From Spin pole thread to Flopper Stoppers for BIG boats...

[redbopeep]

OK, had a bit of thread drift/non alignment of topic with my last one. Sorry about not picking a better title. So, we'll leave that topic alone but start a new one here about flopper stoppers for those of us with big heavy boats that roll like crazy in an anchorage given the right circumstances.

Has any one made their own? How'd it work?

Ian already posted this, which I appreciate, in the other thread:

" it's true that anything works a little and nothing works all the time. In my area when there's a swell running across the breeze, the breeze is usually steady enough. Also, my boats have had berths so close to the waterline and near enough the centerline that rolling was not uncomfortable. And prior to Marmalade, with her huge form stability, my boats didn't roll much anyway. Heel hard underweigh, yes. Roll, no.

The flopper stoppers I played with were triangles of wood on a three part bridle with a weight along one edge so that as it went down in the water the light side tipped up and it sank easily, deploying to flat when the roll took it back up. I played, not no certain conclusion, with two types of shock absorber. Both were similar to dock line snubbers but home made. One try was on the bridle leg to the unweighted corner. The other was a snubber above where the bridle came together. The advantage of the former was it was neater. The latter allowed a gentler start to the anti-roll.

I really think that you want a lighter whisker pole on the jib than would be suitable for the flopperstopper as well and it will be handier to just have three different spars - one whisker pole and two flopper/dinghey booms, rather than two whiskers that are heavy for the jib and light for the flopperstopper. "

[wizbang 13]

Reefed main , sheeted in hard? My mizzen helps.

[redbopeep]

I've heard of folks putting up a backstay sail (like a mizzen) for steadying at anchor but always thought that was to keep the boat pointed into the wind, not to help with side-to-side rolling.

We've just been in some very rolly anchorages and don't see that changing anytime soon as long as we're exploring the West Coast of US, Canada, and Mexico. The worst is when there is almost no wind but the swell just keeps on coming. For example, we've had a few nights with hours of rolls 8 deg port then to 5 deg starboard and back (to 8 deg port) in a mere 3 to 5 seconds. I wouldn't have believed it if it hadn't happened to us more than once.

I take it this just isn't the "flopper stopper" crowd I'm talking to, huh? I'd think some power boaters would have some ideas...

[wizbang 13]

Lee boards, not cloths, single bunks. Cocoon bunk. Gonna cruize the weat coast, gonna roll,right outta the bunk. 8%? ha!

[redbopeep]

Wiz, that's funny but not helpful. We're staying in the bunk, that's not the problem. We need a bit of restful sleep. Very hard to get that when you're rolling a little bit much a little bit fast. I actually like it when the boat rolls a bit, I find it restful. When it snaps back and forth it is not restful.

Have you any experience with flopper stoppers? I note that you're in Washington State in the summer when it is quite calm, therefore, do you even know what I'm talking about? It's funny to joke about it, but seriously, it is difficult to do a good job sailing when you're a zombie from lack of sleep.

[John B]

I made one last year , I think I had a thread on it.It worked fine. The more outboard it is the better( like on a pole) but I just ran mine off the main boom.

[wizbang 13]

I have saailed up and down the west coast 3 times. 1988, 1995,2006
My wife always goes for the sole of the saloon, which is what Ian was talkin' about. low and centered.
If you need to sleep in the pilot bunk, fold a full size matress into a single bunk, with leeboard, to make a U shaped cocoon. The boat will still roll, but you will not flop back n forth like a fish in the bottom of a boat. See? Y'can't make this stuff up.
I have never used roll dampening devises, I would be afraid of the forces involved of denying your boat what it wants to do. I can see that your hard bilge boat would be snappy, but 8% is not a lot of roll.

[redbopeep]

Yes! JohnB,

I found your thread. So, how big is your boat? weight that is? And it worked? Thanks for the info.

Wiz, it's the "jolt" that happens from time to time that wakes me up from a complete sleep. Not falling out of the bunk at all. But, there's a very harsh end to the roll when it switches back quickly and it's not consistent. So, I fall asleep and get that "jolt" awake when a bigger than expected roll jolts more than normal. Not to mention that you should hear the diesel fuel raging/sloshing in our tanks. That sound is worrysome. They're baffled tanks but even so it's a lot of fuel (173 gal/tank) and it really sloshes.

When we're underway and rolling from side-to-side while sailing downwind it is a bigger roll for sure but slower to cycle and easier to sleep during.

Seems that both John and Ian did triangle shaped ones, so that seems about to be our starting point.

[John B]

I had to add weight to the thing I made Red, but it did work ,and being set up off the boom was pretty quick to get out and also back in. I ran a safety/ trip line off its bow so I could haul it in fast if I had to get underway in a hurry and so I had a second line on it if the primary broke .

