Documenting Bowsprit & Lifeline Measurement

[Vento Solare]

The measurement tools used to verify that the Bowsprit length and Lifeline deflection are compliant with class rules are shown here, along with instructions on how the tools are used.

Bowsprit Measurement Tool
Bowsprit measurement was added to the measurement checklist when it was determined that there was a wide variation in the extended sprit length across boats. The measurement is intended to verify that no boat exceeds the J/Boats design specification of 66 inches when the sprit is fully extended. The 66 inch measurement points are the forward edge of the stem head fitting, and the load bearing surface on the sprit. The load bearing surface is either the forward edge of the U-bolt where the tack line turning block is attached, or the forward edge of the sprit for configurations with a dyneema loop & ring anchored at the front of the sprit.

Sprit Tool overall

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Forward end of tool hooks into U-bolt, of hole in end of sprit

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Aft end of tool located by stem head

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The tool provides repeatable measurement without the use of a tape measurer. The critical dimension is the overall length of 66 inches. The other dimensions are not critical, allowing the tool to be fabricated from scrap material. It consists of a PVC or Wood board that is 66 inches long. On one end, a cross piece is attached with screws. There are two screws used as guide pins that are "hooked" into either the U-bolt, or the hole at the end of the sprit, depending on configuration. These screws should be located 1 inch & 2-3/8 inches from the side of the 66 inch board. They are on opposite sides so the screw at 1 inch may be used for the U-Bolt, and the screw at 2-3"8 may be used for the hole in the end of the pole.

Using the Sprit Measurement Tool
One person will pull the pole out. A second person places the tool fore & aft with the pole retracted, hook the U-Bolt or end hole as appropriate. Hold the tool and let is slide through your hand as the pole is slowly extended. When the pole is fully extended, move the aft end by the stem head fitting. Anything that allows the end to swing without touching the stem head is too long.

Remedy for Sprit too long

• The sprit extension may be shortened by either fixing a limit line between the aft end of the pole and the padeye on the aft bulkhead. The line is adjusted and shortened as needed to limit the sprit extension.
• An alternate method uses shims on the aft end between the rubber limit stop and the collar on the forward bulkhead. Trim the shim to the desired length and tape it onto the pole.

Lifeline Deflection Measurement Tool
Lifeline deflection measurement is in accordance with World Sailing Offshore Special regulations specified parameters. The measurement verifies that the lines are properly tensioned with a maximum of 2 inches for the upper and 4-3/4 inches for the lower lifeline. Deflection is measured on longest section of the lifeline, forward of the stanchions used for entry gates. Should lifeline cushions be installed, measure the first section forward of the cushions. A 4 kilogram weight (8.8 pounds) is hung with a hook at the center of a span to be measured. The weight may be any suitable collection of dense material such as lead fishing weights, iron dumbbells, etc.

The deflection measurement tool is fabricated using a 48 inch wooden dowel, a 1 x 2 x 6 inch block and two cable clamps sized the same diameter as the dowel. The plastic clamps used for restraining electrical wires works well. The block should be labeled with a reference line at the top, a line 2 inches below that marked "Upper" and a third line 4-3/4 inches from the refence labeled "Lower". The clamps are screwed into the opposite side of the block and tightened so the the block is able to slide up and down the dowel with some resistance.

Lifeline tool slider front

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Lifeline tool slider back

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Simulated Upper Reference

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Simulated Upper Measurement

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b]Simulated Lower Reference[/b]

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Simulated Lower Measurement

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Using Lifeline Deflection Measurement Tool
Measurement is performed on boat upper and lower lifelines both port and starboard side. Locate the longest lifeline span, and if covered with a cushion, the span just forward of it. Make sure the gates are closed and hang the weight in the center of the span. Put the dowel on the deck against a stanchion and slide the block to line up the reference line at the point where the line being measured exits the stanchion hole. Hold the block in place and move the dowel placing it on the deck by the weight to verify deflection at the weight is no greater than the limit line as appropriate for the upper or lower lifeline. Should the deflection be too long, the weight should be removed, lifeline turnbuckles tightened, and measurement reverified. Repeat the process on upper and lower lifeline port & starboard side.