Aerotech G-Force Deployment Options Answered and L1 Success

[BravoWhiskey]

Hello fellow rocketeers,

Last summer I returned to model rockets after a 35 year break. At first the interest was kindled by my 10 year old grandson. That interest has grown into a full-on obsession and now I have built and launched over 20 rockets ranging from mini engines to G size rockets.

I am now building an AT G-Force for the sole intent of obtaining my L1 certification. I've built the motor mount/fin can with 15 and 30 minute epoxy so I believe that part of the rocket will withstand either an H128 or H182 thrust and acceleration.

I am conflicted as to whether to have the rocket separate in the middle as designed or have the nose cone deploy alone. I have removed the labyrinth from the end cap at the top of the motor tube and so I won't be using the mesh. I'll be using a 12X12 Nomex blanket for chute protection.

Arguments for each side are:
Nose Cone deploy:
1. I can use my Jolly Logic Chute Deployment device without subjecting it to an excessive amount of heat and contamination from the ejection charge.
2. The nose cone slips into the body tube much easier than the paper to paper of the body tube to coupler fitment. I can adjust the slip much more precisely.

Break in the middle:
1. The ejection charge doesn't need to fill as large of a cavity to make the separation.
2. When the rocket lands it will have its weight split over two pieces and won't hit so hard on the ground.

I would love to hear from those who have used these deployment options - or anything else for that matter and get first-hand information so I can make the right decision.

Any suggestions are greatly appreciated. Thanks in advance.

 

[4kids49]

The mid section separation design works fine. The coupler and body tube need to be sanded until a proper fit is obtained. If you are motivated to change the design, go for it. I have an older G-Force and it is not built for high power. I got rid of the mesh, but kept the baffle. I use a kevlar pad from Giant Leap Rocketry. The older G-Forces have a metal hook for motor retention. Does yours have this, or did AT change to a more modern motor retention? The problem with the hook is that it quickly limits your motor length. I don't think any high power motor will fit with that hook.

 

[BravoWhiskey]

Thanks for your reply Chris. AT changed and mine has the new threaded aluminum motor retainer.

 

[ThirstyBarbarian]

I have a G-Force, and it is one of my most flown rockets. I fly it at almost every launch. It flies great on H motors and will make a great L1 rocket for you. I built mine to break in the middle at the coupler as designed. I kept the plastic baffle piece at the forward end of the motor tube where the screw eye for the shock cord is mounted, but I did not use the cooling mesh, or the motor hook. I use a nomex blanket. It has never failed to separate properly. I did have one recovery failure that was due to the chute not opening properly, but the rocket did separate properly, so I consider that a fluke.

The coupler can be prone to binding, and tightness can vary depending on things like temperature, moisture, dirt, etc. The cardboard-to-cardboard surfaces are probably not ideal. To make it slide more easily, I coated the inside of the lower part of the recovery bay with thin CA, and then I sanded the hardened surface smooth. That helped a lot. I also coated the rim of the coupler and rim of the lower recovery bay with CA and sanded those to a slight bevel. The hardened surfaces are less prone to fraying, and the bevel helps to get the the coupler inserted into the bay when prepping the rocket.

I also have used lubricants to help it slide together. One time I used the last bit of a can of fabric-safe spray-on silicone lubricant, and that made it incredibly slippery! I actually had to use a small square of masking tape to hold the rocket together before the launch. I ran out of that, so I've also used a bit of baby powder, and that seemed to help. Usually I don't use anything.

Somewhere on the forum there is a thread where I posted pics of how I prep the whole recovery system, but it wasn't one of my threads, and I'm not sure where it is. I'll try to find it later.

My feeling is that even with a few issues with breaking at the coupler, that's better than going the nose cone route. I think the volume of the body tube would be too big to pressurize with a standard ejection charge. Also it's a bit long, so the enitire recovery system will settle to the bottom of that long tube under thrust. I'm not sure the lightweight nose cone will have enough momentum to pull all the recovery gear out on ejection. With large rockets like this, the recovery system is not "blown" out by the ejection charge, like it is with small rockets. It is pulled out by the momentum of the separating sections. So if you decrease the momentum and increase the effort needed to pull out the chute, you might have problems.

Good luck with your cert flight! Also, until certified, the rocket flies great on the Aerotech Single Use G motors it was designed for --- G77, G78, G79, G80. The G40 is good too, but best on a calm day and long launch rail. And speaking of rails, you might want to add rail buttons or glue on some conformal rail guides in place of or in addition to the launch lugs, especially if you want to fly H motors.

 

[Bat-mite]

So, of course, you left out the forward motor block, right?

Are you using the baffle/cooling mesh? If so, then you don't need to worry about ejection gasses fouling your chute release. If you go middle separation, make sure the unepoxied part of the coupler is longer than the epoxied part.

Good luck!

 

[BravoWhiskey]

So, of course, you left out the forward motor block, right?

Are you using the baffle/cooling mesh? If so, then you don't need to worry about ejection gasses fouling your chute release. If you go middle separation, make sure the unepoxied part of the coupler is longer than the epoxied part.

Good luck!

I removed the baffle and cooling mesh based on information I found searching the forum. So I'm using Nomex for the chute protection. Yes, I left out the forward motor block since this one came with the motor retainer.

