Aeroforce G-Force 4 [Archive] - The Rocketry Forum

1974_Trident

6th December 2009, 02:49 PM

I am planning my first BIG rocket. My Aerotech G-Force 4 should arrive sometime this week along with a Big Bertha, a Der Red Max and a pair of Alphas all for the kids.

I am brand new to re-loadable motors but I have experience handling things that go, "boom." I am considering the Aerotech (or Rouse Tech) 29/40-120 hardware and an assortment of G impulse loads; G64-4, G71-4, G76-4 and I even see possibilities with a G53-5 which seems like it would give a nice slow liftoff for my viewing pleasure. I may even get a few F loads.

For the near future I will be launching at the local school athletic field so I want to keep altitude within reason. Are there any factors other than field size which would limit my target altitude? My New York Sectional shows my launch area is just outside DXR's class D airspace but within Class E airspace with a 700 foot floor. Does this mean I need to keep my flights below 700 feet?

I took a quick look at pictures of kit components of the G-Force 4 and immediately I want to use an engine retainer other than the flimsy little metal hook. I've read a lot on these forums which advocates simply friction retaining my engine. On the Apogee website I saw a nifty looking little engine retainer, the AeroPack, (http://www.apogeerockets.com/retainers.asp) which looks like a really secure device. Has anybody here used one? I see that the G-Force kit also comes with a pot scrubber which promises to cool off ejection charge gasses. I've read nothing favorable about this pot scrubber thingy here and in fact I am under the impression that this device is best left out and its function replaced with wadding. Am I thinking along the right lines? Will I have to add additional protection for the shock cord i.e. Nomex or Kevlar sleeve for the few feet closest to the bulkhead? While I expect to find out for sure when the kit arrives I would like to know if I can build the rocket with a 38mm engine tube and use adapter rings for a 29mm motor. I would like to be able to fly big motors when I am ready although I would be completely content to stick with the impulses available in 29mm format.

H_Rocket

6th December 2009, 03:27 PM

Aeropack retainers are some of the nicest ones there are. There are equivalents that cost a bit less (HAMR by PML and Lock-N-Load) by Wildman). Just make sure you have enough motor tube sticking out to affix it. You can also use the Slimline by Giant Leap.

BTW, the motor hook on an Aerotech kit is many things, and flimsy is not one of them. In fact I often curse at them for being so stiff. That said, I would rather not use them as they also rust.

Initiator001

6th December 2009, 07:18 PM

The motor hook on the AeroTech G-Force kit works fine. As with all motor hooks, I do apply a wrap of masking tape around the hook and motor after motor installation.

The baffle system on the G-Force (and all AeroTech kits) works fine if assembled and used correctly.

I have only flown my G-Force on 'G' motors, not sure if an 'F' would work/be safe.

I modified my G-Force to use two parachutes to bring the upper and lower sections of the rocket down separately. 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.

I think you'll enjoy flying the G-Force.

Handeman

10th December 2009, 04:14 AM

The 29/40-120 cases are great. You will love the load available for it. I fly that case more then anything. I just bought a second case, just so I can fly more often without cleaning. It's a great motor.

If you can build the rocket with a 38mm MMT do it!!! :2: There are a lot of motors available in 29mm, but there are a lot more available when you add 38mm to that. I'm not sure the Aerotech fin mounting will hold up to the larger 38mm motors, but it would be fun to find the limit.

One thing about the G-Force when you fly it on Hobbyline motors. The 4" tube has a lot of volume and sometimes the ejection charge is a little weak for that big of tube. The baffle doesn't help. I've seen several rockets pop the nose cone but not the chute and others where I've heard the ejection charge but the nose cone didn't come off. It ended up about 16" long. An extra 1/4 gram of FFFFg powder in the ejection charge makes it much more of a sure thing.

dpower

10th December 2009, 06:48 PM

I've had no issues with the mesh baffle. I've heard it can get clogged, but I haven't experienced that. After years & many flights, it can eventually rust away. In either case, it can be removed and replaced with 3M or Chore-Boy pads from a hardware store.

