We’ve got Flopper Stoppers!

I remember years ago chatting with a couple who were cruising and they said you must get flopper stoppers, they’ll make nights on anchor much more comfortable. At that time we hadn’t been outside the Hawkesbury/Pittwater region and I couldn’t imagine what they were or how they’d work! Well they’re designed to stabilise your boat when on anchor or a swing mooring. They work by altering the roll of the vessel and the boat’s own momentum counter-acts the roll by 70–90% reduction (depending on the boat and units purchased). 

Since we’ve been cruising over the past 11 months, we’ve certainly experienced some very rolly anchorages, where you sit in the saloon and see the water, then the sky, then the water, and so on, and end up feeling very sick! 

Robert’s been researching what would work best for our boat, not require us to make serious reinforcement to the structure of Poseidon, nor significantly change the look of her. By the time we reached Hervey Bay, we knew what we needed and finally had our flopper stoppers installed!  

Overview of our flopper stoppers

It’s easier for me to explain our flopper stoppers using photos, but in summary, we have one unit on each side of the boat. A unit comprises:

  • An attachment through side of boat with goose-neck fitting on the outside and a stainless-steel plate on the inside of the hull to hold it in place.
  • A 3-metre pole that attaches to the goose-neck fitting. The pole is unfinished alloy, 65 mm outside diameter with a 6 mm wall. It looks a bit industrial but it’s fine. Stainless steel would be nice but also more expensive. The pole has four attachment points on the end:
    • One point to hold a line to the stern and one to hold a line forward, to keep the pole at about right-angles to the boat when in use.
    • One point to hold a line to a connection up above called a ‘topping lift’.
    • One point to hold the flopper stopper, which submerges into the water.
  • The ‘topping lift’ plate is attached to our upper deck and bolted through to a plate underneath. There’s a line that’s connected between this and the end of the pole, and the force is transferred from the flopper stopper to this plate. When deployed, the line is extremely taught.
  • The flopper stopper unit, which looks like a disk on a spring, with a weight at the bottom that includes a chain and a line.
  • A number of lines and pulleys for attaching to the boat, which Robert did himself. 
Notes about our installation
  • We purchased our flopper stoppers from OceanTourque. The flopper stoppers come as a set of 2, are quite expensive but are very well made and come with lots of bits (weights, springs, lines etc.) that would quickly add up if purchased separately. For our boat (50’ motor cruiser weighing about 27 tonne), the #4 size seemed right though there is a view that bigger is always better!
  • We got the poles and fittings for the boat when at Hervey Bay from a local supplier. Because we couldn’t source the gooseneck fittings ourselves, he came up with a universal type fitting that seems to be a good option. He also made the four attachment points on the pole ends to help minimise any issues with the pole sitting horizontal against the boat side.
  • We had the poles fitted by another local supplier. His work was good, but because he’s away a lot it took a long time, and in retrospect Robert could have probably installed them. But he did a good job and made a very good suggestion to beef up the sides of our boat where most of the compression is, as our sides are hollow, so when we get to Townsville we’ll do that. We’ll cut a hole out of the fibreglass on the inside and chock it with wood, then use a bigger plate on the inside. 

Deploying the flopper stoppers

This is a bit tricky as there’s quite a lot of weight by the time you join up all the parts. So Robert worked out a pulley system that supports the unit before it’s deployed, then also lets us more-easily retrieve the unit. In summary, this is our procedure:

  1. We attach the lines (and ribbons) to the 3m pole and pull the pole out, so it’s roughly at right angles to the boat.
  2. We secure the forward and aft lines to cleats to keep the pole in situ. There’s a black line that stays in situ that attaches from the end of the pole to the topping lift plate.
  3. We then start building the flopper stopper unit keeping it fully supported by the pulley system at all times.
  4. We secure the line that is at the bottom of the flopper stopper unit because this is what we pull to help bring the flopper stopper in. This lets us move the disk onto its side, otherwise we’d be trying to pull the disk straight up and would be fighting the very force that is designed to stabilise the boat.
  5. We loosen the pulley line and let the unit into the water.

I think this process takes us between 10 and 15 minutes, because we haven’t done it often enough yet to quickly remember how to set up some of the lines! But I timed us bringing it in and disassembling it and it took 8 minutes. It was quicker because we weren’t trying to remember which side to put the different lines on!

Do they work?

Emphatically yes! We used them first at Rooney Point after we left Hervey Bay and it was quite a rolly anchorage, which was why we chose the location to test the unit. See video below. 

We’re currently sitting in Pancake Creek at Bustard Head (between 1770 and Gladstone) and using them. There’s a strong current that runs through here and we have noticed that they’re impacted by this – insofar as they don’t remain straight down in the water, but instead drift a bit with the current. However, on balance they are extremely effective for us. 

We’ve also made some minor adjustments to our pulley set-up, such as adding some more shackles to make sure there are no single points that, if they failed, could result in losing part of the unit. While it’s still early days and we’re improving our deployment process, I have to say, it was money well spent to have more comfortable times at anchor! 

4 Responses

  1. It was very interesting to read about the flopper stoppers. I am glad that they are proving useful.

  2. Flopper stoppers seem like a good name. I hope your seasickness has improved as a result. Do cats and dogs get seasick I wonder?

  3. Wow. You researched and found your solution. Looks complicated but Iam glad it works. Enjoy your smooth anchorage.

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