Skimmer Ratings- a discussion.

[luke33]

How are you measuring water?

Hook up a bag to the output of any skimmer or feed it to a bucket or any container and you can measure the water throughput. It generally takes two people though : ) You learn that quickly!

 

[Powerman]

Hook up a bag to the output of any skimmer or feed it to a bucket or any container and you can measure the water throughput. It generally takes two people though : ) You learn that quickly!

Ya I could see that. I always wondered how to do it without introducing any back pressure.

 

[Jon Warner]

Hi Jon

That was very well said.
I was wondering if we could get another opinion from you. It is probably the second most talked about in the subject of skimmers, and that is where should the cone transition start from. We here it should be full cone, the cone should start from the bubble plate, or a cone like the Super Marin is enough. Where do we draw the line on the benefits of the cone shape.

Thanks

Kevin

Ok, let me step carefully here :wink:

In the generation of molded cones, the cone skimmer is less expensive to build than a non-cone skimmer. The molded cone cost from a Chinese injection molder is about $10 (including tooling cost). The cost of 18" of 8" acrylic tube and a thermo-formed transition piece is more than $10 by the time you factor in the time to cut the acrylic tube, finish the cut and the time to bond the tube to the transition piece. The cone replaces the body and transition piece of a standard or SM type skimmer.

Is a full cone shape superior? Not so much. I, personally would prefer to see a cylindrical lower section and a tall transition piece starting 1-2" above the bubble plate. Why? The hybrid cone makes better use of the footprint, giving larger internal volume and a larger effective cone surface/volume per footprint. In addition, the larger lower section reduces the turbulence under the bubble plate because of the greater water volume and will produce fewer mb's. A hybrid cone body will also function with greater air flow than a similar full cone with equal footprint.

With automotive racing engines they always say, "There's no substitute for cubic inches" and there's no substitute for a skimmer's body volume.

You can compensate with dual overhead cams, turbocharging and such... but when you apply these same technologies to larger engines the smaller engine will never come out on top.

The larger body is great for skimmer designers... it let's us use a larger diameter bubble plate with a larger VBT drain, it allows for more LPH, of air AND water flow and the extra internal volume is great for increased capacity.

This is PROBABLY the same reasoning/logic why Klaus believes that the SM is superior to a full cone...

The 2010 WM skimmers use a "Hybrid" design... as we introduced last year as the "WM Elite" design.

Check out the sketch below, black outline is hybrid body, red outline is full cone body... equal footprints.

 

[Jon Warner]

A good example is the SWC 300A vs. SWC Askoll cone. The footprints are 19 x 12.5 and 18 x 15 (cyl vs. cone) and the 300A pulls 30% more air and has probably 50% more internal volume. I would rate a 300A for at least 30% more capacity than the SWC Askoll cone.

P.S. and I'm highly "skeptical" of those that have commented that the SWC Askoll cone outperforms the 300A... (noting that the 300A requires a larger, higher bio-load system)

 

[Troylee]

great write up jon....
i think what your saying atb has done with the inverted cone on bottom... it allows more water volume but it also gives you a smaller foot print because you can put the pump closer to the body....
the skimmers with the pumps inside the body are a waiste of valuable space imo. and it looks like yours also from reading your last 2 posts...
+1 also on the cones being cheaper..weather it comes from china or is hand rolled like i do them it is alot cheaper for a flat sheet of acrylic than it is to buy cast tubing...a 10" cast tube can run ya 200$ a foot all day long when i can make a cone with a 10" base for half that or less....

 

[Jon Warner]

great write up jon....
i think what your saying atb has done with the inverted cone on bottom... it allows more water volume but it also gives you a smaller foot print because you can put the pump closer to the body....
the skimmers with the pumps inside the body are a waiste of valuable space imo. and it looks like yours also from reading your last 2 posts...
+1 also on the cones being cheaper..weather it comes from china or is hand rolled like i do them it is alot cheaper for a flat sheet of acrylic than it is to buy cast tubing...a 10" cast tube can run ya 200$ a foot all day long when i can make a cone with a 10" base for half that or less....

all true... and the ATB DLX is a great design.

 

[luke33]

A good example is the SWC 300A vs. SWC Askoll cone. The footprints are 19 x 12.5 and 18 x 15 (cyl vs. cone) and the 300A pulls 30% more air and has probably 50% more internal volume. I would rate a 300A for at least 30% more capacity than the SWC Askoll cone.

P.S. and I'm highly "skeptical" of those that have commented that the SWC Askoll cone outperforms the 300A... (noting that the 300A requires a larger, higher bio-load system)

I guess you need to run them both and determine that yourself :bigsmile: as I'm one of those people you call "skeptical"

 

[Jon Warner]

I guess you need to run them both and determine that yourself :bigsmile: as I'm one of those people you call "skeptical"

that'd be a good test...here's the caveat. The test system must have an excess of organics because the 300A has a larger neck and more pump output. And that 160mm neck is HUGE! I wouldn't put it on anything smaller than 350g. On a smaller system or a system with lower organics, the smaller necked skimmer will always produce more.

 

[luke33]

It was on a 350g system fwiw. Sharks and rays

 

[ksed]

Jon

Points well made!
Although the full cone due to it's lower volume has the ability to inject more air at a lower wattage due to less back pressure.

 

[Troylee]

Jon

Points well made!
Although the full cone due to it's lower volume has the ability to inject more air at a lower wattage due to less back pressure.

