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mpitfield

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I am just starting to think about a design for a rocket that requires HED. That is Head End Deployment for those who have not read about it. I know CJ has done a lot of work on this and I have seen other posts over the last few years. So please share pics, links, thoughts, advice on this AV bay and deployment design. My current need is more of a 4" test platform for to get some experience for at least two other planned builds that are going to be progressively more serious and important to my longer term goals.

I am looking forward to reading your posts...thanks for contributing!
 
Attebery Performance engineering makes a few different HED altimeter bays for various size nose cones. https://www.ape-rc.com/#!/Rocketry/c/11909535/offset=8&sort=normal
Thanks, I have looked at those in the past but they will not work for my rocket needs.

What I have in mind for the first one is what I would describe as a hybrid doughnut design. Essentially a nosecone coupler that is the AV Bay with the bottom half of the Bay as a doughnut design. This is required to allow clearance for the top of the motor and the attachment point for the recovery harness. This would be pinned to the airframe with sheer pins and the nosecone would be pinned to the AV Bay as well.

This first one is a 4" rocket that uses a stock FW/FG 5:1 ogive nosecone, and stock tubing. It is not a MD rocket so there are less design constraints than the next two. It is a stock kit that uses a 54mm motor and is being retroactively fitted. This will be my first HED that I hope to progressively refine as I move towards the final rocket. It will use dual altimeters with dual charge wells and contain a tracker.

The other two rockets will be designed for HED, so there won't be a need for the doughnut part. However these two will be a bit more challenging. This is because they are both true MD rockets where the OD is 54mm on one and 98mm on the other. Because of this both require custom tubes couplers and nosecones.

The final one will use dual altimeters with primary Raptor CO2 canisters and backup high alt charge wells. The tracker, Kate will be packed at the very top of the nosecone.

For now I need to focus on a good initial design for the first rocket.
 
One of these wouldn't be the Black Fly would it?

I could offer suggestions and ask questions but you are more knowledgeable than I on HED as it is so my paltry 2 cents wouldn't add up to much. LOL

Heck, I'm jumping in anyway:
So your laundry will go in the nose. Then you will pin the coupler-turned-a/v bay to the nosecone, then pin that to the airframe. So where will it separate first? The coupler will remain pinned to the airframe and the nosecone will pop deploying a JLCR bundle? Or the nosecone with coupler detaches in a drogueless type setup? Then the nosecone blows the coupler and releases the main?

I've only used one FWFG nosecone so not a lot of experience with those. But you could get a longer coupler to add more room if needed for electronics and batteries, they would go down along by the motor. What altimeters will you be using? I'm thinking Quarks would be space saving, but you may use Ravens or something else outta my price range...I see you got Kate in there after all. Or will she only be in the final rocket? I don't see how you will get her in the nose with the laundry. Looks like the tube just to tuck her in will occupy most of the real estate up there.
 
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I can help with the 54mm & 98mm minimums, need a bit more detail.
Whats going where, obviously you aren't putting Kate in the 54...are you?
 
One of these wouldn't be the Black Fly would it?

I could offer suggestions and ask questions but you are more knowledgeable than I on HED as it is so my paltry 2 cents wouldn't add up to much. LOL

Heck, I'm jumping in anyway:
So your laundry will go in the nose. Then you will pin the coupler-turned-a/v bay to the nosecone, then pin that to the airframe. So where will it separate first? The coupler will remain pinned to the airframe and the nosecone will pop deploying a JLCR bundle? Or the nosecone with coupler detaches in a drogueless type setup? Then the nosecone blows the coupler and releases the main?

I've only used one FWFG nosecone so not a lot of experience with those. But you could get a longer coupler to add more room if needed for electronics and batteries, they would go down along by the motor. What altimeters will you be using? I'm thinking Quarks would be space saving, but you may use Ravens or something else outta my price range...I see you got Kate in there after all. Or will she only be in the final rocket? I don't see how you will get her in the nose with the laundry. Looks like the tube just to tuck her in will occupy most of the real estate up there.

