Acrylic fabrication questions? I can help! - Page 14

masterswimmer · #**326** 09/11/2005, 09:31 PM

Why don't you just use nylon screws to join the bracing piece with the 90 deg. angle piece instead of weldon? It'll drill easily, the nylon screws won't rust and I think you might get a better result. JMO

Russ

AQUAN8TOR · #**327** 09/11/2005, 09:42 PM

Nylon screws give nowhere near the strength and flex tolerance that actually gluing the pieces together would. JMO as well. Also, nylon tends to get pretty brittle when in contact with saltwater for long periods of time, IME. Knurled head screws on skimmers are one thing, but underwater, or where they will be exposed to salt spray, screw heads break off if they are old....

Spuds725 · #**328** 09/12/2005, 09:20 AM

Quote:

Originally posted by Bowman
I was concerned for a couple reasons one of which is the depth of the tank 24" top to bottom. The other is the fact that you are using flat sheet stock cut into strips to fabricate your top tank frame. When those plastic framesare made, they are made in one piece and you have structural integrity throughout the whole frame. When you use flat stock to make dimensional shapes you are relying on the glue joint for structural reliablity so the more surface area for the bonding the lesser chance of glue joint joint failure. Your going to make a significant investment in your tank, due you really want to cheap out for the few bucks it would cost. Also if you talk to your supplier they may have some shorts or scrap you could get for reduced price or even free and only have to buy your 72" pieces. HTH John

But I'm cheap

Of course you make perfect sense-- my question is more of the strength of the acrylic and joints as I'd never worked with building any joints and if doing it the way I described would work or not.

I'm not even sure if its needed or not as I don't know if the tank "bows" when filled-- If it does bow and the "joints" fail I think I would be in worse shape as the tank seams would be shockloaded by the glass bowing quickly then slowly like when it is filled--

I was and am exploring alternatives but your plan sounds like the most sound and safest.

If I go this way, I will likely put 3 cross braces across the middle section and between where my MH lights would be and on each out side of where the MH lights would be (5 total) in addition to the ones at the end-- does that sound like it will be strong enough??

This will be my last question on structure-- thanks for the help btw.

Spuds

Randall_James · #**329** 09/12/2005, 11:28 AM

Quote:

Originally posted by AQUAN8TOR
I appreciate the response, Zeph. I was kindof thinking the same thing about the bonding. I'm more than a little afraid that I'm going to end up squishing out too much glue, even if beveling the joint edge.

I thought the solvents were simply there to melt the stock and pretty much evaporated away. The weld-on 4 leaves no residue

AQUAN8TOR · #**330** 09/12/2005, 09:57 PM

Right; They don't leave residue, but they change the surface of the acrylic. What I was talking about was squishing out too much of the Weld-On 40, which isn't a solvent, but an acrylic epoxy.

keefsama2003 · #**331** 09/13/2005, 08:54 AM

whats a good buffing kit/process i have a few spots on the front of my 300 and i tried to get them out using this kit i got from an lfs but it seemed to make it worse.

someone said to get a buffing pad and rouge to get the whole front buffed but im not sure.

can anyone help me here please i dont want to wreck anymore than i seem to have done well not wreck but its just not as clear as it could be.

the tank is empty right now also. and my lights havent arrived yet

AQUAN8TOR · #**332** 09/13/2005, 09:02 AM

I use a fabric buffing wheel and NOVUS polish---red and green bottles. The blue bottle is just a cleaner & helps shine "".

keefsama2003 · #**333** 09/13/2005, 09:38 AM

and the buffing wheel is that like something used on cars?
im going to google it now.

SUMMERS · #**334** 09/13/2005, 09:43 AM

https://www.micro-surface.com/default.cfm?page_id=1

keefsama2003 · #**335** 09/13/2005, 09:52 AM

summers does it matter which one i get?

keefsama2003 · #**336** 09/13/2005, 09:58 AM

anyone else care to post links or let me know what they use? i really dont want to do anymore harm than done already even tho its not bad. there is like a scuff mark i wasnt able to get rid of i think mostly because i did too large an area at 1 time. i got the scratch i was aiming for out but there is a hue to where i was working and its not completely clear.

SUMMERS · #**337** 09/13/2005, 09:53 PM

These are the popular choices:

https://www.micro-surface.com/defaul...page_id=175#29

https://www.micro-surface.com/defaul...page_id=175#17

keefsama2003 · #**338** 09/14/2005, 07:31 AM

ok so those are all hand sand ones. i know there is a trick to doing this. should i wet the acrylic as im sanding it some? do i just take a small spot and sand it and then try to match the whole area or can i re-sand the whole area and hope to get the whole scuff/haze out of the front. i havent dont this before and was trying to follow the instructions to the T on the kit i got but it took the deep scratch out but now i have a haze/scuff kind of look and its not completely clear. im trying to figure out how to clear the haze out.

