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AGM-12C Bullpup

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Stones

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I thought I'd try scratch building a AGM-12C Bullpup.
This is the one which has a forward (just behind the NC) transition. Pic attached.
I've searched extensively on the net and can get the basic dimensions but, no detailed stuff. Like NC length, transition- tailcone sizes, etc.
Any help would be greatly appreciated.

tia...
 

jetra2

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Ya know, Stones, if I had to say any one thing...

It would be that I would think building/shaping/turning the NC and transition as one piece, the using a router or something to cut slots for the fins in the NC for those upper fins.

My two cents,

Jason
 

Missileman

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That pic I recognize.
It appears to be from performance hobbies launch pad kits page.
I just happen to have that kit on my desk as we speak.
It has not yet begun construction.
email me and I will send all dimensions and all fin patterns ect...
 

Stones

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Jason...
I plan on just what you describe, as far as having the fins pass thru the wall of the NC. I still my have the NC be seperate from the transition. Don't have all the details worked out, quite yet.

Missleman...
Sent you off an email. Tnx much!
 

teflonrocketry1

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I think you might need some additional nose weight in this model to make it fly stable. Anyone have a RockSim file for this design?
I can make a simulation file, your chioce of RockSim version from 4 on up or a VCP simulation file if you post the dimensions.

Bruce S. Levison, NAR #69055
 

Stones

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I'd like to thank Missleman for his time and efforts in getting me the info I needed, to get the ball rolling.
Here's a preliminary RSim pic of the build. Bruce...you're correct that NC weight is a must for stability. I'm sure there'll be some tweaking and changes before work begins.
 

Micromeister

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Stones heres a Page of bull pup specs and pics. If you need a higher res version, Drop me an e-mail.
 

rkt2k1

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Stones,

That's a great looking "preliminary" rsim picture of your Bullpup 12C! Can you post the rocksim file? I just recently finished a 12D and would like to try the 12C.

Thanks,
 

Stymye

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I have been working on one myself...
heres a screenshot,,for scaling purposes, if rocsim is not an option.
 

Stones

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Originally posted by rkt2k1
Stones,

That's a great looking "preliminary" rsim picture of your Bullpup 12C! Can you post the rocksim file? I just recently finished a 12D and would like to try the 12C.

Thanks,
Here ya go...
 

rkt2k1

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Thanks guys!!

Stymye: What CAD program are you using? I'm looking for one that I can do 2D and 3D drawings and designs that is relatively easy to learn.
 

Missileman

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Hey thats just what I was looking for.
That site has decal files in various sizes.
They are as far as I can see for a 12d but a few minor mods will take care of that.
Thanks for the link:D
 

AZ_Ron

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here's a shot of a 12C that I've had for years... I can't remember if it came from A.B.M.R. or someones website...
 

Stones

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With regards to NC fins. Does RSim simulate stability, accurately, when the NC has fins? Reason I ask is, I'll need about 4 oz. of weight in the NC on this build. Though the fins themselves have weight, when removed from the NC, the stability increases for the rocket. So, without fins on the NC, I could decrease the added weight and with the fins, I need to add more. Make sense?
 

daveyfire

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Makes sense because the fins in front shift the C<sub>p</sub> forwards, thus necessitating the extra noseweight.

However, I have noticed some issues with RockSim and canards while working with the Gates Brothers. They built an upscale PML Bulldog and flew it on an N2000W. First sims for the rocket were coming out to around 1700 feet -- doesn't make sense for a 100 lb rocket on an N2000W. They took off the canards and it simmed to over 7000 feet (makes more sense). When it actually flew, it made it up 6000 and change. Any idea on what might cause this drastic variation?
 

Missileman

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I understand what you are saying but consider this.
how accurate is Rocsim with the nose fins?
Assuming all is as it should be would not the Rocsim also already take into account the weight of the fins in that position?
 

Missileman

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a little add on info,
I don't use Rocsim to calculate nose weight. Only to get me in the ball park.
I do rely on it for CP calcs.
Once I know the CP I Go about 1 1/2 body diameter fwd and balance there.
I use #8 lead shot ($10 for 25lbs at Gander Mountain) I find out how much my propellant is suppose to weigh and use an equivalent ammount of shot rolled up in paper and stuffed into my motor casing. Load rocket up as for flight Motor, chut ect..
Now I tape a sandwhich baggie to the nose and start filling with shot until the rocket is balanced where I want it.
I like the shot as it mixes well with epoxy and is cheap:D
 

Stones

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DF...
That is strange with the big difference in altitude. Of course, a much larger rocket than I'm building here but, I tried simming with and w/o the NC fins and it changes the estimated altitude by only feet.

MM...
I see your point. I may have to go with a stock 8" ogive NC ( per Estes Phoenix) minus the "hat". I'm afraid with 4oz. of weight up there, even a "soft" landing would more than likely destroy the tip. Unless it was made of solid epoxy. I'm not quite sure how to go about that and have it stay "stuck" to the plastic NC.
 