Yes as a matter of fact I am turning my 4" BlackFly into HED. I have no experience with HED so don't think you can't contribute. My main reason for doing this is that I have two different rockets that require HED and they are important flights for me. I have always approached rocketry this way where I practice with configurations, technologies and building techniques in rockets that do not require this. I do this so I can gain hands on experience for rockets where it is needed, just my thing.

See below for the description of my constraints and ideas for setting up the 4" BlackFly

I can help with the 54mm & 98mm minimums, need a bit more detail.
Whats going where, obviously you aren't putting Kate in the 54...are you?

Unfortunately no Kate will not fit in the 54mm nosecone, if it did I would use it but right now it is only my intention of using it on the 98mm MD nosecone out of these three builds. Also before I get into the two other HED projects, I want to get some hands on with the 4" with the 54mm MMT.

So focusing on the 4" HED with the 54mm MMT, here are the specs.

- 4" airframe
- 16.75" Ogive nosecone
- 7" nosecone coupler (AV Bay)
- nosecone tip and nose-weight takes up the first 4.5"
- AV bay inserts comfortably 3.25" into nosecone
- components to fit into the AV Bay will be Eggfinder mini (tracker), Eggtimer Quark (Backup), TeleMini (Primary), 3 screw switches, 3 Li-Pos

Because I would like the option of launching with the Loki 54-2800 hardware this means that the motor will extend into the AV bay roughly 4". Again this is because this is not a rocket designed for HED its a retro. Because of this I am looking at doing a doughnut AV bay with an internal 54mm MMT that extends up to the top bulkhead which covers it.

My thought was that I would glue a thin CR in the nosecone as a stop, to prevent the AV bay from moving forward and getting too snug as well as keep the load off the sheer pins. The top of this CR would be rounded to prevent anything from catching on it. I would pin both the AV bay/nosecone coupler using 3-256 nylon pins in the nosecone and airframe.

To pack the laundry I was thinking of using the integrated anchor in the top CR of the MMT to connect my recovery gear to and have it connect to a short Y coming off the bottom CR of the AV bay. I would pack a small 15" drogue just below the bottom CR which would be connected to a 3' 3rd loop coming off my recovery harness. I am not sure which main I will use but the rocket should be about 8lbs coming down so I may use an Iris Ultra Compact in a deployment bag with a 12" pilot. I will have to talk to Gene to see what size bag I could use but I am thinking a 3" x 5" might work well for that chute. If he agrees then it will have to be custom. I would pack the recovery harness up in the top, then the chute then the pilot.
 
So focusing on the 4" HED with the 54mm MMT, here are the specs.

- 4" airframe
- 16.75" Ogive nosecone
- 7" nosecone coupler (AV Bay)
- nosecone tip and nose-weight takes up the first 4.5"
- AV bay inserts comfortably 3.25" into nosecone
- components to fit into the AV Bay will be Eggfinder mini (tracker), Eggtimer Quark (Backup), TeleMini (Primary), 3 screw switches, 3 Li-Pos

this means that the motor will extend into the AV bay roughly 4". Because of this I am looking at doing a doughnut AV bay with an internal 54mm MMT that extends up to the top bulkhead which covers it.

No need for "doughnut", I have a way around this. Another type of doughnut...lol Longer coupler , but the side facing motor will have nothing in it for first 4 inches [or what ever is determined] side going into cone will be empty also for 3.25 in. Gives you a tone of room to work with now.

My thought was that I would glue a thin CR in the nosecone as a stop, to prevent the AV bay from moving forward .

Vent band on coupler will serve this purpose.


To pack the laundry I was thinking of using the integrated anchor in the top CR of the MMT to connect my recovery gear to and have it connect to a short Y coming off the bottom CR of the AV bay. I would pack a small 15" drogue just below the bottom CR which would be connected to a 3' 3rd loop coming off my recovery harness. I am not sure which main I will use but the rocket should be about 8lbs coming down so I may use an Iris Ultra Compact in a deployment bag with a 12" pilot. I will have to talk to Gene to see what size bag I could use but I am thinking a 3" x 5" might work well for that chute. If he agrees then it will have to be custom. I would pack the recovery harness up in the top, then the chute then the pilot.

