Derimming a 20L - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 01-26-2011, 07:47 PM Thread Starter
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Derimming a 20L

Anyone have any good links for how-to derimm a 20L. Should I even attempt? I've read mixed reviews so far. I would leave the bottom intact.
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post #2 of 8 (permalink) Old 01-26-2011, 08:19 PM
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De-rimming a plastic rimmed tank is the same process whatever the size of the tank. It just takes a lot longer with bigger tanks. Whether or not you attempt it depends on how patient you are, how much time you want to spend, how mechanically inclined you are, and what you plan to use the tank for, plus how much margin of safety will be left after you remove the rim. That isn't the same for every tank.

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post #3 of 8 (permalink) Old 01-26-2011, 11:42 PM
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I for one would shy away from doing it in a 20L.
I derimmed an AGA 10gal and noticed bowing out of the glass when filled with water so what more would happen to a 20L?
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post #4 of 8 (permalink) Old 01-27-2011, 05:20 AM
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From what I can tell, at least on a 10gal is that even having the rim on does little to prevent bowing. I filled two 10 gallon tanks that I had with water to test this exact thing. One tank was one that I de-rimmed, the other had the rim intact. I took the measurements of both before and after they were filled with water, so I could see how much more the de-rimmed tank bowed than the rimmed one did.

The results surprised me in that the de-rimmed tank only bowed something like 1/8 " more than my rimmed tank. Granted, there must be variation in how much a tank bows based on the strength of the glass, construction, etc, but I was surprised to see that the difference was so minimal, even though it was a small tank.
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post #5 of 8 (permalink) Old 01-28-2011, 10:01 AM
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Quote:
Originally Posted by Armonious View Post
From what I can tell, at least on a 10gal is that even having the rim on does little to prevent bowing. I filled two 10 gallon tanks that I had with water to test this exact thing. One tank was one that I de-rimmed, the other had the rim intact. I took the measurements of both before and after they were filled with water, so I could see how much more the de-rimmed tank bowed than the rimmed one did.

The results surprised me in that the de-rimmed tank only bowed something like 1/8 " more than my rimmed tank. Granted, there must be variation in how much a tank bows based on the strength of the glass, construction, etc, but I was surprised to see that the difference was so minimal, even though it was a small tank.
Given the surface area covered by that clase, 1/8" is hardly minimal. Put it this way, measure the plate thickness of the glass on it. Now work out the percentage of deformation as compared to glass thickness. If it doesn't worry you, then you know nothing of engineering.

I'm not saying I think that plastic provides much, but if it's an 1/8th of an inch difference, it's providing way more than I thought it would. It's your home though, whatever.
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post #6 of 8 (permalink) Old 01-28-2011, 01:18 PM
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I agree. 1/8" is 4mm... that is a lot.


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post #7 of 8 (permalink) Old 01-28-2011, 01:58 PM
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I used a derimmed 20L (top and bottom) with no issues at all. I loved the look of it, that tank is really slick de-rimmed.

I had thread about it here, check it out, I think you will be more confident about de-rimming the tank after doing so.


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post #8 of 8 (permalink) Old 01-28-2011, 05:30 PM
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Quote:
Originally Posted by tharsis View Post
I used a derimmed 20L (top and bottom) with no issues at all. I loved the look of it, that tank is really slick de-rimmed.

I had thread about it here, check it out, I think you will be more confident about de-rimming the tank after doing so.
yes? and, how much deformation un-rimmed vs. rimmed.

Just because it worked for you doesn't mean it will for everyone.

Basically the reason you get away with it is because these tanks are designed with anywhere from 2:1 to 5:1 safety factor. Now what this means is that the overall design of the aquarium should be able to take 2 to 5 times the predicted stress. But predicted stresses are exactly that, predicted. The true stresses will vary depending on substrate height and weight, decoration weight, the water decorations displace, etc. Those rims keep the highest point of stress in the middle of the pannels.

When you de-rim a tank, you move the point of greatest stress on that panel in a difficult to predict way. You eat into that safety factor. IF it's 5:1, you're in tall cotton still, bowing be dammed. If it's built at 2:1, get a wet dry vac, you are going to need it.
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