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Old 08-09-2010, 08:44 PM
  #21    
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Originally Posted by mishari84 View Post
what i found on older posts are the catamarans are worse than v hull boats at anchor, and deep v hulls are bad in anchor also, this why im thinkin of the stabilizers
Anchor your cat off a corner cleat instead of center of the bow, this will make it very stable.
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Old 08-09-2010, 09:18 PM
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didnt see hard chines mentioned yet
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Old 08-09-2010, 10:23 PM
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Originally Posted by mishari84 View Post
hello

what do you think about these boat stabilizers ? any experience with them ?

http://www.boatstabilizers.net/customer-cments.html

and also this

http://www.magmaproducts.com/Product...tabilizer.html
The sail boys use those a lot, do a search for "flopper stoppers"
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Old 08-10-2010, 06:23 AM
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Beam, Beam, Beam...

This is the most important factor in stability at rest. The wider it is, the more stable it is.

Second is deadrise. this affects a boat much less at rest, but much more at drift or on troll in a beam sea. Flatter deadrise=more stability. If your fishing is nearshore and not typically ocean rough, then something with a small degree of deadrise shoudl work fine. If it is more ocean conditions, then an increase in deadrise may be needed. If you can increase the beam while increasing the deadrise, you may get the best of both worlds for your application.

Cat vs mnohull at anchor is a function of a cat not having the available bouancy that a monohull has due to the area of the hull that is absent in the bow. That area not being in the water causes a cat to dip lower into the water before the lesser bouancy of the twin hulls reacts and causes the hull to recover and push up out of the wave. This is why many cats are noticeable "wetter" running into a head sea. The way designers have overcome this is by increasing the freeboard forward making it less likely to take waves over the bow.
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Old 08-10-2010, 06:23 AM
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We're confusing a couple of different terms here, so a bit of clarification is needed. You don't want to confuse stability with initial stability. First, assume "all other things being equal". When talking about the effect of deadrise, dont' compare a 24 degree 33 foot boat with a 17 degree 18 foot boat.

If you have 2 boats with the same length, beam, and weight, the one with greater deadrise will roll easier and feel more tender. Less beam or softer chines will have the same effect, as will teh concentration of weight towards the centerline of the boat. These are all examples of less initial stability. An easy way to feel it is while standing on a pier - put one foot on the boat and you can easily push it down.

The other side would be high initial stability. An example would be a catamaran. High initial stability means the boat's horizontal plane wants to stay parallel with the water plane.

Here's the rub. Higher initial stability doesn't mean better stability overall, and this is something that TAR hinted on earlier. Let's say my boat is really flat (high initial stability like a cat) and your is very tippy, like a long, narrow, high deadrise boat. At the dock, I can easily rock your boat with my hand on the gunwhale. Now we both go out fishing, and while at drift, we both encounter beam seas, rolling our boats from side to side.

When the wave first reaches the starboard side of the boat, each boat will lean to port. My boat has a lot of initial stability, and will immediately snap to a 30 degree angle to match the water plane. Your, being tippy, isn't as influenced by the change in the angle of the water plane, so yours slowly tilts the same way, but only makes it to 25 degrees and then the wave is already under the boat and we're now leaning back the other way. After the wave is gone, the rolling is quickly attenuated in my boat (second roll is maybe 10 degrees) but your boat rolls 2 or 3 more times.

So who's boat is more stable? Mine rolls less times, and the rolls after the wave degrade faster, but the max angle is actually more and the rolling happens faster than yours. In theory, your boat can withstand a bigger wave before it capsizes compared to mine.

What you want to change isn't the stability but the righting moment. If you move both of our boats by putting your foot on the gunwhale and then let go, the one that snaps back to level quickly has a shorter righting moment. If you increase the righting moment, ie slow it down, this will make it roll slower. Moving weight AWAY from the centerline or using flopper stoppers should have this effect.

