SAW rigger design

[Brian Blazer]

What is more important with SAW riggers....Aerodynamics or Weight. Obviously both play an important role, but if you had to choose, what would it be?

The rigger will be gas powered. I can either go really wide (8") at the tub to enclose the pipe and carb, or go with a narrow tub and make shield for the pipe and carb.

Wide tub would be more aerodynamic

Narrow tub would be lighter.

opinions?

thanks, Brian

 

[TomMoorehouse]

i would go narrow. if you make the tub wide it could have other negative effects..... like creating too much lift!

 

[Climate Boatworks]

What is more important with SAW riggers....Aerodynamics or Weight. Obviously both play an important role, but if you had to choose, what would it be?

You can not choose one or the other. It is a combination of all aspects of the design that creates a winning boat.

The fastest boat will be one that runs right on the edge of stability. It needs to create just enough force to hold it on the water, but have just slightly less power than is required to blow it off the water.

You also need to utilize as much thrust as is available. this means getting the prop to work as hard as it can, while the boat has the least amount of resistance through the water and air.

Wider thicker boat with more weight = more lift and also more form drag, but has the benefit of more stability.

A thinner light boat is cleaner through a medium, but more susceptible to flipping when it gets real loose as it overcomes inertia very quickly.

SAW Riggers are a fine balance of power to weight, and lift to drag. The finer the balance, the faster the boat.

 

[AndyBrown]

Just ask the guy that already ran 110+ mph with a gas boat? Why speculate?

When you gat to 110 then you can make improvements from there.

 

[Brian Blazer]

Andy, how about an opinion from the master

 

[Mike Bontoft]

Hi Brian

The boat should be as lite as possible and still retain some structural strength. You are always able to add downforce or kill lift at speed with add ons, The lite boat will allow for an easier launch and will accelerate faster. 8 lbs is a good staring point.

Mike

 

[Brian Blazer]

Hi BrianThe boat should be as lite as possible and still retain some structural strength. You are always able to add downforce or kill lift at speed with add ons, The lite boat will allow for an easier launch and will accelerate faster.  8 lbs is a good staring point.

Mike

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Thanks for the reply Mike, Your records are truely amazing.

 

[AndyBrown]

There you have it!!!!

Mike B. I mapped out your prop. When you see it give me a call and we'll talk about the next step.

 

[jayt]

The fastest boat will be one that runs right on the edge of stability.

I used to think this until I saw the fastest R/C boat in the world run - 143 mph on radar after a 133 mph pass through the traps. The boat was just as stable at 123 as it was at 143....it was definately NOT on the edge of stability at either speed. It appeared to be glued to the water, it might as well have been a train running on rails. It's stability could be upset, but as long as the water was smooth and the driver didn't try to turn left - rock solid on the water.
In electrics a wider tub is where it's at - narrow tubs have just not proven to be nearly as fast. Neither have rounded airplane fuselage-shaped tubs, they just don't have enough directional stability. Perhaps they could be faster with enough additional development, but wide works best for now. The same trend is seen in gas SAW boats; both types have more weight to haul around than some light nitro riggers. Aero drag has to be used to keep a boat at the right attitude and on the water, either as lift or as downforce. Drag by itself is not a bad thing if used appropriately.

 

[Mike Bontoft]

Thanks Andy

I have been bugging Tom at octura for a while now about some 2175. Well they are at the foundry and should be done real soon. I have two being sent to you as soon as they"ve cool down. Thanks Tom, Thanks Andy you guys are the best.

Mike Bontoft

 

[Flyin Rat Sass]

this is a pic of the current record holder .its dart like tail wings(primarily the horizontal one) held it in perfect trim, and i suspect the carbon fiber pieces that front booms are mounted to(and the front boom) reduce some of the aero effect of the tubs nose. but inside is where you see the weight saving tricks ,almost everything was mounted with velcro (batteries , receiver esch, ect.

jayt was correct, the boat was definatly not on the "edge"