AT Trim Tab versus Boat Movement
 

I am trying to find out how the AT trim tab switches make the boat react. If I press the the starboard bow down switch will the starboard bow go down?

Wire them so they do what you think/want/remember what it will do...

I have Lenco's on my Concept- bow down on that side puts the tab down on that side which the bow reacts to and goes down on that side; if only using that side the other side reacts as well and the bow goes up on the other side

If I hit down on my switches, the tabs actually go up.

Pat and I talked about your boat & the switches.
It's all in personal preference & thinking.

Sonic wires & labels them according to what the bow does.
AT wires & labels them according to what the actual tab does.

There is no switch labeled "Starboard Bow Down" If you press the tab down switch on the SB side of the boat, its going to adjust/lower the SB side trim tab, and the PORT side bow is going to lower.

& vice versa.

If you are an analytical thinker you think about what the bow does when you press a switch. If you are an engineering thinker, you think about what you want the tab to do to make the the bow react.

The good part is, you hardly ever need to use the tabs on a 37AT! Keep them at neutral and leave them there, period.

Two phrases we use on Clark's 37AT when Chuck and I are telling him how to drive:
"Trim tabs are for puzzies!"
&
"Trim tabs waste gas!"

(Clark is crb76 and chuckbeecher is his Dad.)

If you take the Tres Martin class, you will know more about (boat) trim then you ever thought possible.
(Man will never know enough about the "other" kind of trim.)

:)

They also save drives while getting on plane....no vibration

The design of the AVH hull keeps the bow down naturally. Unless you have a strong quartering wind or a bunch of fat people on one side of the boat, you hardly need them. Since the boat is wide is will cock into the wind if it gets real strong (+15MPH). That about the only time I use them on plane.

Brian,
Thank you very much for the clairification on this trim tab issue. I suppose I am an analytical thinker and I definitely want the switches wired to what the bow does. For the last 25 years all of the boats that I have had had the switches wired and labeled the way the bow moved. That is with the starboard switch wired to control starboard side bow movement and the port side switch controlling the port side bow movement. I am very aware that trim tabs waste gas & lower speeds as the 358 Sonic I had required quite a bit of tab which I did not like. Since the AT requires little or no tab played a large part in my decision to purchase an AT. My preference is that my boat have the tabs wired the same way that I am use to them reacting. I think it would not be safe for me to have to think backwards on boat movement after all these years. I have unsucessfully tried to get Pat to understand how I wanted the tabs wired and hopefully your explanation will help in resolving this issue.

Your assistance as always has been most helpful and informative.

Thanks,
Boyce

Screw worrying about how your tabs are wired. You WILL get used to it. My previous boat was wired opposite to this one, but I actually prefer this setup now.

More importantly, if you don't already have it, put some index marks on your gauge for neutral. Run the tabs to that point before coming on plane...and leave them there the rest of the day! Voila. I ran in a strong quartering wind yesterday and actually had to drop one a bit. But that is a rare occassion.

Boyce,

I came from a Sonic before my AT, so I know where you are coming from. You are in a performance boat now! :D

However, I still agree with Pat that they should be wired according to tab placement. I guarantee you will get used to it in two trips. The reason why I agree is now that you will be in a step bottom boat, you need to be precise with all of your trim placements.

I'll explain by example:
If you are going into a sharp turn to port, at speed; you need to make sure that you know exactly where your port trim tab is set. IF your port tab is down a fair amount due to adjusting for ride comfort/balancing, and you go into a hard banking turn to port, your lowered port tab will be lifting the transom of the boat out of the water, counteracting the force of the drives. In a bad wave bounce, you could loosen up the transom of the boat and get yourself out of shape. Hence why I recommend knowing and going with exact trim placement (tabs and drives) in the way your operate and dial in the boat for constant changing conditions.

Macklin's comments are dead on about marking neutral on your drives and tabs. Pat or I can guide you on how to do this. As you learn your new boat, basically set everything at neutral EACH time out, and tweak from there. You DO NOT TRIM THIS BOAT OUT like a Sonic. (I'm not yelling, just emphasizing.)

You will probably run your drives 1-2.5 ticks up from neutral, and your tabs will be never more than 1 tick down from neutral unless you have a strong quartering sea or 3 fat chicks on one side. DO NOT trim the drives in before a turn! You have to keep them out and planted into a turn to the keep the transom in contact with the water. These are more things that the class talks about.

I was just razzing Clark (crb76) about the trim tabs. I actually use my trim tabs every time I get on plane now due to listening to Clark.

So the conclusion is to not have any Fat chicks on the boat and you are all set. But seriously if you take the Tres class it will be completely different than what you are used to for sure but definitely a must class to attend. It took me a few trips to get used to it as well but now it is second nature. When using your tabs make a small adjustment at a time and wait a 1/2 a second for the boat to react, otherwise you will be chasing your horizon line. But once you get used to it the ride on these are second to none especially in the rough stuff, I have passed many faster boats in the rough due to the fact that they could not handle it as well as the 37 A/T. Biggest key to remember is to neutral your drives and tabs in a turn or it will get you in trouble someday, drives in tabs down on take off and start to brings tabs up as you feel the nose steer then adjust accordingly to the sea conditions. Coming from a standard V hull took me a bit to get used to it and still learning the fine points every time out.

