G-FORCE Build

I just finished the motor mount assembly. All I need to do now after the epoxy sets is to test/dry fit it in the airframe along with the fins. I also cut out the slots for the fins and launch lugs.

The instructions call for Medium CA or 5-minute epoxy for adhesive. I have 5 minute, but decided to use up the rest of my 15 minute epoxy instead. I also use milled fiberglass to make it stronger and thicken it some. I'll use the medium CA to attach some of the smaller pieces in place such as the fin lock rings, which btw are pretty tight as they are without glue.

86mustang408w said:

Ok...Does the included mesh "system" that comes with the kit fail often? I'm just wondering if I should make a few upgrades. Its not a super expensive rocket, but I don't wanna add it to a scrap pile either.

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In 20+ years of designing/building/flying AeroTech kits I have not had a problem with the cooling mesh sytem. I even use it on several of my larger scratch built models.

Follow the instructions and do not get any glue on the mesh.

I dry fitted the motor mount and snapped the fins into place. Looks like I will be doing some sanding to get the fin tangs to touch the motor mount tube. The center rings fit in the airframe a little looser than what I like, but I'm sure after I use a thick batch of epoxy it will be fine. I decided to switch over to 5 minute epoxy since I used up what was left of my 15 minute. I should have everything glued up today. Before I apply the AFT center ring I'm going to make internal fillets for extra strength.

Rex R said:

I weighed an aeropack & an estes retainer...as I recall the aeropack was 0.2g heavier(iirc 13.8g vs 14g) the Estes retainer does take up a bit more space though.
rex

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see? heavier!

I agree that it is larger in diameter, though. that prevented me from using one on my wild child (38 mm body tube). that isn't an issue with the g force, though.

Looking good!
Great photos too.

JP

If this will be of any value, I glued up a rocket like you are doing, and did not place the aft centering where it needed to be while the glue was drying. The body tube warped a little and the aft ring would not fit after the glue dried. I had to go back and custom fit the aft ring to match the distortion. Maybe you have never had that experience, but I wanted to give you the heads up so you could consider it.

BEAR said:

If this will be of any value, I glued up a rocket like you are doing, and did not place the aft centering where it needed to be while the glue was drying. The body tube warped a little and the aft ring would not fit after the glue dried. I had to go back and custom fit the aft ring to match the distortion. Maybe you have never had that experience, but I wanted to give you the heads up so you could consider it.

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I think I will glue it up all at once...maybe use 30 minute epoxy to buy some time? Right now I'm gluing the forward ring into the airframe and I have a fillet on it and it's drying. The fins are in place and they are helping to keep things aligned. I'll go back and apply the epoxy later to the center ring along with fillets on the inside so the fins are more secure.

I got the fins epoxied in place and the front center ring. I'm allowing things to set up and then I'll make another batch of epoxy and do the internal fillets and then epoxy the AFT center ring into place. So far things are going well...some of the parts on this kit need sanding to fit properly...I noticed that the fin tabs don't seem to seat all the way, but I guess they are close enough. After I put in the fillets it should cover everything and add some strength.

Well today was very productive. I basically assembled the AFT section of the rocket. I used BSI 5 minute epoxy throughout the build. I just saw a need to use it over the medium CA. A lot of the parts such as rings didn't really fit that great; there were gaps so I used the epoxy to fill in the gaps. I'm changing my approach to this build. It's going to just be basic and nothing spectacular. I'm going to glue the nose cone. I was going to use the upper for a payload, but opted out. I just don't see a need to do more than that. I'm probably going to fly it a half dozen times on some "G" motors to get a feel for how well it flies and then go for my Level 1. That's it and afterward it will be mostly be a "G" flyer. I'll be happy to get my Level 1 so I can buy some bigger and better kits.

Just a quick question. The fins have some gaps underneath where they were injected for the mold (another reason why I don't like this kit) and I want to use some epoxy to make fillets and fill those it. I have 5 and 30 minute. Would 30 minute epoxy be my best choice?

Attached are a couple more pictures. The AFT center ring is now epoxied in place and I'll be adding another center ring mostly for looks and to have something for the retainer to butt up against, but mostly for looks.



