Thursday, December 5, 2019

Glue Filler? Part 1

I see it on the Facebook Rocketry pages once a month.
Somebody asks: "How do I fill the balsa grain?
One or two replies is always: "Use glue! Rub it in and sand it off. I get really smooth fins that way."

I'll be honest, I did this on my first rocket back in 1969. I didn't want to spend 35 cents for a little bottle of the Sanding Sealer that Estes recommended.
After you use a proper filler you probably won't want to go back to using glue on fins.

There seems to be plenty of builders using glue to fill balsa. Maybe I'm missing something?

I cut two small fins from the same scrap piece of 3/32" balsa. I wanted to be sure the balsa grain was consistent between the two pieces.

Wood glue was applied over one side of the fin and smoothed out with an index finger.
Allow to fully dry before thinking of sanding.

Carpenter's Wood Filler is in the next post.

Lawn Dart Rocketry SLAT/S Build, Finished

I did add two more chrome stripes around the body. With only two decals on each side it needed more. I probably could have gave the Stars and Bars decal some white underneath it.

The Seattle Rocket Works kit had 1/16" thick balsa vanes at the front end of the intake. I left them off, they'd be very hard to smooth out once glued inside the tube.

I tried to give the back end some more interest. The original kit had everything flush (even) with the back end. On this build, the engine mount extends beyond the end of the main air frame tube and has the chrome trim. The fin fairings are a little forward and the end of the intake is even farther up.

The fins seem small, I did add .25 oz of clay to insure stability.
This will get a first flight on Saturday, December 7 at the monthly Orlando R.O.C.K. launch.

Wednesday, December 4, 2019

Lawn Dart Rocketry SLAT/S Build, Part 10, Paint and Chrome Trim

The model did get a gloss white undercoat before the overall gloss orange.

I wanted to add some chrome trim like on the Odd'l Fighter Fleet models. This isn't necessary, but paint on the hook will just bubble up after the first flight. On the finished model it just looks cleaner.

TIP: First I scraped off the orange paint on the engine hook. I use the backside of the blade. No sense dulling up the sharp side.

A strip of Monokote chrome trim was started under the engine hook and rolled around the exposed end of the engine mount tube.

The overhang is cut off with a sharp blade, even with the tube edge.

Tuesday, December 3, 2019

Lawn Dart Rocketry SLAT/S Build, Part 9, Gluing It Together

The intake half nose cone was set on the intake center line and traced. The filler/primer was scraped down to the body tube. The half nose was glued down.

Notice in the left picture, the scraped line for the intake tube. I used very little glue to set the intake onto the body tube..

Here's where we are now.

This was a loose build. I did follow the directions but didn't use the intake template. I just cut something out.
The fin assembly angle wasn't steep enough when set against the edge of the intake.

I had to go back and cut a slot out of the intake edge. The fairing was set next to the intake and marked to see how long the slot would be.

This is what I wanted, more downward angle on the fin assemblies.

Monday, December 2, 2019

Lawn Dart Rocketry SLAT/S Build, Part 8, Parts Fitting

The fin fairing pieces had the balsa grain filled with CWF and sanded smooth.
I wanted to shoot the pieces with filler/primer before gluing the fins in the slots.

A strip of masking tape was cut a little wider than the slot widths. This was pressed into place, the overhand kept the filler/primer off the sides of the slot.

The Starlight nose cones are now available from Apogee. The shoulder lip is a hair wider than normal, but fits the BT-50H (heavy wall BT-50) tubes perfectly.
Sometimes you find a slight flare at the lip. This was sanded down slightly to fit the body tube diameter even better.

The intake tube was slid over the bottom of the main tube. Lines were drawn along the sides.
The primer was scraped along the line for a better glue bond.

Sandpaper was wrapped around an engine casing and the bottom curve sanded. As I mentioned before, I use a smaller diameter piece to wrap the sandpaper around.

And, here's the fit.
Set against the intake, it didn't go as planned -
More in the next post.

Sunday, December 1, 2019

I Wish They Didn't Do That - Part 5, Something I WISH They'd Do -

I know the title is confusing. For safer club launches, here's something I'd like to see  - 

If you've ever been an R.S.O. (Range Safety Officer) at a club launch, you'll meet newbies with their first rockets. They may not have installed a recommended engine.
The RSO takes the launch card, the card information is incomplete. No engine type is listed.
You ask: "What engine type is in the rocket?" You get a confused look.
The newbie says: "It's a C3-7, or something like that."
You know that engine doesn't exist. A seven second delay would be too long for that stubby rocket. You might have to pull the engine and check the designation.
I've seen first timers load booster engines (no delay) in single stage parachute recovery rockets.

Food for thought:
Most all engine mounts have the engine extending 1/4" out the back.
Can there be the engine type printed on that visible, exposed back end? This could make for easier check-in, safer launches and recoveries.

There might be reasons why it hasn't been done. The engine printer might not allow ink coverage down to the low end of the casing. When I worked at the print shop, we had to allow some border for the "gripper" on the printer.

The picture above shows colored bands I printed from a blog post back in 2010. The coloring isn't necessary. The engine type could be in black ink or colored (GREEN standard, RED Booster or PURPLE Upper Stage). It could be easily seen at check in if it was printed three times around the engine circumference.

Lawn Dart Rocketry SLAT/S Build, Part 7, Engine Mount

I used an Odd'l Rockets heavy wall BT-20 tube for the engine mount. These tubes are thicker than a standard BT-20 and only available from
The inside diameter is the same as a standard BT-20. The outside diameter is a bit wider. To fit a standard 20/50 ring, the inside is slightly peeled to fit the tube. This is easier than you'd think. The inset picture shows a good friction fit.
The rings are then notched to clear the engine hook.
The 150 lb. Kevlar shock cord line is tied in a loop and slips under the upper bend of the engine hook.

The upper ring is slid over the top bend of the engine hook for a stronger mount.

The rest of the construction is standard. The lower ring is glued 3/4" from the end of the BT-20H tube to allow the hook to flex.
An engine block is glued on top of the upper bend of the hook.