Performance Rocketry 4-inch Nike Smoke (Part 5 - Finishing Up!)





Being the first all fiberglass rocket I've ever finished, I had no idea if the method I had been using on paper tube rockets would yield similar results.  So I decided to just proceed as I normally would an pay close attention to see if one or more of the steps in my standard needed modification.  As it turned out, the same technique worked out fine.

 

 

Figure 1 - Dupli Color High Build Primer coat

Although the fiberglass obviously was devoid of any spiral lines, there were still small dings and scratches as well as a couple of sanding marks where I removed the mould seem on the nosecone.  For this reason I went ahead and gave it two-three good heavy coats of sandable filler primer and then sanded all the surfaces down to a thin, very smooth coat.

 

Figure 2 - Fluorescent paint for the fins

Probably the biggest potential "gotchya" in the finishing stage was that I wanted to use yellow and red fluorescent paint for the fins.  Fluorescent paint MUST be put down over a clean WHITE primer.  If you put it down over any other base color, you won't get the fluorescent "pop" your expecting.  So as with all of my previous kits, I laid on a nice heavy coat of Krylon flat white primer and sanded it with very fine sand paper just enough to knock down some but not all of the tooth.

Figure 3 - Applying the fluorescent fin color

Once the white primer base had dried completely, the yellow and red fluorescent fin colors went on beautifully!  I applied 3 coats to each fin (1 yellow fin and 3 red fins).  Once that was dry, the only thing left to do was to apply the single vinyl "UNITED STATES" decal, and the model was done.

Figure 4 - The completed "Nike Smoke"

This kit was both fun and challenging.  It was not particularly difficult to build but it presented several fun challenges (such as adding the av-bay) and I learned quite a lot about building a high power, all fiberglass rocket.  I look forward to it's maiden flight when I attempt my level 2 cert on a J3??.

Performance Rocketry 4-inch Nike Smoke (Part 4 - Drilling av-bay vent holes and installing shear pins)

Figure 1 - Drilling shear pin and av-bay vent holes

Then final task before painting is to drill the vent holes for the altimeters and also some smaller holes for shear pins. Figure 1 shows the use of the Dremel for drilling the smaller 1/16" shear pin holes. The larger drill press was used to drill the 1/4" av-bay vent holes visible on the right.  I've explained the reason for the av-bay vent holes but not the use of shear pins, so let me remedy that.

High power rockets are often built with stronger heavier materials than model rockets and the nose cone on the Nike Smoke is a perfect example it's built entirely from fiberglass and with the 10oz of weight in the tip, it probably exceeds 2.5lbs.  When the rocket is launched it will gain speed and momentum quickly under the boost of the motor.  When the motor burns out the rocket will begin to decelerate rapidly.  Since there is more drag on the airframe and fins that portion of the rocket will want to decelerate faster than the more streamlined nose.  This phenomenom can lead to premature seperation of the nosecone from the airframe.  To prevent this, small shear pins are inserted through the airframe and nose cone shoulder that will "lock" the nose cone to the rocket body through the coast phase of flight.  Because the shear pins are small, they will ultimately give way ("shear") with the much larger force of the ejection charge when its time to deploy the recovery mechanism. 

Figure 2 - 1/16" styrene rod (from Evergreen)

 

Some people prefer to use small nylon screws for shear pins, and they work fine for many people.  My own opinion is that properties of nylon tend to make it tear rather than break in shear.  Plus nylon screws can be a tad pricey when you figure your going to go through 3 or 4 every flight.  What I like to do is fabricate my own shear pins out of 1/16" styrene rod.  Styrene is more brittle than nylon and will therefor break cleaner in shear with less force.

