Sunday morning launch...

The Longshots begin unpacking their equipment for practice (Click to enlarge).

The weather was practically perfect this past weekend - not only did I get rockets built (Centuri Stellar Starlifter), primed (Sniple), and painted (Mach 10, Estes KL-3 Marauder), but I also got to fly a couple during the Longshots' TARC practice on Sunday. Duane and I showed up at Pegasus Field around 10 AM, whereupon I started to set up the low power pad and Duane began grilling his finals-bound team. It is good to have the "benevolent dictator" back in the States; things were kinda quiet at Pegasus without him. Having been gone for 5 weeks, Duane had a lot to catch up on, and the Longshots were eager to show what they had done in his absence. I was happy to see a green and white backup rocket next to the red and white "Phantom Flier" on the prep table - always a good idea to have a backup at the TARC finals. The Longshots made two flights, striving to hit an altitude of 775 feet. The first, involving the green and white rocket, clawed its way to 717 feet, but the trusty Phantom Flier missed the mark by only 4 feet, reaching 771 feet. Pretty good, but they need to work on their durations a bit in the wind - their time on the second flight was way long (56 seconds).

Patrick inspects "Sign Here Please" (Click to enlarge).

 We were joined on the field by Patrick, a new member of HARA. Patrick brought with him a scratch orange and white rocket, "Sign Here Please". "Sign Here Please" featured 3D printed fins, nose cone and motor mount; it would make two flights on Sunday, both on Estes F15 motors. The first flight went well, with the rocket slowly ascending into the blue sky and deploying a colorful chute a bit past apogee. The second flight, not so much, as the model arced over right after leaving the rail and followed a flat trajectory to the northwest. Breaths were held as the rocket nosed towards the ground, but the ejection charge deployed the parachute at the last minute, saving the model from a ballistic impact. I figure the F15 did not provide enough thrust to weight to get the rocket moving fast enough off the rail - the first flight was lucky to have occurred during a lull in the wind. An F32 or something like it would be better for "Sign Here Please"; 3D printed parts are heavy beasties.

"Sign Here Please" leaves the rail (Click to enlarge).

Coming in for a nice soft landing (Click to enlarge).

I packed two rockets for this launch - an Estes Meteorite White crayon and my recently repaired Probe-18, its payload section loaded with two altimeters. The Meteorite White was the first rocket to fly on Sunday, reaching maybe two hundred feet on a B6-4. Recovery was nominal, with the orange ripstop nylon parachute softly landing the model in the field. The Probe-18 was also powered by a B6-4; the purpose behind Sunday's flight being to compare the data recorded by my Altus Metrum Micropeak and Adrel Alt-BMP altimeters. The Adrel is a new addition to my electronics collection - measuring less than 1x2 centimeters, it is the smallest recording altimeter I have, and was designed for use in rocket competitions. The flight was picture perfect, with a good landing under chute.

Meteorite White leaves the pad (Click to enlarge).

Probe-18 starts another flight (Click to enlarge).

I am always amazed by modern tech - As we waited for the Longshots to make their final flight, Patrick and I were able to use our phones to watch the live stream of the Blue Origin New Shepard launch to the edge of space. Mannequin Skywalker got a fantastic trip to 350,000 feet, and I shook my head in awe at the spectacle of the booster landing. Truly great things are happening!

The New Shepard booster touches down on the pad (Click to enlarge).

Back at the apartment, I plotted the data from the Adrel and Micropeak altimeters on the same graph. I did not expect an exact match, but was surprised by the 4 meter difference in peak altitude, and the 7 meter discrepancy during the descent. Gonna have to think about this a bit, as both units shared the same payload section.

Comparison of Adrel data to that of the Micropeak (Click to enlarge).

To close this post, here are a couple of screenshots from altimeter software - the Micropeak works on multiple platforms, while the Adrel application is Windows-only. An unfortunate thing that altimeter manufacturers have in common is that they don't update their software as the operating systems go though major updates, which can cause issues. The Adrel software was a pain in the rear to install under Windows 10, though I see a new version was released back in January (I installed an older version in December) - maybe it makes things easier. The Micropeak app also had issues under High Sierra on my Mac - I had to disable a security feature to get it to run. Sigh...

Micropeak summary screen (Click to enlarge).

Adrel summary screen (Click to enlarge).

Building the Shrox Sniple - Part 2, Construction and finishing...

There are no instructions for building the Sniple, but it is very straightforward - only thing that is different from a "standard" rocket like the Alpha is that you have to note that the forward fins are 4" from the rear of the body tube. My build proceeded as follows:

• An 18" length of BT-50 was cut to 13", using the Estes tube cutting guides (very handy for quickly cutting Estes tubes). The tube spirals were filled with water-thinned Fill N Finish and allowed to dry until late afternoon of the next day.

