Announcement

Collapse
No announcement yet.

2655 SUNBRIDGE TABS VS (OR IN CONJUNCTION WITH) ENG TRIM-gctid818349

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    2655 SUNBRIDGE TABS VS (OR IN CONJUNCTION WITH) ENG TRIM-gctid818349

    I'd be grateful for some clarification/ education regarding tabs and or trimming engine. My first (and only one so far to be in water) boat was a 21ft c/c with a Mariner 150 outbd. Salt and brackish my entire 4 years of boating life in it. Running the NC sounds I learned the finer points of eng trim as to speed, economy and to a point, handling. I could get her "on step" and as I ran the tab up, learned that just below cavitation was the "sweet spot" where the least surface area of the hull was touching/ causing resistance, and max top speed (per the GPS) providing the water was behaving. The nagging issue with the c/c was from around 25mph to top speed (38 and on good days 41 once I installed a 4 blade prop) and through the last several degrees of "up" trimming she had a list to STBD, although she managed to hold heading and track better than the list would make you think she would. Pronounced enough that I'd actually move my body max to port thinking my big ol self would counter..... at lower speeds it worked to a point. planed out it didn't matter where I moved and 20 mph down to idle after breaking the stern loose to kill wake it sat flat and level at a 5-8 mph( producing no wake) speed in the zones. The preceding is to date my experience and knowledge of trim. Now I've moved to a cruiser with trim able outdrive AND tabs. I am upgrading the tab system to the Bennett system with angle indicator and "auto full up" at shutdown. IF at all do the tabs work in conjunction with outdrive trimming or (as the PO stated) eng trims for raising for transport and tabs are for in the water. Should I regard them as independent systems, OR use in conjunction with each other and if so, to what point or within what range(s)?

    My job in aviation has me with a general basic understanding the fundamentals of trim, theory and operation. but realizing in the end boat doesn't really = wing and water doesn't really = air past simple comparisons and conversation. With the time till I actually get her ready to float the first time I hope to have a couple of basic scenarios and procedures committed to memory as foundation to work from and build upon

    The question I have is..... After reading talking to larger vessel operators with fixed components ( from just a few ft longer then the c/c and up to a max 30 ft and comparable displacement, config and approx. basic estimated as my 2655), weights, and distribution as well as performance when ready for a weekend on the water including eng compt component location and capacities, etc, and have begun to adapt and "train" my mind that I'll be depending on the tabs more to keep the 2655 level at any given speed depending on how I've loaded her and that, like the c/c the engine trim to adjust her "footprint, top and best speeds/econ for a run to safe port and best economy for overall traveling most of a day on a multi-day adventure. OK be gentle.....am I even close?. At some point I hope to end up with a "best scenario" for consistent loading weight/ config., a more level and stable ride within pre defined tab/ eng angles hopefully with less trial and error time getting those "ballpark" initial settings/ start here's" and more time "tweaking" within the ballpark for future adventures.

    Thanks Y'all and again apologies for the inability to just cut to the chase and loose the "fluff". My entire career's required consumption of mass quantities of "details details Kool-Aid", and too often I forget to "set the switch" to weekend mode....
    Dave
    Restoring/ upgrading: 1990 Ciera Sunbridge 2655 ST, "One Particular Harbour"
    5.7 Mercruiser Alpha 1 Gen 1 (my floating retirement villa if it doesn't kill me first)
    Sold:
    1995 SeaPro 210 C/C "Hydro-Therapy"
    Mariner 150
    Towing with:
    2002 Ford F 350 7.3L Super Duty
    Near High Rock Lake, N.C.

    #2
    Here is a little "Trim Tabs 101" I wrote a while back that you might find helpful.

    There is a section on using Tabs with power trim.

    If you are new to using Trim Tabs you may find this helpful in learning how to use them to achieve the best results. All boats react differently to Trim Tabs and the best way to find out what works best for yours is to experiment, and remember, use short bursts of the controls and let the boat settle down between corrections. Using them will soon become second nature.

    Also some boats that suffer from "wandering" at low speeds (particularly I/Os) will benefit from having the Tabs fully down at no wake speeds. They sort of act like feathers on an arrow and make steering a little easier.

