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Old 09-17-2015, 01:02 PM   #61
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Paravane install

Ok. Thanks.

I need to decide if I want/need the sails more than the covered slip.

Or maybe that triangulated mast could be foldable somehow.
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Old 09-19-2015, 11:49 AM   #62
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The dimensions of my "towed bodies" are 14" long by 22" wide, not including the "proboscis" of the weight. I measured the the fish of another vessel and they were 18" long by 27" wide, considerably larger. How large are yours Larry? Should I go larger, as I still have some roll in beam seas?


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Old 09-19-2015, 11:51 AM   #63
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The bigger they are causes more water resistance when towing them, but would further dampen the roll. like everything else on a boat, it's a trade-off.
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Old 09-19-2015, 12:07 PM   #64
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The bigger they are causes more water resistance when towing them, but would further dampen the roll. like everything else on a boat, it's a trade-off.

Yes, but I'm concerned about the stresses on the poles and support structures.


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Old 09-19-2015, 12:07 PM   #65
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The bigger they are causes more water resistance when towing them, but would further dampen the roll. like everything else on a boat, it's a trade-off.
Seems like the bigger the fish, the more force it puts on your rig as well. Are you given a rating for how much your supports can handle when they're installed?
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Old 09-19-2015, 12:51 PM   #66
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The dimensions of my "towed bodies" are 14" long by 22" wide, not including the "proboscis" of the weight. I measured the the fish of another vessel and they were 18" long by 27" wide, considerably larger. How large are yours Larry? Should I go larger, as I still have some roll in beam seas?...
Jim: The rig can take the bigger fish. We've traveled 10K plus miles with the larger fish and no issues. The builder/designer expressed his concerns after we had gone from AK to MX (a little late). We talked about it and he sort of patted him self on the back for the build. lol

Right now we're considering the medium size fish (~210 sq"). They are lighter, smaller and should be easier to handle. We'll loose a little performance but I'm not sure it will be that much. Our cruising area will probably now be the Bahamas and EC so our open water travel will be less. If we go through with it, I'll post our results this winter.

Our fish have 3 adjustments for the tracking angle. If you have those, you can move to the rear which will add more resistance. We use the middle position.

The fish we have now are ~28 x 21" and the front weight is 27.5 lbs.

The last 2 pictures are when the plywood failed after 4 years and ~8K miles. The fish spend a lot of time in the water when we use the paravanes as rocker stoppers when anchored so no real surprise.
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Old 09-19-2015, 02:17 PM   #67
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Thanks Larry. I calculate the area of my fish as 0.5 X 14 X 22 = 154 sq in. Your current fish are 294 sq in, so almost twice as large. I have 5 holes to adjust the tilt. Currently I have them on the centre hole.


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Old 09-19-2015, 02:26 PM   #68
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Thanks Larry. I calculate the area of my fish as 0.5 X 14 X 22 = 154 sq in. Your current fish are 294 sq in, so almost twice as large. I have 5 holes to adjust the tilt. Currently I have them on the centre hole...
Jim: According to Tom Davenport, who did the final design/build on both of our systems, his suggestion was around 200 sq" which would be the medium size fish that I referenced earlier in this thread and are looking changing to. I think Tad had mentioned around 198 sq" (?). If I were you, I'd consider the medium size.
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Old 09-19-2015, 06:58 PM   #69
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Good. Thanks Larry. I'll work on that, perhaps fabricating something out of starboard. I believe my shipwright has made these before so will consult with him.


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Old 09-19-2015, 10:34 PM   #70
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Paravane install

Has anyone try building parvanes with a reversed hydrofoil?
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Old 09-19-2015, 10:46 PM   #71
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Has anyone try building parvanes with a reversed hydrofoil?
Michael Kasten of Kasten Marine has designed/developed a NACA foil shaped paravane.

Roll Attenuation and Bilge Keels

Here's a quote about the NACA foil paravanes from the Kasten Marine web site:

"I have designed such a set of low drag NACA 00xx series foil shaped paravanes for Charles Vollum for use on the 25 foot Boojum. The paravane body, wings and fin are accurate high-lift low-drag foil shapes. Sea trials have verified the effectiveness of this strategy in terms of reduced drag. The foil shaped paravanes are also able to maximize lift for the greatest stabilization effect. We estimate that these foil shaped paravanes cut the amount of drag in half as compared to typical crudely shaped steel paravanes made out of flat plate and a cylindrical weight chamber."
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Old 09-19-2015, 11:50 PM   #72
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... And paravanes just aren't practical for shallow water running like the ICW. And then there's the bridge thing...
Why would one need stabilizers when operating in a protected, narrow channel? Can't handle wakes?
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Old 09-20-2015, 01:09 AM   #73
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Has anyone try building parvanes with a reversed hydrofoil?
Here's another one I just found by doing a U.S. Patent search:

Patent Images
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Old 09-20-2015, 02:43 AM   #74
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The last 2 pictures are when the plywood failed after 4 years and ~8K miles. The fish spend a lot of time in the water when we use the paravanes as rocker stoppers when anchored so no real surprise.
I'm really impressed that they lasted that long. I don't know why, but I would never have thought to make them out of plywood. I just assumed they were all steel or alumin(i)um. Did the fish split suddenly and violently, or did it slowly crack over time?
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Old 09-20-2015, 08:25 AM   #75
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I'm really impressed that they lasted that long. I don't know why, but I would never have thought to make them out of plywood. I just assumed they were all steel or alumin(i)um. Did the fish split suddenly and violently, or did it slowly crack over time?
It split on a roll but wasn't sudden. We were in beam seas and didn't know anything had happened until I went to retrieve the fish. We had commented about the sea state getting worse because of the way we were rolling, not realizing the fish had folded 90 degrees.

We once hit a dead head off the coast of WA. That sounded like a gun shot as the fish pretty much disintegrated.

We do carry at least one spare.
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Old 09-20-2015, 09:58 AM   #76
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when you lost one did the boat roll differently or dangerous?
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Old 09-20-2015, 10:40 AM   #77
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when you lost one did the boat roll differently or dangerous?
We've never lost one completely. It took 15 minutes to replace the fish when we hit with the dead head and all we did was head up to replace it. When the swivel broke it was during the day and in flat seas. There were times though, that if we lost one, it would be uncomfortable/unsettling but I wouldn't say dangerous.

The KK42 was designed without stabilizers and has a range of positive stability to 85 degrees.
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