1974_Trident

10th December 2009, 09:32 PM

Thank you, everybody, for your input so far. The kit arrived yesterday. After inspection of the components and reading the destructions I have decided that the pot scrubber will stay. Since I am using the Aeropack threaded motor retainer I will not have the engine hook or thrust ring. The pot scrubber will be pretty easy to remove for cleaning. I am going to stick with the 29mm mount, there are enough big motors which will fit. When I want to move up to 38mm I will just have to buy another rocket. I don't think that will be all that terrible.

Along with my G-Force came several other kits for my kids; Big Bertha, Der Red Max and a pair of Alphas. We are going to have a big rocket building family get together this weekend!

Pictures to follow.

Handeman

11th December 2009, 01:57 AM

Sounds like you're going to have a great weekend! :D

Sticking with the 29mm and getting another rocket when you want a 38mm is a great plan. If you're like me, you won't miss the 38mm MMT in the rocket until you get that rocket with the 38mm and fly a few motors in it. They you'll be wishing you could fly those motors in the 29mm rockets you have. I've only flown a couple of 54mm motors in my L2 rocket and already I'm regretting not putting a 75mm MMT in it. Oh well, guess I'll have to build another one too.

terryg

11th December 2009, 02:45 AM

One other mod to consider is to add rail buttons. That way you can fly from both 1/4 inch rods and also from a rail for high power flights. It is a large rocket and the rod whip with the larger high power reloads is significant.

Handeman

11th December 2009, 06:43 PM

1974_Trident

12th December 2009, 01:50 AM

Initiator001

12th December 2009, 02:12 AM

Since we are on the subject, Aerotech recommends a 1/4" launch rod at least 36" long. Without trying I can go to Home Depot and get either 36" or 72" rods. Are there any risks or other disadvantages to using a longer than necessary launch rod?

I flew my G-Force off 5'-6' launch rods.

I would use something longer than 3'.

Handeman

13th December 2009, 04:27 PM

In regards to rail buttons I looked at a few commercially available rail button kits and they look like nothing more than a couple of washers, a spacer, a screw and a T nut. All stuff I can get at a local hardware store. Since I don't have a launch rail yet, I plan on making my own. How wide is the slot supposed to be? I would like to have a rail which is compatible with commercially available components for rockets I will purchase in the future which may come with a rail button. And I would like my G-Force to be compatible with said rail. Instead of T nuts I may use a piece of 1/8" aluminum flat stock drilled and tapped then sanded to match the contour of the inside of the body tube and epoxied in. How far apart should I mount the rail buttons? A lot of pictures I've seen of rockets with rail buttons show the two buttons mounted about 6" or so apart which seems close to me but I am only used to using waxed paper drinking straw launch lugs which are mounted much further apart when a rocket has two.

Since we are on the subject, Aerotech recommends a 1/4" launch rod at least 36" long. Without trying I can go to Home Depot and get either 36" or 72" rods. Are there any risks or other disadvantages to using a longer than necessary launch rod?

You can try to make your own rail if you want, but I wouldn't bother. Most of us launch our larger rockets at club events and the clubs supply the waiver and launch pads. If you want your own pad, you can get the 1010, or Standard rail from McMaster-Carr (http://www.mcmaster.com/#catalog/115/1888/=4wy6xo)or other local vendors. The T-slot is 1/4" wide. The 1515 or Extreme rails have 5/16" wide slots, but you shouldn't need anything that big until you're well into Level 2 rockets.

As for making your own buttons, be aware that some clubs only allow plastic buttons because the metal ones can gouge and wear the rails. You also will have to make sure your homemade buttons fit inside the t-slot. The outside diameter and thickness of the T part is critical to prevent binding. Homemade ones might work great on a homemade rail, but might not work at all when you go to a club launch.

1974_Trident

18th December 2009, 11:19 PM

Anyway, this project has been underway for nearly a week now.

I was delighted to come home and find this nice big box behind the storm door.

1974_Trident

18th December 2009, 11:23 PM

Now the fun begins.

1974_Trident

18th December 2009, 11:33 PM

I didn't like the wood screw eye that came with the kit. I see this screw eye pulling out of the forward bulkhead. While the wood screw may be secure in the baffle I am more comfortable using machine screw eyes and nuts. Next time I'm putting a nice wide fender washer on the bulkhead.

