Frequently Asked Questions
I am getting some very good questions on both social media and the web page chat. Here I have done my best to answer them.
But isn't the cable is designed to be the weakest point? Don't you want the cable to break before the ramp or a post / winch stand? Won't it still be the weakest point?
Excellent question! The cables are your dock's lifelines. When a cable fails, the dock will then be free to move in the wind, gaining speed and increasing the impact load when it hits anything. Which will most likely one of the neighbor's docks you are surrounded by and which you will be liable for repairing. The walkway can be ripped from its mount on shore, which will be expensive to have repaired. The walkway to dock joint can be torn loose. A cable letting go is the last thing you want.
The cables are not the weak link. The smallest cable most use is the 5/16" with a minimum breaking strength of 8520 pounds and the more commonly used 3/8" cable is good for up to 14,400 pounds. Most docks use hand winches in the 2500 to 3500 pound working capacity. They have a minimum breaking strength of roughly twice that amount. The winch body will bend from the drum being yanked on until either the bolt passing through the drum fails or the teeth the locking pawl engage will no longer mesh with the teeth on the drum and release all the cable on the drum. The shore anchor is usually a post driven into the ground with some concrete around it. Most weigh less than a ton. If you want to get a tent peg out of the ground, you tap on its side with a hammer, then it comes out easy. Same thing happens over time with dock anchor poles. Dock moves a few inches in the wind, pulls the cable tight. Its kinetic energy becomes impact energy on the pole. Over time it gets loose. A storm passes through with a bigger wind that removes the anchor pole from its hole. Your dock is then loose to sustain/cause damage.
A dampener on each cable mitigates the shock/impact load that occurs every time the dock moves. Dock springs are a form of dampener. Dock springs introduce time into the formula used to calculate shock and impact loading. See the "What is Shock Loading" page for a better explanation of how time is critical.
Introducing time into each impact, slowing the loading of your components, is the only way to mitigate your dock's kinetic energy.
There are currently only two forms of dampeners and springs are the better choice of the two. Other than a dock spring, an elastic connection from marine high density polyethylene rope is your other choice. Rope is fragile, degrades with UV exposure and time, is easily abraded and can be cut. Marine HDPE rope has a 10% yield factor which is both good and bad. A dock with a 65 foot walkway secured with rope has a distance of about 93 feet from the dock to the anchor pole and will stretch 9+ feet when a load is applied. That is 18+ feet your dock can move back and forth. Its just not rigid enough. A dock spring has 6 to 7 inches it can compress when arresting the movement of a dock.
What hours are you available?
I want to shoot for regular business hours, 9 am to 5 pm, but open 7 days a week. Call me if you need further info about dock springs or help selecting a dock spring set for your application.
The web site says the springs I want are not in stock. Can I back order them?
As I figure out the demand for dock springs, I will fill orders as they occur. The materials I need are pretty readily available so the longest it will take to fulfill a back ordered set would be less than 10 days. I keep about 24 sets in stock.
How do you figure which spring my dock would need?
I make 3 sizes.
The Light Duty Dock Spring has 600 lbs./in constant compression rate and a pair would serve a swim platform up to a single slip single story dock well.
The next size up is the Progressive Rate Dock Spring with a progressive spring rate that starts at 1000 lbs./inch and ramps up as it is compressed. It will work fine for all docks as the resistance to compression increases with load.
The Overkill Heavy Duty Dock Springs have a constant spring rate of 2100 lbs. per inch and a one in thick solid steel bar compression links. All the others use 3/4" solid steel bar. They were created to handle the big dock loads seen on Lake of the Ozarks. If you have a large heavy dock on a main channel, these are what you will want.
Do you install different size springs on each side of the dock depending on which one has more tension because of current and wind?
Both sides should use the same size as wind comes from all directions. The current at my dock runs both ways, depending on wind. I have also helped dock owners put 4 springs on their dock. Overkill is underrated. Call if I can help.
Do they go on the dock side or anchor side.
They go between your cable end and what it is normally attached to. Some docks have the winches on the shore and some have them on the dock. Install the spring on the end of the cable opposite the winch. Some docks don't use a winch to control cable tension. It doesn't matter which end of the cable the spring goes on. I would put it on the end that is the easiest to reach. So long as it is between the load and the anchor, you are good.
