The Coaster Dynasoar Centauri: an early mid power boost glider with R/C potential.

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tab28682

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I ran across some information on the old Coaster Dynasoar Centauri boost glider model, produced by the Coaster Corp. in 1962. The design alluded to some possibility of it being flown RC on some of the old Coaster black powder motors, as an sentence in the corner of one of the old ads said: " You can radio control this one!". Evidently a couple of people tried over the years to make it work as an RC model, but could not as they evidently all pranged. Appears it had a boost CG issue.

Someone here on TRF did a successful free flight version at 2/3rds scale, for 18mm motors.

26" long, with a wingspan of about 15.5". Airframe is a 2" ID tube. Balsa nose cone

George G. has some history on the design, plus copies of the plans on one of his RC Rocketry pages, here: https://georgesrockets.com/GRP/GLIDERS/EarlyRC/FirstRC-preview.htm

Attached pics from George's pages.

The plans are a real draftsman's work of art. Seems a real shame that there is no documented evidence of one ever being flown successfully with R/C. An R/C build about 12 years ago petered out with no flight report over on YORF.

I think I am going to rearrange my production schedule so that after the Mizuno Shinryu is finished and do one or two of these, next. One for sure in Depron for an E6, hollow balsa nose cone (will have to turn one to match the drawing) and with the correct tube from BMS, a T204-34.

I might even do one with the flying surfaces in balsa, per the original, with 1/4" balsa wings and 3/16" balsa fins.

Would be fun to make one work with R/C, as envisioned, 58 years later.........
 

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aerostadt

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I remember seeing ad's for this model about 55 years ago. I had a few Coaster motors. The Coaster BP F-motors had quite a kick and reminded me of the Centuri BP F-motors (Min-Max motors?). I can't help but think that there extra fins in the design that could be removed to save weight. There is some more information in the TRF Gallery on this model.

 

tab28682

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I remember seeing ad's for this model about 55 years ago. I had a few Coaster motors. The Coaster BP F-motors had quite a kick and reminded me of the Centuri BP F-motors (Min-Max motors?). I can't help but think that there extra fins in the design that could be removed to save weight. There is some more information in the TRF Gallery on this model.

Zero doubt that the original model has too many fins and other parts...:) The design appears flawed if they really expected it to glide after ejecting a spent 29mm motor casing. Balanced for stable boost with that motor weight, it would be insanely nose heavy after ejection.

However, I am going to honor this vintage design and make it look, externally, just like the original for historical reasons. I think a 24mm motor is plenty for this thing.

The gallery did not really have anything on the original design, other than a scan of the drawing. It had a scaled down FF version and the Semroc mini (non-gliding) version in there and that is about it. Lots more info on George’s page linked above.

Anyone know the specifications of the old Coaster BP motors? Might have to ask that over in propulsion. The plans mention 20, 30 and 40 pound thrust motors.
 
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aerostadt

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Rocketguy101 reported that the Centuri Mini-Max F-motor was about 7.75" long on this TRF thread.
Rocket Reviews reports that the Mini-Max F-motor was derived from the Coaster motor, which I find as believable because I had both and they were very similar.
 

Ez2cDave

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Rocketguy101 reported that the Centuri Mini-Max F-motor was about 7.75" long on this TRF thread.
Rocket Reviews reports that the Mini-Max F-motor was derived from the Coaster motor, which I find as believable because I had both and they were very similar.

Some pics . . .

Dave F.

1a.jpg




Cstr_MMX_EJ_SSRS_3.jpg
 

tab28682

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Thanks for the engine pics.

Ordered the Centuri ST-20 equivalent tubing today.That will give me all needed parts except for the nose cone, which will have to be turned from balsa, or perhaps printed.

Unlikely to start one of these before retiring at the end of the month, but progress should be rapids after that.
 

tab28682

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High impulse F motors like the Coasters mentioned seems like maximum overkill for a boost glider of this size. But, that was what they had to work with, I guess. The big heavy Fs are just not compatible with the CG needed for this thing to boost and then to glide, as a free flight. Would have had to have a pop pod with serious nose weight exiting the model at ejection to have a chance.

My Depron version will do well on an E6. I would expect the balsa version that I am also planning will do very well on an E15 or thereabouts.

George G. did some very intelligent analysis of this vintage design over on YORF. See post 150 on this thread.

 

burkefj

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Tom, the estes PS-II 2" tubing is a press fit into the ST-20 tubing from BMS, what I did for my upscale scissor wing transport was to cut a piece of PS-II tubing to the length of the shoulder of the PS-II 2" nose cone, glue it onto the shoulder of that cone, and cut a small piece of ST-20 tubing 1/4" long to glue onto the front of that PS-II piece to make a "stop" for the cone to not slide into the tube, it leaves a very small step at the tubing/cone interface but the parts are only a few dollars from estes and they are strong and lightweight, you won't have to turn anything and the PS-II tubing into the ST-20 tubing fits perfect. It won't be scale to the original but it will work in a pinch, or if you can find a balsa cone to fit the PS-II tubing you can do the same thing.

