here is my questions and responses from Wednesday13.
hello,
I was wondering if you could offer me some advice on bonding acrylic for a 300 gallon tank I am building? I saw your post about using weldon 40 and was impressed with your knowledge. I would really appreciate some advice.
1. do you think weldon 40 will cause crazing on 3/4 acrylic?
2. how would I go about bonding two sheets of acrylic together with 40? making use of two full sheets I wanted to glue two 8' by 18" pieces together to make the bottom of the tank. simply apply and clamp with moderate pressure?
3. lastly, I am concerned that the weight of an 8 foot long by 30 tall piece of 3/4 would be too heavy and actually squeeze all the 40 out of the joint. is this valid? should I brush it on thinly on both sides of the joint, let it go to work and then lower it into place?
thanks in advance for any advice. it seems these trade secrets are heavily guarded but I assure you I am just a hobbyist trying to build a nice tank for myself. I have a good job
Brian
#40 should be fine on new 3/4" material...it crazes more when used on old material and 1/2" or less... the 3/4" can take a bit of heat no prob as the glue cures.
2. For butt joining sheets...lay them out flat on a surface spaced 1/8-1/4" apart. tape the underside of the seam/void as well as the front and back edges. Inject the #40 into the gap avoiding bubbles and as ur laying the glue down follow ur trail/bead of glue with more tape to seal it all in. packing tape works well as u can see through it..its hard to remove afterwards tho. the purpose of the tape is to keep the glue where u want it and also to avoid shrinkage in the joint. sealing it all off will lessen the shrinking during cure process.
no need for clamps or any pressure. to achieve a clear seam...and in ur case to make the bottom piece flush/level again ull need to sand down the excess glue after it cures for 72hrs. normal type woodworking tools work the same on acrylic. orbital sanders leave the least amount of scratches as well as by hand.
3. As for assembling the rest of the tank with #40 u almost need to do one piece at a time. and u may need to sand/finish after each step also. The weight of the material shouldnt push out all the glue. you can attempt to brush it on but ull just make a mess. #40 is a 2 part epoxy with a 10-30min pot life. u have to work quickly. plan out ur steps before u mix and pretty much pour the glue you need right out of a mixing cup or squeeze type bottle before it starts heating up. 1st glue your front to the two side pieces with the front piece laying flat and the side going upwards. let that dry for 24-48hrs...flip it over and glue the sides to the bottom piece, bottom piece should be placed down flat first. 3rd. glue ur entire bottom permitter on...and lastly glue ur top piece on. i recommend a full top sheet brace with holes cut/routered out. "eurobracing" is not for acrylic tanks.
The whole assembly is not so much a trade secret... its a very long and labor intensive process which is why not many people take the time to learn to do it. Glueing is one art in itself...and Finishing/buffing/sanding is another. #40 cures very hard and can even be machined. its not easy to sand down so even "clean up" on anything you spill will require sanding down to remove...then back up through all the grits and polishes to clear or flush for other glueing.
Off hand i can say ull need a decent table saw, router/bits, oribital sander, sanding block, grits, polishes, mixing containers, squeeze bottles, scale or measuring devices that can be reused/thrown away, good respirator, ventilation (i do not recommend using indoors) and plenty rags/shop towels. Not a bad idea to practice on scrap material first either. #40 is fairly expensive to work/test with...but i wouldnt go diving right into full assembly without mixing a cple batches of glue and practicing gettin bubbleless seams while also keeping the pieces of acrylic where you want them. youll have to tape everything together as you go abd make jigs to help you hold things together while you glue.
You can also solvent weld 3/4" material with #3 or #4 using the pin method...its a bit easier and cheaper process. I do not recommend the use of weld on #16 for anything tho. its for hobbyists/arts and crafts. all #16 is, is #4 with pieces of acrylic melted into the solvent to thicken it. the added acrylic makes it weak and brittle. it also cures with bubbles
