Self Righting Put To The Test

[Doby]

Scale Lifeboats have always been a favorite of mine, :biggrin:(I have 2 in my fleet) :biggrin:and its always good to see when someone puts them to the test just like the real ones.....


http://www.youtube.com/watch?v=IeNc3rDT7gM

[westbeach]

Doby,

Show us your lifeboats. That's what I want for a boat, Don't have to worry about flipping over and having a rescue craft standing by.

[Doby]

Cameras packed up right now,,,heading to the airport in a few hours.

[Steven Vaccaro]

In my opinion, every rc boat should be self righting. It makes the day more enjoyable..

[bwells]

That boat is great! Would a piece of 1/2 inch rebar epoxyied in the keel work? What did this guy use?

[NativePaul]

Just a scale model lifeboat with lots of freeboard and tall superstructure with the weight of motor battery esc shaft etc in the bottom should be enough.

[Chuck E Cheese]

wow that is alot cooler than my self righting super-v kit...

[bwells]

It spun over so quickly that I think there is something more than just the equipment inside. I'm leaning to a very heavy keel as well as the freeboard but not sure of the reason for the tall superstructure. I really like it and would like to make one if I was sure of the concept.

[domwilson]

Looks like it's modeled after the coast guard boats...
http://www.youtube.com/watch?v=GDwvy9PzAIc

[bwells]

Yeah, but how exactly does it work? I'm still leaning to a lead keel!

[NativePaul]

The superstructure is just a light weight buoyant box that moves the center of buoyancy further away from the CoG, so that when it is floating upside down the CoG is high enough above the waterline that it is totally unstable and falls over, when on its side the CoG is so far to one side of the center of buoyancy that it rolls to where the CoG is at the lowest point which is upright.

But that isn't the whole story.

If you imagine a large cola bottle and tape a 1oz weight to one side of it and put it in the water that weight is enough to make the bottle unstable and roll over so the weight is at the bottom, but if you take a flat foam bottle shape of the same volume as the bottle and put the 1oz weight on one side you will probably not notice that it is not floating totally flat and to make it float weight down you have to add enough weight to the rim to overcome the majority of the buoyancy maybe as much as 8lb. The closer to round your cross section is the less weight you need to overcome the flat spots and buoyant projections to self-right or the faster it will self-right for the same weight.

Note the difference in the model and the full size clip the model's superstructure is a simple lightweight buoyant box, the 1:1 boat tries to do the same but the box can't be as light with seats, half a dozen people etc in it, its still buoyant but the CoG is closer to the CoB than the model, thus the model gets tipped onto its side but rights before it goes over while the 1:1 goes over and rights eventually, the model is more seaworthy but would need some weight attached to the cabin roof to reduce its self-righting ability and act in a more scale like manner.