"Millennium Falcon" - AlnessW’s RW Mongoose 75 Build Thread

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AlnessW

AlnessW

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Build page now available at: https://wilsonalness.com/rocketry/projects/MillenniumFalcon.html
(Website back online after a massive crash...)

Background
I don't do many kits these days, but when I was glancing through Rocketry Warehouse's Black Friday sale this past year, I couldn’t resist their $139 sale price on a fiberglass Mongoose 75 kit. Ordered November 28, 2015, delivered to my doorstep February 1, 2016. If you really want specifics, see my posts to RW's Black Friday thread in the vendor forum. While my order took about 2 months to get here, rest assured it was well worth the wait.

Name & Design
With the new Star Wars franchise (great movie by the way), it seemed only fitting to include a reference to the famous starship here. Of course, this kit will be heavily modified to better suit my needs (as to be expected) and will be much more of a "kit bash" than anything else. More on this below.

The stock kit includes:

  • 3" x 48" booster section
  • 3" x 24" upper section
  • 3" 5:1 Von Karman Nosecone with coupler/bulkhead
  • 10" av-bay with 1" switch band, and CNC-stepped bulkheads
  • 3 x 3/16" G10 fins (beveled)
  • 2 x fin alignment guides (1/16" fiberglass)
  • Decal
  • Several other parts of which I can’t place where they would go - some short lengths of coupler and an extra 1/8" bulkhead.
IMG_4315.jpg

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Here she is!

IMG_4324.jpg
I couldn't help but do a little dry-fit...

Obviously, the normal layout here would be to build it standard dual deploy with the upper airframe/av-bay/nosecone. However, this project will be more geared towards altitude and hence will not be using that design. Instead, I’ll leave out the 24" upper section entirely, just fly the booster section, and do dual deploy using the nosecone coupler as an av-bay.

I fly my own motors, so this will be flown exclusively on EX loads. Partially with this project in mind, I ordered a new 75/7600 complete hardware set from Mike Fisher. (My old 7600 case is a little shorter now after its previous misfortune.) It is 41" long – a 41" case in a 48" booster section, now there's a good motor to airframe ratio.

The 7" of remaining space or so should be just enough to fit some harness into, and then the main chute will be housed inside the nosecone.

Construction
I've decided to go with no layups on this rocket. With big fillets and careful attention to epoxy use, she'll absolutely hold. Still debating epoxies, but Loctite E-120HP for attachments and Loctite 9462 for fillets seems more than likely.

Avionics:

  • Featherweight Raven3
  • MissileWorks RRC2+
  • 70cm 100mW Beeline GPS
  • 900 MHz Beeline GPS
Recovery
Drogueless with (depending on final weights) a Rocketman 4' main.


Will probably start construction this weekend or so. Follow along if you wish!
 
AlnessW said:
  • Several other parts of which I can’t place where they would go - some short lengths of coupler and an extra 1/8" bulkhead.
Click to expand...
Internal motor retention. Sandwich the bulkhead between the couplers and add a 3/8" nut to the center of the bulkhead. Most commercial motors use 3/8" threads in the forward closure. Since we already know you are flying EX, it's a moot point. I'm sure you have another method for motor retention. Any left over parts I'd be glad to take off your hands....
Subscribed. Love this rocket, my full up ( with payload) Mongoose flew to 28,905 ft. on an M840.
 
Have you considered reducing the size of the fins? It appears the goal of this project is to maximize altitude and that would be one very important step to get as much as you can out of this rocket.

Additionally, you're doubling up on your GPS electronics. Any reason to not trust the 100mW BRB? Have you considered swapping over to a Telemetrum or an AIM Xtra 2.0 for maximum functionality and reduced weight/internal volume requirements?
 
patelldp said:
Have you considered reducing the size of the fins? It appears the goal of this project is to maximize altitude and that would be one very important step to get as much as you can out of this rocket.

Additionally, you're doubling up on your GPS electronics. Any reason to not trust the 100mW BRB? Have you considered swapping over to a Telemetrum or an AIM Xtra 2.0 for maximum functionality and reduced weight/internal volume requirements?
Click to expand...

That was my question...why two GPS units?
 
Since I had this same same kit on order and changed my order (the voices in my head got too loud) to a kit that I thought would have been delivered by now, I'll be watching this thread between swift kicks to my own head.
 
