Morning Musings - Hobby Horsing?

[Chotu]

Waking up with a morning musing today.

If putting weight in the ends of a monohull leads to hobby horsing, wouldn’t it stand to reason that putting weight outboard on a monohull would lead to more rolling at anchor?

[sanibel sailor]

Slower roll with greater excursion. Think metronome.

[a64pilot]

Heel yes, not so sure how much additional rolling moment, mass up high or low anywhere would I think increase that, putting it outboard just increases the heeling.

On the metronome, our mast greatly reduces the rolling period, so yes we roll as much as a power boat, just at a greatly reduced rate, and lower rates are more comfortable.

Having watched a lot of boats hobby horsing, I feel it’s more of a hull design thing than weight, but weight will aggravate it, we can control weight, but not design. I say that as with all the weight I have added to the ends of my boat she should hobby horse badly, but doesn’t.
You go adding 1000W of solar panels off the stern and hang a dinghy there with its outboard motor and a generator in the Lazarette, then on the other end put 100M of chain, two BIG anchors and fuel on deck, you should set up a recipe for bad hobby horsing, but most don’t.
But you see a different boat in an anchorage pitching wildly with none of that weight.

[hpeer]

Our boat does not roll much, but she can really pitch.

I suspect bow and stern shapes have a good lot to do with it.

In my experience pitching, and rolling, is highly dependent upon hitting a resonance between the boats natural frequency and the wave action.

We had one night in St Pierre that was wild. A SE running tide against a NW running swell. She was laying to the tide and pitching fiercely, wage almost coming over the transom. I rigged a weighted drogue, sea break, which took out a good percentage of the travel.

[rslifkin]

I'm with a64pilot on the hull shape thing. My boat is power, not sail, but pitches fairly violently in a steep head sea. It's definitely not weight, as she's fairly light up forward, but she's a planing hull with a very full, buoyant bow. So the pitching comes from the hull shape being determined to go up and over a wave at any cost, rather than through it (at least at low speeds, at higher speeds it'll smash through a bit).

If anything, I'd think more weight forward might calm the pitching on a hull with a lot of forward buoyancy, as it would push into a wave more and not ride over it quite so easily, so while it may pitch down a little faster on the back side of the wave, it wouldn't have pitched up as high to start with.

I'd think a boat with a lot of rocker in the hull and a narrow stern would be a bit more prone to hobby horse than something with a wide stern and more boat in the water aft, as the narrow stern with lots of rocker would be able to move down more easily, adding to the pitching (putting the point of rotation in pitch further forward on the boat).

[Chotu]

Originally Posted by hpeer

Our boat does not roll much, but she can really pitch.

I suspect bow and stern shapes have a good lot to do with it.

In my experience pitching, and rolling, is highly dependent upon hitting a resonance between the boats natural frequency and the wave action.

We had one night in St Pierre that was wild. A SE running tide against a NW running swell. She was laying to the tide and pitching fiercely, wage almost coming over the transom. I rigged a weighted drogue, sea break, which took out a good percentage of the travel.

I had a crazy experience with this situation myself. One time at anchor In absolute calm conditions, I experienced the worst rolling of my life.

It was so calm that you could pretty much see the craters in the moon on the reflection in the water. Absolutely no wind. No waves to speak of. No chop. No ripples. In fact, it was one of the calmest nights I’ve ever spent at anchor until the rolling started.

I was tucked in behind a series of islands about seven islands in from the open water near the shore. Near the mainland.

At low tide I slept like a baby. Then around midnight, the boat would start slowly rocking back-and-forth increasing more and more and more until everything was smashing and thrashing around in the boat and you were getting thrown out of your bunk. Worse than any sport Fisher wake.

Then after a few moments of everything crashing around, the rolling motion would slowly settle back down and go away. And it would stay away for five or 10 minutes. Just enough time to fall back asleep. Then it would start up again.

I have never experienced anything like it and have still not experienced anything like it to this day.

The harmonics were just right. Somehow, a bit of swell must have been making it around all of those islands and into the little bay on the mainland. So the absolutely calm water with no wind must have been moving Imperceptibly up and down from the swell at just the right frequency for the boat.

It was actually that night that I changed to Catamaran’s. Ha ha Ha. And I’m not joking. I had had it. I think it was a fairly sleepless passage to get there to begin with. This was the chance to get in a good nights sleep. And I still couldn’t. For half the night that Boat was doing that. Then of course the fisherman blasted by at 5 AM to wake us up. Didn’t matter what orientation I put the boat in, nothing mattered. Somehow the frequencies just added up perfectly.

It was pretty cool in a way. But it was not any fun at all. And when I say thrashing, I mean thrashing. You could hear dishes smashing around and everything.

[GordMay]

Originally Posted by sanibel sailor

Slower roll with greater excursion. Think metronome.

Indeed!
Increasing weight, in the ends (or on the rails) increases amplitude, but decreases frequency, of pitching (of rolling).

[Chotu]

Originally Posted by GordMay

Indeed!
Increasing weight, in the ends (or on the rails) increases amplitude, but decreases frequency, of pitching (of rolling).

There we go. Thank you Gord.

To me, it would seem a higher frequency but lower amplitude would be more comfortable. More like what a car feels like. Or Catamaran.

It’s those deep rolls at anchor that are the most annoying. And if you kept the weight out of the bow and stern as well, you wouldn’t have so much spray or submarining going on.

[zeehag]

i had roll issue until i replaced lightweight fuel tank in belly of formosa to a stainless heavier one. bingo no more roll. easy to figger out. keep weight low and centered.

[jewt]

I have found that shortening the anchor snubber on the side that the swells appear to be coming from sometimes helps. The pitch is easier to live with that the roll.

jewt S/V Bifrost 8

Trapped @ home New Bern NC