Brief:
T' Intersteller Cruise Liner consists o' three segments. At t' top, matey, furthest away from t' engines, be t' cabin for t' passengers with a set o' canard fins. Aye aye! Next be t' cargo section and finally t' hyper-atomic engines. Ahoy! Avast! T' liner has t' ability t' land on a planets surface with it telescopin' legs (similar t' those golden years o' rockets from the 1950's).

T' rocket is over 4' tall and flies on 24mm motors. It uses a combination o' tube fin, ya bilge rat, rin' fin, me hearties, and standard balsa fins.

Construction:
This design and build is for t' 2008 EMRR Challenge #6 t' use a software program t' design a rocket and then build and fly t' design. Blimey! Well, blow me down! This is me first real attempt t' design a rocket usin' RockSim. Some issues I ran into may be more my lack o' experience than a shortcomin' in t' RockSim program.

I did nay want t' do a simple 3FNC design, ya bilge rat, although for a first attempt at RockSim that may have been a better choice. Begad! Blimey! I wanted somethin' more with t' '50s style o' sci-fi rockets. While I don't think t' rocket came out quite retro style, it is not a 3FNC.

One goal I had be I wanted a combination o' fins. Begad! I had some 2.84" body tube left over from another project that I wanted t' use as a rin' fin, matey, me hearties, but I did nay want t' use balsa pods t' support this ring--I wanted t' use tube fins as t' rin' fin support. Ya scallywag! I started lookin' at different size tubes t' select a body tube with tube fins that would match t' inside diameter o' t' rin' fin. I finally decided on t' Semroc LT-115 size with BT-30 tube fins. Ya scallywag! I was also goin' t' have conventional fins that would intersect with t' rin' fin that would also end up bein' t' support for the landin' legs. Aye aye! A final touch were t' radiator fins on t' engine compartment t' help remove heat and protect t' cargo section.

T' cargo compartment I made larger in diameter than t' engine tube and t' passenger section reduced down again.

My RockSim adventure, and all RockSim designs, ya bilge rat, start at t' nose cone. Avast! I added t' passenger tube, me hearties, shiver me timbers, the transition, me bucko, t' cargo tube, t' next transition, matey, and finally t' engine tube. Avast, me hearties, me proud beauty! When selectin' t' transition parts, matey, it always assumes t' small end is t' t' front and t' larger size is t' t' rear. Avast! Avast! You can easily change t' properties to reverse t' transition, matey, shiver me timbers, but make sure you remember or write down all t' parameters.

Addin' t' tube fins be easy, but I wanted t' tubes beveled. Arrr! I could nay find a way t' perform this, matey, so I used the average length for t' simulation.

I then added t' rin' fin. Ahoy! RockSim requires pods t' support t' rin' fin, matey, but I was usin' t' tube fins. Avast! Blimey! I set the pod data t' only one cardboard 0.0001" thick pod so it would nay affect t' design.

T' next step was t' add t' main fins. Well, blow me down! I used t' free form plan points t' develop t' fins. I initially had some problems with this and had t' retry a couple o' times, matey, but I finally got it. Begad! Now, arrr, shiver me timbers, one advantage and disadvantage o' RockSim is it is nay a true, matey, 3D modeling tool so it will nay flag any issues with parts interferin' with each other. Arrr! For me it was an advantage as I wanted the main fin t' intersect with t' rin' fin and I did nay have t' worry about about tryin' t' include t' slot in me fin plan. On t' other hand, matey, if you have a design problem where two items interfere that you did nay plan, ya bilge rat, RockSim will not warn you.

I included a second set o' fins with t' plan for a dowel betwixt t' fins. Aye aye! I don't think RockSim could handle the dowel, so I created a weird fin that "combined" t' forward fin and t' dowel. Aye aye! I specified this fin t' be made from fir with a rounded cross section.

I added t' motor mount, me bucko, centerin' ring, shiver me timbers, engine hook and block, launch lug, screw eye, me bucko, and parachutes (as I planned t' use an 18" for t' engine compartment and a 12" for t' cargo/passenger sections).

