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Old 03-04-2016, 08:48 PM   #41
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On my Krogen trawler there is no change at all from slow idle to on the pins. I can drop the stern a bit if I take off from a standstill at full throttle, thats about as low as the stern gets. My sporty, being a planing hull benifits drastically from big by large trim tabs, but then again, its not a trawler or pretending to be.
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Old 03-04-2016, 08:54 PM   #42
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If it needs trim tabs, or if trim tabs help, it is not a trawler.
I guess I am not looking at a "trawler" tomorrow. I am looking at a 43' fiberglass boat with a Diesel engine, a way to steer it, a couple cabins and some nice comforts and conveniences.
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Old 03-05-2016, 06:50 AM   #43
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"I guess I am not looking at a "trawler" tomorrow."

Trawler is an advertising term , remember "HI FI"?

About as meaningless.

Cruiser , or for 1 in 200 Offshore Cruiser might work.
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Old 03-05-2016, 11:51 PM   #44
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quick follow up

The owner of the boat showed me around today. I asked him about the trim tabs. He said that he had paid to have them added, and that he always uses them to try and optimize performance (after all, he did pay for them) but that he has yet to be able to notice any significant improvement.
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Old 03-06-2016, 07:57 AM   #45
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The owner of the boat showed me around today. I asked him about the trim tabs. He said that he had paid to have them added, and that he always uses them to try and optimize performance (after all, he did pay for them) but that he has yet to be able to notice any significant improvement.
One problem with after market trim tabs is they (owner, dealer, installer) sometimes installs tabs that are too small or not enough of them.

If you calculate the wrong speed(s) for effectiveness...then that's exactly what you get performance wise..

I saw an installer putting a pair of tiny (I'm now guessing 12x36 inches) tabs on a 50 something older Hatteras. They probably had some effect up over 15 knots...but the owner never operated up there except for rare occasions and sea trials. To be effective down in his 12 knot and below cruising speed...without knowing all the numbers and recommended size tables....and comparing to other boats I have seen...I would have guessed almost 2X the tab size or 4 tabs of at least that size. I asked when they were being installed and was told they would be fine...they weren't.
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Old 03-06-2016, 09:03 AM   #46
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If trim tabs don't offer enough lift to be a benefit then they are just drag.
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Old 03-06-2016, 09:24 AM   #47
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If trim tabs don't offer enough lift to be a benefit then they are just drag.
Only if you leave them in the down position.
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Old 03-06-2016, 10:43 AM   #48
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Boats and especially Trawlers do not need trim tabs. All real boats will float and move through the water just fine without them.

What properly sized and installed trim tabs will do is enhance performance and provide a flexibility that is not possible without trim tabs. Boats are designed to run at a specific running angle and on an even keel. The dynamic environment boats operate in involve varying wind and wave conditions. The boats themselves have ever changing load conditions as people move about, fuel comes aboard and is burned, tenders load on davits, ice melts, and very large fish come aboard. Trim tabs can allow a vessel to maintain an even keel and efficient running angle in spite of all these variables.

Tab sizing is important. The faster you go a smaller tab is needed to be effective. The reverse is also true, the slower you go the larger the tab is necessary.

Not all boats will benefit from trim tabs. Some boats have so much weight aft that no size tab will help. Some like boats with canoe sterns will be very difficult to fit tabs, some boats don't have enough useable transom to accommodate an appropriate size tab, some are too slow and too small for tabs to work.

A great many boats, even many full displacement trawlers can benefit from trim tabs. On my own Down East hulled Mainship 34 w single 200HP I could only plane with light fuel, clean bottom and downhill with a tail wind. Install 12 x 42 tabs and she doesn't leap onto plane, but lumbers up just fine to 15 knots under most load and normal bottom conditions. At 8 knots a little tab helps he find her "sweet spot" with just a little bow up attitude to keep the forefoot from "wandering."

Trim Tabs are not for everybody, or every boat, but they do what they are designed to do for a great many boats and are one of the few accessories you can buy for your boat that can pay for themselves with fuel savings.

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Old 03-06-2016, 10:54 AM   #49
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Thank you Keysdisease!
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Old 03-06-2016, 11:53 AM   #50
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On many boats, trim tabs are a necessity. On others they are a relatively simple and inexpensive means (Note I said relatively) of resolving or helping with a lot of issues. That issue might be tendency for bow to bury itself under certain conditions or for a high performance boat to porpoise. It might be weight distribution issues when tanks are full or when empty or when the number of people aboard is high or low or people are located more to one side or another. It might be wind conditions and whether heading into the wind or having it from behind. They're simple systems there to use when needed and ignore when not needed. On a performance boat capable of 60 knots, they likely will make a difference of a couple hundred RPM and up to 5 knots at WOT. On a full displacement boat it may be barely discernible. However, even if it's 100 RPM and .2 knots, that's 3% on a 6 knot boat. If a boat already has them, I don't see any reason to remove them.
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Old 03-06-2016, 12:15 PM   #51
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Originally Posted by Keysdisease;

The boats themselves have ever changing load conditions as people move about, fuel comes aboard and is burned, tenders load on davits, ice melts, and very large fish come aboard.
And sometimes people just expect too much out of tabs.
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