Three Point Hydroplane Questions

Hello, new to the forum and excited to learn from the experts!!! I am involved with remote controlled boats and currently building a three point hydro (outrigger?) from plans. It is about 42" long with two sponsons that do not have steps. I have not run the hull yet, but figure adding a step or two would change the boats performance. Other rc hulls I've seen have a step. So instead of copying someone else's work, I would like to change the existing plans to make the hull a fast and stable heat racer.

Can anyone recommend where to start reading on step design? Or know of any information about how to design sponsons? Pictures/diagrams would help!

This is the best picture I have so far:




Aaron

 

Nice looking boat you have there.
I would recommend going to rcuniverse (go to forums, boats, gas boats) and checking their forums. They'll more than likely be able to answer any of the questions you might encounter. I've surfed that website for hours absorbing as much info as I could when I was thinking about doing a 50" Deep V gasser.

I designed and built an outrigger like yours in high school shop class. Still haven't put a motor or any of the running hardware in it though. That was like 8 years ago..Some day...

 

Thanks for the reply...I thought there would be more info here and also on google about the design of sponsons. Can't find much. Guess this will be a trial and error type of build.

 

Did you check www.rcuniverse.com?
All of the information you'll need is there.

 

Steps

What are steps used for ?
how do they work ?
why have them ??

Its all about getting the boat up and out of the water to reduce wetted area . tunnel hulls are the closest thing you can get to the ultimate in Boat design . its got good hydrodynamics and is fast off the line . digs in and goes round 90degree corners like they are on rails yet on the straight away barely touchs the water and appear to fly with the hulls touching only the tops of the waves sometimes , 3 pointers are the fore runner of the tunnel i like to think .
The hull and sponsons you have the air and aerodynamics have little effect
so to get your hull up off the water you want to use steps ,the placement of steps depends on how the boat planes without them .
I used to make small tunnel boats and would draw up the boats full size on a wall so could stand back and eye ball the drawing .
The planning attatude we worked on was between 2.5 to 4 degrees to the surface of the water so the drawing was set at 3 degrees and all our steps and strakes and chines etc etc could be set to work at that angle .A true level line that stood out and was easy to see from a distance was drawn on each boat so when it was in the water and running at differant speeds we could use a video and see the horizen water level and the running attatude of the boat and radio the trim to the driver so he was able to set the trim angle gauge in the cockpit .
Same thing you could do ,set your hull at 3degress and draw level line do everything at a good eyeball height then study where the steps need to be located , what angle they need to be and play with them from there .
remember they are to lift the hull so a slight turndown of the trailing edge 2 or 3 mm could do wonders and flick the water down and create even more lift . keep all corners as sharp smooth and clean as possible so the water sheds away from and dosent cling to any surface even the sides of things . Surface effect with you design will only play a small part . but fill the space between your sponsons and you get even more air lift
Shape and flat sides !! do you see planes that look like flying boxes ?? time to study aerodymanics as well .
How does a wing create lift ??
How many aerofoil sections do you know of ??
what are the best??
Have you seem any and looked at them closely ? How fats will you boat travel at ??
If you looking at foils match the speed to the foil and the foil to the speed !!
See ya

The sponsons and the main body of the boat need to be designed and built round the wing shapes all sides !!!
sponsons need to be wing shapes . The steps you wanting to know about really are a small part of your problems for go fasts it need to fly !!!!!Get ot off the water as in not touching then your steps are meaning less and nothing!!! it needs to run in surface effect if you dont know what that is look it up ,its really interesting !!!. every plane ,ever where, uses it everytime they fly !!
and make it light !!!!

 

Hers the underneath of one similar to yours.

Donald Cambel is driving it and he died a few seconds after this was taken.

60 year old technology

 

Outriggers

http://www.youtube.com/watch?v=hEPTBRlwSCA

Dan Ellison top fuel drag boat

 

Full size boat engineering doesn't scale 1:1 to rc models.

 

Dan Ellison's drag boats started out as RC models.

 

tunnels, great information...thanks for posting. Do you have a picture showing an example of planning attitude? Do you think every side of the sponson should have be round/curved? What is affected by the degree angle of the bottom of the sponsons? Does the shape of the tub carrying the engine make a difference? I have seen some 3/4 points without the front of it raised up, instead it's just a long rectangle.

 

The only thing that matters on the sponsons is whether they're flat on the bottom or have deadrise.

 

Everything makes a differance go look at some airplanes and thngs that go fast go have a look at the new range pf cars everything has smooth flowing shapes not boxy and blunt and square the centre motor pod is a good example sharp corners and about a aerodynamic as a brick the sponsons the same and the bottom of the sponsons need deadrise not flat !! angle gives a smoother ride everytime the boat hits a wave and jumps it takes energy its energy from the motor so the smoother it rides and not wanting to get airbourne that energy is used to drive the boat forward . and if there little wind resistance the its easy to move through the air
Travel down the ride and put your arm out the window have you hand vertical or flat to the air its hard to push against turn your hand horizontal and oops the pressure is only a fraction of what it was . and if you slowly tilt your hand it wants to lift .turn the other way it wants to go down ,at speed every shape will create lift if it is truned the right way . with a limited amount of power you are looking at making the boat move a free as possible . even the tubes that hold the sponsons need to be foiled shape not round find aero foils and understand them . look at slow speed aircraft and high speed .see the differance in the shape . no use making foils from a 1000 mph wing when the boat is doing 100mph the wing we used was the old
RAF 32 it was perfect for our small tunnels worked well at even 50 mph and had good lift and quite stable . draw a foil and build you boat around the shape without changing it to much !! for sides look at wing tips stidy the airflow across and wing and off the end and see whats happening . modeling aircraft has a lot of information that applies

 

The sponson have 3 degrees. How does that sound?

 

You are making me want to redesign the center engine carrier. Can you provide any pictures or other information of planing attitude?

When designing the outrigger, you recommend starting with a 2D side shot to determine the planing attitude and where wind will "catch"?

 

3 degrees sounds fine.