O3400 Min Diameter L3

[airforcetp1991]

Have a look at some of the builds by cryoscum. He held the Tripoli O class commercial record for altitude and speed. O3400 to 66k' and M3.6 IIRC

Here are a couple of his threads on the Australia forum:
https://forum.ausrocketry.com/viewtopic.php?f=10&t=4666https://forum.ausrocketry.com/viewtopic.php?f=10&t=4253https://forum.ausrocketry.com/viewtopic.php?f=10&t=3659
There should be some useful information there .

Enjoy the build!

His engineering and fabrication solutions are incredible!

 

[airforcetp1991]

I agree. My recent 90g flight was built similar to this. As few joints and as little unsupported airframe as possible with a very, very strong coupler.

My 4" N project that's in the works for Balls is built exactly as you describe. Which, full disclosure, is also my level 3 project. Hence my interest I your build, Tony. I've already got multiple TAPs, so it's definitely not out of the question.



My solution to this is a Delrin disc that sits on top of the forward closure. It has a very slight taper to match the interior of the nosecone, adds stability to the joint and gives you a place for the shear pins.

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Very impressive! Are you planning to use the Piranha cutter? The AARD seemed like a solid product but I can’t seem to find one.

 

[THarrison]

That is a big concern I have as well and I liked the elegance of the Sub-min diameter builds in how everything was contained in the nosecone. That also eliminated the need for one of the joints at the switch band in my current design. I liked the Parana cable cutter for that concept a lot but the big thing that worried me was the use of BP at such a high altitude. I have read a lot of threads of people using the charge cannons successfully but it is something I have no experience with.

Did you have any issues with the fit of the nosecone on the case? Also maybe I am just not imagining it right, but where did you place the shear pins or equivalent if the NC was over the case?

-Tony

It was an EX case and a Performance Rocketry (Now Composite Warehouse) cone. I didn’t have any fit issues and it was pretty snug right on the case. Since it was an EX motor, I drilled the shear pin holes right into the very end of the case, above the bolt retention ring. All my electronics were armed out the tip of the nosecone and then I just screwed the tip on as the last step.

Todd

 

[airforcetp1991]

It was an EX case and a Performance Rocketry (Now Composite Warehouse) cone. I didn’t have any fit issues and it was pretty snug right on the case. Since it was an EX motor, I drilled the shear pin holes right into the very end of the case, above the bolt retention ring. All my electronics were armed out the tip of the nosecone and then I just screwed the tip on as the last step.

Todd

I will have to look at what my nosecone fit is on the hardware. I like the ability to avoid the added weight of the motor retainer as well.

Was it difficult to get the CG forward enough with the shorter overall length, I imagine you needed some ballast in the nose?

T

 

[watheyak]

Very impressive! Are you planning to use the Piranha cutter? The AARD seemed like a solid product but I can’t seem to find one.

I've been using Tinder's Mako cable cutters. He's really worked out all the cable cutter kinks with those. They're a little larger, but I even used one in my 2" L record, just for the added peace of mind. I've used a couple AARDs in the past. They work pretty well, but take some ingenuity to implement properly.

 

[GrouchoDuke]

Hash, I don't know you, but from reading your posts it seems like you've got your head on straight and have a good attitude about acknowledging the things you don't know and wanting to find those answers.

You're right that this is a very ambitious project - one that probably 99.9% of people here won't venture to replicate (even after their L3 cert). That doesn't mean that you shouldn't try though. If I translate your signature correctly, you're a zoomie with an aero degree - so you've been exposed to very tough things you don't know and had to fight through them (if you're still there, say hi to Havoc & Beaker for me). Keep asking questions, think through every problem (even the problems you don't know you have yet), and eat this elephant one bite at a time.

(Personally, G10 fins and screws don't make sense to me - but I haven't flown to Mach 3.5 either.)

I'll be watching - rock it!

 

[plugger]

If the fins are the same size yes I would agree that the 4 fin design is more stable...

What I was saying is that 4 fins allow you to make each fin smaller. There's not much point on adding a 4th fin to a 3 fin optimised design.

I agree the 7.5:1 is more efficient however from what I can tell based on this article (https://www.apogeerockets.com/education/downloads/Newsletter376.pdf) there is a point of diminishing returns past about a 5:1 ratio. Does that check, I am not an expert on this, but it would seem that at some point the increased surface area will create enough drag to overcome the more optimal shape?

