Scratch Mercury Transport 29mm Original Design / Scratch Built

Scratch - Mercury Transport 29mm {Scratch}

Contributed by Nick Esselman

Manufacturer: Scratch

 

Rocket PicFeelin' a little bit like Rocky (you know, matey, "I did it Adrian, arrr, shiver me timbers, I did it!"), me hearties, I completed me 29mm Mercury Transport. Avast, me proud beauty! Blimey! Ya scallywag! Blimey! I originally planned on buildin' this rocket, arrr, me bucko, but built an 18mm version first just t' test out t' design. Avast, me proud beauty! It worked and so did this 29mm version.

I actually built this almost two years ago, matey, but thar hasn't been an appropriate Descon t' enter it into, arrr, so ta-da....

T' Mercury Transport's main purpose is t' transport 4 passengers t' 91.8 Million Kilometers t' t' planet Mercury for observation, study and experimentation in a high temperature, arrr, zero gravity, ya bilge rat, high sun-radiation environment. Avast! Aye aye! T' Mercury Transport has fins that are suspended over t' inner Fusion Proton Rod Reactor Core. Arrr! T' fins are in a test configuration for future interstellar travel and t' assist in coolin' t' core as t' ship passes close t' stars (such as our Sun). Begad! Well, blow me down! T' ship is primarily designed for long distance travel. Arrr! In fact, ya bilge rat, 95% o' t' entire ship is a reactor t' allow t' ship t' travel t' distance needed.

T' 29mm (should be 38mm) Mercury Transport is made from components o' t' Fat Cat Rockets' Centaurus rocket. Begad! I purchased t' followin' from Fat Cat Rockets (now OOP):

  • (2) Lower 4" Body Tubes (7.5" long)
  • (2) Balsa Transitions
  • (1) 2.6" Body Tube


Motor Mount

T' motor mount was a custom built with 4" centerin' rings for a central 29mm and (3) 24mm motors. T' 29mm motor tube be 12" long and extended into t' 2.6" tubin' and had a 2.6" centerin' ring. Begad! Ya scallywag! Blimey! This effectively focused t' 29mm ejection charge up t' 2.6" tubing. Avast! (picture is after last flight, even grass from t' landing)

T' recovery system consisted o' an eye-bolt on t' upper motor mount (2.6") centerin' ring. Tied t' that be 15 feet o' 1/2" Keelhaul®©™.

T' nose cone was one o' RGM's 4" Rounded Nose Cones.

I hand cut t' fins from 3/8" Plywood. Blimey! T' long strakes are Walmart Yard sticks with an angle cut from t' corner t' t' 3" mark on each side. Ahoy! Hey, these were a lot cheaper than buyin' wood and rippin' it.

For recovery, I used a 50" rip-stop nylon parachute.

CONSTRUCTION:

T' build on this rocket is fairly straight forward. T' transitions are glued onto t' 2.6" tubin' until t' tube is flush with t' large end. Arrr! Ya scallywag! I used TiteBond Original Wood Glue for this. Aye aye! I then used t' TiteBond glue and spread it all over t' outside o' t' balsa transitions t' seal and strengthen them.

I then glued t' two 4" tubes on each end usin' TiteBond. Avast, me proud beauty! T' shoulder on t' Fat Cat transitions is really short, but for both their Centaurus and me Mercury Transport it is strengthened with external structures. Avast, me proud beauty! In me case, shiver me timbers, arrr, t' 29mm motor tube extends into t' 2.6" tube from t' bottom and t' strakes attach t' t' outside o' both sections o' t' 4" tubing.

Next, shiver me timbers, I built t' motor mount and installed it usin' ProBond Polyurethane Glue. (additional comments about ProBond Polyurethane glue)

I marked t' body tube usin' an old BSD guide that came with me Thor, arrr, after extendin' t' lines t' convert from three fins t' six. Blimey! Blimey! I marked t' lines on both 4" tube sections usin' a door jam.

At this point, ya bilge rat, I covered t' 4" tubes and then used Plastic-Kote primer t' prepare t' inner tube (2.6") for finishing. Blimey! Avast! After t' transitions and inner tube were smooth, I painted them with Florescent Orange by Krylon. T' me disappointment, it did nay come out as "bright" as me 18mm version. Avast, me proud beauty! Avast! T' reason? I painted t' 18mm right over t' white body tube, whereas, me bucko, on this one it be over t' gray primer. Ahoy! Lesson learned.

After a couple days for thorough drying, shiver me timbers, arrr, I taped and covered t' inner tube with paper t' protect it.

Next was t' prepare t' strakes. After cuttin' t' Walmart yardsticks from t' corner t' t' 3" mark on each end, shiver me timbers, I attached them t' t' body tubes. Ya scallywag! I scuffed up t' tube and then used TiteBond for this attachment.

I cut me six fins with through-the-wall tabs. Ahoy! Three had t' be longer t' reach t' 29mm motor tube, shiver me timbers, arrr, while three where shorter t' attach t' t' 24mm tube. Avast! I also had t' ensure that t' upper root section was cut at an angle t' match up with t' yardsticks (strakes). Avast! After complete, arrr, I attached t' fins t' with TiteBond and used a clamp on t' fin t' yardstick interface t' keep them straight.

