No Thunder: a little bit different

[ECayemberg]

This build thread will be a little bit different than normal. Instead of detailing a “standard” build, I’ll detail only those items that are a little different than the norm.

No Thunder: what’s in a name?
The name has a two-fold meaning:

1. The components were purchased from Performance Hobbies as a “TCB Thunder”. I had some credit with Ken from an order that didn’t pan out, I remembered the TCB Thunder as a large, simple, sport flyer from days of old and thought it would be a fun build. Thunder kit: https://www.rocketryonline.com/jimball/jimball/construction/TCB/default.htm. Mark M.'s Thunder (top photo) of which has flown at the Bong lots of times in lots of years: https://tripoliwisconsin.com/meierm1/june13-4.html. When the kit arrived, I could instantly see that this kit was No Thunder! A little bit different #1: TCB kits used a nosecone that was just slightly shorter and had a different base than the Loc PNC-5.38L; instead I received a Loc nosecone. The Thunder had one section of 48” airframe with no payload section; I got a standard Loc 42” airframe, 20” payload, a coupler and a bulkplate. The fins were too small to be Thunder fins; they were more like Thoy Falcon fins. No complaints here, as most or all of the replacement items would be considered upgrades; nevertheless, this was No Thunder!

2. My 3 year old son developed a fear of thunderstorms this summer after a strong storm moved through one night. For some time afterward, he would ask every night before going to bed: “No thunder, daddy?” He’s gotten over it, but still is occasionally concerned with thunderstorms. After hearing that phrase every night for several months, it seemed appropriate for use.

Purpose/Goal:
Though 5.5” cardboard rockets are probably my favorite size for high power sport flying, I had no intention of building No Thunder so soon, as I recently built a similarly sized Loc Magnum:https://www.rocketryforum.com/showthread.php?30930-Loc-Magnum-Build&highlight=Loc+Magnum+build. However, at MWP-X rocket buddy Preston sells me an AMW K500 Skidmark for a nice price. Alas, we have A little bit different #2: check out the bass-ackwards thrust curve on this thing: https://www.thrustcurve.org/simfilesearch.jsp?id=1329; it is literally backwards from a “normal” slightly erosive Bates grain thrust curve. That low initial thrust of 320 Newtons calls for unusual measures to keep a 7’ tall 5.5” rocket under 14.38lbs loaded with motor. Since the K500 weighs 6 lbs loaded, the goal is to create a completed model, ready-to-fly, under 8.38lbs. While the Magnum would probably do just fine on a calm day; I’m a big fan of at least a 5:1 thrust:weight ratio.

A little bit different #3: Fin Construction Part I
The fins supplied with the “Thunder” kit were very nice aircraft grade ply, yet the shape was both smaller than desired and different from the original Thunder design. This gave me an opportunity to redefine the fins. I decided to use the fin design from an old friend: a scratch built 5.5” x 8’ rocket called Hot Topic that I built in 2000. Only this time, I wanted to lighten the fins. In lieu of the ¼”’ply fins on Hot Topic, the No Thunder fins are each constructed of 5 parts: a 3/16” Gatorfoam core, 3/32” Lite ply laminated to each side of the core, and the leading and trailing edges are capped by 3/8” poplar dowels.

Here's a brief photo essay of their assembly. First up, a fin pattern is developed. 3/8" is removed from both the leading and trailing edges, as they will be capped with the 3/8" dowels. Trace pattern onto the Gatorfoam core and the lite ply sides. Grain direction doesn't exist for the foam, but matters greatly with the lite ply (of the 3 ply's, the outer two run the longer length of the sheet, or along the fin leading edges).

The pieces were cut out and returned to the workbench; and here's your sandwich. Flip up the ply sides and you get the idea. The small holes in the foam form "glue rivets" during the laminating process.

One side of the foam is wiped with a damp cloth, and a moderate amount of Gorilla Glue is applied to both surfaces. Note that the water reacts with the polyurethane glue which causes it to expand. The motor water involved, the greater the expansion.

