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Old 04-03-2018, 05:53 AM   #121
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Very nice boat there, Simi ! What will the mast-system look like, and how does she roll - is she stiff or tender ?
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Old 04-03-2018, 06:04 AM   #122
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Btw, I found this clip from a show that aired here 7 years ago. The experienced captain/host takes us around the coast in various historical boats. This piece is with a 75 footer, in 10-15 ft seas off the coast. The host is saying that the beam seas are terrible, and that he must try and stay on course. I can hear the swearing from inside the wheelhouse, possibly from the cameraman or the host himself And this is why I installed paravanes .


https://tv.nrk.no/serie/norskekysten...ode-3#t=35m46s
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Old 04-03-2018, 09:57 AM   #123
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Regarding the position of the paravanes or flopper stoppers. I'm just re-reading Bob Beebe's book "Voyaging under power". He insists that the paravane rig should be positioned at 28% from the stern preferably at a bulkhead to deal with the stresses.

Putting it further toward the bow inhibits steering response as the paravanes fight any course correction. He also mentions increased drag the further forward the vanes are positioned. The paravanes will also try to prevent the bow from rising into oncoming seas the further forward they are. Beebe has a whole chapter on paravanes.
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Old 04-03-2018, 12:52 PM   #124
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Originally Posted by gsholz View Post
Regarding the position of the paravanes or flopper stoppers. I'm just re-reading Bob Beebe's book "Voyaging under power". He insists that the paravane rig should be positioned at 28% from the stern preferably at a bulkhead to deal with the stresses.

Putting it further toward the bow inhibits steering response as the paravanes fight any course correction. He also mentions increased drag the further forward the vanes are positioned. The paravanes will also try to prevent the bow from rising into oncoming seas the further forward they are. Beebe has a whole chapter on paravanes.

He is probably right in saying that 28% is the perfect position, but I feel fairly confident in saying that any position behind of CG/50% to 25 % of lwl is acceptable, if your boat has a good rudder. I found a strong area near 1/3 of lwl from the stern on my boat, and didn't even bother to check the % of lwl. It all works really well, despite my mediocre rudder.
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Old 04-03-2018, 01:18 PM   #125
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Very nice boat there, Simi !
Thanks

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What will the mast-system look like,
Because we have the height already the general consensus is a mast can be avoided and, it would seriously affect solar panel positioning and shading if we had one.

Should be able to get 45degree angle on the cable with what we have.

Quote:
and how does she roll - is she stiff or tender ?
Carvel hull so she rolls.
Saying that, not as bad as many we have been on.
Happy enough to punch into weather without them but get any beam swell happening and all bets are off.

In the past we have been able to change course and essentially tack towards destination to stop it, but if we are going to put some miles on her as we intend, she'll need something better than that.

As she is our full time live aboard house we are a very much wait for the right weather window type of cruiser so reality is she shouldn't be seeing anything to bad.
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Old 04-03-2018, 01:28 PM   #126
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For your consideration, close enough to 50% mark and position of arm if done in the front location
IMO, the forward location would offer a more effective location for the poles. The fish would drag back to just aft of amidship, which is acceptable. No need to worry about the fish flying out of the water if you have them deep enough and that the fish are angled/pointed downward. The amount of weight on front end of fish has some bearing here. I used to have my fish 4-5 fathoms below the surface. This may be too deep if you do a lot of shallow water anchoring, but then you could just shorten them up in those occasions only.
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Old 04-03-2018, 09:25 PM   #127
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Here is a very similar wood boat with the booms at the aft end of the house.
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Old 04-04-2018, 05:50 PM   #128
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I wonder why they put them so high?
If they ran them from the deck down the angles and loadings would be a lot better.
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Old 04-04-2018, 06:46 PM   #129
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Most Nordhavn’s mounted their paravanes from the boat deck. Loading must have been ok but I know you what you’re saying from looking at it.
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Old 04-04-2018, 09:53 PM   #130
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I wonder why they put them so high?
If they ran them from the deck down the angles and loadings would be a lot better.


The boat was originally a ‘head’ boat so would have 25 people on each side with their fishing poles hanging out hoping to hook something. Putting the paravane hardware in the second deck kept it out of the way of the great unwashed.
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Old 05-27-2018, 09:10 AM   #131
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Sea Venture Refit is Done - New video posted

For those interested, we have now finished our refit, which included a new superstructure and paravane system.

We are now headed to SE Alaska and Glacier Bay for the summer. We will return to Puget Sound in the fall and then in 2019 head south to Mexico and beyond.

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Old 05-27-2018, 09:38 AM   #132
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Thanks a bunch for posting that! It should be a game changer both for stability and heightened camera angles

If you don’t mind...how big were the backing plates in the pilothouse walls & roof relative to the outside mounting plates?
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Old 05-27-2018, 10:21 AM   #133
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Paravane Superstructure backing plates

The backing plates in the pilothouse are the same size as the exterior pads and are aluminum 3/8" plating.

