Wing Keels

Fin keels are a very broad category of keel which is characterized by a high aspect ratio appendage. Within this category are a vast world of variations and subtle differences that give rise to very different performance characteristics.

The theory behind a fin keel is the leading edge will produce lift which will carry the boat to windward. The whole keel is shaped like an air foil to aid in generating lift and make the entire system much more efficient. ​

To create more leading edge, you simply need to have a longer appendage, simple! The problem is a longer appendage directly translates into deeper draft. For yacht builders, a deeper draft means that buyers in shallow waterways will not buy their product. Yacht builders want to be able to sell their yachts to everyone, which means that they need to produce a yacht with a shallow enough draft that it will appeal everyone while still retaining the desired performance attributes that will make them competitive when compared to deeper draft competitors.​

Yachts compete on windward performance and on their ability to sail into ​shallow waters. Naturally, these two camps are on opposite sides of the spectrum. You can either sail to windward OR get into shallow waters, not both with a regular keel.

This is where the wing keel shines. A wing keel is a regular fin keel with small wings projecting to the sides at the tip of the keel. These little wings serve two purposes: They provide more leading edge length and they create less drag from tip vortices.

Adding wings naturally adds more leading edge to the keel, but instead of adding more leading edge in a downward direction, the leading edges now travel laterally. This is supposed to produce the same lift generated as a longer fin keel without the added draft.

Tip vortices directly relate to drag, and reducing these will reduce drag. Reducing drag will directly result in an increase in speed and higher performance! Tip vortices occur at the end of every airfoil. On an active airfoil, there will be a high pressure side and a low pressure side. The air foil in the middle acts to separate the two pressures and the resulting pressure differential will drive the airfoil. At the tip, there is no airfoil separating the two pressures and the high pressure side will spill over into the low pressure side, resulting in a vortex that trails along the tip of the airfoil.

A small wing at the tip will help reduce the spillover of pressures and reduce the size of the vortex. Air planes use these winglets at the tips of their wings to reduce drag and improve fuel economy, and sailboats use them too in the form of a wing keel. The wings on the sides of the tips are supposed to reduce drag by reducing the tip vortex.

While a wing keel may sound like the perfect solution to a sailor who is searching for a high performance yacht with a shallow draft, but they do have an additional problem with groundings.

Fin keels are rather weak and can suffer great damage during a grounding, but the sailboat can usually work its way off a shoal with enough effort. A fin keel will dig into the bottom, and be easily pull free from the bottom as you work yourself off a shoal. A wing keel on the other hand will dig into the bottom and get really stuck! Those wings will act like anchor flukes which will dig in and hold if you run aground in soft mud. 

If you plan on sailing a fin keeled yacht into shallow waters and are looking at a wing keel for the added performance, be weary! If you are going to explore into shallow waters, you will eventually touch the bottom!  When this happens, getting off will be a much harder ordeal. You may think you will never run aground, but it will happen if you like to explore shallow waters.

Wing keels supposedly offer added performance benefits with a shallower draft, but don't abuse of the shallow draft and go looking for trouble in waters where you can't float.

Fin Keel Weakness

Fin keels compliment the sails of a sailboat remarkably. High aspect ratio keels, just like high aspect ratio sails, offer gains in performance while reducing the effects of unneeded drag and weight. While these underwater appendages work astoundingly well, they do have their limitations. If you are able to sail without conflicting with these weaknesses, a fin keel can serve your yacht very well. On the contrary, if you find that these weaknesses will interfere with your ideal method of cruising, a fin keel would not be your ideal setup.

Fin keels attach to the bottom of the hull via a small contact area. This small area has to withstand all the stress placed on it by the forces acting on the hull and the keel. When your yacht catches a puff of wind and heels over, the force on the sails heels your boat over while the force on the keel tries to right the yacht. The junction of the keel and hull is under extreme stress as the hull is trying to pull up while the keel is trying to pull down. If you combine these stresses with heavy pounding seas, the loads experienced by this small area will climb exponentially. With time and stress, fatigue will set in and stress crack will begin to form around junction of the keel and hull. 

Another problem with fin keels is they are not very well protected from impact. They are, by design, a very long lever arm. If you were to strike an underwater object, be it a sunken log or the sea bed, this force is going to be multiplied and then transmitted to the rest of the yacht via a very small area. This small area will be subjected to extreme loads and can form cracks.  

In the Chesapeake Bay, most creeks are around 4.5 to 5 feet deep. Sailboats with shallow enough drafts will attempt to enter these waters, typically running aground at some point during their life. When a grounding occurs, the forces excerpted on the keel are enough to create these characteristic cracks in the front of the keel near the hull.  

