Full Clip - 54mm MD build

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drew
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Full Clip - 54mm MD build

Postby drew » Sun Oct 07, 2018 11:05 pm

So I've had an L935 sitting with Blake since 2016 or so as I wanted to fly it in a MD airframe at Westmar. Since the purchase Head End Deploy has become a bit of a thing in MD circles, as can be seen by the Wildman "Mach 2" kit. After looking at this rocket design and wanting to incorporate a cable cutter to deploy my main I decided to do away with the conventional AV Bay and instead do something more aggressive. I've built a single break Head End Deploy design that also incorporates a 54mm plugged forward closure threaded rod to serve as a motor mount. See below.

Here's a shot of the fully assembled Nose Cone/AV Bay/motor mount.
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Here's a fully disassembled shot.
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AV Bay in "Mach 2" airframe demonstrating how much of the AV Bay/coupling shoulder will be epoxied recessed in the airframe.
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CTI 54mm plugged forward closure seated against the aft bulkhead.
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Avionics - will be flown with a single axis Raven 2 or dual axis Raven 3 and TeleGPS 1.0.
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I've got the airframe rolled and fins aren't that far out. And there's heaps more left to do. But this is a decent start. Below is a Openrocket sim of a slightly longer and lighter vehicle. I've cut down the AV Bay by 15-20mm from the sim and I always build heavier than any of my preliminary sims. Still, looks good to me!

Image
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

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SpaceManMat
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Re: Full Clip - 54mm MD build

Postby SpaceManMat » Mon Oct 08, 2018 6:12 pm

Wow that looks pretty sweet to me :!: Big motor, little room for anything else 8)
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

drew
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Re: Full Clip - 54mm MD build

Postby drew » Mon Oct 08, 2018 6:21 pm

SpaceManMat wrote:Wow that looks pretty sweet to me:!: Big motor, little room for anything else 8)


Thanks d00d! Should be a fun flight. :D

For the record every flight I'm planning for THUNDA2 will be leveraging this design in some manner. I'm going to fly a M2245 in a 75mm version of what's above and my two stage stack will have a 54mm sustainer quite similar to above. I won't be able to epoxy the coupler in place on that rocket as I'll need to wire up the HEI forward closure to the staging altimeter before flight so instead I'm going to use a "puck" with some nuts and use countersunk screws to hold the AV Bay to the airframe. The coupler will also be longer as hopefully I'll be fitting a GoPro Session 5 in the NC as well.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

matthew
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Re: Full Clip - 54mm MD build

Postby matthew » Wed Oct 10, 2018 9:02 pm

This is one of those moments where I said to myself "I wish I'd thought of that."

Nice design, drew. I'm looking forward to seeing it in person. :D
Matthew Small
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TRA #11466 L3
QRS #133


http://australianrocketry.org

drew
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Re: Full Clip - 54mm MD build

Postby drew » Thu Oct 11, 2018 12:27 pm

Thanks for the kind works Matthew, I do appreciate it. I must admit I've been mulling this design over in my head for months now attempting to eliminate any pitfalls in the design before I attempt to fly it. I think I've considered most issues but I'm more than willing to listen to any comments about "blind spots" I've not considered.

First off, I have had some concerns about the rocket still being stable post apogee event as I'll only be popping the NC off and leaving the AV bay (and all that mass) in the airframe. I'm not confident the drag of the open ended NC will be enough to stop the rest of the airframe from staying stable, especially considering the fact that there's a sealed bulkhead at the front of the rocket instead of a draggy open airframe. Hence the inclusion of a drogue which historically I've not used in MD designs as I've always been a drogueless sort of guy.

But flying a drogue when I'll most likely be having apogee deployment near or in the jet stream concerns me from a drogue chute shred perspective. So to mitigate this I'll using X-type chutes for the drogue. Top Flight makes X-types at a reasonable price so I'll be ordering a handful of them. Ideally I'd like a 10" reinforced drogue but Top Flight only makes their reinforced drogues in 18" or greater. I suspect I'll "test" the 10" standard x-type on the back of my car somewhere remote to see if it shreds in 100kmh speeds as well as test fit the 18" in the 54mm nose cone. I might move to a smaller main and larger drogue if required.

I've also had some concerns about the main chute burrito wrapped getting tangled as it'll be on the airframe/av bay side of the harness and not on the NC. So I'm hoping to mitigate that by weaving the kevlar recovery harness through the nomex a couple times so the harness is part of the burrito instead of separate to it. That should hopefully mitigate that concern.

Finally, given the expected apogee altitude I'm going to use aluminum cannon/cannons for apogee deployment. Ideally I'll have them recessed in the AV Bay but we'll see as real estate will be tight!

If you or anyone else can think of anything I've not considered I'd love to hear it. I'm not aware of anyone who's flown a design quite like this so any advice is welcome.

drew
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

vance2loud
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Re: Full Clip - 54mm MD build

Postby vance2loud » Thu Oct 11, 2018 3:57 pm

If you are worried about shredding a drouge you could also consider the rocketman ballistic drogues, they come in a 1 foot size and are meant to handle deployment at speeds up to 1000 mph. So long as the rest of the recovery gear can handle it.
http://the-rocketman.com/chutes.html
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drew
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Re: Full Clip - 54mm MD build

Postby drew » Thu Oct 11, 2018 4:29 pm

Cheers for that vance2loud. I had looked at those but considering I can buy 4 Top Flight X-type drogues for the price of 1 12" RocketMan Ballistic Mach II drogues I figured it's worth it to check out the Top Flight offerings first. Basically I was concerned that using a Top Flight thin mill chute for drogue (my go to for small space MD chutes) wouldn't be strong enough for the jet stream. X-type/cruciform chutes have a low Cd which is an advantage for high speed drogues.

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From here.
https://fruitychutes.com/files/blog/NARCON%202013%20-%20Rocket%20Recovery%20Technology.pdf

Price breakdown.

Top Flight X-Types

X-TYPE PARACHUTES
2x XTPAR-10 10" $6.95 each
ULTRA-X-TYPE WITH FLAT-BRAIDED NYLON LINES REINFORCED
UXTPAR-18 18" $13.95
UXTPAR-24 24" $15.95
Total = $43.80 USD

Single RocketMan Ballistic Mach II 12" chute = $50 USD
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

drew
Southern fried goodness
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Posts: 947
Joined: Sat Aug 01, 2009 10:20 pm
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Re: Full Clip - 54mm MD build

Postby drew » Fri Oct 19, 2018 3:47 pm

Just a quick update, I posted on TRF regarding the Top Flight X-Type chutes and what speeds they can withstand. Preston Noble, the proprietor of Top Flight LLC, chimed in on the thread and it looks like I'll be getting him to make me two 10" Ultra X-Types.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015


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