THREE SECRETS OF THE MAST

THREE SECRETS OF A MASTThe mast — Foundation of rig of the vessel, its main node. The role mast multi-function, from its devices and locations on the vessel dependent area, the configuration and aerodynamics of the sails, the ability to control their thrust, the location of the centerboard and much more. So the choice of the type and design of the mast determines the construction features of the vessel, and the level of effectiveness of its sails.

This choice is complicated when you create a small portable vessel, when it is necessary to “reconcile” the contradictory requirements such as durability and reliability of parts with their minimal weight and compactness of packaging of the dismantled vessel. Especially in the design of the mast. The main tasks that decide the following: select the type of masts and materials for its production, the choice of variant structural embodiment (including the method of attachment of the grotto) and finally, selection of design steps.
 
SECRET ONE: CHOOSING THE TYPE OF MAST
 
Less than the “whole” of the vessel strength of hull of small sailing ship makes to increase the strength of the mast. A task to reduce its weight to a minimum reduces the range of suitable materials. So, a wooden mast is too heavy, warp or rot from moisture, difficult to manufacture, and the quality of the wood for them is not easy to get. The same, except for the “rabies”, can be said about a homemade fiberglass masts. Therefore, the most suitable material of steel thin-walled dural tube. Especially after the development of lovers small sails two operations: Assembly of SMD likasa and turning the mast to the farm. The latter significantly improves the ratio of ” strength/weight “.
 
On the ship the mast or put a side and front extensions — guys and the forestay (Fig. 1A) or lateral braces (Fig. 16), either freely (Fig.1B) and is attached at two points. The location of the lower point (steps) do not depend on the type of mast, top — depends: for free is partners — hole in the cross beam; for raskreplennye — mounting point of the braces, or guys with a forestay that is higher partners. Guys significantly reduce the load on the mast and the hull (but complicating design). The angle between each guy and the vertical shall be not less than 11°.
Transform the ordinary masts of the truss (Fig.2) you can use three extensions of a steel cable with a diameter of 2-3 mm ambulant and transverse struts — crespin. (The stiffness of the farm will increase if you install two rows of Krasic.) The angle between ambulante and mast shall be not less than 8°.
 
Removename you can adjust the bending of the mast, thus changing the profile of the grotto and, as a consequence, it is appetite. Do it with a spiral lanyard. Turning the body of the lanyard, it will shorten or lengthen, and attached to it ambulanta simultaneously changing the pressure on the gaff rig and thereby the bending of the mast.
 
Invoice likes collected from thin-walled U-shaped aluminium profile used in construction for fastening glass panes. It is given the desired shape with a hammer and mandrel (Fig.4) any way of drawing between two rollers with grooves of corresponding shape. Ready segments the processed profile is attached to the mast with screws or self-tapping screws with a diameter of 3-4 mm. the holes for the screws are drilled before the beginning of the deformation profile.
 
Fig.1. The types of masts
 
Fig.1. Types of masts:
 
a— raskreplennye stretch marks, b— raskreplennye struts, in— free; 1 — steps, 2— guy 3— forestay, 4— lateral bracing, 5— partners.
 
Fig.2. The mast truss

 
Fig.2. Mast truss:
 
a — General view, b — variant of the node crespin; 1 — mast, 2 — ambulante rear, 3 — krasici (D16T, pipe 12×1), 4— likes, 5— ambulanta front, 6— forestay, 7— lanyard screw, 8—, 9— slot ambulante, 10— deadlifts (D16T pipe, 12×1), 1 T— clamp (band 18CR10NITI s of 1.5—2).
 
Fig.Z. The nature of the flow of the grotto by a stream of air, depending on the method of fastening it to the mast:

 
Fig.Z. The nature of the flow of the grotto by a stream of air, depending on the method of fastening it to the mast:
 
a— rings (segar themselves), b — likasa, in a pocket on the luff of the sail.
 
Fig.4. The stages of likasa through bars
 
Fig.4. The stages of likasa using bars:
 
a — the formation of the cylindrical bottom of the profile, b — tucking shelves profile: 1 — hammer, 2 — profile likasa, 3 — bar flat (wood or Board), 4 — mandrel of a cylindrical (metal), 5 — bar figure (half the window hinges).
 