Change your NC length from 24" to 30" and see what it does to your sim? I'm no expert either but I do expect it would increase your apogee.

And for the record, I'm not saying you shouldn't do this. Far from it, I hope you do. I'm just saying that I suspect the simmed apogee of 85k is probably not really achievable. It reminds me of the early 2010s where a whole slew of engineering students were adamant they were going to hit 100k on N5800 MD flights at Balls... I'm not sure if you're across those efforts but the TLDR is that they weren't successful.

I don't expect you'll carry the same hubris into your attempt that they did, but I honestly think adding ~15,000 ft on a MD record is a pretty hard achievement to attain.

 

[airforcetp1991]

Hash, I don't know you, but from reading your posts it seems like you've got your head on straight and have a good attitude about acknowledging the things you don't know and wanting to find those answers.

You're right that this is a very ambitious project - one that probably 99.9% of people here won't venture to replicate (even after their L3 cert). That doesn't mean that you shouldn't try though. If I translate your signature correctly, you're a zoomie with an aero degree - so you've been exposed to very tough things you don't know and had to fight through them (if you're still there, say hi to Havoc & Beaker for me). Keep asking questions, think through every problem (even the problems you don't know you have yet), and eat this elephant one bite at a time.

(Personally, G10 fins and screws don't make sense to me - but I haven't flown to Mach 3.5 either.)

I'll be watching - rock it!

I really appreciate the words and I know I will need much more wisdom like that if this project, or any other difficult one, is to succeed. I am an Aero zoomie, 2013, and I don’t remember a Beaker or Havoc but I wasn't tracking call signs much at that time to be honest. Is that a Viper in your picture? I’m out at Holloman now.

The screws and something I am torn on, I plan to use a pull scale and a piece of spare tubing to test how much load the screw head can withstand before pulling through the tube. If it isn’t large enough to make a difference I will likely scrap the idea.

-HASH

 

[GrouchoDuke]

I am an Aero zoomie, 2013, and I don’t remember a Beaker or Havoc but I wasn't tracking call signs much at that time to be honest. Is that a Viper in your picture? I’m out at Holloman now.

Beaker & Havoc got there after 2013. I think Sumo got there after you left too. Yeah, just farting around in the Viper in that photo (from a while ago...with an awesome Lockheed photog in the trunk). I'm sure I know some people out at HMN, but I'm not very good at keeping up with where everyone is now that I'm retired. (Everyone I know would be an "old guy.") Have fun out there!

 

[airforcetp1991]

What I was saying is that 4 fins allow you to make each fin smaller. There's not much point on adding a 4th fin to a 3 fin optimised design.


Change your NC length from 24" to 30" and see what it does to your sim? I'm no expert either but I do expect it would increase your apogee.

And for the record, I'm not saying you shouldn't do this. Far from it, I hope you do. I'm just saying that I suspect the simmed apogee of 85k is probably not really achievable. It reminds me of the early 2010s where a whole slew of engineering students were adamant they were going to hit 100k on N5800 MD flights at Balls... I'm not sure if you're across those efforts but the TLDR is that they weren't successful.

I don't expect you'll carry the same hubris into your attempt that they did, but I honestly think adding ~15,000 ft on a MD record is a pretty hard achievement to attain.

I agree the 85K’ number is very much a SIM dream and I think even if I had access to much higher fidelity sims there are still a ton of variables both in construction and the launch that could change things. I don’t see the “win line” as setting a record for this design/attempt and I hope that I would not be tempted to sacrifice design margins to chase a number.

Very true, the nosecone length/ratio does make a difference in the SIM. To be honest the 6:1 is also the highest fineness ratio I could find available and without the tools or knowledge to make it myself I figured that was the best choice.

What do you think of the choice of G10 for the fins, that was based on heat resistance and delamination concerns? My other thought was dragon plate.

Tony

 

[THarrison]

I will have to look at what my nosecone fit is on the hardware. I like the ability to avoid the added weight of the motor retainer as well.

Was it difficult to get the CG forward enough with the shorter overall length, I imagine you needed some ballast in the nose?

T

I didn’t need ballast or have any stability issues. The CG was already pretty far forward since it was all motor with heavy forward bulkhead.

As for your fins, I don’t think they’ll work. Unreinforced 3/16” G10 is going to buzz right off. If you absolutely can’t do tip to tip, here’s what I’d do... get some aluminum fincan band brackets from Hawk Mountain or Binder Design and then make your own fins for it. Preferably aluminum, but if not use carbon plate. Then I’d screw it together and use epoxy to put heavy fillets over the entire bracket assembly. If the fins themselves are your own, I think it would pass the “no prefab fincans” L3 rules, but it’ll depend on your TAP. My 98 MD flight was an epoxy potted Hawk fincan with modified aluminum fins.

