Aeroforce G-Force 4

[1974_Trident]

Well, I have to start out by thanking everybody who has posted in this and all of my other threads, as well as anybody who contributed to other build threads I learned from. Today I flew my G-Force and I am going to break for dinner now and come back to post pics. But I don't want to leave you in too much suspense so I will say that my next G-Force will have dual parachutes. The Aeropack retainer looks salvageable and the 29/40-120 casing is intact.

 

[1974_Trident]

Well, the first photo tells the story. Nearly total destruction. The only salvageable parts are the parachute/shock cord, Aeropack retainer, and engine casing. All of which will go into my next G-Force.

Analysis began with a brief study of the rocket right on the crash site. It would have been a lawn dart had it crashed on a lawn but I didn't get that lucky. Only airframe damage was crash related. No sign of engine malfunction. Airframe damage was a combination of telescoping and buckling suggesting longitudinal compression.

Two fins broke approximately mid span. Fin section of the airframe is structurally intact as are the fillets. Motor mount tube is still straight without signs of swelling.

Cooling mesh was compressed tightly against the forward end of the motor tube assembly. How much of this compression is caused by rapid deceleration is uncertain but likely almost all of it. The inside of the motor mount tube has a coating of ejection charge residue very pronounced at the point closest to the engine casing and very little near the baffle. The cooling mesh itself has an even light fouling of ejection reside on the aft end and is clean on the front end. The cooling mesh worked properly.

Disassembly of the engine casing revealed no remarkable findings although I will defer to the experience of the forum members. This is my first reload and I do not know what a spent engine should really look like. Is the charring on the aft end of the propellant liner more than I should have found? Is there an incidental o-ring failure here? I did disassemble and reassemble this end of the engine to replace a defective igniter last week and I may have upset the o-ring. The o-rings, however, look good with grease still on the protected areas and a coat of propellant residue on the side facing the propellant. I really feel like these o-rings could be reused if their job was not so important. I did find a sign of a little pin hole in the side of the propellant liner which itself is simply incidental. The delay liner has a nice even coating of delay residue and no signs that there was any propellant gases leaking around the outside of the liner. Delay o-ring looks good as new save for a nice light coating of reside. There is no sign of breach around the delay spacer.

 

[1974_Trident]

After flipping through the pictures of my G-Force flight the answer was absolutely stark: IN the first photo taken at apogee it is evident that the ejection charge has fired. A closer look at the rocket at this point shows that the fore and aft sections have nearly completely separated (evidenced by the band of white body tube coupler visible between the orange front half and the mostly black rear half) and are held together by a miniscule amount of body tube coupler. Recall I had a concern about this tight fit when I first built the rocket and I did some sanding inside the aft body tube to loosen the fit. Next time I will aim for a looser fit yet. Also on my list of things to do is pick up a pound of FFFFg at the local gun shop. A quarter of a gram more may have been enough to complete the deployment.

Note, in the photo taken just before apogee there is no visible separation of the body tubes.

 

[terryg]

Yep, not enough black power for the volume and conditions. The standard method to measure the proper fit of couplers and nosecones is to hold the rocket by the nose and it should stay in place. Then if you shake it, it should start to separate. This is a judgment call and depends on the rocket and motor combination. Ones with big draggy fins are most likely to drag separate (especially when flown with high impulse motors) and need a tighter fit. Getting fights with a lot of flame and noise is what is so addicting about this hobby. Find a club in your area and go their launch and enjoy. Fly a little , watch a lot!

 

[Handeman]

Very sorry to hear about your G-Force. Unfortunately, your G-Force is not the first one I've seen that happen to. The interior volume is at the upper end of what the included ejection charges on Hobbyline motors will handle. The other common scenario is the nose cone pops off but the chute never leaves the tube and it falls flat. Things are usually repairable then.

I have a BD Thug that is also 4 diameter. It doesn't have quite the volume of the G-Force, but I always add a 1/4 g of BP to the ejection charges whenever I fly it on a Hobbyline because I've had several flights where the nose cone popped, but not hard enough to pull the chute out.

 

[exprditer789]

Whats the height of this rocket??Alex

 

[1974_Trident]

Whats the height of this rocket??Alex

Rocksim said approximately 500 feet. My visual estimate says about 500 feet.

 

[exprditer789]

Sorry I ment how tall is this rocket.Not how high it went.No problem my fault.Alex

 

[1974_Trident]

Sorry, I misunderstood you. The G-Force is 60 inches (152.4mm) tall.

 

[exprditer789]

Thanks! That is a nice size rocket.Alex

 

[Johnny1Eye]

Built as per the instructions, there is very little volume. It separates at the coupler.

