Motor swap ?

[dtacmed]

I have a Leopard 4082 2000 kv I was thinking about putting it in a new Proboat Ul-19 Seeing that the stock is a 2000 kv how much difference would there be ? advantages / disadvantages ?

Thanks

[CraigP]

It will accelerate much faster! That motor should weigh a lot more than the stock motor, might have to re-check the CG. I'm not sure if there is a 0.150" flex or 3/16 in there stock. If it's the smaller, you'll get more flex windup. Might be close to the line on that... Sounds like fun!

[dtacmed]

It.s a 0.150 flex. I have been running that motor in a BJ-29 V3 with no problems it has a 0.150 shaft also but the UL-19 shaft is longer.

[CraigP]

It's probably fine David... but I would make sure she's not tail heavy. Maybe you have some latitude to move the batteries forward to compensate. You can also throw some negative angle on the strut and drop it by 0.10" too. Main thing is, the weight shift will make a difference. I would work with weight and leave the strut alone...

[dtacmed]

It's probably fine David... but I would make sure she's not tail heavy. Maybe you have some latitude to move the batteries forward to compensate. You can also throw some negative angle on the strut and drop it by 0.10" too. Main thing is, the weight shift will make a difference. I would work with weight and leave the strut alone...

Thank you that was one of my concerns. Not sure if the weight difference will be worth the change. Kind of limited concerning weight shift without adding weight.

[CraigP]

Well, if it flips or airs out, then you'll know. You could just try a lifter prop on it too. All kinds of things! It's up to you...

[Fluid]

The only advantages of the much larger motor with the same Kv include the ability to spin a larger prop. A larger/higher pitch may give the boat more speed. The larger mass will handle heat a bit better.

Some disadvantages include considerably more weight, CG thrown off, higher amp draw with the larger prop, possible poor handling with the bigger prop, added amp draw could damage ESC, shorter run times. Most can be compensated for if you are inclined.

If speed is what the OP is after he would probably be better off selling the Leopard and getting a 40x75 motor with a Kv between 2200 and 2400. Same prop, higher speed, reduced balance issues.


.

[dtacmed]

Thanks for the replies Ran it with the Leopard this evening was not good. As Fluid stated balance was way off and it handled very poorly. Back to the stock setup for now.

[dtacmed]

The only advantages of the much larger motor with the same Kv include the ability to spin a larger prop. A larger/higher pitch may give the boat more speed. The larger mass will handle heat a bit better.

Some disadvantages include considerably more weight, CG thrown off, higher amp draw with the larger prop, possible poor handling with the bigger prop, added amp draw could damage ESC, shorter run times. Most can be compensated for if you are inclined.

If speed is what the OP is after he would probably be better off selling the Leopard and getting a 40x75 motor with a Kv between 2200 and 2400. Same prop, higher speed, reduced balance issues.


.

Would a 40x74 2200 suffice with stock prop ? Thank You !

[CraigP]

OP, that's why I recommended you check CG stock then after the motor swap... Weight makes a huge difference! From here, you just need to run it and decide on subtle changes. If you get a vid, we might be able to offer some suggestions, but we really need to see how the boat moves on the water. And yes, 4074 2200kv is a much more reasonable step up. Even with that, CG must be set right, it is very important on a hydro!

[dtacmed]

OP, that's why I recommended you check CG stock then after the motor swap... Weight makes a huge difference! From here, you just need to run it and decide on subtle changes. If you get a vid, we might be able to offer some suggestions, but we really need to see how the boat moves on the water. And yes, 4074 2200kv is a much more reasonable step up. Even with that, CG must be set right, it is very important on a hydro!

Thanks I have found that out real quick. Obviously Hydros take a little more time to set up than Cats, Tunnels or V's. Time to learn something new. Gonna stay with the stock setup until I figure this thing out.

