These pictures and description below from Henry show the relatively simple tools used to make a fin that wraps the full diameter of the tube.
Thanks to Henry for sending in these pictures.
After reading many diy solar water heating articles on the net I attempted to built my first panel. I noticed that most constructors used the half or partially wrap method to shape the fin material around the riser. When I planned the third panel it was decided to go for full wrap as it just makes more engineering sense to wrap fully than partially. The outcome of the process was of greater importance to me than the process (no of steps) itself. I did not bother to look for refinements because it was a once off project (I hope). For those home panel constructors who are familiar with the half wrap method knows that fin shaping can be accomplished in one process. The full wrap however involves more steps, unless one constructs a device that does it all in one action. Unfortunately I am not that dexterous so please bear with me through this process. I will welcome and consider all suggestions to enhance it. The fin material is 1 mm aluminum roof flashing which comes in 600 mm wide roles, cut to size and pop riveted together after completion of the fin shaping and soldering processes.
More fin area is required to accomplish a full wrap and in order achieve this I secured a 6 mm square steel spacer underneath a ˝”stainless steel rod. It is advisable to use a steel rod instead of copper tubing. All the fins are shaped before proceeding to the next step.
Next the ˝” copper tube is dropped into the “U” shaped curvature of the fin and placed into the jig and squeezed until the wrap is completed. At this point the two sides will point upwards.
The two ends are now dressed back, and if need be, the jig may be turned up finally to secure a near perfect wrap.
The final result is a neat fit around the copper pipe.
Full wrap fin compared to regular fin
Pounding the deep groove into the tube.
My 2 cents -- maybe worth less:
- The method does get full contact with the copper tube, and this should improve performance.
- It seems like quite a bit of work. If one were going to make a lot of fins using this method, it might be worth working to make the forming tools a bit faster and more durable?
- You would want to be careful to not wrap the aluminum around so far that the aluminum touches on the bottom and prevents the fin from being pushed into full and tight contact with the tube.
Gary Feb 21, 2010