L3 Carbon Min Diameter Build

[airforcetp1991]

I am planning on starting this build some time next year and after researching some other very aggressive L3 builds (N5800 types) I am planning on a inside the nosecone style AvBay. This is my first concept and I am hoping those who have built these types of projects in the past can give some feedback and wisdom to help me along. Concept is to use the charge cannons to deploy the drogue at apogee then use 2x Piranha cable cutters to release the main chute which will be in a deployment bag.

Parts:
- 1x4" Aluminum bulk plate and 1x3" Aluminum bulk plate
- 2xMissile Works 3D printed sleds
- 2xMMissile Works RRC3 altimeters mounted with #8 all thread
- 1xFeatherweight GPS in a Lab rat rocketry 3D printed sled
- 1x1/4 center Rod
- 2x Piranha Cable Cutters

-Tony

 

[watheyak]

Looks cool!

I've done quite a few av-bays in a nosecone. One thing you may have to be careful with is where you put your static ports/baro sampling holes.

I don't know anything about the RRC3s other than that they're baro-only. If your sampling ports are angled into the relative wind, there will be an increase in pressure as the rocket accelerates and that could cause issues with what the RRC3s assume is happening with the rocket.

Like I said, I have zero experience with the RRC3s, and they might be fine in this situation, but I'd check with Missileworks first. In cases like this I use a Featherweight Raven, which are immune to issues like that.

Edit: looking closer at you pictures, if you just put the holes at the base of the nosecone where it is tangent to the airframe tube, you should be good, regardless of the altimeter.

 

[airforcetp1991]

Looks cool!

I've done quite a few av-bays in a nosecone. One thing you may have to be careful with is where you put your static ports/baro sampling holes.

I don't know anything about the RRC3s other than that they're baro-only. If your sampling ports are angled into the relative wind, there will be an increase in pressure as the rocket accelerates and that could cause issues with what the RRC3s assume is happening with the rocket.

Like I said, I have zero experience with the RRC3s, and they might be fine in this situation, but I'd check with Missileworks first. In cases like this I use a Featherweight Raven, which are immune to issues like that.

Edit: looking closer at you pictures, if you just put the holes at the base of the nosecone where it is tangent to the airframe tube, you should be good, regardless of the altimeter.

That’s a great point and I have been thinking about that a lot. Ravens are more expensive but when you are talking about several hundred dollars for a reload it is probably a good investment.

On a similar note have you ever experienced issues with avionics heating in the nose cone due to the high speed airflow? Similar setups have pushed Mach 3 from what I’ve read but I don’t know if/how they mitigated that issue.

 

[watheyak]

Heat isn't an issue on the inside. You're only making heat for a couple seconds. The paint, on the other hand, won't survive.

But chicks dig Mach rash...

But seriously, sitting on the pad in the sun will get the electronics hotter than the flight is. Plus, it's like -65 celsius at the altitude this would likely hit.

 

[OverTheTop]

The metal allthread will likely cause you some lost telemetry range (detune antenna and absorb some signal). Not sure what altitude you are going for and whether it will actually matter. Can you get your Tx antenna somewhat away from the metal? My assumption is that it is a fiberglass nosecone, as carbon fiber would not allow much through in the way of RF signal.

 

[Conway Stevens]

The metal allthread will likely cause you some lost telemetry range (detune antenna and absorb some signal). Not sure what altitude you are going for and whether it will actually matter. Can you get your Tx antenna somewhat away from the metal? My assumption is that it is a fiberglass nosecone, as carbon fiber would not allow much through in the way of RF signal.

I've been told by several... Cris from Eggfinder, Adrian with featherweight and Bdale from Altus that the metal all thread will cause absolutely zero loss just being near the tracker. If its inside of metal , encased in metal or carbon fiber then yes there would be loss. But not just having metal components near them.

 

[OverTheTop]

I've been told by several... Cris from Eggfinder, Adrian with featherweight and Bdale from Altus that the metal all thread will cause absolutely zero loss just being near the tracker. If its inside of metal , encased in metal or carbon fiber then yes there would be loss. But not just having metal components near them.

Interesting. Make sure you do ground testing to prove your range. A large piece of metal in the near field of an antenna must have some effect. I should test it with my VNA sometime. Call me skeptical .

 

[Conway Stevens]

Interesting. Make sure you do ground testing to prove your range. A large piece of metal in the near field of an antenna must have some effect. I should test it with my VNA sometime. Call me skeptical .

I myself have the RTx from Missleworks, the Eggfinder TX, and the featherweight tracker. Have tested all 3 and no changes with metal screws, eyebolts , all thread, battery cases, wires, or any other metal components near by. I have seen a substantial loss inside a carbon airframe. This is why I always use fwfg nose cones to utilize for holding my trackers. Just my own personal experience after talking with different manufacturers.

 

[airforcetp1991]

I myself have the RTx from Missleworks, the Eggfinder TX, and the featherweight tracker. Have tested all 3 and no changes with metal screws, eyebolts , all thread, battery cases, wires, or any other metal components near by. I have seen a substantial loss inside a carbon airframe. This is why I always use fwfg nose cones to utilize for holding my trackers. Just my own personal experience after talking with different manufacturers.

I am working on another design option that would coincidentally move the antenna further away. Basically I felt like I could be more space and therefore weight efficient. This includes 2 Raven4's on power perches and the FeatherWeight. Yes it is a fiberglass nosecone.

RockSim says about 37,000 feet with the current design and just shy of Mach 3.5 but I know that it isnt very accurate at those Mach numbers though... The final weight will also vary as I work out the fin design and attachment.

 

[watheyak]

On a similar rocket, Openrocket and RASAero we're about double the Rocksim in altitude.

They're both free. Doesn't hurt to use all availae resources. RASAero's results are especially valuable on a flight like this.