    Tom McGow

    Bennett Marine

    Getting and Staying Trimmed

    All boats assume different fore to aft attitudes at different throttle settings and vary in sensitivity to lateral weight distribution.

    A boat's optimum running attitude is determined by the operator. While some people may define optimum running attitude as the highest possible speed for a given amount of engine RPMs, others desire the best possible fuel economy, yet others may be trimming the boat to get just the right mix of speed and wake (such as for waterskiing.)

    Optimum running attitude is when the boat is running to the operator's satisfaction for the given operating conditions. There are as many optimum running attitudes as there are boats and boat owners

    A good way to determine a boats optimum running angle is to run the boat lightly loaded at full speed in calm water. During this test observe the boat's bow in relation to the horizon. Most boats run at or near their optimum attitude under these conditions. This should give you a feel for the appearance of the wake and bow spray when running at an efficient attitude. Note that not all boats will achieve their optimum running attitude under these conditions. Some boats will benefit from extra lift even when running at their maximum throttle settings. If you feel the boat will benefit from added bow down trim when running at speed start with the trim tabs fully up and deflect the trim tabs in short bursts. Be alert to changes in the boats handling, as you bring the bow down. Observe any changes in RPMs and/or speed. Adjust power trim if applicable.

    Indications of Running Untrimmed

    When a boat is running untrimmed the bow spray will exit the sides of the boat far aft. The stern wave (wake) is high and curling like a breaker on the beach. The rooster tail is high and close to the stern. The engine is laboring and the ride tends to be less smooth.

    Indications of Running Trimmed

    The bow spray moves forward and is flung not as far from the boat. The wake diminishes in height, as the rooster tail flattens out and moves away from the boat. The engine is operating under less load as evidenced by the tachometer and speed as well as sounding "less strained".

    One Step at a Time

    The key to obtaining optimal results from trim tabs is to operate them in short "bursts" and let the boat react before making another adjustment. The amount of time between corrections is influenced by the size of the trim tabs and the boat's speed. This will help avoid overtrimming or ending up with one tab too far down when correcting lateral trim. You will quickly become acquainted with a boat's particular traits.

    Take Off

    Properly sized trim tabs can significantly reduce the time needed to get up on plane. They also allow a boat to keep its bow down and stay on plane at lower speeds.

    As the throttle is advanced the stern of the boat begins to squat, lifting the bow. As the boat accelerates, push the bow down position of the helm control in short bursts. The boat reacts by the stern lifting, the bow coming down, speed increasing, and reduced engine laboring. If you over do it and deflect the tabs too far the boat will end up overtrimmed. When over trimmed, the steering becomes "over sensitive" and wants to pull off course to port or starboard. If this occurs, operate the control "bow up" until the desired attitude is established.

    Getting the Most from Power Trim

    Adjust the trim tabs to achieve the desired running attitude. Then use the power trim to position the propeller thrust parallel to the water flow. If necessary, re-adjust the trim tabs to fine tune the attitude. By observing the boat's speed and engine RPMs the best combination of trim tabs and power trim will be apparent. Trim tab angle indicators and a power trim angle indicator are particularly useful in duplicating effective settings.

    Trimming to Sea Conditions

    When running into a head sea you want to trim the bow down so the sharp forward sections of the boat do their work cleaving the waves. This provides the most comfortable ride and minimizes stress on the boat (and passengers). In a following sea the tabs should be fully retracted for maximum steering response.

    Correction of a List

    The normal control setup for trim tabs operates in relation to the desired changes in trim and not the actual movement of the tabs. Therefore, do not think about what the tabs are doing, but rather on the control and what you want the boat to do. As above, make the corrections in bursts and allow the boat to settle to the new settings. You may find it easier to correct the boat's fore and aft attitude before you correct the side to side trim.

    Correction of Porpoising

    Operate the tabs in very short bursts of about half a second. Continue until porpoising subsides. The objective is to have only a very slight amount of tab deflection, just the amount needed to cure the up and down motion of the bow.
    sigpic"Like" Bennett Marine on Facebook

    Comment


      #3
      Dave, this is simply a friendly FYI and FWIW. You have mentioned several times "trim the engine". If you now own a boat equipped with a stern drive, you will be trimming the stern drive, not the engine.

