See full version: Understanding Ship and Boat Trim (Stability; Trim - Part 2)
This article should benefit anyone involved with designing or operating any type of floating vessel. Regulatory agents and classification society employees also need to understand these methods in order to check various designs for compliance. This article is also designed to give a good theoretical understanding of the calculative methodology utilized in the trim and stability sheets sold on this site. here
There are basically only two types of trimming calculations. Other trimming calculations are just variations of these two fundamental types. In Case I you know the vessel's weight and center of gravity (CG) location and you seek to find the forward and after drafts. In Case II you know the forward and after drafts and desire to know the vessel's weight and center of gravity (CG) location. The simple approach that is presented here should be readily understandable by anyone with a basic understanding of algebra and geometry. [links]
The vessel's "Curves of Form" are needed to perform these calculations. No attempt is made to describe the theory behind or how to construct the "Curves of Form." This article is only concerned with application of "Curves of Form" data.
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I mentioned that trim tabs have little effect in the yaw axis , but they do have some. IÂ’m sure you can readily understand that if you have only one of the tabs hanging out, besides lifting that side of the boat it will also cause a certain amount of drag . This will have the effect of slowing that side of the boat causing the bow to rotate about the yaw axis and turning the boat to that side. The rudder or out-drive are usually adjusted slightly to compensate.
Trim tabs have little effect on the yaw axis, because yaw is controlled by the rudder or the side to side movement of the outdrive. Where they are effective is in the roll axis, to eliminate or reduce listing or heeling, especially if your boat has a deep “V” hull, and in the pitch axis, to raise or lower your bow. more
The port and starboard trim tabs act independently. It is a simple thing to adjust them to lift the down side of the boat and compensate for the three or four hundred kilos of weight caused by your passengers all wanting to be on the same side. To do this, lower the down side tab. The water pressing against the tab as you move will lift that side of the boat (around the roll axis ) and eliminate your list. As your passengers move about, you can continue to adjust the tabs to compensate for the redistribution of weight. You must understand though, the trim tabs will have less effect at slower speed than at high speed. You can understand this by a simple experiment. Next time you are in your car put your hand out of the window at an angle to the slipstream. Note that when you drive slowly, the wind has little effect on your hand but as you speed up, the wind will eventually drive your hand up and back. Now remember, water is much more dense than air so prudence in applying trim is recommended. here
Where most operators initially use trim is in the pitch axis , getting their boats to the plane mode as quickly as possible. It is then easy to maintain the boatÂ’s most economical cruising speed by tab adjustment. This is accomplished using the ” Bow Down ” control. This lowers both tabs and the force of the water against them will push the stern up consequently lowering the bow (around the pitch axis ). Again, smooth rather than aggressive application is recommended to prevent pitch down of the bow. Trim may also be used in the pitch axis to keep the bow up to avoid taking seas over the bow if the water is rough. Naturally you would use the “Bow Up” control to do this.
Trim tabs work exactly the same way as the control surfaces on an airplane. As you know, there are three axes affecting the motion of your boat as you travel through the water: Yaw , Pitc h and Roll .
Using trim tabs is much like riding a bicycle. You learn to do it by feel. Your knot meter will tell you when you have trimmed for best speed at any throttle setting and your common sense will help you adjust trim to sea conditions and weight distribution. I am positive that in gaining experience you will soon amaze your friends with your skills in boat handling and trim.
While it isn't our intention to get into installation and "how it works" issues, these are worked out by the manufacturers for the different equipment. For example, the Hot Foot replaces the hand throttle cable. You install the Hot Foot pedal below the helm, then run a new throttle cable to the engine following the existing hand throttle cable route. At the engine, you disconnect the hand throttle cable and secure it out of the way. (You can remove or leave the cable and the hand throttle itself in place should you ever want to use it again.) Then you connect the cable to the engine and adjust per the directions.
Proper boat trim and planing efficiency go hand in hand. Achieving static (nonmoving) trim can be as simple as balancing your boat by distributing weight (e.g., passengers, coolers, portable fuel tanks) to keep the hull floating level. here
Once you establish a fuel consumption baseline for your boat under normal operation, conditions that can decrease fuel efficiency (such as a bent prop, fouled bottom, or clogged fuel injector) become more readily apparent. This allows you to correct problems before they worsen while saving fuel that would otherwise have been wasted prior to discovery.
The Hydrophase Ridesteady offers GPS-regulated cruise control.
Many small boats have tiller steer outboards instead of a steering wheel—this short video shows us the basics of how to use them.
Many people shy away from owning a tiller steer outboard, because we’re all used to operating vehicles with steering wheels. But truth be told, tiller steering an outboard powered boat gets you excellent maneuverability and control—in many cases even better than that of a steering wheel—and can also help shave some cost off of a new boat’s price tag since you don’t have to pay for a steering system and all the associated pieces and parts. If you’re considering getting a tiller steered outboard boat but have never owned one before, this short Boating Tips video will help. In it, we’ll cover the basics of operating a tiller steer as demonstrated on a 16’ crabbing skiff powered by a Suzuki DF25A EFI.
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The ability to quickly and effortlessly push the tiller handle in either direction provides handling and maneuverability that can’t be beat.