L3 - 5" extended Jart- Build Complete

[Salvage-1]

I haven't really had a productive 'winter season'. My garage is an absolute disaster, and not the usual nice work space that has been in the past.

That being said, the biggest local club launch of the year is fast approaching and I wanna take something 'big' to fly.

I had planned on doing a 4" Broken Arrow, but, I seem to be missing some parts, they are in here somewhere, but...... looking around, I saw something in the corner that desperately needed attention. I got a 5" Jart bottom half. After a couple of comments, my dearest other half arranged for a nice pressie. Father's Day this year will be celebrated by the launch of a large Jart!!! or two...

I will go get pics and leave you to guess the rest. The only clue, is that this CTi person will be happily throwing an AT DMS in the air pretty soon.:eyepop:

 

[Salvage-1]

The two ass ends of a Jart. Both 5". One 54mm. One not.

 

[Salvage-1]

One red, one black one, and one with a little.... erm... not now Salvage...

So, it's a game of spot the difference.

As you can see, there is room for expansion. I got two extensions, both with 8" couplers. One is 8" one is 16". Add them to the bottom ends and you can fly any 54mm or 75mm motor!!!! Yes, it fits the 6XL CTi, so... M840 is an option down the road.

Started on the switch band and sprayed the black one down to get all the dust and crap off it. Not in the shower, just a hose outside (sorry CA residents).

Going back inside to work on the bulkheads. More pics soon.

 

[Salvage-1]

Got the bulkheads done. I love my drillpress for things like this.
Charge wells are 12gauge shotshells. A brass bolt goes through the primer hole, and through the bulkhead. It is secured with a nut on the inside and then the terminal connectors are screwed onto the bolt. Twin holes for the ematch to go through, which will be tape/putty covered when 'live' so no nasty gasses get inside.

Now to work on the nose a little.

 

[Salvage-1]

Electronic bay nearly done... Just have to get some more electronics in there.
There will be two deployment altimeters in there, a Stratologger and an Adept22 as backup, plus a BRB 900 for tracking.
Triple Schurter rotary switches (my favorites for electronics bays) and 3 holes for air sampling (3/16")

 

[gerbs4me]

Alt. Bay looks good, clever idea using shotgun shells for the wells.

 

[Salvage-1]

Thanks. I have been looking for something that would withstand the 'explosion' of the deployment charges. Used shotgun shells are plentiful in this garage, I used to reload for Cowboy Action Shooting. I color coded them too. Green for Main altimeter, Gold for Backup altimeter.

Got the holes drilled in the nosecone for three 4-40 nylon screws as shear pins.

I have got a 72" Ultra Iris Toroidal chute for the main. Yeah, a 72" seems too small, but these chutes have a Cd of 2.2 and Rocksim simulates landing speed of only 16.5 ft/sec which is well inside my safety zone. I managed to wrap it in a 24"x24" nomex protector, with 3/4" tubular nylon shock cord, and it all fits in. Main parachute deployment will be 2cc of 4Fg which should easily shear those pins and pop the nose off. Testing that tomorrow.
The aluminum Bulkheads will also make this beast an ease to clean afterwards!


Yes... this will be my L3 rocket! Planning to test the altimeter on the 54mm fin can and then fly an AT M1350 DMS in it for the L3. It sims at 15000 ft and 1250ft/sec. This Jart is going Mach and 3 miles high.

 

[Salvage-1]

attached RockSim file and stability diagrams.





View attachment SupaJart_75 slightly stretched.rkt

 

[chuck5395]

Looking good Rob.
Nothing like waiting until the last minute though.

 

[Salvage-1]

whatchamean?? we have 3 weeks left.

 

[Salvage-1]

Motors finalised.

Test with 54mm - AT L1000 DMS

L3 Flight in 75mm - AT M1350 DMS

---

3d Printed Camera Shrouds ordered for my 808 keychain and Mobius video camera.

 

[gerbs4me]

Thanks. I have been looking for something that would withstand the 'explosion' of the deployment charges. Used shotgun shells are plentiful in this garage, I used to reload for Cowboy Action Shooting. I color coded them too. Green for Main altimeter, Gold for Backup altimeter.

Got the holes drilled in the nosecone for three 4-40 nylon screws as shear pins.