The fit of the coupler is not just tight. It is flat TOO BIG. Sanding it down, or peeling off enough layers to make it fit, would make for a very thin, and weak coupler, it is thin as it is.

I am not at all impressed with the G-force rocket. It is nothing like the tough rockets I have seen from AT in the past. The nosecone is paper thin! A coupler that will not even fit, unless you peel off half of the paper, of an allready thin tube?? Come on now...

 

[EMiR]

yes I found the Aerotech G-force rockets tend not to deploy, with SU motors.

and seen a many picture of G-Forces exactly like yours, so much so, I think you could have a competition, with who has the most pancaked G-Force picture.

I've had 2 now, and both failed at deploying. and both built to instructions.

the 2nd one I built, I had the same thought about making the joiner a loser fit, but it made no diference. I even did the blow test on the ground, and with the slightest of breath, it seperated, but in the air it did not.

I believe its because the bulkhead is on the topside of the joiner, and the ejection gas pushes against the joiner, causing it to cease.
I think this because the First launch I saw the puff of smoke came out of the engine on ejection, which tells me that it was over pressurised and forced it out of the back of the motor..

Whats the bet the its the plastic baffle holder, forcing the gase sidewards against the joiner walls.

If I was to build another,I would lower the forward CR down the BT a few inches, get rid of the mesh and plastic holder, move the Bulkhead to the bottom the joiner.

But then again if I was to build another I would scratch bulld it, I given up on aerotech rockets.

 

[rcktnut]

1974 Trident,

You had a very nice looking G Force there!! Very sorry to see the results of your first flight on it. I bought mine 13 years ago, second kit after becoming a BAR, and built it stock per instructions. I used med. CA no epoxy, no fillets. It weighs 37oz. (1048 gr.) without motor.

I still have it today, after countless flights with SU as well as reloadable motors (29-40/120). I've never had a problem with ejection charges, never added any BP, used what came with the reload.

The way it sounds, the new kits seem to have couplers supplied with them that do not fit properly. That's just not right, a person should not have to peel off layers of paper or sand the heck out of them to get them to fit properly. My coupler was a perfect fit, did not have to do anything to it.

When standing upright I can lift the upper section off of it and the lower section stays on the floor. That's how "loose" it should be. That's without a motor in it. Once it is together and with a motor in place I can pick it up and shake it very hard for awhile with out separation. I call that "air lock".

With this kits weight and building it stock, you don't have to worry about drag separation. Make sure that it separates very easily (without a motor in place). My G Force is my small field favorite. Great flier!!

 

[1974_Trident]

Wow. I can't thank you guys enough for your input. What I am seeing here is two classes of G-Force owners; Those with many successful flights and those with few or no successful flights on their G-Force. Those who have many successful flights on their G-Force also had their G-force for a long time. Could it be that Aerotech has changed the materials they supply with their rockets sometime in the past five to ten years?

And I agree with the several of you that the coupler is not just a wee bit tight but the wrong coupler, perhaps a metric coupler on an inch standard body tube. Who knows? When I buy a model rocket kit I expect to have to fine tune certain components (sand airfoil edges on balsa fins, scrape casting flash off of nose cones and even fit the body couplers a little). What I encountered on my G-Force was just ridiculous. I had sanded the inside of the aft body tube to the point where I was losing confidence in its strength and it still felt tighter than I was comfortable with. I should have listened to myself and augmented the ejection charge. I guess this is what is meant by learning from experience.

Anyway, I am about to place my next rocket order for the whole family with the exception of my wife. She picked up an Estes Guardian for herself at Michael's the other day with a 50% off coupon. And, EMiR, thank you for the recommendation about putting the bulkhead on the aft end of the coupler. Along with my order I will buy an extra bulkhead (what am I thinking, I already have another bulkhead, I just have to Dremel the epoxy off) and set it up so it threads over the shock cord and just acts as a cap to prevent ejection charge gasses from entering the parachute bay. May require a bit of modification of the kit, I'll have to see.

As far as epoxy and fillets; I do recognize that I overbuilt my G-Force at the expense of altitude but I have a reason for doing so. I want the rocket to survive the high power 29mm loads when I am one day certified. I also want to practice filleting and such reinforcement of my rockets so when I am building level three type rockets I will already be an old hand at these techniques. Also, with nice 1/4" fillets on all inside and outside fin/body tube joints I still only used 4oz. of epoxy more than the instructions recommend. It was my paint which added the majority of weight (Almost a pound) in excess of published kit weight. Recall, I painted and repainted this rocket a few times before I got it right. My next G-Force will only be painted once.

