Bigger Trim Tabs??

[davebuc]

Hi,
I have a 23' Glastron SSV 233, Deep V hull. 5.7L engine, Alpha 1 outdrive. 17 pitch stainless prop. No hydrofoil on outdrive.

The problem I would like to solve is that it is incredibly difficult to keep consistent speed in the 16-20mph range when driving for a wakeboarder because the boat is fighting to be on plane / falling off plane and the speed changes as this changes.

Trimming the outdrive up makes it worse, not better.

The boat has 2 Bennett trim tabs (1 each side), each measuring 9 long" x 12" wide

According to the reading I just did on Bennett's site, they suggest the width (span) of each tab to be 1" for each foot of boat, which suggests ours should be 9"long by 24" wide.

There is a lot of transom room for wider tabs.

I am trying to get a feel for whether wider tabs would help enough to be worth it, or whether a prop change is worth trying?

Thanks,
Dave

 

[dingbat]

Re: Bigger Trim Tabs??

I would first ask your builder what is the design speed of that hull. If the hull was not designed to plane at those speeds, nothing is going to help you.

 

[seabob4]

Re: Bigger Trim Tabs??

Ding,
I have to disagree with you there. Tabs can consistently reduce the speed at which a boat can stay on plane...

Dave, I'd go with wider. What you are looking for is increased stern lift, this can be done either with length or width, as you have greater surface area for the water to act upon. By going with increased width, the same actuators will work for you...

 

[Boatist]

Re: Bigger Trim Tabs??

Wider or deeper tabs will help but hull design and weight also matters. That a pretty big boat for wakeboarder.
Deep V plane at faster speeds than a flat bottom boats.
I have a 21 foot modified V hull but made of Aluminum and weighs 2800 pounds dry.
I have Bennett Trim tabs 24" width by 12" cord or depth.
My natural planing speed is 20 MPH with engine netural and tabs up. With my tabs full down I can stay on plane down to 9 mph and will clime on plane at about 11mph.

If you keep this thread alive Tabman will likely see it and help you out. I know you can go to 12 by 12 without much work and buy just the tabs them self.

Another thing is if you can reduce weight in the boat that will help some.

Hopefully TabMan will stop by and help you.

 

[Tabman]

Re: Bigger Trim Tabs??

Somehow this thread got under my radar!

Seabob is on target, adding surface area aft in the form of larger Trim Tabs will let the boat plane at lower speeds.

Dave, do you have a photo of how the Trim Tabs are mounted on your transom? That will help us determine what we might be able to fit. Boatist is right, 12 x 12 Trim Tabs can be used in place of the 12 x 9s you have now without moving anything or drilling new holes. They would help a bit, but if we could fit something along the lines of 18 x 12 that would make a much bigger difference in lowering your planing speed.