Smart Tabs Question

[John_S]

Re: Smart Tabs Question

Yes the rpms go up, but that doesn't mean gas milage goes down. You gained rpms by not moving the throttle plates one iota.

Try thinking about it in reverse. Lets say your bost is most efficient at the 90 degree trim. At a given throttle position you are doing 3000 rpms and 30mph. You toss a tube behind your boat, causing more drag. RPMs and speed go down. Gas milage will go down.

 

[John_S]

Re: Smart Tabs Question

You guys really do need to check out this link! Pictures speak a thousand words and I have typed atleast that many:facepalm:
http://www.nauticusinc.com/pdf/nauticus_smart_tabs_tech_info.pdf
Anyone have a fuel flow meter on there boat?

I think you are confusing prop angle efficiency from John's website, with trim position, and fuel efficiency. Prop angle is in respect to perpendicular to the water surface. Trim angle of 90 degrees with boat, does not always equal prop angle.

Lets say we are at the perfect 90 degree trim position, doing that 30mph at 3000 rpms again. I trim out some, my bow rises. If my bow rises, it means that prop angle has changed very little or none at all. If my bow didn't rise then only the prop angle changed. BTW, I am not saying that 90 degree prop angle is the most efficient, either. While the pictures try to simplify and make it rather obvious, I'll stick with my prior statement. At any given throttle position, the trim position with the highest speed will be the most efficient.

Ie, while I can easily tell my trim position in relation to boat via the trim gauge, I can't tell the prop angle and its relation to the surface of the water.

BTW, while John makes a good product, that doesn't mean everything on his website is gospell for all boat/hull/motor combinations.

 

[QC]

Re: Smart Tabs Question

Yes, throttle position pretty much determines fuel use in an Otto cycle engine (throttle and spark plugs). Throttle equals air flow, air flow equals fuel use. It is not as simple as that, because RPM plays a role. Very small role as compared to load in a marine application. Do not confuse this with automotive, not everything translates . . .

You don't want to turn this into anymore of a throttle discussion than we have got into here. That one will make your head spin.

Oh, and John_S' posts are spot on

 

[chriscraft254]

Re: Smart Tabs Question

The more rpms you have, the higher rate of fuel burn you will see! That does not have anything to do with speed and resistance. If you run a motor just by its self and increase the rpms, the fuel burn increases. Fuel consumption can obviously be effected by drag and load. If you toss that tube out there, what would you have to do to cause the boat to stay at the same speed? You would have to add more throttle = more rpms, so your fuel consumption goes up. More rpms does mean more fuel consumption. But then you do have to figure in how many miles per gallon your getting.

Yes the rpms go up, but that doesn't mean gas milage goes down. You gained rpms by not moving the throttle plates one iota.

Try thinking about it in reverse. Lets say your bost is most efficient at the 90 degree trim. At a given throttle position you are doing 3000 rpms and 30mph. You toss a tube behind your boat, causing more drag. RPMs and speed go down. Gas milage will go down.

 

[chriscraft254]

Re: Smart Tabs Question

I'm not confusing anything. I think many here are though. Prop angle is what will give you a specific thrust at a specific angle. Every prop and every boat has a position that is most efficient. Trim tabs will give you the best bang for your buck in positioning the boat in the most efficeint manner to provide the most benifit from the thrust of the motor/prop. Without trim tabs you are working much harder to get a stern drive boat out of the water.

If you are on plane, and you change the tilt on your prop, it may not be much but it is changing the thrust angle. Very little, I will give you that, but it is changing the angle of thrust.

Without trim tabs the angle in which the motor has to be tilted in much more drastic and cost people performance.

By the way, I didn't say Johns website was gospel, but it is common sense. It seems that even looking at diagrams people have a hard time understanding this. Simply put, if your boat is brought out of the water faster, with less rpms, at lower speed, you have a much more efficient boat than without trim tabs. Using your motor to acheive this is not efficient.

 

[John_S]

Re: Smart Tabs Question

Sounds like you may not have the right actuators or have them adjusted properly.

It sounds like you are very excited about your first pair of smart tabs and how much they changed your boat handling. I remember thoses days, and have a very good handle on adjusting these tabs for the boats I have them on. I've had them long enough for the rubber boots to fail, and the cylinders to fail. BTW, John replaced them for me.