The pu glue is spread evenly until a uniform thin film is over each surface.

The same process is done to the other side of the fin, and both sides of the remaining fins. Masking tape is applied over the edges to make sure the laminations don't shift around, and the fins are stacked between two layers of heavy plywood and weighted down with ~100lbs. They cure for 36 hours before moving on.

After the laminations have cured, 3/8" poplar dowels are cut slightly oversized for the leading and trailing edges. The leading and trailing edges are wiped with a damp cloth, and the dowels glued to the respective edges once again using Gorilla Glue. Masking tape holds the dowels in place and ensures any expanding glue stays where I want it. Back in the weighted press to dry for another 24 hours. Here's the assembled fins before removing tape:

With the tape removed, you can see where the G-glue expanded around the dowl, yet didn't protrude beyond the plane of the fin sides.

That's all for now; I'll be back with A little bit different #4 and beyond shortly!

-Eric-

 

[CarVac]

What an awesome thrust curve. Is it a single long grain?

 

[dixontj93060]

Subscribed.

 

[ECayemberg]

What an awesome thrust curve. Is it a single long grain?

Two bates grains. As the nozzle throat is fairly small, the cores are as well, so the 2 grain AMW loads typically have slightly progressive inverted U shaped curves. This one is unusually progressive. If I had to guess, I'd say that the progressive curve is accentuated by slag deposited in the nozzle throat continuously decreasing the throat area.

 

[ECayemberg]

The fin laminations have now thoroughly dried, so let's move on to finishing. The root and tip edges were trued up by block sanding. Here's a shot of the tips:

A quick note here on materials: the fins are thicker than needbe; around .4" thick. I wanted to use lightweight materials that I have on hand without resorting to composites. I love composites, but in the spirit of a paper-and-plastic rocket, I'm trying like heck to avoid using them! I believe the 3/16" Gatorfoam could hold up to regular, non-mach flights without reinforcement of any kind; I just don't believe it would stand up well to landings, etc. The lite ply sides add additional durability and stiffness without adding significant weight.

The trio of fins came in under one pound: for reference, the root chord on the fins is 12" long.

A little bit different #4: Fin Finishing

Instead of filling, sanding, priming, and painting, covering the fins (and the remainder of the rocket) in Monokote, Ultracote, Oracover, or other heat-shrink model aircraft films saves time and weight. I've covered several paper/phenolic rockets in covering material in the past, and No Thunder seemed like another good candidate. Alas, we cover the fins.

Step 1: unroll Monokote, place fin on material, and cut out leaving ~1" overhang on leading, trailing, and tip edges.

Step 2: Apply film to fin surface using trusty heat iron. For flat surfaces, I prefer to make a solid pass down the middle of the object and then work the film out towards the edges. For you airplane guys, this is somewhat opposite from covering wings or other open bay structures where you tack and stretch. In my experience, tacking, stretching, sealing around the edges traps a lot of bubbles on solid surfaces. So again, start in the middle and work the iron out towards the edges.

Wrap the excess material around the edges and seal down well. One could trim the material at the centerline of the edges, but a full wrap around the edges is far less prone to lift up.

Repeat for the other side. If done carefully, the heat gun isn't really needed; I used it on the first fin, and skipped it after that. Fin complete: crappy camera flash ON:

Same fin, crappy camera flash OFF: reflection of laborer in the fin:

Next up, slotting and covering the main airframe; though it will wait a day or three.

-Eric-

 

[CarVac]

Too bad, but by combining different materials for your fin, you are using composites. Mwahahaha.

But nice Monokote finish!

 

[daveyfire]

Same fin, crappy camera flash OFF: reflection of laborer in the fin:

Nice striped shirt :grin:

The fins remind me of the new Estes Mega DRM fins in their construction: layered and strong, but light. Lookin good so far!

 

[ECayemberg]

Moving along towards booster completion...

