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mccordmw

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My fiance has been watching me work on my L1/L2 Binder Design Excel Plus 54 for some time with growing interest. We've built little Estes rockets for our kids to paint and fly at a nearby field. Now she want to try her hand at a large L0 rocket that is built to fly on L1 as well. I've got a ton of 2' long 3" diameter heavy wall mailing tubes that have been crying for attention. This is the perfect opportunity to build something with her that can fly on G to I motors that can also fall in the class 0 category so we can launch at the nearby field our club uses.

I want to fabricate as much as possible by myself to help hone my building skills.

Nosecone will be a PNC-3.00 for thick-walled tubes
Airframe: 3" x 2' heavy walled paper mailing tubes
Coupler: cut down mailer tube
Fins: 3-ply 1/4" plywood cut to shape
Centering rings: same 3-ply plywood cut with a flywheel cutter
Motor: 1-4 grain 38mm CTI

Here is the initial design.

Mailer Rocket.jpg

Sims to 1000' on a G and almost 3000' on an H.

View attachment Lara.ork
 
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mccordmw

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On G motors and lower H's, it flies low enough that we'll stick with single deploy. I have a 2' nylon chute to spare which is perfect. I'm going to build an electronics bay for dual deploy at higher altitudes.
 

mccordmw

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I got a lot done last night. I want to have this ready with my fiance for the Sept. 17th launch at Walnut Grove. I'll go for L1 cert at that time with mine.

Grooves were filled with CWF. I use a putty knife to scrape them smooth before sanding down smooth with 220 grit sandpaper. After sanding, a paper wrap was used to measure and mark off the points for the three fins and rail guides. Straight lines were drawn with angle iron. Here, you can see the paper template and the filled, marked lower airframe.

20160821_140002.jpg

The fins were drawn up using OpenRocket and printed out using their tool. The printout was taped to foam board and cut out as a template. This was traced on to some 1/4" 3-ply plywood; orienting the grain along the length of the fin. Cuts were made with my sliding miter chop saw and were really close to the line. Hardly any shaping was needed before they were ready for bevels.

*In my earlier post, I thought I have 7-ply. Nope! It's 3-ply. Should be durable enough for G-I motors.

The foam template:

20160821_140026.jpg

The fins were beveled at about 22 degrees until reaching almost the middle of the plywood thickness. The second bevel at 45 degrees finished the job. Fin tabs and root attachment points weren't beveled.

20160821_153242.jpg

A side-by-side comparison shows that beveling was really close to identical on all the fins. If I can just mount them straight, it should fly really well. :p

20160821_153326.jpg

Digital calipers measured the thickness of each fin at 5.95mm. So much for being a full 1/4". Glad I measured. Fin cutting lines were drawn using the angle iron at 3mm offset from the center line of each previously drawn line. The bottom of the fin slot was cut to just above two centering rings of depth. Here you can see a dry fit test of the first fin in the slot with the 38mm motor mount and two centering rings to test fit. Fit like a glove.

20160821_193408.jpg

Repeated two more times and checked. All lined up well.

The motor mount tube was pulled out and two aft centering rings were epoxied together to the bottom of the motor mount using JB Weld. Once it's done curing, pics of progress to come tonight.

Last bit was to print out a fin alignment jig. I went to http://www.payloadbay.com/page-Tools.html , put in my specs and printed out the alignment jig. That was taped to some foam board and cut out with my hobby knife. Tonight, I'll help tack on the fins.

I rather liked the method used on my Binder Design rocket, so I plan to also cut out the tabs on the lower airframe and remove the fin can once it's epoxied on. That way, I can put in nice fillets before re-inserting.

So tonight, it will be:
- nosecone sanding
- coupler cut and epoxied
- cut motor mount to the proper length
- fins epoxied in
- cut out fin can
- epoxy on top centering ring

Probably no time to filet the fin roots tonight. Coming together fast, though.

Note: I'm doing all the blueprinting and cutting. She's doing the epoxy work since she wanted to co-build her rocket, and she's not comfortable doing the cutting and sanding stuff yet. But hey, shared hobbies are great. Now I gotta help my 13yo build his MPR kit for the launch. Busy!
 
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mccordmw

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More progress!

To join the 2 x 24" airframe tubes, I needed a coupler. Luckily, I have another 20 (!) of the same tubes sitting around, so I can butcher one to make a couples. I cut 6 inches, made a lengthwise cut and marked off how much to remove to fit a coupler. The way I make them is to use scotch tape on the outside just to hold the coupler shape and keep excess epoxy from oozing out. On the inside, I smear a one inch wide line of epoxy across the cut. That gets covered with heavy duty Gorilla tape. Makes for a super stable epoxy join.

