Additional Water Pickup Question

[jakevisser10]

So I installed an additional water pickup on my revolt between the left turn fin and trim tab. I thought that putting it between the trim tab and strut would lead to more prop slippage. The way I look at it, it is either prop slippage or more drag...any insight?

[kfxguy]

Can you post some pics of it?

[jakevisser10]

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[kfxguy]

Are you having any problems? What exactly is the purpose or point of your question?

[jakevisser10]

If the spot I installed it is ok. I always see people install it between the trim tab and strut, which I feel would lead to more prop slippage. The place I put it will have more drag, but not increase slippage. At least that is my though process behind this.


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[lt130th]

Fundamentally, the worst shape of an object in a fluid flow is a circular cross-section/sphere, concerning drag. The turbulence from flow separation at the trailing edge is the problem. Thus, dragging a pipe behind the boat is probably the worst type of water pickup you can have.

flowcyl.jpg

https://www.grc.nasa.gov/www/K-12/airplane/dragsphere.html

That turbulence could affect your prop's performance by introducing dirty flow to a fraction of the flow across the area of the propeller disk. Take what you will from that. I do not claim to be a specialist in fluid dynamics or the study of boundary layer phenomenon.

[jakevisser10]

What would you recommend without having to drill through the hull?


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[boilo56]

I think most people place that kind of pick-up near the strut because that spot is always in the water, so the water flow is more constant. But there might be some other reasons.

[jakevisser10]

Yeah I completely get that, but I feel like it would lead to a lot of slippage


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[boilo56]

Mine is at this spot, and didn't noticed much change on the boat. But i'm not a racer, only a mad scientist!!!

[lt130th]

What would you recommend without having to drill through the hull?

Dual pickup rudder? Honestly I think the effects will be negligible. Your pickup will probably work fine where it's at as far as performance goes. These RC boats are not crafted with aerospace precision.

[boilo56]

Mine is at this spot, and didn't noticed much change on the boat. But i'm not a racer, only a mad scientist!!! Only the beveled part of the pick-up should see the water. here is mine:IMG_20150530_233656.jpgIMG_20150530_233817.jpg

[jakevisser10]

im only going to be sport running this boat, so the speed doesnt really matter that much, its more of a question of whether or not it will affect the handling.

[boilo56]

im only going to be sport running this boat, so the speed doesnt really matter that much, its more of a question of whether or not it will affect the handling.

No, It shouldn't affect the handling.

[lt130th]

...its more of a question of whether or not it will affect the handling.

Physics says you're creating a torque about a point/axis by the drag force acting over the length of the moment arm. But that's what you have rudder trim for, in this case.