 

[rcktnut]

And, EMiR, thank you for the recommendation about putting the bulkhead on the aft end of the coupler.

They must have changed the design. In mine all that I have for the chute and shock cord is 6 1/2 inches. That would be the length of the coupler plus 1/2 in. to the MMT forward centering ring. I have 8 Aerotech kits all older, and have had no problems with any of them. I like them all!! Like I said there should be no reason why a person should have to sand the heck out of or peel paper off of a coupler for a decent fit. Aerotech should check their parts fits before kitting them up. They all used to be good.

 

[1974_Trident]

...In mine all that I have for the chute and shock cord is 6 1/2 inches. That would be the length of the coupler plus 1/2 in. to the MMT forward centering ring...

This is still the case. what I believe EMiR is saying is that the ejection charge gasses are expanding the coupler making an already tight fit even tighter for a critical fraction of a second. I am thinking of creating a "Piston" type ejection system by having a second bulk head loosely fit over the aft end of the coupler with maybe five feet of shock cord between this bulkhead and forward centering ring and the rest of the shock cord and 'chute(s) inside the coupler. The shock cord would be threaded through the center of the additional bulkhead or secured through the bulkhead by a double ended eyebolt/eyenut arrangement.

This is starting to sound like too complicated a solution to such a simple problem. Certainly more complicated than adding an additional 1/4g of FFFFg.

 

[rcktnut]

I would get the correct fit with the coupler and add a bit more BP if it makes you feel better, isn't going to hurt. Your other "piston" type solution scares me!!!! I want to see you posting lots of pictures of nice successful flights!!!!

 

[1974_Trident]

... Your other "piston" type solution scares me!!!! ...

Yeah, I was unsure of that one myself. Thanks for your input.

 

[terryg]

I did a L1 certification for someone using a Gforce at our local club and it flew fine. However I have only seen it fly on high power 29 mm motors which have more black power then the standard hobby line reloads. One other thing to consider is the conditions you are launching in. Us desert rats would not even go outside at the temperature you are launching at. Things fit tighter, chutes are stiffer and plastics are more brittle. One other thing to consider is the question of whether to replace the GForce or not. I have always considered it overpriced for what it is. Madcow rockets have some great midpower kits which are more in the mainstream for rocket designs.

www.madcowrocketry.com

I seldom build kits anymore and prefer to scratch build from stock parts.

https://shop.rocketsbymelissa.com/main.sc

 

[Rocketeer41]

Trident, I like all your posts on this thread.:cyclops: I wish to have a G-Force too. Then it will go ffffffffffgggggg.

 

[Luv2launch]

This is still the case. what I believe EMiR is saying is that the ejection charge gasses are expanding the coupler making an already tight fit even tighter for a critical fraction of a second. I am thinking of creating a "Piston" type ejection system by having a second bulk head loosely fit over the aft end of the coupler with maybe five feet of shock cord between this bulkhead and forward centering ring and the rest of the shock cord and 'chute(s) inside the coupler. The shock cord would be threaded through the center of the additional bulkhead or secured through the bulkhead by a double ended eyebolt/eyenut arrangement.

This is starting to sound like too complicated a solution to such a simple problem. Certainly more complicated than adding an additional 1/4g of FFFFg.

My take on this is that the baffle system of a G-Force works more like a cold air piston its not all the ejection charge gases that push the payload section off its the cold air inside the tube that the ejection gases are displacing that is pushing the payload bay off.

 

[Luv2launch]

This is still the case. what I believe EMiR is saying is that the ejection charge gasses are expanding the coupler making an already tight fit even tighter for a critical fraction of a second. I am thinking of creating a "Piston" type ejection system by having a second bulk head loosely fit over the aft end of the coupler with maybe five feet of shock cord between this bulkhead and forward centering ring and the rest of the shock cord and 'chute(s) inside the coupler. The shock cord would be threaded through the center of the additional bulkhead or secured through the bulkhead by a double ended eyebolt/eyenut arrangement.

This is starting to sound like too complicated a solution to such a simple problem. Certainly more complicated than adding an additional 1/4g of FFFFg.

With the way my G-Force is built with the bulk head on top of the coupler adding one to the bottom of it would make it impossoble to pack the chute and shock cord into it.Besides with the bulkhead on the top it gives the pressure something to push against having filled up the coupler below it.

 

[Boosterdude]

The baffle system on the G-Force (and all AeroTech kits) works fine if assembled and used correctly.
I, also, cut a piece of tube coupler and glued it into the aft end of the rocket up to the aft centering ring. This doubled the thickness of the body tube as the model lands on the tube, not the fins.

