1. General instructions

1.1 Before Starting
Please read ALL these instructions so that you know what tasks will be completed and what tools and materials you will need.

1.2 Plans
The plans needed are:

Profile view – Fin, bulb and rudder positions
Jig Plan 1
Jig Plan 2

To download plans click HERE

1.3 Safety
Working carbon creates dust which is potentially dangerous if breathed in and irritating if in contact with the skin. Wear a mask when cutting, drilling and abrading. Do not use a domestic vacuum cleaner unless it has a fine filter fitted.

1.4 Preparation of surfaces to be bonded
All surfaces that are to be bonded or have epoxy paste added must be very thoroughly abraded with abrasive paper. Clean them thoroughly with solvent, preferably acetone, before bonding takes place. Methylated spirit or alcohol can also be used.

1.5 Bonding
Make all bonds with epoxy paste made from resin and hardener that has been thickened using some silica to prevent it from sagging or running before curing. Fillets should be made, and large gaps should be bonded, with epoxy resin/hardener thickened with silica and bulked out with microballoons to reduce the weight added. Do not use quick cure epoxy glues as these will distort the hull surface.

Tip 1 – allow fillets of epoxy paste to part cure, wet your finger with washing-up liquid and use it to smooth the surface of the paste to the required shape.

Tip 2 – after using a brush with epoxy resin it should be wiped clean and ‘washed’  in 10 cc of epoxy resin (no hardener). Leave it standing in the resin until needed next.

1.6 Method of working
Each step is described individually but you will probably find it more efficient to add the structural parts by marking out all positions first, making all holes next, abrading all surfaces to be bonded next, and bonding parts last. Work in a similar way for the fitting out process.

1.7 Measurements
Dimensions for setting out are given from various datum positions.

2. Instructions for adding foils and ballast

The following steps cover the tasks required to finish and add the fin, rudder and ballast to the hull.

2.1 Shape the fin profile
The fin moulding is supplied with flanges at the leading and trailing edges that are part of the manufacturing process. The fin has to be finished to section shape but it is best to carry out this step after the fin has been finished to the correct profile shape. This will minimise the amount of work required to finish the fin to section and will prevent the fragile trailing edge being exposed to damage.

Transfer the profile shape of the fin to the fin moulding using the leading edge as the datum line. Cut with a hacksaw or bandsaw and shape to the required profile with coarse (60 grade) abrasive paper.

2.2 Check the fin position
Place the fin in the fin box and measure the distances from the forward lower tip to the ends of the hull as shown. Adjust the shape of the profile of the head of the fin until you achieve the target figures.

2.3 Seal the fin edges
Fill the open edges of the fin at top and bottom with epoxy paste. When cured use abrasive paper to smooth upper edges and the lower end of the fin.

Take the opportunity to fill any minor blemishes in the surface of the fin at the same time.

2.4 Insert for fin bolt
Place the fin in the fin box and mark the position of the bolt hole on the top of the fin. Drill a 5 mm diameter hole down from the marked position of the fin bolt.

Drill through the fin on the line of the bolt hole to make the 10 mm diameter hole that will be used to house the stainless steel insert (INS-040) for the fin bolt. The position may vary slightly from the drawing.

Wax the fin bolt, squeeze epoxy paste into the upper holes and add the fin bolt through the stainless steel insert. After the paste has cured, remove the fin bolt and ensure it is a free fit into the insert.

2.5 Insert for ballast attachment
Drill a 3.2 mm diameter hole up from the bottom of the fin (at its thickest point). The position may vary slightly due to the presence of webs in the fin core. Allow the drill to be guided by the webs.

At this stage it is best to block the hole in the bottom of the fin with Plasticene (modelling clay) and carry out the work required to bond the ballast onto the bottom of the fin – see the instructions for the ballast.

After that step has been completed and the ballast removed from the fin, please continue with the steps described herebelow.

Drill through the fin on the line of the hole to make the 6 mm diameter hole that will be used to house the stainless steel insert (INS-030) for the ballast studding. The position may vary slightly from the drawing.

Squeeze epoxy paste into the lower holes and add the studding through the stainless steel insert leaving 20 mm projecting from the bottom of the fin. After the paste has cured, clean excess paste from the fin and ensure it is a free fit into the ballast.

2.6 Finish ballast and attach ballast to fin
Pay attention to the placement of the ballast centre of gravity with respect to the fin. The ballast is given an upward tilt of 2 to 3 degrees. Small variations from this are possible by using suitable size packing pieces between the ballast and the fin in the slot. You may want to test less or more upward tilt. If fillets and/or fairings are required between ballast and fin then you will have to specify the ballast tilt required.

The target weight of the fin, ballast and fin bolt is 2495 grams. This will give a small margin for error in the scales used by the first measurer and later event measurers.

2.7 Shape the rudder profile
The rudder moulding is supplied with flanges at the leading and trailing edges that are part of the manufacturing process. The rudder has to be finished to section shape but it is best to carry out this step after the rudder has been finished to the correct profile shape. This will minimise the amount of work required to finish the rudder to section and will prevent the fragile trailing edge being exposed to damage.

