Level 2 Build - Madcow Level-2 via Apogee Components

[ThePlmbr]

Congrats on your level 2 flight! Good looking rocket. I love a sparky motor.

 

[kcobbva]

Kevin - a big congrats on your L2!! I remember that nervousness & jitters like it was yesterday (cause it almost was, 6 months ago), you did a great job. Also, a very big thank you for a great build thread, I've just ordered my first all-glass kit (Madcow Frenzy XL 3"), and I'll definitely be rereading your posts for tips as I go... This is truly the value of TRF, sharing information to aide in the success of many... Again, thanks for a great thread!! :handshake:

Thank you very much! You really need to speak with Nathan (that's his name and handle on here). He launched a frenzy today on a sparky. Was really awesome; and he really does a sweet paint job as well!

 

[kcobbva]

Thanks everyone for the kind words. It was an awesome day today! We had 60mph winds last night and this morning it was blowing chairs over in our yard. Regardless, my oldest and I drove to Battlepark in hopes we'd find a clear window to launch the Level-2 "RumbleBee". Thankfully that was a very good choice! When we got there it looked like the wind took out the Portapotty as it was on it's side. Was a hold it kind of day! Anyway, the winds subsided and I got to launch on a J250 Sparky. I decided hitting 5k in the wind was nuts, so backing it off was the right thing to do and gotta say, sparkies are REALLY cool! Also I've said it before, but one last time: Thanks Teddy. GREAT RECOVERY HARNESS!


After the Level-2, we decided to try to rip the fins off last month's Level-1 bird, the Torret, by shoving an I540 in it an hitting 3489ft and the stratologger said 740fps for velocity. It screamed off the pad. SO COOL!


Finally, we pulled out a rocket I scratch built about 12 years ago for my oldest son, 7 back then, because he asked "Wouldn't it be cool if you could put my GI Joe in a rocket and launch him?" So I designed one and we shot it one time. It was resurected today on a G76 and had a beautiful flight. Joe came out and seemed he never wanted to come down. The rocket landed two pads over from where it left. What a great day. Moreover, I think my son just might be interested now in building a fast rocket and joining me. THAT is the best thing that happened today!


Here's the video. Sorry, yes, had the bumblebee transformer in mind so that's the sound. The video has both the ground view and the onboard camera view.

[VIDEO=youtube;qmvtBitIH2w]https://www.youtube.com/watch?v=/qmvtBitIH2w[/VIDEO]

 

[Tim51]

A case of congratulations to us both! It's a great feeling, isn't it?

 

[BDB]

Great flight. How do you embed the altitude and time into your video?

 

[kcobbva]

Someone had posted a method some time ago and I'd set it aside for later use. It's a free program called Dashware. You have to tweak the output of your altimeter a bit to get it to time perfectly, and the output will be less quality than that of your original; but...it is a pretty cool output. I was asked about that earlier today as well. If I get some time; I might do a little "how to" writeup, at least for what i've done, and post it out here.

 

[kcobbva]

A case of congratulations to us both! It's a great feeling, isn't it?

Amen! No other word can get close enough! Congrats to you!!!!

 

[Nick@JET]

Congrats Kevin! Love that nervous feeling during the count down then again editing for the main!
That's really awesome! Beautiful rocket

 

[kcobbva]

Congrats Kevin! Love that nervous feeling during the count down then again editing for the main!
That's really awesome! Beautiful rocket

Thank you..and man you have that so right! It is a nervous and exciting moment all wrapped up into one!! ��

 

[NJRick]

just SPECTACULAR!!!! way to go!!!!

 

[kcobbva]

just SPECTACULAR!!!! way to go!!!!

Thank you Rick. Very kind indeed!

 

[Buckeye]

Great on-board video! No nausea-inducing roll, like my videos. What is the key to minimizing roll?

 

[kcobbva]

Great on-board video! No nausea-inducing roll, like my videos. What is the key to minimizing roll?

