Reducing roll while anchored or moored.

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KaSeaTa and Mako, those are both very good ideas you noted. Still thinking about it, but I may try those.
 
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RickyD said:
The Stainless "butterfly" style is popular but I have not used them. The red "Hats" suck. Hard to stow and they flutter down to slowly. I just rebuilt my old ones. The company was small and now out of business. They are two steel frames with rubberized coating. The two screw together with heavy plastic panel sandwiched between. The plastic sheet is cut like an X corner to corner. The bottom frame has a steel lattice work to prevent the plastic from not presenting a flat surface when pulled up through the water. Then the X flaps open to allow the water to pass on the downward cycle. They work great and they don't make any noise in operation. I have two davits and suspend them off of. Rocker stoppers are said to work best when suspended from the same side with as much leverage as possible.
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Ricky - I have the same flopper stoppers and agree they work well (same ones Dashew shows in the link I posted earlier today). You mention you just rebuilt yours - mine have a crack in one of the plastic diaphrams. I assume you replaced this, what did you use?

Question for you: Are you saying that hanging two of the flopper stoppers on the same side works better than one on each (opposite) side? All other things being equal - same length of extension, etc.

Peter
 
markpierce said:
Seems like some don't like the feeling of being at sea.
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I love the feeling of being at sea.
But at anchor I like to be able to things like cook a meal, walk safely without holding on with both hands. At anchor, it is time to relax.

When the southerly wind is blowing and the anchorage has a westerly swell, some type of stabilisation is required to make my boat safe and comfortable.

Other boats may not need it if they stay in protected waters. I like to explore the coast of the Southern Ocean. It's not as benign as some other areas.
 
Marco Flamingo said:
I cheaped out and found Davis Rocker Stoppers for $10 each and free shipping. I'll see what 5 on each side does without any kind of extension boom. I may end up wearing them as hats.
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With 5 of them, I'd plan for about 15 lbs of weight on each string. Then see how they do. 4 per side with low stretch line makes a significant difference on my boat, although as mentioned earlier, they don't always drop fast enough on a big roll.
 
Ka_sea_ta said:
Could a person use the dingy crane and attach the Flop stopper to the winch cable and swing the crane outboard and lock the crane in place and lower the flop stopper to correct depth?
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Probably could, but you might want to consider several points:

  • Dingy crane may not be designed to take constant "tugging or jerking" that would result from using as a flopper stopper.
  • You won't get very much arm and resulting moment from dingy crane.
  • unless you added and extension, dingy winch drum may not hold enough cable to extend the depth you want the flopper stopper to be.
  • Dingy crane cables probably aren't designed for full submersion in salt water.
  • flopper stoppers (and paravanes) work best if they are attached to the boat at the midpoint (between bow and stern). Dingy cranes not on or near the midpoint will impart a torquing force on the hull, or rather to the point on the hull, or cabin roof, where they are attached . . . . May not be much, but . . .
 
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You could attach the device to the crane cable with rope, that way the cable will never get into saltwater, mine is dyneema or Spectra anyway. Our davit has a 10’ arm and would extend about 9’ from the side of the boat, it also is rated for 1500lbs. I doubt that any flopperstopper would put that much stress on the system even during a jerking situation.

I am going to keep my eyes open for one of these units over the winter and give it a try. I might even make one of my own...
 
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Woodland Hills said:
Our davit has a 10’ arm and would extend about 9’ from the side of the boat, it also is rated for 1500lbs. I doubt that any flopperstopper would put that much stress on the system even during a jerking situation.
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You may be surprised how much force is on the rigging. Depending on the size of the flopperstopper, it could be very close to your limit.
 
Well, 1500 lbs working load at a 10’ arm is 15,000 lbs working load at the standpipe. There is also a safety factor in case the tender is bounced by the boat rolling with it 1/2 deployed.
 
I used four per side of the Davis rocker stoppers off each midship cleat (w/ 15lb mushroom anchors) this summer in Catalina for two weeks. Verdict was mixed. I think they made a difference, but not a big one. I saw a guy anchored near me at White's with (I think) an Island Gypsy Europa in the 35-40' range that had a nice looking single-arm cantilever rocker stopper projecting maybe 6-8', and he seemed to be doing better than me. I might try to rig something up like that next year - intuitively that extra moment arm should be really effective.
 