Acrylics · #**339** 09/14/2005, 11:58 AM

AQUAN8TOR,

Sorry for the late response - just been swamped.

Check your material to make sure it isn't AR coated as WO40/42 nor solvent will penetrate it. Banks commonly use the AR material in BR applications.

I would ask that you revisit the idea of using some bracing on the top of your tank, CYRO's thickness calculator is invalid (in my *personal* opinion) regarding tanks with no top. I have built tanks such as these specifically for the chief tech rep from Cyro, had him visit my shop and concede there are flaws in their formula but will not change it. For tanks without tops, the formula (according to me) should read 2.5x normal thickness rather than 1.5X to achieve similar deflection rates.

As for joint strength with 40/42; it would be a rare occurance than 2800psi is ever reached in a hobbyist aquarium - ever. 2800psi is the rating for solvent bonded joints (using WO4 IIRC) and roughly 4200psi for WO 40/42 joints (non-annealed 7 day joint), the problem with this is simple - it does not take the material being glued into account. Differences in various brands and various batches of acrylic (cell cast or not) can & will have vastly different physical properties, more specifically - molecular chain length which, for our purposes, is the material's ability to handle stress. There exists an inverse relationship between this stress handling property and solubility which is required for acrylic solvents and resins (such as 40/42) to "bite" into the acrylic. WO 40/42 do need to bite into the acrylic, they don't just stick to it as a glue.
One of the nicest things about solvents is you know immediately whether the joint is strong. With 40/42 - you can't tell until you actually stress the joint. I've seen more than a few tanks that had beautiful "cast" joints that literally fell apart upon first fill that used #40. While the "bond" intself *may* have been very strong - this has little to do with how well the agent sticks to the acrylic. WO 40/42 can yield perfect looking joints in stainless steel - will this yield a strong joint? nope. While this may border on hyperbole, it's just to demontrate that bond strength and actual joint strength are two totally different things.

This much said, WO 40/42 are great things but IMO take much practice to work with and the material used has to be of highest quality and consistency.

Personally, I use solvents for everything up to about 2.5" as I have the capability of machining material accurately up to this point. After that, cutters flex too much to get the accuracy and consistency needed. It is at this point where #40/42 becomes fantastic products. Casting sheets together in series such as bullnose tanks and extra long panels are other great situations for these resins but are usually done in shops very familiar with working with thicker materials.

I'll stop rambling for now

James

AQUAN8TOR · #**340** 09/14/2005, 02:12 PM

Hmm.....I get 1.44 using the 2.5x normal thickness value instead of 1.5x Do you think that I could get away with it if I use triangular 3/4" corner piece bracing?? ----putting a piece of acrylic 3/4" on a side in each side joint to strengthen it??

AQUAN8TOR · #**341** 09/14/2005, 02:14 PM

Oh, and THANKYOU!!!!!! I'm leaning towards Weld-on 4 for this project. Any difference between #3 & #4 as far as joint strength?? I know that #4 hazes less, but I'm an ignoramus as to which is stronger.....

Also, I don't really know what to look for as far as the AR coating; I'm assuming AR is anti-reflective?? Would sanding the area first or taking off 1/64" with a router table fence setup take it off if it is coated??

Acrylics · #**342** 09/15/2005, 09:09 AM

It's not the joint strength which is at issue (IMHO), it's the deflection tolerance. 1.25" will hole well but will bow over time once it absorbs it's share of moisture (roughly 1-2%) which takes about 12-14 weeks. The eurobrace really helps to alleviate this bowing, the corner gussets will help the joint from splitting due the stress caused by the deflection but will not change the deflection itself.
There is little difference in joint strength between #3 & #4, the major difference is "working time". #3 is very fast and does not flow well esp in thicker materials, for this - I'd suggest slowing the solvent down a little and making it flow better by adding a small % of acetic acid. You'll get a better looking and clearer and inherently stronger joint this way. The only diff between #3 & #4 is the ratio of MC (methylene chloride) and TCE (trichloroethylene). #4 has more TCE to slow it down. #5 uses acetic acid for the same purposes which is better IMHO but can produce a "grainy" looking joint if too much is used.
"AR" is short for "abrasion resistant" it's essentially a micro thin silica coating which resists minor abrasions and grafiti. If it is AR coated, it can be removed by either sanding the areas to be glued or machined off.
Also be aware that cutting BR acrylic is different than cutting "normal" acrylic. BR has a slight amount of (essentially) rubber in the resin to give it elasticity on impact from projectiles. So, it can be a trick to cut and extra sharp blades ought to be used to prevent melting & binding.

James

AQUAN8TOR · #**343** 09/15/2005, 01:27 PM

Thanks, James. I just bought a Freud plexi/plastic blade----expensive!!! Lots of little squiggly lines & J shaped cutouts in it.

