The first step in the design process is choosing the correct blank. Most surfboards are made with polyurethane foam (PU) or expanded polystyrene (EPS). A good surfboard can be built using either one or the other. The past few decades have brought new, sophisticated and more eco-friendly components into surfing, or resurrected materials used in the past, but the foam / resin combination remains the most popular choice around the world. We will deal with these two blank options, on the basis of which choice, all other decisions will fall. Our suggestion is to evaluate the pros and cons of all materials, both from an economic point of view, the quantity of manpower and ease of processing and from the point of view of the final product.

BLANK PU

Polyurethane Foam (PU) Blanks have been the foundation of the surf industry from the 1960s to the present day. Most PU blanks have a standard density (often various brands PU blanks offer various densities) of 3 pounds per cubic foot, approximately 48 kg / m3, much denser and heavier than Styrofoam blanks (2lb / ft3 or 30 -35 kg / m3), with a smaller cell structure. For this reason, boards built with PU blanks make the ride smoother in less than perfect conditions, absorbing chops and vibrations more effectively than EPS blanks.

The PU blanks are supplied with a wooden stringer already inserted and this saves time both in the processing phase and, as in the construction of longboards over 9 feet, in the search for suitable woods.

Another less concern when working with PU blanks is that the lamination can be done with either polyester or epoxy resin. Normally polyester resin is used as the use of epoxy resin on PU blanks, both much more expensive than their respective alternatives, will lead you to spend a significant amount.

Another feature of the PU blanks that make it preferable in this case to the EPS blank is the lower water absorption capacity. During a session it often happens to break the board, perhaps after bumping it against a rock. Well, with a PU blank you can easily, in less serious cases, stay in the water and maybe continue to use the board even in the following days, perhaps putting a piece with a good American tape. The absorption of water is minimal and you can safely dry the damaged part once the sweel is finished.

From the point of view of the shaper, working a PU blank will be much more satisfying due to the compactness of the foam which makes it pleasant to slide the tools. No cracks or blisters of foam leaving, the surface of a PU blank is firm and hard, and the activity is closer to that of the sculptor. A completely different feeling compared to the processing of EPS blanks, so much so that all shapers can agree in the simple phrase "a real PU blank is a whole other thing !!"

There are also internal differences between polyurethane blanks and polyurethane blanks. There are now many countries where companies have launched blankets for the surf industry. Not all donuts come out with the same hole. Almost all the shapers agree in giving extreme importance to the choice of the blank brand both from the point of view of processing and that of the final result. In processing, an excellent blank has a polyurethane foam formula that is the result of years of research applied to surfing. In addition, the dimensions are fundamental, a wide choice to accommodate the various projects and limit the roughing work. The squareness and precision of the surfaces is a fundamental element, so much so that not everyone is able to have satisfactory results in this sense. Excellent blanks can have different characteristics, some more useful for one purpose, others for another. For example, the hardness of the surface has consequences on workability and resistance to bumps. A good blank must be able to reach the right compromise between these two factors. Within this range, which includes the best brands of blanks, different philosophies are distinguished: those who prefer workability with a wink to the shaper, those who prefer hardness thinking more about the surfer.

The choice of an excellent blank is essential for a handshaper, especially if a beginner, focusing on blanks well made in the shape and formula of the foam, easier to sand and with a large catalog to help save time in working to get to the desired shape. We are proud to have brought the distribution of USBLANKS to Italy, undoubtedly the spearhead among the blanks in the world. Born from the bowels of Clark Foam, Usblanks is ideal for the beginner and for the professional and for the surfer who will take him into the water.

BLANK EPS

EPS Blanks have also been used in surfboards for decades, but their use was put aside when Clark Foam in Polyurethane Foam was invented. Australia followed the invention so the market was literally diverted to PU Blanks. Never completely abandoned, EPS blanks have only come back into fashion in the last 10/15 years, coinciding with the closure of the Clark Foam factory in 2005 in the American context. Always starting from the USA, the rediscovery of polystyrene as a base for surfboards led to a study of the techniques and benefits that this material could offer to the surf industry. These boards have demonstrated a higher strength / weight ratio than polyurethane, allowing for increased strength and reduced weight. Right now the most popular surfboard brands, Firewire, Lost, Heyden Shape use polystyrene blanks to produce their boards, as well as some of the best surfers in the world, use EPS boards in both freesurfing and racing in the World Tour. Currently the EPS is particularly popular for small-medium wave boards, where buoyancy and weight are important factors, but they are also gaining popularity in big-wave guns and performance longboards, where the drag ratio / weight is very important. Furthermore, a polystyrene blank is significantly cheaper than a PU blank.