Slowmo said:
The 'fins' you refer to were known as bilge keels (or bilge boards) and were commonly used on round bottom boats into the 1950's. If you look at old cruisers and yachts you'll often find them. I think they stopped being used for a few reasons. First was the move towards hard chine boats. The turbulence generated by a roll with a hard chine damps the roll more than a round bilge. Second, it is really hard to optimize a bilge keel to prevent it from causing a lot of drag. The problem is that the bilge keel should follow the direction of water flow around the boat. That's easy at the keel but fairly hard the further off center you go. also changes with speed. Third is that in the old days we didn't use travel lifts. Obviously a bilge keel would create a stress point in a sling.

The concept has been used more in sail boats in recent years, mainly in Europe, to allow them to stand up when they sit on the bottom with the extreme tides they can get. Of course these tend to be short and deep rather than shallow and long.

I really considered them for our old round bilged wood boat but rejected the idea for the reasons above. We did a keel extension, but still rolled our scuppers under in some conditions.
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There are "bilge keels" that look like stabilizing fins, and there are "rolling chocks" which are much longer and not as deep. The terms are often used interchangeably but that is confusing. Rolling chocks can be added to a SD chine hull with some good effect. I've done so on my boat. The roll extremes underway were reduced only a little (and were not big to begin with) but considerably lower roll accelerations and more dampening, well worth the modest cost. "It will take the snap out of the roll" is what the installer said, and he was right. At anchor the effect is noticeable, but less effective than underway. Comparing before and after (and having done extensive measurements in preparation for them), I can report that on my boat there is no difference in speed or fuel consumption at any rpm, nor any difference in maneuverability. The boat can be lifted in slings with no more care than before. They are not as effective as active fins or gyros, but also cost only a tiny fraction of those solutions and require no maintenance, power, or space at all.
 
socalrider said:
I used four per side of the Davis rocker stoppers off each midship cleat (w/ 15lb mushroom anchors) this summer in Catalina for two weeks. Verdict was mixed. I think they made a difference, but not a big one. I saw a guy anchored near me at White's with (I think) an Island Gypsy Europa in the 35-40' range that had a nice looking single-arm cantilever rocker stopper projecting maybe 6-8', and he seemed to be doing better than me. I might try to rig something up like that next year - intuitively that extra moment arm should be really effective.
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Next time you have yours deployed, stick your head over the side and watch the lines / cones. If the lines go slack on the down roll and don't go tight again until part way through the up-roll, then more weight or adding valves to the cones will make them more effective (by dropping them faster). Lower stretch lines help too, as the cones get moved further as the boat rolls (vs losing some distance to stretch). But if they're staying tight and the lines aren't too stretchy, then they're probably just not enough surface area to make a big difference without more leverage.
 
Anyone crossing FL this winter , I have 2 sets of para vanes , with poles for sale.


Contact me after 1 Nov to come see them.
 
Know they now make active fins that work even at anchor. But would think even old school fins when turned off would have some effect. You have 6’ to 10’ sq. ft. on both sides just sticking out there causing turbulence and drag on both edges. Also boat would roll out of synchrony to wave train. Would think that has to have some effect. ? Am I wrong?
 
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I have 9 square ft niaads and even if they do work somewhat while not moving, we still can roll pretty badly in the right wake. Thus my desire to experiment with the flipper stoppers.
 
SeaLion said:
These look interesting.

FlopStopper.com
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I have spent long time in open South Pacific rolling anchorages. I've tried almost any type available but the best result I had with the type SeaLion posted above. the other ones don't even come close to the performance of these.
 
We added the Forespar flopper stoppers. The standard length for the bigger pole at 14’ was too long to easily stow when not in use. We shortened them to 12’6” at the time of ordering and fitted the kit in an hour or so. Very robust and works. Like almost all systems you have work out how it best works for you and your boat but the system works well. Not the cheapest but definitely heavy duty.
Good luck!

KK 54
Ursa Major
 
I had a very simple set of "flopper stoppers" for almost 30 years:
The outer frame was ~ 3/4" angle iron 30" x 24". A wire rope bridle attached to the 30" sides. Inside were two pieces of steel sheet ~11 1/2" x 29 1/2", with the inner edge rolled over to give stiffness, and the outer edge attached to the 30" inner edge of the angle iron with Stainless steel hinges. Thus the two "leaves" opened in the center. The rolled over inner edge gave them stiffness. The steel had all been galvanized. They were made in S. Calif. in the 60's.