Frank


Thanks for the engine pics.

Ordered the Centuri ST-20 equivalent tubing today.That will give me all needed parts except for the nose cone, which will have to be turned from balsa, or perhaps printed.

Unlikely to start one of these before retiring at the end of the month, but progress should be rapids after that.
 

tab28682

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Tom, the estes PS-II 2" tubing is a press fit into the ST-20 tubing from BMS, what I did for my upscale scissor wing transport was to cut a piece of PS-II tubing to the length of the shoulder of the PS-II 2" nose cone, glue it onto the shoulder of that cone, and cut a small piece of ST-20 tubing 1/4" long to glue onto the front of that PS-II piece to make a "stop" for the cone to not slide into the tube, it leaves a very small step at the tubing/cone interface but the parts are only a few dollars from estes and they are strong and lightweight, you won't have to turn anything and the PS-II tubing into the ST-20 tubing fits perfect. It won't be scale to the original but it will work in a pinch, or if you can find a balsa cone to fit the PS-II tubing you can do the same thing.

Frank
Hmm. good idea and I might go that route to avoid turning a balsa nose cone. Good to have options.
 

georgegassaway

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As for the original Coaster kit, my conclusion is that there is no evidence that anybody EVER tried to fly it by R/C. What I wrote on my website:

"There were some references to flying it by R/C, but curiously no reports of one ever flying successfully with R/C. Perhaps one of the things that supported this over the years was an advertisement in American Modeler Magazine, from August 1962. The upper right side of the ad said "You Can Radio Control This One!". Well, maybe somebody could have, but it seems nobody at Coaster ever did. The actual plans do NOT show how to convert it for R/C."

Take note that R/C gear was incredibly heavy in 1962. Servos? Forget it, they were "bricks", as were the receivers and batteries needed. The only theoretical R/C that could have been tried was rudder-only Pulse R/C, which indeed was the kind of R/C used in the earliest recorded actual R/C boost gliders in the late 1960's. The earliest known successful one was by Doug Malewicki in 1967, using a decidedly "normal" looking hand-launch style of glider with a front engine pop-pod added.


I look upon the Centauri Dyna-soar as a pretty crude early attempt at a "high power" boost glider, as in E to F power in those days. Heck, I didn't even find a record of anyone flying one successfully at all as non-R/C in those days. You would expect a kit to at least have worked for the manufacturer when they tested it. Assuming they tested it. Which, I dunno, might not be a great assumption.

Personally, I have zero interest in ever building one. I would like to see video if someone does manage to get it to fly successfully, as in boost up and glide down. And I am not even talking R/C, I mean free-flight.
 

tab28682

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I agree the anecdotal reports on an attempt or or two flying it by RC are suspect, due to the near impossibility of radio controlling an elevon controlled model with contemporary equipment. Barely possible that some one might have tried to add pulse rudder to attempt to steer it, keeping the elevons actuated at ejection. Who knows?

As you likely know, someone posted here on TRF a 2/3 size downscale free flight that is as reported to fly well. Nothing wrong with the basic aerodynamics of the design.

Seems logical that a full size F version would work, but not as is, using a heavy F motor. Too much of a CG issue. It could be made to work with a heavy pop pod, but that is a major change to to original design. Also, that thing would get hard to see at possible full F altitudes.

Despite the designed in flaws, it it (to me) a very interesting early (in fact, the first, apparently) mid power boost glider design that envisioned the kind of RC rocketry we are doing now. The RC reference in the ad and in the plans was much more concept and marketing hype than reality. I think it will be fun to make one work with in a modern way. I really like the vintage styling of the thing.

It was an overreach, too much, a number of years too soon, but they got the concept right.
 
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tab28682

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Well, its a good thing that I am not starting this for a couple more weeks. My ST-20 tube order was picked up by the post office at E Rockets almost a week ago and tracking still shows it sitting at at vendor.

Good thing I am not is a big hurry.

I did cut out some depron parts for the E6 RMS RC version of the Dynasoar Centauri the other night, when it was too darn cold to go out in the shop and sand out the Type II wings.
 

tab28682

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Did some work on the Japanese rocket plane today, but it is held up for the arrival of servos and a decision about doing a cockpit and clear canopy, or just painting the canopy.

Always like to have few projects in work at the same time. I had made up templates for the wings and fins for the Centauri and cut them out of 6mm Depron last weekend.

Built up the tubes to final length with homebrew couplers. The 2" tubes recently arrived late after a tour of a few unexpected USPS facilities.

Printed out a 6 fin alignment template from payloadbay.com and made a cardstock template. Laid out the slots on the tubing and cut out the two wing slots and the four fin slots. Seemed like a lot of slots.