[SamSam]

Your tanks are probably baffled for fore and aft sloshing, not side to side.

[redbopeep]

Your tanks are probably baffled for fore and aft sloshing, not side to side.

Yep...I was thinking that could be the case. I'll have to ask our fabricator (La Mesa Tanks) about it when we get back down to San Diego in a bit.

Bashing around so much I swear it could end up going out the vent pipe! (well, that pipe is 5 ft above the tanks...it exits at the top of the boom gallows...)

[ramillett]

redbopeep We use a 30' scarab at the end of a 27' spinnaker pole as a flopper stopper . The trick is to make a long shock absorber out of shock cord and line . In our case we start with 2 loops of 1/4" by 20' of shock cord that hook to the end of the pole . We take a spinnaker 5/8" halyard threw the pole tip to a strong point on the scarab center line , used for a bitter end for the shock to protect the boat . If you get your shock just right , you rarely hit the bitter end ( the jerk ) . In your case it's a trade off , the longer the shock , the less effective the flopper stopper is .

[redbopeep]

Gosh, I'm feeling really stupid today. what is a scarab?

[Don Kurylko]

Red...thank the gods for small mercies - at least it's the deisel and not the holding tanks you hear sloshing about. YUK!

But I do feel your pain and I hope a solution is forthcoming. In one of the Pardy’s videos there is a segment on flopper stoppers that you might find helpful. Can’t recall which one though, sorry.

[ramillett]

.................................................. .................................................. ..............................scarab...V...

[Don Kurylko]

Oh yes, and one more thing. I read once that you can purchase ping pong ball sized perforated hollow spheres that are made specifically for fuel tanks to restrict free motion – sloshing. They apparently do the job quite well without needing to modify the tanks and don’t reduce capacity much. A Google search might turn something up.

[redbopeep]

So I have to tow a 30' fishing boat around with me? Ummm...I think I'm losing it.

[ramillett]

NO just make a shock absorber in your flopper stopper lift line scarab is optional

[Excalibur]

Red,
If the problem is the period, can you just make the boat more tender? Raise some weight (like a furled sail), to the top of the mast to slow the roll period and make it more comfortable?

[redbopeep]

Red,
If the problem is the period, can you just make the boat more tender? Raise some weight (like a furled sail), to the top of the mast to slow the roll period and make it more comfortable?

That's a thought.

We've been cruising around this spring and summer with only a partial interior and because of that many things are sitting low and lashed down low inside the boat whereas when her full interior is rebuilt/reinstalled (that's this fall, winter, and spring projects for hubby and why we're headed back to San Diego right now...) I was actually worried about how some of the weight is going to go "up" along the sides of the hull as there are cabinets and lockers outboard and up. She probably weighs what she will when done because we have a stash of tools and wood aboard that is pretty amazingly huge....hummm...I'll just hoist one of hubby's numerous tool cases up there, yea...

More seriously, I have heard of the old lumber schooners doing such things while underway but didn't think of us as being in the same situation.

Well, this morning we're off for a few days of wandering Santa Cruz Island, Catalina, and then to San Diego. So, I doubt we'll have internet access for a bit while wallowing about in those anchorages! We'll be back online in a few days.

Fair winds.

[seo]

I've never seen one on a sailboat, but some Alaskan fishboats used something called a "flume tank" that seemed to work very well. The boats I worked on either had triangular "paravane" style paravanes that we used underway as well as at anchor, pretty much as Ian McC. described on your other thread. They worked better while underway than at anchor, and worked better when at light draft, which was about 8', than fully loaded and down about 13'.
Just from looking at them a flume tank system is a pair of tanks, one at each side of the boat, with a connecting pipe. Somehow the flow was regulated so that as the water in the tanks surged back and forth it got out of step with the boat's roll, and would damp it. I think, but as I said I only observed them enviously from a distance. "They" were new 135' King Crabbers, while "we" were a 110' antique that had started life in 1943 as a 65' tug, and then got stretched out to make her a salmon tender.
For what it's worth I agree with the comments about making her "more tender" to reduce the snap at the end of the roll. I wrote some stuff in a post on your other thread about squaresail yards and their effect on roll. On the Amistad I even conducted an experiment where I timed the roll with the yards square, and then had them braced right around sharp. With the yards square there was a measureable (fraction of a second) lengthening of the roll period. Why? Dunno. I wanted to get a lot of the crew up in the maintop to see if 1,000 pounds of deckhand would change her roll, but never got around to it.
While sailing as engineer on ocean tugs I used to fool around with moving fuel between deep and wing tanks, and filling/emptying water ballast tanks to see what effect it had on roll. When running light it was noticeable, when towing it was not.