Hi all - thanks for the replies and interest so far!

K'Tesh said:
But will it be able to do the Kessel Run in less than twelve Parsecs?
Click to expand...
watermelonman said:
Closer to eleven!
Click to expand...
Indeed. ;)

dixontj93060 said:
Looks like a screamer!
Click to expand...
Most definitely! Can't wait. By the way...

AlnessW said:
MissileWorks RRC2+
Click to expand...
This was the one I bought from you. :wink: Hasn't seen any action yet, but rest assured...

Wayco said:
Internal motor retention. Sandwich the bulkhead between the couplers and add a 3/8" nut to the center of the bulkhead. Most commercial motors use 3/8" threads in the forward closure. Since we already know you are flying EX, it's a moot point. I'm sure you have another method for motor retention. Any left over parts I'd be glad to take off your hands....
Subscribed. Love this rocket, my full up ( with payload) Mongoose flew to 28,905 ft. on an M840.
Click to expand...
Thanks for the info! That was my best guess on the extra parts. So, would one glue that assembly together, bolt it to the motor, then bolt inside the airframe? (I used a similar method with Power Line Seeker II.) 3/8"-16 threads are common for both commercial and EX 75mm motors, at least in my experience - all of my 75mm snap-ring bulkheads are threaded that size. For motor retention in this rocket, I'll just friction fit it as I usually do for MD projects these days. Even if it were to pop out, it's still attached to the recovery harness, so no loss.

As for extra parts. :) I think I have something else in mind for my 24" upper section and av-bay coupler, but I'm sure you'd be welcome to the other bits and pieces... I actually have a couple of questions about your build, I saw the thread but looks like it never got finished.

You built the carbon fiber version, right?
No layups, correct? What epoxy?
Avionics?
Do you have any pictures or video of the M840 flight? I recall seeing mention of it in the AIRFest thread, but sounds like it didn't fly until later.

Apologies if the above was already covered elsewhere, I may have missed it...

patelldp said:
Have you considered reducing the size of the fins? It appears the goal of this project is to maximize altitude and that would be one very important step to get as much as you can out of this rocket.
Click to expand...
Yes, perhaps - though "full bore altitude optimization" may be the focus of a separate project.

patelldp said:
Additionally, you're doubling up on your GPS electronics. Any reason to not trust the 100mW BRB? Have you considered swapping over to a Telemetrum or an AIM Xtra 2.0 for maximum functionality and reduced weight/internal volume requirements?
Click to expand...
Bat-mite said:
That was my question...why two GPS units?
Click to expand...
Same reason as 2 altimeters = redundancy. Am I not trusting the 70cm 100mW Beeline? No, not at all, in fact I'd trust it very well. But having a backup system on board never hurts. I've never flown any of the Altus Metrum/Entacore products so I'm sticking to what I'm familiar with. And yes, I'll absolutely test everything on the ground beforehand to ensure there won't be any interference. (Shouldn't be a problem, but again, always good to test.)

Oh, one other thing. Our launch site is miles and miles of sagebrush which is very good at blocking RF signals, especially if you land in a valley or behind a hill.

SCrocketfan said:
I thought it was 14?

Very cool build AlnessW, will be following!
Click to expand...
Thanks, SCrocketfan!

Igotnothing said:
Since I had this same same kit on order and changed my order (the voices in my head got too loud) to a kit that I thought would have been delivered by now, I'll be watching this thread between swift kicks to my own head.
Click to expand...
Did you end up buying it, or not? Or switch to something different? Either way, thanks for following along - you coming to NXRS again this year?

watermelonman said:
He is building with black tubes again!
Click to expand...
Who, me? :)
 
AlnessW said:
Thanks for the info! That was my best guess on the extra parts. So, would one glue that assembly together, bolt it to the motor, then bolt inside the airframe? (I used a similar method with Power Line Seeker II.) 3/8"-16 threads are common for both commercial and EX 75mm motors, at least in my experience - all of my 75mm snap-ring bulkheads are threaded that size. For motor retention in this rocket, I'll just friction fit it as I usually do for MD projects these days. Even if it were to pop out, it's still attached to the recovery harness, so no loss.

As for extra parts. :) I think I have something else in mind for my 24" upper section and av-bay coupler, but I'm sure you'd be welcome to the other bits and pieces... I actually have a couple of questions about your build, I saw the thread but looks like it never got finished.

