CTI J394 6gXL in MadCow Super DX3?

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Walldiver7

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I'm getting ready for my L1 And L2 attempts on the same day this coming weekend (and it looks like weather won't cancel this one!). For my L2, I'm thinking about (going for broke .. ha!) loading the Super DX3 with the CTI J394. This motor weighs in at about 940 grams. I don't have access right now to RockSim. MY question: How much nose weight do I need to add to fly this motor?

When I pack everything in the rocket for the balancing act... it appeared to me that somewhere between 6 and 7 oz would move the CG about 4" forward of the CP.

Comments please...... Thanks!
 
Is this the 4" Super DX3, or the 4" Fiberglass Super DX3? I don't know what the difference in CG is for the two, but the CP should be the same. Why do you think you will have to add nose cone weight?
 
Walldiver,

I flew my Super DX3 (cardboard) last fall on a Pro38 5 grain motor in the 6 grain case with a spacer and this is about the mass I used in the cone. First off, is this the cardboard / plywood kit or the fiberglass kit? I would imagine that you will be right at about 1 cal of stability if you are using cardboard with a ~15 oz payload bay. This is what my rocket's sim shows.

Doug
 
Is this the 4" Super DX3, or the 4" Fiberglass Super DX3? I don't know what the difference in CG is for the two, but the CP should be the same. Why do you think you will have to add nose cone weight?

It's the paper tube/ply version. The CP and the CG are right at the same point, so I thought it might be a good idea to add a little nose weight.
 
Walldiver,

I flew my Super DX3 (cardboard) last fall on a Pro38 5 grain motor in the 6 grain case with a spacer and this is about the mass I used in the cone. First off, is this the cardboard / plywood kit or the fiberglass kit? I would imagine that you will be right at about 1 cal of stability if you are using cardboard with a ~15 oz payload bay. This is what my rocket's sim shows.

Doug

Doug, This is the paper/ply 4" version. With the Main chute in the payload and the Telemetrum in the e-bay... I need to weigh all this... my guess is that it comes close to 7 or 8 oz in the payload.
 
I don't have access right now to RockSim. MY question: How much nose weight do I need to add to fly this motor?

Excuses, excuses... Get openrocket. In my opinion, it is more user friendly than rocsim, and I don't see any difference in accuracy.
 
It's the paper tube/ply version. The CP and the CG are right at the same point, so I thought it might be a good idea to add a little nose weight.

The CP and the CG shouldn't be at the same point, the CG should already be ahead of the CP by at least 1 caliber. But if it in not, then add nose weight, as you mentioned.
 
I'm sure you don't want to hear this, buuuuuut... Maybe you should consider slowing down a bit and taking some time to figure things out - it will greatly increase your chances of success.
 
I'm sure you don't want to hear this, buuuuuut... Maybe you should consider slowing down a bit and taking some time to figure things out - it will greatly increase your chances of success.

Just what I was thinking when I first read this post. The purpose of the Certs is to demonstrate understanding of the underlying science, not to demonstrate that you can follow advice or recipes. I know that comes off as harsh, but it is Monday and I am still on my first cup of coffee.

Slow your roll, enjoy the ride.
 
MY question: How much nose weight do I need to add to fly this motor?
The instructions tell you where the CG has to be; that's the Rocksim number for 1-cal stability. However you add nose weight, make sure it's securely attached.

I did my L2 on the same rocket and a CTI J285. Make sure you have a large area to recover, or are you doing dual deploy?
 
I'm sure you don't want to hear this, buuuuuut... Maybe you should consider slowing down a bit and taking some time to figure things out - it will greatly increase your chances of success.

Ditto. Your probably not going to get an answer as to how much nose weight to add, even if you do I wouldn't pay much attention to it. Any amount given will only be a guess, you need the rocket in hand to give/get an accurate amount.

FWIW take your time, crunch the number and concentrate on one cert at a time.
 
Anyone else think a Pro-38 6GXL load is going to shred a 4" paper rocket? I deeply distrust paper after seeing an excellently built aerotech kit shred on a wimpy H97, and madcow doesn't even use extra-thick body tubes. If your build isn't spot-on, my money is on confetti.
 
A well built 4" paper tube rocket will handle low thrust J and K motors. My 4" Madcow Frenzy flew on a K350 without any problem at all.
 
Anyone else think a Pro-38 6GXL load is going to shred a 4" paper rocket? I deeply distrust paper after seeing an excellently built aerotech kit shred on a wimpy H97, and madcow doesn't even use extra-thick body tubes. If your build isn't spot-on, my money is on confetti.