Plenty of room for that, if done like mine.


This is 11inch coupler.....both ends open & av-bay in the middle where long vent band is.

20160809_113230.jpg

Careful inspection will show BP against the coupler "shelf" inside. There is 5 inches of room between my BP's for electronics. Both sets of av-bay lids go against the shelf..completely inside.

20160809_113156.jpg

Here is other side. You will have plenty of room for motor on one side and recovery gear on other. Use as long a coupler as needed & vent band sized accordingly.

20160809_113221.jpg

whole thing neatly inside this.

20160809_172440.jpg DSCN0830.jpg

My drawing skills aren't the greatest ...but you get the idea. Should you wish to pursue this solution I will gladly help out with more details & pics.

I would recommend a simpler version for your first go at this & do a couple of deployments.
However if you feel comfortable at this high skill level...go for it.
I can show how to move a GPS into nose tip also.
 
This is 11inch coupler.....both ends open & av-bay in the middle where long vent band is.

View attachment 339109

Careful inspection will show BP against the coupler "shelf" inside. There is 5 inches of room between my BP's for electronics. Both sets of av-bay lids go against the shelf..completely inside.

View attachment 339110

Here is other side. You will have plenty of room for motor on one side and recovery gear on other. Use as long a coupler as needed & vent band sized accordingly.

View attachment 339111

whole thing neatly inside this.

View attachment 339112 View attachment 339113

My drawing skills aren't the greatest ...but you get the idea. Should you wish to pursue this solution I will gladly help out with more details & pics.

I would recommend a simpler version for your first go at this & do a couple of deployments.
However if you feel comfortable at this high skill level...go for it.
I can show how to move a GPS into nose tip also.

That is great feedback. I can see a few things that I will do differently immediately. I was going to avoid a vent band but you just reminded me why I should be using one. The use of the band will also eliminate the need for that nosecone CR I was thinking of using. Also I was going to use the larger Missile works screw switches with the PCB board but your pics also reminded me that I have a bunch of the FingerTech mini screw switches in my stock.

To clarify you have a single attachment point for the recovery harness and both sides of the AV bay are recessed with a short 4" AV Bay in the middle? I am not sure how much if any I can recess the top of my AV bay but I will have a look.

As far as putting the tracker in the nosecone tip I would like to hear more about your ideas?

In regards to simplifying this further I am open to the discussion but dual electronic AV Bays is something I have done so it does not intimidate me. Keep in mind I have been working with, or I should say hacking, electronics since I was about 10. I am no where near proficient but I am slowly collecting a decent set of tools which I find makes all the difference between doing it poorly ad doing it well. Plus a bit of skill can't hurt. Beyond that I am not sure what else can be done to simplify HED ver1 for me but I am open to a discussion.

Thanks.
 
I recessed the aft bulk plate in my Bigger Daddy bay, but the forward bulk plate is flush.

I used forged eye bolts for both recovery points and to hold together the bay. A small screw in the forward bulk plate interferes with the eyebolt being able to back out if torqued during descent.

I am still not sure about how to set up my drogue/main. If I want to use motor ejection as backup for the drogue then it goes in the body tube with the main in the nose. Otherwise I could go with the main on the body.

IMG_3930.jpg

3545BDB3-BE2D-470A-A074-860E0C2FE4A9.jpg

IMG_3970.jpg
 
Here is link to GPS bay in tip.

https://www.rocketryforum.com/showt...2-stage-sounding-rocket&p=1605121#post1605121

Read that & posts # 67 & 79

Shows black ring in NC first post [#62] that where GPS bay is. Ring glued in & tiny bay with Eyebolt for recovery screw into that. We ditched the carbon & remade coupler [double wall thickness] out of glass. But you can see in pic how much room was gained. It's open all way to bottom of cone, you can see coupler through it.