Thank you very much. Honestly on the way up is the fin alignment. Get them on dead straight; and they pretty much fly dead straight. https://www.payloadbay.com/index.php?page=Tools&action=FINGUIDES Thankfully the payloadbay.com One the way down, the drogue makes the roll; but the main, sized a tad over; seems to really make it float. Maybe it's the type: Loc Angel, more likely luck. I know my Level 1 Torrent was pretty straight on it's maiden flight; but I eyeballed the fins.
[VIDEO=youtube;Vnwpm4FeMvk]https://www.youtube.com/watch?v=/Vnwpm4FeMvk[/VIDEO]

There is definitely a little offset though as it's second flight turned half way around with a much larger engine. With more thrust, the spin is more evident:
[VIDEO=youtube;0ly6jPcP-rg]https://www.youtube.com/watch?v=/0ly6jPcP-rg[/VIDEO]

I think this time, making and using the fin guide on the Level-2 really made the difference.

 

[Hobie1dog]

Inspires me to get going on my Level 2 from Apogee, great flight, congrats.

 

[KilroySmith]

After the Level-2, we decided to try to rip the fins off last month's Level-1 bird, the Torret, by shoving an I540 in it an hitting 3489ft and the stratologger said 740fps for velocity. It screamed off the pad. SO COOL!

You're going to have to try harder than that. I just got my L2 today with the Torrent on a J270, going to 4219 feet. Haven't downloaded the data, so I don't have a speed, but OR estimated 715 fps. Of course, OR underestimated altitude by 500' so I'm guessing the speed was a bit higher. That Torrent is a great bird.

 

[kcobbva]

You're going to have to try harder than that. I just got my L2 today with the Torrent on a J270, going to 4219 feet. Haven't downloaded the data, so I don't have a speed, but OR estimated 715 fps. Of course, OR underestimated altitude by 500' so I'm guessing the speed was a bit higher. That Torrent is a great bird.

Way cool! I bet it really ripped on that!! Sounds like I have an objective to accomplish now! �� I absolutely agree with you; it is a great bird.

 

[kevinkal]

While I'm on it, I had someone mention at the club event that when flying L-2 and above, you should also put shear pins in the aft portion of the e-bay/body tube like I do with the nosecone. I hadn't heard or read that before; and am curious what thoughts are regarding that. I didn't do that on the L-1; but it sounded plausible to me, and if the ejection forward can shear them; why not the aft. Anyway, curious if anyone has any insight there.
Kevin

In regards to shear pins for your aft/drogue section, that is a matter of preference. People do it both with and without successfully. On the 4" scratch built rocket I used for my L2 I did use shear pins both aft/drogue and nosecone/main. I lean that way because I feel like there is a little less need to mess around with the fit of the coupler, but friction fit will work. Whatever you decide, get it 'dialed-in' with your deployment charges during ground testing.

I was thinking about why the Apogee/Madcow Level2 kit builds stock with with shear pins for the nosecone/payload section, but apparently a friction fit for the aft fin can drogue section. What occurred to me was that if shear pins were used on the aft/drogue section, then when using a motor that has an ejection charge, would the motor's ejection charge be sufficient to provide the redundant droque separation at Apogee should the drogue BP charge fail? I guess it boils down to how much BP is required to shear those pins reliably and if the motors aft closure can hold that amount.
In Tim's videos, his rocket was saved by the motor ejection charge separating the friction fit aft section and drogue... would it have separated if it had shear pins instead?

 

[rharshberger]

I was thinking about why the Apogee/Madcow Level2 kit builds stock with with shear pins for the nosecone/payload section, but apparently a friction fit for the aft fin can drogue section. What occurred to me was that if shear pins were used on the aft/drogue section, then when using a motor that has an ejection charge, would the motor's ejection charge be sufficient to provide the redundant droque separation at Apogee should the drogue BP charge fail? I guess it boils down to how much BP is required to shear those pins reliably and if the motors aft closure can hold that amount.
In Tim's videos, his rocket was saved by the motor ejection charge separating the friction fit aft section and drogue... would it have separated if it had shear pins instead?