It was simple, I had to replace the wire bridle several times. and re-attatched the hinges (initially was pop riveted, then went to SS round head machine screws and nylox nuts.). It worked as well as the Magma "Rock n Roll". I used these on sailboats from 29' to 55' in length. Granted the sailboats had the advantage of spinnaker poles..

I have always wondered why someone didn't make these still. Fairly cheap, and as effective as the other "blade/ hinge" types.

I also tried the "Mexican Hats"--now by Davis. Not really effective.
 
thataway said:
I had a very simple set of "flopper stoppers" for almost 30 years:
The outer frame was ~ 3/4" angle iron 30" x 24". A wire rope bridle attached to the 30" sides. Inside were two pieces of steel sheet ~11 1/2" x 29 1/2", with the inner edge rolled over to give stiffness, and the outer edge attached to the 30" inner edge of the angle iron with Stainless steel hinges. Thus the two "leaves" opened in the center. The rolled over inner edge gave them stiffness. The steel had all been galvanized. They were made in S. Calif. in the 60's.

It was simple, I had to replace the wire bridle several times. and re-attatched the hinges (initially was pop riveted, then went to SS round head machine screws and nylox nuts.).

I have always wondered why someone didn't make these still. Fairly cheap, and as effective as the other "blade/ hinge" types.
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Hey Bob - these sound like the same design I have, which is same as Dashew shows at 18" x 24". He has 20-foot spinnaker poles to compensate for the smallish sized plates. Mine have a heavy plastic diaphragm vs the SS hinged gates.

I too am surprised they are no longer available. They work well, and are durable. Though I've never used the Magna device, it appears lightweight and the design takes a long time to 'close' on the upstroke. As you say, they are good when compared to the Mexican Hats, but that's about it. The telescoping poles are also a bit suspect in my eyes - made more for casual lunch-hook use that serious cruising.

The above said, there does not seem to be much demand for at-anchor stabilization. Many opinions, but very few who actually have them and use them with regularity.

Always good to see your posts.

Peter
 
mvweebles said:
Ricky - I have the same flopper stoppers and agree they work well (same ones Dashew shows in the link I posted earlier today). You mention you just rebuilt yours - mine have a crack in one of the plastic diaphrams. I assume you replaced this, what did you use?

Question for you: Are you saying that hanging two of the flopper stoppers on the same side works better than one on each (opposite) side? All other things being equal - same length of extension, etc.

Peter
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Peter, my old plastic was .059 thickness. I tried .060 Macrilon (sp?) It was too stiff. Then I tried .030 thickness vinyl. Too thin. I went back to the Macrilon and used my Dremel to cut more on both sides of the X like this IXI and also top and bottom, just leaving much smaller sections to hold it all together. So far it seems to be working well. Maybe not as good as the original. I will be testing them at anchor next week. I'll try to report back. I got the material from my canvas guy. They did have double laminated .030 vinyl. That would work great I believe but they couldn't find it when I needed it.

Yes, in reading about the Rock'r Stoppers they said both on the same side is better than one on each. It does make some sense to give more power resisting the up stroke.
 
RickyD said:
Peter, my old plastic was .059 thickness. I tried .060 Macrilon (sp?) It was too stiff. Then I tried .030 thickness vinyl. Too thin. I went back to the Macrilon and used my Dremel to cut more on both sides of the X like this IXI and also top and bottom, just leaving much smaller sections to hold it all together. So far it seems to be working well. Maybe not as good as the original. I will be testing them at anchor next week. I'll try to report back. I got the material from my canvas guy. They did have double laminated .030 vinyl. That would work great I believe but they couldn't find it when I needed it.

Yes, in reading about the Rock'r Stoppers they said both on the same side is better than one on each. It does make some sense to give more power resisting the up stroke.
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I just looked at the Dashew link and yes, those are exactly what I have. I met the guy who made them down in San Diego. He said he retired but probably could make me one more unit, which he did. I can't find him today. I had to drill out the rivets for SS machine screws. I had to cut the harness so I made my own from Dyneema 1/8" cable. It took a long time to make and whip all of the loops for my two units.
 
