paravane anti-roll system

[mmd]

Hi, folks. I have been asked to design a paravane anti-roll system for a client, and am having a hard time finding background info on the design of such systems. I understand the principles involved, but it's been a long time since I was up on the current technology. I would like to peruse any recent papers on the subject, especially those related to the calculation of forces, the geometry of the paravanes, and recent developments in the ship-board structures. Anybody got a lead on this? Thanks.

[Dutch Peter]

mmd,

It's not really what your looking for, I'm sure. But I wondered what the system was and the only picture I could find was on this page.
The comments are not to promissing though!

http://www.tc.gc.ca/MarineSafety/bul.../2000/15_e.htm

Regards,

Peter

[Dutch Peter]

I just remember you had mentioned some of your clients are in the fishing industry, so I suppose this is the system your looking for. (just not the right data).

[CDBarry]

You MUST look at the paper by Bass in SNAME Marine Technology a couple of years ago as well as this bulletin. The bottom line is that loss of one paravane can cause the other to capsize the boat, and it has in fact happened as noted in the directive attached above, so it is important you instruct you client on safe handling.

That said, there are several papers from RINA, and ASNE (Fuller) on the design of paravanes, though most are a decade old or so.

[mmd]

Thanks for the fast response, guys. I am well aware of the operational pitfalls of the system, and have discussed this with the client. The vessel is indeed a commercial fishing boat and is based in the Florida Keys. The paravane system is to steady the boat at anchor while the crew overnights before tending fixed gear, and for stabilizing while slow trolling. The local conditions and fisheries participated in results in the boat rarely working in seriously rough weather, so the liklihood of paravane broaching is very low. Progressive instability due to icing is, of course, out of the question in the vessel's operational area.

[Dutch Peter]

mmd,

as I'm interested in anything to do with boating, can you keep me posted on what you find out on this system.

Thanks in advance

Peter

[Tad]

Michael;

The problem is the client will learn how great they are and use them all the time. So you'll have to work with full cruising speed.

Note the first line in the TC notice, "may have contributed to their capsize". I have been aboard boats when a fish was lost, no problem, there is not enough pull to roll a normally stable boat over. Out here on the westcoast fishboats often run with only one fish out, on the "off side" when hauling gear.

The Bass paper is one; also see Roll Damping on Two New England Trawlers: An Experimental Study, by Goudey & Venugopal published in Marine Technology in April 1989. Beebe, in Voyaging Under Power is a decent reference, though not technical. See also Slow Down The Roll by Sharp & Egerton in Yachting, Sept, 1984. And Anti-Roll Devices by Edwin Monk in Yachting, March 1971.

All the best, Tad

[mmd]

Thanks, Tad. Those are the types of references I was after. Also, good point on the "client will learn how great they are and use them all the time" comment. I have adequate data on the vessel's stability (I designed it) to size the fish to well below critical righting moment for the hull. What I am hoping for in the reference list is case studies of existing systems, and any new information on the configuration of the fish.

Thanks again.

Michael

[Tad]

Michael,

Sizing the fish is fairly arbitrary, as I was recently hired to do a system for a 60' DeFever, I did some digging in my old magazine piles. Long time supplier out here has been the Kolstrand Company, which you may have come across but I'll include a link.

Kolstrand Paravanes

Kolstrand sizes by the square inch area in the plan view. They supply units with roughly 120, 200, 300, 500, 600, and 800 square inches. These are all welded steel, so the big ones get real heavy. The 500's weigh 70 pounds!! A popular move out here is to build your own fish with a plywood main surface. This is lighter and the plywood is much gentler on wooden boats.

Beebe used 300's on Passagemaker, and wished for some 200's when running in the trade winds. Out here gillneters 32'-40' use 200's, trollers 36'-45' use 300's, seine boats 50'-75' use 600's. We're building a pair of 500's for the DeFever, as much for handling ease as anything. She's 60' by 16' and about 55 tons loaded. Poles are about 22' long.

All the best, Tad

[mmd]

Seems we're in the same ballpark, Tad. My preliminary numbers indicate about 300 sq. in. for a 43' LOA boat with poles 16' long - length is dictated by air draft under a local bridge. The wild card in my project is that the boat is light (35,000 lbs) with a high top-end speed (26 - 27 knots) in its present configuration. The object is to get better comfort at low speed and at anchor, but allow secure stowing and no adverse effects for high-speed operation. Not your usual west coast troller type of boat.

[Luc Vernet]

Hi Michael
Excuse me, but I do not really understand what stabilizing you expect from paravanes when at anchor = not moving (unless there is a strong current)...?

For low speed and/ or at anchor, with not too much waves, a strong "baloon" with a kind of "cup" above it (I'm afraid I should send you some sketch!!!) rigged at the end of one (or two) poles with fore and aft guys and downhaul was tried by some guys from "Zodiac" Company quite a wile ago. I saw it and the the results were excellent, but never seen it commercialized, so...???

[starcon931]

And doing your research on the design, please keep in mind that needs of wheelchair-bound clients.

I came here looking for information on a powered Catamaran and was left breathless when I saw this model. Is exactly what I have been looking for (+ the solar as an extra)

I do not think it is available yet but if any boatbuilder could produce such a thing, IMHO I believe there is a huge demand for it.

http://www.boatdesign.net/gallery/sh...cat/520/page/1