Brainstorming! Suggestions to propel a FRP Trawler

Ok I am reading the docs attached.

By the way I don't have enough room for two engines and 12,2 looks a bit slow velocity.

With a Controllable Pitch Propeller without ducts, how length we will need to get 13 knots??

 

CPP without Ducts.

I mentioned that you keep Lwl=32.7m.

 

Type mismatch

Lwl=32.7m

 

Really nice docs! Thank you for my project will be really useful to calculate coefficients, propellers and power needed.

So between get a 13 knots without ducted propeller or get 10 knots with ducted propeller...
In this kind of boats which we don't need to drag huge nets to fish shrimps and octopus, will we choose less thust and better top velocity??

 

I ran the hull dimensions and coefficient using the Newman's method of resistance prediction. Figure shows which parameters gives the least resistance. Van Oortmensen resistance method will predict more accurately as it is suited for fishing boat hull type.

 

I have been working with trawlers a fair bit lately. The main issue is fuel consumption. To this end you probably steam for 1 day out fish for 12 or more and steam back 1 day so you will only need the max velocity for less than 14% of your trip. Depending on your fishery you may be trawling at 3 to 6 knots. The fishing time is what you need to look at and often the drag from the fishing gear dwarfs the resistance of the ship hull so you need to have a good handle on what fishing gear loads you expect to see.

One of the best scenarios is a single CPP prop in a duct with a shaft generator and a variable speed engine. A small MAK or ABC engine is a good option as the engine needs to be able to operate in Combinator mode with the CPP system, most CAT's don't do this.

The Combinator mode works with the engine rpm and the prop pitch to match the engine performance curve so you are optimizing the power available. To get the shaft generator to work correctly with varying rpm you can use a DC bus "majic box" that will give a constant frequency feed out in AC to a traditional AC switchboard. The beauty of the DC majic box is you can feed in aux. gens or regeneration power from the trawl winches and not worry about synchronizing or frequency. Aspin and Kemp Associates (AKA) is a company that could help on the electric DC side of things.

Another thing on a fishing vessel a bulbous bow can often be ineffective for reducing resistance as the vessel speeds are to low or because the draft and trim changes so much the bulb is not at the correct depth. Bulb may help reduce motions but for most boats it is an extra construction cost and adds to resistance.

Just a few thoughts to mull over.

 

I listened about that system to avoid synchronizing issues with the different electronic equipment on board.

So maybe One Propeller CPP in ducted with that system is the best option to engines not too much powerful and it would be able to place in a smaller room.

Anyone knows what are the loads to drag twins nets with shrimps and octopus for a 32 m ship??