You built the carbon fiber version, right?
No layups, correct? What epoxy?
Avionics?
Do you have any pictures or video of the M840 flight? I recall seeing mention of it in the AIRFest thread, but sounds like it didn't fly until later.
Click to expand...

I attached my internal retainer using 6/32 flat head screws and pem nuts.
Yes, I built the CF version. Some comments from other members on here bothered me, so I didn't finish the build thread.
I got over it, and did manage to do a complete build thread on my Mongoose 54.
 https://www.rocketryforum.com/showthread.php?130487-Wayco-s-RW-Mongoose-54-build

No layups on any of my four MD rockets, Rocketpoxy throughout.
RRC3 primary, SLCF backup, with Featherweight magnetic switches. Eggfinder in the nosecone and a CSI RF tracker taped to the drogue shock cord.
All flights recovered using Eggfinder TX/RX. Full telemetry throughout the M840 flight.
Here is the video:

Our launch area has greasewood bushes, much like sagebush, maybe a little bigger. The above flight landed in a Mesquite tree with cats claw bushes surrounding it. Nasty stuff! Most of the rocket never touched the ground, but everyone on the recovery took some damage.
This is what a "Tree landing" looks like at Eagle Eye:
IMG_6471.jpg


IMG_6472.jpg


IMG_6473.jpg


 
Salvage-1 said:
Watching this one Wilson.... grin
Click to expand...
Thanks Rob for stopping by!

Wayco said:
I attached my internal retainer using 6/32 flat head screws and pem nuts.
Yes, I built the CF version. Some comments from other members on here bothered me, so I didn't finish the build thread.
I got over it, and did manage to do a complete build thread on my Mongoose 54.
[snip]
Click to expand...
Thank you for the info and visuals! Nice M840 flight. I have a better understanding of how that internal motor retainer works after seeing it in your Mongoose 54 thread, but like you said, it's a moot point in my scenario. Still good to know anyways.

Had a very productive weekend and got a bunch of work done on this thing.

IMG_4327.jpg
Requisite bathub soak photo... Yes, I even threw the fin alignment guides in there too, because why the hell not. Excuse the "extra" green FG parts - they're for a different project,

IMG_0799.jpg
Started by sanding and prepping the booster section and fins - done with 80-grit on a sanding block followed by 120-grit on the random-orbital sander.

IMG_0800.jpg
Fin #1 attached using Loctite E-120HP. Most people say that Proline/Rocketpoxy is stronger (and they're probably right), but I've had very good experiences with Loctite so far. If it ain't broken, don't fix it.

IMG_0818.jpg
After that cures, I did fins 2 and 3 simultaneously.

While the fins are curing, let's take a look at the av-bay setup. As I mentioned earlier, I'm using the nosecone coupler as an av-bay (including the switch band) - it's only 5.125" long and will need to house all avionics, since my nosecone is serving as my main parachute bay. Building my 54mm av-bay with 2 altimeters and 2 9V batteries was a much greater challenge...

IMG_0813.jpg
Cut a few 1/4"-20 all-thread rods to length, drill holes in the (CNC-stepped) av-bay bulkheads, and set aside a collection of forged eyebolts, nuts, washers, and wingnuts. The ends of the all-thread rods are a little rusty as they were "recycled" from an old project.

IMG_0814.jpg
And then assemble accordingly - all standard stuff here.

IMG_0816.jpg
Av-bay buttons up pretty nicely. Now all it needs is a switch band!

The other thing I did for this project last weekend was mix the motor... Funny, since the rocket doesn't even fully exist yet and I don't have the hardware, either. I guess that's how it goes for me these days! Anyways, I have a nice 75/7600 load sitting in the shop now, just waiting for action.

Up next = fillets. Looks like we're well on-track for a February 27 launch date.
 
MarkH said:
FWIW. I've flown the BRB 100mW GPS, a 250mW 900MHz GPS transmitter, Raven and Stratto logger all in the same bay on two flights over 30k and had no issues with any of them.
Click to expand...

This is good news!
Did you do it with a 5.5 inch avbay with all thread running through it? I'm thinking space would be more of a factor than compatibility.
I'm planning to put an Eggfinder TRS and an RRC3 into the nosecone coupler of my 3" Punisher. Hopefully without the all thread, which can really kill the telemetry signal with smaller transmitters like the Eggfinder has.
 
