Retro Rockets from the 50's

Onebadhawk
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PS- check out this finished model (not mine, I found this in the XL-5 Yahoo Group.)
 
Marc, thanks for the photo and links. I just looked at the tubes - It hadn't hit me that there really isn't much difference between 3 and 2.5 inches. This is a short distance over 6 inches-or-so of transition. This will limit the approaches that will be feasible.
 
hey - that foamcore XL5 looks pretty good. I wonder if it will finish out right - but going light on the aft end is a really good idea.

Regarding my XL5, its 29 inches long, and where the CG should be is a really good question. The tricky question is "where's the CP"? There's really no way to calculate it. An program like Rocksim will just look at you cross-eyed if you try to enter that shape. The cardboard cutout is going to be pretty far off too.

My seat-of-the-pants guess is that the CP is located at the front of the "reactor core", which means that the CG should be a bit ahead of where the wing joins the body. Of course, that will depend a LOT on how big you make the forward fins. Just a tiny bit bigger or smaller there will move the CP a LOT. So I don't think we can nail a CP or CG on the Fireball until we have determined an official blueprint.

- Steve
 
Steve,

Thanks for the response. I had hoped to find someone who had flown one, and could give a CG position that actually worked.

Personally, I'd be surprised if the CP was behind the tip of the rear fins. I made a Rsim design (Fireball XL-5 "Guestimator") to check the effects of the forward fins. I basically modeled four fins with the shape of the actual side wings. Without the forward fins, the CP was just at or behind the tips of the fins (depending on the calculation method. This is not far off of what you estimated. However, when I added the forward fins, the CP moved to roughly an inch ahead of those fins. (And my forward fins were not as far forward as the real model...an effect of my quick Rsim entry)

Please keep me informed if you run into someone who has an actual measurement form a working model. And good luck at Narcon!
 
I wrote a program where you could enter all fins, transitions and nosecones by themselves. It also uses the length- and the height-coordinate, so it could work with non-rotational-symmetric rockets like the Space Shuttle. I don't know whether the results it gave were correct, but the Shuttle flew without extra fins - it needs a ton of noseweight though.

Unfortunately I only have it in German, but I guess Babelfish will help you out there.

https://www.shuttle-endeavour.de/webimg/barowman.exe

Oliver
 
Oliver,

I tried the link and it appears it can't be found. I didn't try going back to the base page and looking for the right one due to the language issue. If you could please check and repost. It's always possible there's a temporary problem on one end or the other.

I will certainly give it a look-see if I can find it. Another "opinion" couldn't hurt.

Does your program handle fins that are offset from the main BT?

Thanks,
 
Hey, I found this pic while surfing around the web. It's called the Thunderbird 3. Is this a mock-up of a rocket from the Thunderbirds TV show?

Thunderbird 3
 
The problem was the server is Unix/Linux, and the file was named "BAROWMAN.EXE", since it came from DOS. I renamed it, so you can download it from the link above (which uses lowercase spelling).

When you enter a set of fins, it asks for body tube diameter too.

In W2K it may only show a black screen with the blinking cursor. Let me know how it works.

I may write a PHP version of it for everybody to use from a web browser.

Oliver
 
Attention all Fireball scale gurus!

I have a question about the larger 'pods' that appear to be under each side wing. It appears on the scale plans that the leading edge is a full cone structure (at least the tip of it). That would imply the pods are parallel to the body tube and taper towards the rear with the angle of the wing's surface? Or are they half a cone laid flat on this surface?

I have the wing components and tip of the NC done. Have to cut my tube (decided not to stretch the design), and build the transition. I'm going to try a cardboard/paper transition and see what happens.

Thanks for your help.
 
Well, here's the status of my model. Its pretty much together but still needs some sanding/filling. The side pods have been fitted but not installed. Reason for installing: can test fly it before I waste time painting it. Reason not to: think it would be easier to paint them first. I am basically painting-impaired, so I don't look forward th this step. Also still need to weight the NC. You purists will note several things that are not to scale, but it should be pretty close.
 
Wow man, it looks GREAT!!! really it does. How did you end up doing the transition? PS- my opinion is to go ahead and paint the side pods. It'll be a huger pain to do it after they are installed. And fromt he looks of it, your model is really turning out beautiful. I wouldn't want to denegrate its coolness by an "afterthought" paint job. You'll get a nicer finish if you paint the pods then attach 'em. That's my 2 cents.

Looks awesome!!! Can't wait to hear a flight report.

