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Not fixed while in operation, no (if it's not rigidly mounted it can't apply torque to the hull). Not fixed permanently, yes: they're called "daggerboards."
Yes, a daggerboard. It’s like a centerboard keel, but slides through a slot instead of swinging up into the hull.
I don't think so. A daggerboard or centerboard has a similar purpose, but by definition is not a keel.
“Fixed” refers to the fact that the keel isn’t removable. It’s either part of the boat’s hull, or it’s bolted on and can’t be removed without dry-docking the boat.
There are some boat designs with removable keels. For instance, many small sailboats (called a dinghy) have removable keels, so you can remove the keel and beach them easily. The downside to having a removable keel on a sailboat is that it makes the boat prone to capsizing in strong winds; A fixed keel can have a built in ballast to keep the boat from tipping. But on a dinghy, you need to use a live ballast (literally your own body weight leaning out of the boat) to counteract the wind’s effects.
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One neat unmentioned advantage of a bilge keel is that it often enables careening without having to tip the boat on its side or use stands to prop it up.
I also feel like this cool guide should mention differences in draft between different styles of keel.
The first entry “full or long fin keel” is technically a modified full keel with a cutaway forefoot. A true full keel would have the keel extending almost in a straight vertical line from the stem to intersect the horizontal line of the bottom of the keel.
The modified full keel is a nice compromise between the comfort and stability of a full keel and the maneuverability of a fin keel.
Both types of full keel benefit from having a fully protected propeller in an aperture and the additional safety and security of a fully hung rudder. Additionally, nothing beats a full keel for rock solid dependability as the keel is molded into the hull, whereas a fin keel is generally attached by bolts, a far less structurally reliable method.
Neither can compete for speed or maneuverability with a fin or bulb keel for several reasons, not the least of which is far more additional wetted hull area and the water friction inherent therein.
I could be mistaken, but I believe this is the first time I’ve ever seen “full” and “fin” used to describe the same item. I believe those are mutually exclusive terms.
Ngl, I'm at half chub from a comment like this that expands on something cool with even more cool detail
Lol, in that case, I regret for once not divulging the unsolicited full info dump for fear of growing preachy/pedantic. We might’ve achieved full arousal!
The tier list is missing some stat that would explain why anyone would use the bilge keel
Yeah I was wondering the same. The first thing that came to mind is it’s probably the cheapest?
Does having a keel imply that the ship is self-righting? Like, completely submerged, does it also guarantee that the ship floats back to the top, oriented?
Yes. They are weighted with lead, and help keep the boat topside-up. They are also a critical component to the functioning of sail propulsion. The keel works in a kind of opposition to the sail to propel the boat forward, similar to how squeezing an ice cube between your thumb and finger will 'squirt' it out in a direction perpendicular to those forces.
But also no, if it's capsized, the boat may right itself in time before it floods to a point where it sinks.
A fully submerged boat will not bob to the surface. The keel adds stability and (counter)weight, but negative buoyancy - what keeps the boat afloat is the air in the hull.
Once it's fully submerged, there's nothing pulling it up (unless you have some seriously good (and closed!) hatches...