I also need to place an order with Hobbylinc for a couple LOC tube couplers. The one that comes with kit doesn't fit and yeah I know I can peal it back and the one that my friend Dave sent me fit at first, but somehow swelled...maybe the change in weather caused it, not sure, but no big deal...I need some other supplies as well.

If I may, please let me address a couple of your issues. By the way, your build looks really good to me and I really appreciate seeing your photos.
With the gaps under the fins at the main body tube, I used Gap Filling CA (made by BSI, also)to fill in those gaps and it works great for me.
As for the coupler, I bought a LOC couple for mine so that I could build my altimeter bay. I have peeled the OD on coupler before, but I replace what I peeled on the outside with re-enforcement on the inside. I have a ream of card stock that I bought in Wal-mart in the office/school supplies and I will glue that on the inside of the coupler to make it stronger. (I also do this on the inside of paper body tubes, like BT-60s when I am flying Gs and Hs in them for altitude stuff.) I hope this helps. BEAR

If it were me, I wouldn't do much in the way of a fillet on the fins, just enough to
fill any voids. I would use the 30 minute epoxy in order to fill more fins and it has
a little more strength than the 5 minute.

Question; the motor tube looks like it's 3-4 inches inside the body tube. If that's the case
does this not put the exaust and flames too deep and not nearer to the outside of the body tube?

JP

Well I took a little break and then came back and tested fitted the AFT decorative ring. I used a blue marker to mark the correct dept all around, which works out to be 2" from the AFT ring to the AFT end of the airframe. I reinstalled the ring using BSI 30 minute epoxy to allow myself some work time. I haven't apply any fillets, but I will when I cut to fit the tube coupler to reinforce the AFT section of the airframe.

The eye screws were there to help me pull the ring out after I test fitted it. The Aeropack retainer is dry fitted and it fits like a glove. Snug and secure. I need to get some JB Weld and few other items so I might take a short break from this for now.



I hope you guys are enjoying the process. I'm making good time on this build, but taking my time to make sure everything fits the way it should.

BEAR thanks for your suggestions. I don't have any thick Ca, so I'll place an order this week with Hobbylinc. I have a few other items to order as well

My G-force fins fit the same way... terrible. I had to use a ton of epoxy to fill that gap and add a little fillet. Also, I used putty to fill the mold marks down by the root edge. I remember building Aerotech kits about 10-15 years ago the first time around, and I don't remember the quality being like this. But who knows... even Estes is selling out to China now.

skyway2k said:

My G-force fins fit the same way... terrible. I had to use a ton of epoxy to fill that gap and add a little fillet. Also, I used putty to fill the mold marks down by the root edge. I remember building Aerotech kits about 10-15 years ago the first time around, and I don't remember the quality being like this. But who knows... even Estes is selling out to China now.

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I could use epoxy clay maybe and then again I may not use anything. Either way I have to wait awhile before I get the supplies I need to finish. I wish they would make pieces fit the way they should namely the coupler. Sanding is a PITA!

I used a little epoxy to fill the gaps too, although mine weren't too bad as I put epoxy on the root of the fins before I assembled them. this minimized most of the gaps.

as for the injection molding spots, I sanded them down and they ended up ok. the small epoxy fillets covered the rest of the blemishes.

JP Morgan said:

Question; the motor tube looks like it's 3-4 inches inside the body tube. If that's the case
does this not put the exaust and flames too deep and not nearer to the outside of the body tube?

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the end of the motor tube is kind of up there in the body tube. I moved the mmt back 1/2" to help a bit. the retainer also helps move the motor back a bit.

members at my club suggested coating the aft centering ring and inside of the body tube with epoxy to prevent it from getting scorched by the flame. I ended up coating it with titebond 2 as it would have taken a lot of epoxy to cover everything. I figure that is better than nothing.

Jokingly, someone said buy your epoxy in quarts and gallons and then the little bit used in the G-Force will not seem like so much. When you get to building something bigger, (like our 16' tall club project of the Proton M rocket, that is 3 stages and uses 12 motors) then 100 sq. inches of surface area will not seem so big. Just a few pumps with the West system.:wink:

yeah, but the epoxy would have cost about double what the rocket cost!

I think what I'll do is fill the gaps with gap filling CA and then sand down the injection molding spots. I'll use some squadron green putty to fill any imperfections before I sand. I just think using the CA would look better in the long run. I have a lot of internal fillets and the fins are on there pretty good.

