WO1979001077A1

WO1979001077A1 - Sail craft

Info

Publication number: WO1979001077A1
Application number: PCT/DK1979/000014
Authority: WO
Inventors: K Gram
Original assignee: K Gram
Priority date: 1978-05-16
Filing date: 1979-05-14
Publication date: 1979-12-13
Also published as: GB2036656B; SE8000124L; EP0016770A1; DK213478A; US4344377A; GB2036656A

Abstract

Means lor improving the yield or a sail of a sail craft and at the same time to secure the craft against having the bottom turned up after a capsizing. According to the invention a certain amount of buoyancy material (8), which is flexible, is fastened to the uppermost portion of the sail, see fig. 1 and 2, the buoyancy material (8) being shaped such as to form together with the mast (1) and the sail (3) an acceptable airfoil profile, see fig. 2. The buoyancy material (8) has at the same time a volume, which is large enough to keep the sail (3) and the mast (1) floating at the water surface after a capsizing of the craft. In order to make the folding of the sail (3) easier prior to putting it into a sail bag, the buoyancy foam may be split up into a plurality of buoyancy zones (4 and 5) separated by folding zones (6), see fig. 1.

Description

Sail craft Technical field

The invention relates to a sail craft, and in particular, but not exclusively, to hobby boats such as sailing ding¬ hies, multihull boats and keel boats.

Background of the invention

The sail crafts now in use are extremely difficult or even impossible to upright after a capsizing, if the mast has occupied a position vertically downward into the water, as this constitutes a natural position of equilibrium. It is difficult or even impossible for the crew to hold on to th upturned slippery bottom of the craft.

Large efforts have therefore been made to design sail crafts in such a way that the angle of heel cannot exceed 90-100 corresponding to a position, in which the top of mast is situated a small distance below the water surface.

The most simple method consists in putting buoyancy materi al, for instance plastic foam, into the uppermost portion of a hollow mast. However, due to the small volume of the mast, this is in most cases quite insufficient to prevent 180 capsizing of the craft, and this method can therefore result only in a slower 180° capsizing than would otherwis be the case.

An efficient and safe prevention of the 180 capsizing can however, be obtained by placing a buoyancy body, e.g.^' of plastic foam, at the top of the mast. This is known for in stance from the specification to US patent No. 3 865 061 and from German published patent specification No. 2 163 329. As this buoyancy body, which is usually shaped as a solid of revolution, should have a comparatively large vo- lume in order to secure the desired effect, for instance 10-15 litres for a sailing dinghy having 10 m of sails , the body will during sailing with the wind before the beg- produce a large air resistance which will considerably de¬ crease the net motive force acting on the craft. Further¬ more, this buoyancy body is permanently exposed to the in¬ fluence of the weather and is also exposed to the risk of mechanical damages.

From the desription to Danish patent application No. 5435/75 is finally known an air bag intended to be placed in the interior of a double layer wing sail. However, such an air bag will become aerodynamically detrimental if used ^■ in connection with a single layer sail, and is further ex¬ posed to punctures, which will normally not show up until the air bag gets into the water after a capsizing, thereby being exposed to external pressure.

Explanation of the invention The object of the invention is the provision of means for preventing the said 180 capsizings, which means are not permanently exposed to the influences of weather, cannot be punctured, and will not decrease, but on the contrary ap¬ preciably increase the motive force acting on the craft, so that the means can also be used for keel boats or other sail crafts which will normally not be exposed to 180 cap¬ sizings.

This is according to the ^'invention obtained by the fact that a certain amount of buoyancy material made up of flex- ible foam material is fastened to at least the upper por¬ tion of at least one of the sails of the craft, the foam material being shaped such as to form together with the sail and the mast an airfoil profile being as efficient as possible, and having - if ever possible - a volume which is large enough to keep the sail and the mast afloat at the water surface after a capsizing.

By fastening the buoyancy material in this way to the sail instead of to the mast, as was done before, a number of technical advantages are obtained completely "free of ch^£- ge". In the first place the buoyancy material is protected from the permanent influences of the weather, as it is ta¬ ken off together with the sail, possibly is dried, and the¬ reafter is kept in dry condition in a sail bag. In the se- cond place the buoyancy material is protected from mechani¬ cal stresses, as it will be handled in practise with as much care as the sail itself. In the third place, the buoy¬ ancy material will give rise to a somewhat increased stiff¬ ness of the uppermost portion of the sail, which will give rise to a decrease of the angle of twist of this portion of the sail.

However, the greatest advantage consists in the fact that the buoyancy material can be spread over such large area of the sail that its volume, despite of the comparatively small thickness, can be made abundantly large to safeguard against 180 capsizings without increasing in any way the wind resistance of the sail, the socalled "drag". On the con¬ trary, the wind resistance of the corresponding portion of the sail is decreased, because the horisontal sections of the sail will get smooth outline curves without any of the otherwise unavoidable jumps and elbows which are present in a horisontal section through a mast being connected to a single layer sail.