Nope.

We have a guy in out club that regularly flies his un-glassed Hyperloc 300 on I600's. Not sure how he's managed to find it back every time without a tracker but those flights are well over 4k. Not quite an apples to apples comparison but close enough.

Gotta be built right though. Good fillets, straight fins, etc.

-Dave
 
I have an un-glassed HyperLOC 300, which is pretty similar to the paper Super DX3 kit. I sent it up last month on a J340 Metalstorm and a J500 Green Mojave (well over a mile both flights) and it didn't even break a sweat. I'm planning to spank it with a J825 Redline and a J510 White Lightning next :)
 
I have an un-glassed HyperLOC 300, which is pretty similar to the paper Super DX3 kit. I sent it up last month on a J340 Metalstorm and a J500 Green Mojave (well over a mile both flights) and it didn't even break a sweat. I'm planning to spank it with a J825 Redline and a J510 White Lightning next :)

There's room in a HyperLoc 300 for a J825?

:y:

Just built one of those rockets...man I need a tracker baaaaaad.

-Dave
 
I have an un-glassed HyperLOC 300, which is pretty similar to the paper Super DX3 kit. I sent it up last month on a J340 Metalstorm and a J500 Green Mojave (well over a mile both flights) and it didn't even break a sweat. I'm planning to spank it with a J825 Redline and a J510 White Lightning next :)

PLEASE post about this launch!!! Wish I could be there to watch this!
 
The instructions tell you where the CG has to be; that's the Rocksim number for 1-cal stability. However you add nose weight, make sure it's securely attached.

I did my L2 on the same rocket and a CTI J285. Make sure you have a large area to recover, or are you doing dual deploy?

The Super DX3 instructions tell where the CP is.. and from that, you can determine where the CG should be. Originally, I had planned to do both L1 and L2 attempts as DD. Recently, I've decided to keep the motor charge intact and use the Telemetrum to fire the main chute at apogee. Why? I'm trying to make sure I don't have to repeat my 360 mile round-trip to perfom more attempts ( I live in the sticks (maybe I should say "sand" in NM) and Rio Rancho is my nearest launch.). I'm hoping for some pretty calm conditions..... if not, I'll enter the last reported coordinates in the GPS and start walking. Thanks for your reply!
 
There's room in a HyperLoc 300 for a J825?

:y:

Just built one of those rockets...man I need a tracker baaaaaad.

-Dave

Plenty of room, remember this kit was originally designed to take hybrid motors (HyperTEK I, J, and K 54mm tanks). I actually downsized the mmt on mine from 54mm to 38mm because I wanted to use the cool Aeropack tailcone retainer that I had (75-38) but now I kind of wish I hadn't. The J510 AeroTech motor (for the 38/1320 case) is as big as I can go, it's a little bigger even than the CTI Pro38-6GXL reloads, but I have a feeling that it still won't push this kit as hard or high as it could go. Sad to see potential that will never be realized. I definitely have GPS tracking in mine, but the funny thing is both of the flights I mentioned from last month landed within plain view of the launch pad. It was about a 500yrd walk from the J500 and about 385yrd after the J340. DD of course and a very calm day.

PLEASE post about this launch!!! Wish I could be there to watch this!

Sure, our next launch is coming up in about three weeks, I'll try to remember to post a pic here for you. Here's a couple from the J500 and J340 flights I mentioned...still in primer here, I actually just started getting some color on it today.

image.jpg

image.jpg
 
Plenty of room, remember this kit was originally designed to take hybrid motors (HyperTEK I, J, and K 54mm tanks). I actually downsized the mmt on mine from 54mm to 38mm because I wanted to use the cool Aeropack tailcone retainer that I had (75-38) but now I kind of wish I hadn't. The J510 AeroTech motor (for the 38/1320 case) is as big as I can go, it's a little bigger even than the CTI Pro38-6GXL reloads, but I have a feeling that it still won't push this kit as hard or high as it could go. Sad to see potential that will never be realized. I definitely have GPS tracking in mine, but the funny thing is both of the flights I mentioned from last month landed within plain view of the launch pad. It was about a 500yrd walk from the J500 and about 385yrd after the J340. DD of course and a very calm day.



Sure, our next launch is coming up in about three weeks, I'll try to remember to post a pic here for you. Here's a couple from the J500 and J340 flights I mentioned...still in primer here, I actually just started getting some color on it today.

