Joe Turners L2 Build Thread

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OverTheTop
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Re: Joe Turners L2 Build Thread

Postby OverTheTop » Thu Feb 08, 2018 4:58 pm

Any masking tape will pretty much work in that situation. Blue is just what I have on-hand, and it doesn't seem to leave as much sticky mess on the harness. I have used "ordinary" masking tape in the past as well, successfully, in this setup.

I have seen a spinnaker sail taped ever so gently into a ball so it could be thrown into the air (picture throwing a basketball) during a race and the gentle tug on the lines as they went taught would have it unfurl in an instant. Unfortunately it didn't work as planned. As we rounded the mark and lofted the load it just sat there spherically. There was a lot of swearing and yanking on lines to get the thing to unfurl. Cost our boat about ten seconds. Only two pieces of tape!
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Re: Joe Turners L2 Build Thread

Postby joeman » Sat Feb 10, 2018 5:54 pm

Yes, you have to think carefully about what you tape!

I finally got the time to do another test. Did up a video below....added a few stills as well.

https://youtu.be/tN18Zan5K3s

Z-Folds remained, but I expect that as the drogue parachute inflates, the tape will rip...and the ripping will reduce the forces on rocket/drogue chute.

That was with 5 grams of charge.

What do you guys reckon?

Cheers

Joe
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby SpaceManMat » Sat Feb 10, 2018 6:50 pm

Looks pretty good to me, plenty of energy but not stupid amounts. All the important bits are well out.
I wouldn’t wind the cord around your chute protector though, that’s asking for issues.
If you have a backup charge add 30% say 6.5g, should get you out of a sticky situation.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Joe Turners L2 Build Thread

Postby joeman » Sun Feb 11, 2018 8:56 pm

Thanks SpaceManMat.
Will take your advice and not wrap around the Blanket.

RE: Main Chute
Decided to do one last test (#3 test) of the main parachute - with 3.5grams . My previous test was with 4 grams and it was quite energetic. All but one of the Z-folds was "released". Figured that with 3.5 grams the Z-folds would probably remain...but still get everything out...take the "edge" off it.

https://youtu.be/hwPCHpQ9P-Y

Seems to have done the trick.

RE: Main Chute deployment Timing
I've decided to increase it form the standard 700ft to 1000 ft. Just want to make sure it has all the time it requires to properly deploy.

Next Steps...
Ready rocket for sending down to Goldcoast this week.
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby SpaceManMat » Sun Feb 11, 2018 9:36 pm

I’m thinking that pretty much boarder line there. Sure it does the job in this test, but on any given day there will be different conditions causing variation in the outcome. For instance different temperatures may result in tighter fits, perhaps you measure the charge slightly wrong or drop a bit, accidentally wedge some tape on the coupler, powder not packed as tight etc. Point is you want a good margin on the deploy. I personnelly didn’t see an issue with 4g, if your concearned then perhaps consider 3.8. I’d like to see others thoughts on this one.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Joe Turners L2 Build Thread

Postby joeman » Mon Feb 12, 2018 8:48 am

Hi SpaceManMat,
Yes, I see your point. Makes sense.
* Always good to have a little more change than too little.
* Nothing is exact....there is a range of possible outcomes (an error margin).

The mode of ejection is a sliding scale...but with key points below...

- nose cone comes off (without parachute)
- nose cone comes off with parachute just coming out (un-expanded, or only partially expanded)
- nose cone comes out with parachute fully expanded - shock cord still z-folded
- nose cone comes out with parachute fully expanded - shock cord z-folds "released"
- nose cone comes out with parachute fully expanded - shock cord z-folds "released", rocket booster is jolted forward an unhealthy distance forward due to nose cone "pulling" on it.
- .... some failure; shock-cord, or some other component ....

(NOTE: These modes of ejection aren't necessarily linear)

So with 3.5 grams, it was:-
- nose cone off, parachute partially expanded, shock cord still z-folded...

So perhaps at the lower end of this scale. Upper error margin is considerably greater than lower error margin.

Thanks for feedback. Giving me plenty to think about.


RE: Backup charges
I'm not using backup charges, but I do wish to use the motor ejection charge as a backup...have it delay by 2 seconds past apogee. So I assume I can put the 6.5 grams in there, to kick it out?
(I still have to read up the business of sizing backup charges).
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby SpaceManMat » Mon Feb 12, 2018 9:13 am

CTI have the instructions on their website, which You should make yourself farlmilar with. But you want to top up the charge not add the full amount again, otherwise you’ll end up with a rain of rocket parts. Also don’t forget to adjust that figure if you go with lower primary charge, I’d think 6.5g would be a pretty big whack. Also keep in mind that your altimeter will take up to a second to detect apogee and fire the charges. You don’t want a motor ejection charge set any sooner than 2 seconds after apogee otherwise you risk doubling up on the charge.

