Fin Keel? Long Keel? Jeff?

[Curtis]

salty once whispered in the wind:
Does the type of keel (for this purpose, fin or full) make a difference in the motion of the boat (sea kindliness)? It seems that way to me, but I don't know for sure. My full keel (w/cutaway forefoot) seems to have much better (less) motion than did my fin keel.

I'm no expert but I think the difference has more to do with hull shape than keel configuration alone. Most "modern" fin keel designs are also relatively flat bottomed hulls. The flatness tends to make the boat pound and move less gently. By contrast, most full keel boats have fuller, rounder bilges and, consequently, gentler motion.

Just my (proably ill informed) observations...

[salty]

Well, all I know is my Pearson 365 discoed and gyrated wildly, while my Tayana 37 does a nice, stately waltz. I'll take the slow dancin' any day.

They are very different boats with the Tayana having greater displacement as well, so it's probably not fair to compare. However, if I knew then what I know now.....

[Alan Wheeler]

Your spot on. Full keel is much softer riding. Curtis is also correct about it being hull design, but the hull design is part and parcel to the full or fin keel. The Fin designs are usually much faster and will sail in lighter airs, because the hull is in a "planing" mode or easier to get into a planing mode, because of it's larger flat surface. But this comes at a price of pounding on the waves. No problem in light to moderate airs and for coatal sailing, but out in the big blue, get into a storm or just really big steep seas and you will wish you had a Full keel.
Oh and for the other poster on the stresses, there are stresses in either design, but different stresses. So the hull is designed to take those stresses in a different way. But in a flat bottom fin keel hull, the hull undergoes a lot more stress when pounding, than the full keel will ever have to endure.
Oh and the last point, one of the biggest dreads of a fin keel, is sliding back down a huge sea. It plays hell on the Rudder that is not supported top and bottom, that many of the fin designs are like.
Wheels

[BC Mike]

I can not agree with the too simple explanations for fin keels. The light weight boats may have something resembling a flat bottom but they are usually round and they may pound a bit more, but the mass is less so the pounding is not that great. On moderate displacement fin keel boats the bottom can not be flat and in fact may resemble the hull shape of a full keel boat so the motion is about the same. The force on the rudder going backwards would be the same, it is a matter of how well it is attached. Fin keels can be mounted to be exceptionaly strong so grounding is not a problem. Fin keel boats can steer straight otherwise the fastest monohulls would not have them. Fin keels have a lot less wetted surface which reduces drag which affects all speeds, and they tack and point better. I can post a photo of the below water of our 29 foot fin keel boat if needed. BC Mike C

[Jeff H]

Keel type generally plays a small role in motion comfort. A deep fin especially with a bulb will generally lower the center of gravity and have better dampening characteristics than a full keel, and so in theory would be expected to have a more comfortable motion than a full keel. The problem and the source of the misconceptions about fin keels and motion is that fin keels are often used on boats that have a quicker motion because of hull form, weight distribution and buoyancy distribution rather than keel configuration per se.

Jeff

[sfreivald]

Originally Posted by European Cruiser

Why am I mentioning this? Because in many cruising venues (BC/AK, parts of Cen'l America, Oz/NZ, Western Europe to mention some but not all), a boat's ability to stand on her own keel is very helpful if not at times essential. Haul-out facillities are sparse in many places, sometimes may simply be a marine railway, and scrubbing grids are in common use. Standing your boat on her own feet is a risky thing to do with a short-chord fin but commonly done with extended fins.
Jack

Hi,

I've heard and read a bit about the aforementioned need to "haul out" using the tide... I am still a novice sailor and I guess I don't understand what is considered a "short-chord fin".... for example in a 38-40 ft boat?Also, is it not adviseable to use this practice on a wing keel (with flat bottom)? It sounds like a great thing to be able to do when in remote anchorages. If this has been expounded elsewhere, I apologize, but after reading this post I am even more confused. We will soon be in the market for our next boat and of course we are making our "make or break" list! LOL. The more I read, the less I seem to know about what I want.

Also, I hear mostly about the disadvantages of a wing keel, anybody know the advantages and if they are worth it as compared to a "regular" fin keel? (or can point me in the direction of a previous thread?)

Thanks!
Sarah

[James S]

I think what is meant by short cord fin is the actual length of the bottom of the fin measured front to back.
Imagine that you want to stand your boat up along side a dock (with no water) The boat will lean against the dock on its beam...but if the fin is to short (front to back) it will tip forward of aft.

My personal opinion about wings ....if you look at the same scenario and now imagine that the wings are now resting on ground that’s uneven or sloping port to starboard.
It’s easy to imagine a great deal or torque on the wing and then transferred up to lateral forces on the fin.

Personally I'm a full keel sort of guy...I bump into stuff to much.

[rtbates]

Anyone ever hear of a full keel falling off? Can't say the same for fin keels..

