XXI. Tweaks, Modifications, and Upgrades

Building the Core Sound 20

This chapter will describe some of the upgrades and modifications we've made to enhance the convenience or enjoyment of sailing our Core Sound 20 "Second Wind." Click one of the links below to jump directly to that modification.


One minor downside to using VC Performance paint for the entire hull exterior is that nothing adheres to its teflon-impregnated surface, including vinyl lettering. To display our registration numbers, we made a set of varnished plywood "trailboards," which not only look good, but add some classic nautical charm.


No vessel should put to sea without a reliable means of manual propulsion. We built a pair of 10' oars that stow alongside the centerboard trunk when not in use. Click the link for more details.

GPS / Depthfinder

For casual navigation, we use a Lowrance LMS-520C GPS/Depthfinder unit. It is installed under the thwart so it won't get bumped, sun-baked, or water-logged. We epoxied a tapered block under the thwart to angle the screen slightly upward for easier viewing. The external GPS antenna is mounted atop the centerboard trunk.

The skimmer-style sonar transducer is installed just behind the aft bulkhead, offset slightly to starboard (opposite the port-side centerboard), in a shoot-through-hull configuration. We used a router to carefully cut a hole in the wood hull (without removing the thin layer of fiberglass and paint on the bottom), reinforced it with 7 layers of 6 oz. fiberglass, set the transducer in place (with a brick to hold it down), and poured raw epoxy around it. The transducer cable runs through the aft bulkhead, into the port-side seat locker, and out the seat face (under the thwart) to connect to the unit.

12V Power Station

The GPS/Depthfinder runs on a Werker AGM deep-cycle battery (12V 18Ah). The battery is mounted in a small plastic box that fits snugly inside the forward port-side seat locker. A battery switch allows us to isolate the battery when re-charging, and a 12V accessory outlet allows us to power devices such as a flood light, bilge pump, or cellphone charger. The box also holds a small battery charger that automatically selects the proper charge or maintenance mode (CTEK model US 800), permitting us to re-charge and maintain the battery from any standard outlet.

We used Ancor 16-gauge marine wiring, heat-shrink tubing, waterproof connectors, and a terminal strip to make high-quality connections that all stow neatly inside the box and should survive the elements. The box can be easily disconnected and removed from the seat locker for use as a portable power station ashore. Total weight is 15 pounds.

This is the second version of our 12V power station. The prior version used a larger, heavier flooded battery housed in a taller box. Although it worked very well, it was too tall to stow inside a seat locker. As a result, we had to stow it on the cockpit floor or under the foredeck. Either way, this meant that the cord connecting it to the GPS/Sonar unit was visible and in the way of our feet.

When designing this version, we still wanted a tidy, self-contained unit with a carrying handle. But we took care to size the box to fit inside the seat locker. This offers several advantages: We can lock the battery inside the seat while traveling (our seats have lockable hasps), the battery cannot fall out during a capsize, and the connection to the GPS/Sonar unit is no longer visible or in our way (the cord is hidden inside the seat). It's a definite improvement.

Tiller Tamer

A tiller tamer secures the tiller so the captain can let go of the helm without deviating off course, making it easier to attend to other matters, such as tweaking sail controls, preparing docking fenders, or freeing tangles in the main or mizzen sheet. Drawing inspiration from the "Small Improvements" section of Duckworks Magazine, we improved on Gary Blankenship's homemade design by incoporating a stainless steel hook and a short loop of 5/16" diameter bungee cord. We also eliminated the cam cleats and eyestrap.

Our tiller tamer consists of the following:

  • two 1/4-20 x 2" stainless eyebolts, with matching washers and nuts
  • one heavy duty 5/16" stainless eyescrew
  • one stainless S-hook
  • two pieces of 1/4" diameter braided polyester line (one 18" long, one 5' long)
  • 8" of 5/16" diameter bungee cord
  • one small clamcleat

The eyescrew is mounted under the tiller, exactly 3" forward of the cockpit coaming. The clamcleat is also mounted under the tiller, at least 8" forward of the eyescrew, but leaving enough space for a normal handgrip. The stainless S-hook is attached to a small loop of bungee which is tied to the 1/4" diameter line. The line leads to the clam cleat where we can adjust the tension on the tiller. We call this the "adjustment line."

An eyebolt is mounted on each side of the cockpit, tucked under the side decks (out of plain view) and thru-bolted through the aft bulkhead stringer. A length of 1/4" diameter line runs between the two eyebolts, with enough slack to pass a small loop of it through the eyescrew under the tiller. (We call this line the "stabilizing line" because it provides the lateral resistance that stabilizes the tiller underway.)

To use the tiller tamer, we loop the stabilizing line through the eyescrew and clip it to the S-hook on the end of the adjustment line. The S-hook exerts enough friction to prevent the helm from wandering. Tightening the line increases the amount of friction and stiffens the steering. The tension is very easy to fine-tune thanks to the bungee.

