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Lesson TWO….Walking and Nose High Condition

Walking
Chine roll is a another term for the same thing.
Most V hulls get this characteristic of rocking side to side as they get up to speed on the pad. It is more of a problem in calm water. If you run an older style V with no pad then this problem is always there.
Here is what people will tell you and their suggestion[s] may or may not work.
[1] you drive thru it. The boat settles down after you get going faster.
[2] your moving your hands too much. Your over steering the boat.
[3] your boat has a hook in the bottom.
[4] your boat needs a hook in the bottom.
[5] your motor is too high
[6] your running too much trim
[7] you need solid motor mounts
[8] you need cable and pulley steering
[9] you need to run a cleaver prop
I am sure there are others.

IS IT THE DRIVER’S SKILL!
Ever seen a T race boat racer who drives the boat so smooth and in control that it looks easy? It’s a skill and for some it is a gift. Racers call it “feeling the boat thru your asx”. Those drivers run on the edge and in control. They can run set ups that others can’t even drive. Many think it is just because their young, bold and reckless. NOT! You see these racers in later years and they still have it. These are the ones I referred to in a previous post about knowing your limitations. Their just better…period.

Now back to the Walking problem with your T boat.
First to find out if it is you or the boat. TEST drive another T boat that doesn’t have the problem. If you walk it. Then you’re the problem and you need to change your driving style.
The 3 solutions I have that work best for me are:
[1] forget about power trim. Set up the boat 1 pin hole [positive] from neutral and firmly strap the motor to the transom, You want no movement in the motor. Make all your balance adjustments by moving the battery and gas tank positions.
[2] try a smaller diameter prop. It you run 12 ½ x 21, try 11 ¾ to 12 x 23.
[3] run 2 inches of setback.. Not 4 or 5 inches

PRACTISE AND SEAT TIME!

NOSE HIGH
[1] too much stern weight.
[2] too much setback
[3] too much speed…At 65 mph plus with a chop these boats especially the Deltas have trouble settling in the corners. That is one reason why the original Danny Critchfield boats were a little nose heavy. That enabled the boat to enter and turn better in the corners. At 65 plus you have to be like The Gun , you drive the boat thru the corner and use a wider curve rather than cut the corner and muscle the boat. I ran a small sand bag in the nose of my FG Checkmate to give it extra nose weight after I blew it over backwards 2 days in a row. Remember any weight you add to the nose effects the boat 3 times greater than in the stern.

good video lesson, but I like the comment about the boat being built by a cabinet maker,my pad was built by a boomerang carver,but I'll fix that over the winter!

Lesson #3.. Gear cases, Gear ratios and Prop selection

Gear cases
Currently we have the following gear cases
Yamaha 1.71 or 1.84
OMC 1.76 in 3 styles, straight skeg, angle skeg and SST 60
OMC 2.33 large case.
When you look at the race results there is an advantage to running the OMC nitro style smaller gear case over the larger case. The experienced racers like the angle skeg the best.

Gear ratios
A power head turning 6500 rpm at the crank will have the prop turning at 3693 rpm with a 1.76 gear case.
The same 6500 rpm at the crank will turn the prop 2790 rpm with a 2.33 gear case.

So why is this important?
It is not about pitch because you just increase the pitch on the 2.33 case so the total distance travelled in one revolution is the same.
It’s about drag and load on the motor….The size of the case you are pushing thru the water, the weight you are pushing and the diameter of the prop your turning.
You need diameter to push WEIGHT.
You need pitch to go farther on each revolution to go faster.
That is the basic principle on a stock hydro. They run a very small diameter prop and close to a 1 to 1 gear ratio. The boat works hard to get up on plane because of the weight and small diameter prop. Once it gains speed the design of the boat reduces the weight and it doesn’t need a big diameter prop.

A Teeter Totter.
A prop is like a teeter totter. If you change the length [diameter] and the weight position from the centre [pitch] it changes how it works. The power head is the other side of the teeter totter.
So the more diameter the more load on the power head.
The more pitch [weight] the more load on the power head.
But it is less load on the power head if the same amount weight is close to the middle.
The farther out the weight the more load on the power head.

Variable pitch props
The reason is stated above.
You need diameter to move or accelerate the boat. You need pitch to get the speed.
You can’t have the same pitch of the outside as you do on the inside of the prop. So you have less pitch on the outside and more pitch in toward the centre.

Texas Cut
Jeff Titus has had great success with this style. He is in Florida. He didn’t have the original idea. But, he has developed it.
The blade is like a steak knife. It is much thinner at the outside compared to the inside and middle of the prop.
The reduction of blade surface in the outter part of the blade is the same as reducing the pitch. It reduces the load.

The Rooster Tail
At speed the rooster tail should look like a fire hose. Very low.
It does go high on acceleration and positive trim. But it should drop once it hooks up.

