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JAL3

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Tomorrow will hopefully be the maiden flight of my Mercury Redstone from Sheri's Hot Rockets. The recommended motor is a G77-4. I have looked all around town and have been unable to locate such a beast. There is a small chance I will find one in my box tomorrow.

I want to fly it but the closest power combo I can come up with is G80, both AT and RR, but with a 7 second delay. If I do not mount the LES, and I braid the cord to absorb some of the shock, what do y'all think of the possibilities.

Also, my MPR, HPR experience is limited and I don't have as good a feel for these motor as I do the lighter stuff. My field is fairly small. What are the opinions out there for something in the F60-5 range?

I eagerly await your opinions as I try to prep for in the morning.
 

troj

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First, use rubber bands, don't braid the cord.

The G77 reload and G77 SU are both fairly similar, and the G80 has a similar average thrust, although the total is 1/3 again higher. On a small field, that may bite you.

In terms of the F60, without knowing much about what the rocket weighs, it's hard to do much more than a gut feel. You're probably okay, but I don't know.

-Kevin
 

JAL3

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First, use rubber bands, don't braid the cord.

The G77 reload and G77 SU are both fairly similar, and the G80 has a similar average thrust, although the total is 1/3 again higher. On a small field, that may bite you.

In terms of the F60, without knowing much about what the rocket weighs, it's hard to do much more than a gut feel. You're probably okay, but I don't know.

-Kevin
Thanks for the input. I want to make sure I understand. When you say to use rubber bands, you're talkign about gathering the coils and then applying some bands to hold them together until deployemnt, with the assumption that they will break when needed?

I did read your post elsewhere about deployment bags and want to learn more about them. In this case there is the time factor and by doubts about having the room for something like that on this rocket. I am thinking in those terms for the Cosmodrome Nike Apache.

I guess my big question about the G motors is in terms of the delay. If I leave the LES off to prevent shearing, I wonder if 7 secs will still be way too long for the resin capsule and body.

If I had some "3" second delays for a high end F, I would probably chance that first to guage how it goes but I have the feeling that on an F the 5 sec will be too long. The rocket and the capsule seem heavy to me.
 

DAllen

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I would get my hands on a 29/40-120 case if I were you. The G64-4 motor would work just fine as an alternative. At 119 NS total thrust it is not far off the 109 NS of the SU G77.

Methinks that if a G77-4 is recommended a F60-5 is a uber-bad idea. It has 3/4 of the total thrust (75 NS) with a second longer delay and with the industry standard of plus or minus 20% on the delay times your rocket could easily be on or close to the ground before the charge goes off. If there was a way to drill the delay that would be one thing but it is SU so that ain't gonna work.

At $130 for that kit ( :y: ) I'd wait until I could get the right motor for it before flying.

-Dave
 
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BsSmith

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Don't use an Aerotech G80-7 unless it is dead calm.

My Gemini reccomends using the same motors as yours (only doubled up) and the G80s put a zipper in it. Your Redstone is lighter so you probably won't have as much of a zipper, but it will most likely deploy after apogee.

If you are using a 7 second delay, put the capsule and body on seperate chutes and find a way to make it so the parachutes don't snap open.
 

JAL3

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I thank all for the advice. I'm taking the rocket out in the morning in hopes of a swap getting what I need but right now even that looks iffy.

The recommended chute is between 32 nad 36 inches. I had K&S make up a nice hemispherical one with orange and white gores. I just realized while packing up my stuff that I very well may not be able to get it to fit. If it does fit, It's going to be tight.

I'm going to re-examine in daylight tomorrow and hope for a miracle.
 

troj

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With rubber bands, the easiest way to describe it is to S-fold the cord harness back and forth, and put light rubber bands on the ends. The ones from braces will work, if you have those available, and they'll fit.

Otherwise, something small and light weight.

For your parachute you're having a hard time fitting, a deployment bag may be just the ticket.

Based on what you're encountering, it's sounding like waiting to fly another day may be the best route.

-Kevin
 

cjl

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The AT G80-7 might work OK - it has significantly more total impulse than the G77, and could be about right. The RoadRunner would be more questionable - it has something like 20Ns less than the AT, and would probably be pretty late of a deployment.
 

shreadvector

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The *NEW* 137 Newton-Second total-impulse G80 does not come in a delay shorter than 7 seconds BECAUSE (as Gary has explained) a maximum weight Model Rocket (3.3. pounds) will need 7 seconds of delay time after being accelerated to great speed and altitude by the most powerful Model Rocket motor available on Earth. :D

If you have some other heavy rocket that is unusually draggy and really needs a shorter delay, then use the RMS and a 4 second delay.
 

Igotnothing

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The *NEW* 137 Newton-Second total-impulse G80 does not come in a delay shorter than 7 seconds BECAUSE (as Gary has explained) a maximum weight Model Rocket (3.3. pounds) will need 7 seconds of delay time after being accelerated to great speed and altitude by the most powerful Model Rocket motor available on Earth. :D

If you have some other heavy rocket that is unusually draggy and really needs a shorter delay, then use the RMS and a 4 second delay.
And still no pics!
 
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