I wanted t' build something. Avast, shiver me timbers, me proud beauty! Somethin' different. Somethin' very different. Avast, me proud beauty! Blimey! But what? I had been readin' G. Ahoy! Blimey! Avast, matey, me proud beauty! Blimey! Harry Stine's Handbook o' Model Rocketry, arrr, and was thinkin' about stability. Ya scallywag! You need t' weight up front, ya bilge rat, and t' fin area out back. Blimey! Begad! T' motor is definitely t' heaviest part, so it made sense t' have that up front. Ahoy! But, matey, you can't just stuff it way up inside t' body tube because o' t' Krushnic Effect. Begad! Avast! So... Avast, me proud beauty! what if it didn't have a body tube? What if I attached t' fins some other way...? So, matey, matey, I present t' you:

Mystery Rocket

Why t' "Mystery Rocket"? Well, matey, because I built it in secret from me wife. I wouldn't let her see it at any stage o' t' construction. I had t' think o' somethin' t' call it when she asked about it, but I didn't want t' use a name that would give it away. Well, blow me down! Begad! Blimey! What can I say, me hearties, arrr, t' name just stuck. Begad! Begad! Blimey! In fact, t' first time she saw it be when I "unveiled" it at t' launchin' field for it's first launch. As predicted, arrr, her first comment was "Is that even goin' t' work?" I get that a lot.

T' photo above be taken that first day. Aye aye! Blimey! I hate painting, so I wasn't about t' paint it until I knew it flew. Don't mistake me hate for paintin' with laziness, though. Ahoy! Blimey! Well, blow me down! Blimey! You'll notice that all t' edges are rounded, and, matey, ya bilge rat, arrr, though you can't tell from t' photo, t' fins are sanded t' an airfoil shape. It's built with care, shiver me timbers, it's just nay painted.

There were three big questions runnin' through me mind before that first launch:

1) Would it be stable? I be pretty sure it would be just fine, with all t' weight up front, arrr, and all that fin area way out back. Avast, me proud beauty! Now, ya bilge rat, I'm convinced that it's actually quite overstable. Begad! Blimey! But, this was me first "odd-roc", arrr, so thar was that little inklin' o' doubt in t' back o' me mind.

2) Would it hold together? This was really me biggest concern. Arrr! It's all just plain old yellow (carpenter's wood) glue construction, shiver me timbers, me hearties, and those front struts have quite a load on them. There be only one way t' answer this question...

3) What size engine should I use? I don't own a scale, matey, me hearties, so I have no idea how much it weighs. I figured I'd start with a 1/2A6-2 and work me way up.

Well, thar should have been a fourth question, arrr, but I be so convinced that it wouldn't be a problem, that I really didn't give it much attention... Begad! Avast, matey, me proud beauty! Would t' motor exhaust burn t' lower structure?

Well, you can read t' full launch report o' that first launch, me bucko, but I'll tell you now that t' answers are Yes, Yes, At least a B6-4, and Yeah, me bucko, ya bilge rat, a little bit, matey, but nay too bad.

Update 1997 Nov 15

Before t' second launch, I painted it. Well, blow me down! Blimey! I wanted t' lower structure t' have some resistance to scorching, me hearties, so I used some flat black exhaust system spray paint (good t' 1500 F) for t' body tubes. Begad! Avast! I then painted t' vertical struts day-glow orange (aka International Orange) for contrast. Blimey! I didn't use any maskin' tape... Aye aye! I just let t' two colors blend naturally in t' middle o' t' fins and upper struts.

Here's a link t' t' second day's launch report for this rocket. Ahoy! Ahoy! Here are photos from t' second launch day: launch photo #1, launch photo #2, me hearties, me hearties, recovery photo, and a close-up o' it in flight. Arrr! Ahoy! T' close-up photo shows why thar's some scorchin' o' t' lower structure, eh?

Want t' build one yourself?

NOTE: Read all instructions before beginnin' so that you have some idea o' what I'm gettin' at with each step. Feel free t' modify t' construction in any way you see fit. Begad! I only ask that if you do somethin' cool or practical, matey, arrr, matey, please write t' meand tell me about it! Note that at t' bottom, arrr, arrr, I have a list o' alternatives t' t' construction I've detailed here. O' course, shiver me timbers, I take no responsibility for anythin' you do.