We had a 36in Fruity chute with 15 ft or more 1/4 in Kevlar shock cord, wrapped in a 12in. kevlar chute protector.
Plenty of room left over.
This was a 3in diameter rocket. you will have what seems like a cave in yours. The av-bay was 5in. interior.
Yes there was a eyebolt on both lids , just like normal bay. #10 threaded rod [3/16]

I'm sure with proper planning you can get everything needed in place. We made a Phenolic tip. [description in post]
& as you can see I just put antennas on outside of bay with chute wrapped in protector between both antennas.

We also did something very similar on the 3/4 scale Nike Smoke. Made a "pancake" bay only 4in wide, slid into payload...bolted into place right in middle. There was no other way this simple.
 
I recessed the aft bulk plate in my Bigger Daddy bay, but the forward bulk plate is flush.

I used forged eye bolts for both recovery points and to hold together the bay. A small screw in the forward bulk plate interferes with the eyebolt being able to back out if torqued during descent.

I am still not sure about how to set up my drogue/main. If I want to use motor ejection as backup for the drogue then it goes in the body tube with the main in the nose. Otherwise I could go with the main on the body.

View attachment 339114

View attachment 339115

View attachment 339116

Wow more pics and feedback. I like the custom formed removable lead weight, how did you create this? I have always been a bit concerned about melting lead due to fumes. I have a 25lb bag of #4 lead shot and conservatively mix it up in a batch of epoxy and pour. While it packs relatively densely, it is obviously not as dense as melted and cast lead, plus the idea of being able to remove it and have a couple/few different weights is appealing.

I see the concern over the eye bolt and it is something I had not considered as I usually use threaded rods and lock the eye bolts onto the bulkheads using two nuts on the backside to lock it, plus red loctite, plus I grind the backside so the thread is slightly fouled. Put it this way I will never have a failure based on an eye bolt coming lose.

Personally I would be inclined to go with motor back up, if the delay permits it, use the drogue in the body and keep the main in the nosecone. My intuition and observations from other flights leads me to I believe that things will be neater and more controlled on deployment with this config vs. the other.

Thanks for sharing.
 
Here is link to GPS bay in tip.

https://www.rocketryforum.com/showt...2-stage-sounding-rocket&p=1605121#post1605121

Read that & posts # 67 & 79

Shows black ring in NC first post [#62] that where GPS bay is. Ring glued in & tiny bay with Eyebolt for recovery screw into that. We ditched the carbon & remade coupler [double wall thickness] out of glass. But you can see in pic how much room was gained. It's open all way to bottom of cone, you can see coupler through it.

We had a 36in Fruity chute with 15 ft or more 1/4 in Kevlar shock cord, wrapped in a 12in. kevlar chute protector.
Plenty of room left over.
This was a 3in diameter rocket. you will have what seems like a cave in yours. The av-bay was 5in. interior.
Yes there was a eyebolt on both lids , just like normal bay. #10 threaded rod [3/16]

I'm sure with proper planning you can get everything needed in place. We made a Phenolic tip. [description in post]
& as you can see I just put antennas on outside of bay with chute wrapped in protector between both antennas.

We also did something very similar on the 3/4 scale Nike Smoke. Made a "pancake" bay only 4in wide, slid into payload...bolted into place right in middle. There was no other way this simple.

Thanks for the info, I will read the post. BTW speaking of phenolic tip, I have not seen Charles from Carolina for a while, is he still doing his rocketry things?
 
For the weights I started by sticking the plastic wrapped nosecone into a container of plaster of Paris.

IMG_3960.jpg

IMG_3962.jpg

I melted a bunch of old dental x-ray film shields in a stainless pot. I did this outside and avoided getting too close.

IMG_3964.jpg

IMG_3967.jpg
 
Thanks for the info, I will read the post. BTW speaking of phenolic tip, I have not seen Charles from Carolina for a while, is he still doing his rocketry things?

Yes he is , we talk almost daily. Finishing up a batch of 50+ Head End Ignition modules for sustainer ignition. Finished my printed I/S for Nike Apache today, among the tons of custom carbon stuff he's making for various teams [SLI] Just had another baby right before Xmas....he's a busy guy lately.
 
Yes he is , we talk almost daily. Finishing up a batch of 50+ Head End Ignition modules for sustainer ignition. Finished my printed I/S for Nike Apache today, among the tons of custom carbon stuff he's making for various teams [SLI] Just had another baby right before Xmas....he's a busy guy lately.

