Storage of the spare propeller
Storage of the spare propeller
Twin 600hp Verados Versus Triple 400R Verados
Twin 600hp Verados Versus Triple 400R Verados

Testing Hydrotab's new composite 300SR trim tabs in combination with the new Moby automatic controller

By Thomas P.

As we have already mentioned in our related articles, the use of trim tabs is of great importance on each Rib.
With the help of trim tabs we can improve the planning time, stay on plane at lower rpm, achieve the best ride attitude every time according to our loads or speed and therefore maximize our ride quality.

After many tests done since now, we are concluding that is more efficient to trim a boat using trim tabs than the power trim of our engine, which is better to be used only in order to trim our propeller having to run almost parallel to the sea surface so that much of its thrust won’t be lost in the air (trimming the engine out excessively) or not to strain the transom and at the same time to raise the slip numbers in our attempt to lower the bow (trimming the engine excessively in).

So let your propeller run parallel to the water surface getting the most out of it and use the trim tabs to adjust your boat's ride attitude.

Having a very good experience of Hydrotab’s vertical trim tabs from previous tests on different boats, without a second thought we proceeded to the installation of the new composite 300SR series with the new Moby automatic controller on the Rib of the mission "RIBBING FOR ARCTIC", the Seafighter Y36, knowing in advance that they are absolutely necessary due to the large amounts of fuel that we will carry on the stern of the boat.
Note that the Seafighter Y36 is one of the most well-designed inflatable boats running on an excellent hull.
We also know that in our expedition to the Arctic Circle due to our excessive loads, the center of gravity of the Rib has shifted dramatically backwards.

Let's see, in practice, the differences arising on measurements and performance of our vessel after prolonged testing of the new composite 300SR vertical trim tabs of Hydrotab.

Getting on plane with the 300SR trim tabs activation

The Rib was standing on plane at slower speed, keeping its bow clearly lower without even increasing fuel consumption significantly.
Lowering the trim tabs by 50%, we measured 3 seconds less time of planning with the minimum raise of the bow on starting.

Then we focused on our recordings in low cruise speeds with which we will usually travel most hours of the day.
Keeping the engine trim constant at 40%, we started experimenting with the position of the vertical 300SR trim tabs. It was obvious that when the trim tabs were completely pulled up, the bow insisted on standing very high and in no case could we have a decent cruise in the area of 15 to 25 knots.
In contrast, by lowering the trim tabs by 50-70%, the behavior of the Rib changed completely. The bow was lowering considerably, the hull began to cut the water from its bow section and our cruising became softer while at the same time we ensured a very good cruising angle.
We were surprised when we found out that while traveling at 23 knots, our speed increased by 2 knots when we lowered the trim tabs by 50%, without even increasing fuel consumption, which leads to greater autonomy.
It was obvious that we have in our hands a great tool that will enable us to travel comfortably at low speeds, improving the fuel consumption and ride quality, elements that are extremely important especially in bad weather conditions.

Riding in different wave directions

The cruising improvement in each ripple direction was remarkable:

  • traveling against the waves was enough to adjust the trim tabs lower and the bow was getting down immediately allowing thus the hull to cut the water with its front part where the V is more intense offering us a more comfortable trip with softer damping.
  • steering quartering into waves, by lowering more one of the two trim tabs we could lower the leeward side of the bow and prevent its abrupt shaking upwards when it was slamming each wave making our cruising more stable and softer.
  • riding having the waves parallel to our hull activated the leeward trim tab and thus the boat-listing from the waves immediately corrected.

Testing the automatic adjustment of the trim tabs via the Moby controller

After many tests we did adjusting manually the trim tabs, it was time to automatically adjust them according to the prevailing weather conditions, with a combined automatic trimming correction and incline stabilization without any involvement from the driver, which certainly sounds impressive.

First we set up the Moby so that it recognizes the flat position of the boat along the transverse axis. Then, after checking the most efficient position of the trim tabs depending on our speed, we installed the corresponding information and selected the Full Auto position of the Moby controller, a very simple and fast process that took less than ten minutes.

Maintaining a cruise speed between 15 to 25 knots we were watching the Moby screen. We were really impressed by the immediate and combined automatic activation of the trim tabs which were going up and down depending on the speed and the Rib-listing, bringing the Rib onto the right fore and aft or lateral angle improving thus the overall performance.
It’s a particularly important application, in which the trim tabs work automatically by controlling the bow or the boat-listing to one side or the other, thus allowing the captain to concentrate on the steering wheel of the boat or relax enjoying the magic of the trip.

Summing up our conclusions from the combined use of the 300SR and the Moby controller

  • get the Rib on plane easier and faster due to the additional stern lift they are providing
  • keep the Rib on plane at lower speeds which is very important when traveling in rough seas
  • improve the ride attitude offering complete control of the bow
  • improve the handling of the boat giving a more stable and softer cruising in wavy conditions
  • increase cruising speed resulting in lower fuel consumption and greater autonomy
  • by activating the 300SR trim tabs separately and preferably, we can control and correct the boat-listing either when the weather conditions demand it or when our loads or crew are more to one side of the boat and make it tilt during cruising.
  • by selecting the automatic activation of the trim tabs, something that will be highly appreciated by the less experienced drivers, the boat maintains the right angles without the slightest involvement of the captain
  • the new Moby automatic controller is very easy to use, with a large color screen and joystick function, while with IP68 waterproofing it is perfectly suitable for open boats.

So if we accept that one of the "secrets" for the best performance of any planning vessel is to maintain the right balance and its proper angle in relation to the sea surface in any condition and throughout the engine speed range, and given that the weight distribution is constantly changing while all the weights lay from the console and back, then we are very easily led to the conclusion that the use of trim tabs is absolutely necessary in every boat.

...keep Ribbing!

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