Not always good thou... If you pound a cone with air and it has no contact time what good is it??? It's about balance and the smoothest trasition possible....more water volume is always a good thing....
And to be honest from some tests I have done a bubble plate hurts the performance of a pump also... I really think if you could balance a skimmer with no bubble plate and still pull the amount of air the skimmers today do it would truly reign king.... Bubble plates cause back pressure and result in a higher wattage from tests I have done besides taking up more valuable space inside the skimmer body... Currently I run the atb design with the dual bubble plate and it does have it's goods that out weighs the bads like increased wattage, it actually gives a super smooth transtion and keeps them bubbles trapped that much longer in the body.... With the current design I run the deluxe model the bubble plate is dead even with the base of the cone giving me a full cone body transtion and it works great...;)

 

[Powerman]

that'd be a good test...here's the caveat. The test system must have an excess of organics because the 300A has a larger neck and more pump output. And that 160mm neck is HUGE! I wouldn't put it on anything smaller than 350g. On a smaller system or a system with lower organics, the smaller necked skimmer will always produce more.

Awesome Jon, thanks.

So then that brings up an interesting question. You can't "over skim" a system. The skimmer will only pull what's there, you you can have improperly matched skimmer size to tank size. So if I go the ever popular "2 times tank size" then what will happen to my tank? What is the bigger skimmer not doing that a properly sized skimmer is?

If you do not like oversizing a skimmer, then what factor do you feel you can get away with and still have a well performing skimmer. 1.5 times, 1.25 times?

If... and only IF.... you know you will be moving up in size, and you buy a bigger skimmer to go on the future bigger tank.... what do you feel is the max size difference a skimmer can span? 1.5 times...2 times...3 times. Meaning going from a 90g to a 180g or a 270g tank. At what point is the skimmer pretty useless on the smaller tank and useless on the bigger tank?

So then what do you think Jon.

 

[Powerman]

Not always good thou... If you pound a cone with air and it has no contact time what good is it??? It's about balance and the smoothest trasition possible....more water volume is always a good thing....
And to be honest from some tests I have done a bubble plate hurts the performance of a pump also... I really think if you could balance a skimmer with no bubble plate and still pull the amount of air the skimmers today do it would truly reign king.... Bubble plates cause back pressure and result in a higher wattage from tests I have done besides taking up more valuable space inside the skimmer body... Currently I run the atb design with the dual bubble plate and it does have it's goods that out weighs the bads like increased wattage, it actually gives a super smooth transtion and keeps them bubbles trapped that much longer in the body.... With the current design I run the deluxe model the bubble plate is dead even with the base of the cone giving me a full cone body transtion and it works great...;)

I know Mojo has talked about making his bubble plates.... seems to be more to it that drilling holes. Make enough to not cause back pressure, make few enough, to actually redirect. The SWC X200 I was playing with I was suprised at how turbulent it was after the plate. The tangential flow didn't help. But after looking at the bubble plate it was nice and thick. If I owned it, I think I would have to try my hand at making one.

 

[Powerman]

So I wanted to see some sort of standardization of some sort of rating system.... but it does not appear that's going to happen, especially with the fact there is no standardized reference.

Great discussion though guys. I love this stuff, don't really care where it goes.....

So then let me ask this.... why is it cones are considered to have less back pressure? I have heard it a couple of times, yet a couple of times it has been referenced with volume, which has nothing to do with back pressure. The only difference I can come up with is due to the cones shape, the water above the pump is say 10" and the foam head is forced to be 15" in a 25" skimmer. And a cylinder has say 12" of water and 13" of foam. So the total weight of a inch column would be more, but restrictions, decreased diameter and increased velocities also add to resistance. Some body want to sort that out for me?

 

[mojo]

I am actualy geting ready to make another plate for mojo 2.9 I think.

 

[ksed]

Not always good thou... If you pound a cone with air and it has no contact time what good is it??? It's about balance and the smoothest trasition possible....more water volume is always a good thing....
And to be honest from some tests I have done a bubble plate hurts the performance of a pump also... I really think if you could balance a skimmer with no bubble plate and still pull the amount of air the skimmers today do it would truly reign king.... Bubble plates cause back pressure and result in a higher wattage from tests I have done besides taking up more valuable space inside the skimmer body... Currently I run the atb design with the dual bubble plate and it does have it's goods that out weighs the bads like increased wattage, it actually gives a super smooth transtion and keeps them bubbles trapped that much longer in the body.... With the current design I run the deluxe model the bubble plate is dead even with the base of the cone giving me a full cone body transtion and it works great...;)

What is interesting is the new deltec's bubble plate are open on the side's which I believe they did that because of the back pressure issue.That is one of the way's they are able to achieve those #'s on their skimmer's

 

[Troylee]

What is interesting is the new deltec's bubble plate are open on the side's which I believe they did that because of the back pressure issue.That is one of the way's they are able to achieve those #'s on their skimmer's

it is interesting but it's a little different than the traditional skimmers out rite now... For one it runs recirc and the bubble plate has 2 purposes one is pulling the water and air while the other acts as a diffuser.... Deltec makes a really nice product and they really perform but I'm a little skeptical on the numbers they claim I would like to really see someone take one and hook some meters up to and see if it really is what they claim.... :(

 

[ksed]

Another thing we should look at is the abilty of a skimmer to keep a foam head while feedings occur.
I noticed some skimmers will take longer to recover than others.
What would the cause of that be. (That some take longer than others). Body style eg cone or the the air to water ratio?

 

[mojo]

Another thing we should look at is the abilty of a skimmer to keep a foam head while feedings occur.
I noticed some skimmers will take longer to recover than others.
What would the cause of that be. (That some take longer than others). Body style eg cone or the the air to water ratio?

Yes all those. NEck size too. THe smaller neck will not need as many organics to start to form a head.

 

[luke33]

Yea, mostly neck diameter but alot of it is going to do with what your feeding. I don't think that has any thing to do with skimmer ratings though : )