Did he change his site, the old one has been off-line for a while and his FB page seems inactive. Can you let him know I am looking to talk to him about finishing a small part for an 8" project he was working on but waiting for me to get him some measurements. I also have two unrelated larger projects in the works that I need his expertise and talents on.
 
I could've swore you and I had a conversation about HED before, for my Tembo, that I never finished. LOL

Looks like Jim's method would be the simplest to do, however it does stretch the rocket a bit. That may matter to you or not. I started doing something similar on my Wildman Sport, just never got past "started".

So you plan to have a drogue inside the air frame...right up against the motor casing? Well I suppose you will have a protector of some sort so surely it won't melt.

Just from upscaling my Black Fly sim file, it looks like you will have around 12" from the top of motor casing to tip of nose cone. How much space does the EF Mini require? Will it fit crossways in the coupler? As in is it less than 4" long? If so you may can do a two or three layer type pancake bay.

I got ideas bouncing around that I am gonna work up in CAD to see if it's practical but if you are gonna stretch it a bit anyway then a pancake wont be necessary.
 
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Crude CAD of a pancake bay similar to what I have in my (unfinished) Tembo. I don't really know the dimensions of the Telemini or the EF Mini but here is an idea of how you could do it. Wiring may be a nightmare but it can be done.

total.jpg
Blue cylinder is the Loki motor.
Orange CR on bottom holds two charge wells and an attachment point.
Next forward is a bulkhead set 1/4" above the motor. It holds 3 LiPo batteries.
Next is a bulkplate that holds the Quark and Telemini, the green blocks. A notch is cut in this BP allowing the EFmini to pass through. The long purple block is the EFmini setting on sled, the teal piece. The other teal piece between the altimeters is just a support for the EFMini. Probably not necessary depending on how you mount the EFMini.
Top plate holds two charge wells and a penetration for the EFMini antenna, which can be protected using a small tube.

BAy.jpg
Another view. The bottom ring and top plate should probably be stepped just like a regular lid. The blue tube is a piece of MMT glued to the CR and capped to seal the bay. It could actually be glued to the green plate holding the batteries.

Eggtimer board.jpg
The electronics payload.
Like I say, don't have details on Telemini.

LiPo Board.jpg
The batteries.
The batteries I used for a measurement are some I got off Amazon. 300 MAH, 2S LiPo.

Another option to be to mount the batteries to the green plate or the bottom CR, but radially around the motor. They may get a bit hot doing it that way though.
The screw switches could be mounted anywhere in the switch band.
The green and red plates don't need to seal anything so they can be drilled, notched, or whatever to allow cable routing and, in the case of the green plate, to assist in mounting the screw switches.
Of course you will have to place your all thread or whatever you use. But that shouldn't be too difficult either.
I have standoffs separating my plates and all thread holding it all together. Assembly takes some time but that is just the nature of the beast.
You could always forego the all thread and use rod couplers epoxied or fiberglassed to the inside of the coupler.

Yes I know the drawings are pretty crude and the nose cone isn't an ogive, but maybe it will help give you some ideas.
 
I could've swore you and I had a conversation about HED before, for my Tembo, that I never finished. LOL

Looks like Jim's method would be the simplest to do, however it does stretch the rocket a bit. That may matter to you or not. I started doing something similar on my Wildman Sport, just never got past "started".

So you plan to have a drogue inside the air frame...right up against the motor casing? Well I suppose you will have a protector of some sort so surely it won't melt.

Just from upscaling my Black Fly sim file, it looks like you will have around 12" from the top of motor casing to tip of nose cone. How much space does the EF Mini require? Will it fit crossways in the coupler? As in is it less than 4" long? If so you may can do a two or three layer type pancake bay.

I got ideas bouncing around that I am gonna work up in CAD to see if it's practical but if you are gonna stretch it a bit anyway then not a pancake wont be necessary.

