2.6" Optima Clone (bluetube 29mm, L1)

[dbmccann]

Well. knew I couldn't resist this one right?    July 2011.   
-------------

Probably going to be a slow build over the next month or so.  I've been thinking about this one for awhile.   First order of business is going to be making a final choice of fin material, and cutting the slots.  Right now thinking 3/16" plywood, and using a dremel to slot it.   

It begins...

Tonight I did some measurements.  The LOC nosecone is one inch longer than the Estes.  To compensate, I'm taking the radical step of.... making the body tube an inch shorter .
On the Shadow/Optima, the BT is 39 1/2".  I'll cut the blue tube to 38 1/2".  This will make both rockets 47 1/2" overall.  From the rear of the engine hook on the Optima, the motor mount/exhaust tube extends 31 1/2".   It doesn't appear  that will leave me enough room up front. The nose cone takes up more space, and I need to stuff in the nomex, 12 foot of tubular nylon, and a yet to be determined parachute (taking suggestions for an H128W flight, and park flying on F's).   I'm thinking something in the range of 15-20 inches for the motor mount will leave enough room. 



I also traced out the fins.  Once I sand the CR's and test fit the MMT, I'll get some measurements for the tab size. 


Tomorrow, sanding CR's to fit, fin slots, cutting to size, possibly sealing.

Tonight, we bust out the powertools.   I had no idea what would cut bluetube the best.  After my initial test cutting with a regular 40 tooth 10" blade, I wasn't happy.  The exterior of tube seemed to shatter, and splinter off.  It could have been that it wasn't a new blade.  However, I decided to go with an Irwin 180 tooth blade.  Cutting was done with a craftsman radial arm saw, spinning at 3500 RPM.   I also picked up a 10" masonry disc as a plan B.  I didn't need it, so not sure if it'd work better or worse.

First I roughed out the main fins and dorsal fins. I left the tabs on the mains wide open.  I plan to cut each by hand and sand to fit each slot.  I've never cut my own slots before, so I didn't aim for precise, exact anything on the cuts.  Files and sandpaper will do the final work for this one.   

Then on to the slots.  As I stood there looking at it all...I had -no idea- how I wanted to do it.    Tried easy first.  couldn't find my shadow or optima guides....so I went online, and printed off a new optima.  Yea, right.  too easy.  They don't match up. Expected that.  So I looked at things a bit....  made a new strip of paper,  wrapped it around the tube and marked it to line up.    Folded it in half and drew a line.   Measured the total length in mm.   Divided by 3.  Took that measurement, and drew lines on either side of my first line.   I don't know if I missed something...but it looks good to me.  I marked the tubes with a red sharpie (pencil doesnt show up at all on this bluetube).   

Next I took some 2 x 4 and drilled some guides onto the saw's table.   Raised the blade til it was just over the tube, and in a position to cut the slot within the size of the fins.  once I locked the arm into place, I turned on the blade, and very slowly started dropping it.  Each slot took 2 cuts to get the desired width.  They still need to be cleaned up...but that's for tomorrow.     Once I was happy with the slots,  I cut the tube to length (37.5") 

Things I would change next time (I hear someone laser cuts these? *facepalm*):
I'd turn the blade 90 degrees while making the slot cuts.  As I did it, if the bladelock failed, it could possibly bit on the tube, and not only ran up it, but gotten a bite out of my hand on it's trip.   Remote, but still possible.  On a less drastic side, it wouldn't be kicking dust in my face as I try to keep it all smooth and steady.     I'd also draw out the full shape of the desired cut.  I drew lines, and while I centered on them, having to make 2 slices at each it would have been easier with boxes.

slotting setup:


everything laid out back home.  Yea, I know.  Coors light.  It's hot as balls out.  No time to be drinking guinness.

I'm now starting the tedious task of fitting LOC rings to the bluetube motor mount.  I'm tempted to break out the dremel....but know I'll get better results by hand....and sweat.

[dbmccann]

Kit- nice tip on the saw.  I'm going to have to look into that.  Never expected to hear about something like that posting build photos, lol. 

Mmmm dual deploy  38mm.   Hadda be a fun project.   Would love to see that fired off.

Kurt- why is everyone NOW telling me I could order all these parts laser cut!!!    I love the Optima/ Shadow...but the estes kit is a bit fragile at times.

 Not much tonight,  it's too freaking hot to sand any more.   I cut the MMT down to 15 inches by hand.   Sanded the rest of the CR's onto it, and sanded the end down for the aeropack.   I cleaned up the slots a bit with an x-acto.  The inside of the tube needed to be sanded up some to clear the slots, and figured it'll help the epoxy bond.   So, I took some sandpaper, and duct taped it to the closest thing to me.  A vacuum wand.


I'm also getting to the point I'm eyeing up my excess materials.  I've got a good bit of 29mm tube left that may wind up a min dia., and a short fat piece of 2.56 that may get mated to the 5 inch bit of 29mm I just lopped off the end of the mmt..... just need some nosecones and a couple CR's.... rest is all laying around here...

