Flopper stoppers

[Simi 60]

It’s my guess that the line stretch is working against you. On the fishing boats we always used steel cable. If the line is allowed to stretch, the roll is allowed to build momentum, and the flopper is delayed.

No guessing about it and why I have changed to Dyneema as stated.

 

[Simi 60]

Well, been anchored back where high speed ferries usually roll us every half hour
Dyneema from roof to arm
Nylon double braid from arm to Magma clone on steroids

Rolled for the first 2 ferry though as a benchmark then deployed the "clones"
Roll on the next dozen ferries ranges from roll not noticeable to a 50% reduction which is ok.
Big boil on the surface noticed like Brian mentioned and ours are set about 8 ft or 2.5 m down.

Calling that a win for today
My work is done.

 

[Bmarler]

No guessing about it and why I have changed to Dyneema as stated.

thought you said there was still nylon to the flopper. but hey, as long as you're happy with it, that's all that matters.

 

[Simi 60]

thought you said there was still nylon to the flopper. but hey, as long as you're happy with it, that's all that matters.

Long nylon arm to roof is now dyneema
Short nylon arm to flopper
But no more dyneema on board long enough to replace the short nylon if I wanted to.
And as we are out here full time, no shops nearby to buy more.

 

[willd]

Hi All,

I'm on a 60ft houseboat, with three decks, and a fully equipped kitchen on the top deck (so we are heavy, and top heavy). We're moored permanently in a typhoon shelter. We don't get big waves, but we get enough of a rock from wind and/or passing boats to make my wife seasick sometimes. As such, I'm looking to deploy some flopper stoppers. Unlike most, mine will be in the water permanently, so don't need to be packable or light. Our waves are also not huge. Extension arms are not an option, with boats parked on either side. Given our size, I think I may need to attach quite a few on both sides (I have 5 cleats on each side, so doable).

What do you guys suggest? I want something that is going to drop fast enough, which suggests flaps. I've considered Magma or FlopStopper. But given how many I probably need (and being based in HK) I'm thinking it might be much cheaper to do DIY. I've considered a DIY version like what was suggested by Simi 60 or the yellow one discussed by mvweebles.

However, given mine will be in the water permanently (and thus get barnacle growth) I'm thinking a lack of moving parts would make maintenance easier. Also, I don't care about weight. As such, I'm considering either just large steel disks on a chain, with extra chain below for weight. But that might not dive so well? The other idea is an upside down bowl (like the Australia-made round ones, but I'd probably do steel or aluminum) or upside down cone (pointy end down). I assume that making the item hyrdrodynamic downward, but purposely not so upward, would be better than a simple disk--correct?

Anyway, thoughts most welcome. Thanks all (from me and my seasick wife).

Will

 

[mvweebles]

Hi All,

I'm on a 60ft houseboat, with three decks, and a fully equipped kitchen on the top deck (so we are heavy, and top heavy). We're moored permanently in a typhoon shelter. We don't get big waves, but we get enough of a rock from wind and/or passing boats to make my wife seasick sometimes. As such, I'm looking to deploy some flopper stoppers. Unlike most, mine will be in the water permanently, so don't need to be packable or light. Our waves are also not huge. Extension arms are not an option, with boats parked on either side. Given our size, I think I may need to attach quite a few on both sides (I have 5 cleats on each side, so doable).

What do you guys suggest? I want something that is going to drop fast enough, which suggests flaps. I've considered Magma or FlopStopper. But given how many I probably need (and being based in HK) I'm thinking it might be much cheaper to do DIY. I've considered a DIY version like what was suggested by Simi 60 or the yellow one discussed by mvweebles.

However, given mine will be in the water permanently (and thus get barnacle growth) I'm thinking a lack of moving parts would make maintenance easier. Also, I don't care about weight. As such, I'm considering either just large steel disks on a chain, with extra chain below for weight. But that might not dive so well? The other idea is an upside down bowl (like the Australia-made round ones, but I'd probably do steel or aluminum) or upside down cone (pointy end down). I assume that making the item hyrdrodynamic downward, but purposely not so upward, would be better than a simple disk--correct?

Anyway, thoughts most welcome. Thanks all (from me and my seasick wife).

Will

A picture of your boat and mooring situation might help.

