Wednesday, July 31, 2019

Catching Rockets?

There was a spirited debate on TRF about catching model rockets -

Boy, I'll probably catch heck for this one - 
If a rocket is coming down slowly under parachute, and are within arms reach - I might try to catch it, by the shock cord or parachute lines.

If I'm at the schoolyard I might catch one out of five launched in a session.

I wouldn't do this at a club launch, there you wait until all rockets on a rack are launched and you get the "Okay" to recover your models from the RSO. But - If I'm by myself and it's a slow descending rocket under a parachute - I might try to catch it before it hits the ground and breaks off a fin.

Look at our history - 
All these photos are taken from older Estes and Centuri catalogs. At the time, these pictures implied it was okay.

That was before engine hooks with finger tabs! Those extended finger tabs could hit you in the hand a draw blood! Some of these pictures are before thin plastic fin units that could cut your hand.
These pictures were in catalogs up to the mid 1980s. Model Rocket manufacturers don't need angry letters or lawsuits.

It comes down to common sense.
My model rockets are on the smaller end of the spectrum - lightweight, low power and under two feet tall. I'm an adult, I remove finger tabs. I wouldn't think of catching a 1/100th Saturn V, a six foot tall Mean Machine or a spinning recovery rocket.
"Hey Chris, catch that booster as it tumbles in!" - NO.

If anybody were watching, it'd be funny seeing a 63 year old man dodging and weaving to get underneath a rocket under parachute.

Semroc USS Andromeda KV-97, Part 9, Fin Alignment

The large wing fins are glued on using the larger assembly jig.
Set the engine end tube into the large jig, the front of the rocket is set into the upper jig for support.

Glue the root edge. Set the fin onto the jig and slide into the body tube setting the rings into the notches.

The front end dowel support standoffs are glued on using the smaller forward support.

The smaller triangle is used to set the 90 degree angle on the small antenna platform fin.

Use the same triangle to set the engine pylon fin.

Tuesday, July 30, 2019

Fin Glue Rivets? TIP

Here's one way we used to reinforce the fin root edge joints - FIN GLUE RIVETS!
This illustration is from the 1977 FSI catalog.

Punch holes down the fin position pencil line with a needle. When glue is applied it should press into the pin holes and make an effective glue rivet!
I don't think I would use glue rivets on a minimum diameter model. (BT-20 with an 18mm engine or a BT-50 with a 24mm engine.)

Glue Rivets could be considered the predecessor of thru-the-wall (TTW) fin mounting, certainly stronger than surface mounted fins. I would rarely use them unless (in certain circumstances) I really wanted a stronger bond.

I'm currently building another Estes Mercury Redstone.
Those tip plates glued onto the outside of the fins have some laser cut dashes down the middle. I hadn't thought of these in years and realized here's a modern take on the old glue rivets!

The outside fin rudder could break off on a hard landing. Chances are, the card stock plate would probably split down the middle into two pieces. An easy fix.
For the first time in years - I made some glue rivets on the root edge of the fin rudders. The rivets might make this end glued joint stronger.

Semroc USS Andromeda KV-97, Part 8, Gluing The Radiator Rings

The trailing edge tip of the large wing/fin is even with the end of the body tube.
The picture shows how the top ring will fit into the root edge notch in the fin.

With the ring glue on, double check using the fin to be sure the back of the fin is even with the tube end.

Glue a ring, add a narrow fillet on each side, then glue on another ring.
TIP:You'll find it easier to fillet each ring individually as they are close together.
Use the same technique to glue on the second and third ring.

Here's all three rings in place prior to gluing on the two large and two smaller notched fins.

Monday, July 29, 2019

Semroc USS Andromeda KV-97, Part 7, Cleaning Up Parts

The short tubes have interior seams! You'll be able to see them on the finished model so of course, I'm filling them!

The launch lug ends were a bit rough, sand them smooth with 400 grit.

The heavy card stock pieces are laser cut.

These will need some cleaning up.

Sand the burnt edges flat on a block.

Look at the right side picture - the side wasn't cut flat. I sanded it down and evened up the line.

The notches in the wing fin fit over centering rings.
TIP: The edge of the card stock piece were pressed into the wing fin notches to square them up and make for a better fit.

New Gryphon Boost Glider Kit From Estes

The new Gryphon boost glider is now available from Estes.
The website picture might be of the two Gryphons I recently built for Estes. The Boosted Bertha and Sasha are also shown as now available.
A blog build is coming after the Semroc Andromeda, the Estes Boosted Bertha and Estes Sasha!
Lots of builds in the pipeline - 

To see the new kit listing: CLICK HERE

Sunday, July 28, 2019

First Engine Hooks?

Yesterday's post about engine retention got me curious to find the first introduction of the engine hook

These go back farther than I thought, to the Estes Model Rocket News from June, 1964. While most call them an engine hook, here they were referred to as an Engine Holder.

The first use of an engine hook was in the first Estes kit, the Scout. That engine hook was bent out of thick wire, not the flat spring steel shown here. The short engine hook was used in the Astron Sprite, also introduced at the same time in 1964.