For one, for my boats and use, there isn't a one adjustment position that is the perfect and ideal spot for all the different aspects that they can correct. Like most things, there is always a compromise.

For my bowrider I tweak them to eliminate porposing and chine walk at the highest speed possible. This position is not the most ideal for keeping the most level boat while getting on plane. They still provide allot of bow rise control during planning, just not the most perfect position for that. My boat has plenty of power and getting on plane is no issue.

I have also found that the tweaking changes between prop types. A four blade solas (has more stearn lift) then a three blade hustler, which then the smart tabs can be adjusted again. Adjusting and making numerous runs isn't trival on a small lake.

 

[John_S]

Re: Smart Tabs Question

I'm not confusing anything. I think many here are though. Prop angle is what will give you a specific thrust at a specific angle. Every prop and every boat has a position that is most efficient. Trim tabs will give you the best bang for your buck in positioning the boat in the most efficeint manner to provide the most benifit from the thrust of the motor/prop. Without trim tabs you are working much harder to get a stern drive boat out of the water.

If you are on plane, and you change the tilt on your prop, it may not be much but it is changing the thrust angle. Very little, I will give you that, but it is changing the angle of thrust.

Without trim tabs the angle in which the motor has to be tilted in much more drastic and cost people performance.

By the way, I didn't say Johns website was gospel, but it is common sense. It seems that even looking at diagrams people have a hard time understanding this. Simply put, if your boat is brought out of the water faster, with less rpms, at lower speed, you have a much more efficient boat than without trim tabs. Using your motor to acheive this is not efficient.

How do you tell if your boat is running at the perfect prop angle in respect to the surface? Tell me how you measured yours to any degree of accuracy that you know that the claims are true?

Yes, tabs will have some slight gas saving for getting on plane for some hulls. If you are worried about gas milage in a boat, it is once you are on plane and traveling long distances. Most that are, install a fuel flow gauge and watch it like a hawk. You can do that on your boat, and see if QC and I have steered you wrong.

 

[metalwizard]

Re: Smart Tabs Question

WOW GUYS, Thank you for the input it is going to take me a WHILE to absorb a LOT of that.

Bottom line. My Trim motor got delayed by the hurricane. so I doubt it will go in this weekend.

I am going to set the trim as close to centered as i can for now.
I know it will change when I get the motor in.

So far the boat does pretty good. but I do Porpous (SP?) when I come out of the hole. and when I hit other wake so I am SURE the smart tabs are going to help.

everyones input has helpped me understand a bit more how it all works together. so I think I have a great starting point.

She goes in the water again in the AM. I will report back.

Thanks guys... and please no fighting, but Input is AWESOME AND GREATLY appreciated!!

 

[John_S]

Re: Smart Tabs Question

I'll be very interested in your results, especially after you get the trim fixed. The last tri-hull I road in, was a 14' mfg with a merc staight 6 cyl 90hp outboard.

 

[chriscraft254]

Re: Smart Tabs Question

Why do you think I asked earlier if anyone had a fuel flow meter on there boat? I installed one before I had the tabs installed. Though there are always going to be discrepancies because of wind, sea conditions etc. , the proof is in the pudding.

I gained 4 to 5 mph at wot.
I plained in atleast half the time w/half the rpms.
My bow rise while getting on plane decreased atleast 50% set on the center position on the tabs.
I can cruise at 22 mph compared to 29 mph before tabs.
I gained 1 mpg at 3000 rpms with tabs
I gained almost 2 at 4000 rpms with tabs
I gained 2 miles per gallon at 4500 rpms with tabs.
I did not get the wot numbers because I was still breaking-in new motor.

I tested in fairly calm conditions both times.
I tested going up river 10 miles and returning down river 10 miles. The boat was kept with in 300 yards of the shore to assure I was going through similar waters/wind on the way up and back. I did the testing during the week with very little traffic so I would not have to throttle down. The boat imo saw major improvement.

Now, if you had seen that much improvement, don't you think it would be pretty convincing?

As far as the prop angle, on my boat, I don't have very much negative trim when at rest with the motor fully down. The boat while tested was never adjusted because it didn't half to be. The optimal position for the motor is 90 degrees to the transom of the boat, not the water surface.

How do you tell if your boat is running at the perfect prop angle in respect to the surface? Tell me how you measured yours to any degree of accuracy that you know that the claims are true?

