posted 02-19-2004 11:18 AM ET (US)        

http://www.smarttabs.co.nz/smarttabs.html

Sounds like an automatic trimming, affordable trim tab solution for the small boat (under 21')

posted 02-19-2004 03:51 PM ET (US)            

I can also tell you that how I use my tabs is widely different depending on conditions and loading in the boat. These tabs don't know anything about that except the force of the water moving them up and down. So, you would have a hard time optimizing the trim of the boat and the efficiency because of the variability of conditions.

J

posted 02-19-2004 08:58 PM ET (US)            

Do you really fine tune your tabs that much to the conditions (this might be a stupid ? since you are an engineer :)!

posted 02-20-2004 12:11 PM ET (US)            

The amount of lift, and hence drag, of tabs is dependent on angle of attack and speed, right?

At some point, as speed goes up, the springs in the SmartTab gas struts begin compressing, causing the angle of attack to decrease. Whether total lift, and hence total drag, then remains constant as speed increases (and angle of attack decreases), or whether it still increases at a lower rate, can't be determined without a lot more info.

If the total lift and drag being generated by the SmartTabs is remaining constant as the springs increasingly compress (and the angle of attack decreases) with increasing speed, the portion of the lift applied to the boat has to be decreasing. And that could be okay, with the hull providing additional lift as speed increases.

But the point is, the SmartTabs have to be providing lift, and hence be creating drag, whether that lift is being applied to the hull or it's being applied to compress the springs.

The SmartTabs are always creating lift and drag, where electric or hydraulic tabs can be set not to do so.

Right?

posted 02-20-2004 07:31 PM ET (US)            

light breeze (10kn or so). For a full power run down wind (WOT), no tabs will be required. The boat has enough power to hold itself very flat, and the tail wind doesn't force a lot of air under the boat (quite the opposite). When I turn around and run into the wind and light chop, the ride will be different and may require a touch of tab to keep the bow down a bit.

The other example is take that same run downwind. Suddenly I see a large set of boat wakes heading toward me. I would put a bunch of tab in to bring the bow down for its fine entry to get through the waves. Then after I was through them, i would take the tab off again (raise). So, I only needed the drag for a bit to adjust trim. The smart tabs would have the drag there all the time - even when I don't want it.

The tabs do make a substantial and significant change to the attitude and ride of the boat. You can feel it in the steering and hear it in the loading on the motor. I think the bigger the water you are on (chop and conditions) the more you will appreciate what they do. For small inland lakes, probably not a big deal.

So, I don't have to adjust the tabs that much (engineering geek factor aside), but unless the conditions are identical, loading of the boat is identical, then there are different tab settings (more or less lift/drag). The result is that I think you would have a very narrow window of performance where the smart tabs are properly adjusting the trim of the boat.

The tab manufacturers all tell you to run your boat at WOT (usually maximum hull efficiency through the water) and try to replicate that trim position with the tabs. At that position, you usually don't need tabs anymore. These smart tabs will still be pressing on the water in exactly the scenario that Moe describes.

These things (Smart Tabs) are not all that cheap either ($190 for 12x9 Smarta tabs vs $450 for Lenco 12x9s). If you are going to drill the holes, I'd just install the real thing. They are easy to install (Lencos, can't speak for Bennetts, don't have 'em).

posted 02-20-2004 09:22 PM ET (US)            

The trim tabs look extremely well built. I haven't had the opportunity yet to take the boat out in any conditions that would really test the tabs (I just put them on two weeks ago). I'm taking the boat out tomorrow to do a little striper fishing, and I'm anticipating that it will be a bit windy. So hopefully I'll get to really try them tomorrow.

posted 02-21-2004 10:51 PM ET (US)            

Much wisdom have I seen in this thread, so I'll stop trying to be frugal and pony up for the real trim tabs.....

that said, do you guys use a console mounted trim tab position indicator, or just go by feel?

posted 02-22-2004 08:05 PM ET (US)            

I thought long and hard about installation on these. What came down to it for me was the ease of the Lenco tabs and the lack of hyrdaulics. The hydraulics mean adding an additional component (pump and resevoir), having another fluid level to monitor, and the potential for another fluid spill. Because the Dauntless doesn't have a lot of room for mounting things when you get right down to it, that was a big factor for me. With the Lencos, all you have to do is to pull the control lines through the tunnel and your done.

