Mercury Engineering 3" Diam. School Rocket Build, Part 6, Chrome Trim Fins, Comparison

Here's an old post that never got, well . . . posted!
This shows the difference when adding some Monokote chrome trim.
While Bill at BMS wanted a red, white and blue catalog picture, I added chrome trim after the pictures were sent out.
I have a little history with this kit, I drew up the instructions for the 3" School Rocket versions.

This 3" diameter, 28" tall model is one of the best values out there at $23.95 for the 24mm version.
BMS has also added a 29mm version with an optional payload section.
To see the 3" diameter School Rocket,
CLICK HERE - Look for the School rocket listing along the top. Go to the 3" diameter 24mm or 29 mm versions.

The fins got two tapered strips, on just one side of the fins.
Simply a judgement call, I though strips on both sides would be too much.

Here's the before and after the chrome was added.
Both schemes work, but the chrome trim really sets it off.
NOTE: The very tips of the chrome stars want to lift. The stars won't come off, but you can feel them with your fingers.

I remember the Centuri catalog from 1973. Simple bands of chrome added a lot to the Flutter-By, Groove Tube and Bandito models.

Mercury Engineering 3" Diam. School Rocket Build, Part 7, Launch and Follow Up

Here's a picture of the first D12-3 launch of the 3" School Rocket, before the chrome trim was added. The picture is from the December 5th N.E.F.A.R. launch. Boost was arrow straight all looked good until ejection.

The Kevlar loop broke through the upper centering ring and the rocket came down in two parts.
This was a fluke - how could a shock cord break through a 1/8" thick plywood centering ring?
The nose cone descended on the 18" parachute and landed softly. No damage to the nose cone.

The body tube nosed in and hit the ground!
I thought the tube would be crimped and probably beyond repair. THERE WAS NO DAMAGE to the tube, except for some very light scratches. This is a strong tube, it looks to be about 1 1/2 times the thickness of a BT-60 with a .070" wall.
Looking inside the tube with a flashlight, the centering ring had broken through between the two tie-down holes. I had hoped to fly it again with an E9-4 but couldn't with the needed repair.

I called Bill at BMS and told him what happened. He agreed that the ejection charge had to of been a strong one. He didn't have this problem with his prototypes. While this pre-production model had a lightweight ply centering rings, the production kits will get heavier plywood centering rings.
I used an Estes style tri-fold mount for the repair.

UPDATE: The 3" School Rocket has flown a few more times with the E9-4 engine. It gets to a good, but manageable altitude, perfect for demonstrations. Slow off the launcher on the longer burning E9. This model is now a favorite, I have to buy more engines!

Again, this kit retails for $14.95!
At 28 3/4" tall it's almost 10" taller than the Estes Big Daddy - at half the price!
This one is highly recommended. You'll find it on the BMS website, CLICK HERE

Mercury Engineering 3" Diam. School Rocket Build, Part 6, Chrome Trim Comparison - Finished

Simple, tapered chrome trim strips were applied on the right side of the fins. For me, trim on both sides of the fins would have been too much.







On the left is the before,
on the right is after the chrome trim.

Monokote Trim is an easy alternative to complex masking and a vibrant way to trim a rocket.
Look back on some Centuri sport models in the 1972 catalog for ideas - CLICK HERE.

You can overdo it, though.

Mercury Engineering 3" Diam. School Rocket Build, Part 5, Stars Placement

Once again, the blogs posts came in out of order! Early this morning, #6 was posted. #5 was way down in the older posts.
Here's #5 answering the question posted by Neil W.



The star templates were taped to the chrome Monokote trim sheet and cut around with a new blade.

In the end I didn't use much of the chrome sheet. Many of the smallest stars were cut from the areas left between the larger stars.





Set the stars in place using the tip of your hobby knife. Don't place any stick on decal using your fingers.
Using just the knife tip leaves the underside of stickers cleaner and less likely to leave dirt and raised bubble areas.





The largest stars were purposely set over the nose cone / body tube seam.
Slide the nose cone all the way in before setting down an overlapping star. Burnish, then cut through the joint.

It just takes a moment to turn the cone to line up the star tips before flight.