A full keel boat can run aground and not suffer. A fin keel run aground can cause all kinds of hidden damage. Remember the boat out of Galveston in the race to Mex who's keel fell off? The reason? It was run aground in the past and repairs weren't made correctly.

Fin keels are held in place by bolts, that by design, sit in the bilge and rust.

For short handed sailing the ability to stop sailing and heave to is a safety issue. Full keelers heave to much better. Lots of fin keelers can't heave to at all.

[gonesail]

if you like constant steering and quick turns then get a fin keel. if you want a boat that moves straight and constant under sail then get a full keel. or you might look for a modified full keel that allows for better maneuverability especially in a marina setting.

[gonesail]

Originally Posted by James S

if you look at the same scenario and now imagine that the wings are now resting on ground that’s uneven or sloping port to starboard.
It’s easy to imagine a great deal or torque on the wing and then transferred up to lateral forces on the fin.

there is also the chance of it getting stuck in coral or rocks when you run aground ... with a rising tide that could be a big problem. and for that reason i will never have a wing keel.

[Jeff H]

I typically think of a short chord keel as a keel whose bottom that is 50% or less of the overall length of the boat (which historically was also the definition of a fin keel).

Drying out (in lieu of hauling at a facility) is always a risky and difficult proposition. It is critical to the safe refloating of most designs to prevent the boat from heeling or pitching more than perhaps 10-20 degrees in either axis and so mud legs or a pier face become important. When you have a short keel chord it becomes very critical to triangulate your supports to prevent pitching fore and aft.

When it comes to comparing fin keels with full length keels, the tracking thing is a total red herring. Tracking is about dynamic balance more than keel length. What many full keel advocates fail to remember is that boats with fin keels- skeg hung rudders often have a greater longitudinal polar moment than deep keeled boats with cut away forefoots and raked rudder posts.

The design of a well designed fin keeled boat tends to result in lower helm loads and better balance than most full-keeled boats that are out there. In this time of autopilots and windvane steering, the light helm loads of a fin keel boat become far more critical than the theoretical tracking of a full keel. Of the 14 boats that I have owned and the hundreds of boats that I have sailed, the worst tracking boat I ever owned had a longish keel with an attached rudder, the second worst tracking boat I had had a full keel, and the best tracking boat I have owned had a fin keel.

Being able to heave to is also a bit of a red herring in that hull form and rig play a bigger role than keel shape. I never owned a boat that could not hove to, fin or full although the worst at heaving to were the 1960's era CCA boats that I have owned with their short chord keels with attached rudders.

This is an old thread but there is some discussion of wing keels in my post (Post #2 above). There are some minor advantages to wing keels in that they can increase stability in shallower draft boat over a boat with a shallower keel without either wings or a bulb. Most provide improved sailing ability over a typical shoal keel, but decreased sailing capability, and motion comfort over a deeper keel. Most would be a poor choice for drying out.

Jeff

[sfreivald]

Originally Posted by James S

I think what is meant by short cord fin is the actual length of the bottom of the fin measured front to back.
Imagine that you want to stand your boat up along side a dock (with no water) The boat will lean against the dock on its beam...but if the fin is to short (front to back) it will tip forward of aft.

My personal opinion about wings ....if you look at the same scenario and now imagine that the wings are now resting on ground that’s uneven or sloping port to starboard.
It’s easy to imagine a great deal or torque on the wing and then transferred up to lateral forces on the fin.

Personally I'm a full keel sort of guy...I bump into stuff to much.

James,

Thanks so much! The lightbulb went off with your explanation... I wasn't thinking about it measured from front to back, duh!

After I posted my question I found a snipet about it in "The Cost Conscious Cruiser", which explained the process well.

PS pretty boat!!

[sfreivald]

Originally Posted by Jeff H

This is an old thread but there is some discussion of wing keels in my post (Post #2 above).
Jeff

Jeff,

Thank you for your explanation. I knew this was an old thread, but I couldn't find what I was looking for elsewhere. The distinct disadvantages of a wing-keel make sense to me, and I am planning on steering clear of them, but I do like the performance aspect of the fin keels. I also thought that it was possible to heave-to in a fin keel, and your response helped confirm that it is more than keel shape that contributes.

Sarah

[Captn_Black]

Everything I've read says that a long keel is better for bluewater cruising. Especially if your short-handing as its less strain on the autopilot(whatever type you use).
This book goes into the subject in some detail - Seaworthy Offshore Sailboat: A Guide to Essential Features, Handling, and Gear: A Guide to Essential Features Handling and Gear: Amazon.co.uk: John Vigor: Books
And will certainly help you make a decision based on the facts...

[Jim Cate]

Originally Posted by Captain Jaz

Everything I've read says that a long keel is better for bluewater cruising. ...And will certainly help you make a decision based on the facts...

Jaz,

All I can say is perhaps you should expand your reading list a bit! For instance, you might try the Dashews' many publications, especially one called (from memory) "The Circumnavigators Handbook". They might convince you to reconsider your "facts".

Cheers,

JIm