extending hull to gain lift

[schecter]

can anyone help me: my Wellcraft 43 San Remo powered by twin caterpillar 3208, is sitting deeply in the water at the stern. im planing to extend the hull with approx 2 feet with a stainless steel plate. will it help??

[hmattos]

Schecter, We manufacture fast RIBS and most of our boats - 5m to 10 m - have swim platform hull extensions. We add 250mm to the planing surface which adds buoyancy at the stern when in displacement mode, but also helps dramatically in keeping the bow down during acceleration and when planing. The medium vee models plane from 12 knots and are stable up to 45 knots, when the contact area becomes too small. Have a look at our website - www.explorermarine.co.uk

[dereksireci]

Are you planning to extend the hull or just the bottom panel? If you extend just the bottom, the added weight will make the situation worse at the dock but possibly help while running. If you plan to extend the entire hull then that should both add planing surface and bouancy in the stern, which will help in both cases. How about trying a set of hydraulic racing tabs? They are a large controllable trim tabs designed for high performance vessels. Usually they mount on the transom.

[schecter]

im planing to extend the entire hull with approx. 2 feet. My plan is, that the extra lenght of the waterline helps "carrying " the boat under speed, and under load with full tanks, gear etc. The boat is a Wellcraft San Remo, 13,89m lenght overall, 4,42m width, and weighs 16 tonnes full loaded. Engines is Caterpillar 3208, 375hp each.
The real problem is the angle of the boat in planing levels.The bow rises very high, and the boat sits heavily in the water. Speed and fuel consumption ( and visibility!) suffers thereby. Ive tried to contact Wellcraft, but as the boat is more than 5 years old, they know nothing..........!!

[hmattos]

16 tonnes for a 14m boat will require a good deal of speed to get it up on the plane. Obviously the hull extensions will help reduce the pressures required on the hull surface, but there may also be an issue with the centre of gravity being too far back and the shaft - and therefore thrust - angles being unable to get the mass over the planing hump. Any increase of planing area at the stern is bound to help, but I would try a few grp / plywood designs bolted to the transom before spending all the money on a stainless steel construction. With grp / ply you should be able to add buoyancy as well as planing area. Do you have any accurate - GPS - speed figures or any photos of the boat static and underway?
Good luck: Hugh Mattos

[schecter]

Hello Hmattos

The boat is planing at around 14 knots, with a current topspeed of 20.
I have photos of the boat at rest, not under way, and currently no photos of the bottom.I will have some at lay up time.