Initiator and I are on the same page with his thought listed above.

I built a stock G Force only changing a few things. I used rail buttons instead of the plastic launch lugs included in the kit. I also added a piece of coupler to the rear end of the rocket to double the thickness. Since it always lands on the rear end, the double thickness really makes it almost damage proof.

I also bought a stiffy coupler from LOC and installed it inside the the stock coupler where the rocket separates. This really strengthens the coupler and keeps it from denting on landing as well. You can also remove the outer paper layer of the stock coupler if the fit is too tight and not have to worry about a loss of strength.

I fly mine about every month and it holds up well. The stock baffle system works great and makes preparing the rocket a simple task. I also have the stock motor hook which works fine as well.

Mine flies arrow straight everytime and has been reliable. Doesn't get a lot of altitude, but it's cool because you can clearly see the entire flight. I've used G64, G71, and last weekend it flew twice on G76G. I think you will enjoy the G-Force!

John

 

[quickburst]

I'm chiming in late here. The G Force Kit is best suited to a 38mm motor mount. this way you can fly 29 and 38mm mtors.

Wider selection and much cooler flights.

 

[Rocketeer41]

Quickburst, the G-Force only runs on 29mm motor mounts.:roll eyes: Not 38mm motor mounts.:bangpan:

 

[quickburst]

Quickburst, the G-Force only runs on 29mm motor mounts.:roll eyes: Not 38mm motor mounts.:bangpan:

Use a little imagination. Bash the kit. A G Force will fly great on 38mm motors, I've seen it done countless times.

 

[Rocketeer41]

What?:shock:

 

[blackjack2564]

Use a little imagination. Bash the kit. A G Force will fly great on 38mm motors, I've seen it done countless times.

He's right. I had one.Just replaced the centering rings with 38 holes and glued the baffle by using adapter.

Even built it with CA. Flew great till I got one of those "bonus" delays.
Had a video of the flight. The G-80-7 turned out to be a 12 sec delay. It fired after the rocket was a fence post!

You guys are making this way to complicated. I still have my 29 version and love flying it on G-H's. It was hobbled together from a crashed G-force and Sumo.

Just eliminated the motor hook. I tape motors on the Motor tube sticking out.

Peeled a layer off the coupler to make it fit good. No way it was gonna fit the way it came. CA'd the outside and sanded it to fit.
You get used to making stuff fit when building here down South. The humidity swells all paper parts.

Did replace the elastic with 1/2 tubular nylon and put a section of coupler [2in.] in the rear to protect it from hard landings.

Other than that this rocket was built stock, with Ca too. 6yrs old beat to heck, but I love flying it. Build motor, stick it in, go fly!

No extra BP's No eyebolts. No epoxy. It weighs 36oz and handles everything thrown at it!

Here it is on a H-180 medium delay.
Any where from 500ft on G's to 1100-1300 on H's
I did add rail buttons to the other side for flying the larger motors. Sometimes I just wrap an altimeter with newspaper and stuff it in the payload to get height readings. drill small hole in the side of payload for vent

 

[soopirV]

Hi Gang-
Sorry to dig up an old thread, but I too have (well, had) a G-Force that didn't separate on it's maiden voyage. All I have left is the rear part of the rocket, so I plan to rebuild, but it got me frustrated for another reason: every AT rocket I've had that relied on mid-body separation has failed in the exact same way, although not always on the first flight (thankfully!). This includes the Barracuda, the Arreaux, the Mirage and now the G-Force!! In contrast my Strong Arm and Initiator (nose blowers) have never had a problem. I had to wonder why I was giving AT so much money for the kit AND the engines...
I rebuilt the Barracuda, but I skipped the bulkhead and instead switched to nose ejection. I did this after calculating the space in the 'cuda to be less than that of the Initiator. It's flown dozens of times, and is just fine.
Clearly, I'm not able to convert the G-Force to blow the nose (too much chamber space), but can you tell me if there's something fundamentally wrong with my construction technique that I have such terrible luck??
Yes- I did have to sand the couplers in all my mid-body rockets, and yes, they would separate without engine if picked up vertically (kind of a slow separation, but not sticking).
If I build the Arreaux again, I'll do nose-blow. Wish that was possible with the Mirage too.
Oh, FYI- I use only recommended engines, 29mm RMS hardware.

Thanks!!

 

[CF-105]

Use a little imagination. Bash the kit. A G Force will fly great on 38mm motors, I've seen it done countless times.

Especially CTI 38mm motors

I was tempted to put a 54mm in my present G-Force, but figured it would be overkill.