      Tom has given you some great advice.

      Pay particular attention to the comments regarding engine loads.

      Correcting the hull attitude by trimming the stern drive and by using your Bennett TTs, will allow you to reduce engine loads.

      This makes for a happy Marine Engine!

      .

      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Comment


        #4
        Mr. Tabman

        I just replaced the 'green' solenoid and they both work again. Yes.

        Next problem is the size of my 2 tabs are too small for my 3288 with everything in the back now including an ONAN 5 KW. Generator, 2 sets of golf cart batteries and 2- 12 start batt.

        Existing size is 12" x 18'.

        Questions:

        How large can i extend the existing using the same actuators?

        Does it make a difference by adding for strength, if you curl up or down (more lift?) the outer edges,of the extensions?

        Would adding a slight curl at trailing edge (more lift?) create too much pressure on the actuators?

        I would appreciate your thoughts.

        Thanks,

        Don.

        Comment


          #5
          Thanks guys. I'm way ahead from where I was as I began pondering this.

          Tom, I can relate a lot pf your info to running my C/C at the coast. Transitioning from ICW to sound, seas in each and coming or going meant continual adjustment to keep her in her sweet spot but after 6 years I'd actually noticed I was doing it almost without thought. And as with my SeaPro I agree totally with the "short burst" and let her react and recover in between The more time at the helm I spent I was able to go more by range of travel as I accelerated or came off plane and both transitions became more fluid and quicker. I did, with the C/C experience wandering in the narrows where I lived. with wind and current ( sometimes both same direction....other times, well needless to say there wasn't much other than staying on the wheel that would lessen it. Your article though.... very informative. would be well advised as required reading for anyone just starting out in something with any trim feature as well as like me, some experience but moving into larger more complex boats. Getting used to this size boat and multiple systems working in conjunction towards the same end result's at least for a period of time is going to seem as I'm learning how to boat from square one again, but I welcome the process.

          Rick you're right. I learned everything I now know, I learned in the years I had the SeaPro. Huge strep up for me to the 2655. Before I sold her, I'd only been out it the SeaPro twice since moving to the mountains Jan of '15 and the 2655 hasn't left the driveway since I bought her last year in July.. Upgrades, updates, refurbishment and tending to years of little to no TLC after "fun time" ended have limited me to "driveway cruises" only LOL

          I have quite a bit to "unlearn" and start over with including terminology. The boat's going through a 26 year leap ahead in terms of systems and technology to todays standards and beyond that in craftsmanship and reliability but the process won't be complete until I "rewire" myself, catch up and get her in the water and start getting to know her which hopefully will be early spring'18 provided I'll STOP finding things I could improve upon.

          Time on the water's time well spent. and in the interim I'm becoming intimately familiar with every square inch of her as I get her ready for the big reveal and re-launch. This site and it's membership, guys like you and the wealth of info you share freely continue to motivate and inspire me on towards creating and owning one of the finest, head turning "floating retirement getaways" out there!

          Gratitude beyond measure....

          Dave
          Dave
          Restoring/ upgrading: 1990 Ciera Sunbridge 2655 ST, "One Particular Harbour"
          5.7 Mercruiser Alpha 1 Gen 1 (my floating retirement villa if it doesn't kill me first)
          Sold:
          1995 SeaPro 210 C/C "Hydro-Therapy"
          Mariner 150
          Towing with:
          2002 Ford F 350 7.3L Super Duty
          Near High Rock Lake, N.C.

          Comment


            #6
            "Belair" post=818394 wrote:
            Mr. Tabman

            I just replaced the 'green' solenoid and they both work again. Yes.

            Next problem is the size of my 2 tabs are too small for my 3288 with everything in the back now including an ONAN 5 KW. Generator, 2 sets of golf cart batteries and 2- 12 start batt.

            Existing size is 12" x 18'.

            Questions:

            How large can i extend the existing using the same actuators?

            Does it make a difference by adding for strength, if you curl up or down (more lift?) the outer edges,of the extensions?