Coffee is brewing now...need my fix of java:caffeine:

BTW - As the AFT section sit it weighs in at 19.5oz

Guess I could have been quiet and saw your pics too see what you meant by the aeropack kit, I may have to do the same I see what you mean. Thanks the help before, have a good launch, Michael B.

Right now I'm sanding the tube coupler, not the one provided in the kit, but the one my friend Dave (fyrwrxz) sent me. Thanks Dave! It looks like a LOC coupler ... anyway I'm sanding it to fit in the AFT section of the rocket. The instructions have you fit the coupler in the upper portion of the airframe 3" in with the bulk head. That doesn't leave a whole lot of room for the shock(s) and chute, so I'm going to fasten mine to the AFT and then use the coupler provided for the bulk head, but I want to put it further up into the airframe...to allow enough clearance for the nose cone shoulder.

After I text fit the coupler in the lower section I'll use some 30 minute epoxy to set it in place. I'll come back later and reinforce the inside of the coupler with some thin paper/card stock since I had to sand a lot of material off it. I'll also CA the edges of the coupler. I will do this procedure on the upper coupler/bulk head section as well.

I'll post pictures later when I'm done.

WOW!!! I test fitted the coupler after I sanded it and pushed it all the way down. It was very very tight. I tried unsuccessfully to remove it so I can epoxy it, but decided that it would probably be best if I just left it and applied a epoxy fillet so that's exactly what I did. I feared that some how I would damage it trying to remove it and didn't want to risk it.

I also applied a bead of thin CA all the around the edge of the body tube that comes into contact with the coupler as well as the edge of the coupler itself. I used an epoxy brush and 30 minute epoxy mixed with milled fiberglass. I brush and gathered the epoxy in the fillet area. Afterwards I rotated the rocket to allow the epoxy to evenly spread and just let gravity do the rest. If I hadn't known this was epoxy I swear it looks like the glaze they use on Krispy Kream Donuts :rofl::rofl:

I was considering reinforcing the coupler inside, but decided not too. I don't really want to hassle with and I'll leave it the way it is.



I'll still sand the coupler and the upper airframe to make sure I have a good fit, but NOT too snug. The other coupler I will cut about 2" off and use this piece to reinforce the AFT section of the AFT airframe; the rest of it I'll use for the bulk head of the project. This time I'm going to peal the outer layer of paper to save some time on sanding.

Things left to do on the AFT section

• Fill in gaps where fins meet airframe using thick CA
• Reinforce AFT section with coupler
• Lightly sand airframe
• Use FnF to fill spirals
• Sand FnF
• Use green squadron putty to fill imperfections in fins from injection molding
• Primer AFT section

Another thought, you could use the card stock instead of the coupler (then you only have to cut strips of card stock instead of cutting a coupler) and glue it into the aft end of your "fin can" to re-enforce that end. BEAR

BEAR said:

Another thought, you could use the card stock instead of the coupler (then you only have to cut strips of card stock instead of cutting a coupler) and glue it into the aft end of your "fin can" to re-enforce that end. BEAR

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If I could find some very thin aluminum and epoxy (JB Weld) it into place it would also displace the heat as well reinforce the airframe...hmm??

I know I probably shouldn't concern myself with the recovery system now, but I'm going upgrade the chute and the harness. My biggest issue it seems is my rockets suffer the most damage when they land under the parachute. Probably because I launch at a dry lake bed and the surface is harder than your grassy fields and open plains. The stock chute is 42". I sold it a long time time ago. Not sure yet what I might upgrade to, but I was considering maybe 45" or 48" depending on the mass weight of my rocket.

I'm thinking about using 15' of Kevlar attached to a delta link on the AFT section. The Kevlar will have loops sewn in at each end. Then I was going to use about 9' of the stock elastic cord to allow the shock cord some give and prevent zippering. I know what you are thinking that it's not going to work or I should use Kevlar through out or a combination of Kevlar and nylon, but every rocket that I built with a Kevlar shock has zippered and I make the shock 5-6x the length of the body tube and yes my velocity at apogee are between 6-15 mph, so what gives? IDK? but I'm tired of dealing with it. The upper section is 3' plus the 9' equals 12' so the two sections should not collide under the chute. I could always go shorter maybe 7' if I want to play it save.

