Trim Tab Info./Critique

[cbadmin]

From: 2nd Byte (Original Message) Sent: 4/3/2003 8:57 AM
There is an interesting article on trim tabs in the current issue of "Trailer Boats".

They compare the electic (Lenco) and the hydraulic (Bennett) and the virtues of the electic and hydraulic. More important, they give the scoop on trim tab performance.

The advantages of the trim tabs are really significant, from 1000 rpm thru 5000 rpm on their test boat. Up to a 3.4 mph gain with the tabs. I was surprised to see the gain was as significant as it was in the lower rpm ranges.

For anyone contemplating trim tabs or interested in their effectiveness this article is worth looking at.

Mark

From: 2nd Byte Sent: 4/3/2003 9:06 AM
I might add that I picked this information up from by trip to the local library where I perused a copy of "Trailer Boats".
In the article they had a table showing the performance improvements throughout the rpm ranges. I just looked at the trailerboats.com site and they have the article on line with pretty complete text but the performance table is missing. I'll try to get back over, make a copy and post it.

Mark

From: C-LionRay Sent: 4/3/2003 2:20 PM
Thanks Mark


From: Mike Sent: 4/3/2003 8:29 PM
Thanks, Mark -

I read the article on the net. It took me a minute to track it down, so I copied the link to it for us.

The performance data would be interesting. Not that it would affect my view of the wisdom in tabs for the 22 CD. I am sold on 'em, but it might help convince a few others of the good they can do (like Mrs. B~C!).

It is worth noting that the article states the Bennett M120 tabs are 12" x 12", when they are actually 10" x 12" (hence the 120, as in square inches). The M120 is also one of the Sport Tab models, with the lip on the edges of the outer width. I am wondering if the performance comparison was based on two different size tabs. Was there a noticeable difference in any of the performance parameters reflected in the published table?

The author also mentions the use of trim indicators and auto-retract options. In my view, trim indicators are not necessary on the CD 22; the hull is very responsive to tab adjustment, and you can tell by looking over the bow where the tabs are set when cruising. The auto-retract option, however, is worth considering. My understanding is that the system will fully retract the tabs when the ignition is switched off, and also allow you to retract the tabs by momentarily pushing a single button. There is no problem launching or retrieving the CD 22 with the tabs left down (they won't hit the launch ramp), but if you have the tabs down when making a quick hole shot, the boat can get a little squirelly. I can tell by the sound of the pump when the tabs are fully retracted, and hold the buttons in until they are. But, sometimes I forget to do it before docking or anchoring. The indicators will tell you if they are down, or the auto-retractors will bring them up for you when you shut the motor off. If I had Dusty's money, I would have the auto-retract first, and the indicators as a luxury. Of course, without the deep pockets, I have neither.

Thanks again for getting the info.

Mike

From: Sundown Sent: 5/8/2003 7:52 AM
I am finally ready to buy trim tabs and have a couple of questions. Has anyone installed tabs that are 12" wide (port to starboard) and 9" long (bow to stern)? Does this setup work ok? Has anyone tried the electric trim tabs like those made by Lenco? Any thoughts about how they might work?
Thanks.
Larry

From: Redƒox Sent: 5/8/2003 10:05 AM
Larry mine are 12 wide and 16 long! I had to install them a little farther out to the sides than recommended though, but no regrets or problems either. If I remember right, you have the Classic like mine right? I have photo's posted of them on this site I think. It was quite the job having to make cutouts for the dual drains in the cockpit. If your C-D only has a center one, that will make it MUCH easier to install.
As for me I would pass on the auto retract feature. I like mine totally extended for getting ashore of messing about in the shallows to protect the transom from making contact with rocks. It helps!

Don't know about the electric ones.

From: Sundown Sent: 5/8/2003 2:17 PM
Greg,
I have reviewed your pictures and I do have dual drains. I really don't think I need tabs as big as yours. I am usually light (sometimes with "Lite" on board) and think maybe the smaller ones won't be so sensitive while still doing what I need.

From: Redƒox Sent: 5/10/2003 9:27 AM
True Larry but mine are dual piston and use the same pump as the single piston ones. They take twice as long to react. I actuall am stern heavy all the time anyway, it helps.

From: Mike Sent: 5/10/2003 2:16 PM
Y'all can stop fretting about how sensitive the hydraulic tabs are. After just the short time I have used them, I have it pretty much figured out how long to push each of the two buttons to get the result needed. It isn't that the tabs react too quickly, it is that the boat takes a second or two longer to react to the tabs. That is why it is easy to over adjust the tabs. The only trick is to be light on the buttons and give the hull time to respond. It becomes second nature real soon. If anything, I would now prefer the tabs to move more quickly in response to the switches, rather than slower, since I have a pretty good feel for how much movement is needed on each side, and how long to hold the switch to attain it.

The only surprises come the first few time you run with the trim tabs in use.

Any of that make sense?

Mike

From: Redƒox Sent: 5/13/2003 8:02 AM
The faster your speed the less lag time there is, if any! most the time my speed is moderate enough to utilize a faster response anyway. The dual pistons are made for the speed boats, and therefore are less sensitive. arg

From: 2nd Byte Sent: 5/13/2003 2:08 PM
Ok folks , I finally I ran down the test results that went with Trailer Boats's article on trim tabs. Obviously, we'll be looking at apples and oranges relative to our particular applications, but so be it. At least it may provide a "irrevelant" insight and I found it interesting.

In the test theyused M120 Bennett Tabs (they refer to them as 12"X12" but the M120's are 10"x12".

engine (mph) (mph)
RPM w/tabs w/o tabs

1000 4.9 3.1
1500 6,8 4.8
2000 8.0 5.5
2500 9.5 7.0
3000 12.9 10.1
3500 19.4 16.2
4000 24.7 21.4
4500 29.1 26.1
5000 31.8 29.0
5200 32.4 N/A

0 to 30 acceleration w/tabs 10.l seconds.

Boat specs: L/20'2", Beam/8', 1900#, 19 degree deadrise, 12' draft. 1999 Johnson 115 hp 2 stroke w/15x17 3 blade alum. prop

Both tests took place within an hour or one another with the same amount of gear, people & 50 gals. gas.

Mark aka: 2nd Byte

From: 2nd Byte Sent: 5/13/2003 2:12 PM
I actually had the test results spaced out so it was a little clearer to read but it bunched the figures upon sending this epistle. Sorry about that but its still good enough for government work!

Mark