Figure 3 - Making shear pins is easy



Making shear pins is a snap.  All you need is a package of 1/16" (or whatever diameter you want your shear pins to be) styrene rod, a piece of brass strip, a piece of wood (so you don't put burn marks in your kitchen table) and a small candle.  Heat up the tip of the brass strip on the candle, place it on the wood, and lightly push a piece of the styrene rod onto the hot metal.  The styrene should melt and fan out to make a small head (like a nail).  Lift the rod, cut to the desired length and repeat.



Figure 4 - A finished shear pin

Figure 4 shows a close up of a finished shear pin.  Depending on the size of your model you may wish to use slightly larger styrene rod.  It all depends on the forces you expect to encounter.  If you need more strength, you have the option of using larger dia rod or increasing the number of pins.  You will want to consider the use of shear pins when you calculate your ejection charge size.  Most of the calculators I've seen out there have inputs for number and size of shear pins used.

Figure 5 - It's easy and inexpensive to make your

own shear pins

Using the method described above, you can make dozens of shear pins in a single evening for pennies.

Performance Rocketry 4-inch Nike Smoke (Part 3 - Fabricating a small avionics bay in the nosecone)

This kit was originally designed to use only motor ejection to deploy the recovery system.  This means that the only way to ignite the ejection charge is to place it at the upper end of the motor where it is ignited at the end of a pre-determined delay.  Now there is nothing wrong with motor ejection and in fact it is the method used in almost all "model" rocket flights since the ejection charge is built into nearly all model rocket motors.

However, with the advent of reliable onboard electronics, high power rockets are increasingly using altimeters to ignite the ejection exactly at apogee where stresses on the rocket are at their minimum.

To do this, altimeters now typically include one or more firing circuits that are connected to a small onboard battery source and a model rocket motor igniter.  The igniter is placed in contact with a small amount of black powder in some sort of containment canister.  When the altimeter detects apogee has been reached it closes the firing circuit and ignites the ejection charge.

Unfortunately the Performance Rocketry Nike Smoke does not include a separate avionics compartment in it's design.  However the shoulder of the large Nike Smoke nosecone is about 4 inches long which if modified, would be big enough for not 1 but 2 onboard altimeters (1 could be used as a back-up) and still leave plenty of room for an eye bolt to fasten the recovery system to. 

 

 

Figure 1 - Original Av Bay concept sketch

 After coming up with a preliminary design (see Figure 1), I began work on the forward bulkhead that would have to receive the threaded screw-eye.

 

Figure 2 - 1/2" Plywood bulkhead laminated to fiberglass

bulkhead from kit

Just like the centering rings, I didn't feel I would get the rigidity I was looking for by using the fiberglass by itself.  I also wanted something I could mount sled rails into on the av-bay side of the bulkhead, so I laminated a 1/2" plywood bulkhead to the fiber glass bulkhead as shown in Figure 2.

Figure 3 - T-Nut installed in bulkhead

 In order for the av-bay to function, the load bearing bulkhead is moved forward and will receive and anchor a 3/8" threaded eyelet.  However since the threaded eyelet will have to be removable to gain access to the av-bay, I installed a t-nut on the forward side of the bulkhead (see Figure 3).

Figure 4 - JB Weld used to permanently secure T-Nut

The T-Nut was then permanently secured in place with JB Weld (again due to its increased adhesion to metal).  Next up will be to add any nose weight to the the rocket since that will be sealed off when the forward bulkhead is installed.

 

 

Figure 5 - Bird shot mixed with JB Weld

After doing some computations in RockSim and determining the largest motor I would ever want to fly in this rocket ( a full K), I decided to add about 10 oz of nose weight.  To do this I mixed 8 oz of lead bird shot into 2 oz of JB Weld which made a gooey heavy sludge - PERFECT!

Figure 6 - Nose weight in tip of nose

I then pushed the sludge into the tip of the nose with a long dowel and then added a bit more JB Weld as a cap.  Hopefully this nose weight is going nowhere.  Now back to the av-bay.