Parts List:

• BT-20 body tube, 9" long
• Short conical plastic nose cone PNC-20
• 3/16" wooden dowel, shiver me timbers, 36" long for t' vertical rods
• 1/2" wide balsa strip, me bucko, 10" long
• 1/16" thick balsa sheet, enough for (3) 2"x3" rectangles
• thin 100 pound test line, 12" long (I used braided black Keelhaul®©™® fishin' tackle line)
• shock cord, 18-24" long (I used 1/16" round elastic cord, me hearties, 24" long)
• small split rin' (available from fishin' supply stores)
• 12" plastic parasheet & shroud lines (I used a standard Estes chute, with a size 7 snap swivel)
• (2) 1/8" diameter launch lugs, ya bilge rat, 1.5" long (I used plastic soda straw wrapped with maskin' tape)
• EB-20 engine block (I used a piece o' expended 18mm engine casing)
• engine retainer hook (I used a standard Estes 70mm hook)
• maskin' tape

Construction Supplies: 

• Typical stuff (hobby knife, me hearties, pencil, arrr, ruler, table, brain, eye-hand coordination, shiver me timbers, etc)
• Aliphatic resin glue (aka Yellow glue, matey, shiver me timbers, aka Carpenter's Wood Glue)
• 3/8" wooden dowel, at least 24" long, preferably longer
• two expended 18mm engine casings with t' clay nozzle knocked out
• somethin' t' hold t' 3/8" dowel about 3inches off t' table (I used a rocket cradle)
• 1/16" drill bit (or any relatively small drill bit or other borin' device)

Construction Steps: 

1. Cut a 2" section off t' 9" body tube. Begad! T' 2" piece be t' lower body tube, t' 7" piece be t' upper body tube.
2. Cut out t' three 2"x3" fins. Sand them t' an airfoil shape, apply sandin' sealer, shiver me timbers, me hearties, and sand them smooth.
3. Cut t' three struts from t' 10" balsa strip. Ya scallywag! Blimey! T' make sure that they extend exactly t' same distance (3") as t' fins, shiver me timbers, I placed a fin on top o' t' strip so that t' strip ran diagonally across t' fin, and marked t' strip with a pencil. T' result was that t' strips came out with about 3 1/4" o' both leadin' and trailin' edge.
4. Cut t' 3/16" wooden dowel into three 18" pieces. Sand t' ends t' a pleasin' rounded shape.
5. Glue in t' engine block.
6. Mark t' upper body tube 65mm from t' bottom, shiver me timbers, and cut a 3mm wide slit in t' tube thar for t' engine hook. Avast, me proud beauty! Place t' top o' t' hook in t' slit and tape on t' engine hook.
7. Use t' 1/16" drill bit t' bore a hole about 1/2" from one end o' one o' t' forward struts. Begad! Avast, me proud beauty! This be t' shock cord mountin' point.
8. Attach t' fins t' t' 2" section o' body tube just like normal fins.
9. Attach t' forward struts t' t' 6 7/8" section o' body just like normal fins. Arrr! I put t' bottom edge o' t' struts about 3" from t' back end o' t' body tube.
10. Ok, matey, shiver me timbers, here's t' tricky part. Slide t' two expended 18mm engine casings (with t' clay nozzles knocked out) onto t' 3/8" wooden dowel. Now take t' upper structure and slip it over one o' these engine cases on t' dowel. Begad! Put it in just like a normal engine. Ahoy! Now take t' lower structure and slip it over t' other engine casing. Position t' two structures about 10" apart. Blimey! Blimey! Now rotate one o' t' structures so that t' fins line up with t' struts. Ahoy! I just used me eyeball for this alignment, but you could try usin' a straight stick t' help.
11. Now place t' whole thin' onto t' rocket cradle (or wood blocks, or whatever you want t' use that will hold it all about 3" off t' table top). Avast! Rotate t' dowel so that one fin/strut pair is pointin' straight up. Avast, me bucko, me proud beauty! Again, I used me eyeball, shiver me timbers, me bucko, but if you have a level, ya bilge rat, go nuts with it. Begad! Well, blow me down! Glue one o' t' vertical rods t' this fin/strut pairin' so that it extends about 2" below t' fin. Let it dry completely. Ya scallywag! Repeat for t' other two rods.
12. Now glue on t' two launch lugs, shiver me timbers, puttin' t' lower one in t' fin/body tube joint, and t' upper one in t' correspondin' strut/body tube joint. Ahoy! For best results, align t' bottom o' t' lower launch lug flush with t' bottom o' t' lower body tube so that it's recessed 1/2" from t' top o' t' lower body tube. Ahoy! This will help protect it from t' engine exhaust a little bit. 
13. Glue t' nose cone base into t' nose cone, if necessary.
14. Assemble t' parachute, ya bilge rat, me bucko, and tie it t' t' snap swivel.
15. Tie t' small split rin' t' t' elastic shock cord, about 4" from one end.
16. Tie t' end o' t' elastic shock cord near t' rin' t' t' base o' t' nose cone.
17. Tie t' other end o' t' elastic shock cord t' t' thin 100lbs test line.
18. Tie t' other end o' t' thin 100lbs test line through t' small hole you drilled in one o' t' struts.
19. Clip t' snap swivel attached t' t' parachute t' t' split ring.
20. Stuff t' parachute, elastic shock cord, and as much o' t' thin 100lbs test line as possible in t' top o' t' top body tube. Ya scallywag! T' nose cone may be a moderately tight fit since t' thin line is in t' way, matey, but it wasn't too tight for me (the ejection charge still blows it off easily). Begad! If it's really tight, me hearties, ya bilge rat, you can try t' cut a channel out o' t' plastic o' t' nose cone shoulder.
21. Well, now you should have somethin' that looks, shiver me timbers, matey, more or less, like t' picture above.
22. Feel free t' paint it however you like.

