Bull Pup 12C

[Frodo2801]

I'm trying to build a 1/3 scale AGM 12C Bull Pup. I've rocsimed and thought I would see what sugestions or thoughts any one had.

 

[Stones]

If you want "scale", you'll need to move those canard fins to the NC.

 

[Frodo2801]

I tried that but rocksim 5 won't sim the flight correctly with the canards on the nose cone. I had planed to do that in the build. How much weight did you have to add for stabilty on yours?

 

[Fore Check]

I'm pretty "wowed" by the nearly 4 lbs. you've got in the nose of your design...

 

[Frodo2801]

Thats what it took to make it stable with the J350W. I guess its the location of the fins.

 

[Stones]

Originally posted by Frodo2801
I tried that but rocksim 5 won't sim the flight correctly with the canards on the nose cone. I had planed to do that in the build. How much weight did you have to add for stabilty on yours?

I added 4oz. to the NC and that has it marginally stable with a G33 loaded.
I'm curious on how RS is not simming correctly with the NC fins. Is something in RS telling you this or are you using other calculations?

 

[Frodo2801]

There is no way to add the fins on the nose cone so I put them on the transition and located them -2" of the owning edge. This gave me more stability so that I could remove some weight but when I try to sim the flight it only went 485' on a J350. When I moved them back to 0 it simed to 2745'.

 

[Stones]

Originally posted by Frodo2801
There is no way to add the fins on the nose cone ...

Take a look at this file. It can be done.

 

[Frodo2801]

What version are you using? I have ver. 5 and I couldn't read that file.

 

[Stymye]

mabey you can make the lower half of the nosecone a transition

 

[Stones]

Originally posted by Frodo2801
What version are you using? I have ver. 5 and I couldn't read that file.

Sorry, version 6. I forgot that you have 5.
Anyways, what Stymye said. The very front of the NC is a conical piece and the rest of it is a transition. I'll give you the dimensions shortly. The other half is calling for dinner.

 

[Stones]

Start with a NC that is 3" long with a diameter of 1.5". Make it's shape conical. Then make a transition that is 9.75" long and has a front dia. of 1.5" and a rear dia. of 4". Make it's shape ogive. You can add a shoulder, just like on a NC to the transition. You can put the fins on this transition.

 

[Frodo2801]

Hi guys, thanks for the help I adjusted everything and it worked. I still have to add 2.5lbs. of nose weight. The flight sim is 3095'. Check it out.

 

[CTimm]

Originally posted by Frodo2801
I'm trying to build a 1/3 scale AGM 12C Bull Pup. I've rocsimed .

It might just be my eyes, but the fins you've roc-simmed look a bit small.

Chris Timm

 

[hokkyokusei]

There seems to be something wierd going on here. I loaded the sim up with a J350, and it said it was stable, but the from the indicated reltaionshi between CG & CP, it clearly wasn't! It was nowhere near one calibre of stability.

 

[Stymye]

I would go by the rocsim values rather than the barrowman on that one.

 

[hokkyokusei]

Although better, the distance between CG and CP still doesn't look enough.

 

[Stones]

Originally posted by hokkyokusei
Although better, the distance between CG and CP still doesn't look enough.

RS takes into consideration the transitions.

 

[Frodo2801]

CTimm I think the trailing edge of the lower fins are about .75" too small but the rest seem to be correct. The fin span should be 16" the original was 48". I wil adjust that. Thanks for the look see.

 

[CTimm]

I just realized why the fins looked weird to me....
I've been photographing and measuring inert Bullpups for years and they've all been the "D" model and not the "C" model.
One main difference between the two is that the "C" model (shown at the USAF Museum) doesn't have a clipped wingtip like the "D" model (Eglin Armaments Museum).

The D diameter is 17.35".
If the C model is the same diameter, your scale ends up to be 1:2.818 using the 6.155 tube.
With a 48" real-life span, this makes each fin width 5.43" instead of the 4" in your rocsim file.

Assuming both C and D models have the same overall wing length, than the scaled length should be 15.875" and not the 9" you've simmed.

That explains why they look "small" to me.

Do you have actual measurements of the C model? (I don't, just the D model)

Perhaps a calculation cramp?

I remember the Launch Pad plan-pak with the rolled posterboard tubing having huge wings. I made mine out of foamcore!!!
Flew like a kite. Fell like a marshmellow.

Just trying to contribute something useful.

Chris Timm

 

[Missileman]

Not being able to look at the Rocsim right now and assuming you are refering to the main fins,
The fins on my Launch Pad kit are very near that size with a body tube dia. of 3.75"
I would say you need to rescale the fins.

 

[CTimm]

Heres a side view of the clipped-fin "D" version

 

[CTimm]

Heres a view from the balcony.

 

[Frodo2801]

Hey man those pictures are great. Those are the best pics I've seen any where period and I've spent about three hours searching the net try to find information on the bull pup. Did you say you have measurements on the D. I might change it to a D. I haven't started this rocket yet I like to get all my ducks in a row before I commit to a project.

 

[Frodo2801]

Check out the changes and see if they look right or clse I didn't have anything to go by just your pictures.

 

[CTimm]

Originally posted by Frodo2801
Did you say you have measurements on the D. I might change it to a D.

Yes I do. (did?)
I posted this info in another Bullpup AGM-12C thread awhile back, but here it is cut & pasted.

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???

Chris Timm

 

[CTimm]

Canards anyone?

 

[CTimm]

Stenciling....

 

[CTimm]

Originally posted by Frodo2801
Hey man those pictures are great. Those are the best pics I've seen any where period and I've spent about three hours searching the net try to find information on the bull pup.

Thanks.
The Bullpup C and D are pretty rare on the internet.

I've taken 1000's of photographs in the hopes of getting a few to turn out okay.

I've taken detail shots of the fin brackets and other nitty-gritty things, but those were film shots that need to be scanned in.

Chris Timm

 

[CTimm]

Originally posted by Frodo2801
Check out the changes and see if they look right

Looks pretty good for sport-scale!

Use the dimensions I posted and divide each one by 2.818 and you'll be there.

CTimm