EZI-65 (heavily customized) on I115; is it too heavy?

[user 30299]

Not yet. I was talking with jmasterj about it though, and I'll be printing an adapter, at least for 38mm motors.

3D Printed Adapters is out of my wheelhouse.

If you're trying to stick with AeroTech DMS motors here are two additional suggestions for your EZI-65.

• I-205W - 29mm motor

This gets you approximately 58 fps off the rail (standard 8 ft., 1010 rail), and 1700' for apogee.

• I-285R - 38mm motor

This gets you approximately 67 fps off the rail, and 2045' for apogee.

This is using RockSim. Your CP is nearly identical to mine. And I used your weight and CG location in the sim.

I'm assuming your CG is the actual, not one determined by the software.

My choice would be the I-285R because the red flame is awesome. (and a little more speed on the rail is always good)

 

[kjhambrick]

Lol, if it's beefy enough, it should handle the load, and petg has been pretty good to me so far as far as heat tolerance. I should probably ground test it first. I'd probably just make a rig to put weight on it, and then use my heat gun to simulate the heat of the engine. I'll bring it to the edge of failure and if it holds up to that abuse for more than a minute, and if it does, it should be more than enough.

Printers are so worth it as a rocketeer. My printed designs are very modular so I can reuse parts like rocket legos almost lol. It makes it easier to replace and modify parts, as well as just easier to plan arranging parts in tight spaces.


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It also allowed me to place the gopro more predictably within the rocket so I could minimize the viewport.

That is so kool.

Thanks, @Aeva !

-- kjh( I would have bought some cardboard motor mount tubing and made some plywood rings and then I would have done something ugly with sandpaper and epoxy and masking tape )

 

[kjhambrick]

P.S. I also really like that you're considering the axial CG for the stuff in your rocket.

Everything back in the 90's was done with one degree of freedom,

Aligning your center of mass along the axial centerline of your EZI is very kool too !

-- kjh

 

[Aeva]

Thanks kjhambrick!

 

[cls]

I would have bought some cardboard motor mount tubing and made some plywood rings and then I would have done something ugly with sandpaper and epoxy and masking tape

LOC Precision MMA 4, 54mm to 38mm https://locprecision.com/collection...ts/motor-mount-adapter?variant=39778639249599

$cheaper and lighter than 3D printed, but not as up school 21st century!

 

[tsmith1315]

$cheaper and lighter than 3D printed

And if you have the materials, it’s much faster as well.

 

[cls]

And if you have the materials, it’s much faster as well.

oh man ... true confessions... I have a drawer full of various MMA kits, another full of parts. and another full of ebay kits, mostly 3" and 4", but others too, and parts... scratch builds are real quick.

 

[Titan II]

Be glad you fiberglassed your EZI... I got my L1 on an EZI-65 built mostly stock (I fiberglassed the fins) on an H128W. I zippered it on the 3rd flight on an I210R. The 4" LOC BT is very thin, which is good for weight, but not so much for durability.

The 4" LOC BT is the same size as Madcow's, and is plenty strong and durable. You properly mitigate zippers with careful planning.

 

[kjhambrick]

oh man ... true confessions... I have a drawer full of various MMA kits, another full of parts. and another full of ebay kits, mostly 3" and 4", but others too, and parts... scratch builds are real quick.

Me too

But I need to make an 18mm MMA for a 29mm MMT because I've never had a rocket with a 29mm motor mount that was light enough to fly 18mm motors and now I do !

Getting together all my 1990's tech to make one

-- kjh

 

[waltr]

Yeah, I'm definitely gonna up the thrust with another motor. The main reason I "overdid" my rocket was to minimize chances damage to it if something going wrong... it would a shame to lose it because beefy additions weighed too much.

Also heck yeah, that's the day I'm going too. See you there!

Did you do your Cert flight Sunday?
I was down there at MDRA but didn't see an EZI-65 cert flight.

Oh..I should have commented on your above statement:
One should not build a flying machine (rocket) for when something goes wrong....It should be build to PREVENT something going wrong. As Leonardo Da Vinci stated, "If you build your flying machine to withstand a crash then the first one will be BAD". This means heavy hits harder.

 

[Aeva]

Did you do your Cert flight Sunday?
I was down there at MDRA but didn't see an EZI-65 cert flight.

Oh..I should have commented on your above statement:
One should not build a flying machine (rocket) for when something goes wrong....It should be build to PREVENT something going wrong. As Leonardo Da Vinci stated, "If you build your flying machine to withstand a crash then the first one will be BAD". This means heavy hits harder.

I didn't... @SparkyVT offered to let me fly it on one of his experimental motors but I chickened out (tbf I lost two other rockets that day... it was rough). I wasn't able to get an engine with the thrust I need for the L1 by sunday. Instead, I flew two of my printed rockets. I flew a 3d printed V2 (that was the one that CATO'ed early in the day; it was an already open motor reload and I didn't notice I was missing the spacer washer for that engine until I assembled another reload-- so it pre-detonated the ejection charge before doing a flip in the air and slagging itself-- Dali would be proud of the aftermath). The other one I flew was my "Yamadori" rocket it was the blue/silver one that got stuck on a telephone pole. You probably saw it hanging there on your way home lol

Edit: Yamadori pics/vid:



Ah, that just semantics /s lol... but yeah I definitely can say I overdid it. It's definitely was built to prevent something going wrong, but it's also built to minimize damage from what might go wrong. I didn't think about the "heavy hits harder" part though. I definitely will keep that in mind for my future HPRs.

