a barge to be towed by a multihull

[pir8ped]

I know, it sounds mad but....

I am considering using a multihull as commercial fishing boat, longlining and using jigging machines in the English Channel. It's a multihull because multihulls don't roll ( I have sailed 30,000 miles in a trimaran, and owned several monohulls since ) and there is the deck space.

Anyway, the idea is looking very feasible, but of course multihulls are not designed for great load-carrying capacity. I can buy a boat big enough to carry the load I need, but what if I store the ice and fish in a purpose-built barge, which is towed behind the multihull? Most of the fishing will be done at anchor, so the barge could be pulled alongside as needed for loading with the catch. I know there would be issues over moving the load between the mothership and the barge, but these may not be insurmountable.

The advantage of a barge is that it can be built of foam, and be naturally insulated. It can have a tight lid to keep out draughts. It keeps the fish separate from the accommodation. The barge itself could be anchored while the multihull explores prospect around various wrecks or lays a longline. The barge could be designed specifically for the anticipated load ( 1 ton ).

I once towed a 30' motor cruiser that had run out of fuel with my 36' 7 ton monohull in a light wind. I was amazed that towing the boat didn't have a noticeable effect on my speed ( 5 knots, with or without the tow ). Maybe the wind picked up a little while we were organising the tow, I don' know.

Any thoughts?

Thanks in advance,

John Pedersen

[Gilbert]

I once asked my father what he considered to be the most important feature or capability that a gillnet boat should have. He said "It should be able to lay alongside a tender and deliver fish in any kind of weather." I believe his answer applies to your proposal as well.

[pir8ped]

I'd have thought plenty of fenders, and good attachment points fore and aft would be all that's needed there, unless I'm missing something. What design feature do you think your Dad will have had in mind?

What I am wondering is how I can design something that will tow OK - the difficulty will be going downwind with a following sea. I guess have the tow rope a wavelength long, perhaps a sort of mini keel at the aft end of the barge to help it not broach with a following sea, arrange the tow so that it is just forward of the clr.

[Gilbert]

Yes, fenders and strong cleats are essential and the boats have to be built stoutly enough to take the strains.
Often the speed of a towing vessel is the limiting factor for speed unless the towing vessel just doesn't have the power to overcome the resistance of both vessels. I would suggest that your barge be long enough to give a displacement hull speed that is about the same as your towing vessel. Then you should have about the same happy circumstance as you did in the episode you described.
Your idea might work out really well for you. The only downside I can think of is you will have two boats to look after instead of one.

[pir8ped]

Gilbert,

I think you must be right about the length of barge I'd need if I didn't want to really slow down the trip, on the way back to port especially. So rather than a boat and a large dinghy, I really would have two boats to look after.

It might be simpler and cheaper just to get the one boat, big enough to carry the load.

Thanks!