Inflatable Paddle Board Constructions:
Inflatable Core Layups
All inflatable paddle boards start with an inner bladder made of drop stitch fabric. Drop stitch, in a general sense, consists of two parallel sheets of fabric which are connected by thousands of 5-inch or 6-inch length threads. When the edges of the top and bottom fabric sheets are joined by air-tight material and the bladder is inflated, the threads confine the movement of the top and bottom sheets so that it maintains a board shape rather than curving outward like other inflatable objects.
The inflatable core of a paddle board is made with a single layer (with several variants), fusion, or dual layer construction, while the rails are made with single or double rail bands, and in some cases and additional reinforcing strips for rigidity. Here’s a basic description and additional comments regarding each construction:
Single Layer (Drop Stitch Fabric + Plastic Coating)
In a single layer construction, the drop stitch core is made from single ply sheets of fabric at the top and bottom, which are sealed with a layer of flexible PVC plastic coating.
Single layer drop stitch is what you’ll find in most boards below $700. The material is not very rigid inherently, so boards made this way are almost always 6 inches thick, even if that is not the optimal thickness for the performance of the board. Boards made with single layer construction have a bouncier feel and are more susceptible to puncture and leakage. Some companies are using single layer constructions but giving there materials made-up names to imply they are a fusion style material. It is another area where a buyer has little information to go on other than what is claimed by the manufacturer, and since there is no universally accepted naming convention, many companies will take advantage of this.
It is also very common for companies using single layer materials to compensate with an over-the-top rail layer setup (implying 3 or 4 'layers') that offers no actual benefit because, if the core is weak, you cannot add strength to it after the fact.
ERS does not use single layer construction in the manufacturing of any SUP boards.
Fusion (Drop Stitch Fabric + Woven Fabric + Plastic Coating)
Fusion construction is a sweet spot for balance of weight, rigidity, and cost effectiveness. The top and bottom sheets of the drop stitch have two layers of fabric that are permanently bonded to each other, and a layer of PVC coating on the outside of this double ply fabric. The resulting board is significantly more rigid and puncture resistant than a single layer board. Expect this construction in boards from $900 and up. The added rigidity of the material allows boards to be made in 5” thickness without having to resort to excessive board thickness for the sake of rigidity.
As mentioned a trend of great concern is manufacturers implying the use of fusion materials on boards that are actually made of single layer fabric. Some creative layer-counting takes place for the sake of advertising, so read construction claims critically. A common practice is to count adhesives or coatings as 'layers, which muddies the waters quite a bit with regard to the actual composition of the materials used. The use of crossed weave single layer has become common in single layer boards who make the claim the material is fusion or dual layer but this is not the same thing as authentic fusion or dual layer construction.
Another interesting take is calling fusion boards 'dual layer fusion'. By definition all true fusion boards use a double layer drop stitch so any implied advantage to 'dual layer fusion' is null.
ERS uses fusion material and construction in its SKYLAKE series boards.
Dual Layer (Drop Stitch + Plastic Coating 1 + Adhesive Layer + Plastic Coating 2 + Woven Fabric + Plastic Coating 3)
Dual layer construction is is the “cost is no object” inflatable layup, as it involves additional materials and labor to build the board. It starts with an inner bladder made with single layer construction, but then the entire bladder is laminated with an additional sheet of PVC coated fabric. Boards made this way are superior in durability, rigidity, and rocker profile control and are more difficult to puncture and less prone to leakage since they have additional coating layers between the fabric sheets. The additional layer adds about 3-4 lbs to board weight and a significant increase in material cost. This construction can be used to produce a board that feels extremely well balanced and grounded underfoot.
Technically, fusion material also has two fabric layers, but it should be noted that there is a distinct difference between fused material boards (two layers of fabric fused at the raw material stage, with a single coating applied to the outside surfaces) and actual dual layer construction boards, in which a second distinct layer of PVC coated fabric is laminated to the board. Dual layer construction generally adds about 3-4lbs to the weight of a board, so comparing board weights can help you discern whether a board is truly made with two distinct layers of PVC coated fabric or if a brand is advertising with creative wording to imply additional layers that don't exist or are non functional for rigidity or durability.
