Water pickup drag testing

[kfxguy]

I'm one of those kind of people that like to find out things first hand rather than believe everything I read. There's many things I've read and tested for myself to find out what I read simply wasn't true or entirely accurate. So in the quest for more speed I decided to test different water pickup types on a couple different boats I have. One will be my zelos and the other will be my Rivercat. I'm not starting the testing until this weekend as I'd like some feedback on what you guys think and if you think what I have planned will be accurate enough. First one in testing is my zelos with bottom pickups. What I plan is getting a baseline run. One nice long full pass. Then I'll use some ultra thin packing tape to block off the pickups and make another pass. That should tell me the difference don't you think?

Next my Rivercat. Baseline with a rudder pickup. Then block it off. Then I'll try a prop wash pickup. I devised a setup last night that will allow me to add one quickly so I can do it at the lake for more accurate results. What do you guys think?

[RandyatBBY]

I do not think you will see mush difference. But it is always a good idea to test theories.

[kfxguy]

I do not think you will see mush difference. But it is always a good idea to test theories.

I agree but the things I've read you'd think it was a huge difference.

[785boats]

I vote the propwash pickup will have the most drag.

[dmitry100]

Top SAW's (142mph+) in Germany do not use our standard "raindrop" water pickups -- they instead use plain small 3mm holes but with the assist of water pumps. Would not doubt if a water pump would help with the drag in general. Scooping up water like a rain drop style pickup would technically create drag right... but how much drag exactly? Just like using a thinner knife wedge for rudder can create a couple more mph... that's the sort of difference it would probably be but it adds up at end of day.

[kfxguy]

Top SAW's (142mph+) in Germany do not use our standard "raindrop" water pickups -- they instead use plain small 3mm holes but with the assist of water pumps. Would not doubt if a water pump would help with the drag in general. Scooping up water like a rain drop style pickup would technically create drag right... but how much drag exactly?

I'm going to find out

[Turbo Dan-O]

[NativePaul]

I am interested to hear the results of the tests.

While not perfect, I think taping up the hull bottom pick up will be a good enough test.

I suspect the vast majority of the drag from a rudder pick up comes from the thicker blade rather than from the pick up itself, do you have a thinner wedge the same size that you can swap it with?

Can you t ry both behind the prop, and above the prop pickups, I think there will be a big disparity between the two.

[dmitry100]

kfxguy: If you want to give it a shot with good pump-- I can give you a link to a good one. Cheap too.

[Mxkid261]

Curious to see what you find, I put sponson pickups in my rivercat this past weekend after I fixed the front seam

[785boats]

I think the lowest drag water pickup system is the raindrop pickup with a reversed raindrop outlet. The water rushing past the outlet (on the left of the picture) sucks the water out by creating negative pressure in the line, thus negating the positive pressure drag, on the pickup. Well, to some extent at least.
You just can't see if the system is blocked or not while the boat is running. Very common in Europe.

[RandyatBBY]

Ya lets see info on all three. Ya know placement of the j-tube makes a lot of difference too for oval racing I try to get a little closer to the hub and SAW's it is out and higher. I was weighing S-15 props to day, every little thing adds up.

[kfxguy]

I think the lowest drag water pickup system is the raindrop pickup with a reversed raindrop outlet. The water rushing past the outlet (on the left of the picture) sucks the water out by creating negative pressure in the line, thus negating the positive pressure drag, on the pickup.
You just can't see if the system is blocked or not while the boat is running. Very common in Europe.

Holy damnit. That's a good idea. Thanks for that! I've seen the gundert ones but I like this much better. My builds are now going to change a bit. I guarantee that's the least drag setup there.

[kfxguy]

Ya lets see info on all three. Ya know placement of the j-tube makes a lot of difference too for oval racing I try to get a little closer to the hub and SAW's it is out and higher. I was weighing S-15 props to day, every little thing adds up.

I'll be able to do the bottom pickup test this weekend. Probably be next week before I can do the prop wash vs rudder pickup. I really need to set a boat up that has all of them.

[Hotrods]