You can also use a drogue or small sea anchor to change the direction your boat is facing while drifting so you don't drift beam to. Hope this helps!
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Old 08-10-2010, 05:09 PM
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Wide beam + moderate deadrise + Length + Low center of Gravity = STABLE
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Old 08-10-2010, 05:29 PM
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MY mako is not a deep v boat and is pretty stable drifting or anchored. Can have 3 dudes standing on one side and not much list. You do get beat up more in the slop. So i would say that less dead rise is more stabil but not that good in bad seas.
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Old 08-10-2010, 06:32 PM
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Originally Posted by cooterscrazy View Post
MY mako is not a deep v boat and is pretty stable drifting or anchored. Can have 3 dudes standing on one side and not much list. You do get beat up more in the slop. So i would say that less dead rise is more stabil but not that good in bad seas.
i was thinking either to go for deep vee for better ride and correct anchor stability by boat stabilizers, have flatter transom with less than moderate quality ride and moderate anchor stability, or going with catamarans as suggested above
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Old 08-10-2010, 06:44 PM
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Originally Posted by jobowker View Post
We're confusing a couple of different terms here, so a bit of clarification is needed. You don't want to confuse stability with initial stability. First, assume "all other things being equal". When talking about the effect of deadrise, dont' compare a 24 degree 33 foot boat with a 17 degree 18 foot boat.

If you have 2 boats with the same length, beam, and weight, the one with greater deadrise will roll easier and feel more tender. Less beam or softer chines will have the same effect, as will teh concentration of weight towards the centerline of the boat. These are all examples of less initial stability. An easy way to feel it is while standing on a pier - put one foot on the boat and you can easily push it down.

The other side would be high initial stability. An example would be a catamaran. High initial stability means the boat's horizontal plane wants to stay parallel with the water plane.

Here's the rub. Higher initial stability doesn't mean better stability overall, and this is something that TAR hinted on earlier. Let's say my boat is really flat (high initial stability like a cat) and your is very tippy, like a long, narrow, high deadrise boat. At the dock, I can easily rock your boat with my hand on the gunwhale. Now we both go out fishing, and while at drift, we both encounter beam seas, rolling our boats from side to side.

When the wave first reaches the starboard side of the boat, each boat will lean to port. My boat has a lot of initial stability, and will immediately snap to a 30 degree angle to match the water plane. Your, being tippy, isn't as influenced by the change in the angle of the water plane, so yours slowly tilts the same way, but only makes it to 25 degrees and then the wave is already under the boat and we're now leaning back the other way. After the wave is gone, the rolling is quickly attenuated in my boat (second roll is maybe 10 degrees) but your boat rolls 2 or 3 more times.

So who's boat is more stable? Mine rolls less times, and the rolls after the wave degrade faster, but the max angle is actually more and the rolling happens faster than yours. In theory, your boat can withstand a bigger wave before it capsizes compared to mine.

What you want to change isn't the stability but the righting moment. If you move both of our boats by putting your foot on the gunwhale and then let go, the one that snaps back to level quickly has a shorter righting moment. If you increase the righting moment, ie slow it down, this will make it roll slower. Moving weight AWAY from the centerline or using flopper stoppers should have this effect.

You can also use a drogue or small sea anchor to change the direction your boat is facing while drifting so you don't drift beam to. Hope this helps!
Man that was one of the best explanations of something I may have ever read!
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Old 08-10-2010, 07:06 PM
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Originally Posted by mishari84 View Post
hello

what do you think about these boat stabilizers ? any experience with them ?

http://www.boatstabilizers.net/customer-cments.html

and also this

http://www.magmaproducts.com/Product...tabilizer.html
Those use the same concept as outriggers and birds on a commercial vessel like a dragger/scalloper/clammer. We call them sissy arms up here. I can tell you that the full-blown commercial grade ones work unbelievably well. Never spill your coffee with them.

To the OP, the ideal boat you'd like is a downeast style hull with a full keel.
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Old 08-10-2010, 09:29 PM
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Quote:
Originally Posted by jobowker View Post
We're confusing a couple of different terms here, so a bit of clarification is needed. You don't want to confuse stability with initial stability. First, assume "all other things being equal". When talking about the effect of deadrise, dont' compare a 24 degree 33 foot boat with a 17 degree 18 foot boat.

If you have 2 boats with the same length, beam, and weight, the one with greater deadrise will roll easier and feel more tender. Less beam or softer chines will have the same effect, as will teh concentration of weight towards the centerline of the boat. These are all examples of less initial stability. An easy way to feel it is while standing on a pier - put one foot on the boat and you can easily push it down.

The other side would be high initial stability. An example would be a catamaran. High initial stability means the boat's horizontal plane wants to stay parallel with the water plane.

Here's the rub. Higher initial stability doesn't mean better stability overall, and this is something that TAR hinted on earlier. Let's say my boat is really flat (high initial stability like a cat) and your is very tippy, like a long, narrow, high deadrise boat. At the dock, I can easily rock your boat with my hand on the gunwhale. Now we both go out fishing, and while at drift, we both encounter beam seas, rolling our boats from side to side.

