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Breaks Happen
Before I started on this article I had a discussion with the boss on how to write it. Actually, it became a rather heated debate, but in the end it was decided the topic was good and needed to be addressed. How to explain it was going to be the hard part. Here goes.
Over the past couple of years we have been seeing an increasing number of propellers coming in with broken blades. These propellers have been produced by a range of manufacturers from the world's largest to local hand-builders. They've been made by every manufacturing method, one piece castings to weld-on blades. Naturally, when something's broken you suspect somebody hit something; but the owners claim otherwise. There is however one consistent theme; and that would be the type of hull they have been running on. You guessed it, shallow-water tunnel boats, one of the toughest propping jobs.
So the question arises: Why are so many props breaking in this application?
Well, the answer is, "loading" and the easiest way to explain it is, "the paper clip effect."
If you take a piece of metal and bend it back and forth enough times it will eventually become fatigued and break. This is exactly what happens in a ventilated tunnel application.
With every revolution of the prop shaft, the blades undergo loading and unloading. Think of it as the blade flexing every time it bites the water. At first this doesn't sound like much, but add water pressure on the blade's face and repeat about 2500 times for every minute of operation and you will find the blades get a workout. The effective pressure is magnified by the area of the blade, the amount of cupping, as well as the water/air ratio going through the tunnel. This doesn't even begin to get into the real pressure added to a blade as it is screwed through mud or sand while trying to get a fully loaded boat on plane in skinny water.
Look, we know you are going to use your equipment to its maximum, but most go way past that. Just listen to a flats boat as it cruises the shoreline right before it cuts off your quiet morning wade. The sound of the motor is constantly changing with the loading and unloading of the propeller, and that propeller is taking an awful beating.
One of Scott's comments during our discussion... "Fishermen need to think about it like this, if you took your car four-wheeling a couple of times a week for several hours each time, something's gonna break." He has a point. So be prepared, be diligent in checking your equipment after each use, and most of all -- Be Careful!
Over the past couple of years we have been seeing an increasing number of propellers coming in with broken blades. These propellers have been produced by a range of manufacturers from the world's largest to local hand-builders. They've been made by every manufacturing method, one piece castings to weld-on blades. Naturally, when something's broken you suspect somebody hit something; but the owners claim otherwise. There is however one consistent theme; and that would be the type of hull they have been running on. You guessed it, shallow-water tunnel boats, one of the toughest propping jobs.
So the question arises: Why are so many props breaking in this application?
Well, the answer is, "loading" and the easiest way to explain it is, "the paper clip effect."
If you take a piece of metal and bend it back and forth enough times it will eventually become fatigued and break. This is exactly what happens in a ventilated tunnel application.
With every revolution of the prop shaft, the blades undergo loading and unloading. Think of it as the blade flexing every time it bites the water. At first this doesn't sound like much, but add water pressure on the blade's face and repeat about 2500 times for every minute of operation and you will find the blades get a workout. The effective pressure is magnified by the area of the blade, the amount of cupping, as well as the water/air ratio going through the tunnel. This doesn't even begin to get into the real pressure added to a blade as it is screwed through mud or sand while trying to get a fully loaded boat on plane in skinny water.
Look, we know you are going to use your equipment to its maximum, but most go way past that. Just listen to a flats boat as it cruises the shoreline right before it cuts off your quiet morning wade. The sound of the motor is constantly changing with the loading and unloading of the propeller, and that propeller is taking an awful beating.
One of Scott's comments during our discussion... "Fishermen need to think about it like this, if you took your car four-wheeling a couple of times a week for several hours each time, something's gonna break." He has a point. So be prepared, be diligent in checking your equipment after each use, and most of all -- Be Careful!