Aerotech G-Force: A Quick Build Thread

I have been wanting one of these for a long time. Since it's been getting harder to find recently, I bit the bullet and ordered one. Came in the mail yesterday, built it last night.

The large nose cone is soft plastic. The shoulder especially is quite soft.



Assembled the motor mount/stuffer tube. This is an older kit with the wide engine hook instead of an aluminum screw-on retainer. Installed the motor hook, FIN-LOK rings, cooling mesh, plastic baffle, and forward and mid centering rings. Left off the thrust ring and flange, I deem it unnecessary. Will only be using G composite motors and above. Dry fit the fins before gluing the fin rings as spacing is critical.



Glued the screw eye to the bulkhead. Attached the elastic shock cord to the screw eye. Glued the bulkhead to the coupler. Installed the coupler halfway into the upper body tube.



Tied the other end of the shock cord to the screw eye on top of the baffle, and slid the motor mount into the lower body tube from the top. Aligned fin ring channels with the slots on the tube and dry fitted with fins to check for correct placement. Pushed fins into the locking channels. From the rear, filleted the mid centering ring and all fin/body tube joints.



From the rear of the body tube, glued and filleted the aft centering ring.



From the front of the lower body tube, filleted the forward centering ring.



And assembly is (mostly) complete. I left the 1/4" launch lugs off pending a decision on whether to replace them with 1/2" lugs or conformal rail guides. I'm leaning towards the rail guides for aesthetic reasons. Reviews have said that due to this rocket's weight and slow lift off the standard 1/4" rod would not be stiff enough, and you would need at least 8 feet of launch guidance.



Comments: While I have always used epoxy for my mid power builds, the instructions offer medium CA as the adhesive of choice, with 5 to 15 minute epoxy as an alternative. I used the CA for this build. Any opinions, pro or con? I have heard that CA gets brittle over time. Does that mean weaker too?

This design uses the coupler as a 6" recovery laundry compartment, leaving a huge amount of space in the forward payload area. Lots of options for the use of this space in the future, so instead of gluing the nose cone in place I snug fit it with masking tape. Will be using a JLCR for now. What's good about this kit is the integral strength thru the fin locking mechanism. Plus no wood to fill. Also, even with a G motor, max. alt. is only 6-700'. Perfect for our field.

Will be finishing this over the next few days, depending on humidity, etc. Will post a picture of the finished model. Laters, gators.

I run both 1/4” lugs and rail guides on my GForce. I’ve never had a issue with launching it off my 1/4” rod using G76 reloads. I do use the rail launcher when I step up to the 29/180 case and push it a bit harder.
Only issue I had was failures to separate when the ejection charge went off. After a couple times and some damage I switched it to traditional nose cone eject to remedy the problem.

My AT rockets were all built with CA...decided it would be better for a fin to come off, due to hard hit, rather than break if epoxy used. Had it happen 2x fin popped right out to be glued back. No other real damage other than paint.

If ya got a coupler laying around, I would advise to glue a section into back of Sumo & G-Force, motor is pretty far up the pipe & that tube will dent on any hard hits......yep how do I know????...lol

I agree with blackjack, a piece of coupler is a must for the aft end. I also built all my Aerotech kits with CA, never had one come apart.

If it were me i would use something other than elastic for the shock cord. Flying g motors it will not last very long.

IndianaSteve said:

Only issue I had was failures to separate when the ejection charge went off. After a couple times and some damage I switched it to traditional nose cone eject to remedy the problem.

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Could it be that the coupler was too tight? I seem to be having the same problem. Might have to sand the shoulder down a bit. Did you extend the stuffer tube when you switched to nose cone eject? Seems like an awfully large volume to pressurize.

blackjack2564 said:

My AT rockets were all built with CA...decided it would be better for a fin to come off, due to hard hit, rather than break if epoxy used. Had it happen 2x fin popped right out to be glued back. No other real damage other than paint.

If ya got a coupler laying around, I would advise to glue a section into back of Sumo, motor is pretty far up the pipe & that tube will dent on any hard hits......yep how do I know????...lol

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rcktnut said:

I agree with blackjack, a piece of coupler is a must for the aft end. I also built all my Aerotech kits with CA, never had one come apart.

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Thanks guys, nice to hear you've had good results with the CA. I've seen that aft coupler technique used in some TLP kits as well.

crossfire said:

If it were me i would use something other than elastic for the shock cord. Flying g motors it will not last very long.

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The nice thing about a large diameter rocket is that you can reach in and cut out anything that's broken or worn. For the future what would you recommend: I have some thin steel wire cable leader, some 1/2" flat nylon, and some heavy duty braided thick Kevlar cord. Any preferences, and why?

kuririn said:

Could it be that the coupler was too tight? I seem to be having the same problem. Might have to sand the shoulder down a bit..

