Testing the Nida Core
Nida Core is a honeycomb of hexagonal cells bought in sheets. They are used for a variety of projects: placed below asphalt roads in boggy/marshy areas to aid buoyancy and longevity, floor and decking for marine and government use, etc. I'm not sure where Phin came up with the idea to use Nida Core to fill the three inch wide void between the outer and inner hull (between the ribs) or even where he had heard of Nida Core, but the beneficial uses continue to surface. The Nida Core will act as insulation in hot and cold weather, contain a puncture in the hull to a smaller area, and may even reduce the effect of hull compromise from collision, which is what Phin Sprague and Dick Pulsifer tested here: --Mak Sprague
Phin Sprague on Nida Core:
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"We have been experimenting with the Nida Core and impact strength of the hull. As there have been some concerns about the effectiveness of using Nida Core to fill the frame void spaces that theme has also played with the building crew. Besides being a pain to put it in the crew had a number of concerns about it doing the job I was intending it to. Which was #1 to fill the void between the frame bays and contain water intrusion resulting from an impact or abrasion in a grounding. We decided to build and test two original panels and two with the Nida Core. My nightmare premonition is coming in contact with the corner of a sunken container. To see what could happen in a violent impact. We decided to drop a substantial weight on the panels from various heights. |
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I had a 71 inch segment of 85# rail which weighed 157#. We attached it to a line and lifted it 9 feet over the two panels. The first drop shattered the panel without the Nida Core. The panel with the Nida Core sustained a dent in the shape of the end of the rail. Perhaps because we have nothing to compare it to we were pretty impressed. We decided to lift the rail up to 16 feet and again it only dented the panel with the Nida Core. Next week we are going to lift the weight to 30 feet over the panel and see what happens. I am not sure how to quantify the forces on the panel so I can compare it to the boat moving ahead at say 6 knots. Can you shed some light on this value. I tried. F=MGH where M=157 G=32 feet per second squared and H=16 feet gives 80384 pounds per sq. ft/second squared. |
 Dick Pulsifer and the Rail (Click to enlarge) |
| The end of the rail was 7 square inches so is the force of impact 80384/(7/144) = 1,640,489 pounds/ second squared? For a 70,000# boat at six knots ( 10 ft /second) F=1/2MV*V= 3,500,000#/sec squared. Hitting 7 sq. inches results in 7,142,8571# It looks to me that by dropping this weight from 16 feet we are at about 2.5% of the comparable impact load. If we double the height of the drop I conclude we should be at 5% of the comparable impact. Can this be correct? If not how are these loads related? I realize that this is a very simplistic model that I am trying to develop, but I have found the results of the drop test comforting in demonstrating the comparative strength of the panel with the Nida Core and the sudden appreciation and lack of bitching about something new from the building crew." -- Oct 28, 2000 |  Panel Without Core (Click to enlarge) |
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| Panel after first strike. (Click to enlarge.) |
Panel after second strike. (Click to enlarge.) |
Later Trials
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| Sighting Down the suspended rail. | Ready? |
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| SET! | WHAM! |