Beautiful Pictures! I assume you were at least 100' feet away? What camera/lense where you using for these shots?
 
Going for L2 with the same model this weekend dual deploy with an AT J350 at KLOUDBurst. Initial Open Rocket configuration indicated 4 oz in the nose would get proper balance. Will first have shake down flight with AT H242 so first DD ejection can been seen from the ground. Will be ground testing ejection charges with fff BP and Q2G2 igniters over the next couple of days. Let's share stories after the weekend.
 
Going for L2 with the same model this weekend dual deploy with an AT J350 at KLOUDBurst. Initial Open Rocket configuration indicated 4 oz in the nose would get proper balance. Will first have shake down flight with AT H242 so first DD ejection can been seen from the ground. Will be ground testing ejection charges with fff BP and Q2G2 igniters over the next couple of days. Let's share stories after the weekend.

I went with 5oz of #8 birdshot in the nose. Luckily, I have a MadCow Frenzy (that I will build later) that uses the same nosecone, so I'll be able to fly the DX3 with stock or the weighted nosecones. My L1 flight with be with an CTI H125 Classic and the L2 with a CTI J335. Yes, I've decided to back off on the 6g XL motor for the L2 and instead use a little smaller motor. As I mentioned above, I will fly with the motor charge as a backup and let the Telemetrum kick out the main at apogee.. MAN, I sure hope it's calm that day!!!

Did you install shear pins? I did not. The fit is good, but this may proved to be a mistake.... we'll see. Thanks for the reply and looking forward to your report! Good Luck!
 
Beautiful Pictures!

Thank you :)

I assume you were at least 100' feet away?

Yes definitely.

What camera/lense where you using for these shots?

I have a Nikon D7000, using it with an 80-200/f2.8 lens and a 1.7x teleconverter. But the D7000 is a DX crop-format size sensor so that adds another 1.5x which brings it up to about a 500mm lens equivalent on 35mm/full format FX. The Mojave Green pic was taken with this combination. That is the full frame, not cropped at all, but it's hard to appreciate how much detail is there with the file size/resolution that you can upload here. I found that the difficulty with this setup is that you are almost too zoomed in on the action. I was lucky with that Mojave Green liftoff and caught exactly one good shot, by the next frame the rocket was long gone even with the shutter on high-speed burst and there was just a wispy smoke trail remaining. In tight with that much reach, without a bit of lucky timing it's very possible you could get no liftoff shot at all....there it is sitting on the pad, next frame gone (of course this is a paper kit, fully loaded about 90oz on the pad so it just rips on these J motors). So for the Metalstorm shot I went without the teleconverter, which put me at about a 300mm lens equivalent. The pic here is cropped in a bit, and you can definitely notice the loss of detail when comparing the two at full-resolution, but the trade-off is you have a lot more vertical space in the frame so you are much more likely to catch a usable pic before it vanishes. I also have to shoot this rig with a monopod, too much bazooka to hand-hold.
 
They're also both underexposed, whether intentionally through exposure comp, or because the camera correctly chose to expose on the bright white rocket body. Intentionally underexposing, then bringing up everything but the highlights in post, is a good strategy for capturing vivid flame colors.
 
They're also both underexposed, whether intentionally through exposure comp, or because the camera correctly chose to expose on the bright white rocket body. Intentionally underexposing, then bringing up everything but the highlights in post, is a good strategy for capturing vivid flame colors.

YES,... I used to take a LOT of 35mm pics.... with big lenses. I did enjoy those days! When the digital scene came to be, I just didn't seem to have the drive to start all over. Maybe this "new" subject matter will rekindle my interest?? Very cool pictures!
 
Thank you :)



Yes definitely.



I have a Nikon D7000, using it with an 80-200/f2.8 lens and a 1.7x teleconverter. But the D7000 is a DX crop-format size sensor so that adds another 1.5x which brings it up to about a 500mm lens equivalent on 35mm/full format FX. The Mojave Green pic was taken with this combination. That is the full frame, not cropped at all, but it's hard to appreciate how much detail is there with the file size/resolution that you can upload here. I found that the difficulty with this setup is that you are almost too zoomed in on the action. I was lucky with that Mojave Green liftoff and caught exactly one good shot, by the next frame the rocket was long gone even with the shutter on high-speed burst and there was just a wispy smoke trail remaining. In tight with that much reach, without a bit of lucky timing it's very possible you could get no liftoff shot at all....there it is sitting on the pad, next frame gone (of course this is a paper kit, fully loaded about 90oz on the pad so it just rips on these J motors). So for the Metalstorm shot I went without the teleconverter, which put me at about a 300mm lens equivalent. The pic here is cropped in a bit, and you can definitely notice the loss of detail when comparing the two at full-resolution, but the trade-off is you have a lot more vertical space in the frame so you are much more likely to catch a usable pic before it vanishes. I also have to shoot this rig with a monopod, too much bazooka to hand-hold.