For the stern feet of the superstructure they are much larger, since these feet take the majority of the load.

All the bolts are tapped through the fiberglass, which has a minimum thickness of 1/2 inch then backed with the aluminum plates and bolts.

The back plate bolts are 1" bolts on the exterior and 1/2" bolts on the interior side. The forward feet in the pilothouse are all 1/2" bolts.

The back feet are positioned directly over the salon wall where it intersects with a 2nd wall. 1/2 the bolts are on the outside of the house, and 1/2 the bolts go to the inside of the salon. The inside bolts are hidden.

Here is a picture of the rear feet exterior backing / chain plate.

I hope this helps. It's not a very good picture with the sun this morning, plus it came out sideways! I think it's shown in better detail in the video.

Jim
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Old 05-27-2018, 10:33 AM   #134
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Nice job! You did a great job on the tower. I hope you keep posting on your travels.
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Old 05-27-2018, 10:54 AM   #135
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Originally Posted by Cruising Sea Venture View Post
The backing plates in the pilothouse are the same size as the exterior pads and are aluminum 3/8" plating.

For the stern feet of the superstructure they are much larger, since these feet take the majority of the load.

All the bolts are tapped through the fiberglass, which has a minimum thickness of 1/2 inch then backed with the aluminum plates and bolts.

The back plate bolts are 1" bolts on the exterior and 1/2" bolts on the interior side. The forward feet in the pilothouse are all 1/2" bolts.

The back feet are positioned directly over the salon wall where it intersects with a 2nd wall. 1/2 the bolts are on the outside of the house, and 1/2 the bolts go to the inside of the salon. The inside bolts are hidden.

Here is a picture of the rear feet exterior backing / chain plate.

I hope this helps. It's not a very good picture with the sun this morning, plus it came out sideways! I think it's shown in better detail in the video.

Jim
Thanks
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Old 05-27-2018, 11:25 AM   #136
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Nice video. Really drives home the size and cost of the superstructure required for paravanes. Seems like the costs of paravanes, fins and gyros are not all that far apart in the end.

Be careful launching those fish in rough weather. Always good to deploy them before you need them.
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Old 05-27-2018, 06:50 PM   #137
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More videos to come

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Nice job! You did a great job on the tower. I hope you keep posting on your travels.
We will keep posting the videos. They are a fun hobby, and we have got to meet and connect with so many boaters it's been a real joy.

Thanks,
Jim and Rosy
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Old 05-27-2018, 06:53 PM   #138
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Paravane launching

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Originally Posted by gsholz View Post
Nice video. Really drives home the size and cost of the superstructure required for paravanes. Seems like the costs of paravanes, fins and gyros are not all that far apart in the end.

Be careful launching those fish in rough weather. Always good to deploy them before you need them.
Yes, we will follow the rule, if your thinking about it, deploy the fish, and once deployed, they stay out until calm.

I agree on the cost of the different systems. It's been ask about so much I'm working on a video that goes through how we selected paravanes vs. fins vs. gyro for stabilization.

Thanks,
Jim
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Old 02-28-2021, 09:52 AM   #139
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I know this thread is a few years old, but thought I'd use the opportunity to solicit opinions from the experts.

I'm toying with paravanes myself. The boat is an '80 Bristol 42, full displacement, round chines, twin. About 15 tons. She rolls.

I currently have a mast, but it is surely undersized for much more than a steady sail. I sketched up a rough idea of the kind of configuration I think would suit my particular dimensions. It is based on an a-frame set-up I have seen a few times in this thread. My primary concerns:

1. If I can transfer the force from the fish downward on the a-frame vice the mast (or at least a good portion of it), I wonder if I could keep my existing mast? The mast has a decent mounting plate (5x7"), and the mast itself is 3x5" solid wood.

2. The fore and aft stays for the mast.. Need to figure out how much load these need to carry. With the brace bars on the booms, I think not much.

Obviously, everything depends on the actual forces involved. This is just me thinking out loud. A loads analysis is obviously required before I can move much further along in the design.

General thoughts?

edit: (red indicates stowed configuration, blue/green is deployed)
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Old 02-28-2021, 11:22 AM   #140
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Personally I think you will need to upgrade your mast. On our boat, the mast is stepped all the way down to the cabin sole, with a steel framework distributing loads to the keel. From the pic of your mast step, I don't believe it will be up to the strain of paravanes. Your paravane system is just that, it needs to be a SYSTEM, with all parts designed to handle and disburse the considerable loads transmitted to the mast, from the paravanes. Probably not what you wish to hear, but I think you need to get a Marine Architect involved.
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