Trim tabs on a displacement boat.

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TomW1
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Trim tabs on a displacement boat.

Post by TomW1 » Thu Apr 12, 2018 1:13 pm

Would trim tabs work on a displacement boat with top speed of 7 mph.

Tom


Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

silentneko
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Re: Trim tabs on a displacement boat.

Post by silentneko » Thu Apr 12, 2018 2:16 pm

Well I can tell you they don't do much for a typical center console when it's going slow and off plane. So I would say 7mph isn't fast enough to get any real effect out of them.

Is the boat to light in the nose?
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TomW1
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Re: Trim tabs on a displacement boat.

Post by TomW1 » Thu Apr 12, 2018 2:38 pm

That is a possibility. I was thinking to much weight in the stern, but definitely to light in the nose could also be the problem.

Thanks for your thoughts.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

silentneko
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Re: Trim tabs on a displacement boat.

Post by silentneko » Thu Apr 12, 2018 3:22 pm

Quick way to find out. Lay some wet towels on the front deck, for protection and skid resistance, and fill some 5 gallon bucks with water up there. If things get better then you know.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

fallguy1000
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Re: Trim tabs on a displacement boat.

Post by fallguy1000 » Thu Apr 12, 2018 6:15 pm

silentneko wrote:
Thu Apr 12, 2018 3:22 pm
Quick way to find out. Lay some wet towels on the front deck, for protection and skid resistance, and fill some 5 gallon bucks with water up there. If things get better then you know.
Sorry, but no, this will change the trim abgle with undesirable results.

This also increases the section and will not help the trim tab do anything positive.

As to whether it will help; I want to know, but so far have one experienced naysayer. He says it’ll only add drag.
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viewtopic.php?f=12&t=62495

silentneko
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Re: Trim tabs on a displacement boat.

Post by silentneko » Thu Apr 12, 2018 6:56 pm

Fallguy, are you saying no to testing better balance on the boat, or the trim tabs in general? If the boat is stern heavy then the trim angle is already off. I agree with the tabs just adding drag.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

fallguy1000
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Re: Trim tabs on a displacement boat.

Post by fallguy1000 » Thu Apr 12, 2018 7:35 pm

The boat cannot go faster and efficiency of power usage will drop with water on the fordeck, or water in ballast tanks. Performance will not improve with a greater section of hull in the water. An exception would be IF the hull shape is significantly different for to aft, but it would require a bizarre shape, so really not relevant.
My boat build is here -------->

viewtopic.php?f=12&t=62495

Capt UB
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Re: Trim tabs on a displacement boat.

Post by Capt UB » Fri Apr 13, 2018 2:50 pm

On one of my old 13ft. Low Side Gheenoes with a 5 hp 4 stroke, I installed these Self Leveling Tabs from Bennett. The 13 ft. Gheenoes have a wide transom. Worked fine with one person in the boat. I would not use this type again. Would plow the boat with two people. I did go much faster with them. Better to adjust the weight in the boat... 13 ft.long, 30" wide?

SLT6 6″ x 8″ Tabs (Recommended for boats up to 17′)
(Instantly improve your smaller boat’s performance with stand-alone, spring-loaded self-leveling tabs (no control, pump, wiring or tubing required).)

TomW1
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Re: Trim tabs on a displacement boat.

Post by TomW1 » Fri Apr 13, 2018 3:34 pm

fallguy the boat will be more efficient if we can level it out. Adding maybe 500lbs of ballast to the bow may be enough. Lets try it. You can do it dock side. The extra weight is meaning less to speed as the boat weighs so much. Even adding a 1000 lbs would slow it by nothing. We need to get that boat up on her proper lines. A longer waterline carrying that weight is more efficient than a shorter one with the stern down. Speed may even go up.

Let's try to get her floating level. Can the batteries be moved forward? Can we move any other weight forward? What about the console? I'm just throwing out ideas. You know the boat. But definitely try the water on the bow :!:

If you want to discuss the technical details of this pm me. Four inches down at the stern is not right we have to get rid of it. :!: :!: It is causing drag that is slowing it down. :!:

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

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icelikkilinc
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Re: Trim tabs on a displacement boat.

Post by icelikkilinc » Mon Apr 16, 2018 5:50 am

Cumhur put tabs on Tw28

viewtopic.php?f=12&t=30297&hilit=cumhur&start=20

and video of Tw28 with tabs on 10+ knots and pulling his tender with people at the same time

https://www.youtube.com/watch?v=DMsgE-cTLEs
Ilker

TW28 launch: viewtopic.php?f=12&t=23369

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