TT Electric Bow Thrusters

Electronics Guru · 10-13-2009, 12:29 AM

For highly controlled manoeuvring in restricted situations Lewmar's TT ELECTRIC Thrusters represent a move forward in design and function. Easy installation and maintenance free operation are benefits that will attract both builders and owners. A comprehensive program of testing has proved that the new Lewmar Thrusters deliver efficient, balanced and supremely quiet performance.

185TT Tunnel Thrusters
185TT Tunnel Thrusters
No reservoir to install, no leaks and no maintenance High performance 5 blade propellers give equal thrust in both directions High integrity seal Spline driven propeller, no drive pin required Black box electronics prevents misuse and protects mot...

Product Description:

* No reservoir to install, no leaks and no maintenance
* High performance 5 blade propellers give equal thrust in both directions
* High integrity seal
* Spline driven propeller, no drive pin required
* Black box electronics prevents misuse and protects motor
* Hardened and ground spiral bevel gear for maximum efficiency and quiet power transmission
* Self resetting thermal protection on all motors
* Choice of Joystick or Touch Panel controls
* Easy plug together switch connections
* Minimum silhouette hub for smooth water flow

rabcoman · 10-13-2009, 12:42 AM

how $ for a boat 32' to 35

Electronics Guru · 10-14-2009, 04:40 PM

Rabco, first we need to decide on a size and there are some facts in this article to help you decide

Thruster Sizing
By definition, any thruster will to some extent do a job in any boat. The key is to ensure that the chosen thruster will do the job you want it to in your boat. This is one of two main factors deciding the right thruster size for each boat.

Today most pleasure craft over 45’ have a bow thruster as standard equipment which normally will meet the expectations of most customers when using the boat under normal weather conditions. The sizes used by the boatbuilders will vary depending on the boat’s intended usage and price level.

In today’s production boats of around 45’-50’, the typical thruster will push the boat’s bow against a direct sidewind of 20-22 knots. Some custom built or very high end boats may have a high power bow thruster that pushes the bow against a direct sidewind of 24-26 knots.

For boatowners that use their boats in more demanding conditions or have for example a strong current in their local marina, or for other reasons require very high performance, many boatbuilders offer upgrades to a more powerful thruster system. However, few pleasure crafts need a thruster that can push the bow against a direct sidewind of more than 25-27 knots. The thruster’s performance on a boat is basically determined by the boat’s wind area, the wind area distribution and the thruster’s tunnel position in the hull.

By knowing these factors we can calculate the wind pressure on the boat and the centre point of this wind pressure. From these calculations we can determine what thrust is needed to counter the wind pressure with the given thruster position. The boat weight is normally not a major factor for most pleasure craft.

Conclusion
The two main factors that decide correct thruster sizing are:
• boatowner’s performance requirements
• boat size, type and shape

HOW TO SIZE THE CORRECT BOW THRUSTER ?

A bow thruster delivers a side directional thrust force. In order to ensure the best performance under all sorts of weather and water conditions, the bow thruster should be able to provide a thrust force which is suitable, or rather: sufficient, for the boat in which it has been installed. The applied moment of the thrust force - which means to say: the position of the tunnel in the bow - is of prime importance for the bow thruster's efficiency. The further forward the bow thruster is positioned, the greater will be the efficiency. The force applied by the wind onto the boat is determined by the factors: wind speed, angle of wind attack and lateral wind draft area of the boat.
The Wind Pressure
When the wind speed increases, the wind pressure increases quadraticallly!
For wind pressure 'P', the formula reads: P = 1/2ρ× V² (lbf/sq.ft)
ρ (rho) represents the specific mass of air and 'V' stands for the
velocity of the air in ft/s.
The table below will give you an impression of wind speeds and the resulting wind pressures. It will not be possible to counter completely the adverse effect of winds of 40 knots or more. But, in such cases, the bow thruster will still "lend a strong helping hand".

The Wind-Draft of the Boat
The forces applied by the wind onto the boat can be determined by multiplying the wind pressure by the wind draft area. The wind draft area is determined by the shape and the dimensions of the superstructure. Also the wind angle is playing its part. The worst situation is created if the wind is at 90 degrees to the boat. However, due to the shape of the superstructure, which is mostly more or less streamlined, a reduction factor may be applied to the wind draft area, before calculating the wind pressure resulting from the wind speed. This reduction factor may generally be set at 0.75.

The Thrust Force
The bow thruster is required to apply a countering thrust force, which is at least equal to the thrust force applied by the wind. The required thrust force of the bow thruster may now be calculated by dividing the torque by the distance (B) between the center of the bow thruster and the pivot point of the boat.

Bow Thruster Sizing - Vessel Dimensions Bow Thruster Information
Calculation example
The boat has an overall length of 36 ft and the lateral wind draft measures 190 sq.ft. It is required that the bow can still be controlled easily when a wind force of 20 knots applies. At a wind force of 20 knots, the wind pressure is:

p = 1.0 to 1.9 lbf/sq.ft i.e.p. (average) 1.45 lbf/sq.ft.

