Tunnel Hull Design for 60' oyster dredge

[Oystersrus]

Hello,

I am looking for information on designing a propeller tunnel for a shallow draft oyster dredge. I need a place to start and am looking for a design book that can give me some of the basics. We have a twin 65' aluminum dredge now, but the new boat will be a single screw. The 65' has a tunnel for each prop, and the props are partially out of the water when she is sitting at the dock. Underway the tunnels are designed so the props pull water into the tunnel and jet it out the tunnel exit. A book that had some basic technical informetion on tunnel performace charectoristics and design considerations would be perect. A book that covered overall basic hull design would be a plus.

Thanks, Brian

[tom kane]

The thread..Design help making a tunnel may have some useful info.

[cyclops]

I did a web search for someone 1 year ago using I think-----tunnel hull boats or tunnel hull bass boats. Came up with design requirements ,veiws, everything you are looking for. Most of them are in the Texas area.---------Do you guys get that shallow when loaded at low tide?

[silverback]

Still in need of tunnel info? I have a few comments for you to take under advisory. Tunnels with the blade tips out of the water are wrong. Tunnels are not straight in shallow draft applications. The top of the tunnel starts dropping right after the propeller. Therefore, the transom at the end of the tunnel is lower than the blade tips. The reason you have to do this is to keep solid water going to the props in reverse. When you back down, a wall of water forms against the transom.
You will not have spade rudders. The pintle bearing housing should drop out the lower side of the skeg. This feature gives you working room to get the rudder in and out because the rudder palm will be close to the top of the tunnel. Working room is small, you need every inch.
Removing the propellers requires care. When the prop starts down the taper, you are losing overhead clearance quickly.
Have you considered manuerverability of a single tunnel vessel? Tunnels tend to direct thrust quite well. Bowthruster? Do you have a hydraulic dredge set up to divert water for manuervering?
Good Luck