Yes, tabs will have some slight gas saving for getting on plane for some hulls. If you are worried about gas milage in a boat, it is once you are on plane and traveling long distances. Most that are, install a fuel flow gauge and watch it like a hawk. You can do that on your boat, and see if QC and I have steered you wrong.

 

[John_S]

Re: Smart Tabs Question

So, by triming out on your boat, does it have enough power to lift the hull out of the water, raising rpms, further or not? tabs or not? Given from what I can see in the icon pic, it wouldn't surprise me if it can't. If it does, than you can do the test. That size/type of boat, generally come with factory options for tabs, because they do make significant difference.

Let's try the fuel effeciency example one more time. Trim is at 90 degrees going 3000 rpms at 30mph at a particular throttle point. Trim is raised slightly, boat rpms go up to 3200 and speed at 32mph. Leaving the trim in the same place, move the throttle down slightly so speed drops to 30mph and rpms will be 3000. Now, you are at same speed and rpm with less throttle opening. Now, you can move the trim back to where it was and rpms and speed will drop. Would you say that is more efficent at 90 or slightly out trim position?

 

[metalwizard]

Re: Smart Tabs Question

Alrighty... here is my report back.

Took her out on the water.

She comes out of the hole and onto plane WAY faster. I MEAN WAY faster.

the bowrise is GONE 100%... NONE ZIP ZERO NADDA...

she planes out at much slower speed. down to about 15mph maybe even less.

Turning... WOW what a difference She stays WAY flatter in the turn. turns MUCH smoother. BIG difference.

CHOP.... Well being a trihull I felt EVERYTHING before. now when I cross others wake etc it seems WAY smoother. AND no more bow rise when I do.

MPH ok remember I DONT HAVE A TRIM MOTOR.. (got stuck in shipping because of the hurricane. I was hoping oto have it.. but no such luck.

Before 3900 RPM was max. about 37 38 mph max. NOW first time out 4200 RPM (wot) and slowed down to 30 MPH. I KNOW the bow was low. so I took it back out of the water got out the Makita adjusted the front of the motor down maybe 1/4" to 1/2 at the very most. put it back on the water and OOOOPPPPSS almost sunk her (damn I took the plug out and never put it back in...) so after a quick swim at the dock area and 10 mins running the bilge Back on the lake.

Still rode AWESOME. the water was a bit choppier, (lots of skiers on the water) so it seemed rougher. My RPM's stayed at about 4200 but I was able to get up to 32 MPH..

After that I went swimming with the kids. so no more adjustments. I am convinced once I get a trim motor in her, I will be able to trim it to get my top speed back up to where it was.

I do have one little issue. it seemed to be leaning to the PORT side a bit. (while moving) I monder if I have them a little off... not quite even or square..

I hope to have a trim motor soon I will tell you what happens them I also might try moving the tab adjustment in a bit to soften them up.. I think this will help with the top speed a bit too.

 

[chriscraft254]

Re: Smart Tabs Question

Sounds good! But if your bow is staying down completely and your loosing speed, you probably want to adjust the tabs. Your tabs are different from mine,so use your manual to adjust. You may want to double check that you have both tabs in the same adjustment hole on both sides. The tabs should not be making your boat lean, if anything it will ride more level. The bow should not be pushed so far down as to cost you speed. You need to find the right adjustment. Your motor for testing should be as close to 90 degrees as you can get it with the transom.

Post up some pics of your install. If you don't know how to post the pic, I will pm you with me email so you can send it to me. You might want to call John at nauticus tuesday and discuss the leaning with him also. I'm sure they can point you in the right direction. Did you have the leaning issue before or after trying to sink the boat at the ramp? You may have added water weight to one side or the other.

If you are loosing top end speed, try adjusting the tabs, you will eventually dial them in so you have enough lift for planing and enough relaxation of the tabs for improved speed. The actuator cylinders are valved to relax after a certain pressure is obtained. If you don't see improved wot speed, I would talk to John at nauticus, they may want to give you different size actuators. Over all, sounds like you have major improvements you just need to adjust them for your boat.

The turning was something that really impressed me too when I installed mine. Plus no cavitation at all and I could turn harder at any speed. Glad you like them and good luck on getting the motor trim fixed. Keep us posted.

Alrighty... here is my report back.

Took her out on the water.

