The use of marker floats as swimming aids

 

Background

Within the club, the idea of using floats as swimming aids was never seriously discussed until recently. For some years, one club member has used a Sporasub float designed specially for this purpose.  The design consists of a plastic board, which straps on top of two standard inflatable floats to form a catamaran.

 

I did once attempt swimming on top of my double inflatable floats in the same way, but with my 14 stone, the floats were unstable and sat so low in the water that I gained little speed advantage. For myself and others in the club, the purpose of using a double float was to keep spare guns up out of the water, eliminating drag and preventing tangling in weed. In order for me to get on top of the floats any guns and equipment had to be removed.

 

The first time I realized that there could be more to the idea was while reading a French spearfishing magazine. Articles covering all forms of spearfishing, including international competitions, showed virtually all divers at all dives using a type of rigid board to carry all their equipment on and to double up as a swimming aid.

I was surprised that I had seen none used locally, as the French, Italians and other Europeans carry them all around Europe and farther afield to competitions.

 

At the time, lightweight divers had a huge advantage in local club competitions as some, weighing half that of the heaviest competitor could even swim on top of a single float. With the hope of evening things out, heavier members began investigating different float designs to carry their weight. At this point it became apparent that the issue needed addressing at club level as our club rules did not state any maximum size for marker floats or set any limitations on their design shape or use. It was unanimously agreed at the 2002 season AGM that specially designed floats or boards could be used as swimming aids. The dive committee was then tasked with researching the subject and setting appropriate rules to cover their design and use.

 

Research

The main aim of the research was to establish a size limit which ruled out the use of craft, such as surf canoes and kayaks, without disadvantaging the heavier competitors. It first became obvious that there were problems with imposing any restrictions based entirely on volume. A standard spearfishing float 20cm diameter and 80cm long has an internal trapped volume of 25 litres so does a cut down windsurfer 5cm thick 50cm wide and 1.2m long.

 

Matters become really complicated when you cut gun slots and open storage compartments into a solid foam float. These are open spaces and therefore can no longer be included as part of any volume calculation. The most basic scientific method used to measure the volume of a complex shape is to totally submerge it in water and measure the displaced water volume. We could not envisage setting up a volume testing tank at every comp.

 

The maximum float size permitted in the European competitions is 1.2m long x 0.7m wide (4ft x 2.3ft) with an apparent thickness restriction of 30cm. It was clear, that we needed to consider these size restrictions, especially if members were to enter European competitions where all divers will be using such boards. Club members had differing opinions on the potential advantages to be gained by using boards and there did not seem to be any available information on the subject. It was agreed that the only way of reaching a reliable conclusion was to test various boards in the water.

 

The initial stability and speed tests were carried out in a swimming pool. Sea tests later compared the performance in much rougher conditions. The following comments are based on the findings:

 

Results of speed tests in pool

       Item tested                                                                      sizes                             speed
1. 6ft x 14 stone diver in water without board-              big gut                          2.4 mph
2. Flat kneeboard with upturned nose-                          50 x 130 x 10cm          2.9 mph
3. Flat polystyrene bodysurfing board-                          45 x 120 x 10cm          3.4 mph
4. Two standard foam boogie-boards strapped together-          50 x 100 x 10cm          3.4 mph
5. Polystyrene with pointed nose rounded bottom & keel-         60 x 110 x 15cm          3.7 mph

6. Maximum size flat polystyrene with rounded nose      70 x 120 x 15cm          3.5 mph

Stability and performance

The following comparisons are between the two boards at opposite ends of the design extreme. At one end is the maximum size flat board with a rounded nose; at the other end is the pointed nosed board with a curved underside & keel.

·    In calm conditions the pointed board had only a minimal advantage but it performed better in rough sea conditions.

·    The rounded board could easily be laid on while resting without requiring any effort to keep it upright. The pointed board required constant effort while at rest to keep it from rolling and capsizing.

·    The rounded board did not roll side to side so much while finning. Enlarging the keel on the pointed board reduced some of the rolling.

·    The keel on the pointed board caused it to pull to one side while towing unless it was perfectly balanced each side with guns and equipment. The rounded board was much less sensitive to uneven weight distribution.

·    The rounded board slaps against waves more while being towed and becomes more of a burden in rough conditions.

 

Other findings

·      A board of maximum European size and around 15cm (6 inches) thickness is sufficient to carry a heavy diver.

·   An over-buoyant board raises the body too far out of the water, decreasing the stability and making finning awkward.

·    A hollowed out recess in the top of the board stops the body from sliding off sideways and a deeper hollow is more comfortable for those with a big gut.

·    If the body is positioned too far forward on the board, the nose digs in, too far back and the board tilts backward while swimming, causing drag.

·    A firm position to grip the board at the sides or front is vital for stability while swimming hard and for mounting the board.

·    A large board is most easily carried vertically with a wide rucksack type harness. Some thicker boards will be easier to carry long distances with the guns carried separately.

·    The pointed board is much more difficult to attach guns and equipment to.

·    Guns can be securely carried in slots cut into the top of the board with straps or ties over the top.

·    Rubber tubes slid over the ends of the spears will reduce the chance of injury in rough conditions.

·    In sea conditions much over a force three, more progress is made by a diver in the water towing a normal float, than one using either board.

·    The ideal point for fixing the line for towing is near water level. Too high and the nose will be pulled down while diving in the tide or swimming along the bottom, causing drag.

·    Special care must be taken when attaching any line or strap to a foam or polystyrene board as poor fixings can easily rip out.