Taking lessons from another build thread I masked off the body for filleting the fins. The destructions that came with the G-force don't mention filleting but I don't see any harm in overbuilding.

I like the way the epoxy makes its own fillets. All I have to do is position the rocket properly and let gravity do the rest. The epoxy seems to have the ideal consistency for the right length of time. A little bit of sanding will clean up any of my imperfections. This is the first time I've used epoxy for building a rocket and I am now hooked.

1974_Trident

18th December 2009, 11:35 PM

And here are some fillets setting.

1974_Trident

18th December 2009, 11:42 PM

While we are here, something has come to my attention and I'm glad now rather than after I've finished painting.

The body tube coupler fit nice and tight into the forward body tube but is way to tight a fit in the rear body tube. In fact there is at least 1mm of interference. I cut a few slits in the end of the coupling tube so it will squeeze down and fit into the rear body tube and even this takes some manhandling. The fit is so tight I an afraid to push the tube all the way together out of fear I might not be able to get them apart. Any suggestions of how I can loosen the fit a little? Can I sand the inside of the rear body tube? Any tried and true tricks of the trade? I am afraid that with such a tight fit the ejection charge may not be enough to deploy the 'chute and the fit may be so tight that the body tube could rupture instead of separate at the coupling.

loopy

19th December 2009, 02:18 AM

Alot of sanding to get the coupler to fit better. Same techniques as with LPR stuff.

Definitely get a 29/40-120 motor. This casing is invaluable for the MPR flyer. The 29/120 casing is another good one with some great G loads.

As for the 38mm stuff - I love my PML Small Endeavour. Awesome design, 38mm. Flies awesome on the same G loads you'd put in the G force, and any H you can throw at it. used it for my level 1, and it was a thing of beauty! I also highly recommend the PML 2" AMRAAM. Perfect mid power rocket.

Rail buttons - look at PML or Newtons 3rd Rocketry for rail buttons. They are insanely cheap, and well worth the money. Flying with clubs is a great way to go with the bigger rockets - they take care of any regulations that need to be dealt with, and the people there can help you with any problems or questions you might have - especially when it comes to building your first reload.

SPeaking of reloads - a 24mm RMS casing is also another must have for the mid power flyer. This casing holds alot of E and F loads that are perfect for things like the Estes Mean Machine, Big Daddy, Prowler...really, any of the larger 24mm kits out there. I build those with a LOC 24mm motor tube (handles the higher heat better), and switch the balsa to basswood, and it's great!

terryg

19th December 2009, 04:13 AM

Aerotech couplers seem to always be too tight. I do not sand them, I just peel of a layer of paper to give an acceptable fit. When glueing in the coupler make sure that is a very easy slide fit. For any glue but epoxy a tight fit will cause it to seize up faster then you would expect and you can get a coupler that is only part way in position. I would not use CA for the coupler (just asking for trouble).

1974_Trident

20th December 2009, 01:38 PM

With regards to the coupling tube; I did use copious amounts of CA to glue it in. I was aware of the potential for it to seize up so I worked really fast. All went as planned. I left the upper and lower body sections coupled over night and that seems to have "Stretched" the fit out a bit, it doesn't seem as tight as it did the day before.

The entire rocket is in primer now and I almost don't want to paint it. It looks quite mean in primer. Maybe stenciling some official looking words or something on it will finish it up. Maybe I will do the black/blue color scheme complete with the included decals. I'll decide when I'm ready to add color.

1974_Trident

29th December 2009, 09:30 PM

So, I decided on color.

For a while I was considering a Cobalt Blue and no other color for the upper half of the rocket. I couldn't find a Cobalt Blue in Krylon so I started to call the auto paint suppliers. In all cases I would need a color code to get a price over the phone and in all cases I was told it would run about $75-100 for a pint!!! You've got to be kidding me! Something about the pigments in Cobalt Blue that makes them so expensive. I am not spending $100 to paint a $95 rocket. Besides I had to drive an hour to the nearest store that carries PPG Duracryl. I already painted the lower half of the rocket in Duracryl Acrylic Lacquer and I wanted a paint for which I would be able to use the same clear coat on the top half of the rocket as on the bottom half. I have a half quart of black Duracryl and Duracryl clear Coat in my garage from when I painted my motorcycle many long years ago.