Most standard motor ejection charges can hold enough powder to shear three nylon screws (2-56 or 4-40, ground test to make sure) in a smaller airframe, my 5.5" Cherokee D only uses 2 grams of BP in the drogue charge and it not only shears three 4-40s but also straightens the z-fold 30' harness to max during ground testing,and during flight (Lower Payload bay is 5.38" by 19").

 

[kevinkal]

Most standard motor ejection charges can hold enough powder to shear three nylon screws (2-56 or 4-40, ground test to make sure) in a smaller airframe, my 5.5" Cherokee D only uses 2 grams of BP in the drogue charge and it not only shears three 4-40s but also straightens the z-fold 30' harness to max during ground testing,and during flight (Lower Payload bay is 5.38" by 19").

Thanks Rich. This is definitely something I need to get a handle on. That's interesting data, seems the 5.5 inch diam helps with force.. but you also have sufficient momentum/velocity to thrust the section 30' is amazing for just 2g BP. I was just watching Kevin's drogue ejection ground test video. I think it showed that 1.4 g BP and three 2-56 pins failed, but 1.7g BP and just two 2-56 pins worked. I guess it all boils down to pressure over area and number of pins.

 

[kevinkal]

This time I am weighing EVERY darned part of the system. I'll know what has been added via epoxy so I can keep real close track in my log book. Figure this will only help me later if I attempt an L-3. It's also St. Patties, so I have to enjoy something while working!!!
View attachment 285369

Kevin,
I've been following your thread with much enthusiasm. Thanks for all the details and congrats on your successful flight and L2.
I've been trying to get a handle on what the actual finished weight will be without the motor installed. What did your final weight turn out to be?
Thank you.
Kevin K.

 

[kcobbva]

I was thinking about why the Apogee/Madcow Level2 kit builds stock with with shear pins for the nosecone/payload section, but apparently a friction fit for the aft fin can drogue section. What occurred to me was that if shear pins were used on the aft/drogue section, then when using a motor that has an ejection charge, would the motor's ejection charge be sufficient to provide the redundant droque separation at Apogee should the drogue BP charge fail? I guess it boils down to how much BP is required to shear those pins reliably and if the motors aft closure can hold that amount.
In Tim's videos, his rocket was saved by the motor ejection charge separating the friction fit aft section and drogue... would it have separated if it had shear pins instead?

I ended up with two shear pins in the aft section with 1.7g of ffff black powder. No issues with separation. After listening to the folks here and talking to locals at launches; I am glad I did put the shear pins in.

 

[kcobbva]

Kevin,
I've been following your thread with much enthusiasm. Thanks for all the details and congrats on your successful flight and L2.
I've been trying to get a handle on what the actual finished weight will be without the motor installed. What did your final weight turn out to be?
Thank you.
Kevin K.

Kevin,
I was absolutely LESS than what the Rocksim file shows. I weighed every little piece during that build. In Rocksim I did a mass override of 146 oz and the cg at 40". Without the Mass override it stated 148.89oz and 38.6" for the CG. Neither of which was actual. So I left my overrides in place. Hope that helps.

Thanks Rich. This is definitely something I need to get a handle on. That's interesting data, seems the 5.5 inch diam helps with force.. but you also have sufficient momentum/velocity to thrust the section 30' is amazing for just 2g BP. I was just watching Kevin's drogue ejection ground test video. I think it showed that 1.4 g BP and three 2-56 pins failed, but 1.7g BP and just two 2-56 pins worked. I guess it all boils down to pressure over area and number of pins.

I have to admit, I was surprised that the 1.4 failed. My Bp calculator stated it was the proper amount. I guess THIS is why we ground test! I will say I had three shear pins (I didn't listen to everyone). I removed one and upped the charge and as the video showed got a good separation (not only in ground test, but also in flight).

