Help me design paravane system

[Jeff F]

I've read a lot here, and it's very much shaped my thinking over the years. I'm ready to build a system from scratch for my new-to-me boat. Thought I'd crowd source the design and construction details here.

The boat is a Navy Utility 50, round bottom single engine. 15' beam. Cruising speed 7-8 knots. Maybe 35,000 pounds displacement

I'm perfectly willing to give up the deck aft of the pilot house doors. My assumption is that I'll build a self supporting aluminum frame and bolt it down on two pairs of pads on deck. I don't think I care about air draft, and the upper deck is just utility space. I don't mind having it interrupted by the frame. Easy to engineer solid deck mounts. Protected cockpit aft to launch/retrieve fish.

Have at it!

 

[mvweebles]

Beebe's "Voyaging Under Power" has some guidance on design. If I remember correctly, they should be 1/2 to 2/3rds back from bow, so somewhere just forward your salon windows, not the PH doors. You would launch the fish from the cockpit. If you search Yachtworld for Nordhavn 46's, you'll probably find several examples.

Here is a YouTube for Cruising Sea Venture where they install a new paravane system. Not much technical info, but you can get some ideas - outrigger poles appear to be 1.5x beam of boat, maybe a little more. They are in an area well known for fabrication of systems like these so had access to good engineering input. You may want to drop them a line and see if you can get some advice - they seem like nice people. Personally, this isn't something to crowd-source. I'd probably spend a few bucks and hire Dave Gerr. He's done a ton of work on stabilization and my guess would be happy to assist.

Peter

 

[FF]

On both sides there should be a pair of aft lifting eyes .

If they have been removed the access plates should still be there ,and the could be replaced, good strong location.

 

[Pdxstriper]

I would proceed cautiously here. A paravane system deployed places a tremendous strain on the vessel and all the components of the paravane system. These are typically designed by marine engineers.

 

[Larry M]

Jeff: This is from Beebe's first edition (1975). It gives you an idea of the loading for paravanes. He's was convinced that the fish can generate resisting forces up to 10 lbs. per square inch.

 

[mvweebles]

Jeff: This is from Beebe's first edition (1975). It gives you an idea of the loading for paravanes. He's was convinced that the fish can generate resisting forces up to 10 lbs. per square inch.

The footnote on the drawing states "Designed for the 36-foot Garden designed Vega class yacht." That would be my Willard 36. I didn't realize that - thanks Larry.

Peter

 

[Jeff F]

I fully appreciate the potential dangers and forces involved and will proceed carefully. Maybe I was being too flippant about crowd sourcing. But I'd love to collaborate with you folks as I go along. I won't sue anyone

I'm imagining a system that doesn't touch the boat above the deck. I'm quite certain I can tie into the lifting points. Massive support structures available.

And Peter, I think we're thinking of the same place fore and aft. Between the pilot house and the window.

 

[mvweebles]

After seeing the diagram from VUP that Larry posted and watching a few mins of the Sea Venture youtube I posted, if I weren't in an area with experienced builders, I'd give it a shot. I'd drop the Sea Venture folks a note and get an idea of the diameter of the super structure and strongback arch and the cable system (including some tips on retrieval) and scale it to the Beebe diagram.

On second thought, this isn't rocket science. Best path if you're not fairly experienced and tolerant of DIY errors wound be to hire a Naval architect to design the system. But on an older boat, I wouldn't hesitate to just go with my gut instincts coupled with input from a few others who have actually done it.

I launched paravanes a few times off nordhavns. They had push button switches to activate winches to lower and retrieve the fish. Buttons were in the cockpit and knee height so you could keep your hands free. Beyond that I don't remember much. But I actually think the retrieval system may be more difficult to figure out than the structure.

Peter