In short it was becoming to much an exercise in logistics and disposable income to go with Cobalt Blue. I was getting myself ready to settle for a different shade of blue and I was about to go to the hardware store to see what they have. My son pulled into the driveway on his bicycle as I was ready to get into my truck. My son's bike is a very sharp combination of black and Hugger Orange. Something which really appealed to me when I bought his bike a few months ago. I started toying with the idea of painting the front half of the rocket a nice Hugger Orange. I knew the 1970 Pontiac GTO Judge was available in this shade (called Judge Orange). I went online and looked up the paint code for that color on a 1970 Pontiac GTO to bring to an auto paint store.

On our way out we stopped by the local hardware store first just to see what colors they have in stock. There it was in the Ace Hardware store brand of paint (Krylon in the Ace Label for two $$ a can less.) $12 and only fifteen minutes later we were back in my garage.

I have to re-sand a repaint the bottom half of the rocket. I forgot about Duracryl. Re-coat within five hours or after 48 hours. The second coat which I applied after only 20 hours orange peeled. After seeing how well the spray paint handled and finished I am dissuaded from using automotive paint on future builds unless I am craving a really exotic color on a really big rocket.

After applying two coats of the spray paint to the front half of the rocket I see that orange is clearly the right color for the G-Force. I am now considering pin-striping some orange flames down the Lower half of the rocket.

Here is what our current fleet under construction looks like now. We have the G-force in black/orange. Big Bertha and Der Red Max in sand and fill primer. Nothing like the smell of paint fumes in the house while the rockets are atop the boiler to dry.

stickershock23

29th December 2009, 09:35 PM

Trident,

The rocket is looking great... Any True automotive paint is not cheap. especially when you get into colors like the cobalt, pearls etc. a quart of even decent automotive 2 part sandable primer goes for $20. out here OUCH...

anyways I like the black and orange.. Can I set you up with some G-force decals in Orange to something to match? By the way I do custom vinyl decals.. and that rocket SCREAMS for some cool contrasting stripes or something like that.. I can also hook you up with flames for that. I even do Paint masks if you really want to paint them yourself.

Thanks for all the Build details. Thats a great first mid power rocket!

1974_Trident

29th December 2009, 09:58 PM

Well, thank you for recommending your decals, Stickershock. while I haven't committed to such a decision I am considering using the factory supplied Aerotech decals so I can say I followed some of the directions when I built my rocket. As far as pin-striping the flames, I have some pin-striping experience from a youth spent around cars and motorcycles. My wife also worked in a body shop. She was the bookkeeper but was asked to do the more intricate pin-striping when the shop owner found out she was better at it than the guys who went to school for it were. I even have a pattern in mind, the flames on the sleeves of an old Harley Davidson t-shirt which I have, I just need to scan them into my computer and print them out. follow the flames with a roller punch pin pricker thingy and trace the pattern onto the rocket with talcum powder.

I will, however consider decals. Orange "G-Force" decals are sounding quite nice.

1974_Trident

5th January 2010, 02:20 AM

So the top half of the rocket is a nice vibrant shade of orange and the lower half is in primer again. I must say, bad technique with the automotive paint has cost me too much time. Certainly more than the money I thought I was saving by using paint I already have in the garage. I spent more time sanding off the bad paint job than I would have spent on the entire paint phase had I used spray paint from the beginning.

Lesson learned; never wet sand a cardboard tubed rocket. The tube ends absorb the water and get all soft and distorted. I decided to trim about 5/16" off the front tend of the rear half of the rocket. I found that the body tube fits tightly inside a piece of four inch schedule 40 PVC pipe. I was fortunate enough to have a length laying around that still had the factory cut end. With a bit of soap and some gentle persuading I slipped a two inch band of four inch pipe over the end of the rocket and used it as a guide to trim off the boogie dooed end of the tube. Looks like a brand new tube now.