The best feature of our tiller tamer is that it holds the tiller securely at all times, yet still allows us to steer at a moment's notice without releasing or adjusting anything. We love it.

Folding Tiller Hinge

Since our tiller protrudes so far into the cockpit, we installed a hinge that allows the front half to fold up. This gives us more space when moving about or rowing, and also makes it easier to steer from a standing position as we approach a dock or shore. To make the hinge, we used three 5/16" stainless bolts and some stainless flat bar. The two pieces of flat bar are each 5" long x 3/4" wide x 1/8" thick. We snugged up the bolts just enough so the folding tiller handle stays in whatever vertical position we leave it.

Raising the tiller handle also tightens our tiller tamer (see above), causing the steering to lock more securely in position. Pretty neat.

Sleeping Berth / "Sun Deck" Panels

To make it comfortable to sleep or sunbathe onboard, we built four drop-in berth panels to fill in the forward footwells, resulting in a spacious sleeping berth or sun deck. Combined with the surrounding seat tops and beneath the foredeck, the panels produce a lounging area that is 6'6" long.

Port-side Berth Panel

The port-side berth panel is a single panel approximately 36" long x 12" wide. This is the perfect size to fill in the port-side footwell, leaving just enough legspace leftover for one person to sit up normally. It is also exactly the right length to span the seats in the aft cockpit, so when not in use as a berth panel, it is stowed in place against the aft bulkhead where it serves as a bench seat. In that location, we use a bungee cord and hook to attach it to an eyeloop screwed into the keel batten. This prevents the panel from bouncing around in a rough sea or while trailering.

Starboard-side Berth Panels

The three starboard-side berth panels are each approximately 14-5/8" long x 18-3/4" wide. These smaller panels can be stacked and stowed easily under the foredeck. They also permit flexible layout options. For example, we can use only one panel to accommodate a napping child or to serve as a handy lunch table, while leaving the rest of the leg space open for normal sitting and moving around the boat. One panel is also the perfect size for a bilge seat.

To make a bilge seat, we added a tapered foot to one of the panels. The tapered foot matches the deadrise of the hull floor, allowing the panel to sit perfectly level. The resulting seat is high enough to keep one's backside out of any residual bilge water, but low enough to offer reasonable shelter from wind and spray, especially if used with a dodger. Seated this low, one can also safely ignore the main sail swinging back and forth overhead during tacks. Combined with a GoAnywhere2 seat from West Marine, this is the coziest spot on the entire boat.

Some builders make floorboards that raise to become berth panels like ours. Lifting-floorboards are neat because they stow right on the floor and can be designed so that all of the cockpit leg spaces become sleeping berths, including the spacious area aft of the mizzen thwart. But we chose to forego floorboards for several reasons. For one, we wanted to avoid adding unnecessary weight, especially since it is unlikely that we will ever need to sleep several people onboard.

The other reason we rejected the floorboard solution is because we love the convenience with which we can sweep the (unobstructed) bilge clear of dirt, debris, and water. We keep a small shower squeegee/scraper onboard, which we use to sweep bilge water back toward and out the Anderson Bailer while underway. This keeps the hull interior clean and dry. Floorboards would get in the way of this operation, so instead, our berth panels will stow neatly under the foredeck.

Details for interested builders: Each panel is framed with 1 x 2 pine boards, topped with 1/4" thick Okoume plywood. A piece of 1" x 1" aluminum angle stock (1/8" thick) is attached to each end to make a lip that rests atop the centerboard trunk and seat top. This eliminates the need to attach a wooden stringer (support ledge) to the face of the seats and centerboard trunk as others have done. The panel frames are screwed and epoxy-glued together, and coated in three coats of epoxy, then primered and painted. On the starboard-side panels, each aluminum lip is attached by three #8 screws (2" long) which run through the framing members, plus two #8 bolts (thru-bolted), making a total of five fasteners per lip, spaced approximately every 3-1/2" on center. This produced panels which are light, easily stowable, and very stiff. A load of 200 lbs. causes almost no flex to the panel frame and no distortion to the aluminum lips. For the port-side panel, we added a bit of thickness to the frame because it spans such a large unsupported distance (3 feet) and we attached aluminum lips on all four sides so it can be used both as a berth panel and as a bench seat.

Simplified Centerboard Downhaul

The plans call for a complicated shock-cord and tackle to allow the centerboard to "kick up" when it hits an underwater obstruction. Though effective, we never cared for it. Besides needing to clear it out of the way of our sleeping berth panels (above), the shock cord would stretch (counter-productively) whenever we tried to lower the board by pulling on the downhaul. More often than not, we had to grab the head of the centerboard and manually pull it into position, then cleat off the elastic downhaul to keep it in place.

