Adjustable airboat engine trim?

[Daddy Dave]

OK. Waterthunder, Marshmaster and our other resident experts.....a question.

Every other type of motor vessel has an engine trim as an intregal part of basic equipmet. Why not airboats? Would seem to offer great boat performance impact.

Old Volvo stearndrive units had a hydraulic engine trim with a 3" travel that attached to the front motor mount. Rear mounts allowed for slight travel. The engine was set at mid point and slight movement plus or minus was at the push of a switch. Performance was significantly effected.

 

[Anonymous]

I was thinking about this too after AirAg's post the other day.

Maybe some air shocks at the back of the stand and a small battery op. compressor.

You wouldn't need much adjustment would you?

 

[marshmaster pat]

Big Daddy - That is a question I and a few people have wondered about over here. Originally thought hydraulics, but then have to have a pump. A good electric ram (or pair) should work, but we are not the caliber of welder that would be needed to do major stand modifications. Don't want an engine coming lose.

For running tall marsh grass, especially bulrush and cane, getting the nose to climb slightly would probably help. Then adjust when you hit the water for cruising, and readjust for running into the wind, with the wind, or a sprint of speed.

It would have to be a strong setup, due to the thrust and torque. But it seems possible.

 

[Daddy Dave]

MARSHMASTER, THE OLD VOLVO-PENTA / OMC I /O ENGINE TRIM SYSTEM PLACED THE SHORT RAM UNDER THE CENTER POINT OF THE FRONT ENGINE MOUNT. BET THERE ARE A FEW IN MARINE SKELETON YARDS.

Your theory is my theory. Could potentiall allow for dramatic performance changes based on the running surface.

 

[Gbenzx]

BigDad,

Discovered your Airmachine last nite while treading the gallery = one word AWESOME & 720 no less.

Fwiw, I would opt for a small elevator or Horizontal Stabilizer between the rudders for this purpose. It could be configured also for adjustment on the move via cable & twist knob at the pilots station & need no motor or hydraulic assist.

Just a thought, Gben

 

[Waterthunder]

I mounted some Bimba air cylinders on a motor a few years back. But you know 90% of airboaters only care about weight I think my whole system weighed around 26lbs. I ran two air cylinders on the front motor mounts and a small air compressor to run the system. I used a two way ram that utilized air on both sides to lift and lower the motor. I did it for racing purposes and found out that the race is far to short to have time to utilize it. The coolest thing I found was that the air rams cushioned out vibrations and gave a smoother ride. It was fun to play with just like my clutch gear box boat was.

 

[Daddy Dave]

Waterthunder,

I use a Mercury Marine power trim pump to activate the trim tab on my son's airboat. It works great and weighs next to nothing. I imagine your race boat is extremely fast - but, most airboating is done at very moderate speeds and over long distances.
Differing engine trim might make over the ground capabilities better - same as it does on my flats boat. I trim the engine lower unit away from the transom to raise the bow up to go skinny and pull it toward the transom to lower the bow down for rough waters. Total trim ram throw is about 5" in my 225 Mercury.

 

[dean]

I saw a home made airboat with a rudder mounted horizontal above the vertical rudders. He used a windsheild wiper moter with all thread to adjust the upper rudder. Seem like a good idea but we didnt get to see the boat run as it was having power problems. If we see him again I will get some pics

 

[Anonymous]

This is a good topic. I have a trim tab on my boat and it works fine but it does effect the way the boat handles and I have been know to forget to raise while running dry. I have been thinking about a horzontal rudder for trim tab for some time. I wonder how wide (front to back) it needs to be.