Sheetlines System

Bow Block Sheetline System

 

Description
This is a variation of the EC12 sheet line system with modifications for a low friction delivery system to the booms. A tension line is used here to hold the bow block in place rather than a hard mount of the block. This requires periodic maintenance checks for fraying lines at the bow. An emergency line is in place should the tension line break or be lost. The bungee system is to keep tension on the sheet lines and is so designed for a short return with the advantage loop through the travel block. The travel block will move 1/2 that of the winch line. The collector distributes winch line movement to the sheets and the bungee. This movement is 30" from the bow block to inside the tower strut. Blocks are used to reduce friction and guide lines to their terminals. The diagram above will be supported with photos below.

Jib and Main Sheet Guide Blocks

The fairleads through the deck were to be at stations 33 and 65. Below these points a structure was fashioned to mount the blocks that would guide the sheet lines from the winch line collector through the deck. The structure seen here may be overkill, however, twisting failure of either of the 32 and 66 ribs would be catastrophic. The king plank will be the final piece to hold the structure together.

   

Whereas, the blocks are not visible when accessed from the hatch area, removal of the block is easily accomplished in the blind. The orange cone washer is soft and found in the plumbing section at a good hardware store. They are trimmed to fit over the opened eye screw and retained against the rib. The system was tested in the blind with no problems removing the block and installing it by two different means. One, is to press the shackle of the block against the washer and slide the block off the eyelet. Second, is to pull and slide the washer off the eye screw then remove the block. Putting the block back on the mount was as easy. It is suggested that whatever system you use, some repetitive training would help the memory in the future.

Note: When installing the king plank and the deck sheet, protect the assembly from glue droppings.
Here is the installation procedure for the system shown here. There are many ways to do this so, let's just say this is representative.

Bow Block and Winch Line

The block is held in place by a tension line that terminates at a cleat on the port side of the main hatch liner. An emergency line loop passes through the bow eye, is held in place with Silicone sealant and terminates outboard of the cleat on the hull. This line can be used to thread another tension line when one is lost.

   

The winch line is installed in the end groove of a RMG 8 groove 32mm SDS (Step Down Spiral) drum. The winch is programmed for the maximum 11 turns. When at close haul the line will roll a bit over three turns on the axel of the drum. A mark for the collector loop is made at the bow mark and the winch is then programmed to stop sheeting out at 31" just as the mark moved over the Delrin rod in the strut tower. This will leave about two wraps on the drum at full sheet out. A 1/4" collector loop is prepared at this mark to be free of the bow block at close haul and of the trim servo block at full sheet out and full trim out.

This is the calibration of the sheet line system and the rest is a matter of routing. During the programming of the RMG winch it is recommended to disable the battery protector in the final step.

Jib Trim and Sheet Line

Attached to the collector loop, the line runs back through the trim servo block, through the tower strut and up through the station 32 block. Leave an ample line length over the side for when the rig is installed the first time.

Main Sheet Line

Attached to the collector loop, it runs straight back and up through the station 66 block with ample length over the side. 

   

Bungee Line and Travel Block

Install a slightly open eye screw centerline near the bottom of Rib 41. Attach a line to the collector and close haul the winch line. Mark a terminal point on the line at the eye screw so that the travel block is just forward of Rib 45. Make the terminal loop and attach with the travel block in the line and the shackle facing aft. Run the winch to full sheet out.

Install an eye screw on the main sheet block mount to port on Rib 66 and hang a block on a hook. Install another near the port end of Rib 41.

Prepare a bungee line to connect to the travel block shackle and pass it through the station 66 block. Prepare the terminal end with a hook and adjusted for only slight tension on the line when hooked to station 41.

The bungee size used here is 1/8" and because of the line length and short movement of the travel block there are no high tensions on the bungee at close haul. The hooks at stations 66 and 41 can easily be handled in the blind for maintenance. To lessen expansion of the bungee, the terminal end is unhooked and hung on the tension line cleat for storage.