Mountains of sawdust (360g plywood, LED, Arduino build)

[der_wille_zur_macht]

So, recent progress. I got the bracing on. The bracing was 4" wide strips of the same plywood I used for the tank, laminated to double thickness. So, 4" x 1.5" bracing. Once it was on and the glue cured, I spent an hour or two cleaning up the tank and prepping for epoxy. I scraped out any glue drips or squeezout, sanded a bit to knock down sharp edges, swept the tank out, and vacuumed it to remove dust.

Scraping the glue:

I did most of the above-listed prep work from inside the tank. It's really the only way to reach the whole thing easily. It's still up on the workbench, so I just climb in through the front opening dukes-of-hazzard style.

I then took a break:

Oh no, I left my drink waaaay down there at the other end of the tank!

Then I unpacked the epoxy and gathered my tools:

That's 7.5 gallons of epoxy, some mixing cups, plastic spatulas, pigment (for the final layers), dosing pumps, etc.

I mixed and poured the bottom panel. I'm aiming for a little over 1/8" thickness total, and three pours per panel. So this first pour is a third of the total volume for the bottom:

I haven't used "real" epoxy like this in a few years. I've forgotten how much I like the smell.

The next week or two is going to be a pour every 12 - 16 hours or so, so that each layer goes down before the prior layer is completely cured, for a good chemical bond. Also, no sanding between layers will be required this way. I'll post some more photos as I do more pouring.

 

[der_wille_zur_macht]

PS - after pouring and spreading the epoxy, I wanted to make sure there were no bare patches or big bubbles. The work table is pushed up close enough to a wall that I can't really get behind it on a ladder to look down in to the tank, so I just climbed up on top of the tank and walked around the bracing. That bracing is STRONG. I could jump and push on it all I wanted with NO detectable flex. I have no doubt it'll hold the tank together.

 

[H20ENG]

A good rattle from underneath with a couple of dead blow hammers will ensure you are bubble free I use this high tech method when casting concrete countertops.

I thought about using my air chisel with a hammer bit, or using an old sawzall blade with the tip bent over to rattle out the bubbles. Low tech works, plus you get a workout!

 

[EdSnyder]

What's the "special effects" ??!!

What?? Did I miss something?

 

[der_wille_zur_macht]

A good rattle from underneath with a couple of dead blow hammers will ensure you are bubble free I use this high tech method when casting concrete countertops.

I thought about using my air chisel with a hammer bit, or using an old sawzall blade with the tip bent over to rattle out the bubbles. Low tech works, plus you get a workout!

I use the "smack it around" technique. Mix the epoxy, then smack the cup to encourage mixed-in bubbles to pop. Then pour and spread carefully, then shake (or in this case, pick up half an inch and drop) to float the bubbles up, then inspect the surface and smack them with a spatula to pop them.

In the end, since I'm pouring at least three layers on each side, even if a couple survive, it shouldn't matter. Unless the odds are REALLY against me and bubbles in each layer all line up.

 

[salty joe]

If epoxy acts like paint, the tiniest residue of silicone will cause just that.


Why not pour the epoxy in one thick coat? There are not a great deal of fumes to get locked in and create blisters, are there?


Looking really good.

 

[kcress]

What am I missing? No fiber glass! What gives?

 

[der_wille_zur_macht]

Why not pour the epoxy in one thick coat? There are not a great deal of fumes to get locked in and create blisters, are there?

No worries about fumes, but the stuff gets pretty loaded with bubbles as you're mixing/pouring it. If you poured in one thick coat and a big bubble went un-noticed, it could pop late in curing and leave a big void right down to the wood. Not good. Even a pinhole-sized void would cause a slow leak, soaking the wood and causing the tank to fail.

What am I missing? No fiber glass! What gives?

Not strictly required. In a thin composite, it adds stiffness and toughness (i.e. abrasion/penetration resistance.) In this build, the stiffness is there from the wood, and the toughness is there thanks to the epoxy being 1/8"+ thick. Epoxy on it's own is really weak, but with the wood substrate it just needs to provide waterproofness and protection. Cloth is hard to get pinhole-free, so even if I used it, I'd want a thick layer of plain epoxy on top anyways (see: gel coats on glass boats).

