Methods to 'trim' an airboat at speed...

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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glades cat
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Re: Methods to 'trim' an airboat at speed...

Postby glades cat » Wed Oct 05, 2011 5:28 pm

Remember the gyro effect of moving a rotating mass.
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Re: Methods to 'trim' an airboat at speed...

Postby yobee » Wed Oct 05, 2011 5:29 pm

Get a good hull set up right and you won't need any of it. However yes, there has been adjustable engine stands built. You wouldn't need a lot of travel, an inch up and down would be plentiful.
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Re: Methods to 'trim' an airboat at speed...

Postby yobee » Wed Oct 05, 2011 5:47 pm

gyrocopter582 wrote:It just seems like
the ability to 'adjust' the thrust angle to meet changing conditions of the water,
and boat loading would be beneficial.

While we are on the subject, is there a golden rule, or defined angle of the prop
face, or engine centerline, that everyone uses?
I will be building my own engine stand, and I am thinking ahead.
Thanks, Mike.


Airboats ride on TOP of the water and are designed to run in shallow water. I have never encountered any conditions that I would wish to change the engine angle that would be beneficial to the performance of my boat. The same goes for loading.
An engine stand, centered and leveled with the stringers is pretty much as good as it gets, assuming the hull is good. Weight distribution is a different topic as far as engine stands go.

Just my 2 cents, but I don't know sh!t anyways my boat is all blown up lol.
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Re: Methods to 'trim' an airboat at speed...

Postby pirate » Wed Oct 05, 2011 5:52 pm

Is it easier to raise or lower a complete engine or raise or lower a trim tab?
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Re: Methods to 'trim' an airboat at speed...

Postby JAMES » Wed Oct 05, 2011 6:07 pm

i do think u can set a hull not to pourpous but since i was a kid ive always heard if it dont pourpous it dont truley RUN FREE and i seem to think that i mean if u always hugged to the water with no jumpping at all then that could be true ..
if your at crusie say dd/ac at 1700 and your jumping that might no be bad and u might can tweak some stuff so it will help out until deeper waters or higher rpms ect .....

but if u wanna try to get it right b4 a trim tab try that balance thing ask yobee he will tell u how i have no clue my self id put a damn trim tab and be done with it my self :lol: but my new boat wont have one i dont wanna drill the holes in it :roll:
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Re: Methods to 'trim' an airboat at speed...

Postby yobee » Wed Oct 05, 2011 6:09 pm

Engine trim adjustments at those speeds on an airboat will send you flying... possibly on a one way trip to meet your maker lol!! Trim tabs are typically used for boats that carry a load a lot, and don't ride right without the load (ETC.) or boats that are real close to being dialed in, they may hop at higher speeds but not lower speeds, etc etc. A boat set up PERFECT will run any speed with or without passengers without hopping, and that same boat will run well on dry ground as well. Keep in mind every boat is different and ever person that drives a boat will want something different out of their boat than the next guy.

I believe "Zoom Zoom" on this website has an adjustable engine stand, if you try searching for posts by him you may find some info about it. Very cool stuff, but in MY OPINION, not necessary. It might be the best thing ever in your opinion and that's part of what makes airboating so cool, different strokes for different folks. Hope to meet ya one day and maybe show ya a couple boats of different styles.
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Re: Methods to 'trim' an airboat at speed...

Postby Striker543 » Wed Oct 05, 2011 6:18 pm

gyrocopter582 wrote:Yobee, I see your point. I may be overthinking this. My experience with my outboard
speed boat may be overlapping. With the outboard, the prop had a direct 'link' with
the water, and the smallest trim change at speeds approaching triple digits had a HUGE
effect on the handling. OK, so the engine centerline should be parallel to the boat bottom.
Thanks, Mike



I have both airboated and run center console boats my whole life - accept that they are two completely different things and you will make it easier on yourself. One of the only similarities between the two is the constant maintenance.

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Re: Methods to 'trim' an airboat at speed...

Postby Wild Bill » Wed Oct 05, 2011 6:32 pm

here's pics of Zoom Zooms. I figured with all the reading on SA I have done regarding running dry best if the hull porpoises and other opinions that they run dry on certain material if they ride on the nose and varying load conditions and such that engine trim wouldn't be such a bad idea. Zoom Zoom's here looks REAL simple. I have 2 poly bushings one of each that will be mounted at the Rotator mount holes and a electric linear actuator very similar to a Lenco trim tab mounted at the front of the engine. Weel see.. . Image

Image

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Re: Methods to 'trim' an airboat at speed...