• While the body tube was drying, the fin patterns were printed out on card stock. A 6" sheet of 1/16" basswood was sanded smooth using 400 grit sandpaper, and three of each pattern traced, making sure the grain was parallel to the leading edges. The fins were cut out using a sharp hobby knife, and the non-root edges rounded using 240 grit sandpaper.

Assembled Sniple motor mount (Click to enlarge).

• The motor mount was assembled (an Estes BT-20J, Semroc AR-2050, Semroc AR-2050S, and a standard 18mm motor hook). Most folks use some sort of tape around the middle of the tube to help hold the hook in place, but I cut a strip of card stock and glue it around the tube; I find this to be much more durable than tape. A length of kevlar thread was tied to the motor hook and run through the upper centering ring - the sewing elastic shock cord was then tied to the end of the kevlar thread. To avoid "Estes dents", my shock cords are always at least twice the length of the rocket.

Sniple body tube with spirals filled (Click to enlarge)

• After they had dried, the tube spirals were sanded smooth using 240 grit sandpaper, and the motor mount glued into the body tube. I used the spiffy Qualman Rocketry fin alignment guide to mark the fin and launch lug lines, which ran for 8" from the rear of the tube. A strip of card stock was used to draw a line around the tube at the 4" mark - this served as a guide for placing the rear of the forward fins.

BT-50 Qualman Rocketry fin guide for 1/16" fins (Click to enlarge).

• The fins were glued on using Aileen's Tacky Glue with the double glue joint technique. The Qualman guide functioned as a jig to insure proper alignment of the fins - it's quite a versatile tool. After the glue dried, fillets were created using 3 applications of Titebond wood glue smoothed with a finger.

• 4 coats of Brodak sanding sealer were brushed on, sanding with 400 grit after coats 2 and 4. At this point, the basswood fins were smooth as glass, and ready for primer and paint.

As of this writing, the Sniple has just been sprayed with the first coat of gray Krylon primer. I will wait a week to give it plenty of time to dry in the Southern humidity, sand most of it off, then hit the model with a coat of white primer. I will pick up this build thread when I have started the painting.

Ready for primer (Click to enlarge).

Building the Shrox Sniple - Part 1, Getting started...

Anyone who has been into hobby rocketry for a length of time has heard of Douglas Shrox - "The Master of the Dark Art of Rocketry". Shrox is legendary for his exotic designs, many of which have been turned into kits offered by Apogee, e.g., the Orion, the LexJet, the Sea Sting, the Stonebreaker, etc, etc. There is also some of his work published in the Apogee Peak of Flight newsletter, free for download; however, you need RockSim or Open Rocket (which can import RockSim files) in order to open the designs, extract the parts lists, and print out the fin patterns. I particularly liked the Bolaero, an Earth defense missile, and built it several years ago - it flies great! The downside to all this is that some of the plans (like the Tarmon) are missing, having fallen into Internet voids over the years. Hopefully they can be recovered by some enterprising sleuth.

The orange Rustoleum paint I applied to the Marauder yesterday did not turn out so well - I have some bubbles and a "cottage cheese" problem on the lower body and a couple of fins, which means sanding and more paint later on in the week when the current paint is fully dry. Feeling a bit frustrated, I sat down at the computer and started looking for something else to build. Nothing on my kit list appealed to me (though I should have considered the Trident or Starlight, which are on the 2018 build list). However, I did run across a Shrox design - the Sniple - stashed away on my hard drive, which caught my imagination with its Asian missile looks.

The Shrox Sniple (Click to enlarge).

I noticed that the Sniple had rather small fins, with one set being located fairly far from the rear of the rocket - not very stable. Sure enough, the RockSim file showed almost 30 grams of nose weight to insure stability, which means it's gonna fly like a pig - only about 180 feet on an A8-3. I also noticed that all that weight gave about 5 calibers of stability, so I kept reducing it until Open Rocket showed about 2 calibers with a C6-5 loaded - which occurred with 10 grams added to the nose. Much more reasonable, and a nice improvement in altitude. Still, I didn't quite trust the results - the rear fins look very tiny - so I loaded the modified file into RockSim, which produced a near match to the Open Rocket results. I feel better with both programs saying the model is stable, but the proof will be in the flying.

The Sniple in Open Rocket (Click to enlarge).

It's raining all day today, so I am gathering the parts to start building this little beauty. It appears to be the perfect project to occupy my time over the next couple of rainy evenings. If anyone else out there is looking to build something from scratch, I heartily recommend one of the Shrox designs (see post 65 in this thread) - they are very cool fliers!

Open Rocket visualization of the Sniple (Click to enlarge).

Free rockets of long ago...

This weekend's spring monsoon kept me indoors, which was probably a good thing, as it forced me to pay attention to the models on my workbench. Before the rain hit late Friday, I managed to get a base coat of white on the clone of the Estes cold-power convertible Marauder, a coat of white primer on the Centuri Mach 10 clone, and a coat of gray primer on the Centuri 1962 Payloader replica. Yesterday, while other folk in my area were preparing to build an ark, I built a clone of the Centuri Javelin from Semroc parts, and finished up the decals in Pixelmator. I want this model - my 50th anniversary rocket - to look like the one in the 1971 catalog, which I consider the "classic" look for the Javelin.