The cons of this material were the greater water permeability inside the polystyrene cells, a greater amount of work compared to a roughly pre-shaped clarkfoam and the mandatory use of expensive and "difficult" epoxy resin. It is essential to know that when laminating on an EPS blank (or XPS, we will explain this material to you below) epoxy resin must be used. Epoxy resin is needed as its alternative, polyester resin, contains Styrene, a solvent capable of dissolving polystyrene. Not bad since epoxy resin is much more resistant than polyester resin.

Let's see in the list the main reasons why the EPS / EPOXY combination was abandoned:

1) From an economic point of view, the savings obtained with polystyrene will be entirely lost on the higher cost of epoxy resin, two or three times as much.

2) The epoxy resin is also much more in need of care and "affection" than a polyester. It requires precision and attention in the mix of the two components, greater control of temperature and humidity, long, often very long hardening times, greater protection from dust and dirt. In short, not really an "easy" subject.

3) A polystyrene blank is also more difficult to work, as compared to polyurethane it is more fragile and it is very easy to ruin it with the probable detachment of parts or blisters that will have to be subsequently repaired.

4) Furthermore, the amount of work to be spent in the shape and glassing phase will be greater. The project was obtained starting from a parallelepiped block. A stringer had to be added to reinforce the break. In addition, it should not be underestimated that the epoxy resin has much longer hardening times than a polyester, so that it will be necessary to wait a long time between one processing and the other. All this is absolutely not functional to industrial production.

5) Last and biggest flaw, it is the air space between the closed cell pearls that traps and holds water. By itself, polystyrene of good density would not absorb water. Try to leave it outside during a non-stop rainy day. The problem arises when the polystyrene is closed in a fiberglass "skin". The sensitivity to the change in pressure and heat, caused by the presence of air between the closed cells that make up the block, causes absorption when the board breaks. After absorbing heat on the beach or in the car, contact with colder water and a simultaneous break in the fiberglass coating causes water to be absorbed inside. The more water absorbed, the harder it is to escape, causing weight gain and yellowing.

6) Always linked to the same cause, the thrust towards the outside of the air inside, stressed by the heat, can cause a detachment of the laminate, that is the phenomenon more commonly called delamination. Being a matter of internal / external pressure difference compared to the surfboard, even a trip by plane can be very dangerous.

Another type of polystyrene, or more commonly polystyrene, is Extruded Polystyrene (XPS), produced precisely through an extrusion process. Unlike its similar, it behaves much better with respect to water absorption, but compared to it it is more prone to delamination. This material is also more expensive and difficult to find, although in some construction companies it is possible to find parts according to your needs. Only if you adapt to the available colors and sizes can you save a lot. With this solution the costs will be even higher than the previous two combinations PU / POLY and EPS / EPOXY, since also in this case epoxy resin will have to be used.

BUT IF POLYSTYRENE HAS ALL THESE DEFECTS COMPARED TO OTHER MATERIALS WHY CHOOSE IT?

We will not give any final judgment on which is the best material, but on the elements on which everyone can evaluate from time to time based on their project. First of all we come to the advantages that the EPS / Epoxy combination has compared to its more famous alternative.

In terms of performance, the board made of EPS / EPOXY will be more resistant and at the same time lighter. The weight / resistance ratio will be so much better than the PU / POLY combination that it will be possible to obtain greater performance while improving resistance at the same time. The weight difference of the final product is evident, thanks first of all to an extremely different foam density. With this type of difference, in the case of an EPS board, you can decide to increase the amount of fiberglass for lamination by increasing its resistance while always remaining below the standard weight of a PU / POLY board.