mcet

hi, what scale should have a test rc sailboat to have a similar behaviour than a real boat ?

the aim is to test heeling with rig type (2 or 3 masts), foils and water ballast, and also to test leeway with rudders or daggerboards

thomas.armstrong

Scale sailboats behade diferently than full-scale. Impossible to have similar behaviour. with a 1:10 scale. Maybe if you go 1:2?

mcet

in which way?

I found this thread that is full of armchair "experts" boatdesign . net/threads/appropriate-scale-for-modeling.36201/page-3

if you scale the weight, weight distribution and centre of gravity i suppose it should work similar with a small scale, however the rudders and foils maybe are not that accurate because liquid density and viscosity

Hydro Junkie

And, while I would agree with that, you also have to remember that air and water are consistent in that they don't scale up or down, doesn't matter how you slice and dice it

mcet

yes, their properties are uniform in the same temperature or ambient pressure but remember that ants can be trapped inside water and water striders can walk over it like jelly, in the case of scale the same density or viscosity makes different effect depending of the size of the object and even for the same object size those properties change with speed when falling over water at some altitude is like falling over solid.

on the other hand the same wind speed affects differently depending of the scale size and also when you use scale models it's quite probable that wind and water effect don't scale proportionally to real scale magnitudes ratios

so in the case of fluid dynamics I think the scale models are not that accurate as software because of that and other factors and some people modify skin roughness of scale models to test real boats, but as I said in the case of matching weight distribution, centre of gravity, etc the boat should behave in a similar way in motion performance and heeling by changing rigging, keels, foils I suppose with a plain small scale model