Finished up sanding the outside of the CR's this afternoon.  Roughed up the MMT exterior while I was at it.   The mid ring is set at 4" from the rear.  Next up I'm going to measure and number each slot for fin tabs.  Each slot came out just slightly different, so I'm going to number and match the fins.   Thinking 30 min epoxy for the motor mount, and internal fillets, then JB weld for the retainer and rear ring.   Working on an airframe without a coupler, I'm still trying to think of good ways to get enough epoxy on that upper  CR.  Doing it without getting it on the attached nylon shock cord will be interesting.


Cut and fit the main fin tabs tonight.  They stick out a bit still, lots of sanding ahead.  Everything dry fit together pretty well.  I just need to finish mounting the bolt for the recovery harness,  sand a few bits and pieces, and then epoxy it all up.   After doing a short search here on rail button placement, I've decided to just close my eyes and randomly place them

Looks like a rocket:

[dbmccann]

I got my little package in.    Work progresses. Finally putting epoxy on.





Almost forgot tonight's photos.  
Tacked the fins on with loctite 5 min epoxy. Then I dropped some permatex 30 min into each chamber and left the rocket standing vertical while it setup. I had slight leaks out a couple slots, but it wiped up neatly.  I went with 30 minute to get a good soak into things.


Ugly photo of internal fillets. Doesn't look nice, but it's solid. Again with the 30 minute epoxy.


I ordered rail buttons from Apogee.  I found a spot where the weld nuts would be above the lower CR and marked it.  I used a 3/16 bit to drill the hole with an 18v drill. Used some Permatex 4 minute metal epoxy on this.  The stuff is thick and sets nice and hard. Also good to 300 degrees.



The rear CR was a pain.  Could have been the heat getting to me.  I had sanded and fit it all dry.  Of course, the inner main tube, and exterior MMT were now coated in a thin layer of epoxy despite my best efforts to keep them dry.  There would be no way to fit the CR, then remove it and add epoxy, so I had one shot at it. I mixed up some more 30 minute, and spread it around the tube, and on the internal fin edges.  I pressed the CR in,  and it got just onto the MMT and stopped dead.  Getting my fingers in to press down in the tight space wasn't working.   So, I ran out the the garage...grabbed the biggest flathead screwdriver we have, and a hammer.   Blue Tube is stout.  A few good wacks and the CR was seated.   I mixed up a bunch of JB weld next for the Aeropack.  I lined the inside ridged edge with JB, and tried to screw it onto the MMT.  Being that it's set into the bodytube to be flush,  I had issues with this.  After several cross-threaded, sweat pouring into my eyes, failed attempts at this, I laid it over the back of the MMT, and hit it with the hammer. Perfect fit!  I then used the rest of the JB weld on the rear CR.  This CR is NEVER coming out.


The front Rail button hole is drilled, I just need to play with a stick and get the nut installed.  The front dorsal fins need to be sanded and placed.   Once that's done, I'll pull the Kevlar through the U bolt ( currently have paracord looped there) and install the chute and nosecone.  Thinking of cutting open the NC and drilling out for an eye bolt. It'll help move the CG up a bit, and be solid. 

Then it's just prime, paint, and decals.


edit:  forgot to mention, after all the fuss about getting epoxy on the forward CR, I found a simple solution.  After epoxying the front and mid CR's to the MMT, (aft removed at this time) and covering up the Ubolt nuts, I tied a 5 foot loop of paracord to the U bolt.  I fed the cord through the main BT.  Then i stood the MMT assembly on my desk, laying the main BT close by.   I mixed up some 5 minute epoxy, and laid a generous amount on top of the front CR, up against the motor tube.  I quickly grabbed the main BT, pulled the cord tight, lined it up over the front CR, and pushed it down.  I had marked in my fin slots where I wanted the mid CR, and the epoxy was still pliable enough to push the MMT around until it lined up.  I then turned the body vertical, and rolled it around until the epoxy spread evenly around.   It sounds like a lot, but from putting epoxy down, to finish, it all probably took less than 20 seconds.

I wasn't gonna work on it tonight, but I got bored   First up the dorsal fins.

Then onto the front rail button.  This should have been simple....but I didn't look at placement when I installed the mmt.  So, the U bolt is sorta in the way.  Took a couple different ideas and tries.  First I tried a long thick coat hanger with some playdoh on the end.  This would have worked,  but was too thick to get past the U bolt.

Then I used a 1/4" rod, and taped an alligator to it.  This got it close enough that I could drop the bolt in and catch the nut and pull it up.  Before this I put a small bit of JB weld on the nut.


This shows the position of the U bolt, and I smeared some JB weld over the back of the nut.


A couple of the rocket together.   Just a few finishing details here and there, installation of the recovery system, small external fillets on the fins, and then fill/prime/paint/fly.



Here's next week's project:

   [edit 2015,  this wound up in the 2.6" DS]

Structurally speaking.... she's finished.   Just did the fillets tonight.  everything else is just finishing and making it pretty.

[dbmccann]

Wow,  today was like Christmas.  Mailman left me 3 awesome packages.