Thus, the invention can also be applied in keel boats, which will obtain thereby an appreciably greater motive force per square meter of sail area. However, in this case the invention does not at the same time solve a safety prob¬ lem, as is the case for unsinkable sailing dinghies, cata¬ marans and the like.

if the sail craft has at least one single layer sail, the buoyancy material may according to the invention be shaped such as to fill up the two outwardly open spaces between the mast and the two sides of the sail and to stretch it¬ self preferably right from the mast to^' the aft edge of the sail. In this way, a horisontal section through the sail may be shaped as a comparatively efficient symmetrical foil profile, whereby both a decrease of the wind resist ce and an increase of the "lift" of the corresponding po tion of the sail is obtained, so that an appreciable in crease of the motive force acting on the craft is achie ed. Furthermore, the downturned surfaces of the buoyancy material will act as a marginal plate which will decreas the flow of air from the pressure side to the suction si of the sail, so that the efficiency of the main portion the sail under the buoyancy material will be improved co siderably.

It is important that the sail and the buoyancy material be arched to a suitable degree under wind pressure durin sailing. This flexibility may according to the inventio be obtained by the fact that the foam material is made u of a number of thin, flexible, plastic foam sheets being laid flat on top of each other, as a unit of such thin sheets has a greater flexibility than a solid.piece of f material.

The buoyancy material may be sewed and/or glued on to t sail.

Due to the foam material, problems by the folding up of sail prior to putting it into a sailbag, may arise. Ther fore, the buoyancy material may according to the inventi be split up into horisontal sections preferably extendin right from the mast to the aft edge of the sail and bein separated from each other by folding zones. By the foldi up of the sail these sections will be positioned on top each other and will thereby form a kind of parcel, which may form the basis for the continued folding up or rolli up of the sail. As the folding zones are extending in a risontal direction, i.e. in the direction of the air flo the "corrugation" of the uppermost portion of the sail t produced will have no detrimental aerodynamic influence.

Short description of the drawings The invention will be described further in the following with reference to the drawings which show two examples of the application of the invention, and in which fig. 1 is a side view of a conventional Bermuda- sail, the uppermost portion of which is provided with buoyancy material accord¬ ing to the invention, fig. 2 on a much larger scale is a section a- long the line II-II in fig. 1, fig. 3 is a side view of a wing sail, the upper¬ most portion of which is provided with buoyancy material according to the inven¬ tion, and fig. 4 on a larger scale is a section along the line IV-IV in fig. 3.

The preferred embodiment of the -invention The sail 3 shown in fig. 1 consists of a single layer and is in a conventional manner along the forward edge and lo¬ wer edge provided with a rope which can be inserted into grooves in a mast 1 and a boom 2, respectively. The upper¬ most portion of the ^'sail is split up into two buoyancy zo¬ nes 4 and 5 being separated by a narrow folding zone 6.

As shown in fig. 2, the foreleech 7 of the sail is receiv¬ ed in a groove along the aft edge of the mast 1 which con- sists of a profile obtainable on the market. At both sides of the sail is fastened buoyancy material 8 consisting of for example flexible foam plastic which may be foamed up in a mould so that it shall not subsequently be cut to shape. A piece of sail cloth 9 is laid tightly around the foreleech 7, the two layers of the cloth being sewed to¬ gether closely aft of the foreleech 7. To the rear of the seam the two layers of the sail cloth 9 extend along the outer surfaces of the buoyancy material 8 at both sides of the sail 3, and the two free edges of the sail cloth 9 are sewed on to the sail.3 by a seam 10 along the aft edge of the sail. However, the sail cloth 9 may be dispensed with, if the "skin side" of the buoyancy material 8 is faced outwardly and is in^' itself satisfactorily smooth and eve

It will be seen that the buoyancy material 8 is shaped s as to form together with the mast 1 and the sail 3 an ae dynamically acceptable profile having a much better lif drag ratio than the profile formed by the mast 1 and the sail 3 in combination. The thickness ratio of the profil of section II-II is about o,25, but further downward the thickness ratio will be appreciably smaller. Furthermore the buoyancy material 8 has a volumen which is large eno to be able to keep the sail 3 and the mast 1 afloat in t water surface after a capsizing of the sail craft on whi the mast 1 and the sail 3 is mounted.

Industrial use In manufacture, the sail cloth 9 is first sewed on to th sail around the foreleech 7, whereafter the two layers o buoyancy material 8 are attached to the sail 3, e.g. by gluing. Finally, the sail cloth 9 is laid on the outer des of the buoyancy material 8 and is sewed to the sail the seam 10 at the aft edge of the sail. The sail cloth may be glued or sewed on to the buoyancy material 8 long horisontal lines spaced equal distances apart.

Instead of foaming the buoyancy material 8 up in a mould shown in fig. 2, it is possible to use a plurality of t layers of material being laid flat on top of each other cut to shape to produce the shape shown in fig. 2.