From left: Scratch Probe-18 under repair, Centuri
Payloader in grey primer, and Estes KL-3 Marauder
clone (Click to enlarge).

Centuri Mach 10 in white primer and Javelin
under construction (Click to enlarge).

Open Rocket visualization of 1971 Centuri Javelin (Click to enlarge).

I also sorted some of my old rocketry papers and ran across an old late-1960's brochure from Estes - "Yesterday and Tomorrow", featuring the Mercury Redstone and Orbital Transport on the front page. Inside there is an offer for four free rockets. You got to choose between a semi-scale Saturn V and a Constellation for an order over $10, or between a Gyroc and 2-stage Midget for a $5.00 order. Very cool, and it sounds ridiculously cheap here in Spring 2018. However, you have to recall that the dollar had much more buying power 50 years ago; $5 back then was equivalent to just under $36 in today's money, and $10 is equal to an appreciable $72. Still a good deal, but not as cheap as at first glance; I would have to save my allowance for a month in order to place a $5 order with Estes.

Page 3 of Estes "Yesterday and Tomorrow" brochure, showing free
rocket offers (Click to enlarge).

Things like this bring back fond memories of going to the post office to get a money order, sticking it in the envelope with the order form, and handing it with shaking hands to the amused post man. Then there was the excitement of checking the mail after school each day waiting for that box from the "Rocket Capital of the World" to arrive.

Good times...

Advancing to the next round...

Well, the dry spell for the Huntsville locale is over - we have a TARC team that is going to the national competition. The Saint John Paul II Longshots will represent their school at the flyoff in The Plains, Virginia on May 12; a win there will garner about 20,000 bucks of prize money and propel them into the international competition in London on July 20. Naturally, we are very excited for this first year team, and hopes are high!

The Longshots gather around their rocket, as "Benevolent Dictator" Duane looks things over (Click to enlarge).

Frankly, I didn't think they were going to make it - their best two qualification scores were a 21 and a 14.54, giving them a combined mark of 35.54. In the recent past, the cut off for making it into the top 100 teams was around 30, so I figured that the Longshots would appear on the list of alternates who would attend in case any of the top 100 didn't show. So I was both surprised and quite happy to see them make the finals, though it was a very near thing - the cut off this year was 35.56, just 0.02 higher than the Longshots' sum. Talk about the "hair of the chiny chin chin"! The Falcon Rocketeers had Huntsville's next best score - 36.04 (a 21.04 and a 15), which was just above the line, good enough to get them listed as the second alternate. So it is not outside the range of possibility that two John Paul II teams may make the late spring trek to Virginia; that would be totally awesome!

After the elation faded a bit, my nerd nature began to take over and I wondered if there was something in the Longshot's performance - as recorded in my notes - that may be useful in passing on to next year's teams. Even though I took much better notes this year compared to those of the past, there may be some missing data due to too much field activity. Nonetheless, a couple of things jumped out at me:

1) The Longshots fixed their design early, and the model (except for adding or taking away weight) did not change. It was your basic TARC rocket - nothing fancy, just good basic construction down to the nicely-sized fins and the very visible red and white paint scheme. I have seen other teams alter their model to improve stability (fins too small) or use a modular type construction that enables them to swap out damaged components. Stability is absolutely necessary, and in other arenas, modular would be a good thing, except that no two non-machine made components are exactly the same - different weights, different fin cross-section, etc.  These alter the performance characteristics, so swapping components is almost as bad as flying a new model each time. Hard to get consistent scores if the model flies differently each time.

The Longshots' rocket ("Phantom Flyer") leaves the pad powered by
an Aerotech F32 (Click to enlarge).

2) Of all the teams on the field, the Longshots were the most efficient - they moved through their checklist with increasing quickness, turning around the model in 30 minutes or so on the day of their final qualifiers. This is an advantage, as it minimizes the effects due to the rapid weather changes at Pegasus field in March. For example, the temperature gradient on March 25 and 31 was about 3 degrees per hour until early afternoon, with the wind slowly shifting its direction. Our teams record weather data, but I am not sure they know how to properly account for it, so being able to get flights off quickly improves consistency in the scores. The numbers show this clearly - On March 25, the Longshots were able to put 3 flights into the air for a mean score of 31 with a standard deviation of 28. They were much more efficient on March 31, flying four times for a mean score of 29, with a standard deviation of 14. The means are about the same, but the scatter is reduced by half!

TARC teams take note - make a good check list, and move through it quickly. An hour between flights will result in increase scatter in your scores.

Click to enlarge.

Those are tips for next season; for now, here's to the Saint John Paul II teams - may the Falcons get to join the Longshots on the TARC field of battle, and may one of them taste the fruits of victory!