It took me 2 hours to install the Lenco tabs. I was able to do it all with my Leatherman, a fish tape, and a power drill with hole saw (so pretty simple overall). The expectation of time for Bennetts is somewhat longer from what I have read and there is more fooling around.

In construction, I prefer the metal construction of the Lenco jack screws vs Bennett's plastic pistons. I also like the idea that the jack screws will hold position if they fail. The hyrdaulic cylinders will release if pressure is lost.

I also liked the more finished appearrance of the Lenco tabs (but that is just esthetics).

Arguing against that was Bennett's reputation and long standing customer service. That all being said, I broke a part intalling my Lencos and Lenco Fed Exed P1 the part to me next day. Their tech support has been just as knowledgeable as Bennett and just as available.

Others have had equally good luck with their Bennett's so I think this is probably not an place where you can really go wrong. I think if you can get past the Bennett mounting issue then it is probably a horse a piece.

Anyhow, I'm not trying to start a B Vs L war here (because both are great companies) just telling you how I made my selection.

J

posted 02-23-2004 10:28 AM ET (US)            

I'll take a look at both the Lenco and Bennett's before installing in the spring.

PS what a nice difference in ride/rpms/top end speed raising the motor all the way to the top hole made - just a matter of caulk and time:-)

posted 02-24-2004 05:43 PM ET (US)            

Dealers almost always mount them all the way down or at least too low. makes you wonder if they ever got out and use the products they sell!

posted 04-15-2004 01:09 PM ET (US)            

There is probably wood on one side (port) for mounting a ladder or kicker motor. However, where the tabs mount at the bottom of the hull is where there is a whole lot of fiberglass from mating the hull and the transom. More than enough to mount the tabs. THis is especially true since the forces are in shear to the surface of the transom and not along the long axis of the boat.

Yes, you seal it all up with 5200.

I would call up Bennett or Lenco and ask them about this mounting. In my experience, they have big experience with mounting these on whalers of all models and will be able to tell you the issues. Both are very honest and upfront with the problems and benefits.

posted 04-25-2004 09:27 PM ET (US)            

Have you tried adjusting the vertical height of the motor? How about the angle of the motor to the transom (really easy)? What happens when you move weight forward in the boat, does that help? Does your motor have a fin on it?

I would think you would have no problem making that boat plane with a 20HP motor set up correctly.

posted 04-26-2004 01:15 PM ET (US)            

It's hard to tell, but it appears the motor's anti-ventilation plate is 1.5-2" or more below the bottom of the boat. This is going to push the bow up pretty high on take-off.

It also looks like most of the weight is in the stern of the boat, which doesn't help keep the bow down. Can you remount the battery up under the forward seat and extend the fuel line to get the tank up ahead of it?

posted 04-26-2004 05:20 PM ET (US)            

Thanks for taking your time. The antiventilation plate is level with the hull of the boat. it is a matter of perspective. However, the tank and myself at 85 Kg are in the back. My brother at 85 Kg is in the front and this helped. It takes a while to plane as the motor doesn't seem to be powerful enough. I will try placing the tank beneath the front bunk.

Regards,

posted 04-26-2004 09:19 PM ET (US)            

When the fin is operating properly, and the boat is on a plane, then the fin ideally should be riding pretty much at the water air interface. It can be a little lower since the water is disturbed by the leg of the motor passing through it. However, it needs to ride on top of the 'solid' water.

I'm not sure about the 11' boat, but whaler recommends on the Dauntless series that the AV plate be 3/4" ABOVE the bottom of the hull. In point of fact, it seems on most boats here that the common knowledge is that this be at 1.5" or so above the bottom of the boat. On mine, (Dauntless 15), that means all the way up.

What you want to do is to move the motor up as high as you can and still keep cooling water and not have the prop blow out in a turn.

Since two guys and gear in the boat is probably a pretty good load, the boat is going to want to sit lower anyhow. So, that also argues for raising the motor higher.

If this doesn't work and the motor is developing full revs, then you might need to look at putting a different prop on the motor. My bet is that this is also probably not right and you might want to get Sal (the prop expert) to comment on the proper selection. If Sal doesn't bite, then call Stiletto Props (they are on the internet) and they can give you a good recommendation about the right prop for that boat and motor.

