Opinions wanted on 24mm MD setup.

[Andrew_ASC]

Scratchbuilt 24mm custom MD bird with supersonic airfoils. Take off mass 288 grams w/motor. Plans motor eject CTI G-145 L-1 HPR motor. Apogee deploy and radio beacon track via Telemini.

Recovery gear.
Apogee #300 Kevlar ten feet because a Blackhawk24 has 9 ft.
Dino X foil chute 12”.
3” Nomex square.

If you guys think it’s too light of a setup let me know. Should I skip a D link? I’ve never done a 24mm MD rocket until now. And it’s not a kit. Planning on epoxying shock cord to a coupler and coupler epoxy to airframe. Then epoxying shock cord to nose.

 

[Andrew_ASC]

I like the fact the #300 cord packs nice. Upon doing further research a Blackhawk 24 shock cord is thicker stuff. I may try to see how a 3/16” onebadhawk harness fits. I think I should keep length at ten feet.

 

[Eric]

3/16" is way to big. 1/8" would still be overkill. 300-500lb is good. Just make it twice as long. How are you attaching your shock cord to the rocket?

 

[Eric]

And let's see those fillets....

 

[Andrew_ASC]

Here is some #500 shock cord. I’ll have to see if airframe can handle twenty feet. It’s extremely cramped.

https://www.siriusrocketry.biz/isho...MI6sqDtv6t3QIVzWV-Ch0PQQ2NEAQYAiABEgL4X_D_BwE

 

[Estesbasher]

my 24mm and 29mm, I'll set up the anchor for the recovery the same way. I made a 24mm, coupler tube from fiberglass and carbon sleeves, It's probably 3/16" thick. I would do the 300 pounds for the anchor side also. If you use the 500# it's just going to take up a lot of space. Estes 24mm. tubes fit inside the 29mm. coupler tube. So I can use the same type of anchor on both 24mm. and 29mm. rockets.

 

[Andrew_ASC]

Tossing the Dino chute for the Top Flight Recovery thin mill 12”. Had problems packing the square chute tightly.

 

[Eric]

Here is 21' of of 500lb. It measure .065" in a square braid. It weighs 10 grams. And you can decide if it will fit based on the picture. It's not rolled tight.

 

[Andrew_ASC]

About half of that “might” fit just guessing.

 

[Eric]

A longer length of 250lb?

 

[Andrew_ASC]

You underestimate the scale we are dealing with Eric. A similar kit uses 9 ft of cord lol.

 

[Andrew_ASC]

https://wildmanrocketry.com/products/blackhawk-24

Here it has three yards of Kevlar.

 

[Eric]

I understand that length is provided. Are there many rocketeers that wouldn't recommend a longer shock cord?

 

[Andrew_ASC]

I think this is a rare case where the rocket is so lightweight it can deal with 10-15 ft of lightweight cord. I’ll have to see in a week or two how each recovery system can fit inside it. Not epoxying anything yet.

 

[Andrew_ASC]

The Blackhawk 24 is 170 grams airframe only. Mine is 126 grams give or take a gram. My nosecone is 31.8 grams. Airframe only no casing or motor. So that’s what we’re dealing with mass wise with 0.6 gram bp on a CTI pro 24 reload.

 

[Andrew_ASC]

This site at Jon rocket has the masses of the Top flight chutes.

https://jonrocket.com/store/products/parachute-12-standard-thin-mill-nylon

 

[Eric]

This site at Jon rocket has the masses of the Top flight chutes.

https://jonrocket.com/store/products/parachute-12-standard-thin-mill-nylon

Those are close, but a little off. I just order a TFR 30" thin mill. That site has it listed at 1.2oz. Preston just told me the other night that it was actually 1.0oz for thin mil, and 1.3oz for standard.

 

[Andrew_ASC]

Thanks I’ll call sometime or just weigh it when it gets here.

 

[OverTheTop]

I understand that length is provided. Are there many rocketeers that wouldn't recommend a longer shock cord?

I tend to fly shorter. I do z-fold the harness and tape it with masking tape. I think the tearing of the masking tape absorbs energy and also manages to give a good tug on the airframe to get it rotating around to somewhat inline with the NC before the harness is straightened out.

 

[HASTE]

I have a BH 24 I fly regularly on the supplied chute it came with.
With the empty 24mm CTI 6 grain in still recovers nicely, on 6 foot of standard S/C from Wildman.
Only recovery issue I have had with this was when it perched itself high in a tree, reached for the STIHL tree came down on BH 24 knocking a fin off .

 

[Andrew_ASC]

Well there’s the problem is I have no clue what “standard” shock cord came with a BH24. I’m assuming it’s in the #500 range.

 

[boatgeek]

Would dog barf or a dog barf/Estes wadding combo be lighter than the Nomex blanket? It might take too much space, but is something to consider.

