The Semroc Bandit - Part 1

I've realized I made a mistake with #NaRoBloMo. That is, I promised to follow up the first N00b T00b post with another N00b T00b post, addressing specific topics. Then, I kept feeling obligated to write that before writing anything else, making this blog feel like work. This is part of my hobby - and supposed to be fun. So, I'm going to jump around as I see fit.

Semroc is one of those model rocket companies which nearly disappeared a few years ago, when its previous owner, Carl McLawhorn, unexpectedly passed away. Eventually, Randy Boadway of eRockets.biz purchased the company, and continues to produce its high quality model rocket kits and parts.

Despite the fact that eRockets is a sponsor of The Rocketry Show podcast, and that I've had several Semroc models waiting on my build pile for a long time, I'd never actually built one. My Estes back stock was just so out of control.

But I hadn't built a kit in a while. After finishing the N00b T00b, which was just a quickie scratch build to get me back into it, I decided it was time to grab something off the pile of kits and start. But what?

I haven't counted my pile. It's... well, it's enormous. If I tried to count it, I'd probably miss something, as I have kits stored here and there. So, what to build next seemed like a huge decision.

I decided to build something non-Estes to start with. I had some FlisKits, some AeroTech, a Squirrel Works Arapahoe E (which looks like a really great kit), plus a number of Rocketarium scale sounding rocket kits, plus some stuff from Quest. And maybe more, I'm not sure.

I thought this was all of my smaller non-Estes pile. I realized later it wasn't even close.

I made a small pile of what I thought were all of my non-Estes low and mid power model rockets (I decided not to start with high power). I realized later there were a few missing from the pile.

Nonetheless, after some thought, I decided it was high time I built a Semroc, since it was one of the first non-Estes companies I had heard of, but I'd never actually started a model. And I chose the Bandit - a "Retro Repro" model - a pretty close recreation of a classic, out-of-production kit (in this case, a 1971 Estes model). It was a nice, classic (I know I have used that word too frequently already, but it's what it is), great-looking model. Having seen a few online and one really nicely built one at a club launch, I felt I needed to have one.

One thing which impressed me about the Bandit was the quality of the parts. The tubes are all very nice, and the balsa nose cone and nose block fit very well. The other thing about the balsa nose cone I liked was how closely the base of it matched the outside diameter of the body tube.

A lot of long-time model rocketeers seem to prefer working with balsa nose cones, rather than plastic, if what I've seen in various online forums is true. Since I've only been practicing rocketry for about five years, I actually haven't worked with that many balsa nose cones. Estes has switched over to plastic, and the few kits they produced with balsa cones either are out or production, or soon will be.

The thing I've encountered when working with balsa cones - again, in my limited experience - is that the base of the nose cones often seem to have a wider diameter than the body tube, so that the cone overhangs the tube by a significant step.

A balsa nose cone which overhangs the tube a bit. It's not so easy to see on camera with the black paint.

A balsa cone with a significant overhang. I turned this one upside down into the light so you could see it better.

I always assumed that maybe it was harder to get balsa to a specific diameter on a larger scale of manufacture without taking off too much material, and so they'd err on the side of slightly too large. Something like that - it was a guess.

Anyway, I encounter that far less frequently with plastic nose cones, and I really don't like that step. If I were to sand the base of the cone down to match the size of the tube, I'd change its shape. So I don't want to bother with that.

When I made my hand-turned balsa cone for my scratch-built Big Bertha, I tried - and succeeded - to get the diameters to match pretty closely. But that was me spending a lot of time and effort on just one cone. Maybe they couldn't do that with a large batch, I figured.

But the Semroc nose cone is such a nice fit.

The Bandit comes with a ducted ejection charge system. Basically, the motor mount is an ejection baffle. Rather than allowing the ejection charge to blow straight up through the tube, the hot gasses pass through a series of holes in two tubes. The flame shoots straight up and hits a balsa bulkhead, but the air passes through the baffle system before pressurizing the rocket and ejecting the parachute. This means you should not need recovery wadding (though the instructions do recommend a sheet or two, just to be on the safe side).

The holes are all laser cut and quite neat.

The one issue with the parts was that the fin sheet was kind of beat up, and one fin had snapped in two along the grain.

This was unfortunate, but not reason enough to my mind to complain.

I can't remember if I bought the Bandit directly from eRockets.biz, or from JonRocket.com. In either case, if I had sent an email to complain, I'm sure would have done something to make it right. But both are - quite literally - "mom and pop" type operations, small family businesses. If there had been something badly wrong with the rocket (say, it had been crushed or something), I'd have sent an email. But in this case, it's not like there was any negligence or bad handling, and I didn't feel like making anybody jump through hoops for me for a bit of balsa.

The kit was otherwise in fine shape. This is one of those things that happens, and it's an easy fix. First, the fin split cleanly along the grain, and could easily be glued together. The bond would be strong and invisible.

Another option would be to trace a fin onto some balsa or basswood fin stock and make a replacement.

I often make an extra whole set of fins, so I can sand them to a particular shape if I want to. Say, I want to sand an airfoil. It's nice to have a set of spares, so if you make a mistake, you have extras. Frequently, they all turn out pretty good, so I'll build a second rocket - a copy of the kit. Then I have two.

I glued the broken fin back together, and after stack sanding the set, I traced them onto both some 3/32 inch thick hard balsa stock, as well as onto some basswood. I liked how the balsa came out better, so I used that. After stack sanding, I had two identical sets of balsa fins to play with.

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