As the front-runner in Keel production, we have developed a cost-effective, yet practical, alternative to complete Keel refits.
MarsKeel Torpedo Bulbs™, an innovative Keel modification concept, provides enhanced performance and stability for the performance-oriented sailor or draft reduction for the cruising enthusiast.
For over a decade sailors have been asking Mars Metal Company for the solution to these problems. Many of these sailors wish to redesign and replace their boat’s entire Keel. With MarsKeel Torpedo’s, this costly procedure becomes unnecessary.
Below is a general illustration drawing showing the dimensions that are needed by MarsKeel Technology to be able to generate an off cut weight, casting weight and a price for your requested draft reduction.
Click above image to enlarge | Download drawing as a PDF
- Article: Cut your Keel, Keep your Boat
- Draft Reduction Chart (PDF)
- Download Draft Reduction Drawing (PDF)
MarsKeel Torpedo Bulbs™ are available in weights from 50 pounds to over 1,000lbs (455kg) per side. To increase stability in most cases, an addition of 10-15% more ballast will correct the most tender sailboats (ie: 3,000 lbs (1364kg) Keel plus 300 lbs (136kg) Bulbs = 10% more @ 3,300 lbs (1500kg) total.) However, there may be some vessels that require more or less ballast. The redesign calculations may be adjusted to meet the needs of the specific boat.
Having decided to reduce the draft and once the desired draft reduction is established (usually a minimum of 12″ and a maximum of 24″), along with four other basic measurements, our in-house CAD computer systems will determine the amount of lead to be removed and the weight and size of the MarsKeel Torpedo Bulb™ to be added. For every 12″ removed, an additional percentage of ballast is added to maintain stability as before (see factoring chart).
A template (of the Keel base after cutting) ensures that the contoured MarsKeel Torpedo Bulb™ cast matches the keel’s foil section above the tip cord.
MarsKeel Torpedo Bulbs™ run forward and aft, incorporating the entire length of the new keel’s tip cord. The bulbs are positioned horizontally and parallel to the water line. If desired, the bulbs are made to travel aft of the trailing edge, increasing the keel’s lateral resistance, and thus reducing vortex drag.
MarsKeel Torpedo Bulbs™ come fully bored and countersunk with the necessary high-grade 18/8 Stainless Steel threaded rods, hex nuts, and flat washer hardware for easy attachment to the Keel.
Finish by fairing the MarsKeel Torpedo Bulb™ with epoxy to the existing Keel and filling all countersinks. Paint the unfinished metal with epoxy base primer paint. Complete with applications of anti-foul paint.