A little bit different #5: nearly No Metal!

Metal, specifically steel, is dense. Therefore, where we can eliminate steel, we can save weight. In place of eyebolts are simple holes in bulkheads and knots in tubular nylon. Ends of the recovery harnesses are tied instead of using quick links. A fairly simple way of saving weight. As a quick example, here's the forward centering ring: 3/8" hole drilled, nylon passed through, figure 8 knot tied, the knot dipped in water and lightly coated in Gorilla glue.

A final note on minimizing metal: the only metal components on the rocket are: two T-nuts and associated bolts for motor retention, two #10-24 threaded rods and associated nuts/washers for the ebay, and three small pieces of .016" brass sheet on the nosecone for shear pins.

A little bit different #6: Adhesives

Three different types of adhesives are being used on this project: wood glue, polyurethane glue, and epoxy.

The forward centering ring is glued in place using plain wood glue and allowed to dry. Wood glue is used throughout this build where I'd rather have the glue contract (shrink) than expand.

The motor mount assembly is then glued into the airframe using Gorilla Glue, which is a polyurethane (p/u). Before applying a ring of Gorilla to the interior of the airframe, both the ID of the airframe and the OD of the centering ring are dampened with water. This is my favorite feature of P/U glue; the more moisture it contacts, the more it expands. The more it expands, the less you need to use. The less you use, the less weight you add to your project. I started using p/u glue when I flew R/C combat; to build a strong wing quickly, the foam core wing was sprinkled with water, p/u glue added to the spar slot, spar installed, and taped over with strapping tape. The p/u glue expanded to fill any voids and yet was confined to the taped over area: beatiful. Back to No Thunder construction, here's the motor mount Gorilla'd into place; note the foam! Note that the aft centering was temporarily installed for alignment, but not glued at this time.

Epoxy is used in only two places during the build; though it is strong, it is also heavy! I mixed one 8 gram batch to 1) secure the T-nuts on the aft centering ring, and 2) seal the external fin-to-body joint. Zap 15 minute epoxy dries clear and was therefore a great option to seal any gaps between the red fins and yellow airframe; note that this was not a structural fillet.

To be continued...

 

[ECayemberg]

Let's glue some fins! Before doing so, the fins are test fit in their slots. The fins' monokote is marked where it meets the airframe wall, and the monokote trimmed off at that point, exposing the fin tabs (wood bonds better than plastic film!). The fin jig used on a Magnum build earlier in the year is updated to accomodate the wider fins. Here, Mr. No Thunder confirms that we're nearly ready to glue some fins!

A little different #7: Woodpecker

But first, hit it with your woodpecker:wink:. The Top Flight Woodpecker is a tool that leaves lots of little holes in pretty much any surface that it runs over. For R/C aircraft, it gives hot air a place to go when covering a model, minimizing bubbles caused by trapped air. For rocket building, it creates voids so expanding glue may fill the voids, creating many glue rivets. Therefore, we steamroll the fin root with the Woodpecker trying not to poke our fingers while executing the process!

Note that there are many ways to accomplish the same task, I just find that using the woodpecker is uber-easy! Rivet ready fin root looks a lot like this (sorry, it doesn't show the holes in the foam well):

Like we did for the motor mount, the fin root and OD of the motor tube are dampened. The fin roots get a solid bead of Gorilla glue and are inserted. Gettin' jiggy with it; though it wasn't intentional, there are two fully and one partially heat-shrink film covered rockets in the background and Hot Topic that was referenced earlier in the thread.

After a few hours, the fins have a foamy fillet at the root; a very solid bond that doesn't require any further filleting! As mentioned earlier, the exterior fin-to-airframe joint is sealed with 15 minute Z-poxy; roughly 6 grams total was applied to the three fins/six fillets for non-structural aesthetic purposes. To finish the fin bonding, wood glue structural fillets were applied to the fin joints around the ID of the airframe. Here's a shot of the fully bonded rear end prior to permanently installing the aft CR (wish it would show the fin root foamy fillets, oh well).

