Venturi Drain Question

7 years 4 weeks ago #23023 by Newbflat
Replied by Newbflat on topic Venturi Drain Question
Yep, that's exactly how the ventury should be and not how mine is. Glad stellar did the right thing for you. Shame they couldn't to the right thing for me. I'm not sure they deserve any special praise for doing what the should though.. But they definitly deserve critisum for what they didn't do. In my case, not delivering the boat they promised and that I payed for, and not fixing the ishues.

FENN Bluefin S
FENN Swordfish S carbon hybrid
Epic V8 double gen 2
Lot and lots of DK rudders.


Had:
Stellar SEL excel (gen 2)
Stellar SR excel (gen2)
Stellar S18s g1 (excel)
Epic V10 Double (performance)
Stellar SR (gen 1)
V10 sport (gen 2)
V10 (Gen 2)
Beater SEL (gen 1)

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7 years 4 weeks ago #23025 by Kayaker Greg
Replied by Kayaker Greg on topic Venturi Drain Question
Hmmm, I still think the bullet should go inside the venturi a little more but that's an improvement on where it was.

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7 years 3 weeks ago - 7 years 3 weeks ago #23042 by Kocho
Replied by Kocho on topic Venturi Drain Question
In my test the shape, size, and placement were all important. While I didn't experiment with all possible combinations, the simple rig I did allowed me to almost immediately see the effects of the bullet's position and shape. It turned out for me a bullet that was flat on the front and spaced away from the cone worked better than an oval bullet inside the cone.

I've posted this before:


I have also bought a pair of the small size 3D printed sets mentioned here (through Oskar, shipped to the US), but I have not yet installed them, so can't comment on their performance (I don't doubt they will work well). I like the small size for flat water use - less drag than the big/dual setup and still should drain at slower speeds than the original bullet in my Think Eze, which is what I'm after.

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7 years 3 weeks ago - 7 years 3 weeks ago #23049 by red_pepper
Replied by red_pepper on topic Venturi Drain Question
Nice test setup - very similar to a wind tunnel! I like it when you can obtain solid empirical data instead of relying on guesswork and theory. I could see where the flat-fronted bullet would work well spaced a short distance from the cone, in terms of smoothing the flow around the bailer, but I wonder if the flat front would impact the flow of water coming through the bailer?

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7 years 3 weeks ago - 7 years 3 weeks ago #23050 by Kocho
Replied by Kocho on topic Venturi Drain Question
Yup, made quick work of experimenting with a few different shapes, sizes, and positions. Of course, there are many non-controlled variables such as does the air behaves like water and what speed of the blown air would be most representative... Still, the version of the bullet that worked better in my air test indeed worked better on the water too, so there is at least some degree of correlation :)

Oh, and yes, I was asking myself the same questions about the flat front of the bullet not being as hydrodynamic to the draining water as a more round shape would be. It probably isn't, so a smooth protrusion inside the cover would probably work even better. But it might not - what if the sharp edge actually creates a higher local velocity for the water, thus increasing suction? I don't remember if I tried a small bullet with a round front or not, but the small bullet with the flat front worked better than the larger bullet with a round front... Anyway, lots of guess work in my setup too. And, while shaping different bullets from pink construction foam is very easy, it still takes a few minutes for each one, so it becomes tedious after you make a few...

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7 years 3 weeks ago #23055 by red_pepper
Replied by red_pepper on topic Venturi Drain Question
I could see where the flat-fronted bullet might create a "dead zone" ahead of the flat with increased suction around the edges. At any, you have a very cool set up and you've given us some great information. Thanks!

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