modifing bennett trim tabs

[lime4x4]

Currently have a 27 foot cruiser which weighs in at 7000lbs powered by a single 350 mercruiser I/O. The boat currently has 12X12 bennett trim on. I need to get bigger tabs to help with getting the boat on plane at a slower speed.. to buy just the bigger tabs it will cost around 400 bucks. I can get a really good deal on another set of 12x12 tabs.My options are

option 1) mount the trim tabs next to my exsisting set and spilt the hydrulic line for 2 actuators
option 2) mount the trim tabs next to each other and weld the tabs together then move the actuator to the center
option 3) mount the trim tabs next to each other and weld them together then weld a bar across both tabs so i don't have to move the actuator

 

[gcboat]

Re: modifing bennett trim tabs

Don't have much of a hydraulic backround but the thought crossed my mind that the pump just might not have enough in it to make all that extra steel move, especially down. Just thinking out loud. Pretty decent idea, hope you can get it to work.

 

[erikgreen]

Re: modifing bennett trim tabs

Make yourself a custom set of the large moving plate parts and mount them on the boat. I think Bennett uses the same power unit for all sizes of tabs in a given class, so unless you double the size you should be ok....

 

[5150abf]

Re: modifing bennett trim tabs

Not a hydraulic specialist but it seems of the options given splitting the line seems the most feasible, in theory it will take twice as long for the tabs to react as you have to pump twice as much fluid.
Welding both together seems like way too much stress, you would be doubling the load the cylinder was designed for and fixxing them in place would seem to defeat the purpose of having them, they would work at one load under one set of conditions.
Also splitting the line is most reversible if it doesn't work.
thats my 2 cents.

 

[lime4x4]

Re: modifing bennett trim tabs

according to bennett they use the same pump and single actuators all the way up to 60 inch trim tabs

 

[Bondo]

Re: modifing bennett trim tabs

Ayuh,......

I like Option 1,.....
But if you have the capabilities,... I'd weld them together along the edge as Well....

Option #3, I think would tend to induce too much Twist into them.....

 

[crazy charlie]

Re: modifing bennett trim tabs

I would recommend installing a doel fin or stingray to the drive.That size boat with a single drive NEEDS an outdrive stabilizer for lift when getting on plane and will keep the boat on plane at lower speeds when you would usually be coming off plane and fighting the throttle to stay on plane.Charlie

 

[Boatist]

Re: modifing bennett trim tabs

I have bennett trim tabs of 24 by 12 on each side on a 21 foot boat and 2800 pounds dry. I will tell you that if atempting to put the tabs down while coming up on plane the pump will sometimes not have enough power to do it. You can put the tabs down before coming up on plane or after with no problem. Dual cylinders would work slower but with twice the power but I dout you have enough fluid to fill 4 cylinders and push them all the way down. I would call bennet and ask them what they suggest.

 

[marine4003]

Re: modifing bennett trim tabs

Use option #2,but when you weld the two,also weld a reinforcing bar across the two tabs to correct any deflection,preferably along the front of the tabs, the pump will handle the extra tabs,the only thing the pump DOESN'T like is not enough power,so make sure the connections to the power from pump are bussed correctly or have there own lead off battery.I use K-Planes 380-S on the Scarab,and there hooked up to the original Bennett trim pump,No problem,and these K's are big tabs.

 

[dingbat]

Re: modifing bennett trim tabs

How about option 4. Buy a new set of hinges and trims planes from Bennett for $150 and move the actuators over to the center of the tab

 

[captk]

Re: modifing bennett trim tabs

Have you checked with bennitt? They have a great customer service dept.

 

[lime4x4]

Re: modifing bennett trim tabs

the cheapest i've found for 30x9 which according to bennett belongs on this size boat was 167.00 for ONE tab and hinge plate. If they were 150 for both sets then i would've bought them

 

[Jdeagro]

Re: modifing bennett trim tabs

As a manufacturer I would recommend that you contact Bennett customer service and make sure that what you intend to do will work correctly. Also make sure that the hydraulic system is not leaking.

Do not use a hydrofoil on the out drive as it was never designed to lift the boat, that job belongs to the hull.

I think you will find Bennett very helpfull.

 

[lime4x4]

Re: modifing bennett trim tabs

tried a hydrafoil once and i quickly ripped that damn thing off.not stable at all.. I posted this question on another forum where a guy from bennett frequents and he side i can run 2 tab systems.he said bayliner did that alot.But i found a site that claims they have 30x9 tabs for 97 bucks a set so i just might go that route