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-   -   Estes Bullpup 12D (http://www.oldrocketforum.com/showthread.php?t=8049)

Brain 11-07-2010 09:42 PM

Estes Bullpup 12D
 
Bought this one a while back from Michael's, half price... and I've pretty much got half performance out of it (or less).

The instructions explicitly direct you to use ALL of the pack of weight clay that comes with the kit, which I did, following the instructions for doing so.

First launch: Quest B6-4
It manages to clear the launch rod enough to arc over and bury itself in the ground 20' away.
Only real damage is to the parachute (when it ejected while buried). I had responses on this forum split between whether the weight needs to be in the nose cone or not. I was told to be sure the clay had not come loose in the NC. It had not.

I tried a second launch on a later date (Quest C6-5), and got it to go OK into the air, but it arced over and came down in the neighboring golf course. Once again, no damage.

I have e-mailed Estes about this a week ago and have heard nothing back.

Now, as I sit here trying to put the Bullpup back into operational order, I discover that the NC weight clay has started to dry up and coming out of the NC in chunks. In fact, it may have started out MELTING out of it because the 'chute cord/shock cord knot is covered with the stuff.

So, given all this, what would you do?

chrism 11-07-2010 10:08 PM

Remember the good ol' days when Estes used those lead discs as nose weight?

blackshire 11-07-2010 10:10 PM

In addition to checking the clay ballast, I'd check the alignment of the Bullpup's forward (canard) fins. The rear fins (which function as wings on the full-scale missile) are far enough forward that the model is probably not far from being neutrally stable, which would give the canard fins more "control authority" than they would have if the rear fins were mounted at the rear end of the model.

If one or more of the canard fins are crooked, straighten them if you can without damaging the nose cone. If they aren't crooked (and even if they are, and you straighten them), adding small spin tabs to two opposing rear fins (or to all four rear fins) to make the model spin during ascent should make it fly stably.

Shreadvector 11-08-2010 07:06 AM

Excellent advice from Blackshire. Those fins can be a problem.

Forward fins can deflect the flight path severely.

Aft fins need to be in the correct location at the aft end (if too far forward, the rocket is unstable), and they need to be straight. Crooked fins can make the rocket arc over or do loops.

ALL the clay needs to be up at the tip of the nose cone. If it melted, then it was exposed to some pretty high temperatures. If you store your rockets somewhere wheer it gets crazy hot (like leaving them in a sealed car in desert heat), then make sure they are stored nose down. You can also seal the clay in the tip by pouring in a tiny amount of glue (epoxy) and stnding it upside down while it dries or cures.

The BullPup was quite unstable without the extra clay weight. They originally had 1 butter pat of clay and they increased it to 2. Did you have 1 or did you have 2?

And the Quest Chinese C6-5 is actually a C3.5-5, meaning the average thrust is very low. it burns for a LOOONNNGGG time which is great for lightweight rockets, but it is not so good for heavier models as they will tend to arc over under the low thrust.

Here are the old instructions wiht one butter pat and the current instructions with 2 butter pats of clay:


http://www.spacemodeling.org/JimZ/e...12D/est1972.pdf

http://www.estesrockets.com/assets/...Bullpup_12D.pdf

jeffyjeep 11-08-2010 07:53 AM

Quote:
Originally Posted by blackshire

If one or more of the canard fins are crooked, straighten them if you can without damaging the nose cone.

Are the canard fins supposed to be mounted ON the nose cone?

Ltvscout 11-08-2010 08:04 AM

Quote:
Originally Posted by chrism
Remember the good ol' days when Estes used those lead discs as nose weight?

You can still get 'em from Semroc.

Shreadvector 11-08-2010 08:08 AM

Quote:
Originally Posted by Ltvscout
You can still get 'em from Semroc.


Yeah, but they were for use with balsa cones and screw eyes. The clay is used inside hollow plastic cones, and by putting it up at the tip, instead of back on the base of the cone, you move the c.g. forward with less mass.

And plasticene clay is not poisonous.

Shreadvector 11-08-2010 08:11 AM

Quote:
Originally Posted by jeffyjeep
Are the canard fins supposed to be mounted ON the nose cone?


Not according to the instructions (and I posted both sets of instructions already....).

Shreadvector 11-08-2010 08:13 AM

By the way, one of the most common sources of unstable flights in a Bullpup with all the clay installed and with fins in the proper location and straight is a motor mount installed too far aft or a motor not installed all the way in the rocket.

We need detailed photos of the rocket to diagnose the problem(s). including a shot showing the motor installed.

Ltvscout 11-08-2010 08:13 AM

Quote:
Originally Posted by Shreadvector
And plasticene clay is not poisonous.

I'm not suggesting people swallow the lead!


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