 

[kevinkal]

Kevin,
I was absolutely LESS than what the Rocksim file shows. I weighed every little piece during that build. In Rocksim I did a mass override of 146 oz and the cg at 40". Without the Mass override it stated 148.89oz and 38.6" for the CG. Neither of which was actual. So I left my overrides in place. Hope that helps.

I have to admit, I was surprised that the 1.4 failed. My Bp calculator stated it was the proper amount. I guess THIS is why we ground test! I will say I had three shear pins (I didn't listen to everyone). I removed one and upped the charge and as the video showed got a good separation (not only in ground test, but also in flight).

Thanks Kevin. I just ordered a kit last night, so I hope you don't mind that I'll probably hound you with some questions in the near future. =]
When you put in your mass override figures, mass override of 146 oz and the cg at 40", was that including your motor? If so, which motor?

 

[kcobbva]

Thanks Kevin. I just ordered a kit last night, so I hope you don't mind that I'll probably hound you with some questions in the near future. =]
When you put in your mass override figures, mass override of 146 oz and the cg at 40", was that including your motor? If so, which motor?

Kevin,
I have learned so much from so may people on this forum that it'd just be flat WRONG not to help out! Anything I can possibly help with I'd be more than pleased to do so.


As for the Mass Override. That is dry weight. Once a motor is put in, rocksim adjusts accordingly. I anticipated on flying on a J355. However, with the winds expected, and indeed present on the day of the launch, I did not want to attempt 5k feet. Wouldn't have questioned it on a calm day....but.


Anyway, so I finally decided on a J250. With the motor I think it showed 10.7 lbs at the launch. It was right at the 5:1 thrust ratio. A beautiful, straight flight to just over 2K; so in full view at all times and only came down 70 yards from the launch site. Plus it was a Sparky..so that was a bonus to get to see fly!

 

[kcobbva]

Thanks Kevin. I just ordered a kit last night, so I hope you don't mind that I'll probably hound you with some questions in the near future. =]
When you put in your mass override figures, mass override of 146 oz and the cg at 40", was that including your motor? If so, which motor?

Kevin - If it helps, here's my Rocksim adjusted file. It's in zip format because it wouldn't let me upload the .rkt for some reason.
View attachment level2-FG4in Weighed with camera shroud.zip

 

[kevinkal]

Thanks Kevin!
I've watched your video a good number of times. It was a beautiful launch. I was impressed with the fact that you Level 2 did not even rotate 1 full rev during the ascent. Nice work on those fins.
I have not invested in a tracker yet either.. and thus I'm planning to keep altitude down until I'm confident that I'll get it back. The J250 was perfect. Here in CA, I may not be able to fly a sparky motor in the near future when the grasses dry up.. likely by May. One of the items I just ordered from Apogee was an Aeropack 54-38mm adaptor, since there's plenty of 38mm reloads that will put this bird up to 2k+ feet and meeting the Level 2 cert J-impulse requirement.

 

[kcobbva]

Just bear in mind that you need to ensure the 5:1 thrust weight ratio. The 250 was close, by the RSO and I agreed it could fly when I discussed my sims. It did well.

 

[kevinkal]

Just bear in mind that you need to ensure the 5:1 thrust weight ratio. The 250 was close, by the RSO and I agreed it could fly when I discussed my sims. It did well.

