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Trim Tab Angle
- Thread starter BigMac
- Start date
Daddy Dave
Well-known member
I learned the expensive way that the trailing edge of an electric trim tab needs to be about 2" up from level with the hull when fully retracted. That's so the tab wont force the screw ram backward when your boat pulls up on an embankment or runs across a bump on the ground.
Also, it is almost always necessary to block the little triangle out from the hull so the round ram that operates the tab won't bind and break the shear pin at the upper hinge point.
Also, it is almost always necessary to block the little triangle out from the hull so the round ram that operates the tab won't bind and break the shear pin at the upper hinge point.
Rich Andrews
Well-known member
don't know how bad your boat needs one, but I ran an old thurman that had a 10 inch wide tab(may have been 12), and before I sold it we cut it down to half the width, and it worked as good as when it was full size. I can remember times when pulling up on dry and forgetting that dam thing was down, and plowing a trail behind me. I think I had the worlds strongest electric trim tab at one point.
I have always built my own electric trim tabs from electric window drives in cars. How far down it travels will depend on YOUR particular hull and also on WHAT SPEED you are running at the moment. Mine would go nearly vertical in both directions.
Having said this I agree with BIgDaddy that at least 2" above level is smart thinking. If you drop it too low when planing you will find you boat getting on its nose and trying to dart one direction or the other. Loss of control can wreck your day, so go down slowly and feel wht it is doing, don't just run it down to some preset limit. Every time you load the boat differently it will act differently.
Just be careful with it and feel your way.
Scotty
Having said this I agree with BIgDaddy that at least 2" above level is smart thinking. If you drop it too low when planing you will find you boat getting on its nose and trying to dart one direction or the other. Loss of control can wreck your day, so go down slowly and feel wht it is doing, don't just run it down to some preset limit. Every time you load the boat differently it will act differently.
Just be careful with it and feel your way.
Scotty
cowboy
Moderator
I like the lenco small tabs.
I like to cut the trim plate from the hinge, and remove a 1.5 to 2" strip of length from the hinge area, then re-weld it to the hinge.
If I remember correctly, we wind up with about six inches from the hinge, to the actuator mount on the plate.
This increases the overall throw available by a huge amount.
This way I can have plenty of travel for a super high up position, and still have way more than enough down travel for trimming if needed.
This length from the factory just does not afford enough thow for a proper airboat application. It's plenty for a regular kicker boat, and that's what they designed them for.
This does effectively lower the mechanical advantage for the actuator, but they are designed for large boats, and are way overpowered for what an airboat requires anyway.
As Whitebear stated, caution should be used when trimming your airboat with a powered tab. Too much tab at high speeds could cause for a lot tighter turning, than will allow you to stay in your seat. Just give it enough down to stop the bounce, then back it off a bump. Then bump it back if needed.
Then of course, you'll have to tell yourself to pick it back up before you hit the dry.
I want my tabs UP when not deployed. WAY UP, if I'm gonna have one.
I like to cut the trim plate from the hinge, and remove a 1.5 to 2" strip of length from the hinge area, then re-weld it to the hinge.
If I remember correctly, we wind up with about six inches from the hinge, to the actuator mount on the plate.
This increases the overall throw available by a huge amount.
This way I can have plenty of travel for a super high up position, and still have way more than enough down travel for trimming if needed.
This length from the factory just does not afford enough thow for a proper airboat application. It's plenty for a regular kicker boat, and that's what they designed them for.
This does effectively lower the mechanical advantage for the actuator, but they are designed for large boats, and are way overpowered for what an airboat requires anyway.
As Whitebear stated, caution should be used when trimming your airboat with a powered tab. Too much tab at high speeds could cause for a lot tighter turning, than will allow you to stay in your seat. Just give it enough down to stop the bounce, then back it off a bump. Then bump it back if needed.
Then of course, you'll have to tell yourself to pick it back up before you hit the dry.
I want my tabs UP when not deployed. WAY UP, if I'm gonna have one.
cowboy
Moderator
They are infinately adjustable.
Changes in fuel loads, passengers, coolers, water or wind conditions.
If any of these things change, the fixed tuning of the hulls planning surface may cover it, or it may not.
Got some hulls here that have tabs, and some that do not.
Most of the time they don't even get used. They are there if they are needed though.
What you recommend does work, just not as well for anything or everything that may be encountered.
JMO
To each his own.
Changes in fuel loads, passengers, coolers, water or wind conditions.
If any of these things change, the fixed tuning of the hulls planning surface may cover it, or it may not.
Got some hulls here that have tabs, and some that do not.
Most of the time they don't even get used. They are there if they are needed though.
What you recommend does work, just not as well for anything or everything that may be encountered.
JMO
To each his own.
cowboy
Moderator
Naw man.
