Measuring rig on a sailboat
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Measuring rig on a sailboat

September 8, 2019


[Laughter] [Music] [Applause] an important component to measure any boat is the rig plan which includes the mast the boom and how the two are positioned relative to each other and to the boat since this is the framework that supports the sails for measuring a mast it is ideal to measure when it is out of the boat and horizontal on supports use a 30 meter reel of steel or vinyl covered steel measuring tape also keep on hand a shorter measuring tape or folding ruler a set of calipers large enough to measure the mast sections and a log sheet to record all measurements to prepare the mast for measuring make sure the halyards are removed and replaced with small tag lines so that halyard weight is not part of the measurement when using metric units all rig measurement should be taken to the nearest millimeter the shrouds head stay back stay running backstays check stays and inner-force day if applicable should all be secured and pulled taut toward the bottom of the spar instrument displays and their brackets may be left attached during measurement as can any antennas and electronic or analog wind indicators installed at the masthead take note of the mask construction material the number of spreader pairs runner and jumper pairs and standing rigging material such as composites or steel rod the first step is to gather mass tube measurements that include the mainsail luff distance pea heights of the four stay eye and spinnaker halyard ISP and mass profile dimensions the mass should have two measurement bands of no less than 25 millimeters that designate the limits where the mainsail can be set on the mast they are typically black for clear or white paintings bars or white 4 carbons bars holding one end at the upper end of the lower measurement band which is where the top of the boom intersects the mast the other end is drawn tight to where the head stay intersects the front end of the best the height of the forced AIG is defined as the distance from the force a attachment pin or the intersection point of the centerline of the four stay with the forward side of the mast to the mast datum point that is shear line abreast the mast the practical method of measuring ieg is to measure the distance to the top of the lower measurement band and then add the boom above shear bas measurement shown later in this video if there is an outrigger or tang on which the force a is connected to the mast two additional measurements MW and Geo should also be taken the mainsail luff mass distance P is the distance between the two measurement mast bands in the absence of the upper measurement mass band P is measured to the upper part of the main halyard ship the fore and aft section of the spar at the top band is measured and recorded as MDL 2 with its corresponding transverse width measured at that section and recorded as MDT to the height of the spinnaker halyard ISP is defined as the distance from the mast datum point to the upper side of the halyard ship or the lower side of a halyard ring if one exists note that the ISP measurement is used for both spinnaker and head sail set flying if they’re already in the sails inventory if there are more highly ERDs used while racing the highest one should be measured if the mast is tapered the taper length should be measured as the distance from the bottom of the top measurement band to the point at which the mass while starts to taper to locate the lower measurement band of the mast the boom should be made level and this line extended forward to where it intersects the mast this will be the upper edge of where a 25 millimeter or 1 inch band around the mass should be painted in either black or white to contrast with the color of the mast at the bottom band measure and record the fore and aft sections as MD l1 but remember to include any track that may be fixed to the outside of the spot the transverse section measured as the bottom band is measured as MD t1 and the fore and aft length of the head foil is measured doubled in dimension and recorded as the forced a perpendicular or FSP mass weight MW T and the mast center-of-gravity mcg are not required measurements but are always useful to get when the opportunity is available to measure MW t a calibrated scale is needed with the position of the lifting strap and the scale positioned at where the MCG will have the mast perfectly balanced repositioning of the strap is often needed to find the exact point where the mast and rigging hangs in a horizontal position without touching any supports or other objects mark this point and measure from it to the lower measurement band this should be recorded as mcg to determine the boom above shear or bas there are two methods one is to hang a plumb line from the lifeline that will drop to the shear then run the line across to the other lifeline keeping the string taut and just touching the front of the mast then measure the distance perpendicular from the string to a point that is 45 degrees tangent at the shear record this for both sides and take the average of the two values next measure the distance from the string to the top of the lower band on the mast add this to the previous value and record this sum as bas the other method to determine bas is to make a mark on the mast that is 500 millimeters below the top of the band z mark the distance from the top of the band to the shear a along with the distance to the shear from this lower mark b this is done on both port and starboard sides of the boat then plug those numbers into this equation to determine bas if applicable the length of the bowsprit called TPS or tack Points vinegar is determined by extending the bowsprit to its full length placing the end of a measurement tape at the front of the mast using a level to determine the vertical plane from the end of the spread and then arcing the tape to find the shortest length record this as GPS [Music] the four triangle bass J is determined in a similar way with the end of the tape placed at the front of the mast and the level place where the head stay intersects the deck the small distance between the head stay and the very front of the boat without additions to the hull can be measured with the tape and recorded as SF jey another important measurement is the foot length of the mainsail on the boom the 25 millimeter band shall be painted on the boom where the clue of the mainsail is not allowed past this measurement called E is taken from the aft face of the mass or the mass track to the forward edge of this band boom depth BD is measured as the maximum vertical boom spar cross-section spinnaker pole length SPL is measured from the boat center line to the outer end of the pole when placed horizontally in its normal position and perpendicular to the boats centerline most boats are sloops and have only one mast but the same measurement principles apply to boats with multiple masts such as catches and y’alls see the ims measurement rules in manual for more details 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