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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?
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.
1989 3888
Nobody gets out alive.
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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
3888 with Hinos
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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
Last Edit: 22 Oct 2013 02:11 by dmcb.
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38XX owners- what speed do you use trim tabs? 22 Oct 2013 02:44 #5

  • Jim Gandee
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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.
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.
Two C's 1990 3888 Motoryacht w/175 Hinos
Past Commodore Emerald Rose Yacht Club
Member International Order of the Blue Gavel
MMSI: 338030604
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38XX owners- what speed do you use trim tabs? 24 Oct 2013 00:31 #7

  • Jim Gandee
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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?
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 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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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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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.
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).
Hugh
1987 3218 W/135 Hinos
"Last Call"

MMSI 367409880
Last Edit: 25 Oct 2013 22:36 by hughver.
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38XX owners- what speed do you use trim tabs? 26 Oct 2013 19:35 #12

  • Jim Gandee
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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.
Jim Gandee
1989 3888
Hino 175's
Fire Escape
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