How Our Mats Keep You Out of the Muck
The Taming of The Muck
Warning: this is a fairly nerdy article. I’ve tried to make it as interesting as I can for non-nerds. But if you’re curious about how a BoatLIft-Mat works, this is the best I can do.
Assuming you’ve read the “History of Muck,” you now have a better understanding of where your muck came from and what it’s made of. By using the very characteristics of muck (submerged soil particles) we can create a solution to the problem and make a firm base for your boat lift.
Four Soil Bonding Characteristics:
Soil particles have a certain amount of “friction” that holds them together. Think of facing two pieces of sandpaper together and trying to slide them across one another. On a very small scale, this is what happens with soil particles. They’re rough and tend to “stick” to each other.
Soil particles also “interlock,” meaning one particle has a pointy edge which finds another particle with an indentation that more or less matches it. Think of popcorn in a bowl. The natural tendency is for the popped kernels to settle into the others, until your hand disturbs them. But if you push straight down on them, they’ll “lock” together. Soil particles work the same way.
- Dilation – Castles Made of Sand
You know that trying to make a sand castle out of dry sand just doesn’t work. But, if you add the right amount of water, the sand sticks together and you can make some pretty fancy sand castles.But then a big wave comes up and your masterpiece melts away. Bummer…but a great clue: too much or too little water is bad, but the right amount of water is good for building sand castles.Remarkably, the right amount of water can help your muck stick together. “But it’s all under water!” you say, “You can’t have less water, it’s a lake bottom!” Well, yes and no.When you’re building your sand castle have you ever stopped to admire your progress, and happened to look down at your feet? If so, you may have noticed the sand around your feet turns a slightly different color, because the weight of your foot is pushing some of the water out of the sand, (think of it like stepping on a wet sponge, it’s still wet, but some of the water squishes out). The sand stays this way for awhile, it’s why you leave footprints in the sand. It’s called “dilation,” it helps stick particles together.
Another factor that helps soil stay together is chemical in nature. Calcium carbonate, the same stuff that’s in your anti-acids, like Tums, works as a sort of soil “cement.” It bonds with particles, glueing them together.So we’ve got four main factors that can cause soil particles to stick together, friction, interlocking, dilation and cementing.So far, so good. But there’s one other factor to consider: how much weight is your soil trying to hold up in a given area.
If you’ve got one pound and one square foot of soil holding it up, you’ve got a pressure of one pound per foot. Pretty simple, right? But, if you had 1,000 pounds on that same square foot, it would be a pressure of 1,000 pounds per foot. Yikes!
But, if you can spread that 1,000-pound weight over 1,000 square feet, you’re back to just one pound of weight per square foot. You’ve adjusted the “weight distribution” which is part of how snowshoes work. If your foot is four times bigger, then your weight at any point on the surface is going to be a lot less. You don’t sink in the snow.
If you looked at our BoatLift-Mat material with a big magnifying glass, you’d see it looks like a lot of tiny pyramids woven into the fabric. When you place the fabric on submerged soil, the first thing it does is trap the soil particles in the tiny pyramids. It creates “interlocking” of the particles.
Think of walking through mud wearing boots with thick cleats. Some mud sticks to your boots in between the cleats, then more mud sticks to the mud on your boots, then more and more mud, until you can hardly walk. It’s the same principle with the BoatLift-Mat.
The more “interlocked” soil particles there are, the more “friction” surface there is for other particles, and with right amount of water “dilation” the more particles stick together, the more opportunity there is for “cementing,” to bond the soil particles, (like the “cemented” dried mud left on your boots).
Now, think of setting your boat lift and boat in your lake. Let’s say the total weight is 4,500 pounds. There are four foot plates that are one square foot each. So each one has to hold 1,125 pounds (4,500 / 4). That’s a lot of weight for soil that has a very low “bearing load” capacity.
Now, think of putting that same lift and boat on a BoatLift-Mat where the weight is distributed over 225 square feet. If you divide 4,500 pounds by 225 square feet, you get just 20 pounds per square foot. You’ve transferred the “weight distribution” like a snowshoe from 1,125 pounds to 20 pounds per square foot. Much better, isn’t it?
Meanwhile, the pressure of 4,500 pounds squeezes some of the water out of the soil beneath the BoatLift-Mat, even though it’s still under water, there’s less water in the soil directly under your lift, allowing it to stick together better, kind of like your sand castle.
A BoatLift-Mat simulates underwater the factors that keep soil together on dry land, friction, interlocking and dilation. Cementing also occurs naturally under a BoatLift-Mat, but it’s a secondary process.
As for weight distribution, the area closest to the foot plates on your boat lift will always be holding more weight than the edges of the BoatLift-Mat. How much more? You’d need a geotechnical engineer doing some pretty fancy calculus to figure it out. But even if it were five times as much with our example of a 4,500 pound boat and lift, the area near the foot plates would only be holding 100 pounds per foot instead of the 1,125 pounds without it.