            Would adding a slight curl at trailing edge (more lift?) create too much pressure on the actuators?

            I would appreciate your thoughts.

            Thanks,

            Don.
            Don, not sure if this helps or not but last week I bought some parts for my 1990 2655 that were removed from a 1988 2655 I can see your point. especially in a boat that has had modifications/ additions. One thing I noticed but they weren't on my list were the tabs. '88, '89 and '90 all appear to be exact in regards to hull size, design, all the "major" layout, component placement, etc. BUT the tabs..... the '88's were at least TWICE the size of my '90's tabs. There didn't appear to be any major rework or modification to the 88 (post production) though so in my best guess they would have left the assembly line in very nearly identical dimensions, configuration, weight, center of gravity (CG) and so on... and if (in theory) that's the case, why different sized tabs with that big a difference in surface area??

            Both the 88's and my '90 had the INBD and OUTBD edges "radius bent" giving a 1.5" downward leg, I assume for strengthening to prevent the tab from " flexing" from the forces and it makes sense that the down-turned edges would/ could act as fins to hold the boat in a more "true" track at higher speeds. I'm sure more surface area would equal quicker response to inputs as well as increased stability. That has me wondering would a by-product of those increases result in more stresses on the tabs and actuators, causing earlier wear limits or repair/ replacement? Or would they all fall within a predetermined "acceptable" range and simply allow dealers a wider range of marketable sellable options?

            I had hopes of locating access to original marketing. advertising/ sales brochures catalogs, etc but for my particular model/ year range, there's just not anything out there. All very interesting. Hopefully you'll get some good feedback on this one as now my interest has stirred and if bigger tabs WOULD bring big enough changes for the better, there is time left on that '88 before it goes to the scrapper that I have the option of requesting more parts. In my limited knowledge and opinion, given the displacement, size and other similar data. "curling" the trailing edge you mentioned probably wouldn't hurt anything...B UT would it and how quickly would the benefit, if any equate into a noticeable enough return on your investment in improved economy, handling, etc to offset any time/ cost having anything done to/ with the tabs you have?

            Good luck!

            Dave
            Dave
            Restoring/ upgrading: 1990 Ciera Sunbridge 2655 ST, "One Particular Harbour"
            5.7 Mercruiser Alpha 1 Gen 1 (my floating retirement villa if it doesn't kill me first)
            Sold:
            1995 SeaPro 210 C/C "Hydro-Therapy"
            Mariner 150
            Towing with:
            2002 Ford F 350 7.3L Super Duty
            Near High Rock Lake, N.C.

            Comment


              #7
              "Belair" post=818394 wrote:
              Mr. Tabman

              I just replaced the 'green' solenoid and they both work again. Yes.

              Next problem is the size of my 2 tabs are too small for my 3288 with everything in the back now including an ONAN 5 KW. Generator, 2 sets of golf cart batteries and 2- 12 start batt.

              Existing size is 12" x 18'.

              Questions:

              How large can i extend the existing using the same actuators?

              Does it make a difference by adding for strength, if you curl up or down (more lift?) the outer edges,of the extensions?

              Would adding a slight curl at trailing edge (more lift?) create too much pressure on the actuators?

              I would appreciate your thoughts.

              Thanks,

              Don.
              The largest Tab we make with a single actuator is 42" x 12" but the actuator must be in the center (side to side). We have never made a tab with a curl in the trailing edge, and I suspect getting properly sized Trim Tabs would be much more effective. We make tabs up to 72" x 12" with two actuators per Tab. The issue with a curl would be that it will always be creating lift, even when you don't want it, like in a following sea.

              You can add lift by putting 3" drop dins on either side of the Tabs. These capture water pressure that is normally lost out the sides and channels it aft to create more lift.

              Take a look at our sizing guidelines https://bennetttrimtabs.com/tab-sizi.../<br /> <br /> and you will see we recommend much larger Tabs for a boat like yours.

              Can you post pictures of your boat's transom? I may have some ideas that may be easier to implement.

              It might be best to start a new thread though so I can keep everything straight

              Tom McGow

              Bennett Marine
              sigpic"Like" Bennett Marine on Facebook

              Comment

              Working...
              X