At MarsKeel Technology™ the machining of the keel offers the customer the very highest level of accuracy possible in the surface. These keels can be made from virtually any metal in the fin.

The machining of the keel can start from one of three basic beginnings. The beginnings are a fabricated fin, a cast fin or a plate of metal. Each of this group of production methods has its own type of information required. Each will also affect the project timing and cost. There is also a further option in machining; you can machine the bulb as well, regardless if it is integrally cast on the fin or cast separately. As you can see the options are all possible for the customer.

The beginning of the machining process starts with the receipt of a complete production drawing, including an IGES file. Both of these files have to be complete, all dimensions and surfaces defined. The offered drawings will be used to generate one of the following,

(1) If the keel is to be made from plate steel, or a basic fabrication, the offered drawings are used to produce a rough plate cutting drawing, and secondary fabrication drawing. The rough cutting drawing must also include the positioning of clamping points for milling that are removed at the last stage of milling. The preliminary fabrication drawing includes the machining of all joints and their related weld preparation.  The IGES file will be used to create and check the final surfacing program if the fin is to be created from plate steel.

The materials that are available for this process are set by the choices of the designer.

(2) If the machining is to begin with a fabricated fin the offered drawings will be used to produce the initial fabricated fin. The outer surface of the fin will have to be designed and made from plates that are thick enough to allow the machining and still leave the required material thickness on the fin. The IGES file is used for the required surfacing of the fin. The surfacing file is also used in the same way the previous file was used, mill programming and design checking.

The material choice can range from standard Stainless Steel to Armour plate.

(3) If the keel is to start off as a cast part the drawings required are for the generation of the casting pattern. Therefore the required machine tolerance as well as the related shrinkage and possible casting movement must be included in the drawing surface. This is true for both the production of the fin pattern and or the bulb pattern. The only difference is the amount of tolerance required by the different materials and casting methods. The accompanying IGES file is used as before, checking and mill programming.

The material choices are those materials that can be cast.

The size of the part it will be CNC machined will determine the size of the mill to be used. We have a maximum Horizontal Boring Mill table size of 96” X 320” and a maximum crane lift of 25 tons. This machine size will allow us to mill any keel or fin up to and beyond those generally required by the Maxi yachts.

The machined finish surface generally offered from has scallop depth of 0.005”; this is generated by a 0.125” step over of a 1” bull nose cutter. This can be up graded to a mirror finish but it would take many more hours on the mill and would offer as surface that is too smooth for the application of primer and barrier coat products.

Once the machining keel is complete the keel sent to the finishing room where it goes through the following steps,

• It is cleaned of all water based machining oil.
• Etched if necessary with self etching metal primer.
• Coated with 4 coats of Interprotect 2000E.
•  Dry sanded to approx. 180 grit,
• Then additional coats of Interprotect are applied.
• The final stage if required is a wet sanding. The fin and or the bulb can be wet sanded to approx. 400 grit. The final surface id smooth, free of all machining marks and ready for the customer to apply the required anti-fouling paint or surface.

Once the finishing process is complete the keel is sent to the packaging department where it is prepared for shipping to the customer.

Welding and Fabricating: MIG, TIG, Arc and Oxy/Acetylene Stainless Steels, Aluminum, Alloys, Heat Treating, Nondestructive Testing (NDT), Bronze and Submerged Arc Welding (SAW) & Hard-face Overlays.

Typical Machined Keel Fin Materials