 

 

 

Figure 7 - Laying out the altimeter sleds

 

The altimeters themselves are fastened to wooden sleds each of which will slide onto a pair rails that hold them secure during the flight.  This will be easier to understand in the pictures that follow.  Anyway, careful planning has to be done when laying out your altimeter board so that 1.) Everything will fit and 2.) the switch that turns that altimeter on and off is accessible through the vent hole.  The vent hole is a small 1/4" or so hole on each side of the av-bay that vents the outside air pressure into the av-bay so the pressure based sensors on the altimeter can determine the altitude.

 

 

Figure 8 - The completed Raven sled

I chose two different altimeters for this project.  A "Raven" altimeter which includes separate accelerometer and pressure based altimeters on a single board.  The 2nd altimeter is a "Stratologger" altimeter from Perfectflight which is solely pressure based.  Each altimeter will be fastened to it's own sled and wired to it's own switch and power source.  This makes for a truly redundant system.
When completed the altimeter sleds look like the pictures in Figures 8 and 9.  The push button on/off switch for the "Raven" sled can be seen in the lower left corner of figure 8.  This switch on each sled is the switch that must be reachable through the vent holes in order to turn on the altimeters prior to flight.  The ejection charge wires connect to the altimeter at the terminal blocks.

Figure 9 - Showing the battery mounted on the underside of

the sled.

 The batteries for each sled are mounted on the opposite side of the sled in order to keep the sleds under 4" long.  Other configurations you may see, where length is not an issue, will put the battery adjacent to the altimeter.  Also visible in Figure 9 are the sled "rails" which are aluminum tubes that will slide over threaded rods in the av-bay that will hold them in place.

Figure 10 - The entire av-bay assembly prior to

installation

Figure 10 shows the entire av-bay assembly prior to installation in the base of the Nike nosecone.  At the bottom is the forward bulkhead and you can see the 3/8" eye bolt that passes through the center of the av-bay and threads into the T-Nut mounted on the other side.  Also visible are the four sled "rails" upon which the altimeter sleds will slide and be locked into place by the aft bulkhead which is held on by 4 wing-nuts.  The terminal blocks receive the +/- leads from the altimeter firing circuits on one side and igniter leads on the other.  The igniter is inserted along with the black powder ejection charge into the white canisters also visible.  Once again everything is redundant.  Each altimeter is connected to it's own separate ejection charge.

Figure 11 - Both primary and backup altimeters installed in the

av-bay

Finally in Figure 11, you see the completed av-bay with both altimeters installed.  It's a pretty tight fit and it required more than a little planning and extra work but having the opportunity to use electronic  ejection on this rocket makes it well worth the effort.  The fact that there was room for redundancy was a bonus!



Performance Rocketry 4-inch Nike Smoke (Part 2 - Installing the Motor Mount Assembly, Attaching the Fins and Installing the Rail Buttons)

The next step was to install the motor mount assembly into the body tube. Now since the fin tabs on this model were fairly short, there was a lot of play as to how far into the rear of the rocket I could install the motor mount. The decision here is whether you want the motor retainer to be completely recessed into the airframe which has the single advantage of allowing the rocket to stand on its own. The disadvantage is that it leaves a large lip of un-reinforced body tube exposed to potential landing damage if the bottom impacts the ground very hard.  Conversely, if you let the motor retainer stick out past the bottom of the rocket, you are better protected against hard landings but the rocket will likely not stand on its own without some kind of display stand holding it steady.

 

 

Figure 1 - Installing the motor mount assembly

As figure 1 shows, I chose to let the motor mount stick out past the end of the rocket for three reasons.  1.) I'd rather build a display stand than risk cracking the bottom of the airframe on landing.  2.) It keeps the heat of the motor thrust further away from the airframe, and 3.) I just like the aesthetics of the protruding motor retainer better.