In parallel, you might want to have the motor tested for leakdown to make sure the rings and valves are ok. If they leak, you can get full revs but not full power.

Looks like a nice boat. I'm sure you are going to have a good time with her once you get this all figured out. When I was growing up, our first boat was a 14' fiberglass boat with a 1969 or so 25HP Montgomery Wards motor (actually, a Johnson I believe) on it. We all used to water ski behind that boat for years. So, I'm thinking that with a 20HP on your 11' boat, it ought to just fly with it all set up properly.

Sounds like a fun project.

posted 04-27-2004 08:40 AM ET (US)            

at first, my motor was sitting low, with the whale tail.

poor, poor performance.

I've raised my motor, got rid of the whale tail. it is much more responsive although it is nose up for a little bit...much better with 2 people than one.

I just received the smart tabs and will be putting on my 13'. Hopefully mid May I'll be back at the lake and test them and I'll post how it works for my 13'

posted 04-28-2004 09:51 PM ET (US)            

Bet it helps too.

posted 04-29-2004 08:28 AM ET (US)            

From my research, the whale tail keeps creating lift, whereas the smart tabs create lift at slow speeds, then once the pressure of the water equalizes with the hull, they are not creating lift.

posted 04-29-2004 10:20 AM ET (US)            

if you want an in depth conversation on them, call John (number is listed in the site). He will take whatever time is needed for you to understand the concept.

take a look at this post from another forum where someone just put them on

http://www.themarinedoctor.com/cgi-bin/YaBB.pl?board=BO;action=display;num=1083178525

cut planing time in 1/2, reduced slow plane speed from 25mhp to 15mhp, gained 1mph....

posted 04-30-2004 12:01 AM ET (US)            

What you can't do with these is remove them from the boat trim equation at all like you can do with conventional tabs. For example, if you are going downwind at full tilt, you don't need tabs. But if you turn around and go upwind on the opposite course, in order to maintain the same boat attitude, you probably will. The wind speed added to the boat speed, helps get air under the boat and raise the bow. So, it is common in a boat that porpoises to need tabs to take out the porpoising going upwind in this example, but not on the opposite downwind run. Regular tabs can adjust for this as you can with a fin and trim and tilt. The Smart Tabs obviously cannot be adjusted. The real question, is does it matter and is there a significant performance hit in this case? I don't know and it would be very interesting to know.

If the Smart Tabs are in contact with the water and they are trying to push down, then they are providing lift and drag. My guess is that this lift and drag is nonlinear. The most lift and drag are provided at the lowest speeds since the strength of the spring is a larger fraction of the force provided by the moving water. As the boat speed increases, this force of the water (IIRC) increases as the square of the speed but the spring force provided is a constant. So at high speed, the force of the moving water has to be far higher than the spring force opposing it - i.e. lower lift and drag as a percentage. So, at WOT or high speed there probably is little performance or economy (gas) savings but I would think that if there were an effect it would be in the range just after achieving a plane slow planing speeds. In this range the Smart Tabs would be achieving a higher deflection than may be needed. Again, it would be interesting to know if this matters.

If I am understanding what is being said here about the adjustments that were made , is that you have changed two things (at least from what has been written) at the same time - the motor was raised AND the fin removed. In order to say that the fin didn't work or the motor being raised didn't work, just one of those things would need to be done at one time. It is impossible to tell if the raising the motor or the removing the fin brought the performance change or what the impact of either was.

So before it can be said that a fin would not work here, it would be necessary to raise the motor with the fin and observe the change. Then remove the fin and observe again. Additionally, since the fin and height are not independent, this is even more important to prove that the tail doesn't work.

From an economic perspective this could conceivably lead to a considerably cheaper solution - $105-210 for Smart Tabs and $25-$100 for fins depending on boat and application. Although, heaven knows, if we were all worried about economical solutions we probably wouldn't own Whalers or perhaps even boats at all!

My experience has been that a fin mounted too low - so that it is under the water all the time does significantly hurt the performance and ride. Under water it presents a very significant amount of drag and probably inconsistent lift depending on the pitch and attitude it presents to the water coming at it. A fin mounted at the right height so it planes at the surface on a plane does work pretty well in most applications.

Good luck with your Smart Tabs. Let us know how they work.