Trim Tabs On A Jet

[JEThro]

My Nordic has trim tabs on it just like a flat does. I have a few questions about them. What is the best angle to set them at? Do I want the inside edges even, higher or lower than the outside edges? They stick out about 6 inches. If they stuck out further,lets say 8 or 10 inches,would I gain anything?
http://www.***boat.com/image_center/data/521/14Tabs.JPG
http://www.***boat.com/image_center/data/521/14Tabs2.JPG

[Oldsquirt]

Maybe Cliff knows...or even Carlos :eek: :D
Have those been on your boat the whole time? I dont think I ever noticed them before.

[Moneypitt]

You corectly IDed them as "trim tabs", thats what they do, trim the boat. To "fix" them, first you should establish if they're broken, (out of adjustment), and the only way to do that is to try the boat on the water and evaluate the "trim". Once you figure out what, if anything, the trim needs, then you can start to make SMALL changes. Small means 1/16- 1/8th changes, and try it again. The only jets I've seen with tabs had bad porpusing problems prior to the tabs,, and they were installed to keep the nose down. Your boat? I have no idea, but like I say, try it and go from there..................Moneypitt

[TRG]

the only other jet i know of is jack mcclure of MPD in costa mesa...i believe that they help his boat out in the turns as his boat is used in circle boat racing, (was!) he might be the guy to talk to about these,....i also was wondering about the pro's and con's as well!

[Mandelon]

Does the boat have handling or porpoising problems now? Might be too heavy at the backend and need some tab to keep the bow down during takeoff....
Oh, great name on the transom by the way.....LOL :cool:

[AZKC]

I'm going to tabs to fix/help my porpoising, but I'm going with the electric or hydraulic adjustable style.

[flat broke]

The setup on Jack's boat that Todd was referring to was not to cure a poroisng problem, but to be able to control the ride attitude of the hull like on a flatty. In his instance they would be fully controlable cav plates. Imagine coming up on the turn pin at 80-90mph? and knowing that you're going to have stick the boat hard into the water to keep from spining the deal when you make a hard 180. Give her some down plate, wet up the hull and make your turn.
Now the tabs on Jethro's boat are there for a different, and already mentioned reason... to help cure a porpoisng problem. Take lots of measurements before you touch anything. If the boat is running well now, there might not be much value in messing with em, buuuuut, you coud always try and bring the tabs up a small amount and see if the boat frees up and runs faster. The problem is that it will more than likely start to porpoise at one speed or another. Take good notes, make small adjustments, and see what you can get out of her.
In regard to canting the tab higher/lower on the outer edge, that would depend on the shape of the bottom of the hull. If it tended to get up on the keel and then start chine walking, you could turn down the outer edges just a bit to kill the back and forth of the chine walk.
As mentioned earlier though, The key is to take good initial measurements from your known state, and then make small adjustments for each test.
Chris