Figure 2 - The Nike Smoke fin

Figure 3 - Nike Smoke fin cross-section

(from G.Harry Stein's drawing)

The next step in construction was the attachment of the fins.  The fins on this kit were very nicely done and much closer to scale than other 4 inch Nike Smokes on the market. As figure's 2 and 3 show, Performance Rocketry did a nice job getting the bevels correct.  Two additional task for this step were widening the fin slots a smidge and shortening the fin tabs by about 1/4".  This allowed them to insert into the fin slots and seat nicely against the motor tube.



Figure 3 - Attaching the first fin

I chose to use JB Weld epoxy again here.  For one, I wanted the heat resistant properties JB offers for the glue joint on the base of the fin tab where it contacts the motor tube and secondly, although I certainly didn't need it for the fillets between the root edge of the fin and the airframe, I just didn't feel like messing with two different epoxies.  Ideally, I probably could have used something like West System or some other slow cure, high strength epoxy, but I think the JB is up to the job and I'm not that concerned about the extra few ounces in weight.

Figure 4 - Attaching the remaining fins

The three remaining fins were attached one at a time allowing several hours between each one for the JB Weld to set up.  Once all the fins were attached, it was time to install the rail buttons.

Figure 5 - Rail button with standoff

The Nike Smoke has a unique nosecone that at it's widest point is larger in diameter than the airframe.  This necessitates that use of "standoffs" for the rail buttons so that the nose cone won't bind on launch rail when the rocket is on the pad.  I opted to use 1/2" nylon spacers I found at Ace Hardware for the job.  I also had to get longer screws so that the threads would get some "bite" into the plywood centering rings I was using as anchor points. 

 

 

 

Figure 6 - Rail buttons installed

In figure 6 above, you can see the rail buttons installed and tapped into the built up centering rings.  One design concern I have here is if I have enough seperation on the rail buttons.  I'd like to have had another 6" but then I would have had to use a T-Nut epoxied to the inside of the airframe and I really didn't want to do that.  If this configuration does not work for some reason I can still go back and move the upper button, but we'll try this first.

 

Next up is the modifications I made to the Nosecone of the rocket to accomodate a small Av-Bay.  This was by far the most complex and time consuming part of the build, so it deserves it's own entry.

Performance Rocketry 4-inch Nike Smoke (Part 1 - Introduction, Parts Orginization and Engine Mount Construction)

Nike Smoke on launcher

 

The Nike Smoke program was developed to study high altitude wind patterns to aid in the design of larger rockets.  After boost, when the rocket begins to decelerate, it would begin to vent a smoke producing chemical into the atmosphere from a tank located in the oversized nose of the rocket.

Smoke Trail Measurement

 

Data plot of smoke trail from analyzing the camera footage

 

The chemical would react with the air and produce a persistent "smoke trail" that would be visible to cameras and measuring equipment on the ground.  By tracking the speed and direction of the smoke trail as it drifted in the various atmospheric winds, engineers could generate wind models and gain better understanding the crosswind forces acting on high altitude rockets.

If your interested in learning more about the Nike Smoke program, take a look at the following video:

NASA: Smoke Trail Wind Shear Measurements

G. Harry Stein Nike Smoke scale drawing

My Performance Rocketry 4-inch, all fiberglass Nike Smoke was originally supposed to be my Level-1  NAR High Power Certification rocket.  However, at some point during construction, I determined that the finished launch weight of the rocket was going to be in the neighborhood of 8lbs!  While I could probably eek a pretty anemic flight out of an I motor, this rocket really wants a nice easy lifting J, and so I decided to use it as my Level-2 rocket instead.

Getting an idea of the size of the kit

This was a loooooong build for me.  It was my first all fiberglass rocket and my first high power build in over a decade.  I also made a major modification to the design as I will detail below.  I added a small avionics bay in the shoulder of the nosecone to allow for electronic deployment.  This added significantly to the time and complexity of the build.

