Standardizing Rigidity for Inflatable Boards and Boats - Introducing The R-Factor

 

 

Choosing between all the various inflatable paddle boards and kayaks on the market can be a challenge without good information to help make meaningful comparisons.

Inflatable paddle boards, kayaks, surfboards and other watercraft have become incredibly widespread and popular thanks to their convenience and portability. With the proliferation of “me too” and Amazon-only “brands” it’s become increasingly difficult to discern between higher and lower quality products.  One variable that receives little attention until you hit the water and find out how important it is, is rigidity.  The rigidity of an inflatable affects much of the user experience. Floppy inflatables with poor rigidity (aka “wet noodles”) negatively impact stability, how much capacity they can handle, how fast they do (or do NOT) travel over the water, how well they cut through choppy waters and more.  

There’s a good reason one of the top search terms for people researching a paddle board purchase is “hard paddle board vs. inflatable paddle board”.  Over the years the market gradually (back in the early 2010s) then rapidly (around 2015-2017) moved away from hard (also known as rigid or epoxy) boards towards inflatables.  Despite the unique sensation of glide and speed combined with stability that hard boards offer, they’re also impractical for most people due to their size and difficulty to transport and store. Inflatables solve that problem - they’re incredibly convenient, portable and also surprisingly durable.  During this time inflatable technology also improved, resulting in an acceptable level of performance (meaning stable enough, with decent glide and speed over the water for many people).  

Brands have tried to distinguish themselves from the competition by increasing rigidity in an effort to deliver the performance of a hard board with the convenience of an inflatable.  Various methods have been employed, from making the materials thicker to creating multiple chambers of air to adding cables down the center!  All of these efforts are lauded as “more rigid” and an improvement over other boards. Unfortunately there’s no way to really know if and how much more rigid they are! Except for marketing campaigns and the occasional attempt to put sandbags on the board between two sawhorses and measure how much the board bends, there’s little reliable, objective information to support the various claims.  What is needed is accurate, repeatable measurements that give customers factual information about the rigidity of the board they’re about to spend hundreds (or thousands) of dollars on.  

Testing a board with InfinityFiber material, which we now know increases rigidity by over 200% compared to the exact same model without InfinityFiber.

Rigidity difference is easy to see in the videos, and with the R-Factor we can quantify precisely how much more rigid one board is compared to others. 

At ISLE we’ve committed to changing this and are ready to offer a solution that every brand can adopt to help customers better understand what they’re buying.  During the R&D process for our new award-winning PRO Series construction (Popular Science Top 50 Innovations of 2023) we were looking for a scientific, data driven method for measuring rigidity in a way that we could repeat over and over again, knowing the method we were using was the exact same for each board being tested.  

ISLE received the prestigious Top 50 Innovations of the Year award from Popular Science in 2023 for creating a new class of inflatables dubbed Inflatable Hardboards. InfinityFiber, a patented ISLE-exclusive technology, increases the rigidity of inflatables from 200-300%.

During this process we learned a TON about how rigid (or NOT rigid) many inflatable constructions are!  The end result for us was confirmation that our PRO series construction, featuring our patented InfinityFiber material, increases rigidity between 200-300% compared to typical inflatables, a huge leap forwards for the industry!  At the same time we realized that our rigidity measuring methodology could be used across the industry to validate (or disqualify) all the marketing hype using scientific data.  We call this method the R-Factor (Rigidity Factor), and here’s how it works. 

An ISLE Switch being tested on the Instron. Note the length of the piece that is applying the pressure is the size of a typical human foot to approximate a person standing on the board.

Working with our partners at Inflatable Composites we send boards to a lab with an Instron, a huge computerized deflection measuring tool. The Instron loads the boards with a predetermined weight, then accurately measures the deflection, or bend, of the board under the weight. All boards are put through the identical test, and the deflection (or “bend”) measurements are accurate to the 10th of a millimeter. To control variables and create a test that is relevant for watercraft, we inflate all boards to 15psi and load them with 220 pounds of weight across a 5 foot span in a 4 point bend. The machine applies steady pressure until it reaches 220 pounds of downward force in between two supports that are 5 feet apart.  This allows us to compare the bend of different boards very precisely, under controlled conditions.  Next, we take the deflection measurement and multiply by a factor so it can be translated to a 100 point scale for easy comparison among different boards. This way we can see where each board or boat lands on the 100 point scale.  This is the R Factor. 

One great thing about the R-Factor scale is that it’s open-ended, so boards can achieve a result above 100 as construction technologies progress. As of today 99 is the highest R-Factor we’ve ever measured for an inflatable. Another important detail is that the board dimensions must be included in the analysis to ensure all variables are considered.  For example a board that is 6” thick will be more rigid than a 4” thick board.  Also, boards that are wider will be more rigid than narrower boards.  The best “apples to apples' comparisons come with boards that are the same thickness and width (length is less important, since the span is a constant at 5 feet). 

Here’s a table with some sample measurements and a graph to see how it works: 

Board Description (10'6 x 34" x 6")	Maximum Bend (millimeters)	R-Factor***	Rigidity relative to Generic board
ISLE 2.0 Gen Pro Series* (2024)	20	99	285.0%
ISLE 1.5 Gen Pro Series* (2023)	21	95	275.0%
ISLE 1.0 Gen Pro Series* (2023)	23.2	87	195.0%
ISLE Pioneer 2.0 (2022)	32	60	165.0%
Generic Inflatable**	58	34	100.0%
*Pro Series boards feature InfinityFiber, resulting in a dramatic increase in rigidity.
***Generic Inflatable uses the cheapest, most common construction available and make up the majority of inflatables on the market. We consider this the "baseline".
*R-Factor converts the max bend number to a 100 point scale for easier comparison. This is done by inverting the max bend and multiplying by 2000. The scale is open ended, so boards can achieve above 100 as technology improves

This graph shows various boards (inflated to either 10 or 15psi), and how much they deflect, or bend (x-axis), as the load of the Instron increases (y-axis).

In summary, we’re thrilled with how the R-Factor allows us to understand how rigid our own products are, and we’re even more excited about the potential for the R-Factor to become an industry standard to the benefit the customer trying to compare different inflatable boards and boats.  

Brands interested in having their boards tested at the Inflatable Composites independent third party testing facility can contact Dirk Steinhour directly at dirk@inflatablecomposites.com