My kit arrived and I've only washed the tubes at this point. The inside of the tubes still seems like there may be a thin smooth film of mold release or something else still there. I'll just be sure to sand and roughen any bonding locations with sandpaper.
The Aero Pack 54mm "P" retainer slides right on either side of my 54mm tube. I've noticed that all these fiberglass tubes don't seem to have strict tolerance control. I think I'm seeing up to 0.010" variation in diameters and wall thickness.
I'm going to read the RocketPoxy instructions and call it a night. tomorrow I'll start bonding items, starting with the forward CR to the motor tube. I watched your video a few more times too. =]

I picked up an Aeropack 54-38mm adapter, and a Rouse Tech 38/720 Motor, and a AeroTech I327DM and I600R. It looks like I'll have 3 reloads to choose from for my L2 cert flight: J350W, J420R or J500G. All of these should get her off the pad quickly. I'm a little worried about being overstable. I've made an OpenRocket model, and I'm over 2 calibers stable on even larger motors. What does your Rocksim model predict for stability margin on your J250 cert motor? (I can't run Rocksim unless I buy it.. my 30 days were up)

Oh, I need to resolve a main parachute issue. My kit had only a 36" main chute in it... not going to cut it for this size bird... working to resolve that now. So what made you toss the stock parachutes and go with others?

 

[Steve Shannon]

snip...

The Aero Pack 54mm L retainer slides right on either side of my 54mm tube. I've noticed that all these fiberglass tubes don't seem to have strict tolerance control. I think I'm seeing up to 0.010" variation in diameters and wall thickness.

...

The L type retainer body fits the thinner Loc style paper motor mount tube. The P retainer fits the slightly thicker phenolic tubing and those G-10 or Blue tube tubes which are sized the same.
Here's the sizing chart:
https://aeropack.net/webstore/partnumbers.asp
If your L type is too loose, how do your centering rings fit? I would expect the L type to be a very tight fit.
Edit: I'm still getting used to the thin wall g10. [emoji15]
Just be sure to sand the OD of the MMT before gluing the retainer body on with JBWeld and you should be fine.
[emoji1010] Steve Shannon, USA [emoji1010]

 

[kevinkal]

The L type retainer body fits the thinner Loc style paper motor mount tube. The P retainer fits the slightly thicker phenolic tubing and those G-10 or Blue tube tubes which are sized the same.
Here's the sizing chart:
https://aeropack.net/webstore/partnumbers.asp
If your L type is too loose, how do your centering rings fit? I would expect the L type to be a very tight fit.
Edit: I'm still getting used to the thin wall g10. [emoji15]
Just be sure to sand the OD of the MMT before gluing the retainer body on with JBWeld and you should be fine.
[emoji1010] Steve Shannon, USA [emoji1010]

Thanks Steve. The sizing chart showed my error... I mistyped.. I should have typed a P. I seem to be equating P with Paper tubes.. but it's for Fiberglass as I understand it.
I'm not certain what type of fiberglass tubes these are. they appear to be filament wound. Is that the same as G10? I am familiar with G10 plates.. solid as heck. The fins are what I understand to be 0.132 G10 plate, no bevel. The bulkheads and centering rings are what I understand to be 0.100 G10.

Here's some detail on the darn 54mm motor tube:
It's 12 inches long, but has significant variation in wall thickness and OD depending on what section I measure. The ID is consistent.
Wall thickness:
One end has wall thicknesses variation between 0.0585" and 0.060" around the circumference, but the other end has wall thicknesses variation between 0.051" and 0.058" around the circumference.
OD:
One end is 2.274" OD, and the other end is 2.266" OD.
ID:
One end is 2.159" ID, and the other end matches well as 2.159" ID. There is little variation around the circumference for the ID.

Per the Aeropack chart you've linked, 54P = 2.278”. Thus I see why my retainer slides on so easily. I plan to mount the AeroPack retainer on the thicker side of my motor mount tube. I suspect the JB Weld will have no trouble filling the 0.004" gap. The forward centering ring will have a loose slip fit and need the Rocketpoxy (Glenmar G5000 High Strength Epoxy) to fill the gap. Apparently, rocketpoxy is good stuff. I just looked to see what the hardest "hitting" 54mm motor would be for Aerotech... It's the J1999. That's about 450 lbs of thrust. I hope those 2 centering rings are up for the task should I ever load one of those hard hitters.