Best set-up for best cornering speed

[Mike Hughes]

If your out in front no problem. I love that they flop over with a hard left turn. I have save a few boats like that. Stopped in 10 feet.

 

[Marty Davis]

I wrote about this as one of my most recent Technical Notes.

It is available here: http://www.1nitrorc.com/turning_dynamics.html

I think that this might be helpful.....

 

[Charles Perdue]

I wrote about this as one of my most recent Technical Notes.

It is available here: http://www.1nitrorc.com/turning_dynamics.html

I think that this might be helpful.....

Marty wrote a good article. Read it until you have memorized it.

Here are a few things that I will add to Marty's article. The boat hull, sponson booms & sponsons themselves must be absolutely rigid. The hull itself must be very rigid in the torsional plane, the hull twisting along its axis, (hard to do) as well as the longitudal plane, along the length of the hull, (easy to do). The BOSS boat that Marty is referring to of Jack and Steve O'Donnells had triangulated sides (tapered from the top to the bottom) to make it extremely rigid. This can be done without adding any additional weight, it just uses the triangle shape to make it work. This may be why some of the others had problems duplicating its performance. Also the sponson brackets were VERY rigid, especially the right rear bracket that carries a larger part of the load from the turn fin.

The lifting of the left sponson when turning left was corrected by simply extending the sponsons out a little farther and correcting the angle of the turn fin.

Something that must be understood before you can consistently set up boats to allow them to turn like this is actually just how much of a load there is on the turn fin. I am attaching a simple calculator here that will help you in regards to this.

I entered some average numbers into the calculator. First thing that you must do is change the values of the entry blanks on the calculator to something that is meaningful to us. Then I used a 30 foot radius for the turn with the boat traveling at 70 mph with a boat weight of 4.5 pounds. The resulting numbers that came out of this were 10.92 G's of force (if there were a human on board, they would be blacked out) with a load on the turn fin of 49.14 pounds. These are just some hypothetical numbers I entered into the calculator tool to show the forces that we are dealing with. You must use your own numbers for an accurate load measurement for your boat.

Now lay your hydro on its side with the right sponson on the edge of a table and hang a weight of 50 pounds pulling down on the turn fin and you will see just how much deflection there is on the fin in this turn. For the boat to turn very good, this should be as close to zero as you can get it, within reason.

There is a lot more to this challenge than just this, such as the amount of wetted sponson surface. rudder type, rudder placement and other things.

The ideal handling of a hydro in the turns is when you just move the rudder enough for it to begin its arc and hold the rudder at this position as the boat sweeps the turn without any additional rudder throw having to be added. When the boat does this, then you are getting very close. The closer that you get to this setup, the more critical that everything else becomes. But it can be done. It has been done before many times and has won many races.

This is when it starts to become fun, when you enter the corner behind someone and come out of the turn ahead of them.

Charles

calctool.css

 

[Charles Perdue]

I wrote about this as one of my most recent Technical Notes.

It is available here: http://www.1nitrorc.com/turning_dynamics.html

I think that this might be helpful.....

Here are a few things that I will add to Marty's article. The boat hull, sponson booms & sponsons themselves must be absolutely rigid. The hull itself must be very rigid in the torsional plane, the hull twisting along its axis, (hard to do) as well as the longitudal plane, along the length of the hull, (easy to do). The BOSS boat that Marty is referring to of Jack and Steve O'Donnells had triangulated sides (tapered from the top to the bottom) to make it extremely rigid. This may be why some of the others had problems duplicating its performance. Also the sponson brackets were VERY rigid, especially the right rear bracket that carries a larger part of the load from the turn fin.

The lifting of the left sponson when turning left was corrected by simply extending the sponsons out a little farther and correcting the angle of the turn fin.

Something that must be understood before you can consistently set up boats to allow them to turn like this is actually just how much of a load there is on the turn fin. I am attaching a simple calculator here that will help you in regards to this.