Nice set-up you have.... These days, I backpack the CDT (Continental Divide Trail), and I just can't carry much more than a Point&Shoot. I would love to get back into it again though! Love that Mojave GREEN!! COOL!!!
My Super DX3, with everything but the motor and case, is exactly 67oz (1899.42grams).
 
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They're also both underexposed, whether intentionally through exposure comp, or because the camera correctly chose to expose on the bright white rocket body. Intentionally underexposing, then bringing up everything but the highlights in post, is a good strategy for capturing vivid flame colors.

Yes I figured out pretty quickly that if I did my light metering and set for "correct" exposure the pics would all end up over-exposed from the extra light of the flames. So now what I do is meter on the pad, then bump the shutter speed up until it indicates a full stop under-exposed and shoot at that setting. I can only do so much with them in post because I'm shooting jpegs, the D7000 is not a pro-level camera so the buffer can't really handle continuous RAW for long and I want to maximize my fps.

Edit: I don't know if I described that very well, I don't think the fire is so bright that it illuminates and over-exposes the entire scene (the background would still be correctly exposed) it's that at "correct" ambient metering the flames/highlights are completely blown out.

Nice set-up you have.... These days, I backpack the CDT (Continental Divide Trail), and I just can't carry much more than a Point&Shoot. I would love to get back into it again though! Love that Mojave GREEN!! COOL!!!
My Super DX3, with everything but the motor and case, is exactly 67oz (1899.42grams).

I know how you feel, I used to shoot a lot with an SLR back in the film days too, but then when things went digital I spent most of the last 10-12 years with just point-and-shoot cameras. What finally pushed me into a D-SLR a couple years ago was having a kid. But this is a great time to get back into photography, digital imaging technology has finally equalled and even surpassed what you could do with film. If size and weight are a concern for backpacking etc just have a look at what's going on with mirrorless cameras, you can get incredible images with very small kit these days. Check out: https://www.sansmirror.com/

Your Super DX3 and my HyperLOC 300 weigh in about the same. And they're nearly the same length but mine is an inch thinner so doesn't need any nose weight (I'm about three calibers stable) but I do have a Garmin GPS up front which is about the same as your bird shot ~5oz. Add one of your Pro38-6GXL motors (30-35oz) and you'll be +/- 100oz on the pad. Good luck on your cert flight!
 
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Yes I figured out pretty quickly that if I did my light metering and set for "correct" exposure the pics would all end up over-exposed from the extra light of the flames. So now what I do is meter on the pad, then bump the shutter speed up until it indicates a full stop under-exposed and shoot at that setting. I can only do so much with them in post because I'm shooting jpegs, the D7000 is not a pro-level camera so the buffer can't really handle continuous RAW for long and I want to maximize my fps.

Edit: I don't know if I described that very well, I don't think the fire is so bright that it illuminates and over-exposes the entire scene (the background would still be correctly exposed) it's that at "correct" ambient metering the flames/highlights are completely blown out.



I know how you feel, I used to shoot a lot with an SLR back in the film days too, but then when things went digital I spent most of the last 10-12 years with just point-and-shoot cameras. What finally pushed me into a D-SLR a couple years ago was having a kid. But this is a great time to get back into photography, digital imaging technology has finally equalled and even surpassed what you could do with film. If size and weight are a concern for backpacking etc just have a look at what's going on with mirrorless cameras, you can get incredible images with very small kit these days. Check out: https://www.sansmirror.com/

Your Super DX3 and my HyperLOC 300 weigh in about the same. And they're nearly the same length but mine is an inch thinner so doesn't need any nose weight (I'm about three calibers stable) but I do have a Garmin GPS up front which is about the same as your bird shot ~5oz. Add one of your Pro38-6GXL motors (30-35oz) and you'll be +/- 100oz on the pad. Good luck on your cert flight!

You're correct, .. it comes in at 98oz. OpenRocket gives it a .93 (or .98 ?) cal. When I preform the test, physically, it's less than this. Thanks!
 
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