Probably not HED but a nosecone AV bay, I have done that one plenty of times and in some very usual configurations, such as CO2 and ARRD, with cable cutters and experimental deployment bags, custom CF shrouds for chutes, etc. This will be my first official HED although I have read about it roughly over the last 3 years which is when it seems to have become a bit more main-stream. Actually I think the first one I saw was the 3" Punisher, which I have but I have not built yet, so that will be a HED as well. Now that I think about it I likely have an easy half dozen kits and builds that will end up HED that I have in the works now.

I ordered a .5" vent hole AV Bay band, which is hopefully plenty big enough for the sampling holes and will also double as access holes for the screw switches, that is if everything lines up. I may cut the half inch off the existing BT just to keep it proportional or leave it, that I can decide on the fly, no pun intended.

Yes I also thought of a melting drogue, but I am pretty sure it will be fine in all wrapped up in a Nomex blankie. Worst case it comes down semi-drogueless so I will find out one way or the other.

The EF mini is pretty small, one of the smallest I have used with the antenna, I will measure it up on the weekend. Sadly as good as I am with technology and computers, drawing with 3D CAD is not a skill I possess. I am more of a hold it in my hand try it out, visualize it "builder" vs. design it in 3D CAD. So where and how the tracker or any of it gets mounted is still undecided. I did like Jim's idea of a nosecone tracker and I really like the one Charles designed with the TeleGPS antenna in the phenolic tip although I am not sure I read any feedback on it's performance which I think was to 27K. however that will not work for this build so perhaps something below the nose weight. Also rfjustin and RocketFeller both had some inspirational ideas in their designs so it will likely end up a bit of everything.

As Jim said once I start trying things out in the nosecone section it will probably end up pretty roomy.

BTW I posted an accurate Open Rocket 4" BlackFly file, with the Wildman nose not the poly nosecone, on Chris' 4" BlackFly build thread here https://www.rocketryforum.com/showt...-Black-Fly-Build-Thread&p=1766515#post1766515
 
Crude CAD of a pancake bay similar to what I have in my (unfinished) Tembo. I don't really know the dimensions of the Telemini or the EF Mini but here is an idea of how you could do it. Wiring may be a nightmare but it can be done.

View attachment 339283
Blue cylinder is the Loki motor.
Orange CR on bottom holds two charge wells and an attachment point.
Next forward is a bulkhead set 1/4" above the motor. It holds 3 LiPo batteries.
Next is a bulkplate that holds the Quark and Telemini, the green blocks. A notch is cut in this BP allowing the EFmini to pass through. The long purple block is the EFmini setting on sled, the teal piece. The other teal piece between the altimeters is just a support for the EFMini. Probably not necessary depending on how you mount the EFMini.
Top plate holds two charge wells and a penetration for the EFMini antenna, which can be protected using a small tube.

View attachment 339291
Another view. The bottom ring and top plate should probably be stepped just like a regular lid. The blue tube is a piece of MMT glued to the CR and capped to seal the bay. It could actually be glued to the green plate holding the batteries.

View attachment 339285
The electronics payload.
Like I say, don't have details on Telemini.

View attachment 339284
The batteries.
The batteries I used for a measurement are some I got off Amazon. 300 MAH, 2S LiPo.

Another option to be to mount the batteries to the green plate or the bottom CR, but radially around the motor. They may get a bit hot doing it that way though.
The screw switches could be mounted anywhere in the switch band.
The green and red plates don't need to seal anything so they can be drilled, notched, or whatever to allow cable routing and, in the case of the green plate, to assist in mounting the screw switches.
Of course you will have to place your all thread or whatever you use. But that shouldn't be too difficult either.
I have standoffs separating my plates and all thread holding it all together. Assembly takes some time but that is just the nature of the beast.
You could always forego the all thread and use rod couplers epoxied or fiberglassed to the inside of the coupler.

Yes I know the drawings are pretty crude and the nose cone isn't an ogive, but maybe it will help give you some ideas.

Man that was fast, I just hit send and you have 3D drawings up. I will have a look at these and get back to you.
 
Crude CAD of a pancake bay similar to what I have in my (unfinished) Tembo. I don't really know the dimensions of the Telemini or the EF Mini but here is an idea of how you could do it. Wiring may be a nightmare but it can be done.

