Simon.O.
06-22-2010, 05:00 AM
May be useful for setting up a rigger.
This is info that I have that may be useful for those setting up a rigger. This is based on experience on the water and a LOT of reading.
Qualifiers.
I do not race, never have and probably never will.
All my speeds are gps based. No timing or radar with one exception.
I run on an unusual piece of water that is good for saw type runs. It is a keyhole shape and I stand roughly in the middle so i get one wide sweeping turn and one very tight turn at the bottom end. Even the sweeper is made at about ½ throttle. The bottom turn is minimum planning speed or a slow putter until it is pointing in the right direction for takeoff. I can get just on 100m straight if wanted.
Both of my hulls are a bit different and I have a third on the build now.
Here is the mid size one.
http://forums.offshoreelectrics.com/...ead.php?t=3984
And the larger one
http://forums.offshoreelectrics.com/...ead.php?t=6940
Two Major components of setup.
1. AoA Angle of attack
2. CG Commonly known as centre of balance or more accurately the longitudinal balance point. Also refered to as CofG or CofB
Angle of attack.
For my riggers I have done a lot of experimenting and find that close to 4deg AoA is good for the sponson. More AoA can cause excessive drag or blowover, a fine line here. Less AoA usually has caused drag and ploughing.
I set the tub for 1-2deg Neutral is good but a bit of AoA is a help.
CG.
A common thing I read is that the CG should be where the turn fin is. I see it as the turn fin should be where the CG is. There is a difference as blind adherence to this rule may result in less than optimum performance. For a circuit boat the TF and CG should coincide.
For my straight line boats The tf is very small and is only needed at lower speeds to pull the boat round to line up for another straight wot pass.
My CG has been pushed back to 20%+ of the afterplane length. This is the distance between the rear of the planning surface of the sponson and the prop. As an initial setup 10% is a good guide and then onec AoA angles are set, I have moved the balance point aft. This loads the prop, preventing blowouts and loosens up the sponsons. Naturally this increases the chance of a blowover but that is the risk when speed is concerned.
Measuring.
All of my angles are measured with the hull on a flat surface (tf removed) so that the strut is flat and the angles can be accurately measured. They are checked each week before a run too.
Fwiw my big rigger can safely run 65mph or 105kmh+ my small rigger runs 50mph+ or low 80’s(kmh) The small one was once police radar clocked at 101 kmh (61mph) as a one time nuts setup!
I hope that some of this information is useful to folk who are setting up a rigger.
This is info that I have that may be useful for those setting up a rigger. This is based on experience on the water and a LOT of reading.
Qualifiers.
I do not race, never have and probably never will.
All my speeds are gps based. No timing or radar with one exception.
I run on an unusual piece of water that is good for saw type runs. It is a keyhole shape and I stand roughly in the middle so i get one wide sweeping turn and one very tight turn at the bottom end. Even the sweeper is made at about ½ throttle. The bottom turn is minimum planning speed or a slow putter until it is pointing in the right direction for takeoff. I can get just on 100m straight if wanted.
Both of my hulls are a bit different and I have a third on the build now.
Here is the mid size one.
http://forums.offshoreelectrics.com/...ead.php?t=3984
And the larger one
http://forums.offshoreelectrics.com/...ead.php?t=6940
Two Major components of setup.
1. AoA Angle of attack
2. CG Commonly known as centre of balance or more accurately the longitudinal balance point. Also refered to as CofG or CofB
Angle of attack.
For my riggers I have done a lot of experimenting and find that close to 4deg AoA is good for the sponson. More AoA can cause excessive drag or blowover, a fine line here. Less AoA usually has caused drag and ploughing.
I set the tub for 1-2deg Neutral is good but a bit of AoA is a help.
CG.
A common thing I read is that the CG should be where the turn fin is. I see it as the turn fin should be where the CG is. There is a difference as blind adherence to this rule may result in less than optimum performance. For a circuit boat the TF and CG should coincide.
For my straight line boats The tf is very small and is only needed at lower speeds to pull the boat round to line up for another straight wot pass.
My CG has been pushed back to 20%+ of the afterplane length. This is the distance between the rear of the planning surface of the sponson and the prop. As an initial setup 10% is a good guide and then onec AoA angles are set, I have moved the balance point aft. This loads the prop, preventing blowouts and loosens up the sponsons. Naturally this increases the chance of a blowover but that is the risk when speed is concerned.
Measuring.
All of my angles are measured with the hull on a flat surface (tf removed) so that the strut is flat and the angles can be accurately measured. They are checked each week before a run too.
Fwiw my big rigger can safely run 65mph or 105kmh+ my small rigger runs 50mph+ or low 80’s(kmh) The small one was once police radar clocked at 101 kmh (61mph) as a one time nuts setup!
I hope that some of this information is useful to folk who are setting up a rigger.