Lenco Trim Tabs

M

Mighty Bite

New member
There has been some conversation about the Lenco 9x12 tabs not having the efficiency of the 9x12 Bennett or Trimmasters. I concur with this, after having Trimmasters on 2nd Byte and Lencos on my current 22' CD, 3rd Byte.

I had a senior moment, yeah , another one, and came up with a possible solution that I would like to get some opinions on. The Lenco 9x12's taper from 9" to 7" at the tail of the tab. Thus instead of having 108 sq inches of tab surface that a full 9x12 tab would have, the Lenco's have only 96 sq in with the smallest dimension being at the tail of the tab (which would normally be the point of greatest influence. A loss of 12 sq inches.

The 9x12 Lenco tabs have approximately a 7/8", 90 degree, turned up lip on the lateral edges as well as the rear of the fin. Why not detach the actuator piston from the trim tab and remove the hinge pin tying the tab to the mounting bracket on the boat. Take the tab to a metal shop and have them change the 90 degree upturn on the lateral edges to a modest downturn. By doing that you would pick up more than the 12 sq inches lost in the taper, plus the downturn on the edges would tend to hold the water flow under the tabs, allowing a bit more lift.

Another alternative would be to simply flip the tabs over placing the 90 degree lip facing down and that would make it a much easier job to bend the tabs from a 90 degree angle to a modest, say, 20 degrees. The lip on the rear of the tab could either be straightened out to conform to the surface of the tab, simply removed, or left alone. I don't know if there would be a drag factor involved in leaving it or not. In this second scenario, I'm not sure if the hinge surfaces of the mounting plate and the tab would properly align, although it appears that they would.

Anyway, if it was doable, the result would be a gain of 18 to 20 sq inches of actual tab surface over the existing tapered Lenco 9x12 tabs, or approximately 115 sq inches to 95 sq inches.

Any thoughts would be appreciated. Gotta run, I think I'm getting another senior moment.
 
Mark-

You've got some good ideas thee to choose from! Here are my thoughts on the subject:

You're right in that part of the Lenco problem would seem to be the amount and location of the surface area as well as the trailing and side edge design. Another major consideration is simply the lack of enough range of movement or vertical throw because of the limits of the specific screw jack design on the Lencos.

Re-bending the existing tabs whether you turn them over or not may run into problems of the metal having been work hardened in the original fabrication. Taking a 90 degree bend out of them and/or reversing it may be more than can be done reasonably. It depends on the specific alloy and how they were formed.

I would think it would be a lot easier to simply make a new plate to rivet onto the bottom of the existing plate. This is a much easier operation and can easily reversed by drilling out the rivets if necessary. The attachment point for the actuator arm would not have to be reversed either. The new plate could be made larger than the old one as well in the process.

As for the problem of the limited adjustment in the current configuration, the easiest way of dealing with that would seem to be to add a second attachment point closer in toward the hinge pin to get a greater throw range. It would certainly allow the tabs to be extended down further, but two questions arise:

1) Would the tabs then withdraw upward enough to be out of the way in a following sea to be safe? and,

2) Would the resulting load on the actuators be too much for them to handle, either during the adjustment or the static load?

Again, if the new attachment point on the tabs were found to be non-workable, it would be easy to simply switch them back to the old position.

It might also be necessary to move the upper attachment of the actuators to "re-center" the adjustment range with this option.

I'm assuming a metal fabrication shop can fabricate a new attachment point on the existing tabs and make a plate to fit under the existing upturned one. These are easy operations as metal working goes. Hopefully the leading edge can be slightly upturned if necessary to accommodate the front water flow onto the tab from the transom edge so that the hinge for the front of the tab won't have to be moved.

Whether these suggestions would work and to what degree will depend on both the size of the new plate and the actual movement range achieved. Perhaps only experimentation will determine the outcome for sure. As a guideline, one could try and determine what percentage of the ideal area and throw range as found on workable Bennetts could be achieved with this set up.

One could call and talk to the technical reps at Lenco to see what they would say about the added stress put on the actuators as well as the whole re-design of the tabs.

I know Tyboo has also been thinking about this and will have several things to say here. He can also comment about the metal work hardening and fabrication issues.

Great topic! The Lencos initially looked like a great simplification from design, installation, and operational perspectives. Too bad the range just wasn't there in the original product!

Hope this helps! Joe.
 
Mark- Almost two full days and no further responses! I thought for sure one of the other Lenco owners would post on this topic.

I wrote what I did above on my general recollections of the topic from last summer. This morning, I went back at to the Lenco Trim Tabs in the Library Forum and re-read what had been posted there. A lot of these and other ideas have been discussed at length before. The only thing missing was a final solution to the problem!

Mike added some shims between the bottom of the actuator piston and the tabs, but wasn't able to get the full extension needed. A good discussion of the proper use of trim tabs also helped define how much they should be used to trim lateral loading problems versus shifting ballast, which isn't always possible. The discussion ends there. Were there any further improvements found? Does the factory still install the older model Lencos or has it gone the newer model, or back to Bennetts? Has the design been further improved?

P.S.: I'm still working on the Boarding Ladder concept for the front of the boat. The biggest problem seems to be the storage issue. I'll send you the pictures of Yellowstone John's set up right after the holidays.

Happy Holidays! Joe.
 
Joe,

I am interested in your over-the-bow boarding ladder solution. I have never put my boat on the beach due to the difficulty of climbing back onboard. Please post your solution and photos for all of us to see.