I better get this rocket done really soon. Each day that goes by I get ideas for more complex flame designs. I already put the Aerotech stripes decal on and took it off after only an hour. I did not like it.

1974_Trident

26th January 2010, 02:57 AM

It's finally finished.

Just finished attaching the shock cord and parachute. For the first time ever I have seen my G-Force in its complete form.

I decided to use a flame pattern from the sleeve of one of my Harley Davidson T-Shirts. Well, kinda. The flames on the shirt fade yellow to orange from the center of each flame out. I am not that talented with making paint masks so I did the fade from orange to yellow front to rear. I am pleased with the results. The wrinkling which arose when I sprayed the clear coat over week old orange has nearly completely settled, I have to look hard to find it.

I can't wait to fly it this weekend, I just hope the weather permits.

A concern i have now is the finished weight of the rocket. The instructions and all marketing data for the G-Force all say the rocket weighs 907g. I put the finished rocket on a triple beam balance and it weighs in at a whopping 1479g without a motor. A loaded motor adds another 143.69g which places this rocket well above the 1500g threshold established by FAR 101.22. Aside from regulatory burdens I am also concerned about the air worthiness of this rocket on G impulse. All of the advertised literature promises flights of 800 ft. flights (1200 ft. with a G-80T). I am now wondering if I will make a spectacular lawn dart. I guess I should get some G-80Ts to play it safe.

Has anybody here ever built and weighed a complete G-Force? Did I really add an additional pound of paint and epoxy? I know I used Approximately 4 oz of epoxy for fillets which are not mentioned in the directions. On Aerotech's website there is a video showing assembly of a rocket which looks like it could be a G-Force and no filleting was done. I just can't see building a rocket without filleting. I have to now go into my garage and count empty paint cans which promises to be an exercise in futility, I sanded off most of the paint I applied. I have no Idea how much over spray is on the garage floor except it is a lot.

I am really afraid to fly this rocket now after all of the time I put into it.

terryg

27th January 2010, 01:30 AM

At that weight rocksim gives the following results:

The G64W and G76G reloads give an altitude of ~ 600ft with an optimal delay of 4.5 sec

The G80T gives an altitude of ~ 775 ft with an optimal delay of 5.5 sec

Low and slow easy to recover flights. Launch in low winds for best results. It will really get the best flights when you get into the smaller high power loads.

H128W gives ~ 950 ft and the H165R gives a little over 1000 ft.

1974_Trident

27th January 2010, 04:44 PM

TerryG, Thank you very much. It is good news that my rocket will still achieve fun altitudes. I really don't want to fly this rocket too high. After all of the effort I put into the paint I would hate to scuff it on a communications or GPS satellite.

I am planing on my first launch this weekend. Actually this is going to be a family launch fest. My sons are anxiously waiting to fly their new Big Bertha and Der Red max while my Daughter's Alpha is in between coats of paint as I type this. Pink and purple of course.

I have a pile of reloads as well as A through C engines to bring along. Weather permitting, this should be a fun weekend.

UPscaler

27th January 2010, 06:15 PM

blackjack2564

29th January 2010, 07:54 AM

Mine weighs 3.6lbs.[pretty darn close to yours]

Fly it on G-64 4sec delay.....perfect flight to around 500ft consistently.

Also fly it on H-165 to 1100ft
H-97 to 1280

I put little cheapie altimeter in payload to get those heights.

You will be fine.

SuperSlim

1st February 2010, 12:18 AM

I even see possibilities with a G53-5 which seems like it would give a nice slow liftoff for my viewing pleasure. I may even get a few F loads.

I had a G-Force for a brief time and I have seen several launched. I would steer clear of the G53 or anything smaller. I certainly would not tempt fate by shooting an F either, unless of course you are going to video the crash and post it on You Tube. If you look at Aerotech's recommendations, they don't recommend Black Jack or F motors.

The G-Force is a cool rocket but it turns land shark in a hurry unless you put some oomph behind it.

