ThruFlow TM -- Marinas, Commercial Establishments and Homeowners often require ramps to transition from the land to floating docks to accomodate the tide. Depending on the steepness of the ramp there is a legitimate concern of slip and fall accidents. The defense against slipping is good surface friction. There are many environmental factors that influence a choice of the material for the deck of your ramp. We believe that ThruFlow™ is an excellent choice for ramp applications. Although inclines and ramps are the most challenging, once you experience the many benefits of the material you may want to use it for your fixed and floating dock and pier surface as well. Other articles on this site will focus in on other specific benefits of this highly engineered product.
Friction Considerations:
- How is the friction achieved ?
- How is friction measured ?
- What formal Qualification Tests are Available ?
How Friction is Acheived:
Most people's instinct is that if something is going to do a good job as a non-slip surface it has to hurt bare feet. Not so ! ThruFlowTM has achieved a very comfortable bare foot feel while still retaining excellent foot and shoe gripping power. Alternative materials often use a grit material on the surface of the deck material. Not only is this surface sanding your feet as you walk, the sand grit grains tend to slough off over time. This promotes a poor appearance and also looses its initial gripping power.
ThruFlow is injection molded from Fiber Reinforced Polypropolene. These injection molds are quite huge and very expensive. However, use of a mold ensures that each piece of ThruFlow is almost exactly like ever other piece. Precision on the order of a few thousandths of an inch are routine. Very fine detail can be built into the mold. The particular detail feature I wish to call to your attention is the knurled surface. These precision knurls are actually little bumps in the plastic, they are not added on after the deck panel is manufactured, they are actually part of the panel. If you have a good eye or better a magnifier you will notice that these bumps have rounded top surfaces. If they were pyrimidal in shape, they would have a sharp top and that would increase abrasion of the foot, and such a small pointy feature would inconsistantly wear down anyway.
It is this molded in knurled surface feature that gives ThruFlow Deck Panels its Gripping Power.
Friction is Measured by Slip Force:
If you remember your High School physics, and who doesn't ?, friction was expressed by f = µN, where f is the force it takes to slide a mass pressing against the surface with N force. For Thruflow, µ = 0.78 for static friction ( friction to start sliding ) and µ = 0.76 (a dimensionless constant) for dynamic friction. This information is on the Thruflow site at http://thruflow.com/specs.asp . There is an nice article on friction at http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html, just in case you forgot about it.
I am told by Derek, General Manager of Thruflow, that there is such a thing as too much friction. I'd guess if your foot can not rotate off the surface without sticking walking could be uncomforatble. Somehow, Thruflow determined that 0.76 is just about right for pedestrian traffic.
One thing that is splendid from an engineering standpoint, the dry and wet friction specification of ThruFlow is the essentially the same.
WOOD: Now lets just take a quick look at wood, and I think lumber composites aren't much better. From a Wikipedia article on friction they list the range of friction for wood, both wet and dry, and there is a dramatic difference between the two circumstances.
ThruFlow Wood Dry Wood Wet
0.76-0.78 0.25 - 0.50 0.2
A bigger number is better of course. The reason there is a large range with wood is that there are many types of woods, and also is it rough or smooth ? The wikipedia article refereneced is at http://en.wikipedia.org/wiki/Friction .
Australian Qualification Test:
No one wants a preventable accident on a project one has designed, installed, or purchased. I'm sure there are a number of things that can be done to ensure one has done their due diligence in design and implementation. A number of factors may come into play.
Did you touch it, feel it and walk on it? Did you have an outside party review the product in the context of the application ? Was there a rigorous laboratory style review ?
Many modern nations have government and indepenent laoratory standards for many products and applicatoins. Fortuanately for us, not only do we have outside laboratory reports for the ThruFlow panels product, but we also have a specific Australian test related to Ramps and Wet Ramps at that. In short, its says its good to an angle to 29.31°.
You may be interested in adding this spec to your engineering proposal or bid quote package. You can find the information oni the ThruFlow site at http://thruflow.com/specs.asp . Specifically look for the PDF file to the right of the row labeled, Wet Barefoot Ramp, AS/NZS 4586:2004 . This is a copy of the official test report carried out specifically on the Thru-Flow Interlocking Panels in 2006. A direct link to the report at the time of this writing is http://thruflow.com/pdfs/20061030/wet%20barefoot%20test.pdf .
Just in case you want extra credit, or enjoy reading how this test and others are done, here are a couple of links for fun reading. I especially like the phrase [It is not necessary for the test person to actually fall. ] Well, I'm glad of that. http://www.globalsafe.com.au/barefoot_device.php A more general document is http://www.globalsafe.com.au/overview.php . If any of these links fail to work, please let us know. Things do move around on the web.
For this issue or any other, if you have a need to qualify something or back up a claim made in our literature, please contact us. If we don't know, we'll start diggiing up the answer. Having a well thought out standard defined and approval of that standard, whether from the USA, EU or Australia is a great thing.