I entered just some average numbers into the calculator. First change the values of the entry blanks. Then I used a 30 foot radius for the turn with the boat traveling at 70 mph with a boat weight of 4.5 pounds. The resulting numbers that came out of this were 10.92 G's of force (if there were a human on board, they would be blacked out) with a load on the turn fin of 49.14 pounds.

Now lay your hydro on its side with the right sponson on the edge of a table and hang a weight of 50 pounds pulling down on the turn fin and you will see just how much deflection there is on the fin in this turn. For the boat to turn very good, this should be as close to zero as you can get it, within reason.

There is a lot more to this challenge than just this, such as the amount of wetted sponson surface. rudder type, rudder placement and other things.

The ideal handling of a hydro in the turns is when you just move the rudder enough to begin it to start its arc and hold the rudder at this position as the boat sweeps the turn without any additional rudder throw having to be added. Then you are getting very close. The closer that you get to this the more critical that everything else becomes. But it can be done. It has been done before many times and has won many races.

This is when it starts to become fun.

Charles

 

[Charles Perdue]

I wrote about this as one of my most recent Technical Notes.

It is available here: http://www.1nitrorc.com/turning_dynamics.html

I think that this might be helpful.....

Here are a few things that I will add to Marty's article. The boat hull, sponson booms & sponsons themselves must be absolutely rigid. The hull itself must be very rigid in the torsional plane, the hull twisting along its axis, (hard to do) as well as the longitudal plane, along the length of the hull, (easy to do). The BOSS boat that Marty is referring to of Jack and Steve O'Donnells had triangulated sides (tapered from the top to the bottom) to make it extremely rigid. This may be why some of the others had problems duplicating its performance. Also the sponson brackets were VERY rigid, especially the right rear bracket that carries a larger part of the load from the turn fin.

The lifting of the left sponson when turning left was corrected by simply extending the sponsons out a little farther and correcting the angle of the turn fin.

Something that must be understood before you can consistently set up boats to allow them to turn like this is actually just how much of a load there is on the turn fin. I am attaching a simple calculator here that will help you in regards to this.

I entered just some average numbers into the calculator. First change the values of the entry blanks. Then I used a 30 foot radius for the turn with the boat traveling at 70 mph with a boat weight of 4.5 pounds. The resulting numbers that came out of this were 10.92 G's of force (if there were a human on board, they would be blacked out) with a load on the turn fin of 49.14 pounds.

Now lay your hydro on its side with the right sponson on the edge of a table and hang a weight of 50 pounds pulling down on the turn fin and you will see just how much deflection there is on the fin in this turn. For the boat to turn very good, this should be as close to zero as you can get it, within reason.

There is a lot more to this challenge than just this, such as the amount of wetted sponson surface. rudder type, rudder placement and other things.

The ideal handling of a hydro in the turns is when you just move the rudder enough to begin it to start its arc and hold the rudder at this position as the boat sweeps the turn without any additional rudder throw having to be added. Then you are getting very close. The closer that you get to this the more critical that everything else becomes. But it can be done. It has been done before many times and has won many races.

This is when it starts to become fun.

Charles

For some reason, I cannot attach the calculating tool.

Here is the address:www. calctool.org then go to centrifugal force

 

[Marty Davis]

One of the most important items in the Tech Note is that the boat MUST pivot around the center of pressure of the turn fin. If it is to far forward or to far rearward the boat will not easily pivot on the fin. You will know this if your rudder throw is more than the circumference of the turn. It takes very little throw if it is correct. It took us a while to figure this out. We thought that we had something wrong initially until we reduced the throw of the rudder.

 

[Roger Hooks Jr.]

Thank you Marty and Charles for that deep insight. Certainly what I was looking for. Marty I noticed that in your mention of rudders you didn't mention which side of the boat was better. I've noticed like in Gas sport boats for example the Insane rudder set-up is different from the Backlash for example but I've seen no Gas Sport boat turn better than a Backlash. Any thoughts on rudder position?

 

[dwilfong]

The rudder has a lot to do with it.

Andy passed on some words of wisdom to me about the rudder.

