We have made two important improvements to Duet's anchoring platform: A modified bow roller and a heavy-duty mooring bitt.
Nordhavn 46's are generally delivered with a bow roller designed to hold one anchor. A second roller is present, but it is designed to bring a mooring line aboard, not to hold a large anchor. Kato Marine in Annapolis modified the bow roller to hold two anchors (our primary, a 105 pound CQR, and our secondary, a 60 pound CQR). Two important design constraints had to be met: The bowroller fits within an aperture on the foredeck. This limitation on width made it impossible for two large CQRs to sit side-to-side. We considered extending the roller so that the flukes of the secondary would sit well forward of the primary's. This approach would have increased loads on the deck, and was rejected. Instead, Kato Marine constructed a cantilevered assembly for the second hook. When the secondary anchor is retrieved, the rollers pivot up and create room for the primary anchor. The two anchors nest together quite securely, and there is no motion in a seaway. This is our second experience working with the folks at Kato on a custom metal project; we are always impressed with their responsiveness and fine attention to detail.
A second improvement was the installation of a mooring bitt on the foredeck. Nordhavn 46's usually are delivered with two moderately sized foredeck cleats. These are useful at dock, but less convenient for anchoring maneuvers, especially in rough weather. We desired a very strong attachment point for snubbing lines that could be run to our chain rode. Also, we wanted a secure place to belay the rode of our 24 foot Paratech sea anchor. This rode consists of 3/4" braided nylon with a 25 foot tail of 1/2" mooring chain to eliminate problems of chafe where it comes on board.
We asked Schoellhorn-Albrecht in Missouri to design and construct the mooring bitt. Most of Schoellhorn-Albrecht's work is commercial and military. After perusing their stock design schematics, we agreed on a 'scaled-down' version that would be right for our boat. The bitt was custom cast as a single unit out of stainless steel. The post is 6 inches in diameter and stands 11 inches tall. Two 2 inch horns protrude from the sides, approximately half way up the post. The base is 12 inches square, much larger than the post itself, to allow good load distribution. The unit weighs 90 pounds, and is very robustly constructed. 4 11/16" holes in the base accommodate the 5/8" mounting bolts. The folks at Schoelhorn-Albrecht were a pleasure to work with and they are meticulous.
The best location for the mooring bitt was directly behind our Maxwell 3500 windlass, right where the footswitches were installed. The footswitches were removed and the holes filled with West System epoxy (105 resin and 209 very slow hardener) thickened with 404 high-density filler. The footswitches were then relocated to the right side of the deck, slightly forward of the bitt.
The base of the bitt consisted of an outer flange surrounding a central concavity (like the lid of a shoebox). This design allows flexibility in mounting the bitt to surfaces which are not perfectly flat (like a boat deck!). The base of the bitt was filled with thickened epoxy. The bitt was then positioned on the deck while the epoxy cured. When complete, the cured epoxy insured a good fit, and even load distribution, between the base of the bitt and the contoured foredeck. To insure that we could remove the bitt after the epoxy cured, the foredeck was covered with duct tape. Once cure was complete, the bitt was 'peeled' off the deck. Duct tape separates easily from cured epoxy. Any rough edges where the epoxy protruded beyond the bitt's base were carefully sanded down.
The backing plate for the mooring bitt consists of two components: A 15 inch square piece of 3/8 inch thick aluminum is backed up to a 17" square section of 3/4" marine-grade plywood, which is backed up to the deck undersurface. Since Duet's foredeck is robustly built (it is1.75" thick), the backing plate arrangement is over-engineered for anticipated loads. Construction of the backing plate and final bitt attachment proceeded as follows:
The plywood component was secured to the undersurface of the foredeck with wood screws and a heavy layer of thickened epoxy. The epoxy was necessary to insure even load distribution between the plywood and the irregular undersurface of the foredeck. The wood screws were tightened down until epoxy just began to ooze out the edges. Once the epoxy began to cure, but while it was still soft, the edges were smoothed and filleted.
After the plywood cured, oversized holes (1 1/4") were drilled through the foredeck for the mounting bolts. The holes were re-filled with epoxy, and the aluminum plate was secured to the undersurface of the plywood. Finally, 5/8" bolt holes were drilled through the center of each cured epoxy plug, and through the aluminum. Each mounting bolt is surrounded by an epoxy sleeve which protects the deck core and plywood from possible moisture penetration. Finally, the bitt was bolted down with a heavy bedding layer of 3M5200. Here is a picture of the final product.