Not to self: next time, don't use a tube that already had the grooves filled. :p

I leave the scotch tape on the outside. No need to remove it.

20160822_164648.jpg

Inside with the Gorilla tape. It's really sturdy.

20160822_164702.jpg

On to the centering rings. I used my flywheel cutter on the plywood a few times to get some rings. The results were....lacking. I couldn't get a clean edge that I was comfortable enough with to use that could take the force of a motor thrust. Backup plan. I used some spare Apogee 38mm to 3" centering rings. Luckily, they fit perfectly.

Using more JB Weld, the two centering rings were epoxied together and then epoxied to the end of the motor mount to form the aft end. The motor mount tube was cut to appropriate length to support a 2 grain to 4 grain motor case without having too much under/overhang. Once the fins are on, I'll go back with more epoxy to form a generous filet in front of the rings for strength. Here's the result with the case and motors I'll use:

20160822_164827.jpg

The 2 grain case has a spacer already inserted inside it, so those motors will fit. I have a spacer plus a 2 and 4 grain case (not pictured), so I can launch a huge variety of motors. I got the 4 grain case for free as part of Apogee's CTI certification special.

Now on to mounting the fins. First up is to make a fin jig. I printed out a template from www.payloadbay.com/page-Tools.html , taped it to foam board, and cut it out with a hobby knife. The template and my cut fin slots aligned perfectly.

20160822_164917.jpg

More JB Weld was prepped and the airframe/jig was set up for epoxying.

20160822_221051.jpg

Generous amounts of JB Weld were buttered on to the root edge of each fin which was slid into place before pullilng the jig down tight.

20160822_221701.jpg

The whole thing was then taped down to make sure it didn't move while curing overnight. Alignment looked great and the leading/trailing edges were nice and parallel to the airframe.

20160822_222007.jpg

This morning, I cut out the tabs in the lower airframe and pulled out the fin can. They had good attachment to the motor mount with tiny, 2mm filets set up. Up for tonight is:

- epoxy on top centering ring
- add Rocketpoxy filets to the fin can

I should have this thing ready to prime and paint by the weeked. Unfortunately, we have 6 days of rain in the forecast now.
:mad:

All the weights and measures say this will fly just fine on the G motors I have, but I'm still worried. Thrust to weight is fine, though... Still seems big for a G motor rocket. The H will be its sweet spot.
 

Nick@JET

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Nice work! I have several mailing tubes waiting in the wings.
 

Cabernut

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Cool. I may have to try the fin can this way on my next 3" mailer rocket. I found some that are only 5.7g per inch and I'm already planning my next one.
 

mccordmw

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These tubes are 165g for 24 inches. They're really sturdy. Just as tough as any LOC tube I've seen. Dimensions are:

3.05" OD
2.94" ID
24" L

I still have a "few" left. (15 more).
 

mccordmw

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Progress update!

After an overnight cure, we cut the numbered tabs from the tube and set them aside for later re-gluing to fill the gaps. The fin can then easily slid out. The top centering ring was not first epoxied to the motor tube. That was taped into place to simply make sure the tube was nice and centered during fin attachment.

20160823_181514.jpg

Now that the fin can is out, I removed the tape on the top ring and epoxied it to the top of the fins with JB Weld. Contact with the fins was good all around, indicating I have the fins at the same height and size for each. This is one of my best alignments to date.

The attachment of the root to the motor tube looked excellent with full contact, no gaps, and a tiny filet set up. This is one reason I love pulling out the fin can like this. It lets me visually check the attachment and then make corrections if there is a gap. Here, you can see the complete contact and the now epoxied top centering ring.

20160823_181943.jpg

I let the top ring cure for a couple hours to make sure it didn't move. Then it was on to adding filets to the fin roots and rings for the real strength. Here's my filet rig. I shove a broom stick through the tube to let it sit in my rocket cradle and rotate easily. I'll be using Rocket Poxy for the internal and external filets since it flows really well and settles into nice filets.

20160823_201840.jpg

The Rocket Poxy is mixed 1:1 in plastic cups and applied using craft sticks.

My Rocket Poxy is getting old, and the epoxy is getting really thick. You can microwave the epoxy bottle in 10 second increments to melt the crystallized epoxy. I didn't nuke it quite long enough, so it didn't flow like honey. That gave me a bit rough and uneven internal filets. Didn't concern me since they won't be seen. I'll make sure to have nice and flowing epoxy for the external filets.

Internal filets done.

20160823_222013.jpg

After the internal fin filets were done, a filet was added to the top of the centering ring.

