Making a Better Flopper Stopper: One Year Later

23 Apr Making a Better Flopper Stopper: One Year Later

Posted at 18:03h in About MV Starr, Blog by Don and Sharry 1 Comment

Sharry and I have been cruising the South Pacific and more recently Hawaii since 2001.

Hawaii has a reputation for challenging cruising since most anchorages are open roadsteads. The Pacific swell is ever-present and stabilization at rest makes many more anchorages available. Last year we cruised 1900nm around the Hawaiian Islands and were at anchor about 90 nights, most of which required flopper stoppers for comfort aboard. We were anchored in Hanalei long enough to have barnacles growing on our flopper stoppers.

Our primary complaint with existing flopper stoppers is they don’t sink fast enough. They tend to skew sideways like a pie plate sinking, then jerk to attention when the boat rolls the opposite direction. This causes shock loading on the rigging and uncomfortable motion aboard. Another experienced cruiser reported that the Magma/Prime/plate type flopper stoppers eventually tear themselves apart as they sail and jerk.

We’ve had more success with rubber valve type flopper stoppers, but they don’t sink fast enough in big swells. The easiest solution to having them sink faster is to add more weight, but at 40 pounds they’re already difficult (and sometimes dangerous) to handle.

Rubber valves in the “open” (sinking) position

Click here to see the post from a year ago where I more thoroughly described the shortcomings of existing systems.

John Henrichs, owner of Tiger, an FPB 64 introduced me to the flopper stopper that he and Sandra have been using in the Fiji area for the past couple of years. The flopper stopper is designed and built by sailor John Griffith, see www.Flopstopper.com.

FlopStopper with shutters open (the sinking position)

FlopStopper with shutters closed (at rest or on up stroke)

The Henrichs’ have tried virtually every other flopper stopper and this is the best that they have found. You can read Johns comment about the various flopper stoppers that didn’t work for him in the comments section of my posting “How can we design a better flopper stopper?”

I believe this is the best flopper stopper I’ve seen so far, but I think it can be improved for our use. The FPB 64 is a little under 50 tons, (half of Starr’s 100 tons) and the pole to pole spread is 30 feet verses Starr’s 60 foot pole to pole spread.

Even with John’s 30 foot pole spread, he found that when using the shutter type flopper stopper he needed to add additional lead ballast. The flopper stopper weigh 22# without lead. Optimally I can keep the weight down and still drive them down efficiently.

My modifications are:

Replace the aluminum end sockets with 304 stainless square tube and weld on clevis tangs.

Replace the nylon straps with rigid connections. I started with four 5/16 inch stainless all-thread connection rods to connection head but will replace the 5/16 inch stainless all thread with stainless tubing for less flexing.

Replace the dyneema tension line with a rigid pole. I’m trying out a 1 inch x 20 foot stainless compression-tension pole (CTP) with a wall thickness of 0.065 inch. This puts the flopper stopper about 9 feet below the surface.

Connect the 20 foot stainless compression-tension (CTP) pole to the head of the main 4 inch pole in such a way as to have a “U’ joint type connector that won’t buckle on the compression stroke.

We plan on departing Seattle to return to Hawaii this August (after spending a delightful month sailing and exploring Sweden on a chartered sailboat). Optimally our first stop will be Hanalei in Kauai where we can test the new flopper stopper against our old rubber valve and the stainless plate type flopper stopper. Stay tuned!