Plum_Crazy

I've been reading lots of threads on drive toe on various boat forums and all it has done is confuse me. When I think of toe-in, I think this / \. The front of the drives are closer than the drive shafts. However, some people refer to this as toe-out, which only adds to the confusion.

My drives were setup with 1/8" toe-in / \. However, my props are spinning out. Should the drives be set to toe-out for optimal performance when the props are spinning out or is this correct? I've read opposite recommendations for this and some that even say to make the drives straight. What's the right answer?

GO4BROKE

iTrader: (1)

The idea is to wind up with the drives straight while under load. By my thinking the rear of the drives should be 1/8" further apart than the front. /\

Plum_Crazy

So, if the props are spinning out, aren't they trying to push the drive noses together? Therefore, the toe should be out \ / and have the shafts closer together than the noses. Think of it like ice skating. If you push off the outside edge, you travel to the middle.

GO4BROKE

iTrader: (1)

This won't copy and paste, but check out this link:
http://books.google.com/books?id=3HX...esult&resnum=7

Plum_Crazy

Thanks, but I still don't understand the relationship between prop rotation and toe. Maybe there is no relationship.

marylandmark

Drives/props are most efficient when lined up straight: | |

Go down the road with your hand out the window- holding it straight has less resistance than at an angle.

Props spinning in try to come together and push the nose cones away from each other

Props spinning out push away from each other and pull the nose comes together

Props spinning in: toe in or / \ so when the props try to come together they go | |

Props spinning out: toe out or \ / so when the props push away from each other they go | |

Performance steering and/or good tie bars are stronger than prop torque so you set the toe neutral because the drives stay | | all the time.

That is just toe and prop rotation- how different hulls act/react is a whole 'nother can of worms.

Then read this: http://continuouswave.com/whaler/ref...eMounting.html

Water doesn't flow directly off your hull in to the drives path so you have to play with the water flowing to fill the void your hull causes as it passes as well.

Plum_Crazy

Thanks, that's exactly what I was looking for. I was confused as to why my Sonic came set up with toe-in / \ when the props are spinning out. That's probably slowing me down a bit. I think I'll experiment with straight and toe-out 1/8".

marylandmark

You are right. Stand with your feet together.

Toes = nose cones
Heels = prop shaft

Toes in (pigeon toed) is - you got it; toed in!

Now read this to get you real confused: Jim Rohr

"Now if the engines were "toed in" (front of engines closer than rear of engines) it would be normal for a deep-V hull, but these engines were "toed out" meaning the engines were both driving away from center line if looking forward from transom to bow."

I had the same problem the guy in the article did. OSO Steve solved this issue for me after I spent $10Kish in prop testing.

I had Mark Anthony/Mercury Racing rep for 30ish years set mine up. He toed them out a tad to compensate for prop torque since my steering is not super solid. I have outboards so I am dealing with the motor, motor torque, drives and prop torque.

The reason you would toe out a tad is because when a conventional moderate powered V goes through the water- the hull passes, then water fills the void where the hull just was and then the drives pass. The water will rush in to fill that void at an angle since it passes around your hull at an angle.

You are trying to get it so your drives are lined up with the water rushing in to cause the least amount of resistance (think hand out window thing again) but pointing as straight as they can so the most thrust is directed in that way.

Your drives pointing || obviously give you 100% forward thrust, however you may find that by reducing your drag/resistance even if your drives are toed out a tad (not 100% forward thrust) you may be faster than having them ||.

Brownie did the math for me once- some thing like every inch of your drive at 60MPH is over a ton of pressure (I could be WAY off on that but I was amazed at how much it was).

Ah screw it- get some chicks and beer and go boating. Get it close and leave it alone- few degrees in air temp/humidity makes a bigger performance difference than this one-one-tenth of an inch crap!

GO4BROKE

iTrader: (1)

I agree with Marylandmark. I doubt you will be able to measure a speed difference 1/8 in or out or neutral. Too small a difference and too many other variables changing the numbers. I imagine it would be important once over 100mph, but not so much below that.
Toe in, toe out, doesn't matter as long as her legs are over you shoulders!

Plum_Crazy

Hey, every little 10th of a MPH helps. I'm trying to get this boat to run at least 75 through mufflers. I just set it up to 1/16" of toe-out today. I'm hoping to take Wednesday off to go prop testing, if my correct RH prop ever shows up.