xiaohuangdou

Ever since the very first experimental wigs sale boats have been built in the nineteen-thirties, longitudinal stability has been recognised as a very critical design factor. When not designed properly WIG boats show a potentially dangerous pitch up tendency when leaving (strong) ground effect. Powerboats sometimes show the same tendency, when they meet a wave or a wind gust they may suddenly flip backwards.
The reason for this behaviour is the fact that the working line of the lift vector of a wing is located relatively far aft at very small ground clearances and moves foreward when climbing out of ground effect. The stability problem can be overcome by installing a relatively large horizontal tail and although a WIG boat cannot be stabilised by c.g. movement alone, the location of the c.g. is very important for achieving acceptable longitudinal stability. A more indepth explanation is found in the theory section.
Some wing planforms are more stable than others, the reversed delta from Lippisch proved to be very good, therefore it has been very popular lately (e.g. in the Airfisch series craft). Not only the planform, but also the wing section is important for stability. Recent research showed that wing sections with an S-shaped camber line are more stable than conventional wing sections. Many new designs have such an S-foil.