Paravane for normal keel boat

I was wondering about that, but I assumed that the rig would have to also be designed to work perfectly well without the paravane, since otherwise sailing in any traffic would be all but impossible.

I hate to consider how one would go zipping across a busy harbour on a summer Sunday, trying to make sure that everyone from ferries and 40' gamefishing boats to jet skiers, yachts and kayakers was aware that you had a lethal wire and torpedo sitting 7m off to one side! In Sydney Harbour someone would probably get sunk or garrotted before you got to the first mark or your anchorage.

 

Where you connect the lines?

You are the one who is working on a kite boat project? ?

 

Yes. The rig and the entire boat designed for normal operation.

 

Colonia del Sacramento , Uruguay.

 

The tension on the cables to the top is almost 0 when is upright. If you compare the compression with and without paravane on flat water is less. The problem is there is swell the boat is going up and down on different way than the foil. That canot be good for the materials.

 

I first thought Juan Lacaze

 

Juan lacase is 25 miles from there.

 

Now I understand the drawing . These open and close. When close pulls down.

 

If I can get to align the center of pressure of the sails with the paravane force then I will not need deep regulation

 

I have been away from this forum some time, therefore my late reply, but I think I have to make some comments on this thread.
Seakeeping: The key to make a paravane follow the water's surface is to make it very light and use hydrodynamic forces, not buoyancy and gravity, to control submergence. When designing the paravane for the speed-sailer e.g. I estimated the vertical acceleration to the order 10 or even 20 g at speed if there were waves. The popular way to do this is to make a curved paravane, where the force-vector changes direction more upwards with deeper submergence, and vice versa for less submergence. The drawback of this configuration is that it requires relatively high cl at the surface-piercing part, which can cause ventilation, especially in waves. I have observed this in model tests I did some 30 years ago.
My design keeps submergence in a similar way as the "seadog" developed by Paul Ashford, AYRS 114. But I have the surface-sensor straight forward of the main foil. And some other differences in the configuration. The surface-piercing part has very low cl. The speed-sailing paravane, that is designed for a side-force up to 7 kN weighs 4 kg. And it stays in the water even when there are waves. See e.g. the pictures from our speed-sailing home-page from 2004.
Rig-loads: when sailing with a paravane the righting moment is transferred to the rig by the paravane-cable to the mast-head. This gives a much smaller compression-force on the mast than if you transfer the same righting moment by the shrouds, with a factor 10 shorter lever. However, the almost unlimited lateral force from the paravane allows for much more driving force in the sails, so you can get high forces in sails, sheets and the rig also with a paravane, but the forces can be distributed a little different.
Tacking: I have experimented with different ways to change direction of the paravene, -gybing, flipping and shunting. The most reliable way so far has been shunting. The paravane I tacked with my Shark-24 on the Youtube-clip was a shunting one.
My experience from the shunting paravane on the Shark-24 is that it is a little tricky to tack a keel-boat in a way so it does not move too much to windward, so it catches the paravane-lines. Therefore, I would choose a proa for sailing with the shunting paravane. A fully flying kite (the ultimate-sailing concept) would also work of course.
An alternative to the proa is a boat designed for gybing, not tacking. Here you can use either a shunting paravane or have a starboard and a port paravane that you shift when gybing. I have developed systems for launching and retrieving paravanes on the Shark-24. And I have tried this when tacking, but gybing will work better if the rig of the boat can be designed for it. (A square-sail or a windsurfing-style rig e.g. are better suited for gybing than the present rig on my Shark-24.)
Another drawback of an ordinary keel-boat for paravane-sailing is the keel, that can get too much lateral force, so you have to compensate with the rudder. A lateral plane moved backwards will allow more stable sailing with a paravane.
So my conclusion is that paravanes can give very efficient and stable sailing, but that the boat should preferably be built for paravane-sailing. I hope I can get the possibility to develop this concept after my present Foiltwister hydrofoil powerboat prototype.

 

Like Alexander said, get hold of AYRS booklet 114 and read about Paul Ashford's anchor dog. Your design resembles it, but needs three more features to work like the anchor dog, and another two modifications to the setup of your lines may help.
1) The cross bar on the T-foil should not be perpendicular to the stem. More like an italic T, where the left side of the crossbar would be the part deeper in the water. I built mine so that a vertical line from the left and of the T would just touch the stem of the T at the bottom (when it is oriented as in this text)
2) The stem of the T-foil should be swept forward. I also gave it an asymmetrical profile. Then leeway will make the stem of the T push the aft end of the paravane up. The crossbar of the T is angled so that it pulls down, and if the stem is swept forward, it pulls down further forward. That makes the whole paravane pitch down. That moment is counteracted by an inclined surface-piercing foil where you have a bottle. When the forward foil comes out of the water, the pitching moment from the swept-forward
3) Don't use buoyancy to control pitch. The maximum force you get out of that stays constant, while the forces from the foil that you are are trying to control can grow quite large.
4) Paul Ashford used a forward control line to adjust the paravane's yaw angle relative to the boat. I think that is a good idea. A single line gives you a constant angle of attack, meaning the paravane pulls hard even on a reach or downwind when you don't need it to do that. Having two parallel lines means you can give the paravane constant yaw angle relative to the boat's centreline. Not quite parallel lines can give you some compromise between the two.
5) You need a bridle to get something that is stable in roll. I find that not so easy to explain with words only. I published some calculations and diagrams in AYRS Catalyst 23, which you can read and download from http://www.ayrs.org/catalyst/Catalyst_N23_Jan_2006.pdf. That specific topic begins in the last paragraph on page 23.

My article also shows a design for a shunting (two-way) version of Ashford's anchor dog. I have a new design that I will test in the next few months.

It seems I can only link to pictures already uploaded elsewhere, not upload here directly. Is that correct? I have photos of my Ashford anchor dogs, but not uploaded anywhere.

 

Thanks a lot for your posts Alexander! I am following your work with great interest! Also, sorry for late posting in this thread but I actually think the headline question is still most valuable. As the paravane balances high forces in the rig without much compression, I really think it would be great for model-boats. Those could then be buildt with extremely low weight-to-sail-area and thus you could play around with different surface following solutions, long double-stepped v-hulls, WIG-crafts, foils etc... For boats with crews, the keel-boat I think would probably not be the ideal since it at least not where I live meets winds that are not balanced by the keel. In higher winds, even with a paravane, many keel-boats, such as the Shark-24, would I guess, anyway be hard to get above the planing threshold.

But when it comes to most sailing dinghies I think it would be perfect! Just sheeting in and hanging on in a Laser (... surfboard with 8 m^2 plus sails, 29er, 49er, Aussie 18) would be wonderful. It would be another game of course with more distance between the boats. And you need to be careful to have colorful flags not to accidentally sail into the paravane wires. But what a brilliant view such a fleet would make!