Monday, August 13, 2012

24mm Paper Honest John, part 3

Today, I continued building the nose cone by adding the lower sections. The third section (larger-to-smaller diameter) went on well but I hit a snag with the lowest section (straight tube section marked with 'US'). Since I had installed a lower bulk plate, I couldn't make sure the tabs were flush against the inside of the section above it (duh). As a result, it sagged a bit while I wasn't supervising.   I had to pry it apart and ended up adding an inside cardstock tube that extended from the bulkhead to about 1" above it. So, while I managed to get these parts secured together, the joint was still a bit ugly. There wasn't much to do so I added some of vinyl pin striping to break up the mismatched lines. Here it is all stacked together but less the canards. (By now you see that my descriptions are more to tell you what not to do rather than to claim I know what I'm doing!)

To strengthen the upper part of the body tube, I ended up sectioning a section of 3" tubing and making a tube as I often do to make couplers. This tube is sturdier than a wrap of cardstock and forced the body to a round shape.  I also made the nose section's shoulder using this technique. (Shown to the right.)

When I added the canards, I found that they didn't sit flush against the cone's surface.  It suddenly struck me why this happened.  When I bent the tabs, the paper thickness and bend radius raised the fin roots.  Next time, I'll try to account for this spacing. Note, that bending the tabs out was my modification and not part of Mike's instructions.

When I loaded an E9 motor, stuffed in a 24" 'chute and installed the nose, I found the HoJo should be stable.  Whew! The bad news is that an E9 would require a 60" rod! So, this will fly on either a D12-3 or an E12-4.

After this round of glue dries, all that's left is the launch luck and shock cord. I'm adding a 3/16" lug to a fin root and will carefully bore a hole through the cone.  Finally, I'll run a piece of MicroMaxx body tube from hole-to-hole. Should be ready for MDRA this weekend...fingers crossed for good weather!