I am generally skeptical that anything hanging over the gunwales will do much. Simply not enough leverage. I am also skeptical of any device that doesnt have a mechanism of some sort to maximize ascent/descent. Davis Instruments used to make "Mexican Hats" that they advertised could be used like that. Best I can tell is they provide slight attenuation but that's it and even s modest sized sailboat required many of them. Steve Dashew initially used devices identical to my yellow ones, but them used the Magma ones and found they worked better. The yellow "diaphragm" design could be DIY using a frame of angle iron holding a grid of perforated metal ("expanded metal" is what it's called in US - often seen on industrial catwalks) with some sort of heavy diaphragm material that hinges.

Given you are permanently moored, maybe some other means. This is where a picture might be helpful. First idea would be what are locally called "spuds," posts down to the seabed used on small work barges. Depends on how tidal your area is.

Another idea, depending on how close your neighbors are, is some sort of flotation - an ama outboard. If you have even a bit of space between you and your neighbor, a rigid frame attached to your boat that holds an empty 55 gallon drum or two to essentially widens your beam and provides greater form-stability.

Peter

 

[willd]

A picture of your boat and mooring situation might help.

I am generally skeptical that anything hanging over the gunwales will do much. Simply not enough leverage. I am also skeptical of any device that doesnt have a mechanism of some sort to maximize ascent/descent. Davis Instruments used to make "Mexican Hats" that they advertised could be used like that. Best I can tell is they provide slight attenuation but that's it and even s modest sized sailboat required many of them. Steve Dashew initially used devices identical to my yellow ones, but them used the Magma ones and found they worked better. The yellow "diaphragm" design could be DIY using a frame of angle iron holding a grid of perforated metal ("expanded metal" is what it's called in US - often seen on industrial catwalks) with some sort of heavy diaphragm material that hinges.

Given you are permanently moored, maybe some other means. This is where a picture might be helpful. First idea would be what are locally called "spuds," posts down to the seabed used on small work barges. Depends on how tidal your area is.

Another idea, depending on how close your neighbors are, is some sort of flotation - an ama outboard. If you have even a bit of space between you and your neighbor, a rigid frame attached to your boat that holds an empty 55 gallon drum or two to essentially widens your beam and provides greater form-stability.

Peter

Thanks Peter.

I’m too packed in to do much out the sides, and I’m sure I’d violate some regulation if I built outward much. I’m tied up alongside one boat, and the boat on the other side seats but is usually about 10feet away. Building arms outward is just not an option. My beam is 6.4m/21ft.

We do get about 10feet or so tides so I don’t think posts to the sea floor work. It’s also 40ft deep. The boat also sways side to side some.

My dad did have the idea of attaching rigid poles on the side and putting some sort of Flopper stopper at the bottom. That way it works in both directions, unlike one on a rope or chain. But that sounds expensive and I worry about the stresses on the hull.

 

[KnotYet]

In your situation a flume tank or tanks might be the best option.
On your large craft, space for them should not be too much of a
problem and they could be PVC pipes.
There is a lot of info about them, you can start reading here:
https://en.wikipedia.org/wiki/Antiroll_tanks

 

[willd]

In your situation a flume tank or tanks might be the best option.
On your large craft, space for them should not be too much of a
problem and they could be PVC pipes.
There is a lot of info about them, you can start reading here:
https://en.wikipedia.org/wiki/Antiroll_tanks

Thanks KnotYet,

My initial concerns about these antiroll tanks are (1) expense, (2) they address roll but not pitch, and, most importantly, (3) it seems you have to get the design and water levels just right for your boat or else it could not only be ineffective but potentially counter-productive.

Some form of flopper stopper in all four corners of the boat would seem better on all 3 fronts?

Will

 

[willd]

So my improved Magma type flopper stoppers arrived yesterday
Bigger boat than magma recommended so scaled it up in size
Used 3mm 316 stainless plate
1/2 links of s/s chain welded on for attachments
Large robust 316 hinges welded on
And spent a few hours splicing the 6mm blue dyneema ropes.

The rope attaching it to the arms and arms to roof is double braid nylon, learned a new skill splicing that lot as well.

Simi 60,

Have you been happy with your scaled-up Magma? If so, would you be willing to share the blueprints?

I've also considered just getting the regular size magma's off the shelf and get lots of them (at least 4, and as many as 10--since I'm big and have to simply attach to my cleats). But given that most people say they still need to be upgraded (making the hinges stronger, adding weight, etc...) maybe it is best just to go custom from the start.

Will

Will

 

[willd]

We recently installed the round australian ones (https://www.boatstabilisersaustralia.com/products/) Expensive but very well made. Have used them about 20 times on our trip from Hervey Bay to Townsville and they definitely work well. Hard to quantify but subjectively at least 75% reduction in roll in most situations. We had them installed on 3 meter poles (stored lying horizontal along the rub rail). Takes some practice to deploy but not hard once you've done it a few times.