I next used Fix-It Epoxy Putty sold by Apogee Components for t' fin fillets. All I can say is Wow! I like it! This stuff be good t' work with. Aye aye! I used water t' dip me finger in for smoothin' out t' epoxy fillets. I didn't think this would bond terribly well t' t' body tube or wood as I didn't think it would penetrate, but after sufferin' flight damage on t' rocket, NONE o' t' breaks were on t' epoxy bonds. Begad! Begad! Nice stuff.

Unfinished

After everythin' was dry, I used Plasti-Kote primer and Dark Navy Blue by Krylon t' finish it.

Lastly, I checked t' center o' gravity in proportion t' me 18mm rocket and determined that I needs some nose weight. I added nose weight based on me RockSim file (which did nay calculate t' CP correctly as expected). Begad! Ya scallywag! I did this by drillin' two fill holes in t' shoulder base and put in BB's. Then I poured epoxy into t' holes, shook it, and poured more, me bucko, me hearties, until I couldn't hear any BB movement. I then capped it with another pourin' o' epoxy.

FLIGHT/RECOVERY:

At 2002 NYPowerT' final empty weight o' me Mercury Transport was 70 ounces (4 lbs, shiver me timbers, 6 ounces)

For t' first flight I decided t' use an H165 plus three (3) F24's. Begad! Ya scallywag! I set it up without any ejection charge in t' F24's and be ready t' go. Ahoy! Ahoy! A lot o' nice comments from others at t' 2002 NYPower (see t' picture someone took o' me?) so that was fun. Ahoy! I had trouble gettin' it onto t' rail as I be t' first one t' use this particular rail. Ya scallywag! I ran t' rocket up and down multiple times, which "cleaned" t' rail. Then, I waited for t' LCO t' count down. And waited, me bucko, and waited. Aye aye! Ahoy! Finally it came time and t' button was pushed and nothin' happened! I had t' recycle it. Ya scallywag! There goes 1 hour. Well, blow me down! Begad! T' next rocket on t' same pad (#30) failed t' ignite too and therefore that pad be taken out o' t' loop.

I went back t' next day and tried again. Ahoy! Blimey! Blimey! Blimey! This time somethin' happened at t' "launch" command. T' H165 lit and off she went. Aye aye! Blimey! Avast! Blimey! Ejection on t' "Short" delay was very early. T' nose cone went a flyin' one way while t' rocket under 'chute descended nicely. Aye aye! Blimey! T' nose cone landed within 50 feet o' t' pad with no damage. T' rocket landed a few hundred feet away with no damage.

That night I discovered that indeed (1) o' t' F24's lit too.

Lift-Off H238T' next day, me hearties, me bucko, I loaded it up with an H238 plus t' remainin' two (2) F24's and threw an E18 into t' empty slot. Ahoy! After another hour and a failed ignition. Ya scallywag! T' Head Range Officer recognized that I needed a booster-battery t' light this combination, shiver me timbers, he "guaranteed" me an ignition and we recycled.

On t' next cycle, I was loaded with a booster-battery and upon "launch" me "guarantee" was satisfied. Arrr! Aye aye! T' rocket leapt off t' pad under t' power o' t' H238 and at least one o' t' 24mm motors (as seen in t' picture) and at about 100 feet I heard/saw t' remainin' one or two 24mm motors ignite. Avast, me proud beauty! I used Quick Burst Ignitors. Avast, me proud beauty! Begad! I used a Fat Boy in t' H238 and Twiggys in t' 24mm motors. T' Twiggys had t' be built into t' motor as they did nay fit through t' F24 or E18 nozzles. Aye aye! So, me guess, me bucko, shiver me timbers, ya bilge rat, t' H238 and E18 lit, while t' two F24's delayed a bit. T' nice thin' is that those ignitors stayed in t' motors after t' H238 pushed t' rocket off!

Well, again t' ejection on t' "Short" delay be very early. Begad! This time t' nose cone seems t' explode. Ahoy! Several parts floated down. Begad! Ahoy! I never found t' nose weight. Avast! Avast! Don't really know what happen, but I have a guess. Avast, me proud beauty! My guess is that t' BB-epoxy nose weight fell upon ignition and then upon ejection, at t' limit o' t' shock cord (non-elastic), ya bilge rat, slammed into t' top t' nose cone and shattered it.


DamageT' rest o' t' rocket descended and hit hard, ya bilge rat, hard ground. Blimey! It broke one fin and strake off. Avast, me proud beauty! Ahoy! But notice that it did nay break t' epoxy, so again, I am very pleased with t' Fix-It Epoxy Putty. I have decided t' R.I.P. this rocket and move on t' me next project. Ya scallywag! This was fun!

SUMMARY:

In hindsight, I would recommend that this be built with a 38mm motor mount and forget about t' cluster. Ya scallywag! Begad! And that is it, really!

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