I have got a 72" Ultra Iris Toroidal chute for the main. Yeah, a 72" seems too small, but these chutes have a Cd of 2.2 and Rocksim simulates landing speed of only 16.5 ft/sec which is well inside my safety zone. I managed to wrap it in a 24"x24" nomex protector, with 3/4" tubular nylon shock cord, and it all fits in. Main parachute deployment will be 2cc of 4Fg which should easily shear those pins and pop the nose off. Testing that tomorrow.
The aluminum Bulkheads will also make this beast an ease to clean afterwards!


Yes... this will be my L3 rocket! Planning to test the altimeter on the 54mm fin can and then fly an AT M1350 DMS in it for the L3. It sims at 15000 ft and 1250ft/sec. This Jart is going Mach and 3 miles high.

Color coded shells is very clever! I may have to try that.

 

[Salvage-1]

Got some more work done tonight. Connected the shorter of the two extensions up. Also got the 75mm retainer body on, and the rear centering ring tacked on with CA

This nearly completes the 54mm version of this Jart. Just got to pad out the Altimeter bay with things like ... erm ... altimeters and stuff. This will offset my weight etc, but not much.

Talking about weights, got the 54mm all packed with chutes, shock cords, etc. Ready for its first official weigh in.

And.....

It must have been eating left over epoxy cos it got heavy real fast. 12lb 12oz unloaded with the CoG at 29.5".
This is fine for the 54mm loads, but, running the numbers through RockSim and I get a stability of .96 for the 75mm version with the 8" extension.
I then swapped the 16" for the 8" and stability increased to 1.38 at launch. The rod that this will be going off is 144" and the sim puts it at 107ft/sec leaving the end of that. Not quite the slow pig launch that I expected, but, the peak thrust of the M1350 is 1765N and T/W is 16:1.

 

[Salvage-1]

Got the front centering ring drilled and the U bolts installed. Taped the fins on so that I could slide that centering ring down and tack it in place with CA.

 

[Nick@JET]

I'm sure you have thought of this but is this the same AT L1000 that has issues? Hopefully not one that has been recalled

Looking forward to seeing the flight reports.

 

[Salvage-1]

Yes, some of the lot numbers of the AT L1000 DMS were recalled. I have only just (like yesterday) ordered mine, and so I shouldn't get one of the suspect lot numbers as they should have been sent back to Aerotech already.

 

[Salvage-1]

Before I went to bed, I beefed up the 'inside' area of the two centering rings (the sides that meet the fins) with a couple of dollops of 30 min hobby epoxy.

When I got back to it this afternoon, I thought a quick dry fit would be the way to go. Well.. this dry fit could have done with a little lube. After a lot of squeaking, which sent the dogs berserk barking, and then some persuasive taps with a 2 by 4 (literal with the 2 by 4), and the motor mount assembly was in place. Then.... it wouldn't move. Taking this as a 'process', I smacked the fins into their holes to see how they fit. Squeak.. whack whack. whack.. and they are in place.

The fit is so tight and solid that I am going to go to the next step of internal fillets. More on this when I find out where I hid those horse syringes.

Off to get a photo as this thing sits currently.

 

[Salvage-1]

Stuffed all the laundry into the relevant spaces and did a weight and CG check.

The ‘final’ weight of the 54mm fin can, nose, av bay, and 8” extension is 12lb 12oz with the CP 29.5” from the nose.

The weight of the 75mm fin can, nose, av bay, and 8” extension is 12lb 14oz with the CP 29.6” from the front.

The 75mm fin can, nose, av bay, and 16” extension is 13lb 10oz with the CP 33.7” from the nose.

Running the calculations through Rocksim, this shows that I will be able to run the M1350 with the 8” extension for a calculated stability of 2.03 16" extension for a calculated loaded stability of 1.38
This will of course change when I start adding epoxy to the rear end.

I also drilled 3 holes in the rear centering ring, one between each fin, to allow me to inject my epoxy mix into the can space. This will form the internal fillets between the motor mount and the fins, and also reinforce the joints between the centering rings, the motor mount and the fins.

I will be using West Systems 105/206 for this.

 

[gerbs4me]

What altitude is it simmed out to?

 

[Salvage-1]

The M1350, as is without at these weights.
Max Alt 13550ft,
Max velocity 1304ft/sec (roughly Mach 1.2)
Max gee's 17

I expect those numbers to drop a little.