I initially was goin' t' use small tubes for t' radiator section, me bucko, me hearties, but RockSim indicated it would be unstable. Actually, at this point RockSim did somethin' strange. I would "fly" it one time and it would be stable and another time it would be unstable. Arrr! Well, blow me down! Part o' this I discovered was due t' t' simulation mode--basically, arrr, how much wind and how variable t' wind would be. Avast, me proud beauty! Arrr! You also can set t' launch rod length. Blimey! RockSim indicated I needed almost 4' of launch rod. Avast, me proud beauty! Blimey! T' default appears t' be 3'. Begad! I decided durin' t' build t' change t' 1/4" lug since I have a 6' rod that size. Blimey! Avast! All o' me 1/8" and 3/16" rods are only 3' long. A few other things I learned about RockSim is you can specify usin' either t' Barrowman, RockSim, or cardboard cutout t' determine stability. Avast, me proud beauty! You can also use either the nose cone diameter or t' maximum frontal diameter for t' static margin. Ahoy! I think betwixt t' stability calculation method, t' static margin basis, me bucko, and t' weather/launch rod is what caused t' stable/unstable results.

I did extend t' passenger tube some. Arrr! I finally decided t' change from t' tube radiators t' a balsa fin. Avast, me proud beauty! RockSim only allows a maximum o' 8 fins (I wanted 12), shiver me timbers, me hearties, so I set up 3 sets o' 4 fins and used t' Radial Position t' offset them. Ahoy! T' straight balsa radiators also helped with t' stability issues I had.

Finally, I added t' canards because now RockSim indicated t' design was overstable.

So now it is time t' build--or at least order all t' parts.

T' final part list consisted o' t' following:

• BC-944 nose cone
• BR-11518 transition
• BR-918 transition
• BT-30B body tube (for t' tube fins)
• LT-115220 body tube (for t' engine section)
• LT-27580 body tube (rin' fin)
• ST-1890 body tube (for t' cargo compartment)
• ST-9180 body tube (for t' passenger section and t' 24mm engine)
• CR-9115 #9 t' #115 centerin' ring
• EH-38 long engine hook
• 1/4" dowels (the landin' legs)
• 3/16" balsa - fins
• 3/32" balsa - canards
• 3/32" X 1/4" balsa - radiators
• 18" parachute
• 12" parachute
• 1/4" elastic cord
• 1/8" elastic cord

I ordered all t' parts except t' dowels, fin stock, matey, parachutes, me hearties, and elastic cord from Semroc. Avast, me bucko, me proud beauty! I placed t' order on Saturday and t' box be on me doorstep on Wednesday. T' parachutes I had on hand and t' elastic cord came from my stock from Wal-Mart.

T' very first thin' I did, me bucko, was t' check that me concept for t' tube fins t' be t' support pods for t' ring fin would work. Avast! I dry fit them together and it all slid together nicely.

I cut me tubes t' length and filled t' small spirals (I probably could have skipped this step as t' spirals were small). Aye aye! As with a typical rocket, I built t' motor mount first. Avast, me proud beauty! I made a slot in the tube, put t' hook in, me bucko, glued t' coupler over t' top, and t' engine block into t' tube.

I transfered me fin designs t' card stock and cut them from t' balsa. I joined t' dowel and balsa fins together usin' a straight edge. Begad! Well, blow me down! Since t' dowel was 1/4" and t' balsa be only 3/16", shiver me timbers, I made some shims from scrap card stock and placed it under t' fin material. Arrr! Begad! This allowed t' dowel t' be centered on t' fin.

I needed t' mark t' tubes--I had 12 radiators, 3 tube fins, and 3 dowel/fin units. Begad! Knowin' t' diameter o' the tubes, arrr, I used a drawin' program t' lay out a markin' guide. Ya scallywag! Let's see, t' circumference o' a circle is 2 * pi * r. Avast! T' diameter o' t' tube is 1.22" so 1.22 * 2 * pi = t' wrong answer. Ahoy! Ahoy! My first layouts looked huge! What did I do wrong? Wait...hey, thar be a difference betwixt radius and diameter. Aye aye! (Duh...rocket scientist at work?) Well, shiver me timbers, at least that was a simple one t' fix.

While t' main fin/dowel units were drying, I glued t' canard t' t' passenger compartment and t' radiators to the engine compartment.

I cut t' tube fins t' size and beveled them. T' bevel used t' same pointy approach used by t' Pemperton Kraken. Avast! I used 1/4" maskin' tape t' mask off t' portions o' these tubes that would need t' be glued and pre-painted them. Aye aye! I knew they would be a pain t' paint once assembled.

When t' dowel/fin units were dry, me bucko, I figured out where I needed t' slot t' fins for t' rin' tube and used an X-Acto t' cut t' slots. Avast, me proud beauty! Then I dry fit everythin' together again (with t' help from maskin' tape). While it was together, I marked on t' rin' tube where it would need t' be glued. Blimey! Well, blow me down! Again, matey, I masked t' glue area and pre-painted. Well, blow me down!

