Below you will find pictures highlighting my deep dive into model rocketry…they will be somewhat in chronological order to show techniques and products I learned about along the way, and some of the results!
I started back into model rockets in 2009…I had not even thought about them since I was a kid back in the early 60’s, when I would trek out with my brother and fire off Estes rockets and motors…I was in a hobby store one day and noticed some Estes stuff on the wall and it brought me back to those days…I did a little looking around and found out that they have a model rocket club in San Diego – they fly out in the Imperial area east of the city…I headed out there at their next launch and was amazed at how sophisticated some of the guys’ rockets were – especially one built by a guy named Mark Clauson – he got me hooked!
Seeing Mark’s rocket soar away (he was going for some sort of an altitude or speed record and used what is called a “moonburner” (low thrust, long burn time)) and going though the local parts vendor’s (Jack Garibaldi) on-site trailer seeing so many goodies pushed me to get on the internet and find out more about high-powered model rocketry (motors that are 100’s of times more powerful than the little Estes motors).
I found lots of information about such rockets and their fabrication…lots of rocket kits and loads of different motors available…also, I determined that the club was an affiliate of the National Association of Rocketry (NAR)…NAR has an ascending set of levels that you can be certified at, which then allows you to purchase the bigger and bigger motors as you progress through the level structure…so, off to achieve Level 1!
At the time, I did not think I was intending to go high – I had seen several rockets at the launch zoom off and basically go out of sight – but rather build rockets that seemed more realistic with slower ascents and lower altitudes (this poroved to be a false assumption as I progressed in the hobby)…
Hermes 1 – a modified Aerotech Aerospace G-Force The major modification was to change the motor mount (MMT) to a 38mm diameter from stock 29mm and using a GROOVE-LOK from Giant Leap Rocketry to anchor fins to the MMT. Additionally, I used 0.187 plywood bulkheads and centering rings throughout. I added an electronics/payload bay to the sustainer section and changed out the chute for a larger one. For ease of use, I also added an Aero Pac Quick-Change motor retainer.
I had to reduce the tang on the stock plastic fins in order to accommodate the larger MMT and the GROOVE-LOK. I used a power miter saw to cut them slightly larger than needed, then fit them with a file. Care must be used not to let the plastic piece get too hot and start to melt – just be patient and take a bit at a time. I bought a 6″ GROOVE-LOK but cut it to fit between the two rear centering rings that encased the fin tangs (picture). The fins were 6-filleted (each side of the fin where it attaches to the motor mount tube, and two both inside and outside on the airframe tube where the fin inserts) with 30-minute epoxy.
I replaced the stock 42″ chute with a 50″ one due to the increased weight of the mods and I used a Nomex® piece in lieu of the baffle that was sent to use with the stock MMT.
The MMT is a phenolic 38mm x 18″ tube from Giant Leap to replace the paper 29mm factory unit. The main coupler (where the payload section joins with the booster section) was replaced with a phenolic one from Giant Leap and epoxied to the booster rather than the sustainer to better protect the booster lip on ejection.
The e-bay was scratch built from a phenolic coupler and plywood bulkheads. The sled (platform where the electronics mount) slides on 8-32 all-thread and is made from 1/8″ balsa plywood and two pieces of aluminum 3/16″ square tubing.
I used the GROOVE-LOK, so that once I set one of the fins in place, the alignment of the others was a snap, plus the individual groove rails gives the fin a nice sturdy mount to complement/strengthen the expoxy fillet. The exterior fin root bulges in the middle making the filleting process a bit more difficult to make it look good, but I had it down by the third fillet.
The overall kit went together easily and the instructions were clear. I filled the airframe tube spirals with Elmers wood filler and acheived a decently smooth exterior with one application and sanding. I did not use the included decals, but rather made my own. The finish was gloss white. Looked really nice sitting on the launch pad.
Flight – The stock kit called for G motors (motors are rated for their total thrust using the alphabet, A being the smallest and going up from there), but going from the 32 oz. stock dry weight to the final 56 oz. for the modified version called for more power. I bought a G38, a G40 and a G77 with the kit before I decided to modify it.
I simulated all of my rocket builds and their flights using a software product called RockSim – it proved over my journey to be a wonderful tool to match motors with different rocket configurations and see how they performed. The G38 and G40 RockSim’d as a crash, whereas it said that the G77 should put it to 400’+, which is what happened.
The first flight was on a G77-4 (the digit after the dash indicates how much delay in seconds there will be after the motor burns out before the ejection charges blows the sections apart allowing the recovery chute to come out 0 the target is to have the ejection charge fire right after the rocket reaches apogee to minimize the force on the chute when it opens.
Hermes 1 flew perfectly straight with the motor ejection occurring right at apogee and no roll (turning around the vertical axis) to speak of. The bottom of the booster tube sits about a 1/2″ below the bottom of the fins, so on a perfectly still day like we had, the rocket lands on the tube. It crinkled just a bit on one edge. I saw in an earlier article that someone had reinforced that area with a piece of coupler tube. I intended to do so but forgot – wished I had, but I will reinforce it somehow in the future before it flies again.
On landing, the booster hit on the hard-pack desert road and worstened the crinkle, so I definitely needed to add something there, or, go to my 58″ chute, or, both.
The G-Force is a great flyer as reflected in all the reviews I had read during my research The stock components were very nice as far as quality, but I wanted something a bit stronger in the booster/fin configuration since I planned to eventually see about the rocket going to 5K’ (see Hermes 2 below).