Calm verse rough water
Diameter slows you down in calm water. The smaller diameter prop has no problem getting water on the blades and working efficiently. .
Chop or soup that we get in T after lap 2 is different.
If you are top 2 or top 3 in the heat the smaller prop will not hurt you.
In the pack it helps to have more diameter. You get more thrust.
Remember you can run more diameter if you reduce the pitch or cup on the outside. Some racers will have the out part of the blade almost flat and even bent back slightly.

Testing versus racing
Can be totally different. Your best test prop may not be your best race prop.
ALWAYS RACE TEST! Don’t make a prop decision on one race and don’t alter a prop after one race.

Please remember that this school is for T boat racers with 75 to 80 hp. You can't always think the same if your running a big V6. There is a big difference in power.

[quote="Hounddog"]Lesson TWO….Walking and Nose High Condition


IS IT THE DRIVER’S SKILL!
Ever seen a T race boat racer who drives the boat so smooth and in control that it looks easy? It’s a skill and for some it is a gift. Racers call it “feeling the boat thru your asx”. Those drivers run on the edge and in control. They can run set ups that others can’t even drive. Many think it is just because their young, bold and reckless. NOT! You see these racers in later years and they still have it. These are the ones I referred to in a previous post about knowing your limitations. Their just better…period.


This comment just reminded me of watching Owen Boris in the 90's... he was no spring chicken but man could he drive a Mod VP boat!

Variable pitch props:
So how does that work, I don't understand I'm afraid. You want more pitch towards the center of the prop, and less towards the outer 'point' of the blade? How does that work depending on how much prop is in the water at different times during a race? How about the pitch at the leading edge and trailing edge of the blade?

Some notes about what I learned about my setup this year...
Boat: 13' Allison
Engine: 56ci OMC with nitro case, straight skeg
Rigging: Cable steering
Top speed: 68mph with a 12x23 OMC cleaver (65-66 on the course)

Chine Walk: The boat took a bit of getting used to, but I found I was over correcting chine walk to begin with. The string steering is so precise, you don't need major corrections. Also, remember chine walk correction is all about turning left. Just imagine that the boat falls off the pad to the right, so you are bringing it back by turning left. as soon as you feel it falling right, make one correction to the left. Once I realized this, the boat was soooo easy to drive!

Steering: I made a few changes to the steering over the season including smoother pulleys and nylon line. I wore the nylon coating off once. I found the line was not running straight through the pulley. I managed to fix it by adjusting the angle of the pulleys. A smooth steering setup will really help in controlling the boat. My steering line is hidden. I have found other guys external setups makes for less turns and smoother operation again.

Spinout: Many of us have learned a thing or two about spinout this year! For me, I started by running an 11.25x23 prop. By changing to a 12x23 I could hold much better in the corners. I understand a larger swept skeg would help too. Maybe then I could have run a smaller diameter prop?

Trim: I don't have it. My boat seemed to be pretty well balanced and I could get the boat to settle in the corners fairly well too. I would have liked to have it in the rough to bump it down a bit in order to keep the pedal down on the straights. Paul Kryskow said trim would help to accelerate better as well, lifting the boat until it gets air under it.

Props: I had a chance to try alot of props thanks to LC!! A 12" diameter prop seemed to be magic for my setup. I tried a 12.5", but it would torque the boat around quite a bit in the corners. Although a blowout ring on the same prop fixed this problem altogether, I lost a mph or so on top end. I also found prop choice to help settle the boat down. A prop with a lot of rake (19 degrees) will lift the boat better, but with no trim this can be a detriment in the corners and flighty in the straights! Jeremy(Tunnelv) let me borrow his low rake (12-14 degrees) 12x23. This was both my safest and one of my fastest props! This prop also accelerated really well! This is due to the low rake. A low rake prop is more efficient! LC let me run a texas cut 12x23 that I loved! This prop was a great combo of acceleration, handling and speed. I would have loved to try a 12x21. I was only reving 6300. A 21p prop would accelerate better bringing my revs to 6700 or so.

Allison Hull Design: Every boat is different. The Allison has a narrow (6 inch) pad. This helps it settle down and run smooth in the corners, but it takes longer to get on the pad in the straights.

I hope this info helps somebody getting into the sport! This class offers so much fun and support from a great bunch of guys! I'm really looking forward to T750 in 2013!

Dave.

Great summary Dave!

Lots of great info.

Jake think of the pitch as adding weight. The more weight [pitch]the more load on the power head. When you increase the pitch it adds load on the power head and the rpm slows down. The position of the weight [pitch[ on the blade makes a difference in the load on the power head. A prop pulls water from the inside and the water passes along the blade to the end. On most good T props using a pitch gauge you will find that the pitch varies from the centre out. Usually there is more in the centre, example 23-22-20. Cupping also acts like pitch. A good cup adds an inch of pitch. Props are also different from the front [leading] to the back. On a cleaver prop the thickness of the wedge in the prop also makes a difference. The thicker the wedge the more stern lift on the boat. The longer the water stays on the blade the more thrust. I big rostertail means the water is coming off the blade too soon.

LC was that a Titus prop or the OMC V4 drag prop you purchased from me?