I regularly recover a 400-gram bird on a basic 12" flat chute. Go with manufacturer recommendations, but you may be able to go smaller on your chute if you don't have it ordered already. Definitely dump the quick link and tie a good bowline to the chute and a small loop glued into the nose cone.

 

[tim cubbedge]

Hey if that rocket is so light, what about using a streamer?

 

[Andrew_ASC]

Thought about a streamer long ago when I had flat plate fins. Descent rate was crazy high. When I went airfoiled I committed to a small chute.

Also found a different mass for the top flight thin mill 12” as 0.2 oz at this place.

https://store.heavenlyhobbies.com/18-001-p12t.html

 

[Andrew_ASC]

With a standard 12” chute it’s still predicting 25.5 ft/s. I’d like the fins to survive if possible. Granted I may have to walk a mile or two after that G motor. I can play around with the 9” chute in the sim later for if it’s windier.

 

[Nytrunner]

What's the coast time after burnout, and will the full delay time of 15s be adequate if attempting motor-backup?

(I haven't read your other thread in detail if this has been discussed already)

 

[Andrew_ASC]

What's the coast time after burnout, and will the full delay time of 15s be adequate if attempting motor-backup?

(I haven't read your other thread in detail if this has been discussed already)

Sims say 15-15.8s after burnout. Apogee is like 16.8s. It’s a one second burn. I was just gonna run motor eject. It seems the difference is like 10ft between adding a seperate deploy charge. It’s close enough. I chose the G-145 for motor eject since it’s delay is 15s.

 

[Andrew_ASC]

Would dog barf or a dog barf/Estes wadding combo be lighter than the Nomex blanket? It might take too much space, but is something to consider.

I regularly recover a 400-gram bird on a basic 12" flat chute. Go with manufacturer recommendations, but you may be able to go smaller on your chute if you don't have it ordered already. Definitely dump the quick link and tie a good bowline to the chute and a small loop glued into the nose cone.

Yeah there were some heavier multistage rockets 29mm MD recovered on 12” chutes that I have experience with. I ordered 9” and a 12” TFR thin mill chutes. I’ll have to check descent rate on a 9” chute again. I bought the 9” also because it was so cheap to acquire. The wind drift would be less on a 9” but those fins may be single use worst case. I’d take a long hike over single use fins if I can help it. I’m going to have to experiment with whatever packs well. Plus the 9” one says it doesn’t support the airframe weight at standard rate or anything. Already found out the Dino chute was a no go.

I’ll probably skip the dog barf and go with cut down nomex. Thanks for advice on the knot.

 

[blackjack2564]

Forget nomex on 24mm. Use Estes tissue wadding.......
If your lucky and the airframe is "just' right" you can friction fit partially with shock cord!
Use small piece of tape to hold 3-4inch of cord on side of case, and stuff into airframe, wedging cord between motor & airframe.
Saves all the hassle & weight of coupler/glue/cord attachment.
Give cord good tug, making sure it will hold/work. You may have to add more tape...ala normal friction fit to make it work.
A German visiting flier showed me that trick few years ago [Dennis the menace we called him] loved that guy.
Then use folded Estes tissues and place on top of motor to handle initial charge blast.
On top of that put all the shock cord to further protect chute.
Ditch the nomex and wrap chute with Estes tissue wadding, doubled up. [2 layers thick]
Burrito style, just like I showed you.
Must think outside the box on tiny stuff.

For reference , I flew BH-24 on F-24-7's for testing and it would go around 12-1400ft depending on conditions.
No one at our club could visually track the darn thing.
Your is much smaller & lighter, you should see much higher altitudes ,I would test on that motor if you have the case...plus you get 3 reloads per pack.
Good luck & have fun!

 

[BrAdam]

Forget nomex on 24mm. Use Estes tissue wadding.......
If your lucky and the airframe is "just' right" you can friction fit partially with shock cord!
Use small piece of tape to hold 3-4inch of cord on side of case, and stuff into airframe, wedging cord between motor & airframe.
Saves all the hassle & weight of coupler/glue/cord attachment.
Give cord good tug, making sure it will hold/work. You may have to add more tape...ala normal friction fit to make it work.
A German visiting flier showed me that trick few years ago [Dennis the menace we called him] loved that guy.
Then use folded Estes tissues and place on top of motor to handle initial charge blast.
On top of that put all the shock cord to further protect chute.
Ditch the nomex and wrap chute with Estes tissue wadding, doubled up. [2 layers thick]
Burrito style, just like I showed you.
Must think outside the box on tiny stuff.

For reference , I flew BH-24 on F-24-7's for testing and it would go around 12-1400ft depending on conditions.
No one at our club could visually track the darn thing.
Your is much smaller & lighter, you should see much higher altitudes ,I would test on that motor if you have the case...plus you get 3 reloads per pack.
Good luck & have fun!

Jim,

You are the greatest.
Always have ideas or answers to help others.

Brad