 

[tsmith1315]

it. It's definitely was built to prevent something going wrong, but it's also built to minimize damage from what might go wrong. I didn't think about the "heavy hits harder" part though. I definitely will keep that in mind for my future HPRs.

One of the lessons you learn as experience is gained is just how much you don’t need to do. I can be fun to overbuild (and over analyze), but an EZI-65 built stock will fly on many L2 motors just fine. Choose the right baby J on a good day and you could build one on the field and cert that afternoon with pretty much only what comes in the bag.

 

[Aeva]

Yeah, it's my first HPR so I'll take it as a learning experience. That's part of the reason I bought it: for the potential L2 cert. Hopefully once I get that TWR up with another engine (I got an I175 yesterday from @jmasterj, and ordered an I215 from apogee... so I will have options for my L1), there will be no other issues I have to worry about. The other thing I wish I knew before hand was the communal preference for 38mm engines... I can make an adapter, but I notice that 38mm is one of the most preferred diameter engines in HPR.

 

[waltr]

I missed the CATO and didn't see your rocket on the pole. Think I also missed your "Yamadori" rocket flight.
Probably due to spending time in the woods (behind the flight line) looking for my LaserLOC.
Did find it at the top of a very tall beech tree. It is still there. Been debating on spending $400 for a climber to get it down or just write it off.

 

[Aeva]

I missed the CATO and didn't see your rocket on the pole. Think I also missed your "Yamadori" rocket flight.
Probably due to spending time in the woods (behind the flight line) looking for my LaserLOC.
Did find it at the top of a very tall beech tree. It is still there. Been debating on spending $400 for a climber to get it down or just write it off.

That's rough. I'm already considering my yamadori a write off since the hardware basically costs as much as the retrieval from the power company. That was my first midpower rocket, and it had some design flaws in the booster, so it gives me a chance to make some refinements and an opportunity to upgrade it. Also, since my V2 is scraped, it gives me the chance to build a bigger one since my dad keeps talking about his being bigger. Worst part is, he hasn't built his V2 kit lol

 

[Aeva]

here is all I got of the CATO. Not at all my best camera work and since it was so far away I had to crop the video.... meh

 

[Antares JS]

I missed the CATO and didn't see your rocket on the pole. Think I also missed your "Yamadori" rocket flight.
Probably due to spending time in the woods (behind the flight line) looking for my LaserLOC.
Did find it at the top of a very tall beech tree. It is still there. Been debating on spending $400 for a climber to get it down or just write it off.

That was your rocket? Sorry to hear that. I feel for you. I had some near misses with the trees and buildings that convinced me to scrub my Mega Alpha flight.

here is all I got of the CATO. Not at all my best camera work and since it was so far away I had to crop the video.... meh

I remember that one because that's my rocket sitting next to it on B5 and its liftoff was slightly delayed while the fire was put out...

It seems you learned something from that experience though. Be really careful with reloads, follow the instructions exactly, and make sure you have all the parts. Hope to see you next month, and I hope you have better luck.

 

[Aeva]

That was your rocket? Sorry to hear that. I feel for you. I had some near misses with the trees and buildings that convinced me to scrub my Mega Alpha flight.


I remember that one because that's my rocket sitting next to it on B5 and its liftoff was slightly delayed while the fire was put out...

It seems you learned something from that experience though. Be really careful with reloads, follow the instructions exactly, and make sure you have all the parts. Hope to see you next month, and I hope you have better luck.

Yeah, these are the mistakes I rather make on these midpower flights. I'm still pretty new to motor reloads, and from what I have read, that's the main reason motors CATO (bad assembly). I figure having that practice will make me more comfortable putting together HPR reloads. Sorry for delaying your launch though...

Yep yep! Looking forward to next month, see you there!

 

[John Taylor]

Barring a few things, I might be launching my EZI65 soon for an L1 cert. I definitely overdid it because I wanted it to be durable (it's fiberglassed), but also have some extra features (a go pro, and custom flight computer). The final result weighed in at about 2.28kg or about 5lbs without the motor. On paper it seems fine but from what I have been reading, my TWR may be a bit low (https://www.rocketryforum.com/threads/thrust-to-weight-ratio-5-1-or-3-1.14552/ suggests 5:1, mine is about 3:1 on average which is lower than I wanted.) Assuming that the club has an 8ft launch rail, the velocity off the rod will be just shy of 13m/s or 29mph.

I already purchased an engine from RCS because my original weight estimate was a bit lower (2kg no motor) and that seemed to meet the needs of my rocket... but I'm now I'm concerned that I picked an engine with too low average thrust. I know, I can just look at the information in other posts, I just want some feedback because I'm a bit committed to this rocket and the engine (since I already bought it <.<).

The last time I underdid the TWR it was a low powered rocket that turned ballistic missile... never again lol

Use Thrustcurve.org put in rocket specs and it will tell you which motors will work and which will not work as well as altitude, velocity, delay times, etc....
Free, fun, quick and accurate.