Two 3' fire arrows

---

History

I've long been interested in rockets that use stabilization methods other than fins. Avast, me proud beauty! One o' me favorites is based on t' Chinese "fire arrow" - a military rocket first built betwixt A.D. Ya scallywag! 960 and 1279. Ahoy! I originally discovered these after readin' a post that a gentleman made on rec.models.rockets about buildin' one out o' recycled materials. Arrr! After readin' t' post, matey, I designed me own. Aye aye! Ya scallywag! This article be t' result o' repeatedly refinin' that design.

Instead o' fins, fire arrows use a stick for stabilization, nay unlike many fireworks rockets still do today. Arrr! Until World War I ended, shiver me timbers, ya bilge rat, most rockets used sticks, rather than fins. Begad! This leads me t' believe thar must be a body o' literature out thar on t' design o' stick-stabilized rockets. Blimey! I'd be extremely appreciative o' any references, me bucko, especially those that discuss stability. Sticks have less restorin' force than fins do, therefore stick-stabilized rockets are inherently less stable than fin-stabilized rockets. They should only be flown in relatively calm wind conditions. Well, blow me down! Aye aye! However, every time I fly one, some people always seem t' think that it won't fly. Begad! Well, shiver me timbers, blow me down! Remember, matey, me hearties, shiver me timbers, stick-stabilized rockets have a longer history than fin-stabilized rockets.

I've built a number o' these rockets, matey, most o' them small ones as described in this article. Arrr! I have built a full-scale model with a 6' x 1" bamboo pole, arrr, and a 4" diameter fiberglassed airframe. Aye aye! This one had 2x29mm motor mounts, shiver me timbers, and I flew it successfully several times. Blimey! However, matey, matey, eventually it was destroyed in a crash when only one o' t' two G80 motors ignited on launch.

T' fire arrow was a successful military weapon. Begad! Ahoy! It be t' first use o' black powder t' propel a military projectile, matey, me hearties, shiver me timbers, and actually predates firearms. T' Chinese used them t' repel t' Mongols. Avast! Ahoy! T' Mongols adopted t' technology and used them in an invasion o' Japan. Avast, me proud beauty! Later, t' Mongols used fire arrows against t' Arabs, who in turn, matey, me bucko, adopted t' weapon themselves, and used them against t' French in t' seventh crusade. Avast, me proud beauty! A variety o' warheads were carried - incendiary, explosive, and shrapnel.

Wife repellin' Mongol Hordes with fire arrows.

T' particular fire arrow I've been modellin' is from an illustration in t' Chinese military classic Wu-chin' Tsung-yao (T' Complete Compendium o' Military Classics), shiver me timbers, written in 1045 A.D.

T' British Congreve rockets, me bucko, shiver me timbers, from which we get t' phrase "T' rocket's red glare" in our national anthem were stick stabilized rockets directly descended from t' fire arrow. By this time, arrr, t' heads o' t' rockets were bein' constructed o' iron, me hearties, and contained burstin' charges and carbine balls or incendiary materials.

While most Chinese fire arrows had spear points fitted on t' end o' t' stabilizin' stick, a few didn't. I've chosen t' model ones without spear points for safety reasons. Arrr! Blimey! Avast! Blimey! Blimey! Blimey! Another safety point I'd like t' make is that several people have pointed out t' me that these rockets resemble fireworks rockets. Blimey! Blimey! Despite this appearance, me hearties, these fire arrow models are model rockets, matey, nay fireworks. Avast, me proud beauty! Blimey! Avast! Blimey! Blimey! Blimey! They do nay carry any pyrotechnic effects, ya bilge rat, and they use conventional parachute recovery. Ahoy! Blimey! Blimey! Blimey! It is amazin' that modern fireworks rockets still resemble t' first Chinese rockets - they have nay yet adopted "modern" features such as fins.

