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I was interested in the various design characteristics of the different subs that are available for RC.
Since I am interested in the Seaview, I thought I would submit what I have researched about this particular sub to start this thread.
I thought I would start with work from Mr Merriman on the Seaview.
Design Flaws and Characteristics
Wedge shape bow and manta fins creates a downward pitch when submerged. This downward thrust can be countered with internal fixed vanes in the nicelles and also functional bow planes.
This peculiar architecture of the Seaview also creates something else.
A large Bow-wake = lots of drag
(Largest ever seen by Mr Merriman)
Certainly my own little piggyback PL Seaview on a Walmart USS Dallas showed a huge difference in bow-wake
Surface turning radius is average for the Seaview. But submerged it has some design flaws. Yaw stability increased by cadillac fins which makes submerged turns large. However, high speed underwater turns have a roll issue called "snap-roll".
Fast underwater turns have snap-roll due to the cadillac fins which is countered by the manta fins and according to Mr Merriman the sub would actually be non-functional without the manta fins.
Since I am interested in the Seaview, I thought I would submit what I have researched about this particular sub to start this thread.
I thought I would start with work from Mr Merriman on the Seaview.
Design Flaws and Characteristics
Wedge shape bow and manta fins creates a downward pitch when submerged. This downward thrust can be countered with internal fixed vanes in the nicelles and also functional bow planes.
This peculiar architecture of the Seaview also creates something else.
A large Bow-wake = lots of drag
(Largest ever seen by Mr Merriman)
Certainly my own little piggyback PL Seaview on a Walmart USS Dallas showed a huge difference in bow-wake
Surface turning radius is average for the Seaview. But submerged it has some design flaws. Yaw stability increased by cadillac fins which makes submerged turns large. However, high speed underwater turns have a roll issue called "snap-roll".
Fast underwater turns have snap-roll due to the cadillac fins which is countered by the manta fins and according to Mr Merriman the sub would actually be non-functional without the manta fins.
the manta-fins produce a counter torque (outboard rolling moment, counter of the vehicles turn) that works to negate the de-stabilizing inboard torque produced by the SEAVIEW's sail and 'V' shaped 'Cadillac' fins at the stern. The manta-fins contribute to the dynamic roll stability of the SEAVIEW in a tight turn. As the submarines angle of attack about the yaw (turning) axis increases, and starts to 'skid' into a turn, a situation occurs at the manta-fin tips (those tips well below the vehicles longitudinal center of rotation) where the inboard manta-fin tip begins to generate an upward moment (force) and the outboard manta-fin tip produces a downward moment. These two forces induce a torsional moment that works to right the boat in the turn; the manta-fins improve the boats roll stability dynamically in a turn.
The significant maneuverability problems with this boat occur as a consequence of a turn while submerged. Sea-trails taught me to 'ease' the SEAVIEW into high speed submerged turns. To put the rudder hard over while running at any significant speed rolls the boat into an uncontrollable dive to the bottom. (American LOS ANGELES class attack submarines have the same problem). Other than that, and the SEAVIEW's woefully poor backing down ability, it handles pretty much like any other r/c submarine.
The only vice I can lay at the feet (fins) of the manta-fins is that they work to de-stabilize the boat in the pitch plane and contribute a great deal of flow and wave-making drag. The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW's speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished!
But, keep in mind that the two pitching forces (shape of the hull forward, the fixed vanes in the nozzles aft) are directed down; the net force on the vehicle is a downward one. However, this downward force acting on the submerged submarine is of low magnitude and is easily countered by operating the boat at a slight up-angle or simply by cranking in a bit of 'rise' on the sailplanes.
After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a 'traditional' type r/c submarine.
The SEAVIEW, as an r/c submarine, can be made to be dynamically stable in pitch and yaw as it travels submerged - without need of non-scale 'stabilizing' fins or control surfaces.
The significant maneuverability problems with this boat occur as a consequence of a turn while submerged. Sea-trails taught me to 'ease' the SEAVIEW into high speed submerged turns. To put the rudder hard over while running at any significant speed rolls the boat into an uncontrollable dive to the bottom. (American LOS ANGELES class attack submarines have the same problem). Other than that, and the SEAVIEW's woefully poor backing down ability, it handles pretty much like any other r/c submarine.
The only vice I can lay at the feet (fins) of the manta-fins is that they work to de-stabilize the boat in the pitch plane and contribute a great deal of flow and wave-making drag. The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW's speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished!
But, keep in mind that the two pitching forces (shape of the hull forward, the fixed vanes in the nozzles aft) are directed down; the net force on the vehicle is a downward one. However, this downward force acting on the submerged submarine is of low magnitude and is easily countered by operating the boat at a slight up-angle or simply by cranking in a bit of 'rise' on the sailplanes.
After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a 'traditional' type r/c submarine.
The SEAVIEW, as an r/c submarine, can be made to be dynamically stable in pitch and yaw as it travels submerged - without need of non-scale 'stabilizing' fins or control surfaces.
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