 

[ThirstyBarbarian]

Here is the link to the post about how I set up my recovery system https://www.rocketryforum.com/showt...CE-LAUNCH-PIC-and-CRASH&p=1411172#post1411172. That whole thread has some good info about G-Force issues and setup options. I'm still setting up my recovery system basically the same way. I have added an addition small patch of nomex that goes on to the recovery harness at the very aft end right above the screw eye to help protect the end of the harness that's so close to the ejection charge.

My last flight I used a Chute Release and it worked great! I folded the chute with the shroud lines inside, and put the Chute Release on around the chute. Then wrapped all of it in the nomex burrito. The chute realease is protected inside the burrito with the chute. Some put the Chute Release around the whole burrito, but then it is unprotected.

 

[ThirstyBarbarian]

When you say you left out the baffle, are you talking about the small plastic baffle piece where the screw eye for the recovery harness is attached? How are you attaching the harness? Did to put an eyebolt in the forward centering ring?

 

[BravoWhiskey]

When you say you left out the baffle, are you talking about the small plastic baffle piece where the screw eye for the recovery harness is attached? How are you attaching the harness? Did to put an eyebolt in the forward centering ring?

I cut the baffle out of the forward plastic fitting. I used the rest of the fitting for centering and strength purposes. I drilled a hole in the forward CR and installed the screw eye through it. I also have a 1500# Kevlar harness hoping it will withstand the heat.

 

[ThirstyBarbarian]

I cut the baffle out of the forward plastic fitting. I used the rest of the fitting for centering and strength purposes. I drilled a hole in the forward CR and installed the screw eye through it. I also have a 1500# Kevlar harness hoping it will withstand the heat.

That sounds good. I was thinking the baffle piece did more than just act as a baffle, so it's good you kept the rest of the fitting. The kevlar should be good.

 

[BravoWhiskey]

Thank you for the link TB. Those photos are a big help. And thank you all for the information.

 

[ThirstyBarbarian]

Thank you for the link TB. Those photos are a big help. And thank you all for the information.

You are welcome. Good luck with your project, and keep us posted!

 

[Flyrockets]

One more suggestion for you. Buy an extra coupler and reinforce the base of the lower body tube. This is the one spot on the rocket that gets beat up. Annoying if you spend time on the finish.

Have fun and good luck!

 

[Coop]

Mine still has the cooling mesh because... figured I'd give it a go. The bulkhead that was designed to be in the coupler is in the cut-off base of the nose. The coupler is still functional: permits the rocket to be broken-down into chunks friendly to small import vehicle's trunks. It's pinned in place prior to launch. Ejection charge is typically agumented to a solid 2.0g prior to flight.

I like using it for testing because of the cheap motors, quick prep, large recovery compartment (which can hold one MASSIVE streamer), and if I smash it, no big deal to repair or replace. I never installed the motor block or clippie dodad--built it with a screw-on retainer and called it good. Still think it should have a 38mm hole... if I destroy the booster, I'll probably rebuild it with a 38.


Later!

--Coop

 

[Lowpuller]

I built mine dual deploy, there is a build thread on TRF, I'd post the link if I knew how.

 

[KenRico]

I like the blue tube coupler with this rocket..

And they are right the bottom edge takes a beating on landing..sleeving it or fiberglass will help immensely.

Kenny

 

[BravoWhiskey]

Many thanks to all who answered my questions. My Level 1 flight was perfect.


Also, thanks to Rick Barnes for the awesome photos.

 

[Steve Shannon]

Congratulations and welcome to high power!


Steve Shannon

 

[Crash-n-Burn]

Interesting launch pad, it doesn't appear to have a blast deflector. Congrats on the cert!

 

[ThirstyBarbarian]

Well done! Congratulations!

 

[Bat-mite]

Congrats!

 

[ozwald]

Great job. Congratulations on your certification

 

[Coop]

Woohoo! Congratulations! You have any data on the flight?


Later!

--Coop

 

[BravoWhiskey]

Woohoo! Congratulations! You have any data on the flight?


Later!

--Coop

Aerotech H182 drilled to 8 second delay.

Rocksim:
Maximum acceleration:Vertical (y): 432.037 Ft./s/s
Maximum velocity:Vertical (y): 471.9390 ft/s
Maximum altitude: 2099.02887 Ft.

 

[Coop]

Nice! What kind of altitude did you get out of that?


Ooops--I saw the specs at the end... I glazed over it as part of a signature line. Mea cupa.

2,000 feet is a good respectable L1 shot. Very well done!


Later!

--Coop

 

[Lowpuller]

Congrats!

 

[Flyrockets]

Congratulations!

 

[KenRico]

Great flight , but to be E P I C you have to hit 2,100 feet ..

Well done and congratulations

Kenny

 

[MikeT]

Many thanks to all who answered my questions. My Level 1 flight was perfect.

View attachment 309085 View attachment 309086 View attachment 309087 View attachment 309088
Also, thanks to Rick Barnes for the awesome photos.

Great I seriously thinking of following your lead for my Level 1.

Mike

 

[tcomfort]

Brilliant! The flight was picture-perfect the whole way through--straight up, lots of red flame, ejection at apogee, soft landing, not too far away. Tons of prep, research, questions, taking it slowly, all paid off beautifully. Nice job!!