on plane, boat weaves back and forth to both sides

jheard

Cadet
Joined
Oct 13, 2003
Messages
7
i recently purchased a 21' falcon center console, with 135 mercury ob and a 15' prop. The bottom of boat has a deep vee design in front that goes flat in the rear. the bottom is also slick with nothing but the main keel to provide straight line running stability. There is a tee top and 12"x9" trim tabs.<br />When running above 35 mph, it is a constant steering back and forth to keep it on course. it is worse in smooth water than it is in rough water.<br />I have thought about welding fins onto the trim tabs to try to get it to track better??? or would putting the motor on a jack plate help???<br />What can i do to fix this dangerous condition?<br />Please help!!!!!thx
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: on plane, boat weaves back and forth to both sides

Can you try this once without the tabs down????
 

jheard

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Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

on the the last run i had, the right tab was flat, and the left tab was down only about an inch. thats the way they are now setting on the trailer.
 

jheard

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Joined
Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

the last run on the boat, right tab was flat and the left was down only an inch or so.
 

walleyehed

Admiral
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Jun 29, 2003
Messages
6,767
Re: on plane, boat weaves back and forth to both sides

Next question: do you have Trim/tilt, and if so, where are you running the trim at speed??
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: on plane, boat weaves back and forth to both sides

I just missed another item...one tab down...one tab level. This might be creating a situation where the boat is favoring one side of the chine, and may be causing some control issues.<br /> Can you retract both tabs and run it that way?
 

Jdeagro

iboats.com Partner
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Re: on plane, boat weaves back and forth to both sides

Jheard;<br /><br />Are these tabs adjustable from the helm, or are they fixed? If they are helm adjusted ( electric or hydraulic) then they should be up on both sides when on plane and cruising. Any amount of deployment at cruising speeds will cause the boat to list or plow. Do not weld anything to the plates. <br /><br />The basic instructions for using electric or hydraulic tabs are as follows;<br /><br />When accelerating to plane the motor trim and the trim tabs should be down. <br /><br />As the boat comes onto plane bring the tabs up (both at the same time). <br /><br />Trim the motor to the most efficient prop angle.<br /><br />Adjust the trim tabs to correct the boat attitude (level the boat).<br /><br />If the seas change or you change direction, you will need to re-adjust the Trim Tabs to keep the boat level.<br /><br />If the trim tabs are fixed, and only adjusted when on the trailer then they should both be the same. Finding the correct possition for your use will require a lot of testing at various speeds, and even then it will be a comprimise.<br /><br />Under any circumtances, do not add additional planing devices or add fins to the plates.<br /><br />I suggest you call the manufacturer of the trim tabs to obtain an owners manual a read up on the correct opperation.
 

Tabman II

Petty Officer 3rd Class
Joined
Jul 12, 2002
Messages
80
Re: on plane, boat weaves back and forth to both sides

jheard,<br /><br />I am Thomas and I work for Bennett Marine in the Client Service Department.<br /><br />It sounds like you basically have a flat bottom vessel, which can have some tracking issues since they have very little in the water flow to provide directional stability (O deadrise, no lifting strakes). They can be a little "squirrelly" and tend to slide through turns, since there isn’t much more than the rudder/skag to help provide directional control. Check your trim tab system to ensure they both retract equally and when they are fully retracted they have a negative angle (above the hull's running surface), so you will be able to turn them off completely when they are not needed. Also, do you know the make of your trim tab system? If so, please let us know so we will have a better idea what we are dealing with.<br /><br />I look forward to your findings!<br /><br />Sincerely,<br />MJ Thomas<br />Bennett Marine, Inc.<br />Client Services<br />trimtabs@earthlink.net<br />www.bennetttrimtabs.com
 

jheard

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Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

THX FOR ALL THE RESPONSES ..
 

jheard

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Joined
Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

to answer all the responses, here goes, <br /><br />the motor does have tilt and trim, and it is used in a normal fashion, as the boat accellerates the trim is raised based on rpm.or when the motor "sounds right". <br /><br />the tabs are Bennett V351 system that is working well tabs go down together and at the same rate and come up together or individually. the helm control is a single joy stick( i would fell more comfortable with 2 switches) ( i have had several boats before up to 24', but this is my first boat to have trim tabs.} when they are fully retracted they are flush with the bottom of the boat, no negative angle.<br /><br />the boat has maybe 2 degree dead rise at rear max. with no lifting strakes, it smooth as a baby's butt. Squirrelly is exactly the right word, and it has no lean into the turns.<br /><br />the one tab was down as inch to keep it level in that run..i was alone in the boat, but with a heavy 60 gal. gas load(tank mid ship below console) if you run with both tabs up it list to the left.
 