EDIT: Bernard Cawley corrected me in a comment: The Sprite used the standard longer, 2.75" hook so the shorter 1.75" Series III engine could slide back at ejection.

To see this issue of the Estes M.R.N.: CLICK HERE

Semroc USS Andromeda KV-97, Part 6, Assembly Jigs

The assembly jigs are assembled as shown on the right. These just slide together, you don't really need to glue them.
The short tubes are used in the jigs now and glued on the small fins later.

The smaller jig is used in the front to glue on and center the dowel standoff support pieces.

The larger jig with the tubes is used on the back of the model.

You can lay the large flat wing fins on the jig for perfect alignment. The original Estes kit didn't have these tools!

Saturday, July 27, 2019

Old Big Bertha Instructions

A blog comment made mention of the Big Bertha nose cone. The shape and length have changed over the years. The old balsa BNC-60L nose cone had 3 1/8"exposed above the body tube edge. It was longer and not so blunt as the current plastic PNC-60L or part #71020.

Here's the parts layout from some old Big Bertha instructions. Compare the "A" part balsa nose cone to the current Big Bertha and Baby Bertha nose cones.

To see the older instructions go to or CLICK HERE:

Here's a better profile example of the original nose cone shape, a rounded ogive.
You can get it from CLICK HERE

From the same instructions -
This original Big Bertha was produced before engine hooks were used in larger diameter models. The earliest engine "holder" hook I can find was in the 1966 Estes catalog.

I first saw this simple outside the engine mount tape retention method on an Apogee video. I don't remember ever using this when I was in my teens, my rocketry experience started in 1969.  We certainly used a lot of masking tape "friction fits" until more engine hooks were introduced into kits. Until today, I didn't know how far back this tape retention method went!

Semroc USS Andromeda KV-97, Part 5, Low Engine Mount End Assembly

The lowest centering ring is notched for engine hook movement.
TIP: The flat side will be exposed so sand it flat with 220 grit on a sanding block. Sand one side of the (closed) upper ring, it wall also be exposed.
On the left is before, on the right is after sanding. With the flat side of the ring smoother, it will end up looking cleaner when paint is applied.

Slide on the upper ring up to the 4" mark. Glue in place.
TIP: Glue the notched ring even with the tube end. Use a rubber band to hold the open lower ring ends down against the body tube.

Here's what the low end looks like now.

Set the engine hook. Cut a notch at the top for the engine hook bend.
Place a wrap of masking tape to hold the hook in place.
TIP: Paper masking tape can break down over time. I like to use longer lasting electrical tape.

The 4" long ST-9 tube is glued over the rings with the ends of the rings even with the ends of the tube.

This shows the upper tube/shroud assembly. The main body has been shot with primer/filler and was sanded to surface.

Friday, July 26, 2019

Semroc USS Andromeda KV-97, Part 4, Upper Shroud Gluing

TIP: At the inside edge I did sand down the glue tab so I could get a better fit against the body tubes. The tab area is thick!

Slide the adapter up to the centering ring - dry, no glue yet. Trace around the back small end with a pencil. Slide down the shroud.

Apply a thin line of glue around the pencil line and another along the bottom edge of the centering ring. You don't need much glue to attach the shroud, too much glue can saturate and distort the shape.

Slide the shroud up and into position on the glue rings.

The longest 7 3/4" ST-9 tube is glued over the centering rings up to the edge of the shroud.

TIP: While the glue is still wet you can mold the wet card stock shroud edge to better fit against the body tube. (Here the rocket is upside down.)
Roll a smooth burnisher over the edges as the glue dries.

I did go back and add some CWF down the seam bump. This was sanded smooth.

After that, the shroud got an overall wipe of CA glue applied with a Q-tip. After the CA glue dries you can lightly sand with 400 grit. It should finish like plastic.

Thursday, July 25, 2019

New Kits From Estes Available!

The Sasha, Boosted Bertha, Double Ringer and a new version Phantom are now available on the Estes website: CLICK HERE

I have already built two Sasha and Boosted Berthas for Estes.
The Boosted Bertha has two of the new 18mm screw on motor retaining rings. The Sasha sports gap staging with a booster "directional cone" and vented centering rings.

I'm interested in seeing a flight of the Double Ringer - the instructions and tube glider assembly is interesting. To see the Double Ringer instructions: CLICK HERE
This one reminds me of the old Flying Stovepipe plan - CLICK HERE

I'll be featuring both the Sasha and Boosted Bertha builds on the blog after the Semroc Andromeda is complete.

Semroc USS Andromeda KV-97, Part 3, Upper Shroud Prep

The reducer shroud is laser cut! Another benefit of modern technology.
The sides will be charred, wipe them off and lightly sand with 400 grit if needed.

I did my usual shroud forming by rolling a dowel over the card stock in the heel of my left hand.
Press and form the shroud by moving the dowel in a arc or "piece of pie" movement. Go all the way to the outside edges, get a curl there, too.