Fig.5. The nature of the flow of the grotto by a stream of air, depending on the type of mast and attachment of the guys

 
Fig.5. The nature of the flow of the grotto by a stream of air, depending on the type of mast and attachment of the vant:
 
a — fixed mast, b — mast swivel; 1,2 — attachment points of vant, 3 — likas.
 
Fig.6. Ways of connection of knees of a mast

 
Fig.6. Ways of connection of knees of the mast:
 
a — telescopic (D / D=0,2…0,5), b — on the outer sleeve (D—d=0,15…0,2), — on the inner sleeve likasa (D / D=0,2…0,3); 1 — knee lower, 2 — bearing removable pin (rivet), 3 — knee top, 4 — outer bushing, 5 — Bush internal 6 — pin (screw or rivet), 7 — links likasa.
 
Fig. 7. The attachment point of the boom

 
Fig. 7. The attachment point of the boom:
 
1 — the heel of the boom, 2— eyes, 3 — fastening screws 4 — “spider” joint 5 clamp the mast.
 
Fig.8. Types of Stasov

 
Fig.8. Types of stepsof:
 
and — wood and metal (tubular shaped) — for wooden rowing boats and spanovich, b— flat-metal — for installation on the keel of the kayak, in — complex— for installation on the beam of the vessel megacorps-Nika; 1 — spurs masts, 2 — steps-clamps, 3— pin swivel 4 — swivel clamp, 5 — screws-limiters.

 
The thrust of the grotto depends on the method of its connection with the mast. As a small craft sail area is small, but the drag of the hull and the crew is relatively large, it is disadvantageous ratio (compared to a big yacht) impairs the ability of small craft to move against the wind. Therefore, it is important to follow two “not”.
 
First, to prevent gaps between the mast and the mainsail, because cutting them in on the windward side of the sail the air significantly reduces cravings, especially on sharp courses. This happens when the mainsail is attached on the rings (Fig.3A), the hinge-search, lace-up or sliding blocks sliding on attached to the mast rail. “Holes” will not be if the grotto to strengthen lipase — longitudinal slot on the rear side of the mast (Fig.3b).
Secondly, not to create a ledge between the mast and the mainsail, because the violation of the smoothness of the profile of the sail, especially at the beginning, also reduces cravings. This problem is solved in stages. To improve the smoothness of the profile helps the mast teardrop-shaped cross-section, which is to get or make difficult. But you can make the mast from turning, then step between her and the grotto will be lower. And if you use pocket, the profile of the sail will be quite smooth (Fig.3b).
 
Of course, the easiest way to get to turn loose the mast. And what raskreplennye? At first glance, is preventing the forestay and shrouds. But if the mount vant to move to a single point (Fig.5B), the mast will be able to turn to the left to the right by 15-20°, which is enough.
 
With pocket mount the grotto is also not simple, for it raises a whole bunch of problems. It is known that mast are better able to resist loads, including the headsail, if it is the shrouds and forestay attach not to the top, and below it at a distance of 0.12—0.25 length of the mast. The forestay should be below guys, or at least on the same level.
 
So, the pocket on the mainsail forces to attach the shrouds and forestay to the top only and apply only the top staysail, which is the maximum load the mast. The same pocket does not allow you to equip the mast and ambulante, so you have to significantly increase its strength and rigidity, and thus, and weight.
 
SECRET TWO: DESIGN OF THE MAST
 
The articulation of the knee of the mast (Fig.6) depends on the method of attachment to her grotto. Option “a” — universal; “b” is used generally for spare masts; option “b” for raskreplennye with liposom. Links likasa should properly be joined, so the neighboring tribe in the Assembly to be secured in a specific position. The simplest option— using the screw head or rivet, a member of the slot at the lower end of the upper knee (Fig.6, POS.6).
 
The strength of the mast affects the method of fastening it to the boom. In particular, thin-walled mast “does not like” to be full of holes. This is considered in the illustrated embodiment (Fig.7). The boom attaches to the mast covering the yoke, which is easy to fix at the desired height.
 
Fastened to the boom lower part of the grotto you can either liposom or pocket (the latter is easier — it does not create any difficulty). In the pocket, make the cutout for the passage of a delay geek needed for Bermuda, GA-Velen (including Guara), shprintovoe and sometimes raked (if the bottom part is attached to the hull and not on the rail) grottoes.
 
