Keels

I've been kicking the idea around about adding a wing to the outside of the keels. The propose would be to allow more of the lead ballast to be located lower and also to help dampen roll while under way and at anchor. I latter found that winged keels are also added for performance.  The keels job is to stop the boat from slipping sideways from the force on the sail, and because they will always be sliding sideways some there is water the rolls over the bottom edge.  That flow of water causes an eddy vortex on the other side of the keel and the turbulence created slows the boat. 

Adding a 10" pipe to the bottom of the keel like a torpedo would achieve making room for the lead and it would at lease partially do the same job as a wing. I thing the fabrication time for torpedoes would be considerably less that Ted's wing keel (below) but perhaps not likely to perform as well. My amateur view is that the cross section of a torpedo is considerably more than a wing so so it's going to cause more turbulence. I don't think I'd use a gas bottle because I'd like more metal on the bottom where the punishment is taken. The scrap yard has 8" pipe with 1/2" wall and the locals commonly taper the ends but cutting long wedges and folding the seams closed. That way it could make a gentle transition from the front corner of the keel and again into the aft corner of the keel. A problem I see, and I purely guessing that it's a problem; is that the force of the water flowing over the bottom edge of the keel is greatest where the keel is at it widest, and it is that point where the pipe would present the least surface to prevent the flow from slipping downward. I suppose the pipe could be attached slightly outboard of the keel and that would help. I haven't a clue if a pipe would create less turbulence in the water the does flow over the edge but I guess it to be better than the sharp edges of a wing stuck onto the side of a normal bilge keel. At this point I'd bet we're splitting hairs and fabrication time and durability should have more weight. On the durability point, I think the torpedo is a killer idea provided it's heavy walled steel.

But I keep coming back to building a wing. Just making the foot of the keel out of really thick steel. Brent scared me about banging the wing into rocks while the tide is going out, so now I'm thinking about 1 1/2" plate. Then just let that plate extend out to the side. It would slowly curve out from the front to and follow the shape of the keel so that it stuck out about 12" to the side. I guess you could leave it at that if you really wanted simplicity and at that point you have not done any extra work. But it seams to me that you have the same advantage that you are suppose to get from adding a bottom plate to a rudder. To add lead and more thickness to the wing it's just a matter of adding a plate at an angle from the outside of the wing back to the side of the standard keel. Just cut some holes in the side of the standard keel so the lead can flow through and into the wing.

Scheel Keel   Bulb Keel

Scheel Keel

1960 design by Henry Scheel, the Scheel Keel is a wing like bulb on the bottom of a center keel. The idea gave rise to the bulb keel

Ted's bilge keel with wing tips.

Ted's Bilge Keels with Wings

Ted made winged keels for his BS36. The base is 12 mm (1/2") plate and the round edge 30 mm (1 3/16").  It's a maximum it is 13 inches wide, and a 3/4" round bar give the outside edge it's curve. The top of the wing is about 7" up the keel side at its highest.  The base is at 115° to the vertical of the keel, which means that if the keel is canted out at 25° then the base will be horizontal. In the middle of the keel athwartships is a knee boot shaped 1/4" frame. A plate is welded over the lead and up the front and back of the keel interior to make the diesel tank. The lead was added before the keels were fitted to the hull to insure that it filled the outside of the wing. The inside is painted with POR 15 to ensure seal the welds so the rest of the volume could be used as fuel tanks.  The performance advantages are difficult to determine but several manufacturers rate keel wings and bulbs highly.

Wing keel conversion on Beatrice, a 50 footer from Sweden.

Sten Hellsten's Wing Keel Conversion on Beatrice

Beatrice has a robust wing keel with lead ballast added to the stock keel on a 50 footer.

This is the kind design I had in mind for wings on a bilge keel. We plan to sail in waters laden with snags so I'd not use the bulb on the front that might catch a line, however I really like the skeg extending back so that it protects the full length of the rudder.  The rudder also uses a bottom a wide bottom plate that extends a few inches beyond the thickness of the rudder which should improve it's preformance.

The owner, Sten Hellsten of Sweden reports that there was no perseved performance change with the new keel.  Except of course he can now sit upright and dry out the hull between tides.

Lerouge Yachts Winged Bilge Keel

Lerouge Yachts, www.lerouge-yachts.com designed and tested wing bilge keels and came up with the the pictured keel for a 36 footer.  This is the keel that Ted used as his inspiration.

Magic Dragon

No wings on those keels but they did write a good review of twin keels.  Read it here: www.setsail.com/s_logs/deridder/dragon12.html
 

Folding Bilge Keels

Here is a Polish idea from Dr Jan Anielski at www.steel-yacht.com. Two hinged keels supported by struts that can be manually folded flat to reduce draft if needed by cutting or removing the bolt that on the top end of the strut. A winch line can be attached to the top end of the strut to lift the keel, and a pawl on the strut holds the keel in the lifted position.

Ballast keels may have any profile by adding concrete on the surface on welded reinforcement.

I think it's a cleaver idea for getting off a reef, or navigating the canals of Europe and it might be the best protection for twin keels in ice, but it relies on no skeg and a lifting rudder which exposes the prop, and on impact it concentrates a lot of force on the hinges.

Collecting and Processing Lead

We have been in the business of collecting and processing lead for years.  First for our submarine and now for our sailboat.  Our sailboat lead is almost completely processed from used wheel weights using a wood fired smelter.  See the videos and read more about it here: Wood Burning Lead Smelter.