SECAT (Surface Effect CATamaran)
The US Navy funded some studies in the early eighties of a boat that utilized catamaran-like sidehulls with each sidehull a generic SES. While the SECAT's analytical and model studies were encouraging there appears to have been no follow-on efforts on actual full size or prototype vessels. The generic SES is a pressurized air cushion vehicle that incorporates full span flexible seals fore and aft (bow and stern) between parallel sidehulls. In the Navy's concept, the twin generic SES sidehulls were separated by and connected to a cross deck or wetdeck structure. Not only were their sidehulls parallel, but each sidehull had sides that were thin and plate-like and ran completely up to the wetdeck. Outward extensions of the wetdeck actually formed the upper surface of the pressurized gas recesses.
SECAT's idea was that each sidehull's flexible bow seals would give to waves and they could pass through the sidehull recess without molestation unless they were of sufficient height to contact the recess wetdeck. SECAT also requires extra structural weight for the long thin cantilevered sidehull plates and would have very poor off-cushion performance. It would appear that concern for the aforementioned plus the very high, narrow, and high maintenance flexible seals in each sidehull recess with the related tremendous increase in wetted area resistance in high seas, due to the extra vertical movement of the flexible seals on the inboard sides of each sidehull and resulting increases in wetted area, compared to a generic single chamber SES, probably discouraged further efforts.
Each of SECAT's sidehulls had a rectangular footprint on the water surface. The SECAT's design used full, to the wetdeck, depth recesses with full depth flexible seals fore and aft. That design used parallel thin sideboards, that extended all the way to the wetdeck, to form each side of the catamaran sidehulls. It can easily be seen that the SECAT's design must have functioned much like a lilypad with the blowers off.
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