ROV design 101 - Frame Design

Here are the 10 most important things to remember when designing an ROV frame:

1. Center of Mass directly below Center of Buoyancy = Positive Static Stability.
2. Center of Pressure near Center of Thruster = smooth flight.
3. Vertical thrusters near corners = good dynamic stability.
4. If you will grab something with an arm on the front, put some of the vertical thrusters as far forward as possible.
5. Keep center of mass close enough to center of buoyancy and center of pressure to keep the vehicle maneuverable.
6. Have enough space for all equipment it's intended to fly with (and just a bit more).
7. Add a little more buoyancy than is needed.
8. Control "Scope Creep" or it'll never fly well, even if it can hold a kitchen sink.
9. Do not obstruct the thrusters, as this will significantly effect power and efficiency.
10. Pay attention to Thrust to cross sectional area ratio in the X, Y, and Z axis. It's all about the effective thrust to unit area of the vehicle. Calculate for Forward, Lateral, and Vertical movement separately.

Remember that EVERYTHING in engineering is a trade off. Every designer will need to fine-tune their design based on the desired payload, available parts, and a hundred other criteria.