The Mast Design
The mast is fabricated in Paris and built off the Goldspar teardrop design. The rigging positions and shroud rack design are to control a rather whippy mast with a very large mainsail. Aluminum stiffeners sleeved into the mast are used to mitigate this movement. A jumper with outriggers is also used to control aft pressures at the crane affecting the upper third. Another set of shrouds may be needed at the gooseneck to prevent forward movement. This remains to be seen. Point identification stations are used like the hull for fittings. The stations are measured from the base of the mast upward.
The rig needs to be very functional for competitive sailing while at the same time travel. The latter drove the design to accomplish the former. The mast is separated for 92 and 18 inch sections. The lower will have attached the main boom and vang. The mainsail, jibsail and the mast parts will be removed for shipment and stored in the crate.
Crane and Stiffeners
The mast and other parts were powder coated in advance of construction. The head was prepared using a needle file to receive the crane. A description of the crane is in the Hardware section. The neck was designed to snuggly slide inside the mast to prevent any rocking.
Sometimes there is luck. By cutting off the sail track of a Goldspar mast used on the EC12, the remaining shortened tear drop is a perfect fit inside the Paris mast. It is so perfect that a powder coated one will not fit. The Goldspar is only 72 inches so another piece was used to reach from below the crane neck to a point 87 inches below the top of the mast. This is station 23 (measured from the base) and where the lower/lower shroud tangs will be located. No glue is used as mast fitting screws will hold it in place. However, it does not move on its own.
The Mast Splice
The 18 inch lower section of the mast was sleeved also but to reach from the base and to meet the upper mast sleeve at station 23. Hence, this lower section will become 23" long. This splice does not allow any twisting as you can see when the two mast sections come together.
However, trouble on the race course. A 116" rig design with about 4000 square inches of sail was running with a stiff breeze when the mast sheared off at the splice. Without getting into the details of the analysis, the Goldspar insert was determined not have enough wall thickness to handle great forces. The following was designed to add strength to the splice.
The base below was installed in the Goldspar insert. A piece of .3125" (5/16") aluminum tubing with a .035" wall was cut and inserted into the Goldspar insert from the base installed to just below station 23. A piece of .064" sheet aluminum was prepared to the same width of the insert and pushed in the full length within the gap of the tubing and the insert. There is no movement of any piece. This strengthens the wall at the splice while still using the Goldspar mast insert to prevent twisting...it looks good in the shop!
A piece of hardwood was fashioned to fit inside the sleeve at the base for the mast step mounting pin. The sleeve and the mount are recessed slightly to allow sealing with resin to protect the wood.
The full 110 inches of mast is assembled and secured for marking of the stations for the fittings. Blue tape was used to mark the drilling locations and include the number size drill to be used. All holes were to be drilled in one session while the mast could be flat on the press table. This marking is only on the upper section as the lower 18 inches will be done later as its own piece. The drills used here will be noted below with each fitting. The positions are also specific to the part used. Overview notes of the below are needed to complete this marking if this design is used. The positions are on the graphic at the head of the page, however, work out the variations your need.
Note: All drilling is done with the sleeves inserted and in their correct position. The blue tape is used to prevent drills from walking on the outside. Walking inside the mast is a caution for the spreader drilling and noted below.
Leading Edge Tangs
The forestay and the lower jumper wire mount tangs are installed first. This will lock the sleeve during further drilling. These are Pekabe fittings and have been drilled for #2 sheet metal screws (#42 bit). Alignment is secured and the holes punched for a #50 bit for the threading. Don't go hard on your self, they are very hard to get straight.
This is something that you do want to get straight and perpendicular to the mast. It is hard due to a tendency of the drill bit walking inside the mast. The best solution here with the equipment at hand is to shorten the drill bit in the chuck to no more than is needed to punch through the other side. Likewise drill very slowly. If it takes five-minutes to complete you will probably have it right. The hole is drilled slight forward of center on the side of the mast. This is the thickest portion of the mask and presents less properties for walking. A #42 bit was used so as to receive the #/32" core wire.
Four pair of these will be installed at this time. The tangs are drilled for #2 screws like above. There are two different sets, a pair each for the upper and a the lower/lower. They are aligned, punched and the mast drilled. These are mounted with two screws each.
The second set are those at the two spreaders. The core wire will pass through the top hole of the tang and a screw for the other hole. A piece of core wire was cut to assist in alignment for the one punch. The mast was drilled and the screw and tang installed with the core wire in place. You guessed it! Pliers were needed to remove the core wire and was expected. With both tangs in place, the tangs and the spreader hole was re-drilled with a #40 bit for a snug but easier fit of the spreader to the mast.
A single tang is attached to the leading edge of the mast centered across from the gooseneck. The shrouds for these will be attached to the inside of the shroud racks. They will not allow the mast to bend forward under pressure.
The spreaders are 1/8" brass tubing over a 3/32" core wire. This wire is cut to match the full length of the spreader when full assembled. The shroud wire holes are .055 and should hold a pair on wires on the lower spreader. One end of the core wire is glued into a tube.
The jumper spreader is 6" across and fashioned of .064 aluminum sheet. Lightening holes were not cut as it was thought they would create more drag than the solid surface. The spreader will be removed during storage. 60 pound wire and an slide adjusting sleeve was used over the wires. The unit as shown will be powder coated.