These cracks are just the visible damage that occurs to the yacht, but the forces run much deeper and so do the damages. The bolts that attach the keel to the hull are located in the bottom of the bilge and are often bathed in bilge water for the life of the yacht, causing corrosion to wreck havoc on the bolts. The combination of these bolts rusting away and the forces from an impact can cause the keel to actually fall off! If the keel falls off, you now have two very major problems.  

First, the keel is gone and the keel bolt holes (which are rather large) are open and flowing a lot of water into the hull. If these holes are not plugged quickly, your yacht could sink from the in flowing water! 

Second, the keel is gone! You no longer have any ballast or righting moment to counter the sails. If a puff of wind heels you over, you will capsize! Worst of all, if you do capsize, you will not right yourself because the ballast is gone. Losing your keel is not just terrible, it is horrible! 

If you decide on a yacht with a fin keel, don't try exploring shallow waters. If you run aground, damage will occur to your underwater appendages and the repairs can be quite costly. Think of a fin keel yacht as a deep water dream machine! It will glide through the waves with ease and efficiency, but it is a fragile dream machine. If you hit it too hard, it will break along with your dreams. 

Fin Keels

Fin keels are the epitome of performance! They project out of the hull as a high aspect ratio appendage with a long leading edge to generate as much lift as possible with as little drag as possible. The narrow fin slices through the water with ease and its airfoil shape adds to its efficiency.  

The long fin keel locates the mass of the ballast far from the hull, providing a long lever arm to aid in righting moment. This added leverage uses the ballast more efficiently which means that less ballast is needed. Less ballast also means less weight which directly relates to the yacht having a lighter displacement. Lighter displacement gives the sailboat greater speeds in light airs, and much greater speeds overall. Fin keels truly are the ideal underwater appendage from a performance standpoint! 

If your dream yacht is a high performance machine that will zip through the water toward your destination, be sure that you size your keel accordingly to the waters you intend to navigate. The longer the keel, the better the yachts ability to point, but the yacht will also have a deeper draft. 

If you plan to cruise in waters that average around 6 feet deep, then a 10 foot keel may be problematic. Your cruising grounds will be severely restricted and limited to only the deeper areas. If you went with a shorter fin keel, you will still have the performance benefits of a fin keel with the increased cruising realm of shallower waters. 

It would behave you to look over the charts of your intended navigable waters and examine the charted depths. Identify the creeks and rivers you wish to sail into and record their water depths. By compiling the data by depth, you can see how different drafts will remove potential cruising waters.  

For example:

Creek A, Creek B, and Creek C have depths of 4 feet;
Creek D, River E, and Bay F have depths 5 feet;
River G, Bay H, and Creek I have depths of 6 feet.  

If you choose a boat with a draft less than 4 feet, you could cruise all the bodies of water that you have identified.
If you choose a boat with a draft less than 5 feet, you can no longer enter Creek A, B, or C. 
If you choose a boat with a draft less than 6 feel, you can only cruise in River G, Bay H, and Creek I.

If you did not look at your local charts before you purchased your yacht with a 10 foot draft, you would be disappointed when you can not enter any of the cruising waters you wanted to explore! 

While fin keels are excellent performers, be sure to size your keel accordingly to the waters you wish to cruise instead of solely focusing on the performance aspects of the keel length. 

Wedding Registries for Liveaboards

Registries are magical accounts where you can choose mountains of gifts that you wish to receive for your wedding.  Normal registry items consist of fancy dining ware, crystal, wine glasses, vacuums, and endless amounts of household appliances.  This is all well and good…if you live in a house.  The registry of a live-aboard is a tricky thing to create.  I had to completely alter my thought process to include plastic instead of glass and anything that happens to come with a compactable capacity.  I managed to do a pretty fine job of it in the end, and we ended up with a wide variety of handy boat-friendly options.  I’m going to list some of the things we are most happy with. 

1.       The Fruit Hammock

a.       This is a FANTASTIC way to store fruit and vegitables that don’t need refrigeration such as apples, bananas, oranges, avocados, and onions.  This item is inexpensive, so it was a perfect gift option for my college friends who are still trying to begin their careers.  The hammock hangs completely out of the way on the nobs that open our porthole where it is accessible from the galley.  It expands to fit tons of food that simply swings back and forth during wakes and storms instead of rolling all over the counter.    

