Tuesday, September 04, 2012

Rocket status including a new, smaller air Honest John

The weather and my personal schedule have continued to delay the launch of my air-powered Saturn V.  So, this is what I've been up to instead.

I wanted to build one of the Honest Johns from the Mike Bauer plan pack.  It's MUCH smaller than my earlier HoJo builds (~18" v. 39") and I thought the outer body would work as a pressure tube on my 1" launcher.  However, I miscalculated and found it's just s skosh too small. Luckily, GIMP will load pdf's and from there they can be converted to graphics formats and edited. So, I converted the plans to png's and then tried scaling them.  Rescaling should be easy but for me it wasn't. First, the expanded version was clipped by the printer margins. I first tried printing without margins.  This only worked on some sheets plus my HP goes into snail mode (very slow).  Next, I split up and rearranged the parts, using 4 sheets v. 3. The body still had to be printed without margins but it worked fine. So far so good....but not for long.  I found the hard way that, when I resized the other pages, not only did the parts get resized but the page size did too.  This was subtle and it took me 3 print rounds to figure out what was happening.  Because the page was larger than the paper size, the graphics program automatically adjusted the six back down due to the 'fit to page size' option.  When this is de-seclected, the printed image suddenly became a thumbnail sized image so that was a no-go.  Once I figure this out, I trimmed the page to 8.5x11 and then things were OK.  Since the nose is expendable anyway, I chose to use/adapt some of my undersized copies rather than just trash them. The results are shown to the right. The kludged nose won't slide down far enough to make it scale, but who cares? If I don't, nobody will!

I also installed a 24mm mount in the carcas of the now much stubbier big HoJo.  A little glue and duct tape and it should be flyable.  Since MDRA has long set-off distances, it should be allowed to fly unless the wind is very unfavorable (i.e. would blow it over the crowd). Hopefully, it will get even shorter in a couple of weeks.

Finally, I built 'initiators' from my last few pre-cut twisted pair wires. I think I'm going to get a 30ga wire stripper and some loose wire rather than buy the pre-cut stuff.  For 29mm motors it really would be better to have longer wires anyway and 12" is the longest my supplier makes without a custom run.  I also double-dipped some Q2G2's and soldered on a pigtail to lengthen them.  If this works out, I may give up the wire-wrap igniters for 24/29mm motors.