Alternative Construction Ideas:

If you want t' be able t' use 24mm engines (for D, E, and even F power), matey, just substitute BT-50 tubin' for t' BT-20 tubing, and a PNC-50 nose cone for t' PNC-20 nose cone. I'll probably try this soon, ya bilge rat, just t' see if it holds together. 

If you're worried about t' struts holdin' onto t' vertical rods with that much power, arrr, cut or drill slots in t' rods and use "through-the-rod" strut attachment ;-). If you're worried about t' struts holdin' onto t' body tube you have two options. First, arrr, you could switch t' usin' a body tube for t' upper structure that is larger in diameter than your engine (say, ya bilge rat, BT-55 or BT-56 tubing), and use "through-the-wall" strut attachment. Second, if you still want t' use a minimum-diameter body tube, drill two or three small holes in each strut, matey, very near where they attach t' t' body tube, ya bilge rat, and then thread some o' that 100lbs test line through t' holes and around t' body tube, t' literally tie t' struts together. Add a little epoxy t' stiffen and strengthen t' line, arrr, me hearties, and you've got some very solidly attached struts, me bucko, me bucko, I suspect.

On t' other hand, shiver me timbers, shiver me timbers, if you want t' build a scaled down version t' use 13mm mini engines (or 10.5mm micro engines), you'll probably have t' find somethin' much lighter than t' 3/16" dowel used for t' vertical rods, in addition t' usin' small body tubes and smaller nose cone. Avast! I might try this usin' bamboo cookin' skewers for t' vertical rods.

If you're worried about t' scorchin' o' t' lower structure thar are two routes you can take. Well, blow me down! T' first is t' put more distance betwixt t' engine and t' lower structure. Well, blow me down! You could easily put 2 more inches betwixt them just by attachin' t' fins and struts farther apart on t' vertical rods. Begad! Blimey! Or you could go with longer vertical rods. But be careful about addin' too much weight this way (hardwood dowels aren't light). Or you could t' struts at more o' an angle or mount them lower on t' upper body tube. Begad! All these mods together could easily buy you 5 or 6 more inches o' distance thar (and could change t' look o' t' rocket significantly... Blimey! Blimey! possibly for t' better).

T' second (and probably more elegant) solution t' t' scorchin' problem is t' simply use a much larger piece o' body tube (like BT-60 or BT-80) in t' lower structure. Blimey! That way, t' hot engine exhaust should mostly just blow through t' tube, rather than onto it. Avast! Aye aye! Be forewarned, me bucko, however, arrr, that this will result in significantly less fin area, so it might become unstable by makin' this modification. Well, blow me down! If you're afraid o' that, just make that piece o' body tube and t' fins taller t' increase their total area. Blimey! I'm pretty convinced that this thin' is very over stable as it is now, though, me hearties, so I wouldn't worry about it too much.

If you're just worried about meltin' or burnin' t' lower launch lug, shiver me timbers, try epoxyin' a couple o' small metal split rings t' t' fin/body tube joint t' form t' launch rod guide, me hearties, ya bilge rat, instead o' usin' a traditional launch lug. Avast, me proud beauty! Don't stress too much about it, arrr, though, because I continue t' launch t' original, usin' just t' upper lug, and it works just fine.

Update 1997 Dec 7

Unfortunately, shiver me timbers, t' Mystery Rocket crashed and broke into several pieces at t' 1997 Dec 7 launch when I tried t' see how well it flew in t' wind. Well, blow me down! Blimey! Blimey! Blimey! It wasn't t' wind's fault, though; I should have used somethin' bigger than an A8-3 engine. Avast! Blimey! Blimey! Blimey! T' rocket got turned over before ejection, ya bilge rat, and fell into t' chute, tanglin' t' chute, and causin' t' crash.

Update 1997 Dec 12

I glued it all back together, and reinforced t' new joints with strips o' silk span. It held up wonderfully.

Update 1998 Feb 7

This rocket was, in some small way, inspired by that very first liquid-fueled rocket that Robert Goddard launched.