Robert,

Do you still like these?

One of my top candidates for my problem (big boat at mooring that basically never moves and must hang flopper stoppers off the cleats as no room to extend outrigger) is to have custom made versions of these Austrialian Ocean Torque "round bowl" stabilizers. I'm thinking of going with the largest size (~1m diameter) and building the entire thing out of metal (as weight and storage is not an issue for me).

I originally thought I'd just have a shallow bowl (similar to the Ocean Torque stabilizers--see pic below), with a ring welded on in the middle of the bowl on the top (for attaching the suspension line) and a ring on the bottom (for attaching a weight chain). But I note the Australia ones have a rigid pole on the bottom, to which is connected a chain. Do you know if that rigid part is needed or could I just attach a chain directly to the bottom?

I also thought about daisy chaining them. You basically just attach other one to the bottom of the weight chain (with it's own weight chain below that).That saves on suspension line, and it allows me to conentrate the pull at the extreme ends of the boat fore and aft. However, I wonder if this is too much stress on the cleat. Given I have 5 cleats on each side of the boat, I could just add single units to more cleats.

Anwyay, thoughts welcome. As should be clear in my recent posts, I have not yet decided the best route to take.

Will

 

[rpackard]

I used the magmas deployed off the poles that serve with paravanes when underway. The magma comes with a line to keep them from spinning. You need some stretch in the line going down or else the boat give ab ig jerk each time they open. You will not get a good night's sleep in that case. I used a very heavy section (about 12") of of bungy cord. They were a nuisance to bring down from the top deck and deploy, especially if I waited until the boat was rolling heavily. And I had to be careful to have a piece of carpeting to rest them on in the cockpit to keep from damaging the fiberglass. I did not need any extra weight.

 

[willd]

I used the magmas deployed off the poles that serve with paravanes when underway. The magma comes with a line to keep them from spinning. You need some stretch in the line going down or else the boat give ab ig jerk each time they open. You will not get a good night's sleep in that case. I used a very heavy section (about 12") of of bungy cord. They were a nuisance to bring down from the top deck and deploy, especially if I waited until the boat was rolling heavily. And I had to be careful to have a piece of carpeting to rest them on in the cockpit to keep from damaging the fiberglass. I did not need any extra weight.

You also used the Australian round ones right? Did they not work as well as the magmas?

Re your point about jerking, note that others on this chat have suggested solving that with weight and non-stretch lines (the opposite of the direction you took).

Will

 

[rpackard]

I only used the magmas.

Use low stretch line like dyneema and let me know how you slept. Maybe on a hull that does not roll much you could use low stretch, but why would you use stopper floppers on such a hull?

 

[rpackard]

Keep in mind that because of the construction of the magmas the boat will have rolled a few degrees before the vanes open. Then you come to a jerking halt. there is another design available using multiple smaller vanes that would open at a smaller roll and would have less jerk.

 

[willd]

Keep in mind that because of the construction of the magmas the boat will have rolled a few degrees before the vanes open. Then you come to a jerking halt. there is another design available using multiple smaller vanes that would open at a smaller roll and would have less jerk.

I assume you are talking about the flopstopper?

 

[willd]

I only used the magmas.

Use low stretch line like dyneema and let me know how you slept. Maybe on a hull that does not roll much you could use low stretch, but why would you use stopper floppers on such a hull?

Sorry, I got you mixed up with RobertLeatch, who used the Aussie round ones.

 

[mvweebles]

I am aware of three designs. The plastic diaphragm design I have, the Magma hinged design (Forespar makes a similar model at 2x the cost, but is a bit bigger), and the multi-shutter design of the Flopstopper. Steve Dashew noted the Magma engaged much more quickly than the diaphragm design and subsequently swapped out his diaphragm plates for Magma. The shutter design would likely be quicker still, but for me, not worth the significant cost uptick. They appear to be easily disassembled and stored, a nice feature.

I agree with Rpackard that some elasticity in the rigging is needed, at least for a traditional setup with significant boom lengths. For hanging off the gunwale, elasticity would not be necessary, and would likely be a negative feature.

There is one aspect that has not been discussed - roll attenuation, or reduce the roll-momentum when a series of waves comes through (Rpackard may have the right word). This is where I think gunwale hung stabilizers might help - they wouldn't help with initial roll, but might dampen the duration and amplitude of the overall event.