[SV Papillon]

About the only thing I have seen that works is 2 hooks, to have a good stern anchor set up to keep the bow into the swell. If there is any wind it does it for you, in the open spots where the swell rolls in all the time you end up laying in the trough non stop when its calm. never having tried it, I would think a easy way to slow a roll would be a little weight aloft, make up a canvas sand bag ? pounds, put a eye on each end and run it up a stay sail halyard with a down haul to keep it off the mast etc.

[seo]

What follows is pretty much a theory. It's based on a gizmo that I've had described to me that's used for doing inclining experiments on USCG certified vessels where Instead of shifting weight around the deck of the boat, it's possible to use a fabric bag that goes into the water and fills up. This is rigged to a spar sticking out from the vessel, with an accurate load scale in the rig. So if you want to measure heel with a given force, you hoist up on the bag's "halyard," and as it emerges from the water it goes from 0 weight to the weight of however much water (in the bag) has been lifted clear of the surface.
I can imagine a similar approach to a flopper stopper, as follows:
1) Spar sticking out from the side of the vessel, as with any flopper stopper, with hoisting tackles that attach to the mast at the spreaders.
2) Rather than the triangular flat plate flopper stopper, use conical shaped bags with circular end plates. The plates would be heavy (solid fiberglass? Plywood with lead ballast?) With holes that would allow the bag to sink and fill with water. The point of the cone would be built as heavily as the corner of a big jib, and would end in a hoisting eye.
3) The cone shaped water ballast bag would be deployed pointy-end up, and lowered down so that it floods with water. Depending on conditions, the tip would be just below the surface, or might be further down.
4) As the boat rolls, the "downhill" cone's hoist goes slack. Because the cone is underwater, it's essentially weightless, and doesn't act to roll the boat further downhill.
5) The "uphill" cone is hoisted up as the boat rolls, When it's underwater it has some resistance to being moved through the water, which damps roll. As the boat rolls further, the tip of the cone emerges, and the weight of the water in the cone is added to the righting moment. As the boat continues to roll, more of the cone comes out of the water. Because it's conical, the volume(weight) of water in the cone that is acting to resist the roll grows larger exponentially as the cone emerges from the water.
6) When the boat reaches the end of its roll, and the uphill cone becomes the downhill side, the cone is dropped back into the water where it becomes weightless, except for the weight of the ballast on the end plate, which sinks it down.
7) To recover the cones, they're slowly hoisted up, and the water runs out through the hole in the end plate.

Because the righting force grows progressively as the boat rolls and the cone emerges from the water, it might avoid some of the banging and jerking commented on by Ian McC in his comments on the triangular plate rig.

The cones would be collapsible and pretty easy to stow, compared to metal plates with hoist bridles, etc.

I one used a rig similar to this, very like the one pictured in #15 above where a 30' motorboat was hung at the end of the hoisting tackle, except that I used a 9' dinghy (40' mother ship) with maybe an extra hundred pounds of water in the dinghy's bilge. The dinghy was made up under the tip of the spinnaker pole, using the three-legged hoisting bridle normally used to hoist the dinghy aboard. It worked fine, as long as you tightened the hoisting gear enough to induce an incline of a few degrees, at which point the hull starts picking up stability. In other words, it's easier to keep a hull at a constant incline of a few degrees, while keeping it at 0º incline is harder.
Somebody who knows more than I do about naval architecture might refute this, or explain it clearly.
SEO

[seo]

There's a website from the builders of Flume tanks:
http://pws.prserv.net/flume/flumetankstabilizers.htm

[seo]

Another site with a simpler explanation of how flume tanks work:
http://atlantic-cable.com/Cableships.../flumetank.htm

[redbopeep]

Hey all, I'm back online. We'd been thinking of a waterbag type thing, funny that seo brought that up.

We're now in San Diego. We vacated our last Catalina anchorage at midnight (night before last) and just started our trip down to San Diego a little bit early because of the big swell that was hitting our anchorage late Thursday night. We were at the Isthmus Cove cursing at all those stupid moorings, the rules that say one cannot anchor within 300 feet of the durn moorings, and the few anchored boats already there that made it so one must anchor in 90 feet of water in order to anchor at all. Well, anyway, we spent a lovely night Wednesday and day Thursday there no wind to speak of and no swell...and just as we went to bed Thursday night a growing NE swell started working into the anchorage. Two things--big NE swells usually mean big NE winds and that place isn't exactly the place to be in NE winds, second--the swell wasn't long period but rather short. No wind. The boat was circling so that we'd be bow into the swell, then side-on and then stern-to. First gentle movement, then bang-bang-bang actually quite violent. Finally, we said "let's go, it's a long trip to San Diego, we might as well start now."

