02-20-2007, 10:06 PM
[left][font "Impact"][#000080][size 5]Walk Sideways With Bow Thrusters [/size][/#000080][/font][/left] [left]
[font "Verdana"][#000080][size 5]S[/size][/#000080][/font][font "Verdana"][#000000][size 2]mooth maneuvering is easy on the open water, with one foot on the wheel and one hand on an icy drink--until... the time comes to dock with the wind in the "wrong" direction. Suddenly, you have two[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic27.jpg"]![[Image: bow_thrust_pic27_small.jpg]](http://www.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic27_small.jpg)
[/url] hands on the wheel and your feet are sweating while you try to maneuver your 30,000-pound trawler in between two toothpicks with million dollar boats on either side. Some in this situation might say, "No problem, I have bow thrusters" while others might say, "holy @&%*!" If the time and money is right, bow thrusters are a worthwhile investment for any trawler owner. Here's an overview in the world of bow thrusters from some common names in the industry.[/size][/#000000][/font][/left] [left]
[font "Impact"][#000080][size 4]History[/size][/#000080][/font]
[font "Verdana"][size 2]I[#000000]n a crude form, bow thrusters have been around since the early 1900's. In these early years, mariners discovered the usefulness of the bow thruster to help steer in close quarters. The modern bow thruster has the same basic concept. However most New England fisherman, especially the long-liner, uses the bow thruster not for docking but for slow precision net tending in the ocean. A fishing vessel can stop dead in the water and use thrusters to move about the nets.
Some mariners will let their macho pride show when speaking of thrusters, "If you can't dock a boat without thrusters, you don't need to be on a boat". Hey, if you can financially and physically own and use a piece of equipment that makes life easier and safer...go for it! Besides, tell a tugboat captain he is not a man because he uses a bow thruster and see what kind of response you get!
Once you've decided that a bow thruster is right for you, choosing the right one can be a bit confusing. The manufacturer you choose will be more than happy to point you in the right direction, but here's a little head start. [/#000000] [/size][/font][/left] [left][font "Verdana"][size 2]
[/size][/font][font "Impact"][#000080][size 4]Things To Consider...[/size][/#000080][/font]
[font "Verdana"][#000000][size 2]The LOA (length over all) and displacement are main considerations when choosing a bow thruster. Thrusters come in two forms: electric or hydraulic. The form of propulsion is solely the buyer's discretion. It's uncertain which is more efficient, each manufacturer claims personal glory for their form of thruster. Thrust exerts horizontal outward pressure and determines the size of thruster needed, not electric motor size or hydraulic output. Thrust is usually measured in thrust per kg (kilogram). For example, Side Power (a bow and stern thruster representative) distributes a 35S model bow thruster, which has a thrust of 35 kg or 77 lbs.[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic_25.jpg"]![[Image: bow_thrust_pic_25_small.jpg]](http://www.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic_25_small.jpg)
[/url]with a 3hp 12-volt motor. Bare in mind this thrust load is at optimum performance (i.e. perfect batteries or perfect size and length hydraulic hose without a single leak, etc.). This thruster is recommended for smaller vessels 25-32 feet. If your displacement is greater than most of this length, such as a Willard 30 full displacement trawler, you may have to step up one notch to get acceptable performance. At the other end of the scale would be Side Power's 285-TC bow thruster with a whopping 285 kg or 627 lbs. of thrust. You could turn this thruster around and use it for main propulsion! This model is for vessels up to 80 feet in length.
Bow thrusters come with either single or twin propellers. Vetus brand thrusters state they have the same performance with one prop as their competitors do with two. The theory being that in order to work in perfect order, one prop must turn twice as fast as the other and in the opposite direction to gain only 3-4% more efficiency. Vetus claims this doesn't[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic26.jpg"]![[Image: bow_thrust_pic26_small.jpg]](http://www.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic26_small.jpg)
[/url] always happen and that one prop doing all the work balances out the performance gain of twin props.
[/size][/#000000][/font][font "Verdana"][#000080][size 2]Factors that lead to less than optimum performance:[/size][/#000080][/font][/left] [ul] [li][font "Verdana"][#000000][size 2]Low battery voltage[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Tunnel in bow not shaped properly[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Tunnel openings with grids over hole; grids can cause decreased performance[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Thruster unit too small for the vessel[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Hydraulic hoses not in proper condition[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Hydraulic hoses not proper length[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Low hydraulic fluid level[/size][/#000000][/font]
[/li][/ul]
[font "Impact"][#000080][size 4]That Big Hole!