 

Final conclusion

In an all-out rough water race, a board constructed similar to the pointed board would be the best choice but for a normal spearfishing competition, the much greater stability & carrying capacity offered by the flatter, rounded board makes this the better choice. The type of boards designs seen used in the European competitions supports this conclusion.

 

A word of caution

A diver should not rely on his board to negotiate strong currents on his return to shore. Many unforeseen events such as deteriorating sea conditions, a broken fin strap, or lost board can lead to a serious safety situation.

 

Boards available commercially

 

Several commercially available boards are seen regularly in European competitions. The most popular one seems to be the Sub’Ideal. The board is made from heavy-duty plastic and is very robust. The drawback is a weight of approx. 7.5 kg (16lb). Add guns and equipment and you have the weight of another weightbelt. Not recommended when a long walk to the water is involved. The board is not very deep and has little buoyancy at the rear. I would not consider it buoyant enough to suit a heavy diver. The board comes with gun slots, storage compartments, a reel and handles. It is for sale on the French internet site www.sub-marine.com at around £130.00.

For slightly less, the same company sells a fully inflatable board called a Sevlyor Dive Hunter which look like a miniature inflatable dinghy with no back. It has many separate air chambers covered by a tough outer skin. In tests the board performed well, being the most buoyant, stable and comfortable of all the designs and fast in calm conditions. The most significant advantage is in transportation.  It weighs little compared to the other manufactured boards and is easy to carry over difficult ground; it can be deflated and inflated in minutes.  Further research may well uncover more boards on the European or American markets.

 

 

 

The DIY version

As seen in the French competition photos, the vast majority of divers make up their own boards. The boards I made up for the tests were constructed to compare two extremes of board design. The boards were constructed from dense polystyrene sheets sold as Glascofoam and Wallmate insulation at local DIY stores. These were bonded together with expanding foam, then trimmed and sanded to shape. A cover of stretchy cotton (old T-shirt) and waterproof PVA sealant forms a strong shell and prevents chunks being torn out of the polystyrene. The Expanding foam and PVA are also available at all large DIY stores.

 

The surface of the polystyrene sheets are roughened before applying foam then clamped together while the foam sets (approx 30 minutes). I found a saw best for removing large chunks, then a very sharp thin bladed knife for slicing off smaller bits. The final shaping is with a small curved Surform rasp, before smoothing off with a sanding block. Colour is added to the PVA sealant in the form of artist’s acrylic paint or can be sprayed on afterward. The PVA is not 100% resistant to water if permanently submerged or left outside all winter but it is fine for the normal usage of a float.

 

The heavy duty option involves covering the board with T Shirt and painting with resin. The standard polyester resin used in fibre glassing will dissolve polystyrene so an alternative such as West Systems Epoxy has to be used. This is sold at boatyards and will form a bullet-proof skin but it will add a lot of weight.

 

The total cost of making a basic board in this way with PVA is around £20.00 for all the materials and £20.00 for all the required tools if you don‘t have them.

 

Other DIY designs include two boogie boards, which are glued or strapped together with waterproof duck tape. The best type are the rubberised foam boards as they are much more durable than polystyrene and require no protective covering. The foam is easily shaped with a blade and some can be sanded. A cheap foam rubber boogie board will cost at least £30.00, a pvc coated polystyrene one can be much less but is more difficult to shape and much weaker.

 

A single polystyrene body-board, being thicker than a boogie board, may be suitable for the much smaller competitor. I would be tempted to cover one of these with the cotton & PVA skin mentioned earlier, as I know they can be broken in half while surfing. Most of these boards are the wrong shape to fix two together. A board like this can be bought for £20.00

 

Many of the French use what appear to be cut down windsurfing boards.

A wide, thick board used by beginners is required, as the front end of a “sinker” windsurfer or a long surfboard may not have enough buoyancy to perform well.

 

The outer plastic skin of a windsurfer or the fibreglass skin of a surfboard can be cut with a fine jigsaw and the polystyrene or foam inside shaped. The yellow two-part expanded foam fill in some boards is not totally waterproof and needs sealing with PVA when repeatedly submerged in water. This type of expanded foam can be coated with normal polyester resin without dissolving.

 

 

 

Solid versus inflatable

I would be cautious of using any float that relies totally on one inflatable chamber. I sometimes use double inflatable floats 3/4 filled with polystyrene balls from a beanbag so they can never go down completely if punctured. This idea arose after I spent a whole competition with one side of a double float punctured and the spare guns and equipment dragging in thick japweed.  At least I still had the other float to stop my equipment sinking altogether and disqualifying me for displaying no marker or flag.

 

 Many standard inflatable floats sold for spearfing can’t be relied on as a serious safety device. An emergency is no time for a 14 stone man to find out that his float is no more robustly built than a cheap blow up toy bought at the beach cafe.

 

The bladder-type floats now sold by many manufacturers have a tough outer cover over the inflatable bladder, reducing the chance of accidental puncture, they can still fail though. A float made of solid polystyrene or foam rubber is by far the safest option.

 

An easy way of making an unsinkable float is to start with one of the bladder floats.

Buy a roll of thin polystyrene insulation sheet, available at many DIY stores.

Bind the roll all the way with duck tape to stop it unrolling.

Cut roll to length and round both ends with sharp knife to make same size as blown up float.

Elongate the slit used for inserting the bladder into the float.

Cut the roll into 3 sections and insert rounded ends first then the middle section.

 

£5.00 is well worth spending to make a float unsinkable.