Balancing the boat with more chain.

[model 10]

Our stern has gotten low from cruising gear. It's time for new chain up front and I am thinking about going with even more chain to help even out the trim. Another 70' would be a half barrel , 270' and the good price break. It might make the boat sit closer to level but not all the way. Standing on the end of the 4' bow sprit does not do that much. I suspect it would need another 170' of chain to level out which is crazy. That would be 370'.
I don't notice any weird sailing from the boat.

[Panope]

I needed to trim the bow down also. I got more chain, got a bigger primary anchor, added a big secondary anchor (with its own chain), stowed a third anchor under the V-berth and last but not least, moved a hundred pounds of ballast from amidships to under the V-berth.

This goes against the wisdom that says that we must keep weight out of the ends of the boat. That said, I did not really notice a difference in the way the boat handles/performs.

Steve

[skipmac]

If you put a lot of weight in the ends of the boat it will probably increase the tendency to hobby horse. I put a lot of weight in the ends of one boat and in short steep seas it was like riding a teeter totter.

[Greggegner]

Hang a bigger anchor on the bowsprit if you can. But I would first add temp weight on the bow and check how it affects the trim, that is 1 medium size women.


Greg S/V Sweet Dreams
Pearson P385 out of Racine Wisconsin

[skipgundlach]

I wonder how adding weight at the ends of the boat would induce hobbyhorsing.

There are flywheels which are mere spokes and all the weight outboard, to induce easier maintenance of motion against pulse input.

I minored in Physics, but apparently missed the boat on levers and momentum.

Someone please 'splain me how adding weight at the ends of an arm induces motion.

BTW, despite our two oversized (one massively) anchors and all chain plus 100' and rode on the other, we're still stern heavy after adding the arch and all we hang from it, as well as the other two (wimpy) anchors and some probably thousand plus feet of line in the aft lazarette. But we don't hobby our way through the waves...

[colemj]

Adding weight to the ends does not induce hobby-horsing, it increases the hobby horsing - for the same reason a flywheel weight resists changes - momentum and inertia. In other words, once the heavy bow starts going down, it will continue to fall further (momentum) than a light bow before enough force is generated to lift it again. And then at the top of that force, it continues moving up further than a light hull before gravity catches up to it.

In short/small enough seas, heavy ends can work for you by having enough inertia to never start hobby-horsing compared to extremely light ends. Just the opposite in larger/longer seas.

For relatively short monos with heavy displacement, there will not be much change in hobby-horsing by moving ballast around. For longer, lighter boats, and especially catamarans, weight in the ends can make dramatic differences in hobby-horsing.

A light end boat will hobby-horse with considerably less amplitude, but at higher frequency, while a heavy end boat can hobby-horse with an amplitude great enough to take water over the bows and up the stern.

Boat hulls with a lot of rocker or overhangs (containing weight) will hobby-horse worse than flatter run hulls carried to maximum waterline. This is even more so with catamarans.

Mark

[skipgundlach]

Ah, right. The old conundrum of the bobbing cork vs the heavy stable boat. Huge waves probably favor the cork...

[skipmac]

Originally Posted by skipgundlach

I wonder how adding weight at the ends of the boat would induce hobbyhorsing.

There are flywheels which are mere spokes and all the weight outboard, to induce easier maintenance of motion against pulse input.

...

Mass in motion has inertia, more mass has more inertia.

So as the bow rises to a wave the weight in the bow accelerates upwards, builds inertia, wave passes but bow continues moving upwards until gravity overcomes the inertia and the bow starts moving down again. Acceleration of gravity without the buoyancy of the water the bow drops and accelerates. Bow hits trough but the inertia of the weight pushes the bow down into the water until the buoyancy overcomes the inertia, bow starts to rise again.

Inertia is the mass times the square of the distance to the center of rotation so moving mass farther from the center of the boat increases the inertia a lot.

Add weight in the stern and it compliments this process.

[jrbogie]

Originally Posted by Guy

Our stern has gotten low from cruising gear. It's time for new chain up front and I am thinking about going with even more chain to help even out the trim. Another 70' would be a half barrel , 270' and the good price break. It might make the boat sit closer to level but not all the way. Standing on the end of the 4' bow sprit does not do that much. I suspect it would need another 170' of chain to level out which is crazy. That would be 370'.
I don't notice any weird sailing from the boat.

keep all weight possible OUT OF EITHER END OF THE BOAT. if anchoring is the issue, by all means the more chain the better but if your purpose is balancing the boat on her waterline think removing weight out of the heavy end and move it toward the center.

[Cheechako]

I would be evaluating how to get weight out of the stern.

[Delancey]

Chain seems like expensive ballast when there are other cheaper options available, like getting rid of junk in your trunk.

[model 10]

Originally Posted by Delancey

Chain seems like expensive ballast when there are other cheaper options available, like getting rid of junk in your trunk.

Like the dinghy engine, the wind generator the solar panels the radar the arch, the wind vane? The rest of the stuff in the trunk is fenders empty water jugs galley garbage etc. I just can't cruise without all that stuff. I guess the question might be, should you leave the stern low or drop the bow too? You can always use more chain so I would rather error on the side more chain if the only obvious draw back is hobby horsing in short seas. We don't sail those days already anyway unless we make a mistake anyway.

[Terra Nova]

Originally Posted by Guy

Our stern has gotten low from cruising gear...I am thinking about going with even more chain to help even out the trim...

Huge error in judgement. The stern is low because you've overloaded the stern--not because the bow is too light.

Load whatever chain you require. Then move your other heavy stuff out of the ends of the boat until it is trimmed.

[Olddave]

It is worthwhile learning a little about ship stability and probably the most useful fact would be that a vessels centre of gravity will move towards any weight that is added.
Having said that, I am a firm believer that you can't have too much chain. Therefore I would advise you to carry at least 300 ft and remove any unnessecary weight aft, as mentioned by others.
Good sailing, Dave

[GrahamHO]

Originally Posted by skipgundlach

I wonder how adding weight at the ends of the boat would induce hobbyhorsing.

There are flywheels which are mere spokes and all the weight outboard, to induce easier maintenance of motion against pulse input.

I minored in Physics, but apparently missed the boat on levers and momentum.

Someone please 'splain me how adding weight at the ends of an arm induces motion.

BTW, despite our two oversized (one massively) anchors and all chain plus 100' and rode on the other, we're still stern heavy after adding the arch and all we hang from it, as well as the other two (wimpy) anchors and some probably thousand plus feet of line in the aft lazarette. But we don't hobby our way through the waves...

I believe it's momentum. The bow goes up and it keeps going up. Then when it comes down it comes down harder. It is a fact whatever the explanation.