Any issues with the eyelet pulling through the aluminum channel at the attachment point if In the dock side?
If you have had a problem with an attachment eyelet pulling out on your aluminum dock, I would put a steel backer plate on the backside of the attachment to spread the stress over a larger area. Saw this same problem on next door neighbor's dock. I made a 4" x 8" x 1/2" steel plate with a 9/16" hole popped through it for a backer. Been solid ever since. See the dock bulletproofing page.
What warranty do you provide?
Dock springs are made from very heavy duty components. The springs are OEM quality heavy truck springs and the compression links are 3/4" hot rolled bar stock. You could spend a full day pounding on them with a hammer and not break them. If however, you do experience a failure due to the materials or workmanship, I will happily exchange them. One thing you will find in almost every warranty is the phrase, "acts of God". There are conditions that exist in nature that will rip your dock off the shore, turn it upside down, boats on lifts and all, and stomp it like a bug. Nothing associated with a heavy duty spring on your anchor cables will mitigate that. So, if God breaks it, you are on your own.
How long should they last?
They are made of steel. Heavy steel. UV light won't break them down or weaken them. They may get a little surface rust on them in areas where the paint wears off but you won't live long enough to see a set fail from corrosion. The springs are brand new and designed to support a truck over hundreds of thousands of miles. They will not break from use. You will not wear them out. They will have a very easy life of absorbing your dock's movements. The set on my home dock are more than 30 years old and still performing great.
What about cable tension. Should I make my cable tight or loose?
There are 2 schools of thought.
Plan A is to have the cable tight enough to put a slight preload on the Dock Spring. This would basically eliminate any lateral movement by the dock. Movement is indeed bad as it allows kinetic energy to be created by any momentum your dock gains through its movement. This energy is what causes damage and failure.
Plan B is to have a slight amount of slack in the cable so the dock has the ability to move slightly to accommodate wake's effects on the dock and make it more pleasant to be on. On my dock, I have a 100 foot long walkway and 140 foot cables from the corners of my dock to the corners of my property where the anchors are. My cable runs from a winch at waist level to a pulley at the base that directs the cable towards the shore. The pulley is about a foot above the water. I run my cables tight enough to keep them out of the water, with about 8 to 10 inches of droop in the line. This does allow my dock to move less than foot left or right with the wind and up and down with wake. The weight of the cable is actually the first dampener in the system. It weighs about 80 or so pounds which must be lifted by the dock's lateral movement and this absorbs some of the energy from the wind that caused the dock to move.
While we are talking about the weight of the dock anchor cable as a dampener, there is a method of adding additional weight to the cables between the dock and the shore in the form of a chunk of concrete on a chain attached to the midpoint of the cable and allowed to hang from the cable into the water column, not touching the bottom of the lake. It is an effective low tech way to slow the initial movement of the dock. It does nothing to mitigate the shock or impact loading of the cable and its attachment points. A 5 gallon bucket full of concrete makes a pretty good line weight. Be sure to set up an attachment point with a stainless steel eyelet to attach your chain or drop cable to before the concrete dries. Google "catenary anchor" to see how weighted cables are effective dampeners.
Its common on my lake for a dock company to post on Facebook to the lake groups to put extra slack in the dock lines before a thunderstorm hits. Why? Might have something to do with the phone calls they will get after the storm to come fix docks. Movement is bad. Movement creates kinetic energy that breaks stuff. Slack cables allow movement. Slack cables contribute to dock anchor system failure. Rising water levels may affect dock cable tension, causing it to get tighter of looser based on the angles and elevations of anchor points involved. All dock owners should be aware of the water level of their lake and how it affects their cable tension.
Can I buy just one?
Yes and no... I get them in pairs. The math for margin on my side of the counter is bad for me paying shipping on just one so, yes. I can sell you just one but I can't afford to foot the bill on the shipping on just one. Once my free shipping to the 1st 100 customers is behind me, I will have springs on most bodies of water to get the ball rolling and I will edit the product page to make the springs an "each" instead of "pair". Shipping for a pair runs me about $75 to most of the country (except California... Add $40 to anything shipped into that state). So if you need just 1 or 3 or an odd number of Dock Springs, call. I can take care of you and get what you need to you.