It is further possible to attach additional buoyancy mat rial along the whole length of the foreleech of the sai 3, stretching for example from the mast 1 to the chain-d ted line 11 in fig. 1. In this way is obtained an apprec able decrease of the drag of the sail and a small increa of the lift. Taken in combination this gives rise to a c siderably larger motive force acting on the sail craft.H

O ever, for reasons of safety there is no need for this buoy¬ ancy material, as the buoyancy zones 4 and 5 are sufficient. The thickness of the buoyancy material at the mast totals 6 cm for the sail shown in fig. 1, this sail having an area of approximately 7 m . The volume of the material will thus be about 15 litres, which is abundant to keep the mast and sail floating at the water surface after a capsizing.

If buoyancy material is placed along the .whole length of the foreleech, .the mast profile should be adapted hereto. The profile may for instance consist of the front portion of a NACA 0012 bounded at the rear by a plane surface at right angles to the axis of symmetri of the profile. Hereby an appreciably larger motive force of the sail can be ob¬ tained than in the case of the profile shown in fig. 2.

The invention may also be applied in connection with the the wing sail shown in fig. 3, which is folded around the front edge of a round mast 12, its lower edge and upper ed¬ ge being drawn all the way round along NACA 0012 shaped sail rails attached to the top side of a boom 13 and the under side of a frame 14. The sai-1 has a concave aft edge 15. The described unit can as a whole be rotated about the axis of a vertical tube 17 which by means of a cranked por¬ tion is displaced somewhat aft of the mast 12, so that the sail can be- turned away from the direction of the wind by a horisontal pull of not more than 2 kilograms exerted on the boom.

Vertical tension of the sail is obtained by means of a kicking strap 18 and a clamping ring 19 which can be slit along the mast and clamped thereto in any position. Hori- sontal tension of the sail is obtained by means of a line 20 received in a running in each of the two layers of the sail at the aft edge 15 of this. Each line 20 is fastened to the frame 14 and is below led through a hole in the boom 13. • Six pockets 21, each containing buoyancy material 22 in form of for instance flexible plastic foam, are sewed on the inner side of each layer of the sail. Between the poc ets 21 are horisontal and vertical foldings zones 23 whic make it possible to fold the sail to a size correspondin to the size of one of the pockets 21. It is clearly seen fig. 4 that the buoyancy material should have large flexi lity, as it during the putting on of the sail has to pass the relatively sharp curving of the front end of the 001 profile. In order to obtain this flexibility, a number of foam sheets put together may be received in each pocket i stead of one single plate in each pocket, for instance fo sheets of 2,5 mm thickness each, instead of one single plate of 10 mm thickness.

If the area of the buoyancy zones of this sail is increas to for instance double as much as shown, it will be possi to shape the buoyancy material-as an integral "carpet" of flexible foam plastic, which is sewed onto the inner side the sail along the full width of this, i.e. all the way _> round along the inner side of the sail profile shown in f 4, whereby the manufacture is simplified. Such a sail may possibly be rolled together like a carpet prior to puttin it into the sail bag.

he, sail shown in fig. 1 and 2 can be used for any sail craft, i.e. also for keel boats, whereby the motive force per square meter" of sail area will be increased by up to 100 % mainly due to the reduction of the flow of air fro the pressure side to the suction side of the sail main po tion situated below the thickened buoyancy zones 4 and 5.

The sail shown in fig. 3 and 4 can be used on sail craft any kind and will result in a still larger motive power p square meter of the sail area.

OM LIST OF ITEMS mast boom sail buoyancy zone buoyancy zone folding zone foreleech buoyancy material sail cloth seam chain-dotted line mast boom frame aft edge cranked portion vertical tube kicking strap clamping ring line pocket buoyancy material folding :zones

OMPI

Claims

Claims 1. Sail craft, characterized in that a certain amount o buoyancy material (8) made up of flexible foam material fastened to at least the upper portion of at least one its sails (3) , the foam material being shaped such as t form together with the sail (3) and the mast (1) an air profile being as efficient as possible, and having - if ever possible - a volume which .is large enough to keep sail (3) and the mast (1) afloat at the water surface a ter a capsizing.

2. Sail craft as claimed in claim 1 having at least one single layer sail, characterized in that the buoyancy m rial (8) is shaped such as to fill up the two^•outwardly pen spaces between the mast (1) and the two sides of t sail (3) and to stretch itself preferably right from mast (1) to the aft edge of the sail (3) .

3. Sail craft as claimed in claim 1, characterized in t the foam material is made up of a number of thin, flexi plastic foam sheets being laid flat on top of each othe

4. Sail. craft as claimed^' in claim 1, characterized in t the buoyancy material is split up into horisontal secti (4 and 5) preferably extending right from the mast (1) the aft edge of the sail (3) and being separated from e other by folding zones (6).

000