Figure 1 - Kit contents plus a few things not included in the kit

These kits are "bare bones".  They only include the main structural components: Body Tube, Nosecone, Nosecone bulkhead, Fins, Motor Tube and Centering Rings.  Everything else (recovery hardware, shock cord, rail buttons, etc...) must be purchased separately.  Still the kit was a pretty good value and being constructed entirely of fiberglass, if built right, it should last for many, many flights.

 

 

Figure 2 - Centering ring reinforcement

The kit came with 2 fiberglass centering rings which I augmented by laminating them together with 2 1/2" plywood centering rings.  This was done for both rigidity and also to allow for the tapping into the rings for the rail button launch guides.

 

Figure 3 - Centering ring sizing with sanding drum

The fiberglass (and also the plywood) centering rings required a bit of sanding on both the outside and the inside of the rings to get an ideal fit.  I used my sanding disc for the outside sanding and for the inside sanding, I purchased a set of sanding drums.  These made sanding the now 1/2" thick centering rings much easier. 

 

Figure 4 - Marking the motor retainer flange holes

I decided to go with Aeropack flanged motor retention, so the holes for the flange piece had to be marked and drilled.




Figure 5 - drilling the motor retention flange

holes

The flange bolts were 1/8" so I was able to use my Dremel to drill the flange holes.  There are six holes in all, so I went pretty slow and checked the alignment between each hole to make sure everything was lining up.

Figure 6 - Motor retention flange attached.

Another thing to watch out for here besides the flange holes not lining up is that the flange has to be perfectly centered on the inside hole of the centering ring.  If it's not, you will end up with a small "lip" of the motor tube interfering with the motor case when you try insert it into the rocket.  All-in-all, this step went very smooth considering all the things that could have gone wrong.

 

Figure 7 - Fillets using JB Weld

After the motor retention flange is attached, the centering rings can be epoxied to the motor tube.  Because of the possibility of high heat transferring from the outside of the engine case to the motor tube, I elected to use JB Weld steel reinforced, high temperature epoxy for both attaching the rings and for the reinforcing fillets.  This epoxy is slightly heavier than standard epoxy, but I think the extra temperature margin it provides is worth the weight trade off.

 

 

Figure 8 - Hole for shock cord retention hardware

Once the epoxy for the centering rings had dried, it was time to drill a hole for the 1/4" stainless steel shock cord retention eyelet.  My first attempt (shown in Figure 8 above) was too close the motor tube for the nut to fit, so I had to plug that hole (with JB Weld) and drill a new hole a bit more centered in the ring.

 

 

With the hole corrected, the eyelet was attached and the nut permanently glued onto the threads.  I used JB Weld here too, not because this area will see a lot of heat, but because JB Weld adheres very well to metal surfaces.

Well that about wraps it up for the motor mount assembly.  The next step is installing the motor mount into the main body tube and attaching the fins which will be "through the wall" and anchor to the outside of the motor mount tube.

Estes Mosquito ( #0801) Building Notes and Finished Model Pics

 

Initially released as part of the original introduction of the "Mini-Brute" line of rockets in the Fall 1971 catalog, the "Mosquito" was one Estes longest running kits.  At $0.49 and featuring a whopping 3 parts in the kit bag (a body tube, a tiny balsa nosecone, and a small strip of balsa), it would also perennially be Estes' smallest, simplest and least expensive kit until it was finally discontinued in 2003.

2011 Re-release as a "combo" kit with the "Mega Mosquito"

2012 Re-release as a seperate kit (#1345)

In 2011, the Mosquito re-appeared as a "combo" kit with it's much larger big brother the "Mega Mosquito".  In 2012 it was once again available as a separate kit, albeit sporting a new kit number (#1345).