To improve the downhaul without sacrificing the centerboard's kick-up function, we replaced the shock-cord and tackle with a non-elastic downhaul that runs from the centerboard head, down through a stand-up block, then directly aft to an Autorelease Clamcleat (model CL257 - the same cleat used for the rudder blade downhaul) mounted on the thwart. If the board strikes an object, the cleat automatically releases (at approximately 30 lbs. of force), allowing the board to kick up. The cleat can be reset by simply snapping the break-away portion back into place. This new setup makes it much easier to lower the centerboard from the helm, with no need to go forward to pull on the head of the centerboard. It also reduces clutter by eliminating the extra rigging alongside the trunk, clearing the way for our drop-in berth panels.

Compass and Mount

A good compass guides a boat safely in low-visibility conditions, provides a vital back-up to fallible electronics, and makes it much easier to find and maintain an efficient sailing angle in areas with few prominent ranges or landmarks. It also makes tacks conveniently repeatable. While beating to windward, finding the right tack is as simple as turning 90-110 degrees across the wind from your present heading.

Finding a good spot to mount a compass in the Core Sound 20 is a challenge. Others have mounted a compass at the forward edge of the centerboard trunk (where it meets the forward seat), on the forward cockpit coaming (nearer to eye level), on a mounting bracket just aft of the mizzen thwart, or in the seat tops to either side of the mizzen thwart (in which case, you need two compasses, one for each side). None of these options seemed ideal to us. The first three all made it difficult to read the compass (either too far away to see clearly, or so close as to cause parallax error), while the fourth seemed too costly and intrusive.

After a lot of experimentation, we finally settled on a location that has proven ideal for our needs. We mounted a Ritchie Voyager RU-90 compass just forward of the mizzen thwart, alongside the centerboard trunk.

In this location, the compass is near enough to read without glasses or squinting, yet far enough forward to read the degree heading accurately. Since it is almost directly over the centerline of the boat, it is also easy to install in proper alignment to the bow. The helmsman can read the compass accurately from either side of the boat, even when hiking out on the side decks. One can also lean forward and "top-read" the compass card to take quick, rough bearings on natural ranges or landmarks even if they are not directly off the bow (i.e., it can be used a bit like a hand bearing compass, though not as accurately). Best of all, tucked between the mizzen thwart and centerboard trunk, it does not snag the main sheet or obstruct seating space.

Before committing to this location, we tested to ensure that the nearby GPS antenna and various metals (aluminum mast, stainless hardware, etc.) would not affect the compass's accuracy. Only our galvanized steel anchor and a small tool set caused deviation, but both are stowed far away from the compass, negating their effect. We built the compass mount by epoxy-laminating five layers of 3/8" Meranti plywood into a hefty block, which we bored out to accommodate the compass. We routed a small (1/2") lip on one end of the block that wraps under the mizzen thwart just far enough to accommodate fastners. We attached the mounting block by driving two stainless screws into the cap rail of the centerboard trunk, and three more into the underside of the mizzen thwart. Finally, we used a laser line to align the compass perfectly parallel with the boat's centerline and secured it in place.

Anchor Box / Storage Drawer

There's a lot of room for storage under the forward seat, but the hull deadrise (slant of the hull) is sufficiently steep that gear tends to shift around while under way. Drawing inspiration from Dale Niemann, who implemented a similar solution on his Core Sound 17, we built a custom-fit storage box that matches the hull deadrise. Since the bottom of the box is slotted to ride on one of the hull reinforcement battens, it cannot shift around. This makes it the perfect place to store the anchor and rode.

Heavy duty handles on the front and back of the box allow easy carrying, and a 1/2" drain hole in the lowest corner lets out any water that accumulates when stowing a wet anchor rode. Previously, we carried our anchor and rode in a plastic bin under the forward deck (atop the seat). The anchor box frees up that space for stowing other items. It also carries the anchor weight lower in the hull, which improves stability.

We painted the exterior sides and top edges of the box, but left the interior and the bottom unpainted. That way we can quickly re-coat the epoxied interior and bottom if the box begins to scuff from hard use. Later, we added six little tap-on "furniture sliders" to the bottom to help the box slide in and out smoothly, without scuffing the floor. The sliders are a nice refinement.

Removable Gear Caddy

There are several small items we like to keep within reach while sailing, but which often get in our way as we move about the boat. To address this problem, we built a removable gear caddy that hangs on the aft edge of the centerboard trunk and can be quickly removed to stow inside one of the seat lockers.

The caddy is just large enough to accommodate the desired items: a pair of binoculars, a compressed air horn, a small LED flashlight, and an anemometer (wind gauge). A quick-release hanger on the side of the box also holds our portable VHF radio in close reach. With finished dimensions of 5-3/4" wide, 6-3/4" tall, and 4-5/8" deep, the caddy is small and non-intrusive so it won't bump our shins or get knocked off as we move about.