I mentioned earlier in the thread that I have some composites background, from classes back in college (probably forgotten that part anyways) and other hobbies (airplanes, boats, cars.) This method strikes me as unconventional and risky from that background, but it's been proven pretty thoroughly with many multi-year-old builds in my local area (see: fingerlakesreef plywood forum.) I've known those folks for many years and they swear up and down by this method, even though it's a bit different from traditional composites methods AND traditional wood tank methods. So, I bought in to it. Figured I could always sand it back out and add glass if I thought it was a problem once the tank was built. But, seeing how insanely stiff a box made from 3/4" hardwood ply is (especially with the doubled-up lip) I have no worries. I was literally standing on the lip above the front opening jumping up and down yesterday, it was rock solid.

 

[kcress]

OK, thanks!

 

[H20ENG]

Do you plan on putting down a "prime" coat of thinned epoxy to let it soak into the wood first? Sometimes the epoxy is thick enough and sets up before it can really soak into the wood. I thought that if I ever build another woody, that is the way to go.

Raaden built some frag vats and had some delamination. Extra insurance to get it into the wood pores, IMO.


Oh, and I believe the special effects referred to are of your lighting system. I read that too back a couple pages....

 

[der_wille_zur_macht]

This is some of the thinnest epoxy I've ever used, and it soaked into the wood pretty significantly. I tried to pay attention to that during the initial pour of the bottom, and it looked OK. IME surface prep can make a difference there (getting dust out of the pores, etc.) in addition to using the right product. Besides being thin, this epoxy is V-E-R-Y S-L-O-W. The pot time is like 45 minutes, and cure is like 48+ hours at the temp I'm using it. It's setting in around 12 hours, so I can do two coats a day, but it'll still have plenty of time to soak in. And it doesn't blush! I've never used this brand before but I really like it so far.

 

[H20ENG]

Awesome! Pour on then

 

[der_wille_zur_macht]

Regarding the special effects with the lighting - I'm going to wait 'till it's finished to post finer details, if at all. Someone's already taken one of the "cool" LED ideas I posted and claimed it as their own on another forum. I don't mind people copying what I do, but at least I'd like a shout out.

 

[H20ENG]

I just used one of these Had to make my own heatsink, but it really makes for "Sexy Parties" (Stewie Griffin)

http://www.haywardnet.com/inground/products/lighting/ColorLogic-4-LED-Pool-Lights.cfm

 

[der_wille_zur_macht]

Oooohhhh. . . .Ahhhhhhhh. . . . .

 

[der_wille_zur_macht]

And the last pour for the bottom panel:

Yes, it's white. I know black and dark blue are probably the standard choices, but the inside of my tank will be white.

Here it is spread:

And, just so people don't think I've abandoned the sump, here it is, too. I'm pouring each panel in the sump at the same time as the main tank:

 

[MrineLfRlz]

its coming along nicely
keep the updates coming

 

[PapaKlix]

this is all really cool and a nice thorough pictorial. just curious, why did you make the sump out of plywood when you said yourself that the cost is probably the same as buying a glass/acrylic tank at that size?

 

[der_wille_zur_macht]

this is all really cool and a nice thorough pictorial. just curious, why did you make the sump out of plywood when you said yourself that the cost is probably the same as buying a glass/acrylic tank at that size?

Couple reasons:

1) I essentially had most of the material. The wood was scraps or cutouts from the main tank - I needed three full sheets to do the main tank, but there would have been a ton of leftovers. And it's not gonna use that much epoxy, and no glass. By virtue of standard packaging, I had the biscuits, glue, and screws, too. So I guess I lied, because it's gonna be cheaper for me, though it would be more expensive if you were starting from scratch.
2) Practice - the sump is my "warmup" for each new phase in the process (cutting the wood, prepping, joining, pouring epoxy, etc.) This way, if I somehow mess something up the first time, I don't destroy the display tank. Though, I'm essentially on the last step that they'll share (pouring epoxy) and I haven't messed anything up yet.

 

[username in use]

Coming along great. How come you chose white? Nothing against it, just wondering why. It might be a lot of work to keep it looking clean.