Optimal sailboat for towing things

This is a follow up on this thread though that isn't necessarily relevant information.

If you had to tow a large raft with a sailboat, what kind of sailboat would you use and what would be the optimal type of sailboat for towing things like rafts, pontoons, barges?

-How did people manage this before steam engines, or did they?
-What should be the relation between the towboat and the towee in terms of mass and/or sail area?
-Aside from tacking, what would be the main difference between towing something large behind a sailboat vs. towing something large behind a motorboat? I would assume you'd want a long tow rope.
-And finally to keep this relevant to this section of the forum, if you had to design a sailboat specifically for the purpose of towing rafts, pontoons and barges, how would you do it?

 

Towing your island would be best done with a motor boat.
It doesn't have to be complex or expensive, it just has to be powerful enough to fight unexpected wind and tide.
I suspect you could get away with say around 50 hp, which is relatively inexpensive, but small enough to start by hand if you have a starter motor problem.

The boat itself, can be a simple plywood boat, of easy construction. It would be a good utility boat, so you can go and pickup shopping and supplies, tools etc.

You may not use a long tow rope. Its quite acceptable to tie the boat up against the raft, and power the whole thing tied together. This technique is used a lot, and can solve many problems.

Something like this perhaps ? What's the cheapest way to get a 17 ft motorboat? http://forum.woodenboat.com/showthread.php?131422-What-s-the-cheapest-way-to-get-a-17-ft-motorboat

 

Thanks for the reply, but that wasn't the answer I was looking for. I can tow my island with a motor boat, and I have towed it with a 200HP utility boat in the past.
If I wanted to tow it long distance, fuel costs would get pretty high. Besides, I don't feel like burning up than much fuel if there's an alternative. I really love sailing, and I would like to know how a "sailboat-tugboat" should be built or what modifications could be made to an existing sailboat to make it a "sailboat-tugboat". It seems pretty obvious that if a small sailboat can tow a dinghy, a large sailing ship should be able to tow something bigger. But what other variables are there besides size?

 

There's the story of this tugboat fitted with sails, which admittedly used sails only for assistance with the engine contributing most of the power. Still, it's pretty much just a normal tugboat with sails. How could this be improved so that you would get 70% sails and 30% engines, or 90% sails 10% engines?

 

I have been on that sailing tugboat and was fortunate enough to meet Captain Lane. His son now runs Rebel Marine at Norfolk

RW

 

One idea I have is a catamaran where the raft being towed is sandwiched between the hulls. Probably with large keels and stuff to compensate for the poor hydrodynamics of the raft. But I only have monohull sailing experience, so I have no idea how a catamaran would behave if you had a raft underneath it and what you would need to do to compensate for that.

 

Cool, it seems like a pretty unique boat.

 

Hi Katti, towing this looks potentially dangerous...like an accident waiting to happen. I wouldn't tow it unless it was built on a hull form that could be controlled with a rudder. Some have mentioned a barge type hull. That would not only be more stable, but also easier to calculate. If I may ask some basic questions:

1. What is the main mission of this floating island project?
2. Precisely how big is it (length, width, weight, approximate static displacement)
3. What rivers, seas, oceans do you plan to explore and for how long?

Definitely keep a long leash (at least 100 meters or so) if you plan to tow it. Any notion of using a sailboat to tow it would be up to mother nature and many other variables depending on how it's built. You don't want that thing smashing into another vessel.

 

1. It's kind on an artsy thing, but I want to explore what kind of potential floating islands could have in marine environments. Like agricultural, environmental etc.
2. Not that big now, less than 200 square feet. The plan is to expand it to about 23 feet wide and maybe twice as long. The displacement would be something like 6-10 long tons, currently less than 1.5
3. The raft is currently in the Baltic Sea, so at least around here. But I'd like to go further.

 

Like this

 

you don't want to get the towed raft to get anywhere near the tug, especially as it won't have brakes. But a catamaran might work with a long bridle from each stern

RW

 

==========
I had never heard of Capt. Lane Briggs-thanks for the heads up-what a great guy!
index.html http://www.tugantine.com/

 

I was thinking along the lines of securing the raft to the catamaran hull from many points so that the catamaran becomes more like an extension of the raft. Hypothetically the catamaran would be custom built for the purpose with extra reinforcements in the hull and whatnot, and the raft is kind of squishy so it wouldn't immediately go through the hull even if it were to hit with some speed. I do agree that this is kind of crazy out of the box thinking and that a long towline is the most reasonable option. But I'm in no hurry to get anywhere yet, so there's no harm in playing around with different ideas, even crazy ones.

 

Hope some one more qualified can help out here. In a conventional sail boat the relative disposition of the sail and the hull and keel is critical. The drag of a large and ill defined towed mass will affect this relationship considerably, pulling the hull into a position other than that needed for sailing. From my windsurfing days, the only way to get over this was to tow by tying the hawser around the mast, allowing the hull freedom to rotate without the drag of the tow. you then have to deal with the hawser sweeping across the deck.

 

That's what I thought. Even on a normal tugboat the hawser is attached near or slightly abaft its center of mass. With the pull of the tow on the stern, it is almost impossible to turn the boat without changing the attachment point of the hawser (at least if the towing boat is lighter than the towee). Coincidentally, dropping a drogue and changing the attachment point of the line is exactly how you would turn your boat after losing your rudder.