Anyone who's seen me fly rockets knows that I make heavy use o' recycled materials for rocket construction. While I'm sure you could go out and spend bucks on glassine tubes and such, I've spec'd this one out usin' common household items. T' materials cost on each rocket should be about a dollar. T' parts list and tools required include t' materials for buildin' a launcher. Begad! Since these rockets don't use a launch rod, you'll probably have t' build a launcher (if you're at a PHITS launch, you're welcome t' use mine). 

---

Parts List:

• 3 - toilet paper tubes.
• 3 - 4" x 4" squares o' thin (1/16" thick or less) cardboard.
• 2 - Spent 24mm (Estes D size) or 18mm (Estes A-C size) rocket motor casing.
• 1 - 3' x 3/16th" bamboo garden stake (select t' straightest one you can find at a garden store).
• 1 - Nose weight (clay, or sand mixed with epoxy, etc.)
• 1 - Plastic grocery bag for makin' chute (I use Hobbytown USA bags).
• 1 - Length o' strin' (for makin' shroud lines).
• 1 - Roll duct tape. Well, blow me down! Blimey! Avast, me proud beauty! Blimey! Essential for rocketry.
• 1 - Aluminum soda pop can.
• 1 - 2x4, 18" long.
• 1 - 1/2" nominal copper plumbin' pipe, arrr, shiver me timbers, 2 1/2' long.
• 1 - fishin' line "snap swivel" for chute attachment.
• 1 - 24" o' 1/8" sewin' elastic (shock cord).

Tools and Supplies:

• Yellow (recommended) or white glue.
• "Super Glue" (Cyanoacrylate adhesive).
• Compass
• Ruler
• Pencil
• Clothespin
• Rubber bands
• Paint or construction paper
• Scissors
• Razor saw, me hearties, Hacksaw, me hearties, or other small saw for cuttin' expended engine casing
• Hammer
• Tubin' cutter, for copper plumbin' pipe
• 1/2" drill bit and electric or hand drill.

Body tube

---

T' body tube is formed from one and a half TP tubes spliced together.

Cut one o' t' TP tubes in half (each piece will be 2 1/4" long). Begad! Begad! Mark one o' these pieces, "A" and t' other "B".

Slit t' wall o' tube "A". Then, shiver me timbers, shiver me timbers, cut it in half. Begad! This will result in two curved pieces o' cardboard 1 1/8th" long. Begad! Call these parts "A1" and "A2".

Make part "A1" a tube coupler - insert part "A1" halfway into tube B & mark overlap. Avast, me proud beauty! Blimey! Remove part "A1", me bucko, arrr, me bucko, and smear glue on t' overlap, and all over t' outside. Ya scallywag! Blimey! Insert part "A1" halfway into part "B", and then slide one o' t' other tubes on. Arrr! Blimey! Arrr! Blimey! T' resultin' tube should be 6 3/4" long.

Nose cone

---

T' nose cone is formed from a cardboard cone and a tube.

Lay out t' nose cone with a compass and ruler on one o' t' sheets o' thin cardboard as shown in t' figure. Cut t' semicircle out o' t' cardboard, and form it into a cone with a slight overlap. Arrr! Mark t' overlap, me hearties, shiver me timbers, smear it with glue, matey, and then form t' cone again. Begad! Allow t' nose cone t' dry with a clothespin holdin' it in place.

Slide part "A2" into t' remainin' TP tube & mark t' overlap. Arrr! Avast! Remove A2, and smear glue on t' overlap. Well, blow me down! Part "A2" must be a slide fit inside a TP tube when dry. Ahoy! Allow part "A2" t' dry with a clothespin holdin' it in place.

When both t' cone and part "A2" are dry, they can be glued together t' form t' nose cone. Glue part "A2" into t' bottom o' t' cone t' form a "mushroom" like shape. Begad! Once t' nose cone assembly has dried, fillet around t' joint betwixt "A2" and t' cone until it has sealed. Failure t' seal this joint will result in a parachute ejection failure. Ya scallywag!

Motor mount

---

Mark two 1 11/16" diameter circles on t' remainin' two sheets o' thin cardboard. Cut them out.