 

As far as personal history with this model, the Mosquito has the distinction of being the very first model rocket I ever saw launched! (well sort of...)  Back in 1977, I was attending Lexington Jr. High School in Cypress, CA and was getting back into model rocketry with my friends: Steve Perkins, Geno Torretta(sp?)  & John Lister.  Steve's grandfather had a small cabin on a nice flat peice of land somewhere around Twentynine Palms, CA and had granted us permission to use it as a base of operations for flying.  For weeks we worked feverishly on building up several kits and prepping, testing (and re-testing) our launch equipment for our first ever rocket launch... I will never forget that day... 

 

We had the following rockets (at least that I recall):

1. Estes Alpha (from the starter kit)

2. Estes Constellation

3. Estes Avenger

4. Estes Mosquito

5. And a home built rocket that my dad made from a Christmas wrapping paper tube and spare parts.

 

Anyway, after arriving at the cabin and discussing our options, we decided to start small, so the Mosquito was first up.  We carefully loaded the motor and attached the clips.  Continuity lamp was go... 5...4...3...2...1...pffffft!  NEVER SAW IT!  It just dissappeared before our eyes like a David Copperfield magic trick.  We never saw the Mosquito again...

 

What a dissapointment!  Never having seen a launch before, I wasn't sure what to expect, but that was definately not it!  Fortunately, the other larger rockets were much easier to follow and our faith in the hobby was restored, but the Mosquito will always be a memorable rocketry momment for me and therefore is one of my sentimental favorites.

Figure 1 - Cutting out the fins

 

Construction-wise, there isn't much to the Mosquito.  As mentioned in the introduction above, this was Estes simplest kit.  Still, I wanted it to look nice so I did the usual Elmers wood filler putty treatment and sanded them all down smooth.  The only potential "gotcha" here is that due to the tiny size of the fins, care must be taken not to oversand.  Any slight differences in the fin size or shape due to sanding irregularities is going to be noticeable.

 

Figure 2 - Filling the body tube seam

 

Filling the body tube seam was no different than on any other rocket, just on a much smaller scale.  And a lot less sanding... I like that!

 

Figure 3 - Glueing on the nosecone and marking

the body tube for the fins.  

Since the nosecone is glued in place for this rocket, I wanted to eliminate the seam between the body tube and the nose cone.  This was accomplished with a slightly thicker mixture of the Elmers wood filler and some fine grit sandpaper. 

 

Figure 4 - Estes Tube Marking Guide (#302227)



As a side note, this rocket was my first opportunity to try out the new Estes Tube Marking Guide.  These consist of 2 stair-stepped circular peices with markings for a 3 or 4 fin configuration and a "combo" tool for measuring tube length, marking the lines on the body tube and a jig for holding one fin at a time for glueing (see Figure 4).  All in all I like tube marking discs but for some weird reason they don't have a guide for BT-70 tubes.  An oversight?  As far as the "combo tool", I still prefer a door jam for getting straight tube lines and the Estes Fin Alignment Guide (#02231) is a bit more useful to me since I can attach all my fins at once.  However for going to a friends house to build, or doing field repairs, it's a good functional tool set that fits easily in your range box.

 

Figure 5 - Fin attachment

Decided to go "old school" on the fin attachment due to the tiny size of the fins.  One at a time, and rotate.  Fillets were done with 5 minute epoxy.

Figure 6 - Dupli-Color Filler Primer

Good ol' Dupli-Color "High Build" filler primer followed by a nice coat of Rustoleum white "Ultra-Cover 2X Primer".  Using white primer over the grey filler primer is done for two reasons:  1.) it provides a 100% compatible base for the color coat (no risk of crackling or adverse reactions), 2.) a white undercoat is a much better base for light colors such as yellow.  The underlying white really allows the lighter color to "pop". Whit also allows lighter colors to cover with a much thinner coat than a darker undercoat will.  As far as brands go, I opted for the Rustoleum over the Krylon for this model due to the color choices available at the time.  I wanted to paint the model in the 1970s era Marigold and Black scheme and Marigold was only available in the Rustoleum.

 

Figure 7 - Completed model on display

This was fun quick build and having the Mosquito back in my collection just feels good.