Marc
 
Thanks for the word's of encouragement guys!

I don't know how I'll paint the thing. Masking the curves will stress my capabilities. I was thinking that Monokote trim would work nice for the yellow stripes but I don't know about the pods. Suggestions will be welcomed here too.

Finally, I still am hung up on stability, having heard of one near disaster. My paranoia keeps pushing the CG forward and the weight up. I now estimate around the 2lb mark so I'm now thinking F50 or G40...or go for broke with a G80. I couldn't get Oliver's program to run, so I don't have that data point. Man, I REALLY want to get a measurement from a proven rocket!
 
Wish I could help you there. Have you given it a swing test just to get a ballpark idea of its stability? I know Rocksim is not much help because of the fin configuration and all the custom parts... I think between your weight and a swing test, you'll get a as-good-as-you-can-get guesstimate.
 
I will have to figure a way to temporarily (without 2-part foam!) hold the weight in the nose and rig a swing test. You're right, that's prolly the best way.
 
Dick, that model looks great. I am incredibly jealous.

I sympathize with your finishing woes, as I too, am "finish impaired." Tulanko and Marclee drive me nutso with their "40 leventy coats of primer blah blah blah....." I just can't persevere through all that.

I am also very anxious to hear about a flight report.
 
To piggyback on Ken's "eleventy coats of primer"... I would suggest you look into buying the silver metallic touch-up finishes sold at auto body supply stores (and on the Internet). You'll find they look much more realistic than the typical silver spray paints you find at home supply warehouses. Another interesting alternative is the newer Testors "Metalizer" finishes which require a few steps but look like real metal.

Your model is so nice that I'd hate to put anything but the best on it. And you know, I just bought stock in a primer factory and...well you know.

Marc
 
Marc,

I forgot to respond to your query about the transition. I wimped out and went with a posterboard wrap; didn't even fill it with foam.

As for paint, I was thinking about Krylon Original Chrome, since I have the good part of a can already. May not be enough but I can get more if need be. I'm also still leaning toward trim Monokote. I can use the template I used for the pod, which conveniently has the paint pattern on it - a benefit of printing it from the plans. Cover the leading edge with a strip and then lay on the side patterns.
 
I decided to go with trim Monokote for the red/yellow trim and picked up some Testors Stainless Steel for the main body, pending testing the compatibility with Plastikote white primer.

What I need now is suggestions for the 'XL5' lettering, and what color/finish to use for the cockpit(s) that in a plastic model would be clear. I've seen:

1. keep them silver and add black support outlines
2. keep the support outlines silver and make the 'glass' black

Any other ideas?

Thanks,
 
I picked up some plastic letters from a hobby shop - I think they're intended for R/C cars and airplanes. The font looks perfect, and they have all sizes in 1/8 inch increments.

I don't really have any good ideas for the window. I was thinking of painting it black and masking in the silver bars. Then while its still masked, going back into it with some dark blue and an airbrush to add some faux highlights. I don't know what it will look like. Haven't tried it yet.

Steve
 
The ones I got come in bags with two or three sheets inside, depending on the size of the letters. There's variable amounts of each letter on the sheet. Some letters have two copies, some three, etc. And it has numbers.

SR
 
Rstaff,

Here is a thought on the window. Go with clear and paint or tape the black stripes on it. you can print out a photo of the cockpit to place under the clear windshield for realizm. Now, for the question...how big would the glass have to be??? Here is why...

...it just happens to be Easter season. You could get some "clear" plastic Easter egg shells for holding candy that come in all sizes, or one of those "eggs" that has one side clear with the 50 cent toys in them you find at the market or department store exits. Just a thought.....

Carl
 
Here's photo of my Fireball showing its current. Finishing is complete except for lettering, stripes near cockpit and round 'portholes'. Oh, and I need to finalize the nosecone weighting. Since I am using old fishing weights, etc, I didn't try to optimize the ballance. I did a swing test with the CG around 2.5" in front of the side fins, and that worked just fine. That was with a G80.

I bought a G40 for it an I might even fly it this coming weekend. I need to get hold of my son's digial camera, which is currently away at college. I want some good quality 'before' pictures in case the 'after' aint so good. This will definitely be a heads-up flight!
 
Dick, that model is just too cool for words. Please please please try to get a lift off picture. I can just see her climbing out belching fire and smoke.....

Do you have plans? Parts list?

Incredabeautifulicious. Congrats.

- Ken
 

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