I like the idea of having the batteries pancaked between the electronics sled and the bulkhead that or a version of that will likely make it's way into the design if it all fits. One thing I am realizing after looking at both Jim and rfjustin's designs is that the doughnut part is likely unnecessary and the bay will just be recessed. This helps me with the design and for the all thread I am leaning towards a single centered thread maybe a 14/20 stainless which I have and should be plenty heavy enough. The drogue side I would secure the eye-nut so it was permanently on that side, which is the side that would come lose on decent. The main side I would use a washer against the bulkhead with a nut and the eye-nut locked in and I might even add a drop of blue loctite. Realistically it would not e subjected to the same dynamic loads as the drogue side considering it would only be in play at roughly 800' AGL.

The TeleMini's LiPo is small, here are the ones I use https://csrocketry.com/electronics/altus-metrum/400-mah-battery.html The Li-Pos I use for the Eggtimer Quark are 2S but they are also small, one of the smallest 2S Li-Pos I could find but they still have good run-time but more importantly they are 20C rated.

One thing I am not sure about, which is what Jim's post showed is how well the antenna will hold up to the BP charge. Also I could have sworn I read something where he or someone else ripped an antenna off in the recovery harness with that bulkhead mounting style. I think mounting it just below the nosecone weight, is my best plan if it fits.

BTW how is the Tembo coming along, I am sure you know that my 4" Tembo in my Avatar. I may fly that this summer but using the JLCR using the SL100 in the nosecone AV bay with a BP charge for apogee. If motor eject timing works I would use it as a backup.
 
I do like to play around with CAD before I start piecing things together and hacking up my supplies. I am getting better but still learning. I CAD stuff to get an idea and then end up getting the stuff out and test fitting it anyway. It's good practice and I can get parts cut or printed exactly (or close to it) like I want.

In my example, it is likely the antenna will only stick a short distance past the top plate. You can easily glue a small piece of fiberglass tubing to the top plate to protect the antenna and seal the penetration. My plate with the batteries is just 1/4" above the motor. If you slide your switch band up and coupler down all you will be doing is losing interior room. So while the doughnut style may not do a whole lot, it does help seal the bay. What I am trying to say is your switch band will be pretty much where it is in my example, below the lower bulkplate because that bulkplate can't go any lower, there is a Loki in the way. With no lower CR or tubing to seal the bay, those switches will be exposed to ejection gases. But I may have got a few measurements off. The alternative would be to have your switches above the bulkplate and have your sampling ports and access holes directly through the nose cone.

One all thread through the center would certainly work, you would just have to arrange things around it.

I think my LiPos are 30C, don't remember for sure.

Looks like the Telemini is a bit smaller than the Quark maybe? Should have no problem fitting them on one bulkplate. I bet my Tembo bay may can be incorporated here. I have a trashed quark I'll mess around with. If so, I can send you the files to have them cut. Nat at Upscale CNC has them on file I think.

I'll go grab your OR file and mess around with it. Sadly a Black Fly isn't in my near future. Fairly certain Ethos is hidden somewhere in the house waiting on my birthday though.

Tembos. Yeah I think we were discussing nose cone bays for those and you were using the CO2 system for yours. I wanted to do full on HED but it was kinda hard with the poly nose cone.
I can't decide on a paint scheme. I lean toward some sort of smiley, then lean toward a ripped paint/second skin kinda thing. I want to try to airbrush it, but then I want to use a wrap. I hit a snag on my nose cone bay trying to route cables or some such and haven't went back to it. Ordered a coupler and payload section to stretch it, then decided against that. LOL Think I will name it Indecision.

The nose cone bay turned out great though. A two part bay...thought I had some pictures here somewhere. Tracking up top, with a pancake style below it holding an RRC2+ and Lipo. I had designed it with recesses for support tubes and all kinds of nonsense that I will not be using now. That will be a good project tomorrow. Assemble the bay and post a picture.

