location: Granite Quarry, NC
My Boats: 1966 !8' Switzer Wing "Miss Diablo" 1968 Switzer Wing "Dust'n the Wind 2",, 1960 Powercat 15C , 1977 17' Molinari w/Evinrude CCC
Posts: 5,004
Default

Quote:
Originally posted by audacity
...a boat that bow steers is EVERY bit a handful as a boat thats ass is too light.
Joey.... I believe that both circumstances you described above are actually the same thing. A loose rear pivots on the nose in either case. That may make Peter's new Skater vee the best of a bad lot in that, with five steps, the whole bottom can slide (drift) a bit through a turn....but, I still wouldn't want to bet my life waiting for some errant surface to catch and trip.

T2x

Last edited by T2x; 04-25-2003 at 10:51 AM.
T2x is offline  
Reply With Quote
Old 04-25-2003, 10:51 AM
  #37
T2x
Allergic to Nonsense
Platinum Member
 
T2x's Avatar
 
Join Date: Aug 2001
Location: Granite Quarry, NC
My Boats: 1966 !8' Switzer Wing "Miss Diablo" 1968 Switzer Wing "Dust'n the Wind 2",, 1960 Powercat 15C , 1977 17' Molinari w/Evinrude CCC
Posts: 5,004
Default

Quote:
Originally posted by audacity


the bottom line (pun intended)...get to know your boat and yourself...don't go out there and learn with passengers. if ya want to know more???...i'm sure there are some racers in your area that always love seat time and are more than happy to pass along knowledge. i know some race teams sell seat time in a race boat, as we do...the information is out there...you just have to ask!

people seem to want a absolute answer...like for turning X boat where do i set tabs, drive and throttles in a turn...i think we create more problems trying to answer ...again, EVERY boat will have a different feel! so get to know your boat and set up...know WHAT and WHY it's doing things...this will allow you to change with it dynamically, as we know the environment it is in does!
BE SAFE
Joey:....

I concur with all of the above except that there are a surprisingly large number of racers who don't have a clue.........and have a huge "show off" factor.

be selective of whom you trust in all things......and always Be Safe.

T2x

Last edited by T2x; 04-25-2003 at 11:31 AM.
T2x is offline  
Reply With Quote
Old 04-25-2003, 10:59 AM
  #38
Registered
 
Join Date: Jun 2001
Location: Michigan
My Boats: It's how well you go fast
Posts: 3,345
Default

the end result maybe...but they are different...cg plays a part and the moment can work for or against you...also surface adhesion and laminar flow (in differnt areas of the hull) work themselves into he equation as well. the later is what we are working on now.
audacity is offline  
Reply With Quote
Old 04-25-2003, 11:03 AM
  #39
Registered
 
Join Date: Jun 2001
Location: Michigan
My Boats: It's how well you go fast
Posts: 3,345
Default

"suprisingly large number of racers who don't have a clue.........and have a huge "show off" factor. "

i agree...but if your savvy enough to seek out good information and repeatable data...you maybe keen enough to sift through the bull **** too.
audacity is offline  
Reply With Quote
Old 01-11-2005, 02:12 AM
  #40
Charter Member # 430
Charter Member
 
kcgbjc's Avatar
 
Join Date: Nov 2000
Location: Orange County, So Cal!
My Boats: None, sucks!
Posts: 288
Default Re: Tips for driving stepped bottom boats

Thank God for these boards! I have a new Eliminator with steps and never really thought about it. I never turn hard tho. When I turn, I ALWAYS settle the boat slowing down get into the turn then throttle out. Guess I was doing right all along. I will be a lot more careful now.

THANK YOU ALL!
__________________
Chris Johnson
Armed Forces Racing
www.armedforcesracing.com
kcgbjc is offline  
Reply With Quote
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
kgshooty
General Boating Discussion
42
05-27-2008 02:08 PM
gotime34
General Boating Discussion
40
11-11-2005 03:58 PM
Apple a day
General Boating Discussion
16
02-01-2005 10:08 PM
BLee
General Boating Discussion
5
06-28-2004 06:41 PM
Cattitude
Pantera
3
06-07-2004 08:21 PM



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 03:45 PM.


Copyright 2011 OffShoreOnly. All rights reserved.