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

Mystery Rocket

Why t' "Mystery Rocket"? Well, ya bilge rat, because I built it in secret from me wife. Avast, me proud beauty! I wouldn't let her see it at any stage o' t' construction. Ahoy! 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. Aye aye! What can I say, t' name just stuck. Avast, me proud beauty! In fact, t' first time she saw it was when I "unveiled" it at t' launchin' field for it's first launch. Aye aye! As predicted, shiver me timbers, her first comment was "Is that even goin' t' work?" I get that a lot.

T' photo above be taken that first day. Begad! Avast! 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, ya bilge rat, though. Ya scallywag! You'll notice that all t' edges are rounded, and, ya bilge rat, though you can't tell from t' photo, me hearties, t' fins are sanded t' an airfoil shape. Avast, me proud beauty! Ahoy! It's built with care, me bucko, shiver me timbers, me bucko, it's just nay painted.

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

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

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

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

Well, me hearties, me hearties, thar should have been a fourth question, but I was so convinced that it wouldn't be a problem, that I really didn't give it much attention... Would t' motor exhaust burn t' lower structure?

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

Update 1997 Nov 15

Before t' second launch, I painted it. Aye aye! Ahoy! I wanted t' lower structure t' have some resistance to scorching, so I used some flat black exhaust system spray paint (good t' 1500 F) for t' body tubes. Begad! Ya scallywag! I then painted t' vertical struts day-glow orange (aka International Orange) for contrast. Arrr! I didn't use any maskin' tape... 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. Avast, me proud beauty! Here are photos from t' second launch day: launch photo #1, ya bilge rat, launch photo #2, me bucko, recovery photo, arrr, and a close-up o' it in flight. Begad! Avast! Blimey! T' close-up photo shows why thar's some scorchin' o' t' lower structure, arrr, 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. Arrr! I only ask that if you do somethin' cool or practical, arrr, shiver me timbers, please write t' meand tell me about it! Note that at t' bottom, I have a list o' alternatives t' t' construction I've detailed here. Begad! O' course, shiver me timbers, 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, 36" long for t' vertical rods
• 1/2" wide balsa strip, arrr, 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, shiver me timbers, me bucko, 18-24" long (I used 1/16" round elastic cord, 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, 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, ruler, me hearties, table, matey, me hearties, brain, eye-hand coordination, arrr, etc)
• Aliphatic resin glue (aka Yellow glue, aka Carpenter's Wood Glue)
• 3/8" wooden dowel, shiver me timbers, at least 24" long, me hearties, 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. T' 2" piece be t' lower body tube, arrr, t' 7" piece be t' upper body tube.
2. Cut out t' three 2"x3" fins. Aye aye! Begad! Sand them t' an airfoil shape, ya bilge rat, me hearties, apply sandin' sealer, and sand them smooth.
3. Cut t' three struts from t' 10" balsa strip. Ahoy! T' make sure that they extend exactly t' same distance (3") as t' fins, arrr, me bucko, 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. Arrr! Aye aye! 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. Aye aye! Sand t' ends t' a pleasin' rounded shape.
5. Glue in t' engine block.
6. Mark t' upper body tube 65mm from t' bottom, and cut a 3mm wide slit in t' tube thar for t' engine hook. 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. Well, blow me down! 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. I put t' bottom edge o' t' struts about 3" from t' back end o' t' body tube.
10. Ok, here's t' tricky part. Aye aye! Blimey! Slide t' two expended 18mm engine casings (with t' clay nozzles knocked out) onto t' 3/8" wooden dowel. Ahoy! Blimey! Now take t' upper structure and slip it over one o' these engine cases on t' dowel. Avast, me proud beauty! Blimey! Put it in just like a normal engine. Begad! Blimey! 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. Aye aye! Blimey! Aye aye! Blimey! I just used me eyeball for this alignment, ya bilge rat, 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). Begad! Rotate t' dowel so that one fin/strut pair is pointin' straight up. Ahoy! Begad! Again, me bucko, I used me eyeball, me hearties, but if you have a level, me bucko, go nuts with it. Ahoy! Glue one o' t' vertical rods t' this fin/strut pairin' so that it extends about 2" below t' fin. Blimey! Let it dry completely. Arrr! Repeat for t' other two rods.
12. Now glue on t' two launch lugs, me bucko, puttin' t' lower one in t' fin/body tube joint, and t' upper one in t' correspondin' strut/body tube joint. Avast! Blimey! 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. 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, and tie it t' t' snap swivel.
15. Tie t' small split rin' t' t' elastic shock cord, ya bilge rat, 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, me hearties, shiver me timbers, elastic shock cord, me bucko, and as much o' t' thin 100lbs test line as possible in t' top o' t' top body tube. T' nose cone may be a moderately tight fit since t' thin line is in t' way, but it wasn't too tight for me (the ejection charge still blows it off easily). Ya scallywag! If it's really tight, 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, more or less, me hearties, shiver me timbers, me hearties, 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), ya bilge rat, just substitute BT-50 tubin' for t' BT-20 tubing, and a PNC-50 nose cone for t' PNC-20 nose cone. Ahoy! I'll probably try this soon, just t' see if it holds together. 

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

On t' other hand, arrr, if you want t' build a scaled down version t' use 13mm mini engines (or 10.5mm micro engines), matey, you'll probably have t' find somethin' much lighter than t' 3/16" dowel used for t' vertical rods, me hearties, in addition t' usin' small body tubes and smaller nose cone. 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. Blimey! T' first is t' put more distance betwixt t' engine and t' lower structure. Begad! You could easily put 2 more inches betwixt them just by attachin' t' fins and struts farther apart on t' vertical rods. Or you could go with longer vertical rods. But be careful about addin' too much weight this way (hardwood dowels aren't light). Avast! Or you could t' struts at more o' an angle or mount them lower on t' upper body tube. 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... Aye aye! 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. Ahoy! That way, me bucko, me hearties, t' hot engine exhaust should mostly just blow through t' tube, rather than onto it. Ahoy! Begad! Be forewarned, matey, however, that this will result in significantly less fin area, so it might become unstable by makin' this modification. If you're afraid o' that, just make that piece o' body tube and t' fins taller t' increase their total area. Ya scallywag! Blimey! I'm pretty convinced that this thin' is very over stable as it is now, ya bilge rat, though, so I wouldn't worry about it too much.

If you're just worried about meltin' or burnin' t' lower launch lug, me bucko, matey, try epoxyin' a couple o' small metal split rings t' t' fin/body tube joint t' form t' launch rod guide, shiver me timbers, instead o' usin' a traditional launch lug. Begad! Don't stress too much about it, though, because I continue t' launch t' original, me bucko, me hearties, 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. It wasn't t' wind's fault, though; I should have used somethin' bigger than an A8-3 engine. Begad! T' rocket got turned over before ejection, shiver me timbers, and fell into t' chute, tanglin' t' chute, me hearties, and causin' t' crash.

Update 1997 Dec 12

I glued it all back together, and reinforced t' new joints with strips o' silk span. Avast, me proud beauty! 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.