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TOPIC: 38XX owners- what speed do you use trim tabs?

38XX owners- what speed do you use trim tabs? 21 Oct 2013 23:27 #1

  • Jim Gandee
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Another thread got me to thinking , at what speed do you begin to use your trim tabs and what improvement do you see? I have mostly cruised my Hino 175HP, 1989 3888 at around 1000 RPM which yields about 6kts or so tide dependent. I have never tried the tabs at that slow speed so maybe I'm missing something?

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Jim Gandee
1989 3888
Hino 175's
Fire Escape
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38XX owners- what speed do you use trim tabs? 22 Oct 2013 00:05 #2

  • kwb
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My tabs are almost full down 99% of the time and rarely make any adjustment.

Typical running speeds are 15-16kn.

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1989 3888
Nobody gets out alive.

38XX owners- what speed do you use trim tabs? 22 Oct 2013 01:10 #3

  • bobsyiruncle
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Thanks very much lpiex

This s worth playing around with

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3888 with Hinos

38XX owners- what speed do you use trim tabs? 22 Oct 2013 02:10 #4

  • dmcb
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I travel at these speeds also. 6 mph.
I can tell you for a fact if you lower your tabs at your speed, you will also lower your speed.
Doug

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Started boating 1955
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38XX owners- what speed do you use trim tabs? 22 Oct 2013 02:44 #5

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Doug, copy that. I wonder if anyone has experimented with higher speeds and tabs at all. I know that if I put the tabs full down prior to full throttle the boat comes out of the water and gets to top speed quicker than if I wait to lower the tabs.
What's the speed though at which the tabs begin to help? Next week I'll be moving the boat and I will test various speeds and tab use and report my findings.
FWIW my boat has tab extensions on the outter tabs.

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Jim Gandee
1989 3888
Hino 175's
Fire Escape
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38XX owners- what speed do you use trim tabs? 24 Oct 2013 00:12 #6

  • jmcannonball
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I use my tabs at any speed above "hull speed". I have 5" extensions on all 4 tabs.

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Two C's 1990 3888 MY, 175 Hinos, Hurth 630 Trannys[/B]
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Member International Order of the Blue Gavel
MMSI: 338030604

38XX owners- what speed do you use trim tabs? 24 Oct 2013 00:31 #7

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JM,
Thank you for your response. What is your definition of hull speed, 5-6 kts? Also, when you use your tabs above that speed, say 10 kts, how much deflection do you use and what effect does it have?

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Jim Gandee
1989 3888
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Fire Escape
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38XX owners- what speed do you use trim tabs? 24 Oct 2013 11:12 #8

  • dmcb
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The use of tabs varies with the sea conditions also so no setting is right for all cases. Bayliner even has a warning on my helm about not using them in following seas.
You may require full tabs at anything above hull speed. For economy running I use 6 mph on one engine and 7 mph on 2 which is a bit below hull speed.
Here is what I have done on every boat I have owned.
At the cruise speed I want to run, I slowly bump the tabs. Up and down. Be sure to give the boat time to react but watch the speed. It will change. You can't watch the tachs on a diesel because the governors will keep it the same but you can on a gasser.
When you find your max speed without moving the throttle, I feel that is your best tab position at that load, sea condition and speed.
Doug

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Started boating 1955
Number of boats owned 32
Bayliners
2655
2755
2850
3870 presently owned
Favorite boat. Toss up. 46' Chris Craft, 3870 Bayliner

38XX owners- what speed do you use trim tabs? 24 Oct 2013 11:33 #9

  • mmichellich
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Your tabs should help at all speeds. Comfort and safety dictate less tab in larger following seas.

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Started boating 1965
Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996

38XX owners- what speed do you use trim tabs? 24 Oct 2013 13:51 #10

  • Jim Gandee
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Doug,
do you recall the RPM on the one engine to make 6 kts?
About ten days from now I will be running from Anacortes to Olympia and will test the tabs at various speeds.

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Jim Gandee
1989 3888
Hino 175's
Fire Escape
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38XX owners- what speed do you use trim tabs? 25 Oct 2013 15:43 #11

  • hughver
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In the FWIW department, I've been crusing the last three years and 200+ hours at 7.1KPH/1500RPM on two engines. Since I have autopilot and have nothing else to do at this speed but watch for logs/boats/whales, I've tried all trim tab positions to see how it affects speed. At full tabs there is a noticeable reduction in speed. IMHO, at 7.1KPH the speed reduction is proportional to tab deployment. I do not keep track of fuel burn other than to know that my travels are relatively economical (around150 gallons/season).

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Hugh
1996 3988 W/ 250 Cummins
1995 Novurania 380 W/40HP Yamaha
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38XX owners- what speed do you use trim tabs? 26 Oct 2013 19:35 #12

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Thanks for the info Hugh, it's helpful. It appears that at the slower speeds 5-maybe 10 kts the use of tabs only slow the boat. Next week I'll test the tab performance at the 10-14 knot speeds and report back.

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Jim Gandee
1989 3888
Hino 175's
Fire Escape
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