8m Hysucat RIB

The 8m Hysucat RIB has been developed by Hoppe/Conradie by jumbodizing the 6,5m Hysucat so far with nearly 500 units sold.

The hull has the same typical Hysucat hull with fully asymmetrical demi-hulls connected by the double arc-tunnel which has the ventilated tunnel step behind the bows.
The foil system consists of a mainfoil slightly forward of the longitudinal center of gravity and twin rearfoil struts near the transom on the tunnel vertical walls.

Several 8m Hysucat have been built over the last 3 years. They are usually equiped with twin 115 to 150 HP outboard engines running in propeller surface mode.
The presented 8m Hysucat, however, has twin 200 HP Mercury Ourboard engines installed on the special wishes of the client. The gear boxes are of the racing type with the cooling water intakes below the gearbox bosses to prevent air intake at high speed when the propellers running semi-submerged.
The total operative weight of the tested 8m Hsysucat is between 2,6t and 2,9t.
Initial trials were run off Gordon's Bay in False Bay with winds of around 30 knots South-East which creates a very choppy sea with white horses and short wave lenghts. Trials were run with three persons onboard and the well experienced helmsman Malan Conradie by going at different directions to wind and waves.
The boat has considerable acceleration and also decelleration which requires the passengers to hold tight even on their elastic chairs. At the will of the helmsman the boat can fly over wave crests or cut smoothly through them, landing smoothly on re-entry.

The boat ran unbeliveably smooth in these choppy sea conditions. The top speed was 118km/h which is 63,714 knots up-wind and down-wimd with maximum engine rpm's of only 5000 rpm even though top speed of engines is 6200 prm. This indicates that the propellers are still too deeply immersed or the propeller pitch is on the large size.
There was also hardly any rooster tail visible which proves too high propeller arrangement. In future tests the engines will be set up slightly higher but this requires some transom extension upwards.
The power ratio ep (inverse of transport efficiency!) was ep=0,35 which is still relatively high and indicates that higher speeds will be possible.
The Froude Displacement number FnD was 8.9 which indicates absolute racing class type.

The general conception of the hydrofoil speed capacity is about 60 knots. For higher speeds only super cavitating profile sections are useful. However, this 8m Hysucat does not indicate such speed limitations and has reached 70 knots in smooth water. This proves that the profile sections used in the Hysucat designs can be used at higher speeds without any performance limitation. The foils might be partly ventilated or running with hyper-ventilation effects as it was already observed on the mainfoil of the foil assisted E-Cat by Halter Marine / USA, for which a video of hyper-ventilation will be placed on You-tube ( check back for a link in the future )

Further research in extreme hydrofoil speeds is desirable.
A video of the 8m Hysucat in Struisbaai as an Andrenalin-Wave-joy craft for tourists can be found on You-tube (http://www.youtube.com/watch?v=NxHPkhcDlRQ )