Missileman

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Here is a thought on that,
I am basing this on my Skunkworks Saturn V.
It uses 2 long shock cords, 15' on the drouge and 30' on the main.
The idea is that the nosecone (wcich has 25lbs of weight in it) hits the ground first. with this weight gone the rest of the rocket with the fragile details slows down and touches down nice and gentle.
If you use a fairly long chord and have the chute near the nose perhaps this would have a similar effect in reverse?
 

Stones

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Originally posted by missileman
...
If you use a fairly long chord and have the chute near the nose perhaps this would have a similar effect in reverse?
Rgr that. This is the way every rocket I have built to date recovers. Chute is attached to the NC via eyescrew. Of course, I haven't built anything much over 2 lbs. "yet". ;)
 

Stones

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Question on attaching the "hat" to the NC. I plan on epoxy (inside and out) and wanted to know if drilling some small holes in the NC for the epoxy to attach itself to or a major "scuffing" will work. Also, the seam where the "hat" is glued to the NC, any good tips on smoothing this transition to make it as seamless as possible?
I'll be posting some part pics here shortly.
 

Missileman

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I did, as the directions instructed, drill a hole in the tip of the nosecone to relieve any pressure in the hat.
I used spot putty to feather in the seams.
I would scuff the attachement point as well as an area aft of the seam to help hold any filler you use.
I have done 2 cones this way so far.
The first I fiberglassed with 3/4 oz. glass.
The second I soaked with thin CyA.
Both came out about the same.
I think on my next project I may try turning a solid extension and see how that works out.
 

Stones

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Here's the basic layout of the parts needed to build this one.

From left to right as follows:
(2) 24.0" x 4.0" lengths of .125" basswood (with templates)
The lengths will be glued together so the large fin template can be layed out correctly with the grain.
(1) #110 cardstock transition 2.65" x 4.06" x 4.79" in length.
(1) #110 cardstock transition 2.72" x 4.06" x 3.46" in length.
Both of these transitions are double walled. They were glued using 3M Super 77 spray adhesive. They have a smooth seam and are coated with sanding sealer.
(1) 2.60" x 12.50" Estes BT
(1) Estes PNC80 NC with attached "hat". Hat internal is solid 5 minute epoxy.
(1) 2.60" x 5.0" LOC BT
(4) .0938 basswood CR's - 2.60" I.D. x 3.90" O.D.
(2) .500" x 3.90" O.D. LOC couplers
(2) .125" x 1.141" I.D. x 2.58" O.D. CR's - with T-nuts installed on one(1) ring.
(1) 1.141" x 16.0" LOC BT (MMT)
(1) 4".0 x 20.25" LOC BT

I will post pics as the build progresses and will detail any of the build for those that are interested.
 

Stones

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To keep the basswood sections flat while glueing, wax paper is placed on both sides of the wood and weights are placed on top. I'll let this dry overnight, sand the glue seam and then check it's length for any warp.
 

CTimm

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Originally posted by Stones
I AGM-12C Bullpup. NC length, transition- tailcone sizes,
Any help would be greatly appreciated.
I don't know about the AGM-12C Bullpup, but I did measure the AGM-12D Bullpup B!!!

Tailcone starts out 14.25" diameter and increases to a main motor diameter of 17.35". The tailcone is 13" long.

Motor is 17.35" diameter, and 87" long.

Forward tapered section is 20" long, tapering down to a 12" diameter.

Cone is 12" diameter, 40" long.

Some dimensions are rounded off to the nearest inch, both for simpler scaling, and the fact that not all museum displays are assembled within the same tolerances (i.e. They make up stuff for display purposes)

The canard fins are 8.25" long root edge, 3.5" wide trailing edge, and the trailing edge is positioned 12" from the base of the 12" diameter cone. 1/2" thickness.

The main wings are more complex to describe.
Heres a set of X and Y coordinates to plot out.

X Y
0.00 0.00
0.00 8.00
9.50 0.00
9.50 -1.32
20.25 11.68
32.00 11.68
44.75 -1.32

Main wing trailing edge is located 11" forward of aft end of 17.35" motor casing. 5/8" thickness.

Flares are 11" overall, with the first 6" being cylindrical and the 5" left tapers to a point. Diameter is 1.75".

Is this enough or do you think you'll need more??? :)

CTimm
 

Stones

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Fins are cut. Nosecone is shaped and ready for fins. I'll drill some small holes along the fin line on the nc to help "rivet" the fins on with epoxy.
 

Stones

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Here's the NC. There are 4 small holes drilled in the NC, equally spaced under the root edge of each fin. They fins were attached with medium CA and fillets are of slow cure epoxy. Sanding sealer on the remainder of the fin surface followed by 3 coats of primer.
Next to a stock PNC80 for comparison.
 

Stones

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The main airframe spirals are filled and fin slots are cut. I normally use Fill'n'Finish for this but, had picked up a tube of Bondo glazing/spot putty for use on the NC so, I thought I'd give it a shot. It's a real nice consistency, right out of the tube, and drys fast. Very sandable. Fins slots are done with a Dremmel.
 
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