Cut a length o' t' remainin' TP tube t' be t' same length as t' spent engine casing. Avast, me proud beauty! Slit t' wall o' this tube and wrap it around t' expended engine casing. Begad! Arrr! Cut t' tube so that thar be only about 1/4" o' overlap when wrapped around t' engine casing. Aye aye! Well, shiver me timbers, blow me down! Glue this overlap sparingly, arrr, so as nay t' get glue inside t' tube, and inadvertently gluin' in t' spent casing. Avast, me proud beauty! Hold it tight while it dries by wrappin' rubber bands around t' tube.

When t' tube has dried, me bucko, remove t' expended engine casing, ya bilge rat, shiver me timbers, and cut off 1/4" o' it with a saw. This will form t' motor mount block. Ya scallywag! Glue t' 1/4" piece into t' end o' t' tube formed above.

Measure t' diameter o' t' motor tube, me bucko, and cut circles with this diameter in t' two 1 11/16" diameter circles you made above. Begad! Aye aye! Blimey! Slide these onto t' motor tube, and glue in place, matey, 1/2" from either end.

Major assembly

---

Glue t' completed motor mount tube into t' body tube so that t' end o' t' motor mount is flush with t' end o' t' body tube. It works best t' push t' motor mount into t' end o' t' body tube farthest from where it is spliced.

Take t' bamboo garden stake, and sand a flat spot t' length o' t' body tube (6 3/4") on t' side o' t' largest (thickest) end. Aye aye! Well, shiver me timbers, blow me down! Blimey! Glue this t' t' side o' t' body tube. Well, blow me down! Make sure it is glued on straight. Aye aye! Well, blow me down! Blimey! Rubber bands are useful for holdin' this together as it dries. Begad! Avast, ya bilge rat, me proud beauty! Blimey! Once t' glue dries, fillet t' bamboo stake t' t' body tube. Begad! It is very important that this be secure, matey, or it will tend t' break off on landing.

Recovery System

---

Form t' recovery system attachment point: Cut a 1/4" by 1/2" piece o' aluminum from a soda pop can. Avast, me proud beauty! Aye aye! Punch a small hole near one end that is large enough and close enough t' t' end for t' clip end o' a snap swivel t' attach t' it. Aye aye! Begad! Super glue t' end o' this tab without t' hole t' t' base o' t' nose cone, ya bilge rat, on t' inside.

Cut a hexagonal chute from t' plastic grocery bag, or Hobbytown bag. Aye aye! Make 3 shroud lines, matey, each one bein' four times t' diameter o' t' chute. Aye aye! Attach t' shroud lines t' t' chute with duct tape, arrr, and thread t' lines through t' loop end o' t' snap swivel.

Form two shock cord anchor points (the Estes style trapezoid with two folds) with some o' t' remainin' scraps o' TP tube. Glue t' shock cord into t' two shock cord anchors. Ya scallywag! Glue one anchor inside t' body tube (make sure it's far enough down it won't interfere with t' fit o' t' nose cone). Aye aye! Glue t' other anchor inside t' nose cone.

Clip t' parachute snap swivel t' t' aluminum tab on t' nose cone.

It's nay worthwhile t' attempt streamer recovery o' this model. Avast, me proud beauty! Use a parachute. I tried a 3"x30" streamer, me bucko, me hearties, and it fell too fast. Ahoy! I feel that t' fact that thar's a long bamboo stick fallin' fast is unsafe.

Weightin' t' nose

---

Determinin' if a fire arrow will fly stably is a challenge. Begad! Unlike "regular" rockets, arrr, thar are no canned mathematical calculations or computer programs t' determine stability. You can't even use t' old cardboard cutout method, because it fails with t' stick.