Transfer the profile shape of the rudder to the rudder moulding using the leading edge as the datum line. Cut with a hacksaw or bandsaw and shape to the required profile with coarse (60 grade) abrasive paper.

2.8 Finish fin and rudder to section
See SAILS Etc Product Information PI370a, 370lx for details

2.9 Add the rudder to the boat
Place the rudder into the trunking and adjust the top so that, in front of the stock, the gap between the top of the rudder and hull is reduced to a minimum.

Cut the rudder stock so that the top is flush with the deck.

2.10 Add the fin to the hull
Drill three 1.8 mm diameter holes through the fin where shown. Insert three M2 x 10 mm long countersunk head screws into the holes until they protrude an equal amount each side.

Make the jigs for fin alignment shown on the Jig Plan 1. Make sure that the jig shaped like a question mark (?) is shaped to allow for the taper of the fin. Make sure the size of the slot in the other jig is chosen so that the jig fits half-way up the fin. The design and method of use of the jigs compensates for any lack of accuracy or symmetry in the jigs themselves so the absolute precision in their construction is not important.

Test and adjust the verticality of the fin as follows:
• Place the fin into the fin box and check using the jig shaped like a question mark (?)
• Place the jig on the port side of the fin and note the position of the deck centreline on the upper part of the jig
• Reverse the jig and place it on the starboard side of the fin, noting the deck centreline position
• If the two marks are in the same place then the fin is symmetrical in the boat
• If they are not in the same place you should adjust the upper screw until the marks coincide

Test and adjust the fore and aft alignment of the fin as follows:
• Place the boat upside down on a flat surface with the fin vertical
• Place the jig with the central hole on the fin as shown on Jig Plan 2 
• Mark the hull, or the surface that the hull is resting on, under each plumb line
• Lift the jig off the fin, turn it upside down, and replace it on the fin
• Again mark the hull, or the surface that the hull is resting on, under each plumb line
• If the marks are in the same place then the fin is aligned with the hull
• If they are not in the same place you should adjust the two lower screws until the marks coincide
• Do this by turning the screws in opposite directions by an equal amount – this will keep the fin on the hull  centreline and retain the verticality of the fin

Now test the verticality of the fin again and adjust if necessary.

When the fin alignment is correct apply masking tape to each side of the fin in line with the hull to protect it from epoxy paste.

Remove the fin and apply release wax to the inside of the fin box. Also apply a second piece of masking tape to each side of the fin 12 mm above the first piece. Clean the fin between the tapes where epoxy paste will be bonded to it and replace the fin in the hull using the fin bolt to hold it securely. Fill the gap between the fin and hull with epoxy paste making sure it is not liquid enough to flow far into the gap. Allow to cure thoroughly.
Remove the fin bolt and break the bond between hull and fin. Clean off the excess filler, tapes and wax.

2.11 Add fillets to rudder and fin
The addition of leading edge root extensions (fillets) to the fin and rudder is described in SAILS Etc PI 370a, 370lx.

3. Some instructions for completion of the boat

3.1 Tape over foredeck tube hole
Add self adhesive tape over the lower end of the foredeck tube.

3.2 Add patches over hatches
Add the self adhesive deck patches over the openings. This is best done by applying a solution of soft soap (like the soap used in soap dispensers) in water to all the areas where the patch will be placed. Peel off the backing paper from the deck patch material and lay the patch where required. The soap solution will allow the patch to be placed accurately where it is required. Allow to dry before sailing.

3.3 Internal ballast - waterline endings
The design and target displacement is 4010 grams. This will give a small margin for error in the scales used by the first measurer and later event measurers.

When you have finished the installation of all equipment that will be on board during racing, you should weigh the boat. Weigh the three rigs and add rig corrector weights to the lighter rigs until they match the weight of the heaviest rig. Rig corrector weights, SAILS Etc item 145g, are suitable for use on 11.0 and 11.1 mm diameter masts. They weigh 10 grams each. The weight of deck patches will be 12 grams.

Calculate the required corrector weights to bring the total to 4010 grams and make it in two pieces that can be placed each side of the fin box. It is best to cover lead with tape (deck patch material is excellent) to give a better bond for the silicone sealant to the lead.

If you have the opportunity to float the boat before bonding the corrector weight in place it is worth doing. Place the corrector weight in the hull and add a rig and all other equipment required on board for racing. When the boat is on its design waterline, the water surface is level with the bottom of the transom and half-way along the bottom edge of the bumper. Allow for the height of the meniscus when judging this. Move the internal ballast backwards or forwards to correct any error.


Note: Parts of SAILSetc Document KI61 Pikanto 2008 have been used in these Instructions by permission of SAILSetc and remain copyright of SAILSetc.

Prepared by Robert Grubisa
Rijeka, November 2008

PDF file of the Instruction may be downloaded HERE