Mobius Shroud Effect on Flight?

[jkovac]

I just balance it on my finger. With no motor, but everything else loaded and ready. I’m thinking that balancing on my finger is accurate to +/- a quarter inch. That’s close enough for me. The main point is the relation of the CG to CP, and I’ll never call it so close that a quarter inch either was makes the difference.

I might not be following what you are doing in relation to the simulation, but I don’t understand how you’re determining the physical CG of the rocket with no motor loaded.

 

[Starfire73]

I might not be following what you are doing in relation to the simulation, but I don’t understand how you’re determining the physical CG of the rocket with no motor loaded.

First, I establish the actual CG without the motor. Then in OR when I select the various motors (and virtually load them). OR knows how much the motor weighs, where the weight is placed, and how it affects the CG. It calculates the CG with different motors pretty accurately.

 

[jkovac]

First, I establish the actual CG without the motor. Then in OR when I select the various motors (and virtually load them). OR knows how much the motor weighs, where the weight is placed, and how it affects the CG. It calculates the CG with different motors pretty accurately.

Understood. What I am asking is, are you physically confirming that the CG on the fully loaded rocket is where the sim says it is? I saw that you stated this in a post above:

“The actual total weight of the rocket with the motor added was exactly what OR predicted, so I didn’t physically check the CG after determining the CG without the motor and doing the override.”

Maybe your sims are right on, but I would definitely physically check the CG in reality to confirm. You can use fishing weights and modeling clay to make a simulated propellant load if you want to check in advance of loading the motor in the field. It is also a good idea to shake the fully loaded rocket downward a few times, to make all the recovery gear shift to the bottom, which it what happens when it takes off. Then check the CG.

 

[Buckeye]

Maybe your sims are right on, but I would definitely physically check the CG in reality to confirm.

Not really necessary. This is a trivial center of gravity calculation performed by the software. The only risk is if the mass in the motor file is wildly incorrect, or the motor CG is not near the middle of the motor case length (like a long case with several adapters.) The OP is using single use motors, so this is not a problem.

 

[Starfire73]

Understood. What I am asking is, are you physically confirming that the CG on the fully loaded rocket is where the sim says it is? I saw that you stated this in a post above:

“The actual total weight of the rocket with the motor added was exactly what OR predicted, so I didn’t physically check the CG after determining the CG without the motor and doing the override.”

Maybe your sims are right on, but I would definitely physically check the CG in reality to confirm. You can use fishing weights and modeling clay to make a simulated propellant load if you want to check in advance of loading the motor in the field. It is also a good idea to shake the fully loaded rocket downward a few times, to make all the recovery gear shift to the bottom, which it what happens when it takes off. Then check the CG.

No, as a general rule I don’t double check after loading the motor; however, I have double checked a few times and the actual weight and CG (after adding the motor) have always been pretty much what was predicted. What minor variation there was, was insignificant and did not affect the predicted altitude, stability, CP, etc.

 

[jkovac]

Well if you’ve spot checked the actual CG a few times and it matched the sim in those instances, then that’s probably not the issue. But since it takes a few seconds to check the actual CG right before flight, I’d still do that. It might not be the case here, but I have seen people fixate on simulations and calculations to the point of missing something that can be easily checked in physical reality.

To get back to your initial question, I don’t think the camera/shroud was what made your rocket arc. If it’s not the power issue some have noted above (I didn’t look into that) then maybe it was a one-time thing where it caught a sudden gust of wind.

I hope your next flight goes straight up!

 

[Rocketclar]

Good comments and analysis above. I have several EZI-65's. In fact, my L1 was made on one. (I've since modified them for DD, but had flown the "stock" version on very similar motors including G80's along with a BoosterVision camera taped to the side with no problems. The only other comment I would add is a possible binding of a rail button as it was leaving the rail along with a gust of wind.

 

[Starfire73]

Good comments and analysis above. I have several EZI-65's. In fact, my L1 was made on one. (I've since modified them for DD, but had flown the "stock" version on very similar motors including G80's along with a BoosterVision camera taped to the side with no problems. The only other comment I would add is a possible binding of a rail button as it was leaving the rail along with a gust of wind.

I want to get into DD. Trying to decide if I want a new rocket or just mod my existing EZI with an Av bay and a new payload body tube. It’s that or an Apogee Katana.

I like my chute release but I’ve had a few reliability issues using it (prob operator error in the chute packing).

 

[Rocketclar]

I want to get into DD. Trying to decide if I want a new rocket or just mod my existing EZI with an Av bay and a new payload body tube. It’s that or an Apogee Katana.

I like my chute release but I’ve had a few reliability issues using it (prob operator error in the chute packing).

Here's a few pics of one of my first conversions of the EZI-65 to DD. Original had 1/2" lugs that I left on, but added the Acme conformational rail guides; used lower AF and added ebay. BTW....my 4" ebays are interchangeable between rockets. The pic on the sawhorse is just before doing a ground test of charges. For my first attempts at using shear pins, I glued metal washers on outside of top AF to help shear the pins. Now for cardboard AFs I reinforce holes with CA plus glue small thin pieces of brass shims on the inside to help shear pins off. Works well.

BTW....I used to live in Midland and all 3 of my kids were born there.