In the year-and-a-half we've been living aboard the boat and 9/10ths of that time at anchor, we've only left an anchorage one other time for reasons of weather, swell, etc that would make a dangerous situation.

So, there I was at midnight, standing jammed against the anchor locker in the forecastle flaking 300 ft of chain (hubby had 400 out...) into the anchor locker while the boat rolled all over the place, thinking "flopper stoppers aren't a good idea, we couldn't retreive them in this crazy rolling anyway!" and "I wonder if David's still on deck or if he's been pitched overboard?" It really was an amazing swell and a violent roll to boot.

All's well that ends well--we motored a few miles out away from Catalina, found some wind, and enjoyed a very long day of sailing to San Diego, getting in to the anchorage behind Shelter Island around 7:30 pm. We're there now...calm...flat...I now remember why I liked this place

[wizbang 13]

Long sail Catalina to SD with a NE wind in a 65'er ?

[ramillett]

Red I was checking the ocean about 4:30 yesterday thinking it was hooting off Newport , good white caps Looked like a westerly on the coast .

[redbopeep]

It was a light NE wind until about 7 am Friday, we were averaging between 3.5 and 4 knots, then nothing much (we were doing 1.7 to 2.3 knots) for a couple hours as it swung around a bit more from the North. Picked up about 9:40 am still from the North to about 10 knots. Built up with some pretty white caps in the mid-afternoon. NNW wind NW swell, something like the low teens in windspeed and we were doing 7 knots. South of Del Mar it started working around to the NW, abeam Pt Loma winds from the West at a piddly 10 knots, sunset and winds dropped to less than 5 knots and we turned on the engine to go the last 4 miles at 6 knots rather than 2 knots (sail alone).

Size: we're 69' boomkin-to-tip-of-bowsprit, 54' on deck, 46' waterline, 14.5' beam at the waterline 15.5' beam including rubrails.

[Wooden Boat Fittings]

Red,
If the problem is the period, can you just make the boat more tender? Raise some weight (like a furled sail), to the top of the mast to slow the roll period and make it more comfortable?

Picking up again on this, I remember once reading how some cruising person (Eric Hiscock perhaps?) when at anchor in a swell would occasionally hoist a spare anchor up into the rigging to slow the vessel's roll. (Sorry I can't be more specific with details.)

Thinking in terms initially of pendulum clocks here, any weight added to the clock's pendulum bob of course makes the pendulum heavier, but it doesn't change the frequency of the swing or therefore the timing of the clock. However, adding weight above the pendulum's balance point (centre of rotation) does. This is essentially what happens by hanging a weight in the rigging, as it puts weight above the 'centre of rotation' -- ie changes the metacentric height and hence the roll frequency.

Mike

[redbopeep]

I really do believe that our center of gravity (CG) or center of mass (CM) or whatever it's called is a bit lower than it would normally be right now. We are only 1/2 finished with the interior and while we decided to take 8 months off and do some cruising we also decided to just make sure she was ballasted with correct weight in the hull to counter the rig forces but...how we did that was by adding extra lead atop the keel. That lead (about 1800 lbs) will be removed when we install two more water tanks (which sit about at the waterline height whereas the lead weight is presently about 3.5 ft below that. Further, since my storage lockers are not all built in, I have stored close to 1000lbs of canned food, bottled water, and other such things under the sole atop the keel. All that stuff would normally reside at or above waterline height, too. In general, there are other things of significant weight including about 500 lbs of hardwood (for the built-ins) and 700 lbs of tools and boat parts that actually belong "higher" then they reside at present, too. When I consider all this stuff sitting at sole or below, it is no wonder that we're making quite a "snap back" quick period roll! In each and every case, I have conservatively placed heavy things as low as possible in the boat...

Following the NA plans for this boat, and looking at his calculations for the vertical CG, and working through the same, I'd say our CG presently resides 16" lower than the design CG. That is actually quite significant. When I initially did the numbers as we loaded up the boat, I was only concerned to make sure that the vertical CG resided at or below the NA design. Guess I should have really considered this rolling aspect as well.

[seo]

You could experiment with that by hoisting a weight (some of your lead trimming ballast, or a strong sailbag with a garbage-bag waterproof liner with water in it) up to the foremast spreaders. How much, how high could be tailored to return her CG to the plan, hopefully on the as-designed waterline. That MIGHT answer some questions about the roll characteristics... The advantage of using the waterbag would be that you'd have it for other interesting experiments, and it might be a little safer to deal with, because you could fill it in situ.