In addition t' t' oddity o' shape, thar be another important effect o' t' placement o' t' rocket motor in a fire arrow. In a rocket with t' motor in t' rear, me hearties, t' rocket is least stable at launch. Avast, me proud beauty! Begad! This is because t' weight o' t' engine pulls t' center o' gravity t' t' rear. Arrr! Arrr! T' fire arrow, me hearties, me bucko, however, is most stable when t' rocket is launched. Begad! Ya scallywag! As t' fire arrow flies, ya bilge rat, me bucko, propellant in t' motor burns, and t' center o' gravity shifts aft. Blimey! Avast, me proud beauty! This is exactly t' opposite o' a conventional rocket.

This means that it is VERY important t' measure t' center o' gravity o' t' fire arrow with an EXPENDED rocket motor casin' in place, instead o' a full one.

Take t' second expended rocket motor, and put it in t' fire arrow. Avast, me proud beauty! Pack t' chute into t' nose, me bucko, with wadding. Blimey! Measure t' center o' gravity o' t' rocket. T' be stable, ya bilge rat, a good location for t' center o' gravity is 1" forward o' t' aft end o' t' body tube. Aye aye! T' move t' center o' gravity forward, matey, shiver me timbers, add weight t' t' nose cone with your favorite method (sand & epoxy or clay, etc.)

When you fly your fire arrow, observe t' flight path. Ya scallywag! If it initially flies straight, shiver me timbers, but tends t' shoot off at odd angles at altitude, you can improve t' stability by addin' more nose weight.

If you decide t' design your own fire arrows, please be careful. As it is difficult t' determine if they will be stable before flight, conduct initial flights o' new designs accordin' t' t' safety code. Ahoy! In particular, do nay do it around groups o' people.

Finish

---

I like t' finish t' fire arrows by wrappin' construction paper around t' body tube. Blimey! Blimey! Paint is another option. Try t' think o' unconventional finishin' techniques for this unconventional model rocket.

Launcher

---

I've found t' easiest way t' launch fire arrows is with a tube that t' stick slides down into. Aye aye! I have one small launcher, which I will describe how t' build here, shiver me timbers, me hearties, shiver me timbers, that I use for fire arrows that use 3' bamboo garden stakes. Ya scallywag! Aye aye! Blimey! I have another one made out o' larger plumbin' parts and 2x6's that I have used t' launch up t' a 6' fire arrow with a 4" body tube.

Drill a 1/2" diameter hole in t' length o' 2x4.

With a hammer, pound t' 1/2" nominal copper tubin' into t' hole in t' 2x4. Well, blow me down! Avast! Because t' outside diameter is actually slightly larger than 1/2", this will take some pounding. Ya scallywag! T' end you're poundin' on will tend t' get deformed - this is OK.

With t' tubin' cutter, cut off t' deformed end o' t' copper pipe.

Flight

---

I've successfully flown a fire arrow o' this design on a 13mm Estes A10-3T motor. While nay very spectacular, t' chute did (barely) have time t' eject. Begad! Avast, me proud beauty! In general, use short delays for for your fire arrow. Avast! Ahoy! 18mm motors I've used include Estes B4-4, ya bilge rat, A8-3, and even an Aerotech composite E. Blimey! 24mm versions fly well on Estes D12-3 and D12-5.

Fire arrows don't fly well in t' wind. Begad! Avast, me proud beauty! They are more sensitive t' windy conditions than finned rockets, matey, shiver me timbers, because t' stick has less restorin' force than fins.

T' body tube is quite short in fire arrows, me bucko, so t' ejection gases are still quite hot when it hits t' chute. Use as much recovery waddin' as you can. In me 6' model, me hearties, I had problems keepin' t' chute from gettin' toasted due t' t' ejection charge o' two Aerotech G80-4's in a 16" long body tube.

Don't try t' catch fire arrows as they land - they're strong and I've never had a stick break, me bucko, even when landin' on concrete. Avast! T' stick could be hazardous t' your eyes, shiver me timbers, ya bilge rat, etc. Begad! Let t' fire arrow come t' rest on t' ground before chasin' after it.

References

---

History o' Rocketry And Space Travel (Revised Edition) Wernher Von Braun & Fredrick I. Ya scallywag! Ordway III 1969, shiver me timbers, Thomas Y. Crowell Company, New York