Todd

 

[airforcetp1991]

Beaker & Havoc got there after 2013. I think Sumo got there after you left too. Yeah, just farting around in the Viper in that photo (from a while ago...with an awesome Lockheed photog in the trunk). I'm sure I know some people out at HMN, but I'm not very good at keeping up with where everyone is now that I'm retired. (Everyone I know would be an "old guy.") Have fun out there!

Thanks, I’ll ask around the SIM IPs, some of them have been here a while haha. CP!

HASH

 

[GrouchoDuke]

Thanks, I’ll ask around the SIM IPs, some of them have been here a while haha. CP!

Ha!

 

[airforcetp1991]

I didn’t need ballast or have any stability issues. The CG was already pretty far forward since it was all motor with heavy forward bulkhead.

As for your fins, I don’t think they’ll work. Unreinforced 3/16” is going to buzz right off. If you absolutely can’t do tip to tip, here’s what I’d do... get some aluminum fincan band brackets from Hawk Mountain or Binder Design and then make your own fins for it. Preferably aluminum, but if not use carbon plate. Then I’d screw it together and use epoxy to put heavy fillets over the entire bracket assembly. If the fins themselves are your own, I think it would pass the “no prefab fincans” L3 rules, but it’ll depend on your TAP. My 98 MD flight was an epoxy potted Hawk fincan with modified aluminum fins.

Todd

I have looked at lot at the Dragon Plate high temp plate but was concerned about delamination. Have you seen people use that in the past?

Tony

 

[plugger]

Very true, the nosecone length/ratio does make a difference in the SIM. To be honest the 6:1 is also the highest fineness ratio I could find available and without the tools or knowledge to make it myself I figured that was the best choice.

Apparently Curtis/PR makes a FW VK NC in 4" that's 7:1. They're very hard to find though.

What do you think of the choice of G10 for the fins, that was based on heat resistance and delamination concerns? My other thought was dragon plate.

Definitely don't go with the G10. I've been meaning to start a new thread on the NC and AV Bay that I recovered when my 3" M2245 MD rocket re-kitted itself at nearly Mach 3. The base of the AV Bay was a G10 bulkhead and it cleanly delaminated up to the 'mid line' of the bulkhead where I had threaded rods and Epiglue holding them in place. I expect at Mach 3.5 you'd have a heck of a time keeping those in one piece and even if they did hold I expect they'd be significantly damaged which would impact your apogee considerably.

Use the Dragon Plate. Also, t2t isn't really a requirement with your flight envelope imo as long as your fin thickness is adequate along with your fillets, especially given your trailing edge is swept forward. I've found t2t is really only necessary to keep fins on when the rocket lands, especially if you're impacting on a single fin off angle. Your forward swept trailing edge mitigates that risk considerably.

 

[OverTheTop]

What do you think of the choice of G10 for the fins, that was based on heat resistance and delamination concerns? My other thought was dragon plate.

CF plate will be lighter and stiffer. You might be able to get the same stiffness with thinner plate if using CF. That will make the fins have less frontal drag.

FYI I used some G10 for core with CF plate on the outer of some fins for my O-M project. M2.14 only, but it held up to the flight stresses. You will be going a bit harder than that so I don't know if my fin method would work for your situation. See here for what I did:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=42See some of the earlier posts here for the rationale for using the isogrid and an earlier attempt at this. I did place a layer of fiberglass over the leading edges and laminated them in place with JB Weld. I was concerned about forward facing laminated structure delaminating.

 

[airforcetp1991]

Apparently Curtis/PR makes a FW VK NC in 4" that's 7:1. They're very hard to find though.


Definitely don't go with the G10. I've been meaning to start a new thread on the NC and AV Bay that I recovered when my 3" M2245 MD rocket re-kitted itself at nearly Mach 3. The base of the AV Bay was a G10 bulkhead and it cleanly delaminated up to the 'mid line' of the bulkhead where I had threaded rods and Epiglue holding them in place. I expect at Mach 3.5 you'd have a heck of a time keeping those in one piece and even if they did hold I expect they'd be significantly damaged which would impact your apogee considerably.

