The Shipyard ( Dry Dock ): Builds & Questions > Bait Boats

Help Needed - Building Bait Boat - Propulsion Query

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nick1974:
New member here, hello to all.

I have a catamaran grp boat, 29"x 14", weight approx 2.3kg bare, that I will be fitting out for use as a bait boat for my foreign carp fishing, I would like to use a water jet drive system, have seen some information regarding 12v offset impeller pumps that can be used but I think that using bow thrusters would work using the same principle and would keep weight and cost down? 

I am looking to use 2 bow thrusters for the propulsion inline fore/aft, each with own esc to give forward and reverse using tank steering method (or use mixer to give proportional steering from each unit) from transmitter.  I have seen the graupner, robbe and raboesch units, robbe units will be too tall for the hull so I am leaning towards the raboesch units (16 or 19mm tubes) but want to run 12v SLA so this would mean removing the 6v motor from the raboesch unit and replacing motors with mabuchi 385 12v units.  Will this work, hull will be sealed with a removeable cover to access the battery (12v 7 or 10ah) so am concerned about heat from the motors etc.

Boat weight is planned to be around 4kg unladed, 6.5 kg laden - will the use of bow thrusters give me enough thrust for movement?

Any advice appreciated, have seen/read that a few members have built bait boats and would welcome any alternative ideas - not too keen on props as this would require alot of fabrication at the stern in order to keep the props within the foot print of the hull - similar restrictions using jet drives.

Thanks in advance

Nick

Stavros:
I also fish fro Carp and have built a few Bait boats so here goes

I personally don't think that you will have enough oomph to move the bait boat with a Bow thruster

Now how about going into your local Yacht chandeliers and getting some bilge pumps,these will run on 12v,and don't consume a load of current  some thing like this

http://www.rule-industries.com/products/pumps/bilge_pumps/rule_360/iid_236/index.htm

the inlet would be under the water,and the outlet in the stern,2x speed controllers and a mixer and hey presto away you go,don't use a 19mm outlet try 15mm more oomph all the best

Stavros

nick1974:
Many thanks, looks alittle mor like it, I think this type of pump/drive unit would be better suited, only issues being only 1 outlet - will that restrict reverse travel as there is no where to direct the flow with the pump reversed apart fro out the inlet in normal mode, have seen this:

http://www.allpumpsdirect.co.uk/tmccaravan-maceratorpumps

second pump down, the tmc unit.  Only thing with this unit is the weight, 2 of these pumps will be 5.5kg?

I think it will give me the thrust that I'm after

Nick

malcolmfrary:
Way too heavy, almost your estimated fully laden weight.  Using Stavro's idea, you don't really need reverse.  A burst of hard left or right will make it spin like a beetle on a pin, and when it is facing the right way, just go forward.  If you are really desperate for reverse, a reversing flap on the outlet will do the job.

nick1974:
Many thanks for the advice, I have decided to go with Stavros' recommendation and use Rule 380Gph bilge pumps, I have figured a way of including reverse, esc for each pump with a mixer for proportional control left and right.

I will manufacture a water tight housing that the pump will sit in that will be fed from an inlet port that will mate with the moudled inlet on the hull, water will be drawn through the inlet and out through the pump outlet to a port on the rear of the hull, in reverse the pump will draw water in the opposite direction and due to the inlet now outlet will give me reverse travel.

Any advice on materials in which to fabricate the housing?, pump dia. is 61mm and I plan to have 5mm clearance around the pump body to allow for enough water to be drawn into the pump, I have seen ABS plastic pipe in varying diameters, and think that this will be suitable.  Inlets and outlets will be rigid 15mm id plastic pipe.

Thanks in advance.

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