[/size][/#000080][/font] [font "Verdana"][size 2][#000000]The biggest concern with most mariners beginning a job like this is the big hole that has to be in place below the waterline. Who does the installation? Not you, unless you're a certified thruster installer because obviously, this is a serious structural job. Drilling a big hole in your boats' hull below the waterline needs to be carried out by someone reputable with experience and one who can provide references from other bow thruster jobs. The manufacturer will give you suggested contact people. As recommended, a tunnel needs to be made in the hull as far forward and as deep as possible. After the tunnel is cut into the vessel, a tube or sleeve is secured inside the tunnel where the unit will be mounted. The tube material is available in fiberglass, aluminum or steel to accommodate the hull material of your trawler.[/#000000]
[#000000]The tunnel dimensions are roughly between 5" ID (internal diameter) 10" (internal diameter) ID depending on thruster of choice.
The vessel itself can suffer a bit from having an unnatural hole drilled through its bow. While underway, if water rushing past the hole is not deflected away, water will rush into the hole and cause drag and reduce speed on the vessel. Your batteries must be able to handle the load as well. A separate power supply (battery bank) for the thruster should be provided. For example, the Vetus model 5012 with 51-lbs. of thrust draws 150 amps during eight minutes of continuous use.
The price tag for these jewels are not small, convenience comes with a not so convenient cost. The units themselves range from approximately $2000 to $6500 including control panel. This price does not include installation, which can easily double with labor costs.
In some cases, price alone will determine who owns a bow thruster. We have all experienced times when we wish we had one, but somehow we always manage to get our trawler back where it came from. A bow thruster can be a very useful tool, but it is not for everybody nor is it a necessity. Many mariners have circumnavigated the globe without one and many sailors have voyaged the globe with no engine, let alone a bow thruster. If you are thinking of purchasing a thruster, call around and talk to people who have them. Get their take on this invisible man under the water. Is it worth it? It's worth it if the time is right. Using all the tools at hand to make your voyage as comfortable and pleasurable as possible is a great way to go.[/#000000][/size][/font] [indent] [indent]
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[font "Verdana"][#000080][size 5]S[/size][/#000080][/font][font "Verdana"][#000000][size 2]mooth maneuvering is easy on the open water, with one foot on the wheel and one hand on an icy drink--until... the time comes to dock with the wind in the "wrong" direction. Suddenly, you have two[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic27.jpg"]
[/url] hands on the wheel and your feet are sweating while you try to maneuver your 30,000-pound trawler in between two toothpicks with million dollar boats on either side. Some in this situation might say, "No problem, I have bow thrusters" while others might say, "holy @&%*!" If the time and money is right, bow thrusters are a worthwhile investment for any trawler owner. Here's an overview in the world of bow thrusters from some common names in the industry.[/size][/#000000][/font][/left] [left][font "Impact"][#000080][size 4]History[/size][/#000080][/font]
[font "Verdana"][size 2]I[#000000]n a crude form, bow thrusters have been around since the early 1900's. In these early years, mariners discovered the usefulness of the bow thruster to help steer in close quarters. The modern bow thruster has the same basic concept. However most New England fisherman, especially the long-liner, uses the bow thruster not for docking but for slow precision net tending in the ocean. A fishing vessel can stop dead in the water and use thrusters to move about the nets.
Some mariners will let their macho pride show when speaking of thrusters, "If you can't dock a boat without thrusters, you don't need to be on a boat". Hey, if you can financially and physically own and use a piece of equipment that makes life easier and safer...go for it! Besides, tell a tugboat captain he is not a man because he uses a bow thruster and see what kind of response you get!