3 foot chute from rocketman
2X of F20-4W,  F42-4T, and G78-7G  (need to order some redlines)
two sets of Optima Decals from StickerShock.   

I STILL havent decided on a paint scheme yet.  I thought I had something in mind...but this big old Orange chute makes me think the stock colors might be good.  I've got metal flake vinyl for Green, Blue, and Orange.

I'm starting to get slightly antsy to Launch this puppy.    Really wanna light off those g78's.


Annnnnd we're priming.




I hate sanding.   That is all. 

I figure at least 2-3 more cycles of this.



Well, the idea was to fill in the spirals entirely with Rustoleum   primer/filler.   The above photo was after 3 coats/sandings.  Then I laid on a thick coat of primer/filler. let that dry.  Laid on an entire can of black primer.  let that dry.   Laid on an entire can of white primer.  let that dry.   Then I laid on another can of gray primer filler.  Just to be sure.  (I was getting sick of those spirals.)

Let it all dry up for a few days. I used 100, 150 and 220 grit sandpaper on the upper tube.   Then I busted out the 3m sponges for between the fins.  The red ones are the best for this type of work,  80 grit.  I used one large one, and 2 small ones.  Would have liked a few more of them really.  the small 180 grit tan ones I used for the finsihing work.   I know I used way too much primer in the end.   However, there are still traces of the white layer in the spirals.  The other layer of gray was entirely removed.  I took most of the body down to just above the tube.   

Using several different colors really helped to pick out the high spots, show coverage of new layers,  and when I was bad,  where to sand down the runs.   After sanding, it also left some unique patterns.   I think on my next rocket I'm going to experiment with this for a finishing pattern.   

Right after this, I got excited and tried to lay on the first coat of my final colors.   After using so much thick primer,  the testors lacquer laughed at my desire to lay it on thick, and ran like a track star.   lesson learned.  gonna sand it all off, lay a thin coat of white primer, sand it smooth,  then coat this beast up.   Adds about another week of painting...but it'll look nicer.




I was going to wait until I was totally finished to post anymore photos.  Too impatient to wait til then.

This isn't a flawless paintjob, but it's the best I've ever done. There's a jump or two from masking the dorsal fins, and some uneven spots here and there.    When the blue was wet, a family of gnats flew into the side of it.  ><  Overall though, I'm happy with it, and it absolutely should look good from 15 feet. 

I still have the vinyl rings to place around the blue/white transition, and on the fins.
I've also got a big ole Optima logo from stickershock to slap on the side  

This is Testor's One Coat Lacquer.  White Lightning and Star Spangled Blue.
Light sanding with a 320 sponge, and 2 quick coats of Blue and it had a nice candy-coated shine.   The white is a little more picky.  You really need a good even basecoat sanded very very smooth, and multiple coatings to get a good shine on it.





Laid the bigass Stickershock Optima on tonight.   I had planned to use metal flake Blue vinyl for the rings and fins.   Now I'm not so sure.   The blue doesn't stand out,  and I don't want to add any other colors.  Considering leaving it as is,  or using a plain white stripe for the upper ring between the chrome 2.   Think I'm going to sit on the idea for a week or so.



Finally got to get out and fly.  First Flight was on an F50T-4. unfortunately My Altimeter Two reported the previous flight's info on that. Strange but worked fine the rest of the day.   Second Flight was on a G78G-7.  The first one I tried failed on 2 ignitors.  I set it aside and the second one worked fine.  About 690 feet at 136 MPH.   Last Flight was on a G38FJ-4.  only 431 feet and 88 MPH,  but a fun flight.   Took a little damage on the front of the BT on the landing.  I took an insane amount of photos, and caught some really cool ejection sequences of all the laundry popping out.  Just going to share of the best here,  then tomorrow post a link to the finished gallery with all the ejections and such.   

Thanks for everyone's comments and ideas during this thread.  It helped a lot.


 Now, on with the photos:
F50T:




G78G:



G38FJ:

[dbmccann]

[dbmccann]

Spoiler Alert!!!    I built a 38mm version



needs paint....thinking stock...

[dbmccann]

Man. so many Optimas......   too many you say?

[dbmccann]

Considering a 54mm mount 2.6" body rocket.   Might be an optima,   Might be a 2.6" Madcow pike.    both would have their issues....but be fun on J175W's and K250's

The fins on the optima are the troubling bit.   Going to have to be stiff to get past mach.   thinking 3/16 CF maybe.   (I hate t2t)


I don't think they actually make a 2.6" Pike, but shouldn't be too hard to ask.   I'm thinking 1/8" fins and a 54 mount for that.

[RKeller]

I plugged the basic fin dimensions into Aero Fin Sim and you would be good with 3/16" G10 or 1/8" carbon fiber.
This is with 3/16" G10

[dbmccann]

Wow.  That'll be much easier.  Thanks

[dbmccann]

I forgot about this thread.... Some updates.... Optima 2929 is ready to fly,  Working on painting the pair. 



Filling the spirals on the 38 did NOT go as planned.... the lower half I finally got the hang of it.




Planning on doing the 38 Stock,  the 2929 will likely be a Shadow or Dark Optima scheme.