To tension the forestay, the shrouds and the boom sling is best with a soft lanyard — nylon end diameter 3.5—5 mm, several times missed between the two rings; with an area of over 10 m2 of sail can be used spiral lanyards.
 
SECRET THREE: DESIGN STEPS
 
If the mast should not rotate as raked and Latin caves, holes in stash make rectangular or square (Fig.8A). The spurs in these holes can be either tightly or with a gap of 3-5 mm on a side.
 
Steps mounted on transverse or longitudinal beams inflatable boats and rafts, catamarans and trimarans, allow, if necessary put the mast horizontally in any direction (Fig.8b).
 
Briefly about the application of the considered structures.
 
For masts typically use tubes of alloys D16 or D16T with a diameter of 35-70 mm and a wall thickness of 1.5—2 mm, rarely 2.5 mm.
 
When the area of the grotto of less than 4.5 m2 ambulanti disadvantage: some weight savings does not justify the cost of labor, materials and, most importantly, time for their Assembly and disassembly.
G mouth fastened pocket especially in the arms of the CAT (mast plus grotto) with a free match, especially when you sail up to 4 m2. This solution gives the maximum effect: the advantages of the design work, and cons to show nowhere — no headsail and guys.
 
In addition, the pocket caves it makes sense to apply the types of weapons with a short mast: havelina, sprintcom, Latin and raked. The advantages of this solution significantly outweigh the cons: masthead staysail, although it has the largest possible area, not too load case. The mast with the often free, because the difference in weight with raskreplennye relatively small. It is easy to remove and to put, to put her in the grotto.
 
Free mast often used in the intermediate variant, when the main sail — arms of CAT complement in light winds a light staysail (that is, converted into rigged SLOOP). The staysail of heavy loads does not create, and the mast is relatively easy.
 
A FEW WORDS ABOUT THE GEAR
 
Standing rigging (shrouds and forestay, ambulante) use steel — it is not extended, thin enough, and therefore has a low parasitic windage. This is usually the cables of galvanized or stainless steel with a diameter of 2-3 mm. At worst — just a wire with a diameter of 2-2,5 mm. It is stronger, but can suddenly break down (usually near the fire point on the end of the rope).
 
The cord is about destruction, “warns”: first break individual wires.
 
Running rigging — halyards (tackle for raising sails), sheets (to control the sails), tacks and quickdraws are made of vegetable or synthetic (often nylon) ropes. The latter is preferable, they are more durable and are moisture resistant. Files do of the braided rope type cord, as twisted wire (usually of three strands) stretches under load and sail “SAG”. Allowed the cable to the core bundle of filaments in a thick and durable braid, such that when the tension of the halyard under load and subsequent compression with no load filament core through the braid. Diameter files— 6-10 mm (with an area of over 7 m2 mainsail halyard sometimes made of steel cable). The sheets have a diameter of 8-12 mm. to Make them, especially with a small square sail, and of finely twisted rope, the hood here is not as important as to hold the. Good jib sheets out of polypropylene rope, it is noticeably easier than others, which improves the management of a staysail in light winds.
 
Sail area single hull vessel can be roughly determined by the formula:
 
 
Smax=kLB,
 
where Smax — the maximum area of a sail; K — coefficient of stability (depending on the design of the vessel: kayak K=0,6…0,7, for inflatable boats K=0,7…1, rowing for K= 1… 1,2); and L is the length and width of the vessel at the waterline.
 
Depending on the characteristics of the vessel the result can be adjusted. But “inflate” the sail is unsafe. Better, dividing it into main and additional, to expand sailing “closet”, using the main sail in high wind, additional— in a weak, storm— fresh weather (primarily the grotto, which area needs to be 2-3 times less than the main).
 
Sometimes, instead of a storm jib mainsail used when its area and sufficient strength. As additional sails are used primarily stakely larger and lighter (than the core) of the fabric. When the area of the main sail up to 6 m2 can increase the “closet” without the tangible financial costs and the relatively small cost of labor — at the expense of Taxila of ordinary polyethylene film.
 
Yu KUZHEL

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