For the HK houseboat poster, since these will be a near permanent fixture, suggest the plates are small enough to be easily hauled for monthly cleaning. A power washer will be your friend.

Peter

 

[willd]

I am aware of three designs. The plastic diaphragm design I have, the Magma hinged design (Forespar makes a similar model at 2x the cost, but is a bit bigger), and the multi-shutter design of the Flopstopper. Steve Dashew noted the Magma engaged much more quickly than the diaphragm design and subsequently swapped out his diaphragm plates for Magma. The shutter design would likely be quicker still, but for me, not worth the significant cost uptick. They appear to be easily disassembled and stored, a nice feature.

I agree with Rpackard that some elasticity in the rigging is needed, at least for a traditional setup with significant boom lengths. For hanging off the gunwale, elasticity would not be necessary, and would likely be a negative feature.

There is one aspect that has not been discussed - roll attenuation, or reduce the roll-momentum when a series of waves comes through (Rpackard may have the right word). This is where I think gunwale hung stabilizers might help - they wouldn't help with initial roll, but might dampen the duration and amplitude of the overall event.

For the HK houseboat poster, since these will be a near permanent fixture, suggest the plates are small enough to be easily hauled for monthly cleaning. A power washer will be your friend.

Peter

Thanks Peter. Very helpful.

I take the point about making them small enough to lift and clean. Though, one appealing aspect of the Australian round bowl design is that there are no moving parts, and I suspect a rusted and barnacle covered bowl (3feet in diameter and 6-10feet under water with a chain weight hanging below) would probably work nearly as well as a clean shiny one? Maybe slightly less hydrodynamic downward but enough to matter?

Will

 

[mvweebles]

Thinking about it, your boat probably has a really slow roll period which gives whatever device you use plenty of time to descend. Also, doesn't need to be round, and doesn't need to be stowable. Three factors working in your favor.

I'd be tempted to mock-up something to see if it works. Maybe a couple pieces 18mm plywood, 1m square with a 10cm rim around it to create a barrier to water just sliding off. To weigh it down and offset bouancy of wood, suspend a decent sized dinghy anchor with the rode passed through a hole in the center. Tether to boat would be a 4-point bridle attached to the corners of the plate. It wouldn't last long, maybe a month or so if you painted it well, but would be easy and inexpensive to build so you'd know what you might need in a final metal fabrication.

Without outrigger booms, best you can hope for is some mild dampening to prevent sustained pendulum oscillation.

Peter

 

[KnotYet]

Thanks KnotYet,

My initial concerns about these antiroll tanks are (1) expense, (2) they address roll but not pitch, and, most importantly, (3) it seems you have to get the design and water levels just right for your boat or else it could not only be ineffective but potentially counter-productive.

Some form of flopper stopper in all four corners of the boat would seem better on all 3 fronts?

Will

(1) Expense: You are contemplating buying between 4 and 10 Magma units.
In the U.S. the big ones cost $350 each for a total of $1400-$3500.
I can only guess what they cost in Hong Kong. PVC should be less.

(2) Pitch: While a tank would work as well as floppers if arranged fore and
aft, floppers might be more practical at bow and stern if they actually work.

(3) Design: Gunnel-hung flopper stoppers may work if you use enough of
them. You won't know until you buy them and try them. They will also need
periodic cleaning. Flume tanks are well understood and could be DIY.
Obviously that depends on your level of ability and desire to do so.

 

[Xlantic]

Based on my experience using a boom is essential. I tried my two 35cm x 100cm stabilisers directly on the gunnel and they didn't do much. I now use two 6 metre booms. The booms multiply the vertical motion of the stabilisers by a factor of more than 3X, in my case, giving them more time to sink. They also multiply the righting force on the boat by the same factor.

The design below is not the one I use but is probably cheap to make, has no moving parts and should not be too impaired by barnacles. Maybe you can build these large enough and use enough for it to work in your situation.

 

[willd]

Dear all,

I finally got around to ordering five custom flopper stoppers for my 60ft house boat (2 going on the stern, 2 mid way up before the hull narrows, and 1 off the bow). They will be tied to (sturdy) cleats. No room for booms where I'm parked. They will be upside down steel pyramids with an open "base" at the top 1 meter squared.

The only thing left to decide is what to hang them with. I intend to create a bridle of chain connecting the four pounts of the inverted pyramid. Then I will run something 10-12 feet up to the boat. But what? Some have expressed strong opinions it should be something without any stretch, while others insist some stretch is necessary. I will leave them permanently in the water. I don't want jerk, but I also don't want the line to stretch so much it doesn't have the desired effect. My hope is that my heavy upside down pyramid (60 degree angles so it is quite pointy downward) will sink rather quickly, but we'll see. Should I use chain, cable, dyneema, polyester, polypropylene, or nylon?

