1) For force due to material weight:
F [N] = m [kg] * a [m/s^2]
Where m is the mass and a in this case is acceleration due to gravity: 9.80665 [m/s^2 ].
2) For force due to pressure:
F [N] = P [Pa] * A [m^2]
where A is the projected area of the hatch in the plane under consideration. If you have a dome hatch, you only need consider the forces in the direction of the axis, since the radial forces cancel each other.
3) For force due to counterbalance spring:
F [N] = k [N/m] * x [m], where k is the linear spring constant and x is the compression / extension distance, OR
F [N] = k [N] x theta [unitless], where k is the torsion spring constant and theta is the twist angle, expressed in radians.
4) For force due to buoyancy, equal to the force due to weight of the displaced water (using equation 1 above):
To figure the mass, m [kg] = rho [kg/m^3] * V [m^3]. Use densities of rho=1000 kg/m^3 for fresh water, or rho=1025 kg/m^3 for salt.
-Sean
On Nov 4, 2009, Alan James <alanjames@xtra.co.nz> wrote:
Hi psubbers,I'm trying to calculate what the lifting force will be on thedome in my hatch when it is just submerged; but aren'tquite sure what I have to take into consideration to calculate this. Any thoughts on this?Thanks, Alan