A wide rudder front to back that is the same thickness at the back as a shorter rudder will produce less drag.

The angle of attack in the wedge is what causes the drag not how wide front to back it is.

With a wider rudder you do not have to move it as much to gain the same force to turn.

If the rudder turns more than the arch you make in the corner you are scrubbing off speed with drag.

A narrow rudder will have to turn more than the arch the boat is making.

A wide rudder front to back will apply more force to the hull and not over rotate to compensate.

Steve wood made me a 1.5 wide rudder for my SGX and it made a BIG difference in the corner speed.

I have also found that a thin , wide front to back turn fin that flexes has helped a lot also. I made one out of .050 Titanium. It flexes a lot but it dose not lose its shape after many runs. I think the reaction of the fin is different than SS fin. Kinda like a different set of shocks on a car react to the spring rates different.

The guys at the races are baffled by that thin flexing fin. It just blows there mind when thy see how it runs with that wet noodle on the boat.....LOL

Just figured I would share what I have found from testing and racing.

Mark how did thy like that one I sent you?

 

[Charles Perdue]

The rudder has a lot to do with it.

Andy passed on some words of wisdom to me about the rudder.

A wide rudder front to back that is the same thickness at the back as a shorter rudder will produce less drag.

The angle of attack in the wedge is what causes the drag not how wide front to back it is.

With a wider rudder you do not have to move it as much to gain the same force to turn.

If the rudder turns more than the arch you make in the corner you are scrubbing off speed with drag.

A narrow rudder will have to turn more than the arch the boat is making.

A wide rudder front to back will apply more force to the hull and not over rotate to compensate.

Steve wood made me a 1.5 wide rudder for my SGX and it made a BIG difference in the corner speed.

I have also found that a thin , wide front to back turn fin that flexes has helped a lot also. I made one out of .050 Titanium. It flexes a lot but it dose not lose its shape after many runs. I think the reaction of the fin is different than SS fin. Kinda like a different set of shocks on a car react to the spring rates different.

The guys at the races are baffled by that thin flexing fin. It just blows there mind when thy see how it runs with that wet noodle on the boat.....LOL

Just figured I would share what I have found from testing and racing.

Mark how did thy like that one I sent you?

David, just another one of your attempts to give out misinformation to the boaters and destroy a good topic. Misinformation is much worse than no information.

Do you not realize that ******** is no match for scientific principles, physics and common sense.

What is it with you anyway? Is it your ego, drugs or just ignorance of the facts????

Charles

 

[julianconde]

Roger,

The teardrop design is a really good one.

I am with Rudy a larger turnfin will get you through the corner

faster with a better overall lap time. With the new ABC propellers

a lot of boats will need bigger turnfins and run them deeper also

to hold the faster boat in the corners. Testing is the only way to

prove if you are heading in the right direction, the stopwatch does

not lie.

Enjoy Testing New Designs,

Mark Sholund

Bingo we have a winner. Everything stated is correct. I have tested a lot with my twin 45 and 101RS twins this year. bigger and deeper turn fin has made by twins turn on rails. Also I use a wider rudder on my boats ad david stated as well helps going in the turns and with the bigger turn fin it's a perfect combo. Works for me but might not work for others. I have attached some pictures.

Have fun testing.

Julian

 

[John Finch]

You guys are bringing back some good old memories when Kentley Porter and I ran 8.5 second laps to break the 60 and f records many years ago. The principals Charles and Marty are talking about just brought back those trying times when we ripped turn fins out of the sponsons and only used a quarter inch of rudder throw to whip the corners. Wow those were some sights to see. Kentleys Orlic mod f class engine pushed the boat to 103 mph at the end of the front SAW and was clocked at 98 coming out of the turn on buoy six. People would back up off the bank when the boat came out of buoy six. Those perfect runs are hard to get with glass water and good crisp air but when they do. WOW!!!!!

 

[dave roach]

If you have to turn the rudder more then 10 deg.to the right and you turn fin isn't doing the job.Just like Marty and Charles stated.When everything is right you can her the engine unload in the corners.