MarkH said:
FWIW. I've flown the BRB 100mW GPS, a 250mW 900MHz GPS transmitter, Raven and Stratto logger all in the same bay on two flights over 30k and had no issues with any of them.
Click to expand...
Great to know - thanks!

Wayco said:
This is good news!
Did you do it with a 5.5 inch avbay with all thread running through it? I'm thinking space would be more of a factor than compatibility.
I'm planning to put an Eggfinder TRS and an RRC3 into the nosecone coupler of my 3" Punisher. Hopefully without the all thread, which can really kill the telemetry signal with smaller transmitters like the Eggfinder has.
Click to expand...
Yes, it should be a tight fit, but with some careful planning I think it'll happen. TBD once I assemble the sled and have all components in hand. Also, the transmitters will be simply bubble-wrapped and placed inside the bay, not mounted anywhere.
 
Now for my favorite part of building fin cans - fillets. Got all 3 sets done last night!

IMG_0820.jpg
With a little convincing, the fin alignment guides popped off pretty easily.

IMG_0822.jpg
Hey, it looks like a rocket now!

IMG_0823.jpg
As I mentioned in my OP, I used Loctite 9462 for filleting. I get these cartridges of it from McMaster, as well as the dispensing gun. And course, their disposable mixer nozzles are a godsend for doing fillets.

What I really like about 9462 is that its very thick - about the consistency of Pillsbury cake icing. Because of the high viscosity, you can do one set of fillets, then rotate the airframe and do the next set, and so on without the fillets sagging. This is a real time-saver!

IMG_0824.jpg
Now you see how it goes together.

IMG_0826.jpg
And done! This photo didn't come out very well, but you get the idea. For all 3 sets of fillets, I only needed just a tad over 2 cartridges total. (I had budgeted for 3 or so.)

I usually use a tongue depressor for shaping fillets, but it was too narrow for the width of epoxy I wanted. Since this is stuff is thicker than E-120HP, it's less forgiving about smoothing out by itself. Did the first set and they came out pretty lumpy, so I looked for a different tool to use. A 1.25" dowel was too small, and a 75mm scrap piece of casting tube was too big. So I then tried a scrap piece of 54mm liner, and bingo! Perfect size/diameter for fillet shaping.

As mentioned above, I was able to do all 3 sets one after the other. I spent probably about half an hour on each set, making sure they were shaped properly, etc. This stuff takes several days to fully cure, so we'll let her sit for a while.

Getting closer by the day! Next up will be the av-bay, recovery harnesses, and chutes - and that should just about do it...
 
Worked on this thing a bunch over the weekend, but not a ton to report on here.

IMG_0829.jpg
Fin can looking sexy with fillets.

IMG_0828.jpg
With this mostly done, time to move on to the av-bay. #2-56 shear pin holes drilled and in place.

IMG_0830.jpg
Here are the individual components (sans sled) - innards, 2 x 3/4" CPVC caps, and 4 x Euro-style terminal blocks.

IMG_0833.jpg
New Raven3 - I just love how he ships these in jewellery boxes...

IMG_0834.jpg
Recovery lineup - Raven3 and an RRC2+ (thanks to dixontj93060!) for backup.

IMG_0835.jpg
Sled cut using the scroll saw from 3/16" plywood (I always thought using G10 sheet for this purpose was overkill) with altimeters mounted in place. I don't have the switches yet, so their location is simply sketched in for the time being. Given the size of this bay and the fact we're trying to cram both altimeters plus 2 x GPS units in here, we have to get a little creative with space. I made the sled as large as possible and I'm liking the layout so far. The 2 x 9V batteries mounted on the back could make for a challenge, but we'll figure that out when the time comes. And no, I won't use LiPos.

IMG_0837.jpg
Aft (drogue) end of the bay all put together. My surgical tubing charges will be attached to those terminal blocks.

IMG_0838.jpg
And the forward (main) end with terminal blocks and charge caps. (No need to use surgical tubing here.) Originally I was going to use 1/4"-20 wingnuts to secure this end, but those were swapped out for standard hex nuts due to space limitations.

IMG_0839.jpg
Last up for today we glue the switch band in place. Rough up both surfaces to be bonded, mix up a small batch of E-120HP, align shear pin holes with airframe, and done.

Getting closer by the day...
 

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