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Much simpler to just peel the glassine layer off the coupler, then use CA or thinned epoxy to coat the coupler and sand smooth. It'll slip in & out like a silk glove. I had same problem
You peel the top layer off of reload liners when they are too tight. Sanding takes too long & makes a mess.
I crashed it and my Sumo...so this is made up with all the parts..LOl Only other change I made was ditching the elastic & using 12 ft of tubular nylon.



I left the motor hook off mine, so I could fly it on 29mm 180 & 240 cases. Did my L-1 with it

kuririn said:

Could it be that the coupler was too tight? I seem to be having the same problem. Might have to sand the shoulder down a bit. Did you extend the stuffer tube when you switched to nose cone eject? Seems like an awfully large volume to pressurize.





Thanks guys, nice to hear you've had good results with the CA. I've seen that aft coupler technique used in some TLP kits as well.



The nice thing about a large diameter rocket is that you can reach in and cut out anything that's broken or worn. For the future what would you recommend: I have some thin steel wire cable leader, some 1/2" flat nylon, and some heavy duty braided thick Kevlar cord. Any preferences, and why?

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I actually extended the motor mount 12” and put in a bulk head to keep the area that needs pressurized down and it works great.
I actually sanded my coupler down and put a thin layer of CA on it and would powder it and sometimes it would still not separate. Seems like that is the biggest issue with the G force.

I miss my G-Force. Had more flights on it than other rocket I've owned. Nice build.

I had a G-Force for what I intended to be my L1 rocket. On it's maiden flight with a G64 it the ejection charge blew but not enough to separate the two halves, which lead to non-repairable damage. Earlier this year a member of my club had a similar issue with his, but he was able to repair his and fly again. My theory is due to the size and relatively lightweight construction, the rocket flexes in flight and binds the coupler. I've advised my friend when flying Hobbyline motors use as much ejection powder as can be put into the cap, not just what is provided. I'd normally recommend a ground test to confirm how much ejection powder works, but in this case it wouldn't duplicate flight conditions.

Howie said:

I had a G-Force for what I intended to be my L1 rocket. On it's maiden flight with a G64 it the ejection charge blew but not enough to separate the two halves, which lead to non-repairable damage. Earlier this year a member of my club had a similar issue with his, but he was able to repair his and fly again. My theory is due to the size and relatively lightweight construction, the rocket flexes in flight and binds the coupler. I've advised my friend when flying Hobbyline motors use as much ejection powder as can be put into the cap, not just what is provided. I'd normally recommend a ground test to confirm how much ejection powder works, but in this case it wouldn't duplicate flight conditions.

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I've been observing the G-Force for a number of years and I agree, it is a marginal rocket on AT Hobbyline G motors. There is not enough ejection powder to ensure a sufficient ejection. I've seen them where the nose cone does not come off, and where the nose cone comes off but the chute doesn't leave the BT. My personal opinion; the G-Force should only be flown on HPR motors with their much larger ejection charges. YMMV

I always flew mine on AT 29/40-120 G motors with no trouble.

Bat-mite said:

I always flew mine on AT 29/40-120 G motors with no trouble.

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You were doing something right then. I've seen more G-Forces land hard or lawndart than any other type of rocket. Saw one go through a windshield on a pickup. Many times the nose cone comes off, but the chute didn't come out and unfortunately, if it doesn't come out at deployment, it probably won't come out on the way down. I think packing all the cord in first and putting the chute on top so it gets pulled out when the cord is pulled out and stretched helps a lot.

Did the G-Force come with the AT baffle? Did you use it?

I did use the baffle. But the way the G-Force is designed, it is supposed to break at the center, not at the NC. My nose was glued in, and the rocket separated at the coupler midway down the AF.

I recently purchased an old stock G-Force (Instruction date stamp 2001!) which I plan on bashing out to a 38mm mmt and using a piston in the recovery system. (7mm ply centering rings and ditch the baffle system, Kevlar bridle/shock cord for the recovery). (I've done the same for a Mirage and plan to adapt it for a 29mm Rattworks hybrid.)
I noticed the stock mmt is very long going all the way up to the bulkhead in the coupler. If it's not built as instructed and a larger volume for the ejection charge is resultant then I imagine the problems with ejection mentioned above will more than likely occur.
I'll still use 29/40-120 motors in the local field but up it to 38's at the high power site. Will have to run it through rocksim to see if any nosecone weight is advised. Rivets to hold nosecone so a data package can be used.
Cheers

Old thread but im getting ready to plan out my G-Force build. How do the stock centering rings they give you hold up?? I'm debating on having plywood rings made but I might not if the stock ones hold up..Thank you!!