 

[Salvage-1]

Spent the evening at the house of one of my TAPS, discussing this project, and basic bs'ing. This TAP is one of the ones that likes to put doughnuts on the nosecone of a rocket to please the rocket god. Then finds that they don't like the sugar frosted ones.
Anyhoo... everything looks right and fine. Tomorrow I will continue.

 

[gerbs4me]

The M1350, as is without at these weights.
Max Alt 13550ft,
Max velocity 1304ft/sec (roughly Mach 1.2)
Max gee's 17

I expect those numbers to drop a little.

Very cool!

 

[PeterEkstrom]

Spent the evening at the house of one of my TAPS, discussing this project, and basic bs'ing. This TAP is one of the ones that likes to put doughnuts on the nosecone of a rocket to please the rocket god. Then finds that they don't like the sugar frosted ones.
Anyhoo... everything looks right and fine. Tomorrow I will continue.

Just so long as you don't blame me for breaking you 54mm fin can.:grin:

 

[Salvage-1]

Just so long as you don't blame me for breaking you 54mm fin can.:grin:

Nah, that one was my clumsiness, which was quite funny as it happened just after you were explaining that you were known for your clumsiness, and then knocked over one of your nosecones.
That one will be an easy fix, lots of surface area on the fillet break, i will dremel some channels and holes to work as anchor points, and I will drill and inject internal fillets to the 54mm can.
It was actually fortunate that it broke, as the same would have probably happened at the launch, better to fix it now and make it stronger.


Went into the local feed store and grabbed a couple of handfuls of the LARGE syringes, then walked up to the counter whilst announcing to the owner that I had just started watching Breaking Bad again. He just looked up and replied "you'll need a lot more than that, would you like a box?"

So, that's the syringes bought... no reason to not work on getting the fins in place tonight.

--
Extra

Two of the things that were discussed last night have been changed in the rocket design
Now there are two kevlar shock cords extensions, each about 2ft long, that go between the AV bay and the main shock cord. This means that all the tubular nylon can be inside the fire blanket and the only part of the shock cord that is anywhere near the black powder when it goes off are pure 1/2" tubular kevlar.
The other change was to the drogue chute. I was planning on using a standard 1.1m X form chute at 36". I am changing this to a Binder 36/40" octagonal chute. This has far stronger shroud lines and I believe 1.3m for the chute. This also slows the drogue fall down to 67ft/sec. A little longer walk, but I don't mind that if it leads to a successful recovery. This is one flight I don't want chute problems with!

--
edit 2

Just finished sewing two sleeves for the kevlar section of the shock cord. It now has its own nomex shroud to keep it safe and happy.

No no, I'm not overly concerned about a safe recovery...

 

[Salvage-1]

Got the electronics bay done.

Space left for the TeleMega in the future (when I get licensed), and for the moment, I have an Adept22, and a Stratologger.
Adept 22 is connected to a brand spanking new, straight out of the wrapper, Panasonic "Digital" 9V battery, the Stratologger is on a 2S 7.4V 430mAh Lithium.

Connections between almost everything are with JST connectors, easy to disconnect and reconnect.

Switches all wired, rubber grommits behind switches on the inside to hide my messy drilling and protect hands from shards.


Ordered 75mm-54mm adapter just in case the 54mm fin can isnt available for some reason or another (like I didnt get around to fixing it)

 

[Salvage-1]

Labelled all those little connectors

Set up is

Adept 22 - Drogue @ Apogee, Main @ 600ft
Stratologger - Drogue @ +1, Main @ 500ft

 

[chuck5395]

This is getting really real now.
I'm excited to see this flight.

 

[patelldp]

Be careful with that Adept22 near RF trackers.

 

[Salvage-1]

This is getting really real now.
I'm excited to see this flight.

... and I am already starting to get nervous.....

Be careful with that Adept22 near RF trackers.

I have flown this Adept22 with this BRB900 at few times and havent had any problems. I am still planning to paste foil behind the Adept, and also set everything up live in the garden, and then leave it a couple of hours, just to make sure.

I am not sure but I think that the Adept / BRB problem is with the HAM licensed versions, they put out quite a bit more oooomph.

 

[chuck5395]

... and I am already starting to get nervous.....

That's a good thing