jheard

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Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

tomorrow i will try to post a pic of the bottom and rear of the boat. thx
 

Tabman II

Petty Officer 3rd Class
Joined
Jul 12, 2002
Messages
80
Re: on plane, boat weaves back and forth to both sides

jheard,<br /><br />It sounds like you have a good idea how the trim tabs work, since you are already correcting for the list you experiencing. Please contact me at my email address below and provide me with your mailing address, so can send you a current Trim Tab Owner's Manual for your records at No Charge, of course! We need to check your actuators, since we have a few different ones in the field and I must know what I am dealing with before making any suggestions to help with your directional stability issue. Please provide me with the following information:<br /><br />1. How many raised rings do they have on the bottom of the 2” cylinder body, 3 or 4? <br />2. With the tabs fully retracted, how much piston shaft is exposed between the bottom of the 2” cylinder body and the Lower Hinge, 1” or none? <br />3. Do you have Trimdicators installed (http://www.bennetttrimtabs.com/trimd.htm)? <br /><br />Also, you state the trim tabs don't have any negative angle when fully retracted, but are these installed on the transom or into molded pockets? Please let me know your findings as soon as you can!<br /><br />I look forward to your reply.<br /><br />Sincerely,<br />MJ Thomas<br />Bennett Marine, Inc.<br />Client Services<br />trimtabs@earthlink.net<br />www.bennetttrimtab.com
 

Jdeagro

iboats.com Partner
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Re: on plane, boat weaves back and forth to both sides

MJ Thomas<br />Nice service!
 

Tabman II

Petty Officer 3rd Class
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Jul 12, 2002
Messages
80
Re: on plane, boat weaves back and forth to both sides

nautiJohn,<br /><br />Thank you very much for the compliment and I hope to see you at IBEX &/or Ft. Lauderdale!!!<br /><br />Sincerely,<br />MJ Thomas<br />Bennett Marine, Inc.<br />Client Services<br />trimtabs@earthlink.net<br />www.bennetttrimtabs.com
 

jheard

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Joined
Oct 13, 2003
Messages
7
Re: on plane, boat weaves back and forth to both sides

mr. Thomas, i have 4 rings on the piston, 1-3/4" is exposed on the shaft, and no trimdicators. Attached are some photos that may help you see my problem. i look forward to all the help i can get to fix the squirrelly handling. thx
 

Tabman II

Petty Officer 3rd Class
Joined
Jul 12, 2002
Messages
80
Re: on plane, boat weaves back and forth to both sides

jheard,<br /><br />Thanks for the information and photos! <br /><br />They really tell the story about your situation and I feel you are bow steering, since the trim tabs don't have the negative angle at the trailing edge the system needs. The negative angle lets you turn your trim tabs off when you don't need them, so you can run as if you didn't have any trim tabs at all. I replied back to your personal email with a more detailed explanation regarding how to correct the negative angle issue and about the extra parts that are coming in the shipment. Please wait for them to arrive before you do anything else, since the shipment will include some installation instructions to make the refit easier! Also, drop me line when it arrives and I will go over anything that doesn't make sense regarding the refit!<br /><br />I look forward to your reply.<br /><br />Sincerely,<br />MJ Thomas<br />Bennett Marine, Inc.<br />Client Services<br />trimtabs@earthlink.net<br />www.bennetttrimtabs.com
 

Jdeagro

iboats.com Partner
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Jul 30, 2003
Messages
1,682
Re: on plane, boat weaves back and forth to both sides

Thomas;<br /><br />I will stop by your booth or see me at the Greenwich trade booth. #474 on the 27 & 28th<br /><br />John
 

Tabman II

Petty Officer 3rd Class
Joined
Jul 12, 2002
Messages
80
Re: on plane, boat weaves back and forth to both sides

nautiJohn,<br /><br />Ok, I look forward to you seeing you there!<br /><br />Sincerely,<br />MJ Thomas<br />Bennett Marine, Inc.<br />Client Services<br />trimtabs@earthlink.net<br />www.bennetttrimtabs.com
 
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