INTERNATIONAL 420
CLASS ASSOCIATIONRIG INSPECTION GUIDEVer. 1 ‐ 07/2008

INTRODUCTION
This guide is meant to help standardizing the inspection process at the 420 Class main events.
Class Measurers are encouraged to improve on the described process, but at least they should
follow this basic pattern to ensure that rig inspection is done properly and on the same quality
level each and every time. It is essential that the required steps are explained clearly to theassistants who do the job, and this guide is made with that task in mind.

SETUP
The standard specification for a 420 event inspection preparation calls for a mast/boombench/table. Dimensions should be at least 7 m in length for the mast part and 2,60m forthe boom one, with a width of at least 30 cm, 50 cm being better. Normal table heights ofaround 80‐90 cm are fine. Melamine‐coated planks are the best but in many cases we see
plain plywood which should be the absolute minimum regarding the surface quality. The
most important thing is the construction of the set: they must be rigid, leveled and securely
fixed to the ground so they won’t move. Simple taped connections should be rejected, goingfor screw joins instead. In most cases the mast table is made up of at least 2 or 3 parts so wewill have one or two joins to look after; the boom can be made of only one, but it must be
securely fixed to the mast table itself, positioned around the lower limit point (~1,160 m)
and at right angles to the reference line (see Fig.1). Proper cutouts have to be made for thespreaders, and preferably for the compass bracket and any fittings near the bottom of themast. In addition, there must be space for the mast weight scale. A separate small table canbe used, but if space (table width) permits and if you have a separate scale for the foils, youcan use the mast table itself (Fig.1). In general, avoid at all costs a setup using trestles
because a) you will need measuring tapes to do the inspection instead of template marks(which are the fastest!) and b) the spars will bend from their own weight so they will not bestraight. See ERS H.4.1 and always remember that when checking permanently bent spars,measurements are taken along the spar! That might make a slight difference in masts withexternal sail tracks where the top section is usually not in‐line with the bottom part.
Fig.1 shows the standard mast/boom table arrangement including a scale for mast weighing.
This example is made up of two parts, joined around the spreader height position. Since they
were normal tables, they were joined by using a separate wooden piece screwed on top ofthem (Fig. 1b, under the scale); in case of a disposable plywood surface, a cutout for thespreaders may be accommodated instead (Fig. 1a), about 10 ‐ 15cm long and ~10cm inside
the axis line.

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When the tables are positioned and fixed in a satisfactory way, then you can proceed to thetemplate mark preparation:a) Draw the reference line, which is the axis of mast measurement (Fig.1). It doesn’t have tobe drawn all the way up the top of the mast but only around the areas where you take ameasurement. That is near the heel, the gooseneck, the pole fitting, the spreader bracket,
the hounds and the top. Use a laser beam straight edge instead of the traditional string: it isfaster and more accurate. Use thin pencils and permanent marker pens. The thinner yourlines are, the better. Use color‐coded marks when there are a lot of then close‐by (e.g. at thehounds)b) Decide on the datum point position and draw a line perpendicular to the reference. That
will be the mark for the datum point (heel) stopper.
c) Mark the various measurement points. Near the spreader bracket you may use areference mark lower than the actual point (2,550‐2,650 m), because of the cutout. Then
you can use the reference point to check the actual spreader height. Fig. 2 shows areference point at 2,500 m. You may also use preformed templates for the shroud, trapeze,forestay and spinnaker halyard points (fig. 3), to minimize the time spent in hand drawing
marks. You will only need to find one point on the table, and then attach the template.
d) Draw a line perpendicular to the reference line at the gooseneck position (1,160m fromthe datum). Use a laser square or the 3/4/5 triangulation method to set and verify the line.
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That will become the reference axis for boom measurement. On that line, mark the 2,400 m
point for the outer limit.

Fig. 2Fig. 3e) Draw a line for the spinnaker pole on the boom table. Mark the 1,750 m length at bothends. At this point you are ready to install the blocks/angles which are needed to set themast on the table.
f) For the mast heel (datum point for most measurements), use a very strong aluminum
angle as a datum point stopper (Figs 1 & 4). Normal aluminum angles are good enough,provided they are thick enough! Recommended sizes are 50X50X2.5 or 3mm (width‐height‐thickness), 100mm long. Fig. 4 shows a special thicker angle used by the Finn class.
Whatever equipment you use, make sure it is square (vertical face is really vertical, andperpendicular to the axis of measurement (aft edge of spar), especially if you use a wooden
block. Use screws to fix the stops tightly and mark their outlines on the table with a markerpen.
g) To align the mast properly on the table, especially for checking the boom outer point, useat least two angles/blocks (luff groove stops in Fig. 1): one should be positioned about 50~60
cm above the gooseneck and the other above the spreaders (Fig. 5).
h) Fix two more aluminum angles as spinnaker pole length limits at the marks made in step(e) (Fig. 6). These stoppers may be smaller in length (~50mm).
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Fig. 6 Pole limitsi) Cover all marks with clear tape to protect them from wet masts! Mark all table joints andthe table legs the floor, so it will be obvious if anything moves during measurement time. Itis also a good idea to have a copy of the rig rules taped on the mast table for quickreference, and to write down the dimensions of each mark next to it.