Just got back from the visiting my boat and taking my Davis "mexican hats" for a test run. Of course, I had to try a modification. It looked like the down stroke would be the weakness of these flopper stoppers. The modification was to drill "pressure relief holes" in the pointy area on the hat on half of them. So I drilled four 3/8" holes about 3 inches down from the top. The other 5 I left alone.

I put both strings on the same side of the boat and started rocking it. The ones without holes kited sideways quite a bit and were not fully at the bottom of the stroke before that side of the boat started to lift again. The ones with holes sunk down straighter and engaged faster when that side of the boat started to rise. In fact, they snugged up so much faster than the un-modified flopper stoppers that the un-modified had a hard time fully engaging on the rise. It appeared that my modification worked.

It seems like adding more vent holes (designed like a reed valve used on other flopper stoppers) on the "brim" of the hat might make them drop even faster. Something like several 1 inch holes covered by a 3 inch round flap of vinyl coated polyester material.

Dropping fast because of lower resistance on the decent also requires less weight on the end of the line. I'm trying to get the most stabilization in the smallest and lightest weight possible. No room on my pocket trawler for hurkey flopper stoppers.
 
makobuilders said:
Thataway do you have any photos?
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I am sorry, those were sold with a boat in the 1989 era. I tried to find photos on the internet, but not successful.. I believe the corners of the 3/4" angle iron was mitered on the bottom at 45* each piece, and then bent and tack welded. This gave a 3/4" lip around the edge which the sheet metal plates stopped against. Kelp can get caught in these (as well as the Magma). My impression was that the steel "flaps" opened faster and the unit sunk faster than the cut plastic flaps.

Peter, mine were considerably larger, and had the steel "flaps". Of course SS would be ideal.

One problem (I found out the hard way) is that you can cut or get a finger caught with the Magma, which we used on our Cal 46. I agree that the plate in a frame seemed to work slightly better than the Magma.
 
I'll try to remember to pull out the drill and pop a couple holes like Marco described in my orange cones. Might be enough without having to resort to holes and flaps on the bottom portion.
 
mvweebles said:
I wouldn't say the displacement boat rolls more or less, but they do roll differently. FD hulls are quick to roll the first 5-degrees or so until whatever ballast is present offsets. A SD hull has form-stability that resists the first 5-degrees, but does not have the added leverage. SD hulls are often characterized as having a 'snappy' roll.

My Willard 36 (39-hulls built between 1961 and 1970) came off Wm Garden's drafting board in the 1950's with very slack bilges - Willard's Naval Architect Rod Swift filled-out the bilges for the 1974 introduction of the Willard 40. The deckhouse on the W40 is also higher to gain more accommodation so the A/B ratio is higher, similar to a KK42 or N40. My guess is the Willard 36 may be the roundest-bottom production trawler out there. However, Garden designed-in a full keel, and she carries 6000-lbs of her 25,000-lb displacement as ballast - almost 25% (for comparison, KK 42 and N40 are under 10%). As expected, my W36 is tender to 5-degrees or so, then gets pretty dang stable.

I can tell you from many miles of running with long swells in the Pacific, it's a nice ride to swing 10-15 degrees on a heavy-ballast FD hull. A friend calls it akin to an old Buick Roadmaster going down a country road.

Peter
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As my old man used to say on this topic of paravanes ( career Navy class of 41) , “ roll, roll you SOB! The more you roll the less you’ll pitch”. I think he was on old destroyers at the time he heard it first. I’d imagine they werepretty snappy esp if they were trying to get somewhere.

At an anchorage anything that resits the water will work and the further off the boat the better. A 5 gallon bucket tied off amidships cleat is a good start. I use the flipper stopper plate described above tied off off my boom on my 32 trawler.
 
Codger2 said:
No, not interested in debating someone who thinks his experience is the only experience! :blush:
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I just don’t like the idea of the gyro running at such high rpms and consuming energy. Seems to defeat the purpose of anchoring out. Boats roll.
 
Does anyone on the Forum have experience with using a Magnus stabilizer at anchor? There are several manufacturers of Magnus stabilizers, but I haven't been able to find their power consumption. I'm curious how their power consumption compares to the gyros.
 
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