20160823_222709.jpg

This is curing overnight. Tonight, on the agenda is:

- add eyebolt and shock cord to the top centering ring
- epoxy in the fin can to the airframe
- glue in the previously cut tabs
- attach parachute to nose cone

Final construction step on Thursday night is to add the external filets. After that, all I need are shear pins to the nose cone, brass pins to the couple to prevent airframe separation, and then I can prime/sand/paint/launch!
 

mccordmw

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Another update.

Last night, I put in the eyebolt and shock cord to the top centering ring. The nuts holding the eyebolt were epoxied into place using Rocket Poxy. I have a 3-loop 9/16" nylon harness from http://onebadhawk.com/ attached using a screw lock carabiner. The harness is pulled backward out the motor mount to keep it out of the way and clean.

Then, it's on to re-inserting the fin can. It's hard to tell in this pic, but a generous ring of JB Weld is slathered inside around the front of the fin slots for the front centering ring to set in and push up a filet. After inserting the fin can about 4 inches, I had enough clearance to put more JB Weld now at the end of the tube for the aft centering rings and thrust plate.

20160824_224548.jpg

After the fin can is fully inserted, the end is tightened down using zip ties. Then, it's left to cure overnight.

20160824_224952.jpg

This morning, I slip off the zip tie and checked everything. It's all solidly epoxied in. Here you can see a shot down in the tube checking the top filet. It's not the best. I didn't have enough JB Weld pushed up for a solid filet. I'd say it's still way more than enough to take a G to I motor, as intended. You can also see the bolts down there in the centering ring. If I get paranoid, I'll put some additional Rocket Poxy down there with a long dowel. Not sure it's needed.

20160824_225357.jpg

Last step this morning was to glue the tabs back in. They aren't really structural, so I just used some carpenter's wood glue. Remember, number the tabs and slots, and fins so you can re-insert the fin can properly and glue back the tabs in their right spots. It's those little things that always got me when I first started building.

20160825_071331.jpg

Last thing I did this morning was to mark the spot where I'll drill into the aft centering ring for the rear rail guide. Also, I marked off the spot for the top rail guide. Tonight, it's time to tape off the fins and work on the external filets. I'll need to re-nuke my old Rocket Poxy to get it flowing like honey.

Progress is looking good for prime+paint this weekend if it doesn't storm. My fiance went with an anodized candy red color. I was tempted to get that Alsa spray paint. It's gorgeous. But in the end, I went with Dupli-color.

I'll primer a couple layers with Dupli-Color FP102 Red Oxide General Purpose Sandable Scratch Filler and Primer.
The ground coat will be a couple coats of Dupli-Color MC100 Ground Coat Metal Cast Anodized Color.
Finally, it'll get the red. Dupli-Color MC200 Red Metal Cast Anodized Color.

Videos of the effect make it look really nice.

I think I'll go with Alsa when I'm building an L3 fiberglass rocket.
 

mccordmw

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Filets are all done. They came out perfect. I can't feel any edge where the tube and fins transition into the filets. I follow the same method now that most others do, and it works beautifully.

1. take an ~2" long piece of 3/4" PVC pipe.
2. using a black sharpie, color in about half of the radius of the tube black.
3. lay the tube into the corner of the airframe and fin and drag it back and forth to mark each with a faint black line.
4. that's the boundary you need to tape off for your filet.

Here's the progress mid-taping off.

20160825_200448.jpg

Epoxy time. I used my old Rocket Poxy. Since it was old, I had to nuke the epoxy jar about 10 seconds to get it flowing again before mixing. I used a total of 24 g epoxy + 24 g hardener. It was mixed and let to sit about 15' to thicken up just a little to prevent too much filet sagging.

Epoxy was applied with craft sticks and smoothed by dragging that same 2" piece of PVC down the filets. I dragged about 4 times for each filet to make sure they were smooth. I found that dragging very slowly while holding the PVC at about a 22 degree angle gave me smoother results and avoided creating voids or bubbles. I let this cure for about 30' until it was like putty on the rocket. The tape was removed, and I rounded off the front/back of each filet using an isopropanol-wetted gloved finger. Doing that let me mold a nice, smooth curve around the front and back of each fin.

After working each fin, the PVC tube was scraped of excess epoxy and cleaned with isopropanol and a shop rag.

The end results came out great. Smooth, glassy filets where I can feel no edges between the airframe to the filet to the fin. Shouldn't need hardly any sanding here. One downside to the cheap mailing tube. When I pulled off the blue tape, a little paper came with it and left me with fuzzies. I should have used my less tacky green tape. Oh well.

Different angles of the results show below. Also shows the fuzzy bits created. :facepalm:

20160825_211818.jpg

20160825_211806.jpg

20160825_210805.jpg

20160825_210748.jpg

I'm ready to prime and paint. After that, shear pins and rail guides, and camera shroud then it's go time.
 