I glued and filleted t' fins onto t' engine tube. Arrr! Avast, matey, me proud beauty! I masked t' glue areas on t' tube for the tube fins and on t' balsa fins for t' rin' fin, me hearties, and painted t' engine compartment. Begad! Once dry, I removed all the maskin' and finally glued on t' tube fins, matey, rin' fin, and launch lug. Avast, me proud beauty! Then I finally glued t' motor mount in, lining the hook up with t' launch lug.

I also painted t' cargo and passenger compartments.

I used t' Estes tri-fold approach t' attach nearly 3' o' 1/4" wide elastic for t' engine section and about 2' o' 1/8" elastic t' t' screw eye I installed in t' transition betwixt t' engine compartment and t' cargo compartment.

Finishing:
After t' rocket was built, arrr, I checked out t' real rocket against t' RockSim specs. Arrr! Begad! My real rocket be heavier by about 0.7 ounces. Ahoy! Ya scallywag! My first thought was this was due t' t' glue, ya bilge rat, paint, ya bilge rat, and possibly items (like t' elastic cord) that I had missed in t' design. Then I checked t' center o' gravity. Avast! It be much higher in t' real rocket than what RockSim predicted. Arrr! I went back t' t' computer and created a mass object equivalent t' t' 0.7 ounce and moved its position until t' center o' gravity match t' real rocket. Ya scallywag! I simulated a flight, but since t' rocket be already stable, movin' t' cg forward only made it better (possibly overstable).

One concern I did have was whether t' dowels would survive hittin' t' ground. Aye aye! Aye aye! I thought o' reinforcin' them, but I was concerned about how heavy t' rocket was getting. Also, I was runnin' out o' time! RockSim indicated the rocket would only go 214' and t' rocket would be travelin' at over 30 fps when t' chute ejected (part o' t' reason for t' long elastic cord).

Flight:
Well, shiver me timbers, time was runnin' out t' try t' fly this beast. Avast! I loaded up t' car and went t' t' school yard. Well, matey, blow me down! Weather was poor with on and off rain and drizzle. Begad! I get there, ya bilge rat, and t' field is in use. I went back later. Begad! Begad! T' weather was still poor, arrr, ya bilge rat, but I only had 2 days left t' meet t' challenge deadline. I set up t' pad with t' 6' long 1/4" rod and loaded a D12-3 engine. Ya scallywag! A few photos and 3-2-1 launch. Ahoy! Well, me hearties, blow me down! Well, me bucko, t' rocket went "straight" up, but an interesting thin' happened. Ya scallywag! Blimey! It did nay weathercock, arrr, shiver me timbers, shiver me timbers, however, I did see it drift sideways due t' t' wind. Aye aye!

Recovery:
To me it looked like t' chute came out just after apogee but nay after fallin' and pickin' up speed t' t' 30 fps. In fact, initially t' cargo/passenger section was floatin' down sideways since t' 12" chute did nay want t' pop open. Begad! T' rocket drifted a bit, and then landed. Ahoy! It stuck t' landing, sort of. Avast! T' one dowel was stuck in t' ground with t' rocket layin' on its side next t' it. Ya scallywag! Aye aye! I knew I should have reinforced that joint! Otherwise, ya bilge rat, arrr, t' rocket did fine. Ahoy! I think I would change t' 18" parachute for a 24" t' slow t' landing.

Summary:
Well, it was an interestin' exercise really usin' RockSim for t' first time. Blimey! T' me it looks like for a standard 3FNC rocket it is easy t' use. If you want t' make exotic or fantasy type rockets, ya bilge rat, you will need t' play many games and may even need t' question t' results. I'm nay even sure it could handle some o' t' Shrox rockets, t' Fliskits ACME Spitfire, me hearties, t' Odyssey, or others o' that type. Ya scallywag! T' Apogee website does have many tips in t' "e-zine" section though. Ahoy! Some o' t' tips will allow RockSim t' properly simulate t' rocket, but it then can't properly display what the rocket looks like. Begad! There are also tips that can be found in some o' t' various forum sites.

In t' long run, me hearties, I am nay happy with t' paint job. It looks too much like I just joined 2 different rockets. Aye aye! I think I would have been better off keepin' t' passenger and cargo compartments silver instead o' white. But I was happy with t' tube fin/rin' fin/balsa fin combination.