Estes "Catalog" rocket. Anyone build one?

Not sure if this belongs in Scratch Built, Plans, or here but here we go.
You know that rocket shown in the Estes catalogs which is supposed to diagram the different parts of a rocket? Has anyone actually built one?


I think it would be kind of fun to build the rocket nobody notices.

It could work as long as the transition is hollow.

Would it be: BT20/50? BT50/55? BT55/60? 18mm? 24mm? Mini?

Thoughts?

I think it would be a fun build.

In the interests of irony, build it entirely out of non-Estes sourced parts. Balsa Machining, eRockets, Sunward... Just because...

As drawn I'd say the bottom sections are BT-50 and the section above the transition is BT-20. This is based mainly on the illustration of the green centering rings which look to be AR-2050s. You'll have to hollow out the transition to get that parachute out....and getting the 'chute out of BT-20 is always a bit of a pain.

Also odd to put a launch lug on the booster and not on the sustainer....

Appears to be BT20/50 based on the text below as well however I suppose it could be anything. I think the Estes Designer Special should have the perfect hollow BT20-50 transition. Otherwise drilling through a balsa one could make it quite weak, but then I suppose CA might fix that...

I've drawn up a quick approximation in OR. It's marginally stable as a 2-stager. With a tiny bit of nose weight, 3-4g or so, then it's stable at 1.0 to 1.2 cal. A B6-0/B6-6 combo sims to 1100'

Cabernut said:

I've drawn up a quick approximation in OR. It's marginally stable as a 2-stager. With a tiny bit of nose weight, 3-4g or so, then it's stable at 1.0 to 1.2 cal. A B6-0/B6-6 combo sims to 1100'

Click to expand...

...speaking of, what does "cal" translate to in terms of real-world stability? What's a good minimum?

ActingLikeAKid said:

...speaking of, what does "cal" translate to in terms of real-world stability? What's a good minimum?

Click to expand...

One caliber of stabilty is one body tube diameter between the Center of Gravity and the Center of Pressure, on a 1" diameter tube the distance is 1", 2 cal.=2", etc. One caliber is considered stable and 2 is considered overstable by my understanding, overstable rockets are more susceptible to weathercocking. I aim for a stability margin of one, however short fat rockets fly well on less.

I've found that squirrelly things sometimes still happen if the stability factor is down around 1:1, I usually shoot for the 1.25-1.5 range just to be sure. I'd rather add some nose weight and not go quite as high to be sure of a good flight than have the rocket do a corkscrew and come back at the crowd...

Incidentally (not to derail), there is another "parts rocket" that's shown in the catalogs in the mid-80s. This is actually what I was expecting to find when I first read this thread. This one was more sci-fi like, like a lot of the kits they were making at the time. I modeled it in Rocksim as accurately as I could:





It's worth noting that a quirk in the 3D rendering has the blue side tubes flipped on the Y-axis (see the 2D images). Also, the nose cone shown in the catalog image is actually the PNC-50SP, which is the canopy version (from the Falcon Commander, etc). The canopy isn't reflected in this model, but would be if (when?) I actually built it. I created the Rocksim file assuming that it would be 24mm, so there's a bit of nose weight in it to allow for an E9, which didn't exist in the mid-80s. In fact, Estes probably would've used an 18mm mount...

Awesome! I may have to try this one as well.

Let us not forget the legendary Estes SPEV which was a parts vehicle that actually got kitted. (Spare Parts Elimination Vehicle). Not exactly the same as a catalog illustration model but in the same vein. Photo link is from HCMBanjo's blog.

When you said "catalog rocket" I thought you meant this one from the 1969-70 catalogs:

I'm pretty certain that at least that one is an early draft of the Cherokee-D, before it was actually in the catalog officially.

I just got a Designer's Special. Working on drafting up my first build with it now but this would be a fun one to do next.

Here's an .ork file that I drew up from careful measurements of the page scan. Scaled to BT50/55 which seems to fit better with 70mm long engines.
If anyone has the parts, have at it!



View attachment Catalog_BT50-55.ork

That looks good; I changed the fin material from default cardboard to lighter balsa, which brought the stability up to 1.18cal, and added a motor block to the sustainer section with no ill effect on CG. The plastic nose block shown in the drawing will probably have to be made out of a standard coupler, which is no big deal and shouldn't detract from the spirit of the design. I also agree on the BT-50/55 sizing, as a BT-20 payload section wouldn't be good for much.

Now, I'm assuming that this is a 2-stager, since the drawing shows two mounts. I'm curious as to why they put the launch lug on the booster. What combination of motors are you assuming to grade the stability, and which tube diameter is the factor based on? It is proportionally kind of stubby, with the sustainer fins pretty far forward in relation to the proportions. It seems like nose weight of some sore would be mandatory...

Good call on the nose weight. The BT50-55 version was ~1.0 cal for stability with a pair of heavy D12s - which is technically "OK", but is kind of iffy considering OR isn't perfect. If I were building this, I would feel more comfortable with about 7g of clay in the nose. The altitude doesn't change much(+/- 20ft) with the nose weight but the stability increases to about 1.6 with D12s and 1.9 with C11s.