Can someone tell me about the vibration on the 37 AT? I had a vibration problem with the 358 Sonic with 30 Bravo 1 4 blade props. The vibration was of fairly short duration when coming out of the hole with a pretty heavy load. I switched to 5 blade hydro's and the problem was solved. Anyone have similar experiance with the 37 AT.

I've never heard of a vibration before but If you had one I would think it had to be a prop out of balance.

I've never felt it before on any of the 37ATs, and I've been on a lot of them. (There was the one time when I ICBM'd a prop blade, but that's a different story.)

Clark claims he feels some vibration when getting on plane using the 4 blades and no tabs, but I think it has to do with how aggressive your props are tweaked and correspondingly how aggressively you have to accelerate to get out of the hole.

Just to compare to Sonic, and Fountain, and others with an integrated swim platform... when the boat is pitching up when coming on plane causing the swim platform to make a solid "cup" over the water; the air pressure building up from the exhaust will cause a vibration until you get the transom up out of the water. Attached pic shows example of this with my old 26' Sonic.

I have to agree with Brian..I believe it is with how agressive you bring the power up and even with slow increases the disturbed water coming off the bottom and transom and the 4 blades(reworked or not) aren't really biting. I'm also a big believer it could also have to do with X demension.
I-Lean(serial #1 with step) and the other 37 with boxes that I have experience with never did it. Those you could always just bring the power right on up and no problem...right on up not slamming them..
BUT tabs always helps any of them jump up easier.
As for indicators and indications..just remember any thing hanging off the back:
if it goes down the bow goes down
if it goes up the bow goes up
remember that and you can do it with out any indicators just takes practice
I was taught by someone, with racing experience, years ago how to handle a quartering sea or strong wind with just splitting the drives to level the boat
and if the boat is launching it takes the load off the drive hitting first.

No vibration at all on the A/T ! Possibly prop slip on the 4 blade 32's in fresh water, but I am yet to experience vibration at all. Heavy load or light load no vibration, went to 5 blade Hydros due to fresh water and elevation and they bite real nice, but still looking to try a pair of labbed 30's just to see the numbers.

Vibration is prop specific. Has nothing to do with the boat or the way you bring it up. You can mitigate it with tabs. I have been known to try more than one set of props! 

Brian, My Maximums vibrated not the four blades. I had the Max re-balanced by Throttle Up and it fixed it. I think is has a lot to do with trying to run too big of a wheel without having them balanced properly.

Laszlo, labbed 30's suck. Also, AT's have high slip. That is the bottom line and there little to do to change it. I believe it has to do with the flow of the water off the large front step, thru the pad, and then off the back. However I am no expert.

The only boat that I knew that had low slip was Thunder Roy's boat. The one in the classified with 500's and boxes. That boat had a blue printed bottom and the boxes pushed the props back far enough that the wheels ran in cleaner water, thus the reason for less slip.

Please, lets not have a box conversation!

Thanks for clarifying Clark!

Gents, don't be afraid to try a couple different set of props if you feel froggy. Brett at BBlades knows his stuff and can help you tune until your heart or wallet is content. Personally, I just pick an all around great set of props, and stick with them. I have two pair, stock 4 blades and labbed 4 blades. I think I have run the labbed props for a total of 1 day. They just stay in the boxes nice and pretty.

Clark's boat is heavier than most of the other late model 37ATs due to his custom cabin configuration, but it still runs 90mph GPS with Herrings behind the 525/XRs.

Yo laszlo - I heard there was a blue Active Thunder that made its way down by Pier 75 in Toledo this weekend, any chance that was you?

That was us, we decided to stay south due to weather so we took a trip down the Maumee, got lots of looks for sure.

Just to have fun, should we Box or not ? As that would put the props in cleaner water.

Just for grins, next time you're out, trying raising the drive on the high side when you have a lean instead of dropping the tab on the low side and let me know what you think.

Tabs even with hull......lead the pack for 45 minutes down the bay :)

http://i295.photobucket.com/albums/m...ni_Run-218.jpg

And I got the big ones for my 25:grinser010:

Hard to tell John, but the tab looks all the way up.......?

I did that after you showed me that little trick and it caused my oil temp to climb on the low side.

Set at 3.

I should have had them a little deeper on that run on the James!!:boat:

Engine builder.....:party-smiley-004:

I like your train of thought, makes sense. It will be on the fine tuning list for sure.


QUOTE=ActiveThunder;2920052]Just for grins, next time you're out, trying raising the drive on the high side when you have a lean instead of dropping the tab on the low side and let me know what you think.[/QUOTE]

Good thread! Being a new to boating I`ve been trying to figure out all the relationships between trim, tabs, etc.

Since day one the boat leans to the left so I have to have the left side set to about 4. the other side I keep at 0
This keeps the boat level but with lake Michigan chop anything over 40mph it keeps flying out of the water. using the trim to lower the bow kills speed and I`m sure eats more gas. Trimming up makes it even worse
This weekend I tried lowering both the tabs and that seemed to lower the bow for a smoother ride but not kill speed as much.. then using the trim didn`t seem to make too much difference..

Damn I got a lot to learn..

If I read the above right :eek::eek:
you can get in BIG trouble having one down significantly and none on the other side.
I was always taught to have them both in the water ..then add more of one or the other.
if say "3" is level with bottom of boat(assuming "0' is all the way up) then have both at "3" then drop high side to "4" and low side more(deeper)

280's? I got 380's on my 25, there's a little bit more going on out back though:coolcowboy:I only use em when the ol' lady starts crying, which isn't often