Monday, August 20, 2018
Along with the pop-lugs, Fly-Away Rail Guides can leave the lugs on or near the launcher while the rocket continues upward.
These Fly-Away Guides are from Apogee. They also require a 1010 Aluminum Extrusion Rail to launch the rocket.
There are two complete guides in each kit. Five small orthodontic rubber bands are also in the bag. Four are needed, one extra is added.
Here's the bottom of the laser cut plywood.
There is some areas where the laser didn't cut all the way through to the bottom. It's understandable, this is 1/8" thick plywood.
The supplied Kevlar line is laced through the drilled holes and securely tied. I used a square knot. The knot is inside the lower capsule half.
The knot was "set" with a small drop of white glue.
A larger single hole is cut into the flat bottom of the 18mm shoulder.
Again draw a circle with a pencil. Cutting through the shoulder base took more time than I would have expected.
Sandpaper was wrapped around a tapered dowel and the edges cleaned up.
The shoulder was set on the capsule over the pencil circle. The Kevlar is fed through the hole in the shoulder.
Once I was sure the shoulder was centered, liquid plastic cement was brushed around the shoulder/base joint.
The Kevlar line seemed long so another knot was tied, closer to the shoulder hole. The excess Kevlar was cut off.
Sunday, August 19, 2018
The cut edges of the capsule halves were a little off. The cut ends have to be flat for the end to end taped fit.
It's a simple fix to sand off the rough cuts with 200 grit on a sanding block.
Don't blindly drill the holes with the tip of a knife, take a moment to mark the locations with a pencil. You might find yourself erasing and remarking the hole locations a few times. Leave a little space between the two hole locations for strength.
Start the drill with the tip of an X-Acto knife.
Widen the holes and clean up the edges with a small diamond rat tail file. You want the hole edges clean and strong. Sometimes vacu-form parts can get thin.
Set the shoulder over the end with the drilled holes. Center it as best as you can visually and trace around the joint with a pencil.
Chances are the traced circle will be a little off center. Erase the circle and try again.
The pencil traced circle will assure that the shoulder will be centered.
Saturday, August 18, 2018
Now available from JonRocket.com:
BT-20H HEAVY WALL BODY TUBES!
To see the listing, CLICK HERE
On the left is a standard BT-20, on the right is the heavy wll BT-20H.
Standard Estes BT-20 style tubing is thin walled (.013") and prone to buckling and bends. Thin wall tubes can’t insulate well against the heat of ejection charges. Paint above the engine mount area can blister.
Heavy wall BT-50 tubes are already available, why not a stronger BT-20?
This new tubing has the same wall thickness (.021") as a BT-55 or BT-60 tube.
The inside diameter is the same as a BT-20 tube. (.710")
Thicker wall tubing is less likely to shrink or “coke bottle” when a glue fillet dries.
Standard engine blocks (5/20 rings) will fit as an engine block.
Existing centering rings can be easily peeled or sanded to fit the slightly wider outside diameter.
Comparing both tubes, an 18" length of the heavy wall BT-20H weighs a little over 1/10th an ounce more than the standard BT-20.
- Engine mounts - Perfect for the new C and D Quest Q-Jet engines.
- Ejection Stuffer Tubes - Stronger when exposed to ejection charges. Longer life, more flights.
- Strap-On Boosters - Less damage on landing under streamer recovery.
- NAR Superroc Competition - Stronger tubes for longer length designs.
- Sport Models - Stronger as a main air frame tube. More success for school, Scout, 4H and general sport rocket projects.
The yellow plastic nose cones from Apogee are a great fit for the thicker wall tubes. These nose cones have a wider shoulder than standard BT-20 fit nose cones. CLICK HERE
I'm basing my C engine Egg Lofter design on the old Competition Model Rockets Robin design.
To see the CMR catalog: CLICK HERE
I'm really doing a lot of guessing with my competition designs. I know you have to keep them light and aerodynamic.
The only NAR competition I did was in 1975 and 1976. Over the years some things have changed, other elements haven't really changed at all.
I'll base my model height and body tube diameter on the Robin design. Note the CMR tube walls were a little thinner than the equivalent Estes sized tubing. I'll be using Estes tubes in these builds.
The model itself is very simple except for the Egg Capsule.
Years ago, CMR was the main source for lightweight, vacu-form nose cones. CMR also made the larger egg carrying capsules.
Apogee now sells vacu-form capsules. This parts pack has shoulders for both 18mm and 25mm models.
This build is one I put together for the recent NARAM. After a two hour tour of Estes, I got back to the launch field too late to fly it!
Friday, August 17, 2018
There was a few questions raised in the instructions. I have mentioned them to Randy at Semroc.
It's interesting that a Micro Maxx downscale probably as difficult to construct as the full size original. Maybe harder?
There are the same amount of parts as in the original full-size kit, just smaller.
Holes were punched with a bamboo skewer where the Sharpie dots were drawn.
Short lengths of bamboo skewer were cut.
For the longer models that will lay on their side, two posts will sit on either side of the body tube.
Here's how the models ended up. Not very glamorous, but the models are safe and together in a small area.