She comes out of the hole and onto plane WAY faster. I MEAN WAY faster.

the bowrise is GONE 100%... NONE ZIP ZERO NADDA...

she planes out at much slower speed. down to about 15mph maybe even less.

Turning... WOW what a difference She stays WAY flatter in the turn. turns MUCH smoother. BIG difference.

CHOP.... Well being a trihull I felt EVERYTHING before. now when I cross others wake etc it seems WAY smoother. AND no more bow rise when I do.

MPH ok remember I DONT HAVE A TRIM MOTOR.. (got stuck in shipping because of the hurricane. I was hoping oto have it.. but no such luck.

Before 3900 RPM was max. about 37 38 mph max. NOW first time out 4200 RPM (wot) and slowed down to 30 MPH. I KNOW the bow was low. so I took it back out of the water got out the Makita adjusted the front of the motor down maybe 1/4" to 1/2 at the very most. put it back on the water and OOOOPPPPSS almost sunk her (damn I took the plug out and never put it back in...) so after a quick swim at the dock area and 10 mins running the bilge Back on the lake.

Still rode AWESOME. the water was a bit choppier, (lots of skiers on the water) so it seemed rougher. My RPM's stayed at about 4200 but I was able to get up to 32 MPH..

After that I went swimming with the kids. so no more adjustments. I am convinced once I get a trim motor in her, I will be able to trim it to get my top speed back up to where it was.

I do have one little issue. it seemed to be leaning to the PORT side a bit. (while moving) I monder if I have them a little off... not quite even or square..

I hope to have a trim motor soon I will tell you what happens them I also might try moving the tab adjustment in a bit to soften them up.. I think this will help with the top speed a bit too.

 

[metalwizard]

Re: Smart Tabs Question

Thanks Chris,

Yeah It turns AWESOME and like you said NO cavitation. I only dropped maybe 2 or 3 MPH on a pretty sharp turn.

I KNOW I have them BOTH in the same hole. )middle one) so they are adjusted even (for the lean) they may not be perfectly even though. Like I said, the trihull made my choices of where to put them pretty limited.

I'll post some pics after the holiday weekend is over. I also agree with you. I think going down a hole or two on the adjustment will help. My dumbazz didn't bring wrenches with me to make the adjustment LOL oh well. I was thinking about finding a couple quick pins that fit the adjustment holes... No real tools needed that way.

Seriously it was GREAT improvement. and I know now it is just a matter of dialing her in. I would have taken some time to do that. but it's a 3 day weekend I took the kids, It preformed good enough to enjoy it and let the kids have some fun. I'll take it out one day while they are in school when I can play with it..

 

[chriscraft254]

Re: Smart Tabs Question

The lean, was it there before you tried to sink the boat at the dock? Also did it lean before the tabs were installed. Also could be your torque zink above your propeller isn't adjusted properly. Could be many things is all I'm saying. Could also be like you said that you one of the tabs isn't located even with the other one. Good luck

 

[metalwizard]

Re: Smart Tabs Question

Chris,

Yes it did lean before I tried to sink it, but Good though water could have been trapped on that side..

Ok I think I found one big issue. Look at my transom it is NOT straight up and down its at a STEEP angle.

I BET the tabs are TOO farin the water. I think I need to level the boat out to the ground. then set the smart tabs at the 25 deg (or whatever it is) from the GROUND not from the transom. it makes TOTAL sense. they are just WAY TO FAR in the water so they are dragging and slowing me way down.

here are a BUNCH of pics sorry they are big but I figured they might help out.

 

[metalwizard]

Re: Smart Tabs Question

 

[metalwizard]

Re: Smart Tabs Question

While I am Asking. see where my speedo Pitot is? right next to the right smart tab..... I wonder if that could be messing with my speedometer reading???? I don;t have a gps to check it...

 

[John_S]

Re: Smart Tabs Question

Don't worry, most transoms are not straight. The angle is from the bottom of the hull. Could you pop the pins and lift the tabs and take a picture of the hull? While your bow may be trihull, the transom looks like a standard V with chines. If so, they should be mounted just inward from the chines, and parrellel to the v.

 

[metalwizard]

Re: Smart Tabs Question

John,

Ill pop them off and take a picture. it actually does drop back down again making it tri hull in the back.

Do I have them to far out?

and do I need to make them 23 deg from the hul not the transom.