[CraigP]

Hydros, both full bodied and rigger, use principles of both hydrodynamics and aerodynamics. It takes a while to figure out which one is actually effecting the ride negatively, and how you go about fixing it. The UL-19 is a very light boat, so it will fly in rougher water and wind. I would put it back to stock and tweak on the strut, both lowering it and raising it, with no angle on the prop (neutral). Just see what it does. Make sure to mark your strut for the stock position, I use an Exacto blade to put a line scribe along the bottom side of the mounting bracket into the strut, to make an easy reference point. The stock position for this hull, is the exact distance that the back of the sponsons measure to the bottom of the boat. Generally, making the strut deeper, or increasing the distance from the centerline of the prop shaft to the bottom of the hull (at the transom) will make the boat run wetter on the sponsons. It will also make the boat a bit more stable in rough water or wind. Many racers tweak their struts at the races for the type of water they are running on. Just the opposite, raising the strut, or reducing the distance to the bottom of the hull will make the boat lighter on the front end and fly easier.

Now, the other tweak... Only do this after you get a good sense for the strut up/down adjustment. Adjusting the angle that the strut sits in its bracket either clockwise or counter-clockwise, as you view it from the side, will do the following:

1) Clockwise - This is known as positive angle. You are aiming the back of the prop up in the air. This makes the back of the boat drive lower and tends to make the front of the boat run more free. This is done in very small amounts, like 1/2 - 1-1/2 degree.
2) Counterclockwise - This is known as negative angle. You are aiming the back of the prop down in the water. This drives the stern up and pushes the nose down. As in #1, this is done in very small movements.

Then there are different propellers. There are "lifter" props, they have a high degree of rake on them and they tend to lift the back like #2. So you can see, many things to tweak to get a boat to ride right. There are setups for course racing and there are SAW setups for each hull.

And we haven't even touched rudder/turn fin adjustments! Have fun with this and learn. Sure beats a freaking video game, eh?

[dtacmed]

Hydros, both full bodied and rigger, use principles of both hydrodynamics and aerodynamics. It takes a while to figure out which one is actually effecting the ride negatively, and how you go about fixing it. The UL-19 is a very light boat, so it will fly in rougher water and wind. I would put it back to stock and tweak on the strut, both lowering it and raising it, with no angle on the prop (neutral). Just see what it does. Make sure to mark your strut for the stock position, I use an Exacto blade to put a line scribe along the bottom side of the mounting bracket into the strut, to make an easy reference point. The stock position for this hull, is the exact distance that the back of the sponsons measure to the bottom of the boat. Generally, making the strut deeper, or increasing the distance from the centerline of the prop shaft to the bottom of the hull (at the transom) will make the boat run wetter on the sponsons. It will also make the boat a bit more stable in rough water or wind. Many racers tweak their struts at the races for the type of water they are running on. Just the opposite, raising the strut, or reducing the distance to the bottom of the hull will make the boat lighter on the front end and fly easier.

Now, the other tweak... Only do this after you get a good sense for the strut up/down adjustment. Adjusting the angle that the strut sits in its bracket either clockwise or counter-clockwise, as you view it from the side, will do the following:

1) Clockwise - This is known as positive angle. You are aiming the back of the prop up in the air. This makes the back of the boat drive lower and tends to make the front of the boat run more free. This is done in very small amounts, like 1/2 - 1-1/2 degree.
2) Counterclockwise - This is known as negative angle. You are aiming the back of the prop down in the water. This drives the stern up and pushes the nose down. As in #1, this is done in very small movements.

Then there are different propellers. There are "lifter" props, they have a high degree of rake on them and they tend to lift the back like #2. So you can see, many things to tweak to get a boat to ride right. There are setups for course racing and there are SAW setups for each hull.

And we haven't even touched rudder/turn fin adjustments! Have fun with this and learn. Sure beats a freaking video game, eh?

Thank You that helps a lot. Every bit of information is greatly appreciated. Definitely beats a video game. I have a 2yo , 5yo and 12 year old grandsons. They all have boats and love heading to the lake or pond.

[CraigP]

That's what it's all about!