Managed to get the model framed up, hinged and the motor mount installed during the afternoon. I stuck a (faintly undersized in diameter) 2" PSII nose cone on itto see what it looks like. Working on getting a correctly shaped nose cone 3D printed, but I kind of like the looks of it with the long PSII cone, as well.

Servos arriving for this model this week as well.

Looks like this model will need some small rail button standoffs, as the gaps between the fins at the surface of the tube are a little narrow for the rail.

More to come.
 

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tab28682

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Have made more progress on the Centauri.

Did nearly no modeling for about 10 days while the extreme winter storm was going on here in Texas. Had no power for about 7 days, which puts a crimp in modeling...:)

The Centauri is now complete except for the custom nose cone and the windshield and window graphics, which will need the cone to be completed.

Decided to style it a little like a fictional SSTO spaceship from the 1950s and gave it some fun space liner markings. The temporary nose cone is a PSII 2” cone.

It also looks pretty good with the Interceptor E cone.

Will have to add a little bit of reinforcement to the lower fin tips to keep them from getting ground down when landing.
 

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burkefj

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I like your color scheme and I think it looks much nicer with the long pointy cone, the pictures of the original version with the markings and original cone don't look near as nice as your version imho
 

tab28682

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I like your color scheme and I think it looks much nicer with the long pointy cone, the pictures of the original version with the markings and original cone don't look near as nice as your version imho
Yep, I agree. It might get flown once with the historic cone, if I can ever get my buddy to print it. Should come soon. I have also ordered a 2” version of a PNC-20B/72606 which is a better looking blunt cone that I might use as well.
 

tab28682

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The 3D printed nose cones finally showed up for the CDC.

I liked the shape of this upscale PNC-20B the best, but it was a little too short for my taste. Luckily, it had a very long shoulder, so I added a 1.1” wrap of .020 polystyrene sheet to the base of the cone. This modified cone gives the CDC a nice overall look and keeps the fineness ratio attractive, IMO.

Even with the added wrap, the ABS printed cone weighs in at a a nice light weight of 17 grams. Body filler and paint will add a little.

Headed outside with the body filler, sandpaper and primer now.
 

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tab28682

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Finally had a few hours to finish up the Dynasoar Centauri and two other RC RGs yesterday and today. (No relation to Dynasoar Rocketry) Not having as much free time after retirement as I thought there would be....:)

It is now ready to test glide and launch. DX9 is fully programmed with two flight modes, boost and glide. I might still had a few atches and some more panel lines.

Nose cone is a 3D printed ABS cone that a buddy printed for me. There are basically no nose cones available for the Centuri 2.04 OD that I used since it was what the original used.
I cound not stand to put the blunt original cone on it, so did one in CAD using the “that looks about right” design approach.

Had some fun with the markings.

The second pic shows the result of the weekends work: the Dynasoar Centauri, the Athena and the Dynasoar Rocketry Avro Vulcan.

Hope to put the first flight on all three this coming week.
 

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burkefj

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Looks great Tom good luck on the maidens
 

tab28682

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Flew the Coaster Dynasoar Cenaturi yesterday. All went very well. Was hard to get the CG aft enough for a good glide due to the long nose. Even moving the rx and battery back to the rear was not quite enough.

Excellent boost to a good altitude and a decent glide to the runway. Ran out of elevator in the flair due to the fairly small control surfaces of the original design and the slightly nose heavy condition.

Will tweak the CG and it should do great.

Have what should be great video and stills coming soon!

At last, there has been a successful RC flight of a Coaster Dynasoar Centauri!
 

tab28682

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My photographer buddy Richard Ng sent over some photos of the Dynasoar Centauri from it's maiden flight in Little Rock, AR at SMALL in early June.
As mentioned previously, it was a little nose heavy, even with the RC equipment placed well back, partly due to a slightly overweight 3d printed nose cone. At landing, the long/tall fins touch first, which bounces the tail up and the nose down, as you can see in the photo. The original design had a landing skid made of small diameter music wire a little ways aft of the nose cone, and I may have to adopt that.

Will fly the CDC one more time stock, with the CG moved aft with more equipment adjustment and a bit of tail ballast. After that, I plan on making the elevons slightly larger. The original design, as previously mentioned, was very challenged by the design CG location for boost, which would move well forward once the motor ejected and left the model. I think the design could be nicely improved with a larger wing, perhaps with a strake going forward, and, as mentioned, larger control surfaces. I think it could be done without a large impact to the overall look and style of the model.


Going to fly it again with the CG moved further back, and I predict I will mod it a bit, by increasing the size of the elevons. Note the large bounce on the landing photo, the fin touch first and rebound, then the
 

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Aeronerd

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Nice job! Heard the original was a complicated design & build that was hard to trim & wasn't too good a flyer. Your rebuild is much more successful.
 

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