What exactly is boat trimming?

Boat trimming is the correction of hull’s cruise angle in respect of the sea surface (pitch), and also the correction of hull’s roll angle (around the longwise axis).


My boat is fine-adjusted so why do I need dynamic trim?

Even with the best designed hulls, optimal cruise line which enhancemaximum speed, maximum stability, economy in fuel and comfort, is achieved only in a specific angle (or around it) of the hull in respect of sea surface. Changing factors like, height and direction of waves, wind, distribution of load on the deck, or speed of the boat, may divert a hull from optimal geometry (angle). A dynamic trim control can continuously  re-adjust cruise line so the boat to gain back maximum speed, stability and of course economy in fuel consumption.


Which systems are there in the market for dynamic trimming?

Traditional trim tabs (or flaps) are the most common systems for boat’s dynamic trimming. Interceptors are a pair of plates attached on the transom of the boat. Electric or hydraulic actuators adjust the ascent of the plates in respect of sea level. This inclination of plates produce the appropriate lift power so the hull’s geometry to get adjusted.

Within the last 10-15 years, interceptors (or vertical flaps) a new, more efficient concept entered in the market of boat trimming based on the technology of Gurney flaps. Gurney flaps have been used several decades now in airspace industry. They are a pair of blades (also attached on the transom of boats) extending vertically in the water. Few millimeters of extension of blades can produce a power lift exactly under the stern, so boat’s pitch and roll can be dynamically trimmed.


Which are the main technical features of Hydrotabs?

Hydrotab’s design is based on the concept of vertical flaps (interceptors). The innovation about Hydrotab has to do with the simple though highly reliable and robust mechanism which never fails.  Until today, vertical flaps were complicated mechanisms vulnerable to failures due to the sensitive parts they consisted of (servomotors, gears/rotating parts, seals. etc.), demanding also high precision during their installation. In the contrary, with a simple mechanism open to the sea water, self-cleaning, made of materials unaffected by salt water or barnacles, Hydrotab practically have zero-fail rate and needs no maintenance.


I have been using trim tabs for several years, why should I change them with Hydrotabs? 

  • First of all, you should change your flaps, in case your boat does not plane immediately, or does not plane at all, which means that the selection of your current flaps is incorrect. In that case, do not hesitate to choose Hydrotabs for your application, due to their several advantages.
  • Your current conventional hydraulic flaps require to be cleaned regularly, to avoid fouling and barnacle development, which operates as a break for your boat.
  • Also, they get damaged frequently, and require spare parts and service. Very often, a small initial price hides big future costs. Malfunction will happen when you want to use the boat mostly, i.e. at your vacation period.
  • There is a common problem of steering interference, when you reverse the boat.
  • A more frequent problem is when they are extended in high wave condition, because of the high received stress, from the boat constant bouncing.
  • In smaller vessels and at inflatables also, flaps protruded and there may be an injury, since the passengers usually move to the back of the vessel. Also, they are not visually attractive.
  • Conventional flaps have many moving parts, so the possibility of damage is high.


Which are the major advantages of Hydrotabs comparing to conventional trim tabs?

Benchmarking users of classic trim tabs after they changed them with Hydrotabs, responded as follows:


Is it true that vertical flaps (interceptors) produce more drag effect (friction) than common trim tabs, due to the fact that interceptors extend vertically in the water?

No, it is not true. Several contemporary scientific studies bear testaments to the contrary. Interceptors need only few mm of vertical extension to produce the appropriate lift so to trim the boat. Friction and drag power is proportional to the flap’s surface exposed to the water, so conventional trim tabs produce much greater amount of drug. In addition, response of interceptors is quicker and more precise. These are the major reasons super-yachts builders use interceptors instead of common trim tabs.


Are Hydrotabs appropriate for planning and semi-planning motor boats?

Yes, Hydrotabs can be used to optimize cruising performance to both planning and semi-planning boats. Hydrotabs, like all interceptor systems are effective for speeds greater than 7Knots.


 Are Hydrotabs appropriate for a small and light motor boats like inflatables or RIBs?

Yes, different sizes of Hydrotab cover motor boats 20-130ft. In fact, the smaller and lighter the boat is the more the need for trim adjustment is, since small and light boats are more sensitive to weather conditions, speed or load changes.


Frequently Asked Questions for 4DHC Controller and NMEA 2000 Network


I don’t have an NMEA 2000 network can I use 4DHC?

Yes the system will make its own network as soon as you make the proper cable connections.


I don’t have NMEA 2000 GPS Unit.

4DHC has multiple GPS inputs available as a system and n2k is just one of them,


Is 4DHC Controller compatible with NMEA 0183?

You can use the older NMEA 0183 system.


I don’t have GPS Unit at all.

Use a normal passive antenna and connect to its own built in GPS system


What are the advantages of the 4DHC system compared to other systems?

4DHC was designed from the beginning as a pure NMEA 2000 system and as such it only uses the network existing cables for the system making installation a breeze. This also means that it immediately communicates with all n2k systems without headaches.

The system is truly plug and play with full auto trim and roll functions and needs no special installations for the gyros .it’s open architecture and continuous firmware upgrades which are very easily done by the end user means you have a product that will evolve after installation and not another instrument on the panel.

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