The quick-remove feature of the gear caddy comes in very handy. We can stow the gear easily in a seat locker for theft-security or while in transit, yet still have the items quickly onhand while sailing. It also allows the caddy to be moved out of the way to access the oars, which stow alongside the centerboard trunk. To permit quick removal, two screws are permanently embedded in the back of the centerboard trunk, with the heads of the screws sticking out approximately 1/4" (the thickness of the back of the caddy). On the back of the caddy, we drilled two oversized holes (slightly larger than the diameter of the screw heads) and cut a small groove (the thickness of the screw shaft) in the 12 o'clock position. To attach the caddy, we slip it over the screw heads and tug downward gently. This engages the screw shafts into the grooves, "locking" the caddy into place so it cannot fall off (much like the mounting slot on the back of some picture frames). A gentle push upward "unlocks" it again for removal.

Hard Dodger

It took a long time to settle on a design for the spray dodger. A soft folding dodger seemed ideal because it would setup quickly, yet fold away when not needed. But building a soft dodger did not seem feasible given our lack of experience with sewing and with bending metal tubing. Having one made professionally would be expensive, so we decided to try building a hard dodger first, using leftover plywood and epoxy.

We wanted the dodger to look like it belonged on the boat, so we began by mocking up the design in cardboard. After a great deal of cutting, taping, measuring, and adjusting, we settled on an aesthetically pleasing and functional shape, which we then transferred to plywood. As designed, the leading edge of the roof is approximately 5-1/2" above deck. The roof extends aft for 22" and rises to approximately 14" above deck at its highest point. For strength and roof curvature, we laminated a mahogany roof beam that has approximately 3/4" more crown than the deck. This curvature helps the roof shed wind and water. Together with the gentle inward slope of the sides, it also prevents the dodger from looking too "boxy" against the rest of the boat's lines. The bottom is a curved plywood base cut to match the perimeter of the coaming for a nice, snug fit to the deck and cockpit.

After aesthetics, unobstructed visibility was our top priority. We designed the dodger so the aft edge of the roof is about even with the tops of our shoulders when we are sitting up on the seats. This allows us to look right over the top of it to spot oncoming boats or other obstacles. When the wind and spray kick up to uncomfortable levels, forward-seated passengers can either lean forward and hunker down (sitting with their elbows on their knees) or sit on the floor to enjoy full sitting headroom (using the bilge seat described above). On hot days, the dodger also shades the first few feet of the cockpit, offering reprieve from the sun for anyone who sits or lays beneath it.

To mount the dodger, four heavy-duty (5/16" diameter) bungee cords wrap down under the deck and attach to a set of small stainless hooks. The bungees hold the dodger securely against the deck. The base of the dodger fits snugly around the cockpit coaming and is lined with 3/16" thick "Super Firm Sponge Tape" (closed cell weatherstripping tape), which cushions the deck from scuffing and provides grip to prevent the dodger from wiggling around. To brighten the interior, we painted it Whidbey White to match the rest of the cockpit. The exterior is varnished to match the deck.

Hanging Storage Box

The storage area beneath the CS20's forward hatch is enormous. In fact, it is so spacious and deep that it is difficult to reach whatever is stowed there, so we never made use of it—until, that is, we built a storage box that hangs beneath the hatch lid.

The rim of the storage box is sized to match the internal dimensions of the hatch rim, minus 1/8" in each direction for clearance. The rim also forms a 1/2" lip all the way around the exterior of the box, which allows it to ride on a pair of 3/16" thick strips screwed inside the hatch to form a ledge. The ledge strips are made from a 3/16" thick cutting board to keep them light, waterproof, and scuff-resistant.

When building the storage box, we gave particular thought to our 4-pound Fortress (Danforth) anchor. Despite its light weight, the wide head, long shaft, and pivoting flukes make it awkward to handle and stow without scuffing the boat interior. Thus, we carried it disassembled and rarely used it despite its superb performance. We have always known that the assembled anchor fits through the forward hatch, but we were reluctant to stow it there for fear the flukes would damage the hull while tossing about. The storage box eliminates that fear: Now, the anchor head rides in two grooves in the box's rim and the shaft extends through a hole in the box's bottom. This holds the anchor securely in place, just beneath the hatch lid.

A pair of rope handles just under the rim makes the box easy to install, remove, or carry. A small rotating cover allows us to cover the hole for the anchor shaft if desired. Another small hole in the box bottom allows the hatch hold-down bungee to pass through up to the hatch lid. Final dimensions of the box are approximately 13-1/4"L x 15-1/2"W x 14"D, providing just over a cubic foot of storage space, all within convenient reach.

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© 2008, Wesley Kisting

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