Lenco Trim Tabs

[Sneaks]

I'm gonna jump in with yet another alternative: Trimmaster hydraulic tabs.

$300 "C-Dory special" for the kit was still in effect early this month, but ask for the extra fittings for an external tubing run (free.) 9X12 or 12X12 same price. Can be installed without removing the tanks if you use a 3" piece of 1/4" npt tube to go through the transom and then one of the elbows Trimmaster furnishes to route the tubing toward the hydraulic actuator. (You will not use external tubing, just some of the fittings.)

Benefits over Lenco? Dunno, but the only power connections are behind the helm and nothing electrical external to the hull. Benefits over Bennett? Cheaper and with higher hydraulic pressure.

Critical installation tip? Tubing hole MUST be perpendicular to the transom. (I have an old electric drill jig expressly for that purpose.)

The sequence of installation (after drilling all holes) is to attach plastic hydraulic hose to the elbow fitting, screw 3" brass tube into hydraulic cylinder WITHOUT any pipe seal/lock compound, then have your friendly neighborhood knuckle dragger rotate the cylinder and tube while you thread and hold the elbow until tight and faced the right direction with the cylinder properly oriented. That joint is the only one that needs thread sealing compound, BTW, and the tube needs a little tape over the end so it stays clean inside when inserted through the transom.

Don

[TyBoo]

The only reason you need 12 x 12 with Lenco is because they do not go down in the water far enough. The stroke of the actuators and/or the mounting geometry make for insufficient travel. The Bennetts travel farther than you will ever need, but you can fix that by just letting go of the button. When you run out of stroke on the Lencos, you're done. Plus, the 90º turned down edges on the M120 Sports do for the boat tracking what the same edge design does with the Permatrim.

On the other hand - the Lencos are very well made and a good product. There is no hydraulic junk with the Lencos, and that is a major plus. The reason I went to the Lencos was exactly that. But, you see, I done learned my lesson. Those Lenco 12 x 12s should do everything you need on a CD22 and you will be very happy with them.

If you haven't bought those Permatrims yet, I would suggest you try the tabs only first. On my CD22, the tabs provided more bow down than I ever needed; I could turn the bow into a bulldozer at any speed if I wanted. Another benefit of the trim tabs is the freedom to trim the motors where physics wants them to be rather than where you need them to be for hull attitude. With the thrust running square to the water surface, you get the most efficiency and economy. Trim tabs work to force the bow down, whereas a hydrofoil serves to lift the stern and allow the bow to go down. The stern is only a few inches deep in the water when on plane anyway, so given a choice I would think that controlling the bow is preferable to lifting the stern. You should not need both the tabs and the foil unless the function of the tabs is inadequate as is the case with the two gentlemen who are struggling so with their Lencos.

Many, many people have gone through this process of finally getting tired of stretching their neck and sliding sideways in the seat to try and get the boat to stay level sideways and see over the bow. Back in the old days, the guys at C-Dory strongly advised against trim tabs, and it is kind of a mind set among us to put off getting them. But once they are on, we wonder why in the world the boat wasn't built with them in the first place. Now they are a factory option. And either for this model year, or mid-season last year, the factory switched from Lenco electrics to Bennett hydraulics. And I promise you it had nothing to do with my incessant ranting.

I also promise you that I will never make fun of your choice if you decide on the simplicity of the Lenco electric screw jacks over the potential problems of hydraulics. If your tabs have enough surface area - and at 12 x 12 they will have - they will do just what you want.

A couple of disclaimers: I usually get into trouble when I start trying to use words like physics or when I think I have it figured out how a hull goes through the water. Take everything I say under advisement until such time as DoD and SW Joe have had their chance to beat the crap out of me. I am more of a simple minded go-with-what-works guy than a scientific analyze-and-choose-the-best-design person, and when I fail, I do so miserably. I may also be mistaken about the when, why and what fors of the factory option trim tabs - but the way I stated it is the way I believe it to be at this moment.

[Norm S]

Question for those of you that have messed around with various sizes of the C Dorys. I want to put Lenco trim tabs on my 18. I like the idea of no hydraulics to deal with. I am just not sure of which size to go with. MY hull is a bit narrower than the current 19s. (7' beam) I know I'll have to notch whatever I get to clear the drains on either side. Also some metal fab and modification would not be a problem for me. In a perfect world I'd have the bennet tabs and lenco actuators. Any advice from those that have endured the pitfalls would be appreciated.
Thanks
Norm

[CAVU]

Tyboo,
Well stated. My plan was to order the standard mount actuator. It seems that the problems are with the edge mount? I like the geometry of the mount (top mount 15" up the transom) which will put the hole and wire run in the splashwell where it will be easy to join the wire loom going forward. As far as the argument about using the minimum size tab; it seems to me that the drag would be about the same if you have a 10x12 farther down in the water or a 12x12 not quite so far? You have to generate the same amount of lift to get job done. As far as the turned down edges vs the turned up-beats me. I guess the turned edges provide some stiffness, but why wouldn't Lenco turn the edges down? I think you are right about the Permatrim and I will hold off on that until I get some experience with the tabs.

[dogon dory]

Sorry, Folks - Post Deleted By Author

[Mighty Bite]

Hard to disagree too damn much with Tyboo when he puts out a manuscript on the subject. In this case he pretty much nailed it.

Ken, I agree with Mike, I would definitely go with the trim tabs first and see how they performed before thinking about the Permatrim. The tabs should allow you to get your bow down and allow you to adjust laterally for loads.

I like to take stuff like this in baby steps anyway. A step at a time is the only way I can gauge the effectiveness of a given add on or adjustment.

Chances are you wouldn't need the Permatrim for the above but the
P-trim certainly eliminates cavitation and to my mind provides an improvement in handling.

I'm guessing the "perpetual motion machine" in the DogOn's garage is wearing pants and a C-Brat cap.

[Da Nag]

Hey Mark - emails are bouncing, check your PM's....

[tpbrady]

Over the last 4 trips I have been experimenting with all the above to determine the best trim for the boat to get the best fuel economy. I'll dispense with the theoretical physics and base this on field observations.

First on my boat, there was no situation where trimming the motor up beyond parallel with the water flow did anything but decrease fuel economy and make it harder for me to see over the bow. Trimming it up was only useful for going fast inefficiently on glassy water.

If the boat was not trimmed laterally, levelling things out with the trim tabs increased efficiency even with a trim tab down.

The most efficient cruise for my boat was with the motor trimmed up slightly to make the prop parallel to the water flow, using trim tabs to level the boat, and adjusting the throttle to the desired speed.

Doing this I found three speeds with essentially the same fuel economy, 14, 18, and 22 mph. So if getting there was important and seas permit, get the speed up, but if seas are not ideal, you have some idea of where to be. Of course all of this changes with loading of the boat.

After my son told me to look back one day, I realized I didn't need all the electronics to tell me what I was doing. When I look at the rooster tail behind the motor, the right trim is to raise the motor until the rooster tail starts to climb and lower it back slightly.

[TyBoo]