I hate eurobracing; I know, I know...... I just don't like losing the ability to reach things in the tank. Also, I'm cheap, err on a very tight budget. I really don't want to do this, but if I must, I must. Would 3/8" be enough, or should I go for 1/2"?? Thankyou for all your input.

herefishyfishy2 · #**344** 09/19/2005, 11:23 AM

James..........would you mind looking at my thread here: http://archive.reefcentral.com/forum...hreadid=672070 and making a recomendation?

jozak78 · #**345** 09/24/2005, 08:50 PM

i've been looking through this thread for a few hours today and there is just a massive amount of information and i'm sure the answer to my questions are somewhere, but i figured i'd just ask since it seems that there are a lot of very helpful and knowledgeable people posting, so to my point i'm considering building a tank somewhere between 72Wide x 48Tall x 24Deep and 96Wide x 48Tall x 48Deep, and i'd like to know what thickness of acrylic I'd need and a good place to find it or at least some ideas. I've used a commercial calculator, but it's been suggested that the thicknesses it recommends are extreme overkill.

I already know the basics of acrylic construction, and that i need to get some practice before i attempt something of this magitude.

I appreciate any help

thanks
zach

kurty · #**346** 09/27/2005, 01:11 AM

Anybody knows about this method

"Construction Method â€“ We DO NOT use capillary cementing on our
tanks as this is NOT recommended for aquariums!! Some fabricators
use capillary cementing to save time and money and charge less -
Ask yourself this: is a few hundred gallons of water on your floor
worth saving a few dollars? We employ a two part Polymerization
method which is not only stronger but creates a virtually invisible
bubble free seam that lasts forever! Remember, our aquariums are
guaranteed for LIFE."

kgross · #**347** 09/27/2005, 01:35 AM

Kurty,

The method you listed is discussed in this thread, just look for any talks on Weldon 40/42. You will find that most experts say that the 40/42 is not as strong as a correctly "glued" seam with a capillary solvent. But please read through this thread for more info.

Kim

kimche' · #**348** 09/27/2005, 12:43 PM

All I know is I DIP and let either #3 or #4 SOAK in for between 1-2 minutes.

Bubble-free, welded edges every time.

AQUAN8TOR · #**349** 09/28/2005, 06:09 AM

jozak78, here's the only commercial calculator I know of. http://cyro.custhelp.com/cgi-bin/cyr...dWFyaXVt&p_li= James and others here have suggested that the thicknesses it suggests are definitely NOT overkill, and maybe could be INCREASED slightly. If you are making a tank 48" deep, then you are going to need some THICK acrylic. Something like 2". I know someone who had a tank made by a commercial acrylic manufacturer that probably everyone here has heard of that is made of 1.5" acrylic, and bows visibly, with a water depth of 44 inches. If you look along the length of this aquarium, it is kind of scary. These thicknesses are NOT overkill. I'm no engineer, but water pressure forces go up at a non-linear rate when increasing depth in an aquarium; the deeper the tank is, the much thicker the material you need will have to be.....

Acrylics · #**350** 09/28/2005, 10:43 AM

Jozak,

IMHO, the thickness required is largely dependent on two factors; A) deflection tolerance and B) bracing tolerance. The tank you have in mind can be done with 1.25" if you can handle a little bowing and a good amount of bracing, by "a little" bowing - I mean 1/4" or so. If this is too much, then you just move up in thickness. By "a good amount of bracing" - I mean one crossbrace (6-8") for every 2' of tank length and 4" perimeter flange. This would yield ~16 x 16" access openings nit accounting for any overflows. The depth you have in mind (24") makes this size tank kinda tough as the required bracing cuts down on the size of the top openings unless you use thicker acrylic.

Kurty,

What they are referring to in that statement is commonly called a "cast" joint. It has it's pros & cons both for mfrs and end users.
The main benefit can be stronger joint strength if, *only if* the resin gets a good "bite" into the acrylic and it (entire tank) is annealed in an oven for a week. The "bite" into acrylic (actual joint strength) is only absolutely known on water testing and without the annealing - the joint strength is comparable to a good solvent welded joint. The issue at hand insofar as joint strength is that you tank will *never* have more than 2800psi of force on any joint at any time so the point is rather moot IMHO. Capillary cementing is just fine for most aquaria and there is only one acrylic mfr that I know of that recommends against it and that is simply because they believe most fabricators cannot machine their materials precisely enough to allow for it, cast joints allow for more "slop" in the machining of the acrylic. In either case (solvent or cast), if done correctly - the joints are only rarely the first thing to go in a tank and in these cases it is usually because the mfr used inferior materials to begin with. The first thing to go is usually a crack in the top in the corner of an access opening or overflow and this has nothing to do with method of mfr but in design and engineering.

HTH?

James