Postby todd glover » Wed Oct 05, 2011 7:05 pm

stick with a trim tab if you need it the other would weight more be more complex to build and if done wrong could kill you

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Re: Methods to 'trim' an airboat at speed...

Postby RickMc » Wed Oct 05, 2011 8:49 pm

Has anyone ever thought of putting a driver adjustable eleveator in the airstream . Mabe use a lever with notches like a mower deck . Just another thought.
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Re: Methods to 'trim' an airboat at speed...

Postby JAMES » Wed Oct 05, 2011 10:38 pm

RickMc wrote:Has anyone ever thought of putting a driver adjustable eleveator in the airstream . Mabe use a lever with notches like a mower deck . Just another thought.

proley not cause u only use maybe a 1/8 at a time up or down people use a fender washer for reference
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Re: Methods to 'trim' an airboat at speed...

Postby mascara » Wed Oct 05, 2011 11:20 pm

My experience with centre consoles in the saltwater enviroment and not just calm waters has it that we need to
continually adjust the trim tab + outboard engine to get a smooth ride which is not easy, you do either the engine or the trim tab and not together.

To do the adjustment on a huge engine on a 18' AB on the move would be very dangerous given the shallow draft and the speed it can achieve.

I think an adjustable trim tab with the control mounted on the stick would still be safer.

JMO, from a newbie, still formulating my AB. :alien:

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Re: Methods to 'trim' an airboat at speed...

Postby Wild Bill » Wed Oct 05, 2011 11:21 pm

elevator been done, canard been done. Search SA. Not saying for sure I'm going to build an adjustable but I might. To have enough down thrust you could pull most of the weight off the stern or enough up thrust you could pull most of the weight off the bow. I wonder if the first guy that though up tilt on a stern drive or outboard had this much negativity? I think it would be cool; to try a ground effect boat.
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Re: Methods to 'trim' an airboat at speed...

Postby Whitebear » Thu Oct 06, 2011 1:27 am

I remember Bear Airboats used to sell the elevator wings for the back. It was a fad but sure didn't last long. They even had one with a crank to be adjustable. The non adjustable ones were only useful at one exact prop speed and at only one hull speed. The folks I spoke with said they weren't very effective. Their adjustable model was said to be better but you had to adjust it near as often as ha had to move the rudder stick. If they were a useful accessory they would still be around and in vogue. I see just one here and there. Maybe 2 in the last two years. I think some racers back years ago got hurt with them too.
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Re: Methods to 'trim' an airboat at speed...

Postby mrfixit » Thu Oct 06, 2011 7:10 am

most if not all race boats do not have the engine pointing straight forward or center of haul right - left . they are offset to counter act torque eather by moving the engine to the left and or pointing the engine towards the left front corner of the boat. this helps with torque roll.
Yes I have seen a few play with wings or spoilers both on front and back to eather keep the boat in or out of the water depending on what they were trying to acheave.

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Re: Methods to 'trim' an airboat at speed...

Postby GIMAMMOTH » Thu Oct 06, 2011 7:55 am

real boats dont need trim tabs..
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Re: Methods to 'trim' an airboat at speed...

Postby ZoomZoom » Thu Oct 06, 2011 9:51 am

Mike, I'm Bud C. aka Zoom Zoom if you PM me I will be glad to help you. I have used this system on 6 differant hulls with no problems, in fact, if you are sitting in the front seat you will not even know when I'm changing pitch angle. I do know about gyroscopic effect, and its' not noticable on any of the boats I have put it on, (I believe it is due to the change angle is slow). The motor moves thru a 3" arc at the rear of the engine, all thou I don't need that much. Mike I also will be on the St. J on Sat. I'll will be putting in on SR 50 around 1 PM.

Thanks, Zoom

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Re: Methods to 'trim' an airboat at speed...

Postby tkendall82 » Thu Oct 06, 2011 10:54 am

The best method is to level the boat front to back and set the engine between a half of a degree to one degree higher in the back with a digital level.


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