I'm not ruffled. If may post above sounded short, perhaps I just need more coffee. Besides, I'm sure the original poster welcomes your input here as I do.
I fully agree that if your into running the really rough stuff, having a tab of any sort on your boat could be a liabillity.
It could tear-up your boat, and stop your operating. I agree fully.
That why when we do put them on, I want massive throw for a way high stowed position, and willing to go through the extra hassle to modify for increased travel.
Peace!
Have a great day slider.
I'm not ruffled. If may post above sounded short, perhaps I just need more coffee. Besides, I'm sure the original poster welcomes your input here as I do.
I fully agree that if your into running the really rough stuff, having a tab of any sort on your boat could be a liabillity.
It could tear-up your boat, and stop your operating. I agree fully.
That why when we do put them on, I want massive throw for a way high stowed position, and willing to go through the extra hassle to modify for increased travel.
Peace!
Have a great day slider.
jdotson
Well-known member
In my particular situation I was able to remove my trim tab by tapping down the aluminum lip from the turn chine down to the start of the flat bottom on both sides of my Alumitech. It works well and the tapped down part is off the ground when running dry.
I did change the mounting location of the Lenco ram on the tab itself when I ran one. I moved it closer to the hinge to allow more travel and faster response.
I did change the mounting location of the Lenco ram on the tab itself when I ran one. I moved it closer to the hinge to allow more travel and faster response.
Have any of you guy's ever thought of putting a elevator tab between your rudders mounted at the top where they connect at the cage, I don't think it would have to be that big and let the air off the prop trim the boat instead of the water then it would be out of the way of damage from stumps and other things and it would be up high on your cage so it would have good up or down force.It works on an airplane so I don't know why it would not work on an Airboat
Sniper have seen those tabs used. I am not familiar with them as to how good they actually are but the fellow I talked to liked his. The one he had was made by a company called "BEAR" I belive and it was adjustable but not on the fly. I experimented with an adjustable design to allow the front or rear of the boat to be picked up using the airflow of the prop. It turned out to require significant mounting strength ... more than was available at the back of the cage. It also required some serious seat of the pants/hand coordination and speed to keep it all working right especially in deep water. i wanted for quicker takeoffs to keep the stern from going so deep and enabling a substantially quicker plane. I also thought it would be neat to use it to spin the boat around in a tight place by standing it on its nose or transom. I got the idea from being stuck in a floating mat and having the bow go under through the mat while at heavy acceleration and I thought WOW if I could just do that on purpose now I would have something LOL I did alright... an almost for sure awww poopy. But back to your question ... yep they work and they are out there most of them mount at the top of the rudders that I have seen in person and in picts
jdotson
Well-known member
The three rudders are more responsive and require less stick movement. There is a lot less resistance at the stick even when rudders are turned and engine is at full power such as when spinning around on dry ground. People that have driven my boat and are used to two rudders say the steering is sensitive and takes a little getting used to. I've been told it's like having power steering on an airboat. The three rudder design was the work of Paul Petit who used to make Nighthawk hulls/ P&R Specialty. Chances are the aluminum throttle petal on your airboat (and most others I've been around) says Petit Enterprise or something like that on the bottom side of the petal. He came up with those too.
IM WITH JDOTSON IVE HAD ALOT OF PALMBEACH HULLS THAT HOPPED BUT LIKE COWBOY SAID YOU COULD RE-ARANGE YOUR LOAD AND WEIGHT A LIL AND FIX IT SOMETIMES.. BUT A COUPLE YEARS AGO I BOUGHT A BRANDNEW HULL FROM DIAMONDBACK, I PUT MY BOAT TOGETHER AND 1ST TIME OUT IT HOPPED BAD, I WAS DISAPONTED TO SAY THE LEAST BEING BRANDNEW AND THE THOUGHT OF BUYING A TRIM TAB, I WENT TO LAKE CYPRESS THE NEXT WEEK AND CAME IN FROM RIDING AND A OLD BOY WITH A GTO WAS THERE AND TOLD ME HE NOTICED MY NEW BOAT HOPPING AND ASKED ME IF I WANTED HIM TO FIX IT.. I SAID YA I KNOW I NEED A TRIM TAB, HE SAID NA AND GRAPPED A 5LB SLEDGE FROM HIS TRUCK AND WENT TO THE BACK OF MY NEW BOAT , AND I SAID WOOOO THERE BROTHER WHAT YOU FIXING TO HIT ON MY BOAT WITH THAT THERE HAMMER? HE BEAT THE LIP DOWN FLAT ON THE BACK OF MY TRANSOM FLUSH WITH THE POLY AND TOLD ME TO GO OUT AND TRY IT NOW.. THAT DANG BOAT RODE FLAT AS GLASS, I COULDNT THANK HIM ENOUGH FOR THE TRICK AND SAVING ME THE MONEY ON THE TRIM TAB...