Ensign Project: Installation of thru-deck Spinnaker Blocks

Material List

• 2 Harken Thru Deck Dingy Blocks (H046)
• 2 Harken Hexarachet with Post and Shackle Attachments (H009)
• 2 Harken Swivel Post Block Springs
• 2 Cam Cleats
• 2 Small Bullet Blocks
• 2 Small Stainless Steel Eye Straps
• 2 Medium Stainless Steel Eye Straps
• Spinnaker Sheet/Guy Lines (50 ft. each)
• 2 Custom Deck Mounted Seats/Wash Guards.
• Miscellaneous Stainless Steel Fasteners and Washers

 

Installation Tools and Aids

• Saber Saw with narrow blade
• Cardboard Cutting Template for thru deck cutout
• 6 ft. length of 1/4 inch threaded steel rod to pass line forward through underside of deck
• Of course, duct tape

 

Installation Instructions

Much of the material selection and installation instructions came from an article Installing Thru-the-Deck Spinnaker Sheets, by Bob Rude, Ensign Fleet 4 Newsletter, Narragansett Bay, RI. Additional guidance and information was provided by Bruce Blackie, former Captain, Ensign Fleet 72, Saratoga Lake Sailing Club.

 

 

Most of the material selection is straight-forward, however, line and sister clip selection can vary.

One consideration is the added weight that these two items will have on the spinnaker's performance. Local sailing conditions may dictate the size and strength of spinnaker lines. Ensign Spars material lists indicates a 5/16 inch line at 45 feet, which may in fact be best suited. However, we opted to use a 1/4 inch (6mm) line with a higher breaking strength. We also found that a line length of 50 feet was more sufficient for our installation. A small diameter line allows for a smaller, less heavier, sister hook. Also, color-coding sheets (red/green) is always good practice.

The deck mounted seat/wash guard is optional, but serves to protect against water spilling from the deck into the thru deck block opening.

 

 

Using the actual block, not the metal cover plate, cut out two seats/wash guards. We used 3/4 inch mahogany and rounded all corners. Make sure that the block fits snugly, and that the block turns freely. Avoid forcing the thru deck block into the seat/wash guard opening, which may distort or impair the functioning of the thru deck block. With the thru deck block fitted to the seat/wash guard, pre-drill holes for mounting screws.

 

 

Once the seats/wash guards are made, make a cardboard template of the inside rectangle. Use this template to outline the area to be cut from the deck. We positioned the forward edge of the cutout using a 12 inch offset from the aft end of the coaming.

 

 

We aligned the outside edge by placing the seat/wash guard on-line with the edge of the non-skid surface. Positioning the seat/wash guard at the forward line and aligned with the edge of the non-skid border, trace a line at one of the inside corners of the seat/wash guard. Then, use the cardboard template to trace the entire cutout area. Note: if you decide to locate the cutout differently, it may alter the length of line for spinnaker sheets.

 

 

Having traced the cutout on the deck, drill pilot holes at the diagonal corners (below). Using a narrow saber saw blade, make your cut.

 

 

Then dry fit, and make necessary adjustments to the cutout (below).

 

 

This is when the threaded rod and duct tape are used. The steel rod is strong enough to penetrate the rigid foam at the underside of the deck, but still flexible enough to bend to the correct placement. Also, the steel threads, when worked in a saw motion, cuts a channel through the foam flotation for the spinnaker sheet lines to pass through. Work the threaded rod from the under the coaming, pushing aft toward the cutout. Having another person to provide sight/sound bearings is helpful in locating the cutout. Note: it is important that the channel be placed in alignment with the under coaming bullet block (details below). Once the rod has cut the channel, feed the line through the thru deck block, making sure that it is fed through the top and using the correct line color for the side of the boat you are working on. Take the end of the line that is through the bottom and tape it to the threaded rod. Then draw the rod, with line attached, back to the underside of the coaming. Note: make sure that the channel in the rigid foam, which the line will pass through, is sufficiently wide and at an correct angle to allow the line to pass freely.

 

 

Next, install the bullet block at the underside of the coaming, at a location approximately aft of the winch mounts. You could improvise this piece of hardware. The idea is to suspend the spinnaker line and keep it uncluttered and unobstructed from the shelf storage.

 

 

Next, install the hexarachet blocks. We positioned them aligned vertically with the edge of the under coaming shelf, at a height of 2 to 3 inches above the shelf edge. We through-bolted eye straps to the cabin bulkhead, using fender washers on both sides. Using the block springs supports the blocks in a lateral position when line tension is released, so that they don't go limp. The cam cleat use and placement is a personal choice. We placed it at the bottom, on the face of the coaming, in a position where the spinnaker line cleats upward, and where the line would not rub against the wood.

 

 

Finally, only when all of the assembled parts have been installed, dry fitted, and tested (and retested) do you bed and mount thru-deck block.

 

 

Contact us if you'd like to learn more about Ensign sailing.