 

[Starfire73]

Nice! I think the EZI-65 is underrated. It gets good reviews, but it seems like everyone who wants to level 1 at my club uses a Zephyr or maybe a LOC IV. The EZI-65 is a perfect rocket to go bigger or smaller in terms of motor size.

 

[Rocketclar]

Here's another of my EZI-65's. Same ebay. Flies nicely on big I's or various J's. Many of my NCs are interchangeable since I move an Eggfinder sled between rockets. I also modified my ancient LOC-IV for DD. Here's a pic.....again same ebay.

 

[Starfire73]

Here's another of my EZI-65's. Same ebay. Flies nicely on big I's or various J's. Many of my NCs are interchangeable since I move an Eggfinder sled between rockets. I also modified my ancient LOC-IV for DD. Here's a pic.....again same ebay.

Rather than starting over with a new rocket to get into DD, I'm seriously considering converting my EZI. My payload bay body tube has the bulkhead and hardware epoxied in place, so I will have to get a new payload bay body tube in addition to the AV bay. That's ok. If I want to fly it single deploy I'll always have the original payload bay I can throw on there.

My question is, how long of a body tube did you use for your payload bay on your EZI? It looks like LOC sells the 3.9" BT in 34" lengths, but I'm not sure I want it stretched that much. I suppose I could put all 34" on there if I really want to change it up with the DD version.

 

[waltr]

I added DD to the LOC 4" (3.9") Goblin. Used an 18 inch long tube for the Main chute section. Two 30" chutes or single 50" chute easily fit with cords and Nomex blankets.

The other way to get the chute, cords etc and stuff them into the 34" tube then measure how much of the tube they fill. Add the Ebay couple and nose cone should length. Add a little and that is how long the tube much be.

 

[Tractionengines]

Just FYI,

LOC sells the AV Bay with a section of body tube. Just verify it's enough. (Shipping could be less than the 34", due to shorter box.)
https://locprecision.com/collections/rocket-components/products/electronic-bay-with-payload-tube

 

[Starfire73]

Just FYI,

LOC sells the AV Bay with a section of body tube. Just verify it's enough. (Shipping could be less than the 34", due to shorter box.)
https://locprecision.com/collections/rocket-components/products/electronic-bay-with-payload-tube

Thanks, I hadn't seen that.

Huh... the AV bay/15" BT combo is the same amount as the AV bay and 34" BT are if purchased separately. Like you said, maybe I could save it shipping a little bit. Otherwise, the only other benefit is a cleaner cut on the 15" BT, than if I cut down the 34" myself.

 

[waltr]

Thanks, I hadn't seen that.

Huh... the AV bay/15" BT combo is the same amount as the AV bay and 34" BT are if purchased separately. Like you said, maybe I could save it shipping a little bit. Otherwise, the only other benefit is a cleaner cut on the 15" BT, than if I cut down the 34" myself.

Yes, but first verify that a 15" tube is long enough to hold Chutes, cords, etc.
I bought the 34" tube + Ebay kit for the Goblin and cut to length I wanted.

 

[Rocketclar]

Rather than starting over with a new rocket to get into DD, I'm seriously considering converting my EZI. My payload bay body tube has the bulkhead and hardware epoxied in place, so I will have to get a new payload bay body tube in addition to the AV bay. That's ok. If I want to fly it single deploy I'll always have the original payload bay I can throw on there.

My question is, how long of a body tube did you use for your payload bay on your EZI? It looks like LOC sells the 3.9" BT in 34" lengths, but I'm not sure I want it stretched that much. I suppose I could put all 34" on there if I really want to change it up with the DD version.

The tan top AF in my above EZI-65 pic is 24" which is plenty long to house the cord, Nomex chute protector and chute. I, too, kept my epoxied original top payload AF and have sometimes put that back on to use with a JLCR.
As a sucker for sales, I got a couple of clearance fin sets from LOC and epoxied them onto separate bottom AF's. The fins were originally for the LOC-IV and a Hyperloc. I put different top AFs on those. They fly DD since I've standardized interchangeable ebays. In fact most of the time I fly a PML upper AF on those since I like the piston ejection for the main. I mix and match my bottom and top AFs.

 

[shockie]

What happens when you increase rail length from 5-6 ft to 8-9 ft? Velocity off rail?

 

[Starfire73]

What happens when you increase rail length from 5-6 ft to 8-9 ft? Velocity off rail?

I’m not sure but it’s flown three times prior on the same rail with no issues.

 

[kjhambrick]

YouTube video of onboard camera.

EZI-65 on board video, YouTube

This was one of the few launches (unfortunately) in which I did not get any video from the ground.

@JimJarvis50 has me thinking about rail whip.

No ground video to review and the rail is hidden by the smoke from the I140 but do you recall if the rail oscillated after liftoff ?

Could your flight trajectory possibly be due to random rail whip ?

If that is the case, then a longer unreinforced rail could make things worse, not better !

-- kjh( still thinking about this flight )

EDIT: P.S. Jim also noted that more thrust could actually make rail whip worse, not better and that makes perfect sense too !

 

[Starfire73]

Could your flight trajectory possibly be due to random rail whip ?

If I had to guess I would say probably not, for a number of reasons. But I guess we’ll never know.