1974_Trident

7th February 2010, 12:05 AM

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

7th February 2010, 02:33 AM

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

7th February 2010, 02:48 AM

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

7th February 2010, 03:04 AM

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

7th February 2010, 03:49 AM

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

15th February 2010, 12:54 AM

Whats the height of this rocket??Alex

1974_Trident

15th February 2010, 06:02 PM

Whats the height of this rocket??Alex

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

exprditer789

15th February 2010, 08:20 PM

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

1974_Trident

15th February 2010, 09:59 PM

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

exprditer789

16th February 2010, 12:11 AM

Thanks! That is a nice size rocket.Alex

Johnny1Eye

16th February 2010, 01:17 AM

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

17th February 2010, 09:16 AM

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

17th February 2010, 05:28 PM

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

17th February 2010, 06:33 PM

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

17th February 2010, 07:02 PM

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

17th February 2010, 07:47 PM

...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

17th February 2010, 08:07 PM

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

18th February 2010, 04:38 AM

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

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

terryg

18th February 2010, 07:36 AM

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. :D 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.

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

Rocketeer41

26th February 2010, 10:33 PM

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

Luv2launch

27th February 2010, 01:50 AM

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

27th February 2010, 02:25 AM

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

27th February 2010, 02:13 PM

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

27th February 2010, 06:06 PM

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

28th February 2010, 06:33 PM

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

quickburst

28th February 2010, 07:03 PM

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

28th February 2010, 07:41 PM

What?:shock:

blackjack2564

28th February 2010, 08:45 PM

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

11th January 2012, 02:24 AM

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 :rolleyes: too.
Oh, FYI- I use only recommended engines, 29mm RMS hardware.

Thanks!!

CF-105

11th January 2012, 03:56 AM

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.

fyrwrxz

11th January 2012, 04:32 AM

loopy

11th January 2012, 04:34 PM

I've haven't had any problems like this with my Barracuda, either. All I can say is make sure the fit is right at flight time, not just the night before in your basement. Humidity/heat can have a dramatic effect on the fit of couplers.

DRAGON64

11th January 2012, 06:43 PM

My G-Force was cursed from the get-go!!!

I bought a G-Force, and it was a lemon. The body tubes were blistered from trapped air buubles, and the nosecone was warped something aweful...and that was just opening the box. Granted, I purchased this rocket right after Aerotech demoed the rocket at NSL `99, so the first production nosecones were junky Ace cones.

Haggled with Aerotech to get replacement parts; the tubes were better, but I received another warped Ace cone...

built the rocket, and on it's maiden flight, the rocket landed in a tree. Second flight, the rocket flat spun to the ground makeing one of the fins a little shorter. 3rd flight was nice, and the parachute deployed, but the rocket landed while blowing sideways, and shortened another fin...

Funny thing is, I have video of the Aerotech demo, and it launched beautifully on a G64, and flat spun to the ground breaking a fin... I should have seen the signs, that this was not going to be a good rocket... at least for me

KenRico

11th January 2012, 09:21 PM

fyrwrxz

11th January 2012, 09:27 PM

My wife says I have a great sense of humidity, but I don't tend to sweat things like that.....

soopirV

11th January 2012, 09:30 PM

Soo- Sorry to hear of your experiences. My Mirage flew 97 flights before I killed it with too many g's packing the wadding. Barracuda has 54 flites and just looks beat from the desert. Big "A" the same. Both still works great. Could humidity be a factor in your area?

Thanks for the kind words- I live in Tucson, AZ so I don't think humidity is a factor. My original hypothesis (still current) is that weather cocking or some other oblique force is causing flexion of the tubes, binding the coupler; it does seem that the fins on AT kits are oversized, but why wouldn't everyone be seeing that?
Unrelated, but where do you fly? We're not so far apart and I'm looking for better fields- on my drive to San Diego with the family last week I saw some promising areas between Tucson and Yuma...

fyrwrxz

11th January 2012, 09:37 PM

Oh buddy!!! You have GOT to come out to Plaster City! Next launch in Feb-check out San Diego Tripoli for directions and schedules- Come on over and fly Fiesta Island with us! It's a challenge with the LPR limit and huge water hazzard! Look up San Diego D.A.R.T. club.

soopirV

11th January 2012, 10:28 PM

KenRico

13th January 2012, 02:28 AM

Could , humility be a factor ?