 

[Roger Hooks Jr.]

The rudder has a lot to do with it.

Andy passed on some words of wisdom to me about the rudder.

A wide rudder front to back that is the same thickness at the back as a shorter rudder will produce less drag.

The angle of attack in the wedge is what causes the drag not how wide front to back it is.

With a wider rudder you do not have to move it as much to gain the same force to turn.

If the rudder turns more than the arch you make in the corner you are scrubbing off speed with drag.

A narrow rudder will have to turn more than the arch the boat is making.

A wide rudder front to back will apply more force to the hull and not over rotate to compensate.

Steve wood made me a 1.5 wide rudder for my SGX and it made a BIG difference in the corner speed.

I have also found that a thin , wide front to back turn fin that flexes has helped a lot also. I made one out of .050 Titanium. It flexes a lot but it dose not lose its shape after many runs. I think the reaction of the fin is different than SS fin. Kinda like a different set of shocks on a car react to the spring rates different.

The guys at the races are baffled by that thin flexing fin. It just blows there mind when thy see how it runs with that wet noodle on the boat.....LOL

Just figured I would share what I have found from testing and racing.

Mark how did thy like that one I sent you?

David, just another one of your attempts to give out misinformation to the boaters and destroy a good topic. Misinformation is much worse than no information.

Do you not realize that ******* is no match for scientific principles, physics and common sense.

What is it with you anyway? Is it your ego, drugs or just ignorance of the facts????

Charles

I see it as another option. I think we've all managed to find a different way to go fast. May have been flawed in one way or another but managed to use whatever we had within us to win a race or set a record of some sort. My Sport 40 II Ira Cotton boat comes to mind for that held the NAMBA record for several years. Like I mentioned before if I set-up for the corner just right, with just the right about of throttle to set the boat I could zip right around that turn but touch it left and it could be a catastrophe, turn too much, hit the corner with too much power or don't turn enough and the boat would turn sloppy and inconsistently but hit everything right and you'd think it was a perfect running boat. Perhaps there are more consistent approaches but it's good to know what works and why as well as where the drawbacks might be with each philosophy. So I'm interested in why a "wet noodle" might work too if it indeed does.

 

[John Finch]

I would like to know that one myself Roger. One thing I like to keep in mind with respect to rudders is that the prop wants to carry the transom to the left so while going down the SAW we are just using the rudder to hold the boat from turning right. When we get to the corner we are turning the rudder just enough to let the transom track left like it naturally wants to go so we are LETTING the boat turn to the right, not MAKING it turn right.

John

 

[dave roach]

Not a lot of love here.Now you two KISS and make up.LOL

 

[DON MAHER]

Real class right there David, you do know the whole world can see what as ass you just made of your self!

 

[Don Ferrette]

Some of you better calm down REAL QUICK as any more profanity laden outbursts will not be tolerated. I have better things to do than come on here to a bunch of p/ms complaining about said behavior. And to those this applies to don't bother sending me p/ms "explaining" your side, don't want to hear it.

 

[julianconde]

Wow

 

[dwilfong]

Sorry Don.................lost my head.............

That's what happens when you play with your wet noodle to much.

 

[Charles Perdue]

Sorry Don.................lost my head.............

That's what happens when you play with your wet noodle to much.

To Don and my fellow boaters,

It is very aggravating when you make a post that is hopefully useful to the boaters on here and someone tries to contradict you with only opinions, nothing even related to facts. I spent over a year and built several boats to try to find out what did not just work good on making a hydro turn but to make it turn at its best on every lap. This was 39 years ago and very little was known at the time about boat handling. I did a lot of research to try to learn and I try my very best to base my knowledge and understanding on these scientific facts and principles. You cannot rearrange physics to suit your application.

When you make this information available, then someone comes back and makes a post about the subject that has no scientific base whatsoever, it confuses the ones that do not know and are here to learn.

Sometimes it causes our emotions get the best of us.

I am through Mr. Don......