Use the Dragon Plate. Also, t2t isn't really a requirement with your flight envelope imo as long as your fin thickness is adequate along with your fillets, especially given your trailing edge is swept forward. I've found t2t is really only necessary to keep fins on when the rocket lands, especially if you're impacting on a single fin off angle. Your forward swept trailing edge mitigates that risk considerably.

That makes sense given the span of the fin as well. Hopefully Dragon Plate can cut them at a per area rate, that 12x24 sheet ain’t cheap haha Based on their options I think the 0.2” is what I would pick, yes it’s thicker but I wouldn't want to go all the down to 0.125”.

 

[THarrison]

I have looked at lot at the Dragon Plate high temp plate but was concerned about delamination. Have you seen people use that in the past?

Tony

I've seen a lot of people use carbon plate without issue, but I'm not sure which ones sourced from Dragon. They're pretty expensive and Wildman/Composite Warehouse may be better sources for raw carbon plate. I don't think I've ever seen commercially manufactured G10/Carbon plate itself delaminate. The delamination is usually the tip to tip layup applied by the flyer peeling away from the leading edge when the airflow gets under a tiny gap in the layup. I have seen the plate char and slightly erode the leading edge, but it maintains it's structural integrity and doesn't fan out the layers. Just my observations, somebody may have a different experience.

Todd

 

[airforcetp1991]

CF plate will be lighter and stiffer. You might be able to get the same stiffness with thinner plate if using CF. That will make the fins have less frontal drag.

FYI I used some G10 for core with CF plate on the outer of some fins for my O-M project. M2.14 only, but it held up to the flight stresses. You will be going a bit harder than that so I don't know if my fin method would work for your situation. See here for what I did:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=42See some of the earlier posts here for the rationale for using the isogrid and an earlier attempt at this. I did place a layer of fiberglass over the leading edges and laminated them in place with JB Weld. I was concerned about forward facing laminated structure delaminating.

I’m sorry to see that the recovery didn’t work out for the nike Project but was an incredible build! I like the idea of a fiberglass or phenolic leading edge but I would also prefer the fins be as simple as possible and I would hate to have one leading edge fly off and cause a stability issue.

Tony

 

[OverTheTop]

I’m sorry to see that the recovery didn’t work out for the nike Project but was an incredible build!

Thanks. Loss of telemetry at 37k' doesn't help with recovery. The good news is that the fins held up .

 

[airforcetp1991]

Thanks. Loss of telemetry at 37k' doesn't help with recovery. The good news is that the fins held up .

My first L2 attempt is core sampled somewhere in the NM desert… Certainly not of the same scale as the Nike but I know that feeling.

 

[DAllen]

over here......

Show me you know what your talking about and let's do it. Why should we all say no to the OP simply because we will never do it or it has not been done ?

Um...You're taking my post a bit out of context. I wasn't saying "no" to the OP...I was making light of the idea of building this project with 5 minute epoxy - in one day.

 

[dhbarr]

Um...You're taking my post a bit out of context. I wasn't saying "no" to the OP...I was making light of the idea of building this project with 5 minute epoxy - in one day.

15min epoxy over two days, sorted!

 

[RalPh8]

To the OP. First if you are going to stress the airframe on a smaller M class motor, it will never handle an "O".
Second, on a MD build you can slot the airframe the size of the root of the fins and inset them into the slot. I also like to drill holes through the fins to act as " fingers " in the fillet.

That fingers idea is genius. This is why I read these posts. Always learning.

 

[David Schwantz]

It just came to me while I was driving through downtown Atlanta at 8am

 

[airforcetp1991]

It just came to me while I was driving through downtown Atlanta at 8am

Do you have an images of how/where you drilled the fingers that you'd be willing to share?

-Tony

 

[David Schwantz]

Yuppers.

 

[airforcetp1991]

Yuppers.

Awesome, thank you! Did you plug the holes halfway through the thickness while doing the fillets or just tape over the bottom and let the holes fill up and then sand the "bottom" side of the fin before the fillet on the opposite side? That may have been worded poorly but I hope it makes sense. Thanks again.

Tony

 

[David Schwantz]

Drill holes, sand with 36 grit, tack in place with CA, add fillet. I also like to spooge a little glue in the holes with pop stick or my finger as I am doing final fillet. It will normally come out the other side of the holes as you go. When glue will no longer run, drip or sag, flip over and do other side so that you will still get chemical bond with the previously done fingers.

 

[David Schwantz]

PS, sand tube also before tacking with CA.