You should post your praying to the Rocket Gods pic with your k*ck *ss Blacked out G-Force with tailcone ! Or I can if you wish . . .

Kenny

Here it is ! Warned ya . . .

gldknght

13th January 2012, 03:02 AM

I am brand new to re-loadable motors but I have experience handling things that go, "boom." I am considering the Aerotech (or Rouse Tech) 29/40-120 hardware and an assortment of G impulse loads; G64-4, G71-4, G76-4 and I even see possibilities with a G53-5 which seems like it would give a nice slow liftoff for my viewing pleasure. I may even get a few F loads.

Of these motors you mentioned, the G64 has the most get up and go. You DO NOT want to try anything less than a G64-4 in the G-Force. And that is barely enough motor. I've had two of these rockets and both crashed due to not enough altitude from G64's. It was my own fault, wrong delays, but both crashes were on maiden flights.

You might get 700 ft out of a G64, but probably will be more like 500 or so.

loopy

13th January 2012, 04:57 PM

Of these motors you mentioned, the G64 has the most get up and go. You DO NOT want to try anything less than a G64-4 in the G-Force. And that is barely enough motor. I've had two of these rockets and both crashed due to not enough altitude from G64's. It was my own fault, wrong delays, but both crashes were on maiden flights.

You might get 700 ft out of a G64, but probably will be more like 500 or so.

The G-71 and the G-76 he mentioned both have a higher initial kick off the pad then the G64 does. The G71 has slightly less total impulse (108 N-sec vs. 112 N-sec), and the G76 has slightly more total impulse (112 N-sec vs. 118 N-sec). Any one of those three motors will give a decent flight, with similar performance. I love the G71R, and the G76G loads!

Handeman

15th January 2012, 04:28 AM

I love the G64. The G71 & G76 are also great motors.

The problem any of these can have in a G-Force, IMHO is weak ejection. I've never owned a G-Force, but I've seen more of these then any other model come in ballistic or under nose pop recovery because the ejection charges on the Hobbyline motors didn't pop the nose cone, or if it did, the chute never left the BT. I would recommend a little extra BP to the ejection charge, 0.2g or 0.3g should be enough to increase the reliability of the ejection significantly.

gldknght

17th January 2012, 07:33 AM

The G-71 and the G-76 he mentioned both have a higher initial kick off the pad then the G64 does. The G71 has slightly less total impulse (108 N-sec vs. 112 N-sec), and the G76 has slightly more total impulse (112 N-sec vs. 118 N-sec). Any one of those three motors will give a decent flight, with similar performance. I love the G71R, and the G76G loads!

Why is it then that Rocksim always shows the G64 sending any given rocket to a higher altitude compared to those other two motors when used in the same rocket?

loopy

17th January 2012, 04:50 PM

Why is it then that Rocksim always shows the G64 sending any given rocket to a higher altitude compared to those other two motors when used in the same rocket?

Probably because the G64 burns longer than the other two. It's a flatter thrust curve than the other two. The other two are harder hitting motors at ignition, so they will give more kick off the pad, but don't burn as long.

gldknght

18th January 2012, 04:29 AM

Probably because the G64 burns longer than the other two. It's a flatter thrust curve than the other two. The other two are harder hitting motors at ignition, so they will give more kick off the pad, but don't burn as long.

Ok, so we agree that of all three, the G64 goes the highest, right? What I guess I'm getting at is the Gforce starts coming back down quickly after motor burn out. 500- 700 ft doesn't leave all that much time to deploy a parachute.

loopy

18th January 2012, 01:23 PM

Ok, so we agree that of all three, the G64 goes the highest, right? What I guess I'm getting at is the Gforce starts coming back down quickly after motor burn out. 500- 700 ft doesn't leave all that much time to deploy a parachute.

I honestly don't know - I don't have any sims set up, so I can't give any results. I would imagine that the flights would all be relatively close in altitude, but can't say for sure. The other thing to keep in mind when determining what to use is delay times. If one motor is going to deploy late, and one is not...well - which would you use?