Thursday, May 26, 2016

Building The Pitsco "Model A.1" - A Review

Two years ago, I built and reviewed a Pitsco Solid Fuel Rocket kit, which I referred to the "Model A". A representative from Pitsco, Melissa, read the review, and offered to send me a newer version of the model to see what changes were implemented. The first one I built was an older version, from 2001 no less, and had been in my collection for years, a survivor of a pair we ordered when I was at the South Florida Science Museum.
I took her up on her offer, and a short time later she sent a new Pitsco Solid Fuel Rocket, one that I refer to as the "Model A.1."
Unfortunately, life got in the way, and it took over two years to finally get around to building the model. Unlike the model I built in 2014, this model I built mostly by the book (mostly). This is a review, with some observations.

Body Tube -
Like the original model, you have to roll the body tube, with the first layer being typing paper (I imagine notebook paper would work as well). They recommend rolling it as tight as possible around the plastic core, but to not glue until you get to the last 1" (25mm). 

Still, I think it is probably a good idea to use something like a glue stick or white glue to add as close as possible to that initial wrap, being careful not to get any on the plastic core. The rest of the wrapping went per instructions. 

Once it was all dry, I trimmed off the excess gummed paper tape, removed it from the plastic core, and set the tube aside. When it had dried, I made the initial line for the launch lug and attached it.

Fins -
The original booklet wasn't clear with how to lay the fin pattern out on the material. This time, they show you how. That was good, as there is really just enough material to make the three fins. I chose to make a copy of the fin pattern and use that as the template. 

The three fins were cut using a sharp razor knife. 

As I still do not have a fin guide, I marked the lower end of the body tube and used both the plastic core and a ruler to make three 4" (100mm) lines for the fins. Each fin was attached with white glue. I used my normal pre-glue method here; a bead of white glue is applied to the fin root, the fin is pressed into its place, and then removed, allowing for the glue on the parts to dry. Then, I used white glue again, applied it to the fin root, and attached the fins. This gives a stronger joint. When the fins had dried, another bead of glue was applied as a fillet on either side of the fin root.

Back to the body tube. There is a problem that arose that might crop up with others. As the inner layer was not glued, it tended to unroll on the inside. This was probably due to humidity here in Florida affecting the paper. I applied a little glue carefully to the inside of those layers and pressed the paper outwards. I also applied a little bead of glue around the end of each edge to serve as additional reinforcement.

Shock Cord & Engine Mount -
Since the page that had the fin pattern had been copied, so had the shock cord mount. This was cut out, and the shock cord attached according to the instructions. This was set aside to dry.
My one big area of concern with the model was the engine mount. This was something that didn't change on this model. In my initial build, the engine mount was modified so that the forward part of the engine clip slid into a slit near the top of the engine tube (about 1/4"-6mm down). Pitsco calls for the engine clip to simply be put over the engine tube, with one end over the top of the engine mount, the clip held in place with the spacer rings. This time, I chose to stick to Pitsco's instructions, but feel that this is still an area of weakness. However, the engine spacer rings are a tight fit, so perhaps the clip will be held in place fairly well. Flying the model will determine how well that works.

Parachute & Final Assembly -
The rest of the model went together according to the instructions. The only change I made to the parachute assembly was to put a drop of white glue on every knot. This is an old trick I've used, as there is nothing worse than having shroud lines coming undone. 

Before the final assembly, I chose to paint the model, as I had the previous model. Unlike the previous model, a gray primer coat was skipped. The model was painted white, sanded smooth, and then painted a bright yellow. Of course, painting the model is optional, as in unpainted form it will still fly.

Once the paint had dried thoroughly, the final assembly took place. The engine spacer rings on this model were a much better fit than they were on the previous model, so no paper layer was needed to build it up. 

The parachute was attached to the screw eye, and then the screw eye was attached to the nose cone.
Final details consisted of the same red and white checkerboard pattern self-adhesive decal material I had used on the first model. 

As the first model was red and this one yellow, they have been named "Cardinal" and "Canary".

Conclusion -
The changes here were minor, but important. I like that the fin material layout is now shown on the instructions, and the new engine spacer rings seem to be a better fit. However, the method for rolling the inner body tube could cause problems for some, and the engine mount may be an area of concern on later flights for the model.
Still, this is a light model, definitely stable, and probably a good performer. This is something I hope to test soon enough.
Stay tuned.
Here we are, late June, 2016, and the models still haven't flown yet! The weather here this time of the year is dodgy. As soon as they fly, I will share! - RL)