NOTE: The ejection charge on Pro54 motors is 2.0g of FFFFG black powder. If additional ejection charge is required, do not remove the white plastic cap. Instead, add additional powder on top of the cap and seal cavity with tape – it will ignite when the ejection charge is activated. Proper installation of the ejection cap is critical to ejection reliability – removal of the ejection cap could result in ejection failure and will void warranty.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Joe Turners L2 Build Thread

Postby joeman » Tue Feb 13, 2018 1:10 pm

Thanks SpaceManMat.
I'll get myself up to speed on that and have a plan in place ready for the day.

That reminds me, I'll also need to get tool to reduce delays.

Thanks

Joe
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby SpaceManMat » Tue Feb 13, 2018 5:11 pm

joeman wrote:That reminds me, I'll also need to get tool to reduce delays.


Comes with starter kit if you ordered it.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Joe Turners L2 Build Thread

Postby joeman » Sat Feb 17, 2018 11:34 am

ok..
Sorting out the PRo-dat54 tool.

Rocket with all the gear I think I'll need for the launch packaged up and sent off to Goldcoast.

Still a bit more work to do on doco to assist me with preparation and with details on the rocket. Besides that, all set.

See you guys on the day.

Thanks for your help and encouragement. It has been a great journey.

Joe
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby SpaceManMat » Mon Feb 19, 2018 9:10 am

Hope it all goes to plan Joe.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Joe Turners L2 Build Thread

Postby CATO » Thu Feb 22, 2018 6:07 am

Good luck with the L2 Joe...
"In thrust we trust"

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2018: 14,767 Ns (44% N)
Ns 17: 5,973; 16: 34,558; 15: 35,955; 14: 6,016; 13: 10,208
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Re: Joe Turners L2 Build Thread

Postby OverTheTop » Thu Feb 22, 2018 7:23 am

Hi Joe. Hope the flight goes well for you.

Can I suggest giving somebody the task of photographing the prep and flight for you? That means you will get some good shots of it and not have to worry yourself. Also, make sure they get a good shot of you and the rocket at the pad, without the top of the rocket being cut off :)
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Re: Joe Turners L2 Build Thread

Postby joeman » Tue Feb 27, 2018 7:22 am

Thanks guys.

Yes, It is a little surreal. Everything is coming together. Rocket + Extras has arrived safely at Goldcoast yesterday ... almost everything booked.

Just writing up a document with my steps for the day...instruction manual + Check List. Don't want to miss a thing.
Occasionally re-familiarizing myself with some other procedures/steps.

Good idea about photography. Yes, I had planned on bringing a proper camera down. Will figure something out.

Cheers

Joe
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO

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Re: Joe Turners L2 Build Thread

Postby joeman » Fri Mar 30, 2018 6:20 pm

Hi,
Well, the build has finished, launch was terrific and the learning never stops.

Blake advised me that this rocket should be flyable with a lower-powered M motor.
This got me thinking about what is the limiting factor in this rocket.

I've thought about all the possible failure modes, and I'm guessing that it is fin failure that is the limiting factor. i.e. the speed gets so great that there is fin flutter and they are ripped off. Not content with that, I've found some information about fin flutter and how to calculate the velocity at which flutter becomes a problem.

I found a useful Apogee article on fin flutter which has a collection of equations for calculating the min fin flutter speed. I've applied them to the forward and aft fins. The aft fins are smaller and so the flutter speed is greater than the forward fin. So I focused my analysis on the forward fins.

I calculated the flutter speed to be ~1000m/s. It varies a little with temperature and air pressure, but is generally around that region.
(Used a G of 1.73MP)

With a 20% safety factor, we have a max rocket speed of 800m/s
With a 50% safety factor, we have a max rocket speed of 500m/s.
50% probably more appropriate because fin material G12 is orthotropic.

So... running a few simulations...
* With 5198-M1101 we have a max velocity of 351m/s - OK
* With 6421-M1300 we have a max velocity of 391m/s - OK
* With 7328-M2045 we have a max velocity of 490m/s - OK
* With 8181-M1545 we have a max velocity of 459m/s - OK

* With 9977-M2245 we have a max velocity of 581m/s - Not OK


All these speed for the first 4 motors are acceptable ... assuming 50% is suitable safety factor and my calculations are correct.

I can only imagine that choice of a low M-motor is just a very cautious choice, or that there are other potential modes of failure that I have not considered. What do other people think?

FYI, the build I did is not optimised for speeds > Mach 1, so it would have particularly high drag.
I don't have any plans at this stage to try and put an M-motor in this for L3 attempt. I'm more curious.


Cheers

Joe
L1 - Callisto (H133) - 11-Jan-2016
L2 - March Fly (1633K940) - 18-Mar-2018 - RSO


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