Understanding Stability and
Buoyancy in ROVs
Fred Donelson
Bob Richards
Jim Fannin
When you think about getting into a
water craft, there are at least two
major factors that you consider …
Most folks would like
to ride in a craft that
• Doesn’t tip over (is stable)
• Doesn’t sink (is buoyant)
When designing and building an
ROV, we want the same thing:
• A craft that is stable and
doesn’t tip over
• A craft that is buoyant
enough so that it can be
maneuvered easily up or
down without using too
much energy
So a very simple but important
question is:
How do we make things float?
to find out …
So at least two factors are
important to consider for
buoyancy:
• Weight (mass x gravity)
• Volume
So, based on these two factors
…
Would a kayak float?
Click on the
picture at right to
find out!
Yes … provided the
conditions were
right!
Now when things are
sinking, rotating or
floating, that most
likely means some
physical forces are
involved!
So click the link below to find out
the mathematical calculations
relating the forces of buoyancy and
the forces of gravity
http://www.youtube.com/
watch?v=woIct8d6j_8&feat
ure=relmfu
Of course, watching
someone else do these
calculations isn’t as good
as actually playing with
them yourself!
Now go to this link
Read the instructions, watch the
demo, and then play with the
simulation until you have a good
understanding of how changing
volume or changing mass affects
the interaction of the forces of
buoyancy and gravity!
Think you have it now?
How much weight can your ROV
hold without sinking?
Watch this video demonstration using
a plastic cup as a simulated ROV!
http://www.youtube.com/watc
h?v=HTMwM81J48M
Stability of an ROV is affected by
the distance between the center of
gravity (Cg) and the center of
buoyancy (Cb)
Could you build a simple craft and
illustrate this principle like in
this clip?
Can you come up with a general
“rule” that would ensure that your
ROV would always remain stable
and not tip over?
(Hint: think relationship between
Cb and Cg)
Think you have this
buoyancy/stability thing down?
Take a few
minutes and
click on this
guy to see!