While some manufacturers may be using use similar materials, different methods of constructing the board can make the most impact on the longevity and performance of a board. ERS uses dual layer construction in its DUAL series boards, using proprietary construction and assembly methods.
The rail, or edge, of an inflatable SUP is made by joining the top and bottom sheets of the board with strips of reinforced PVC coated materials in an airtight manner. The physical properties of the materials used to form the rails can have a significant effect on the rigidity and performance of the board.
Single rail band with taped seams
A single band of PVC coated fabric along the sides of the board is the cheapest way to close off the containment layer, but the most vulnerable to puncture and leakage. It is most often used in low quality boards where every optional cost must be eliminated. Boards made with single layer rails can often be identified from the 1 inch width strips of PVC used to tape or cover the rail seams.
Dual rail bands
In dual rail construction, an inner band seals off the containment layer and a wider second band is bonded over the top of it. This is the most common rail configuration, but details on how it is implemented can make a significant difference in board strength. Boards with a larger gap between the edges of the drop stitch layers (less overlap with the inner rail band) are easier to build but have less structural integrity than boards where the drop stitch fabric layers fold farther over the sides leaving a narrower gap to close with the rail band.
Dual Rail Bands + Stiffening Layer
Adding a strip of low stretch (high tensile strength) material to the rail can improve rigidity while providing an additional layer of puncture resistance. It is also an area where false marketing claims abound. Hint: Carbon fabric serves no mechanical function as a rail stiffening material. Carbon fiber must be impregnated in an epoxy resin to realize its potential strength, in which case it becomes extremely rigid and impossible to fold. The addition of carbon fabric tape to rails is actually a surfing board throwback to tune a hardboard shape and carbon tape is pliable and useful for that specific application. Carbon fiber is great for rigid and lightweight paddles, but provides no significant structural or ridgidity benefit on the rail of an inflatable SUP board.
An example of correct implementation of a stiffening layer on a rail is our Enhanced Dynamic Rail (EDR™). This is an innovation in rail stiffening technology using a unique high tensile strength material band applied in a propriety construction method. The EDR™ is designed to provided resistence when force is applied by a rider through turns and waves.
Heat Welded Rail
As of 2019, some manufacturers are experimenting with bonding the rail layers using heat to join the PVC instead of adhesive layers. Doing so has potential to reduce manufacturing costs, which is why it has been adopted, but the jury’s still out on whether boards constructed with this technique can match the dimensional integrity and longevity of boards bonded with more expensive adhesive based methods.
Heat sealed or welded rails are somewhat of a misnomer as the weld is usually a partial connection over the inner fold while the core construction of rail is completed with adhesive. A variant of the techniques "welds" the underside of the inner seam and uses adhesive for the top part of the inner seam and the entire outer seam. Inflatable boards require adjustment during the setting process so a completely welded rail would not allow this to occur. There are some minor variations to the welding technique though the mechanical and chemisorption strength properties of a purpose specific adhesive used to permanently bond the sections of the board, can be as strong as the base material itself providing incredible durability, reliability and longevity.
Construction processes differ between manufacturers / factories to a degree so the assumption that everyone uses the exact same adhesives, techniques and processes is incorrect, though some standardization and techniques are commonplace.
The construction of a performance stand up inflatable paddle board is a synergy of materials, outline shape and manufacturing processes. Getting it right is expensive and time consuming since the end product is only as strong as its weakest link.
A Final Note On Board Construction
Most of the construction details described here are completely invisible to the paddle board buyer. As a result, some companies, particularly on the lower to mid end cost end of the market, are hyping their board constructions using misleading language to imply additional material layers that do not really exist on their boards - or - have no actual effect on design parameters such a rigidity / durability they claim them to. Review websites and press releases will usually just rely on this and repeat the companies claim (we give them the benefit of the doubt they are not required to know the ins and outs SUP construction). Sadly, just because something is repeated over and over it does not become truth, though the perception of it being truth or fact can gain momentum.
If a corner can be cut often it will be to the detriment of the buyer, the industry and the environment. Cheap glue, core materials and lower density EVA are common place at the low to mid end of the market and even among some more well known brands.
For this reason, we advise caution in believing unsubstantiated marketing claims. To protect yourself, we recommend getting to know the brand you are buying so you can feel more confident in knowing you are getting the construction that is advertised.