DIY flopper stopper

[felizcortez]

I am building a diy flopper stopper (roll reducer) out of some extra plywood I have on the boat. Since the piece of wood will be below water when in use I need to waterproof it somehow.

Should I just paint it with epoxy or should I put a single layer of fiberglass on it?

[GILow]

Personally, I’ve found it hard to get a thick enough layer of epoxy to waterproof plywood without using a bit of fibreglass.

[ctl411]

Layer of glass for ding/abrasion resistance. One little nick/crack and plywood becomes a sponge...

[CassidyNZ]

What sort of plywood is it? Because, seriously, for the amount of time it will spend in the water, a simple cover of a decent two-part urethane paint (or epoxy if you have some going begging) will do it.

Many years ago, in a previous life I was into competitive 3-event water skiing. At our club, we built a jump ramp out of 19mm construction pine ply. That ramp lay anchored in fresh water for 15 years that I know of with no visible rot. And it was painted with domestic enamel paint every two or three years.

[daveNZ]

A couple of costs of everdure.

[felizcortez]

So I ended up wrapping the plywood on 1700 biaxial because that was all I had. Waiting for that to finish cureing them will give it a try tomorrow.

I was going to try it out first before I put a finish coat of paint on it.

[RaymondR]

I generally try to encourage folks to take on boat projects being an enthusiastic DIY person myself however over the years I have seen numerous flopepr stopper projects which quietly sank into oblivion. Give us a sketch or good description and we'll be kind enough to constructively critique it for you.

[Steve Bean]

If I wanted to make flopper stoppers I would first look on YouTube for ideas; there are about 20 articles. Also I would search this forum and other sources for ideas.
Regarding painting plywood, over the years I've come to the realization that sometimes plywood remembers how it was before it was sliced up and flattened out. It doesn't like the way it was treated, and if not well sealed or fiberglassed, it tries to curl up again, resulting in a failed paint seal. I'm experimenting with applying a layer of light sailcloth with epoxy resin, then paint. Cheaper than fiberglass, no fiberglass dermatitis; I don't need the strength.

[felizcortez]

Here is a progress pictures. I'm going to make a 3 rope bridle and hang dive weights on it to make it sink. I potted the holes with epoxy I'm going to drill. I had scrap laying around so I epoxied them together to get the right shape. I still need to sand some of the sharp bits of glass off.


I have a 37 ft boat and this one is about 26 inches on each side of the isosceles triangle.

I told another boat what I was doing and he gave me 4 of the Mexican hat style roll reducers. I put those out last night and they made a bit of a difference. Interested to see how mine will compare.

[felizcortez]

Finished up the flopper stopper today. Will get a chance to compare it to the Mexican hat style when the waves pick up later.

I used some dive weights that I had on board to sink the plywood and one on the edge so it would dip.

Here is a video of it just below the surface of the water before I hung it from the boom.

https://youtu.be/1tbCvTNpKL0

[felizcortez]

Originally Posted by felizcortez

Finished up the flopper stopper today. Will get a chance to compare it to the Mexican hat style when the waves pick up later.

I used some dive weights that I had on board to sink the plywood and one on the edge so it would dip.

Here is a video of it just below the surface of the water before I hung it from the boom.

https://youtu.be/1tbCvTNpKL0

So I tested these out today. Performance is similar between the Mexican hat ones and also the one I built. If you deploy them on one side, they don't stop the initial roll, but percent oscillations that build and make things uncomfortable. You move quickly one direction and then slower the other as the flopper stopper resists the movement. I would say that by themselves they take the edge off the roll.

I also tried putting the one I built out on the boom and just hung the hat ones off a mid ship cleat. That actually made a pretty big difference as you are getting dampening in both directions. If you rigged the second one out on a Spinnaker pole that would allow it to work better. I may try that later, but I need to free up one of the jaws that is frozen shut first.

Overall, I'm pretty happy with the result as it has improved things at anchor in the rolly anchorage where we are currently located. It wasn't too bad, I had the scraps laying around the boat for the wood and already had the glass/epoxy.

[felizcortez]

After living with these for a few days at anchor, I would definitely call the project a success. Things are a lot more stable with both roll reducers deployed.

[felizcortez]

So after a little more than a week of use I am trying to fix a chafe problem where the dive weight line goes through the flopper stopper. It appears to be rubbing inside of the hole which is the one that has the most movement because that one constantly dips. The dive weight I have also hangs from this hole so there is probably a good deal of movement.

Any recommendations?

[CassidyNZ]

Secure the dive weight with a couple of screws?

[mvweebles]

Has anyone tried making a DIY Flopper Stopper with a cut-down 5-gal bucket? Cut out the bottom to leave four pie-shaped wedges open, then an inside diaphragm from another bucket loosely tethered at the hub/center so when the bucket descends, the diaphragm floats free. On the up-stroke, diaphragm closes providing resistance. Total cost would be $10 for two buckets plus a 5-10 lb fishing weight. One on each side, and would nest together for storage. Thoughts?


Peter