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mccordmw

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Flights planned for this rocket are set and simmed.

Shakedown flight:
Motor: CTI 38mm 1-grain G46 Classic
Stability calibers: 1.98
Initial thrust-to-weight: 8:1
Velocity off rail: 19 m/s
Max acceleration: 75 m/s
Max velocity: 90 m/s (mach 0.26)
Apogee: 395 m (1,295 ft)

Shakedown flight #2 (because I have a spare white on hand and I like the whoosh :D):
Motor: CTI 38mm 1-grain G58 White
Stability calibers: 1.89
Initial thrust-to-weight: 9:1
Velocity off rail: 19 m/s
Max acceleration: 73 m/s
Max velocity: 103 m/s (mach 0.30)
Apogee: 442 m (1,450 ft)

HPR flight:
Motor: CTI 38mm 2-grain H100 Imax
Stability calibers: 1.42
Initial thrust-to-weight: 10:1
Velocity off rail: 19 m/s
Max acceleration: 96 m/s
Max velocity: 185 m/s (mach 0.54)
Apogee: 885 m (2,900 ft)

All are single-deploy from motor eject coming down on a 30" ripstop nylon chute.
 

Cabernut

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Looks great so far. What are you using for motor retention?
 

mccordmw

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First two layers of gray primer are on. Going to sand tonight then put on the red high build primer tomorrow. I understimated how much the bare cardboard would soak up primer. I estimated a total weight of about 1013g without the motor. After two layers of primer, I weighed the whole thing without a motor. I'm at 1050g. Now that the paint absorption is done, I'm estimating another 150g total weight for the paint. That means I need to recalculate my thrust-to-weight and velocity off an 8' rail.

I'm now at an 8:1 thrust-to-weight ratio with an estimated velocity off an 8' rod at 13 m/s. The ratio seems ok, but I'm worried about the speed. I know the minimum acceptable ratio is 3:1 with preferred ratios of generally 6:1. However, I've read several times that a minimum speed off the rail is 15 m/s. I should be ok, right? Thoughts?
 

mccordmw

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All done. This weekend was paint time. I wanted to paint this rocket with a chrome effect with layers of metallic fine, so I did things differently. My process for this rocket was:

1. One coat of Rustoleum filler primer.
2. Sand 90% of the primer off using 600 grit until all is uniform and smooth.
3. Once coat of Duplicolor hi-build sandable primer (used red for this one since I want a rich red top coat).
4. Wet sand with 1000 grit sandpaper.
5. Repeat the hi-build primer and wet sanding.
6. Spray with Duplicolor metallic ground coat. This left the whole thing shiny and sparkly. You can zoom in to see the fine.

20160827_152730.jpg

7. The first ground coat was grainy feeling, so I wet sanded it with 1000 grit sandpaper.
8. Second ground coat went on much more smoothly, so this was polished with a 2000 grit sandpaper wet sanding.

Ground coat done and ready for color.

20160826_213723.jpg

9. One coat of Duplicolor red chrome.
10. This was really smooth, so no sanding.
11. Second coat of red chrome.
12. Polish this with a light, wet sanding with 2000 grit sandpaper.
13. Spray with Duplicolor color effex color shifting clear coat for a prismatic effect.
14. Polish with my hand buffer and Meguiar's Compound.
15. Prep for waxing with my hand buffer and Meguiar's Polish.
16. Wax with Meguiar's Ultimate Liquid Wax.
17. Buff out with a sheepskin bonnet.

Final result is a chrome red rocket that shift to a black color as you get more off angle when viewing. You can see here the top looks black. If you look straight on, it's candy apple red.

20160828_182715.jpg

Close up shows the metal fine detail. Plus, the filets came out great. You can't see any transition as they melt from the fin to the airframe. I wish I could say that wa skill, but I got lucky that the tape was dead on where the epoxy ended, so I didn't have to sand it at all. Plus, the high build primer really blends in the curves.

20160828_182756.jpg

I'm getting better at painting, but there's still some orange peel. I'm mainly too impatient to sand enough to minimize that, and my technique isn't good enough to prevent it. Also, in MO, the heat and humidity resulted in some blushing of the paint. Luckily, that went away completely as it cured overnight in the house.
 

mccordmw

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I found my new favorite buffing machine. This is light enough to easily hold in one hand. It's small enough to get into the corners around the fins. Also, it's really quiet. I spread out on a dropcloth in the family room and could polish there while the family watched TV. I'd rather build with them around.

Carrand 94000AS AutoSpa 6" Orbital Professional 120 Volt Automotive Polisher
$25 at Walmart
 

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