Sticking with the theme, the aft centering ring was installed by A) dampening both surfaces to be bonded with a damp towel, B) adding Gorilla glue to aft edge of the fin tabs, OD of the motor tube, and ID of the airframe, and C) pushing in the until it contacted the aft edges of the fins.

After adding rail buttons, the completed booster section weighs a touch under 3.5lbs

-Eric-

 

[Nea_rocketman]

I have been thinking about using monokote to cover rockets. I have a bunch left over from my airplane days. Looks great I think I will go for it on my next build.

 

[ECayemberg]

I have been thinking about using monokote to cover rockets. I have a bunch left over from my airplane days. Looks great I think I will go for it on my next build.

Absolutely! I'm in the same boat; I have a lot left over from when people actually built r/c aircraft (instead of ARF'ing it). I now prefer to monokote/ultracote/oracover paper/wood rockets over filling, priming, and painting. I still paint glass or similar rockets, but to me, covering is much quicker and easier!

 

[ECayemberg]

Nothing too exciting here, so I'll quickly skim over a few steps.

I *always* seal the ends of cardboard tubes by soaking them in thin CA. When covering airframe in film, I also make sure to iron down the edges of the film to the ends of the airframe as well. This provides an additional barrier and hides the edge of the film from the airflow. If this step were skipped, the edge of the film could lift up a bit, allowing air under the film, which in turn makes the film balloon, peel, or tear off. After ironing down, #11 trims the material flush with the ID of the tube.

No Thunder shares an electronics sled with my Magnum. Twin Adept 22's mounted on opposite sides of the sled using shared hardware. Simple and effective; nothing crazy here.

You'll note in the photo above that only coupler bulk plates are used (no airframe bulk plates). That's because we installed a "stiffy" inside the tube coupler. I have trust issues with the thin Loc 5.54" couplers; plus the one included in this kit was creased in two places on one end. I created a "stiffy" insert by stripping the glassed phenolic surface off a scrap piece of zippered airframe and cutting a slice out of the length so it would fit the ID of the coupler. Here, my younger workshop elf fits the two pieces together.

Again with the Gorilla glue, the ID of the coupler and the OD of the stiffy are dampened with some high quality H2O, moderate glue applied, stiffy inserted. A balloon was inflated to ensure the stiffy pressed against the wall of the coupler, which made for a happy helper.

After that dried, the forward bulkplate was fitted with a section of tubular nylon and sparingly glued into the forward end of the coupler. The coupler was then installed into the payload section with the help of my friendly gorilla.

I've haven't had the chance to work on the rocket in the last few days, but we're nearing completion of this build already. Just need to drill a few holes, paint the nose cone, glue a ball in the booster, and take care of some shear pins.

-Eric-

 

[fyrwrxz]

Oh, I see how it is now. You come up with the excellent ideas, have your helper do all the dirty work, and then take the credit, eh?? He has that aspiring rocketeer gleam in his eyes-watch out Dad-you may be creating a monster...motor case lover! Nice build, sir and hats off to the workshop elf!

 

[chadrog]

Looks great Eric, love the look of the monocoat. Have you developed a quiet propellant for it?

 

[CarVac]

In my viewing experience (3 of them), Aerotech I600R's are noticeably quieter than similar sized motors (compared with the J500G and J350W).

Also, smokies tend to be quieter.

 

[ECayemberg]

Oh, I see how it is now. You come up with the excellent ideas, have your helper do all the dirty work, and then take the credit, eh?? He has that aspiring rocketeer gleam in his eyes-watch out Dad-you may be creating a monster...motor case lover! Nice build, sir and hats off to the workshop elf!

Indeed; both the boys are maniacal rocket boys! They're my helpers, and they can take as much credit for the efforts as they like!