When the wave first reaches the starboard side of the boat, each boat will lean to port. My boat has a lot of initial stability, and will immediately snap to a 30 degree angle to match the water plane. Your, being tippy, isn't as influenced by the change in the angle of the water plane, so yours slowly tilts the same way, but only makes it to 25 degrees and then the wave is already under the boat and we're now leaning back the other way. After the wave is gone, the rolling is quickly attenuated in my boat (second roll is maybe 10 degrees) but your boat rolls 2 or 3 more times.

So who's boat is more stable? Mine rolls less times, and the rolls after the wave degrade faster, but the max angle is actually more and the rolling happens faster than yours. In theory, your boat can withstand a bigger wave before it capsizes compared to mine.

What you want to change isn't the stability but the righting moment. If you move both of our boats by putting your foot on the gunwhale and then let go, the one that snaps back to level quickly has a shorter righting moment. If you increase the righting moment, ie slow it down, this will make it roll slower. Moving weight AWAY from the centerline or using flopper stoppers should have this effect.

You can also use a drogue or small sea anchor to change the direction your boat is facing while drifting so you don't drift beam to. Hope this helps!
after i read many times i found your reply to answer everything regarding initial boat stability including transom deadrise effect , boat stabilizers action mechanism , beam much more

so a boat with flat transom and wider beam will have much more initial stability compared to deep v hulls according to your explanation

1 issue need to be more explained is sea anchor method , can you explain more please
because i only have seen pics of sea anchor in the internet, never tried before
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Old 08-11-2010, 05:55 AM
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A wider beam is more stable, but will also contribute to a rougher ride and a less-efficient hull. The ideal ticket is to stick with your narrow beam for a nice ride out to the fishing grounds, then deploy an outrigger to gain your stability at rest. Outrigger = extra wide beam without the poor ride and poor efficiency of the wide beam.

Add a drift sock to the rig to help control your drift. If the boat is still too unstable, then add one of the vertical stabilizers as advertised in the links above.

Also, keep your eyes on the horizon. If you look down too much while fishing in the waves, you will get seasick!
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Old 08-11-2010, 06:08 AM
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A sea anchor deployed from the bow creates drag in the water which will keep the nose of the boat into the wind. the result is that you drift facing into the wind so you do not get the side to side roll of drifting abeam of the waves.
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Old 08-11-2010, 06:32 AM
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i'm mostly guessing at your situation but sound like you need a design with positive bouyancy and a low center of gravity in respect to center of bouyance- this will reduce some motion at rest and reaction to the occupants moving around. bay boats and jon boats demonstrate these qualities but may be less forgiving to other conditions you're encountering.
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Old 08-11-2010, 06:56 AM
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Glad I could help! Even a blind squirrel finds an acorn now and then...
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Old 08-08-2013, 11:23 PM
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Default boat stabilisers

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Originally Posted by UaVaj View Post
Rock n Roll Boat Stabilizer and Ocean Torque

fugly, fugly, fugly - unless you are shrimping.
Ocean Torque don't make stabilisers for Shrimp boats, they are for Anchored or Adrift, only. The video is worth a look the whole site for that matter 'OceanTorque'.com.
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Old 08-09-2013, 02:17 AM
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You need a Seakeeper gyro stabilizer!

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Old 08-09-2013, 04:11 AM
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Show me a stable boat at rest and I'll show you some flat seas underneath it. My last 3 boats: 15 degree, 20 degree, and now 24 degree deadrise. They all rocked and rolled when the support beneath them was rocking and rolling.
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Old 08-09-2013, 05:37 AM
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Chines and lifting pad design turn an otherwise unstable inefficient hull into one that is efficient, relatively stable and still a wave crusher at speed. My cc has 3.5:1 length to beam ratio and is surlrisingly stable yet still screws in the rough stuff and at 35' averaging just under 1.4 mpg canyon loaded is pretty darn efficient. Thats with gen 1 vrods.
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Old 08-09-2013, 07:58 AM
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Show me a stable boat at rest and I'll show you some flat seas underneath it. My last 3 boats: 15 degree, 20 degree, and now 24 degree deadrise. They all rocked and rolled when the support beneath them was rocking and rolling.
I tried to post a picture of a cruise ship but every one of the pictures the boat is still.


as I posted on page 1 years ago

little more dramatic view
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