I was interested in the Lenco tabs, but this thread puts me off that idea until this problem is resolved.
 
The discussion on the Lenco tabs got dropped, I suspect, because there weren't any profound solutions. They are what they are.
I talked to and have received a couple e-mails from a rep from Lenco and the response failed to address the specific questions satisfactorily. His only solution was to go to the 12x12 tabs ( which are incidently also tapered similarly to the 9x12) and he was willing to work with me on a replacement using those. Those would probably be a little overkill, and if a person went to changing over from the 9X12's, I believe you would have to have a epoxy plugging, gelcoating, new hole drilling exercise to deal with. Then depending upon the motor pkg. you have on the boat the clearance issue comes into play.

I hung a Permatrim hydrofoil on my J90, as did DaNag on his H90, and between the foil and the 9x12 lencos I have been able to compensate. The Lencos give me adequate lateral trim and wiith the Permatrim I can jump up and stay up with a heavy load. I might sacrifice a bit on speed but Geez, I got time, and if I am losing anything it's too small to quantify.
Like Dusty said, anytime you hang something else on the hull you're going to pay a penalty in fuel, performance or both. Not a quote but that seemed to be the gist of it.

Yep the boarding ladder off the bow would be a slick add-on and it's definitely doable. John mounted another long hand rail along the outside of the cabin top (I believe on both sides). The rails were mounted on the edge where the lip is, so no screws thru the cabin roof, proper. He cradled his boarding ladder on the roof against that outside handrail and it worked out well for him. I don't see any other practical alternative to storing the ladder than utilizing the roof of the cabin. He used his ladder off the bow, side and stern, I believe and really liked it.

I got a long letter from John and he is selliing his CD "Farwest II". He has some medical challenges but apparently he is doing very well now. It sounded like he may get up the SBS this year, so you may get a chance to revisit the boarding ladder enterprise with him at that time.

It doesn't look like I'll make the SBS this year, as much as we'd like too.

Whenever you get through with the pics, Joe, I'll be interested to here your ideas on boarding ladder design. Minimizing the weight, while maintaining strength, by material selection and design would seem to be the primary challenge.

Merry Xhristmas One and All!
 
Mark,

Sure sorry you can't make the SBS. I was sure looking forward to a long visit from another of the elder statesmen!! :lol:

Best season's greetings to y'all up in Santa country.

Stay warm!

Sawdust
 
Larry- Yes, this is a major problem that needs and even BEGS for a solution. Who wants top run their smooth bottom or anti-fouling paint job up on a grough gravely or rocky beach?

I talked with Yellowstone John regarding this at the Lake Shasta C-Dogs gathering in 2001. He said he had a boarding ramp that worked both on the front, side, and back of the boat and doubled as a rear seat (!!!) It could also be stored on the roof as a alternative to being stored cross ways (athwartships) at the rear of the cockpit.

I mentioned the need for the ramp and my discussions with John in a post about 4 months ago, and Mark (3rd Byte) PM-ed me that he had photos and a written description of the project from John. He mailed them to me, and I have them in my possession now.

I'd like to get someone with a scanner to scan them and enter the text into the site here so we can work on the project together. Most of us need the front ramp more than anything else, but all the other features would be a nice bonus. I'd build his design in a minute if I thought I would be happy with the storage issue, and I just may be being too "pickyunish" about that issue.

Is there anyone out there who would volunteer to scan them into the site for us? We could easily set up a thread, and I'll type the written info into it, but we need to have the photos to have a common starting point to begin the discussion.

John's ramp is 78" long, by 9' wide, and 2 1/4" thick, made out of teak plywood (top and bottom) with wooden sides reinforced with aluminum side strips, and is foam cored. There are also stainless eyelets, a wooden lip to catch on the inside of the under gun whale storage compartments, and has 3M Non-Skid on the walking surfaces.

We need to get this underway! I'm making my own copies of the letters and having copies made of the photos. Who will volunteer to scan them into the site as part of the project?

Happy Holidays! Joe.
 
Joe,

I have a scanner and if winter? ever gets to So Cal, I'll have the time. How many photos are there?

I could pick them up from you at the Seattle BS. We will be staying at the Hawthorn Suites.
 
Hey Joe: I neglected to mention that the C-Dory factory has dropped the Lenco tabs and is using Bennetts as their standard install. That is the word from Aaron at Lenco at any rate.

With all the expertise we have on board this site we should be able to get a
workable boarding ladder schemed together. I know I have been in many situations where one would really be nice to have.

Thanks, Dusty for the kind words. I'll be thinking of you and the other C-Brats down there at the SBS, basking in that liquid sunshine, sipping a cool brew and generally having a blast! Enjoy!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Larry- There are 6 photos- 4 of the boarding ramp, and 2 of a related engine well wall project to close off the engine well from the cockpit. I'll give them to you at the SBS. I'm also staying at the Hawthorn Suites. Thanks for the help! See you then.

Mark- Thanks for the info about the Lencos. I'm sure we can build a ramp. Would like to keep the weight down as much as possible. John's weighs 26 lbs., and while that seems like a lot, all the wood, screws, glues, resin, metal, fittings, finish, foam, non-skid, etc.,......soon add up to much more than one might expect! I've built a lot of stuff for racing sailboats, and it's a tougher game than one might imagine to keep the weight to a minimum.

More on this later! Happy Holidays! Joe.
 
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