Setting up the Dredge

After you have decided on where you are going to dredge, as well as where you are going to discharge your tailings and where you are going to position you intake tube the area where your dredge is going to be anchored needs to be taken care of. All that is needed now is to find a place to anchor the dredge to.

However before getting into attaching the anchor points to your dredge there are two forces apart from pressure of the stream flow against the floats that need to be looked into.

One of these forces has to do with the moment of force around the dredge. Whenever a force pushes an object down the stream it has a tendency of rotating around its center of gravity. If you can picture a flat log floating down the stream you will know what we are talking about. As long as its advance is not obstructed it will keep on floating normally with the forces having a tendency of rotating it overpowered by the speed of the stream that is pushing it. 

However, if you were to attach two lines to the sides of the flat log close to the middle then it would not float down the stream anymore. Now that the strength that pushes the flat log would be resisted but those that have a tendency to turn it the other way around it’s center of gravity would be free to do as pleased. If the lines were adjusted close to the back of the log, the downstream area would be lifted for only a little distance. If these were attached close to the center this area could be lifted to a good height and the log would sink at the section upstream. Now the strength of the current would push and put forth enough to turn the log around the axis created by lines.

When a dredge is first launched, its center of activity is way over the water line and close to the back section. During this time the turning effect around the center of gravity can be very outstanding and if you are not careful, the dredge is able to turn over during launch. There will rarely be any problem when the launch is done in calm water or if the water is not any deeper than waist deep. The main problems occur when the dredge needs to be launched in deeper water or when there are stronger currents of water. There are some cases in which it is even necessary to weigh down the dredge with a big boulder.

This effect can also been seen when the dredge is launched or anchored sideways on the stream in where it presents its side instead of its back part to the current. This kind of anchor should only be done when there is no other choice and a downstream anchor of some kind is rigged up in order to maintain the dredge from turning in the current while the operation is going on.