APPLICATION OF THE RIG TEMPLATES
Mast, boom and pole must be clean, dry and with rigging properly fixed around the mast.
Check that no extra items are left on the mast, such as vang and jib tension blocks,
Cunningham and inhaul ropes, and that all items are normal for their purpose. Ask thesailors to reorganize trapeze wires or other rigging that are wrapped around the gooseneck
and create problems for the inspector!
a) Position the mast so the heel touches the datum point stopper; one of the two rig
inspectors must hold it in this position firmly.

b) Push the spar so the aft edge touches the luff groove stops. In this way the mast is
properly aligned with the axis of measurement.
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Page 4 of 4c) Use a square tool (one aluminum angle like the stoppers, cut perfectly square at the edges
is fine) to transfer the table marks on the mast spar, especially when the inspected items arenear the limits. Never check a mast without one! First item for inspection is the lower point
limit mark.

Position the tool at the reference line (left arrow) and then check the lower point on themast (black tape, right arrow). Remember that the limit is a maximum, so the tape cannot behigher than the reference line! Do not fix a stopper at that point; the tool shown in the
picture is movable!
d) Check the pole fitting extension (outmost point of fitting).

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Page 5 of 5e) Transfer the reference mark for the spreader bracket on the spar and then measure thespreader height with a ruler. A batten marked for minimum and maximum is also
acceptable, but a ruler is giving clear view to the sailors who will always question our tool
accuracy when their equipment is in trouble! Remember that the height is measured at thetheoretical intersection of the bottom edge of the spreader with the spar wall, extended asnecessary.

f) Next, check the forestay, shrouds, trapeze and jib & spinnaker halyards. In case of doubt,
remove the shrouds and the trapeze wires from the hounds to have a clear view of therigging points. Be careful when transferring the marks from the table, and always measurewith a tape from the datum point when you find items out of limits. Spinnaker halyard is tobe held at right angles to the spar and in case of an oversized block, always check theextension (Max. 40 mm) in front of the mast with the ruler or marked batten!

g) To check the upper point, first make sure the lower limit mark is exactly n the referenceline. If it is lower, then move the mast up until it hits the ark. One assistant must hold themast in this new position before the other checks the upper point.
420 RIG INSPECTION GUIDE

Page 6 of 6h) With the mast in the last position, attach the boom to check both the outer limit and theheight relative to the lower point. Paint or tape at the correct position the outer limit mark,and check that the boom top surface is at the same level as the lower point or higher (itshould be touching the square reference tool or pushing it over the reference line; if there isa gap, then the boom is positioned below the limit and the sailors must either a) modify thelower point –which means checking the upper point again‐ to match the boom or b) modify
the gooseneck/boom combination to get to the correct height).

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In this case, there is a gap between the boom and the reference line. However, moving thewasher (a) to the other side (b), may correct all or the biggest part of the problem. Further
modification of the pin by cutting the top ‐where it touches (a)‐ and extra washers at (b) maysolve the remaining part of the problem. Always take extra time to EXPLAIN CLEARLY to theassistants the procedure of checking the upper point and the boom top surface! This is themost common mistake they make, and it shows immediately at the next event when you getmasts “inspected” from the previous event but with the problem still there for everyone tosee!
i) Finally, just try to fit the pole within the two length limits (Fig. 6). The pole should go inside
freely! Don’t push it to go down, and never let the sailors do it! Your stops will be damaged
in the end, and the poles are still longer! Because of that, do check again the distance
between the stops from time to time to make sure it is still correct after the day’s (ab)use.
j) Mast weight is the last check: make sure there are no extras, like shroud adjusters the jib
halyard tensioning system or the vang. For centre of gravity checks, you need to remove thetrapeze adjustment systems and put the halyards in sailing position with the tails resting on
the floor. Mark the 2,400m point on the spar, balance the mast there and see on which side
it goes down! (The top should go down!) At the moment and with current equipment, mast
weight is not critical or even close to the limits so it may be excluded from the inspection
process, especially if the timetables are tight!

FINAL NOTES
Mast & boom stoppers are not to be checked here. The fully rigged boats should bepresented to the measurer after the inspection and that’s when it is to be done. A quick lookat the mainsail head and clew should give you a clear idea on the proper stopper position.
Finally, always ask the assistants to position the event limitation stickers properly (seebelow)!!!

Dimitris Dimou
Int. Measurer, Chairman of the TC&Alexander Finsterbusch
Int. Measurer
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