The rocket is still sitting by my work desk, waiting for inspiration. I need to add some nose weight as well, about 8 ounces it looks like. I built it to fly on 54/426 motors. And it is the only one in the fleet that can use those motors. An I170G oughtta do nicely. Just writing this post is making me want to finish it. So...I need to get it finished for the spring launch. Yeah I'll do that. LOL

What I have in mind for the finish if I can get it smoothed down and over to Mark to get printed.
or rip.jpg
 
Lots of great information here. Just remember ALWAYS use a drogue of some type on HED , if not you have a good chance of it going streamlined due to the heavy nosecone. I fly one of Charlie's Meco's (carbon of course) with HED , fun little mach 2 rocket!!
 
Did a hasty assembly of my Tembo pancake bay.
Overall height is 2 1/16". Black plate is stepped to fit the shoulder of a 4" Madcow nose cone.

First the pieces.

nose bay 1.jpg

Piece 1 and 2 are the same thing. For this exercise we will use 1 since it has the weld nuts, 6-32 BTW. It goes above the nose cone shoulder. The larger holes are for 1/4" all thread.
Piece 3 is a plate that covers the hole in 1. My Eggfinder will eventually be mounted to this plate and inserted into the nose cone. The cutouts are to accommodate the 1/4" rods.
Piece 4 is the bay lid. Stepped to fit the nose cone shoulder. The two small holes on opposite sides (11 o'clock and 5 o'clock) are for mounting the charge well and running the wires through. In your case, just for charge wells since you will have two.
Piece 5 is the actually sled. The standoffs correspond to the four holes on a square pattern on piece 4. Cutouts are for the 1/4" rod. So it will slide freely.
I don't know why I used a 5/16" U-bolt. Something about the hole spacing maybe. No clue. It is way overkill for the Tembo and will be for the Black Fly as well.
You wouldn't use 1, 2, or 3.

nose bay 2.jpg

Piece 1 inserted in the nose cone and the 1/4" rods epoxied in place.

Pancake bay 1.jpg

Pieces 4 and 5 held together with aluminum threaded 2.5" 6-32 standoffs.
RRC2+ on bottom, 25-06 case trimmed for a charge well up top, as well as that big honkin U-bolt.

Pancake bay 2.jpg

My "box" for the LiPo. It has a "Kaplow" clip to hold the battery in...somewhere around here.

Pancake bay 3.jpg

Missile Works screw switch. I will have to drill through the air frame and shoulder for access but that's not a big issue. #4-40 screws tapped into the standoffs. I am probably going to replace this piece of wood with a piece of aluminum or G10.

You could easily do something similar. Do away with the LiPo box. Move the standoffs out toward the edge of the plate to give more inside room; and use longer standoffs. The cutouts will go away and you will have one hole in the center for all thread. With longer standoffs, you can actually run the altimeters up and down - parallel with the standoffs, on opposites sides. Just use standoffs a little longer than the longest altimeter. Then on another side, have your back of switches. That will free up the entire interior for your batteries. The whole package can come in under 3". Your plate #5 would be a reflection of your #4, also stepped to fit your coupler.

Or. You could use almost this exact setup, minus the big honking U-Bolt...WTF was I thinking. LOL. The LiPo box could double as a sled. LiPo on one side like shown, with the altimeter on the back side. Just like a standard sled in a standard bay...a mini sled if you will.

If you do one rod through the center, just remember your motor is gonna be right there close. Just make sure to leave enough room for it. Your bottom recovery attachment point will likely have to be off to one side. And will have to keep that in mind when placing batteries and altimeters. I'm sure you've thought of that, but a little reminder sometimes goes a long way.
 
Rod through middle is generally a waste of interior space. #6 or 8 threaded rod is more than enough & will reduce RF interference if GPS is in bay. Use a Kevlar loop instead of eyebolt for more space. [off to side of motor]
 
Careful inspection will show BP against the coupler "shelf" inside. There is 5 inches of room between my BP's for electronics. Both sets of av-bay lids go against the shelf..completely inside.

View attachment 339112 View attachment 339113

CJ:

You said the lids go completely inside, but the last photo shows the aft lid flush with the end of the coupler. Am I seeing that right?
 
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