I appreciate the views already expressed here, but some are completely opposed. Now that I've got a design, does anyone have a clearer view on what material I should use for the line up to the cleats?

Thanks again.
Will

 

[mvweebles]

At this point, I'd be most concerned with chafe, UV tolerant, and noise. I would go non-stretch, but wouldn't worry too much. I'm tempted to suggested wire rope witb loops in both ends - shackle to the pyramid, maybe just a loop over the cleat. But I think that might transmit noise through the hull. Perhaps just a simple 3/4" double braid dockline with a SS thimble on the bitter end and a shackle to the pyramid. Or similar but made of dyneema with a heavy chafe jacket where it loops around cleat.

BTW, for those in the San Diego area, I have a pair of Flopper Stopper plates for sale. They are used, but in okay condition. $100 for the pair.
https://www.trawlerforum.com/forums/showthread.php?t=66366

Peter

 

[willd]

Thank you.

I don’t want to use steel wire as I worry about noise (as you say) and tearing up the side of my boat. Nylon is too stretchy.

That leaves two options: double braided polyester or Dyneema. I’m going to hang them 15 feet under water now to avoid any chance of them swinging up during some sway and hitting the bottom of mine or my neighbours boat. I worry the polyester will have too much stretch over that length and thus reduce effectiveness. But I also worry Dyneema will have too little stretch and thus exert too much force on my cleat and hull when a big wave comes. I’m torn, but leaning toward polyester on the side cleats and Dyneema off the bow (as it has much further to travel just to the water).

BTW, here is what these beasts look like. Galvanised steel with anti corrosion paint. 1m^2 at the top.

 

[mvweebles]

I just did a bunch of rigging for my flopper stoppers and bought a couple reels of double braid polyester. It's been a number of years so I had forgotten how little stretch there is in double braid. My gut instinct tells me it's the right line for what you're doing. 1"/25mm?

Questions for you. Curious, what does each one of those weight? They look pretty massive even in photos. Second, there's a piece of me that wonders if, on an upswing, the pyramid might sway to allow the contents to spill-over and reduce resistance. The mitigation would be to allow some water to pass through - instead of s solid vessel, cut the peak off the inverted pyramid. But how to balance the loads (if even needed)? Wondering how you approached the design to optimize?

Best of luck to you. Fingers crossed - sure couldn't hurt.

Peter

BTW - for those in the SoCal area seeking to tame the rolly Channel Island anchorages, , I still have an older pair of flopper stoppers plates for sale. $150 local pickup San Diego area.

 

[RickyD]

I just did a bunch of rigging for my flopper stoppers and bought a couple reels of double braid polyester. It's been a number of years so I had forgotten how little stretch there is in double braid. My gut instinct tells me it's the right line for what you're doing. 1"/25mm?

Questions for you. Curious, what does each one of those weight? They look pretty massive even in photos. Second, there's a piece of me that wonders if, on an upswing, the pyramid might sway to allow the contents to spill-over and reduce resistance. The mitigation would be to allow some water to pass through - instead of s solid vessel, cut the peak off the inverted pyramid. But how to balance the loads (if even needed)? Wondering how you approached the design to optimize?

Best of luck to you. Fingers crossed - sure couldn't hurt.

Peter

BTW - for those in the SoCal area seeking to tame the rolly Channel Island anchorages, , I still have an older pair of flopper stoppers plates for sale. $150 local pickup San Diego area. View attachment 135813

I'm in on your floppers. You can PM me

 

[RickyD]

Thank you.

I don’t want to use steel wire as I worry about noise (as you say) and tearing up the side of my boat. Nylon is too stretchy.

That leaves two options: double braided polyester or Dyneema. I’m going to hang them 15 feet under water now to avoid any chance of them swinging up during some sway and hitting the bottom of mine or my neighbours boat. I worry the polyester will have too much stretch over that length and thus reduce effectiveness. But I also worry Dyneema will have too little stretch and thus exert too much force on my cleat and hull when a big wave comes. I’m torn, but leaning toward polyester on the side cleats and Dyneema off the bow (as it has much further to travel just to the water).

BTW, here is what these beasts look like. Galvanised steel with anti corrosion paint. 1m^2 at the top.

I'd use the Dyneema for your attachment bridle then something like dock lines for the rest. Choose the diameter/stretch you want.