 

[ECayemberg]

Looks great Eric, love the look of the monocoat. Have you developed a quiet propellant for it?

Thanks Chad! Sure, my smoky propellant hisses more than it roars, though I haven't made any in over 2 years (sparkies > smokies).

 

[ECayemberg]

In my viewing experience (3 of them), Aerotech I600R's are noticeably quieter than similar sized motors (compared with the J500G and J350W).

Also, smokies tend to be quieter.

Huh, I used to fly the I600R quite frequently, and never considered it a quiet motor:confused2: Either way, I like der big red flame!

 

[ECayemberg]

No Thunder is functionally complete; all that's left to do is add a few decals and paint the nosecone. This being the case, it was time to weigh the (mostly) completed rocket.

Masses:
-Booster section: 3.475lbs
-Payload section: (with electronics, batteries, main chute, and all the fixins): 2.731lbs
-Nosecone (unprimed, unpainted): 1.256lbs
-Nerf ball (anti-zipper device: yet to be installed): .113lbs
-Grand total: 7.575lbs.

Since the goal is to stay at-or-under 8.38 lbs, this leaves me with 0.8lbs allowance for nosecone primer and paint, and decals: I should be able to make it!

More pictures as soon as we cross the finish line.

-Eric-

 

[ECayemberg]

Little Bit Different #8: Nerf ball

Giant Leap has the Fireball, Shopko has the foam ball. I'm shamelessly stealing this idea from some clever students at the Rockets for Schools competition. For a few years, delay issues, wind, and material choice caused zippers on many of the student rockets launched. One team...either Madison West or Iron Mt. Michigan implemented these foam balls in their recovery system to help prevent zippers.

A utility blade was used to make a slit in the ball, passing from one side to the other. The cord was dampened, a bit of p/u glue applied, and the ball slid into place, so that as the recovery harness was pulled taught, the ball was near the top of the tube, preventing the harness from directly touching the airframe wall.

 

[dixontj93060]

Little Bit Different #7: Nerf ball

Giant Leap has the Fireball, Shopko has the foam ball. I'm shamelessly stealing this idea from some clever students at the Rockets for Schools competition. For a few years, delay issues, wind, and material choice caused zippers on many of the student rockets launched. One team...either Madison West or Iron Mt. Michigan implemented these foam balls in their recovery system to help prevent zippers.

Eric, what happens when an ejection charge lights near one of these foam balls? Seems like it might melt? (Hopefully no flames ). I have used a piece of pipe foam insulation wrapped in layers of duct tape and further cinched in place by zip ties. In that case, many, many ejection charges resulting in just a bit of blackening on the duct tape (white duct tape in the case shown below).

 

[chadrog]

Little Bit Different #7: Nerf ball

Giant Leap has the Fireball, Shopko has the foam ball. I'm shamelessly stealing this idea from some clever students at the Rockets for Schools competition. For a few years, delay issues, wind, and material choice caused zippers on many of the student rockets launched. One team...either Madison West or Iron Mt. Michigan implemented these foam balls in their recovery system to help prevent zippers.

A utility blade was used to make a slit in the ball, passing from one side to the other. The cord was dampened, a bit of p/u glue applied, and the ball slid into place, so that as the recovery harness was pulled taught, the ball was near the top of the tube, preventing the harness from directly touching the airframe wall.

Ballz for mini-type dogs work very well in smaller air frames too. Thanks Rex.

 

[blackjack2564]

Eric, what happens when an ejection charge lights near one of these foam balls?

That's why they call it a "FIREBALL" silly!

 

[ECayemberg]

Eric, what happens when an ejection charge lights near one of these foam balls? Seems like it might melt? (Hopefully no flames ). I have used a piece of pipe foam insulation wrapped in layers of duct tape and further cinched in place by zip ties. In that case, many, many ejection charges resulting in just a bit of blackening on the duct tape (white duct tape in the case shown below).