The required torque reads:

T = windpressure x wind draft x reduction factor x distance center of effort to pivot point, (=appr. half the ship's length)

T = 1.45 lbf/sq.ft x 190 sq/ft x 0.75 x 36 ft/2 = 3719 ft.lbs.

The required Thrust Force is calculated as follows:

The bow thruster which is most suitable for this particular vessel is the 121 lbf model.

Always bear in mind that the effective performance of a bow thruster will vary with each particular boat, as the displacement, the shape of the underwater section and the positioning of the bow thruster will always be variable factor.

I'll look at a couple models and post them for you
Thanks

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10-13-2009, 12:42 AM	#2
rabcoman Got fish Join Date: Feb 2008 Location: n.y. Posts: 178 Credits: 1,727.9 Boat: 40' rabco c.c. Home Port: freeport n.y. Best Catch: offshore love Occupation: charter captain	how $ for a boat 32' to 35

10-14-2009, 04:40 PM	#3
Electronics Guru Administrator Join Date: Oct 2009 Posts: 216 Credits: 2,156.7	Rabco, first we need to decide on a size and there are some facts in this article to help you decide Thruster Sizing By definition, any thruster will to some extent do a job in any boat. The key is to ensure that the chosen thruster will do the job you want it to in your boat. This is one of two main factors deciding the right thruster size for each boat. Today most pleasure craft over 45’ have a bow thruster as standard equipment which normally will meet the expectations of most customers when using the boat under normal weather conditions. The sizes used by the boatbuilders will vary depending on the boat’s intended usage and price level. In today’s production boats of around 45’-50’, the typical thruster will push the boat’s bow against a direct sidewind of 20-22 knots. Some custom built or very high end boats may have a high power bow thruster that pushes the bow against a direct sidewind of 24-26 knots. For boatowners that use their boats in more demanding conditions or have for example a strong current in their local marina, or for other reasons require very high performance, many boatbuilders offer upgrades to a more powerful thruster system. However, few pleasure crafts need a thruster that can push the bow against a direct sidewind of more than 25-27 knots. The thruster’s performance on a boat is basically determined by the boat’s wind area, the wind area distribution and the thruster’s tunnel position in the hull. By knowing these factors we can calculate the wind pressure on the boat and the centre point of this wind pressure. From these calculations we can determine what thrust is needed to counter the wind pressure with the given thruster position. The boat weight is normally not a major factor for most pleasure craft. Conclusion The two main factors that decide correct thruster sizing are: • boatowner’s performance requirements • boat size, type and shape HOW TO SIZE THE CORRECT BOW THRUSTER ? A bow thruster delivers a side directional thrust force. In order to ensure the best performance under all sorts of weather and water conditions, the bow thruster should be able to provide a thrust force which is suitable, or rather: sufficient, for the boat in which it has been installed. The applied moment of the thrust force - which means to say: the position of the tunnel in the bow - is of prime importance for the bow thruster's efficiency. The further forward the bow thruster is positioned, the greater will be the efficiency. The force applied by the wind onto the boat is determined by the factors: wind speed, angle of wind attack and lateral wind draft area of the boat. The Wind Pressure When the wind speed increases, the wind pressure increases quadraticallly! For wind pressure 'P', the formula reads: P = 1/2ρ× V² (lbf/sq.ft) ρ (rho) represents the specific mass of air and 'V' stands for the velocity of the air in ft/s. The table below will give you an impression of wind speeds and the resulting wind pressures. It will not be possible to counter completely the adverse effect of winds of 40 knots or more. But, in such cases, the bow thruster will still "lend a strong helping hand". The Wind-Draft of the Boat The forces applied by the wind onto the boat can be determined by multiplying the wind pressure by the wind draft area. The wind draft area is determined by the shape and the dimensions of the superstructure. Also the wind angle is playing its part. The worst situation is created if the wind is at 90 degrees to the boat. However, due to the shape of the superstructure, which is mostly more or less streamlined, a reduction factor may be applied to the wind draft area, before calculating the wind pressure resulting from the wind speed. This reduction factor may generally be set at 0.75. The Thrust Force The bow thruster is required to apply a countering thrust force, which is at least equal to the thrust force applied by the wind. The required thrust force of the bow thruster may now be calculated by dividing the torque by the distance (B) between the center of the bow thruster and the pivot point of the boat. Bow Thruster Sizing - Vessel Dimensions Bow Thruster Information Calculation example The boat has an overall length of 36 ft and the lateral wind draft measures 190 sq.ft. It is required that the bow can still be controlled easily when a wind force of 20 knots applies. At a wind force of 20 knots, the wind pressure is: p = 1.0 to 1.9 lbf/sq.ft i.e.p. (average) 1.45 lbf/sq.ft. The required torque reads: T = windpressure x wind draft x reduction factor x distance center of effort to pivot point, (=appr. half the ship's length) T = 1.45 lbf/sq.ft x 190 sq/ft x 0.75 x 36 ft/2 = 3719 ft.lbs. The required Thrust Force is calculated as follows: The bow thruster which is most suitable for this particular vessel is the 121 lbf model. Always bear in mind that the effective performance of a bow thruster will vary with each particular boat, as the displacement, the shape of the underwater section and the positioning of the bow thruster will always be variable factor. I'll look at a couple models and post them for you Thanks