It was a cold and damp weekend. As we've been spoiled with above average temps lately, I just didn't feel like removing subfloor in the cold. The plastic welder I'd ordered arrived a few days earlier, so I couldn't resist the urge to stay indoors and put it to use.
---------------------------------------------------
As I'd mentioned in the February 13, 2011 log entry, the quotes I'd received for fabricating a replacement black water tank were unreasonable. I decided to order a Steinel HL2010E heat gun with reducer and speed weld tips. I also found a great local plastic supplier that was very eager and willing to supply me with various types of plastics and weld rods at prices considerably cheaper than the cheapest source I'd found on the internet. What makes the situation even better is that they are located less than 5 miles from my residence. So, I picked up a 0.25" x 4' x 8' sheet of HDPE and a 0.125" x 4' x 4' sheet of ABS, and appropriate weld rod. The plan is to teach myself to plastic weld.
Steinel makes a nice product. The temperature is selected and displayed via an LCD on the back of the unit.
HDPE is a finicky plastic. Some sources recommend using nitrogen as a cover gas when welding HDPE (hot gas welding as opposed to hot air welding). I've found that the welds produced by hot air welding are very strong, provided the edges are beveled, the weld area is scuffed thoroughly with an abrasive (sanding disc), and cleaned with acetone. Your hands and weld rod must also be contaminant free. I've also found that the best weld temp is 570 degrees Fahrenheit. Finally, a soldering iron comes in handy for tacking the pieces together prior to welding, and is much quicker than switching back and forth between tacking and welding tips.
A word of caution....Plastic expands considerably more than metal when heated, so one must be prepared to deal with warpage as the weld cools.
For me, the free hand welding technique produces a far stronger weld than welding with the speed tip. However, free hand welding is slow....10 seconds for each inch of weld. A pair of 2" x 2" inch coupons of HDPE corner welded on one side only was able to support my full body weight (190 lbs) without failure.
White HDPE is very hard to photograph clearly. The weld below was produced with the speed tip. I'd love to use the speed tip, but cannot yet consistently achieve strong welds. I'm content with free hand welding HDPE if I can get consistent results.
I've put down close to 20' of weld today. Based on the results, I'm convinced that fabricating a replacement tank is well within my capabilities. It's fairly easy once the technique is acquired.
I've not tried to weld ABS yet, but will get the opportunity as I am going to attempt to repair the existing ABS black water tank as well.
I wrapped up the evening by cutting a few of the pieces for the top portion of the tank, and will start welding them together the next free evening I have.
That's all for today.