Tim,

I did think about this; worst case scenario, as CJ mentioned, we have a fireball. For this design, I'll place the e-charges just aft of the payload bulkhead. The ball will be on the opposite side of the main airframe, just above the motor, with all the recovery harness between. Most likely, I'll throw in a Top Flight chute protector near the payload end of the recovery harness as well, so that all the recovery components would be segregated from the charge.

Isn't napalm a byproduct of burning poly-foams:eyepop:?

-Eric-

 

[ECayemberg]

A little different #9: Simple D-I-Y decals

Let me start by saying that I have a lot of rockets outfitted with Stickershock decals; as you all know, they're great! But when I started out in high power, Mark wasn't around to feed me beautiful decals. So today, if the trim scheme of the rocket is super simple, I'll cut my own; anything complex, its off to Stickershock we go!

No Thunder has a very basic trim scheme, so I'll cut my own for this round. Here's how I do it.

1. For letters and logos, I print out two copies full-size on plain paper. Take one copy, tape the paper to trim Monokote and cut out using a scissors and/or #11 X-acto: simple!

2. Take the second copy, position on rocket and tape in place. For the letters, I mark the mid-height level of the letters (3" letters = 1.5" from either end). This mark corresponds with the mid-point between two fins. Before taping the template to the rocket, I cut off a 1" strip off the bottom of the template. Tape template in place, taking care to ensure that it is A) centered between the fins and B) on axis over the length of the airframe, and off we go.

3. Cut a small piece off the backing material of the letters (if we cut 1" off the bottom of the template, we need to cut less than 1" of the bottom off the backer.

4. Position the letter directly over the template. Once aligned, stick the backer-less portion solidly to the rocket; this "locks in" the decal's position.

5. Repeat for all letters until it looks like Manny's 18 and Life to Go before he doubled on the Elmers. At this point, all letters are essentially tacked in place, their aligment secured.

6. Take off the template, remove the sticker's backing material, and carefully press the unstuck portion of the letters into place.

7. Repeat for fin decals. Yes, I know that's lightning verses thunder, but how the heck do you picture thunder?

Once the decals were completed, No Thunder was placed alongside the Magnum for comparison; these rockets are the same physical size.

The nosecone was painted over the weekend, so as soon as the weather and camera cooperate, I'll post a photo of the completed model.

-Eric-

 

[chadrog]

Excellent technique with the lettering Eric, looks great! First flight Saturday?

 

[blackjack2564]

Eric....outstanding build. been saying for years ya can build'em strong & light at the same time!

I've done several cut and place decals myself...not hard at all & a good skill to learn. Yours look great.

Just wondering: after you glued the dowels to the fin edges, did you fill the gap with something or sand flush?
Or did the Monokote just stretch and cover the gap?

 

[ECayemberg]

Excellent technique with the lettering Eric, looks great! First flight Saturday?

Thanks Chad. First flight will likely be the TWA launch in February! I have lots of 3" motors to burn in 5.5" airframes in 2013!

 

[ECayemberg]

Eric....outstanding build. been saying for years ya can build'em strong & light at the same time!

I've done several cut and place decals myself...not hard at all & a good skill to learn. Yours look great.

Just wondering: after you glued the dowels to the fin edges, did you fill the gap with something or sand flush?
Or did the Monokote just stretch and cover the gap?

Thanks Jim! The more rockets I build, the more I "regress" towards simplicity! Just like your fine builds, KeepItSimpleStupid!

Gaps are not filled; the monokote bridges the gap of ~1/4" unsupported. I figure if we can push open bay film coverings 200mph+, then subject it to loading in pylon turns, it should hold up well to the straight line speeds that this bird will see. If not, we'll have some nice red confetti as part of the special effects of the flight!

-Eric-

 

[ECayemberg]

Whoa, just realized that I never posted a photo of the completed rocket. She's all ready to go, maiden voyage to be on the AMW K500 Skidmark on February 16th at the Bong. Hope to get some photos, will post them here if I do!

-Eric-