2.       Solar powered Inflatable floating lanterns

a.       These are a beautiful invention.  They store easily and when we are underway we simply flip them over so that the little solar panel on the bottom faces the sun.  When night falls and we wish to read or dine outside, we blow them up and place or hang them around the boat.  If they fall overboard they are easily recovered since they float and they come with three light settings including a flashing red SOS.  Herby takes one with him on the dingy when he rows Morty ashore so that I and other boats can see him.  We registered for and received 8 of them!

3.       Two-Person Hammock

a.       If you don’t already have a hammock on your boat, you’re doing it wrong.  There is nothing more peaceful than being in a hammock as it gently swings you with each subtle movement of the boat.  Herby and I like to relax in our double hammock while I read to him in the evenings.  It even closes up above us to keep out the bugs, and when it gets dark, I use a solar lantern to see!

4.       Flexible Wine Glasses

a.       We have broken all but two of the original glasses Herby had on the boat when I moved in.  They fall in the sink during wakes, they clink together in storage, and they slide off the table when bumped, which happens a lot since there isn’t a lot of space to move around the salon table.  I registered for two types of wine glasses, therefore, that give off a classy appearance while remaining nearly indestructible.  Govino is a company that makes adorable Plexiglas wine glasses that flex in your hand and include a handy dimple for your thumb.  We have received tons of compliments on them while entertaining.  They are super light and make absolutely no sound when they bump together on the shelf.  I also registered for high quality plastic stacking wine glasses because they stacked so beautifully I couldn’t resist. 

5.       Britta Filter

a.       The Britta filter has become our best friend.  The water that stores in our tanks comes out of the faucets tasting terrible.  We previously fought this issue with tons of water bottles which was incredibly wasteful and costly.  Once our tank water flows through the Britta, it tastes completely normal!  We simply keep the filter in one half of our divided sink so that it doesn’t knock over.  We drink so much water there is no need for refrigeration.  We simply fill it with as much as we plan to drink at that time.     

6.        Stand-up Paddle Board

a.       Stand-up paddle boarding is both super fun and quite useful.  If you are cruising or living aboard, I highly recommend getting an inflatable paddle board.  It stores very easily and does not take much effort to inflate.  It’s a fun way of exploring new areas if you are anchored in a protected creek and it serves as a quick and easy way to get your dog to shore if he is small and has a low center of gravity like Morty! 

So there you have it: six awesome and smart registry items for live-aboards.  We are so very happy with our decisions!!  

Keel Designs

When searching for your dream liveaboard sailboat, the variety of keels may raise some questions as to which one is the best?

The truth is, they are all good and bad at the same time. You have to find one that fits your needs and demands, and has drawbacks that you are willing to accept or don't bother you.

In general, keels are either fin or full. Within these two broad categories are a multitude of variations, but in general, they fall into these two camps.

Fin keels are characterized by their long, high aspect ratio projections from the bottom of the hull. They provide greater performance and less drag, but they are not as strong as a full keel. The hulls have a shallower bilge which results in less wetted surface area, all leading to greater performance.

Full keels are characterized by their low aspect ratio projections, running the length of the hull. They provide less performance, more drag, and add lots of weight to the yacht. This may sound like a horrible keel choice, but it does have two strong characteristics. It is strong and it creates a nice slick to windward when hove to.

Full keels offer a greater area of attachment to the hull and spread the forces from the keel over more of the hull. This very strong attachment to the hull resists breaking under normal and extraordinary conditions. 

Normal loads on the hull-keel joint are experienced when the yacht heels over and the keel acts as a lever arm with the ballast at the end. This load is torquing on the hull, trying to turn the hull back to a vertical orientation. A full keel will spread this force out over a greater area and lead to less stress cracking in the hull at this junction.

Extraordinary loads occur when a yacht is grounded. When the keel smashes into the seabed, all that force is transmitted to the hull via the hull-keel junction. Spreading this massive force over a larger surface area decreases the pressure at this junction and reduces the risk of damaging the yachts hull. This means that a full keel boat will survive coming in contact with the bottom with less risk of damage or holing. 

A full keel provides more drag through the water when hove to and sliding sideways. This added drag will lead to a slower rate of drift and provide a very disturbed slick to windward which will calm the approaching seas from breaking waves into rolling waves. 

The negative attributes of a full keel is the increase in wetted surface area adds lots of resistance which leads to slower sailing speeds. A low aspect ratio of the keel is simply less effective at producing lift when compared to a keel of the same surface area that is high aspect ratio. This is why racing yachts all have very deep fin keels.

If performance is your top priority, a fin keel will be your desired keel platform. If you want a bit more forgiveness with exploring new waters and will be satisfied with a slower boat, a full keel will be a great platform to look into.