Anyway just my :2:

Special Note: I wanted to come back and add the descent rates based on a rocket that weighs in at 45.5 oz

Fruity Chute 36" Descent Rate = 9.9 MPH
Fruity Chute 42" Descent Rate = 8.6 MPH
Fruity Chute 48" Descent Rate = 7.5 MPH
Top Flight 45" Descent Rate = 9.1 MPH
Top Flight 50" Descent Rate = 8.2 MPH

Fruity Chutes have an estimated CD of 1.600
Top Flight have an estimated CD of 1.3400

I'll be launching on a dry lake bed which is a harder surface. Do you guys think that 8.2 mph will be slow enough not to caused any damage or should I invest in a larger chute above that? You feed back is appreciated. Of course I won't know until I weigh my rocket what chute to get, but just kicking things around right.

I pealed back a couple layers of the tube coupler and it fits in the upper airframe perfect!! I'll cut about 2" off the end and use it as reinforcement in the AFT section airframe. I'll 30 minute epoxy. I'll also install the bulk head section leaving enough space to clear the shoulder of the nose cone and as it turns out I'll have some extra room, so maybe I'll decide to attach the nose cones via screw and drill a few holes in the upper section for my Jolly Logic Altimeter. Yeah that's probably what I'll do...

I just finished epoxying the reinforcement ring in the AFT section. I used 30 minute epoxy with milled fiberglass. I mixed up a little to apply to the inside of the coupler to make it look nice and uniform and to strengthen it. I used the excess epoxy that over flowed for part of this...the rest is up to gravity to form the ring fillet...

I'll set it aside and allow it to dry while I work on the bulk head section.

AfterBurners said:

I know I probably shouldn't concern myself with the recovery system now, but I'm going upgrade the chute and the harness. My biggest issue it seems is my rockets suffer the most damage when they land under the parachute. Probably because I launch at a dry lake bed and the surface is harder than your grassy fields and open plains. The stock chute is 42". I sold it a long time time ago. Not sure yet what I might upgrade to, but I was considering maybe 45" or 48" depending on the mass weight of my rocket.

I'm thinking about using 15' of Kevlar attached to a delta link on the AFT section. The Kevlar will have loops sewn in at each end. Then I was going to use about 9' of the stock elastic cord to allow the shock cord some give and prevent zippering. I know what you are thinking that it's not going to work or I should use Kevlar through out or a combination of Kevlar and nylon, but every rocket that I built with a Kevlar shock has zippered and I make the shock 5-6x the length of the body tube and yes my velocity at apogee are between 6-15 mph, so what gives? IDK? but I'm tired of dealing with it. The upper section is 3' plus the 9' equals 12' so the two sections should not collide under the chute. I could always go shorter maybe 7' if I want to play it save.

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I use a 15', 1/2" kevlar line with loops sewn on both ends. I installed u bolts in the top centering ring and the payload bulkhead and use quicklinks to attach the line at each end. It is way overkill. the chute is tied to a loop about a third of the way down from the payload, and I have a kevlar blanket tied to another loop about a third of the way above the booster.

the 1/2" kevlar is pretty wide, and the sewn part of the loop winds up at the ends of the tubes. I haven't had a zipper with this setup.

Looking good!
There ought to be a G Force Festival every Spring.:clap:

JP

If you wanted aluminum in the aft end of the fin can, why not take the gap filling CA (check the Bob Smith web site about adhesive properties on aluminum, and glue aluminum foil into the hollow on the bottom of your fin can. You can wrap layers if you want to. I have used .003" aluminum shim stock to make laminated fins on some of my altitude rockets and glued the layers together with the gap filling CA or the Extra Thick CA. (Fins .030" thick) Or you can go to the hardware store and see if they have back in the section where there is a K&S display of aluminum, copper, brass, and stainless steel tubing, in 1' to 3' lengths and get some sheets of steel or aluminum that are .010 thick. Then you can glue that on the bottom of your rocket. You could also take a coke can and use the aluminum in it for your heat shield. I wonder how heavy your find can is now with all the epoxy. My un-painted fin can weighed in at 1 lbs, 6.6 ozs. I hope I am helping and not distracting you. BEAR