Once you've decided that a bow thruster is right for you, choosing the right one can be a bit confusing. The manufacturer you choose will be more than happy to point you in the right direction, but here's a little head start. [/#000000] [/size][/font][/left] [left][font "Verdana"][size 2]
[/size][/font][font "Impact"][#000080][size 4]Things To Consider...[/size][/#000080][/font]
[font "Verdana"][#000000][size 2]The LOA (length over all) and displacement are main considerations when choosing a bow thruster. Thrusters come in two forms: electric or hydraulic. The form of propulsion is solely the buyer's discretion. It's uncertain which is more efficient, each manufacturer claims personal glory for their form of thruster. Thrust exerts horizontal outward pressure and determines the size of thruster needed, not electric motor size or hydraulic output. Thrust is usually measured in thrust per kg (kilogram). For example, Side Power (a bow and stern thruster representative) distributes a 35S model bow thruster, which has a thrust of 35 kg or 77 lbs.[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic_25.jpg"]
[/url]with a 3hp 12-volt motor. Bare in mind this thrust load is at optimum performance (i.e. perfect batteries or perfect size and length hydraulic hose without a single leak, etc.). This thruster is recommended for smaller vessels 25-32 feet. If your displacement is greater than most of this length, such as a Willard 30 full displacement trawler, you may have to step up one notch to get acceptable performance. At the other end of the scale would be Side Power's 285-TC bow thruster with a whopping 285 kg or 627 lbs. of thrust. You could turn this thruster around and use it for main propulsion! This model is for vessels up to 80 feet in length.Bow thrusters come with either single or twin propellers. Vetus brand thrusters state they have the same performance with one prop as their competitors do with two. The theory being that in order to work in perfect order, one prop must turn twice as fast as the other and in the opposite direction to gain only 3-4% more efficiency. Vetus claims this doesn't[url "http://dev.pilothouseonline.com/IS2V1_00/images/bowThrusters/bow_thrust_pic26.jpg"]
[/url] always happen and that one prop doing all the work balances out the performance gain of twin props.[/size][/#000000][/font][font "Verdana"][#000080][size 2]Factors that lead to less than optimum performance:[/size][/#000080][/font][/left] [ul] [li][font "Verdana"][#000000][size 2]Low battery voltage[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Tunnel in bow not shaped properly[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Tunnel openings with grids over hole; grids can cause decreased performance[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Thruster unit too small for the vessel[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Hydraulic hoses not in proper condition[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Hydraulic hoses not proper length[/size][/#000000][/font] [li][font "Verdana"][#000000][size 2]Low hydraulic fluid level[/size][/#000000][/font]
[/li][/ul]
[font "Impact"][#000080][size 4]That Big Hole!
[/size][/#000080][/font] [font "Verdana"][size 2][#000000]The biggest concern with most mariners beginning a job like this is the big hole that has to be in place below the waterline. Who does the installation? Not you, unless you're a certified thruster installer because obviously, this is a serious structural job. Drilling a big hole in your boats' hull below the waterline needs to be carried out by someone reputable with experience and one who can provide references from other bow thruster jobs. The manufacturer will give you suggested contact people. As recommended, a tunnel needs to be made in the hull as far forward and as deep as possible. After the tunnel is cut into the vessel, a tube or sleeve is secured inside the tunnel where the unit will be mounted. The tube material is available in fiberglass, aluminum or steel to accommodate the hull material of your trawler.[/#000000]
[#000000]The tunnel dimensions are roughly between 5" ID (internal diameter) 10" (internal diameter) ID depending on thruster of choice.
The vessel itself can suffer a bit from having an unnatural hole drilled through its bow. While underway, if water rushing past the hole is not deflected away, water will rush into the hole and cause drag and reduce speed on the vessel. Your batteries must be able to handle the load as well. A separate power supply (battery bank) for the thruster should be provided. For example, the Vetus model 5012 with 51-lbs. of thrust draws 150 amps during eight minutes of continuous use.
The price tag for these jewels are not small, convenience comes with a not so convenient cost. The units themselves range from approximately $2000 to $6500 including control panel. This price does not include installation, which can easily double with labor costs.
In some cases, price alone will determine who owns a bow thruster. We have all experienced times when we wish we had one, but somehow we always manage to get our trawler back where it came from. A bow thruster can be a very useful tool, but it is not for everybody nor is it a necessity. Many mariners have circumnavigated the globe without one and many sailors have voyaged the globe with no engine, let alone a bow thruster. If you are thinking of purchasing a thruster, call around and talk to people who have them. Get their take on this invisible man under the water. Is it worth it? It's worth it if the time is right. Using all the tools at hand to make your voyage as comfortable and pleasurable as possible is a great way to go.[/#000000][/size][/font] [indent] [indent]
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