Sunday, August 28, 2016

Glider mindsim FAIL

I added more and more stuff and all it theoretically needs is two elastic bands. What a kludge.

No hypothetical worries here. It is good and nose heavy. Tail weight helped. Didn't add more as it already needs repair. I really don't want to add a bunch of weight so I think I'll extend the area of the canard. It may still just be a throw toy for the grandrocketeers. Or a chew toy for my dog.


Friday, August 26, 2016

The pitfalls of real-time design (yet another photoless post)

Well, progress on the Chesapeake Air Monster is crawling along.  The good news is that the motor mount flips like is s'posed to. The rest isn't as good.

I added the motor mount tubes and began thinking about adding a thrust point for each motor. Currently, the thrust point is only a bit over a quarter of an inch. No bueno. I cut some wood triangles out of some scrap wood. They should work but they sure look weird (as if the whole build isn't kinda weird). Back to the drawing board.

Then I roughed out to support posts for the back of the motors. I will need about an inch of tape thrust ring. I considered the motor mount plate, but hadn't considered the clearance required for the motor tubes. D'OH! At least they will not be super ugly and the long thrust ring shouldn't hurt anything.

I added some popsicle stick supports at the attachment points for the elastic (note to self...but some thin stuff) and some extra chunks of foam board to get the 1/4" lugs to line up.

Today's worries: 1) Will it glide as is; 2) If the nose is too heavy, will weight on the tail counteract that or should I add more area to the canard?; and, 3) How melted is the stabilizer going to get? Maybe I'll add some metal duct tape to the leading edge.

Old school rocket trackers

Rocket Hunting Dogs

Thursday, August 25, 2016

New day, new name, new issues

Last night I decided on a name for the foam ekrano-glider: Chesapeake Sky Monster.

I also decided on two 24mm mounts. I just wasn't feeling the joy for another large cluster and this will allow for the use of the legendary E9s. Two tubes were cut and are being plugged so the spent motors can hail down over the field.

The solution to the deployment issue presented itself 50ms after I last hit 'post'. I'll fashion two supports that will hold the motor mount up when motors are loaded. When they eject, the mount will be pulled up.

My latest worry is transferring all the thrust to the two tabs on the supports seen in the previous photo that I posted. I think this will be strong enough but, because they are at the centerline, I worry that any off-center thrust will wrench the motor mount apart.  I started adding some extras supports with some high-tech tongue depressors. I really need to additional tabs further out from the centerline. I'm considering a thrust plate between the two motors which will also mate with the existing tabs.

Foam, squishy balsa and popsicle sticks, what could go wrong?

Wednesday, August 24, 2016

Foam ekrano-glider progress

Progress on the foam Chesapeake Sea Monster was delayed by a long weekend getaway (which also caused me to miss both August launches). I still hadn't figured out the entire motor mount/flipping canard design. So, I just started cutting wood anyway.

Here is a photo of the mount dry fit in the deployed position.  It will be pulled up by elastic bands attached to either the side wings or the rear wing. Both should keep the elastic away from the exhaust plumes.  The part I have not figured out is how to keep it in place during boost. One way is to have the motors hang out the front with a bracket to hold them down. But, will a motor eject itself if it is merely touching a flat plate? Maybe I need to have the motors' rear overhang mate with a bracket?

I also can't decide on the motor configuration. I'm torn between eight 18mm and two 24mm. Since I'm running low on Q2G2's, I think I want to reduce the number.

Finally, I wanted to limit the weight of the motor mount parts so I went with a slab of squishy balsa. I'm not worried about the boost but an unsure what will happen if the canard deploys at high speed.

One the original Chesapeake Sea Monster, I was worried about stability. Now I'm worried about everything else.


Tuesday, August 23, 2016

Building tips from Chris Michielsson

Apogee's latest newsletter has some great tips on: adapting a 3/16" lug for a 1/8" rod; improved use of wadding; hiding sticker/decal junctions/overlap; thinning down your tri-fold shock cord mounts; masking tape removal; tying a better shock cord knot; and, cleaning paint over-spray.

I'll steal his thunder and give a hint on the last one - use a Mr. Clean magic Eraser. I very lightly scrape the overspray with a hobby knife blade but will have to try this one out!

If you don't already do so, check out Chris' great blog.

Smoke by the water, a fire in the sky.

In Case You Missed It...

Tuesday, August 16, 2016

"Is that X-15 Model Really the Right Color?"

Dean Black has written a paper discussing the true color of the X-15s, why it is that color and how to make your model's color true to scale. It's a .pdf and not hosted anywhere so I'll provide a teaser. He had given permission to distribute it so if you leave an email in the comment section, I will send it to ya'.
Is that X-15 Model Really the Right Color?  
Is the X-15 really black? The short answer is “No”. For a variety of reasons X-15 appears black in most photographs, but outdoors in direct sunlight X-15 is an iridescent dark blue. That’s right, blue, or more specifically “gunmetal blue”.   ....