TIP: Thin card stock shrouds require very little glue on the gluing tab.

After the shroud is dry, you can go back and do more forming in your hand with the dowel. Get both sides as near to a perfect circle as you can.

Before marking the tube for the gluing of the upper centering rings, be sure you are marking the upper tube!

On ring is 2" from the top, the other ring is even with the top of the tube.

Dryer Sheet Wadding?

From the Facebook Estes Model Rocketry page:

Mark E. Johnson asked:
"Has engine thought about using crepe paper party streamers for recover wadding? Back in the day I don’t think it was fire proof/resident but these days I’m thinking it might be.

Matt Matt posted:

I like leftovers on the field from previous launches, but my go to is dryer sheets from the dollar store. Perfect for the application.

I use flame resistant crepe paper wadding all the time.

EDIT UPDATE: I just found two (old) dryer sheets. I didn't even know I had them. Single guys don't use fabric softener sheets, that's a married thing.
Anyway - I held a match under the dryer sheet and it easily melted! It didn't go up in a flash, but it did melt. Matt Matt may be using a different brand than I just tried.

Wednesday, July 24, 2019

Semroc USS Andromeda KV-97, Part 2, Joining the Body Tubes

Test fit the coupler in the body tubes. Don't glue in place yet. Sand the edges if needed for a smooth fit. The side of the coupler with the hole is the upper side.
The coupler is marked with pencil at the halfway point.

Always square up the body tube ends before doing any gluing. Sand the ends using a block.
On the right I am rolling down any "burr" with the back end of a Sharpie barrel.

Glue the lower half of the coupler into the lower body tube.
Tie the Kevlar line in the coupler hole with a secure knot.

Drop the Kevlar line through the second, upper ST-7 tube.

Apply some glue on the inside of the upper tube. Slide the coupler into the upper tube until both tube ends are butted end to end.

Roll the two tubes on a flat surface to be sure both are straight and in line with each other.

Free Plans From Apogee

If you visit the Apogee Rockets Website you should find this offer -
FREE PDF Book of 25 Rocket Plans!
Simply subscribe to the Peak Of Flight Newsletter - CLICK HERE
Free plans - GOOD! Add the POF Newsletter  - Better GOOD!

EDIT UPDATE: You have to treat this FREE offer and "order it" like you would any rocket part or kit. They will then send you a link for the plans. Lots of out of print Shrox designs.

Tuesday, July 23, 2019

Semroc USS Andromeda KV-97, Part 1, Parts

As I mentioned before - 
The two main, smaller diameter body tubes are the thicker walled ST-7 tubing.
The other BT-50 style tubes look to be thicker walled ST-9 tubes.
When I got the parts last year, the decals weren't included - yet. The new production kits do have decals and embossed metallic trim.

Parts of interest:
A Midget style BNC-50J style nose cone
What do ya' know - An Odd'l Rockets Parachute!
In the center are some laser cut thick cardboard rings and trim pieces.
BIG Balsa wing fins.
Two round end tapered toothpicks. The original Estes kit had dowels.
In the middle bottom is an old style black fish paper coupler. There is a hole for the Kevlar tie.
On the far right is a clever system of fin and body tube alignment tools.

Well, I've Never Seen This Before!

Isn't it a "Right Of Passage?"
We've all cut our fingers with a hobby knife. Practice makes close! The more experience you have, the less we cut our fingers.

Years back at the Print Shop I heard a paste-up artist let out a yell. An X-Acto knife had rolled down the angled drawing board and stuck in her thigh! These Kevlar finger cots can't help a fast rolling knife.

I've been using an X-Acto knife since I was five years old. But then again our 1960s based toys involved unsupervised toy making hot plates and wood burning sets.

This product obviously comes from China. I like the photo: "Let's see if they work by dragging a sharp knife over a protected finger!"
I don't quite understand why the F, S, P and Ts are highlighted in yellow.
Before somebody corrects me, I have seen finger protection used in wood carving.
To see the Ebay listing: CLICK HERE

Monday, July 22, 2019

Semroc USS Andromeda KV-97 Background

This was the new standout kit from the 1975 catalog!
At over 43" it was almost as tall as the Saturn V! Painted an overall black with high contrast orange decals and metallic trim.
In the Estes catalog it is called simply the  "Andromeda". I don't know when the "USS" prefix was added. In 1975 the retail price was $4.95.

In the mid 1970s, I launched mine - once!
The main body was two 18" sections of thin walled BT-20 tubing. Even though there were balsa and dowel reinforcements down the body tube, it buckled and pinwheeled after it cleared the launch rod.
The new Semroc re-issue uses the heavier walled ST-7 (Centuri style) tubing. A great improvement!

Randy Boadway gave me kit parts at the last NARAM in August, 2018. I understand there were some hurdles getting the white water slide decals produced. Against the black paint, any decal would need a white undercoat to show up.

I have a real interest in this kit, I did most of the drawings and layout of the interior instruction pages.
The build starts tomorrow!
The kit is available now: CLICK HERE