Mercury Engineering 3" Diam. School Rocket Build, Part 4, Paint and Chrome Trim

The build is very straight forward and easy.
The 3/16" launch lug is glued and centered over the pre-etched lines on the body tube.

Bill asked for a simple paint scheme, Red, White and Blue.
Here's how the model looked for it's first flight, before I added the chrome trim.

I wanted to add some random chrome stars. These wouldn't be perfect stars. Cutting perfect five point stars isn't easy.
I always like the star decals on the old Estes Patriot and Shark models.

Some rough stencils were drawn up on card stock for templates.

These were cut out and taped onto the tube to get a better idea of the placement.

They start big on the top and get smaller towards the bottom.
There will be four lines of stars roughly following this pattern.

Mercury Engineering 3" Diam. School Rocket Build, Part 3, Fin Alignment

The fin tab doesn't reach all the way to the engine mount tube. When glued into the body tube notches it is plenty strong for D and E engines.

Bill (BMS) told me the kit might be offered with longer fin tabs as an option. Email Bill and let him know if your are interested in the longer TTW fin tabs.
The shorter fin tabs fit onto a 3" wide balsa sheet. A 4" wide balsa sheet would have increased the price of the kit.

On the left you can see how the glue was applied before sliding the tab into the body tube.

TIP: When looking over the trailing edges the fins should be in a straight line.Here I'm looking across two opposite fins to check their alignment. You can do this visual alignment with four fin models, not three fin rockets.

Mercury Engineering 3" Diam. School Rocket Build, Part 2, Engine Mount

The engine mount assembly is straightforward, no surprises here.
The engine hook slot is laser cut, the centering rings glue onto the etched lines on the motor mount tube.







The Kevlar shock cord is tied with a bowline knot through the two holes in the upper centering ring.
You'll use the bowline knot a few more times in the model assembly.







The end of the engine mount tube end is flush with the 3" outside tube edge.
The spring steel engine hook overhangs the end by about 1/4".

Mercury Engineering 3" Diam. School Rocket Build, Part 1, Parts

Everybody has rocket favorites, this is one of mine.
If you are a Big Daddy fan, you'll want to check this one out.
The 3" School Rocket is now available on the BMS website - CLICK HERE
There is a pull down menu at the center top, look for "School Rockets"
The instructions I drew up are there too -

The Mercury Engineering (BMS) 3" School Rocket is a big, 3" diameter stubby model built for D12-3 and E9-4 engines.
One of the main features of the model is no hobby knife or cutting is needed for construction!
(Well, except for the parachute) You'll only need wood glue and tape.
All markings for the centering rings, launch lug position and engine hook notch are already laser etched in the tubes!

I didn't know that Balsa Machining Service had bought Mercury Engineering. Bill had called me a while back and asked if I'd be interested in drawing up the instructions. I would also be involved in some flight testing.

The nose cone is BIG at 3" diameter and 11" long! Certainly a highlight of the kit. It's a bit loose in the body tube and needed two wraps of masking tape for a better fit.
The body tube is 11" long with laser cut fin slots.
The Kevlar provided is 750 lb.
The plywood centering rings have two holes in the upper ring for the Kevlar tie.
A 1" long engine spacer is included to allow for D12 and the longer engine E9 flights.
Four fins are 1/8" thick balsa, laser cut and through the wall. On this standard model the tabs don't reach or attach to the engine mount tube.

It was a surprise to find my design parachutes included in the kit!




This kit will probably be upgraded by many to use 29mm engines. Bill said he might offer a longer tab through-the-wall fin that'll glue to the engine mount tube. But that availability will depend on customer feedback.

The biggest news is the retail price - $14.95!!!
You'd normally pay more for that nose cone alone!

This is probably be the best bargain in rocketry today!

Mercury Engineering 3" Diam. School Rocket Now Available!

Here's the first page of the instructions I produced for the

BMS Mercury Engineering 3" SCHOOL ROCKET

To see the kit: CLICK HERE Look for "School Rockets" along the top of the first page.
For the instructions: CLICK HERE
The kit is now available and worth waiting for. A blog build of this model will start in a few days.
A great value and great demonstration rocket for only $14.95!

If you need instructions produced for your rocket kit, contact me at: oddlrockets@bellsouth.net