Looking for plans for Estes Attack Craft Orion #1374

I am already aware of the plans listed on the Ye Old site, but am having the same problem other cloners have mentioned for other projects. The file there has no scale indicated on the page, so once printed, there is no way to verify actual size. I know that a lot of these should be formatted to print out 1:1, but in my experience there's a lot of variation in that. This model is not shown on JimZ site, so no luck there. Does anyone have a scan or photocopy of the fin plans for the Attack Craft Orion, Estes #1374, that actually shows a scale on it?

Thanks.

Hi Rick - I have a built ACO in fairly pristine condition. If I remember tonight to go measure and post a couple of reference dimensions you ought to be able to scale the YORF sheet to print correctly.

OK, here ya go, measuring from my actual model:

Main wing root chord: 3.375"
Main wing tip chord: 2.0"
Main wing LE sweep dist: 2.2" (I think it was probably laid out as 2 3/16")
Main wing height perpendicular to root chord: 3.125"
Main wing leading edge length: 3.85"
Main wing trailing edge length: 3.23"

Strake root chord: 3.5"
Strake outer chord: 4.0"
Strake width: 0.5"

Main wing TE offset behind TE of strake: 0.50"

Vertical fin root chord: 2.25"
Vertical fin tip chord: 1.375"
Vertical fin height perpendicular to root chord: 1.94"
Vertical fin leading edge sweep dist: 1.5"

These look plausible...in the era when this was designed Estes tended to use fractional inch measurements for fundamental fin dimensions. The only surprising one is the vertical fin height. I measured both fins on mine and they are identically about 1/16" under 2" high. It's possible that I took them down a bit when match-sanding so I'd treat that one as a bit less definitive than the other measurements. Anyway this should be enough to let you get your printout pretty accurate.

View attachment Estes Attack Craft Orion fin planforms.ork

And finally...here's an OpenRocket file with the fin planforms according to the measurements given above. This is not a full OR sim of the model; it can't represent the actual fin geometry nor the nose cone.

Thanks for posting that. It looks like the fin patterns as printed are real close, at least within sanding variability. FWIW, based on that, the fin height on the pattern is an even 2", so maybe yours are sanded a little more than typical as you said. Either way, this is enough to get me started. I'll be building it with the modern version of the nose cone, so it won't be 100% acccurate. The new cone seems to have more detail and has a dome (an Astromech droid?) on the rear of the canopy that the original did not. But its close enough for me.

Could I ask one more favor? Can you give me an approximate CG location? Normally, I'd build a simulation in Rocksim to get an idea of CP & CG positions, but with this I have no idea what to do with the nose cone. All I can think to do is make sure it balances close to the original...

I am wanting to build one of these as well with the Asteroid Hunter nosecone. In fact, I have cut out all the balsa parts using the template from the Ye olde site a while back but haven't gotten around to starting on the model. I don't know for sure, but the Asteroid Hunter nose cone looks to be about 3/4" longer than the original Orion nose cone. I have been wondering if I need to shorten the body tube or will it be ok with the original body tube length?

I'm inclined to build it per the original tube length. Then, if I ever come across an original, I can swap it in. I doubt extra length (and nose weight) ever hurt a rocket...

Hi Rick,

I'll go measure the nose cone mass and my as-built CG location tonight. I can probably enhance the OR model I built to give a pretty accurate CG, though it will have no real clue about the CP since it's drastically different in the yaw and pitch planes.

Most fin patterns on YORP are standardized at 200dpi. You can use that to set the print size in programs like Gimp.

kj

More Attack Craft Orion details as requested

Mass of nose cone: 12.9 gm with paint, decals and a layer of masking tape to make it fit in the tube (shoulder is noticeably small)
Mass of overall model: 44.9 gm
Dry CG station: 3.75" aft of forward end of body tube (about 1-2mm in front of the point of the strakes).

Thanks for posting that. Interestingly, when I use that nose cone weight in my Rocksim file, I get a CG .25" farther forward than you have, even though I've already made the fins basswood. I'll probably need to account for all the glue and filler on those yet.

Mine is pretty well finished...so with the acreage of balsa I'd expect the filler and paint to bring the CG back a little bit from a more minimally finished one. But basswood is quite a bit more dense than the balsa so I'm a bit puzzled. Perhaps I'll play with my OR model later to get it mass-accurate so I can verify the as-built CG and then look at the effect of switching the fin material to basswood. I'm sure I'll have to put in a paint/fillets allowance to reach something like 0.1" accuracy in CG.

Edit for follow-up on the nose cone: I also have an Asteroid Hunter in work and I compared the AH nose cone against the ACO nose. Except for the cylindrical extension coming out the back of the wedge, the AH and ACO nose cone dimensions are identical. By sanding off the raised details added to the AH cone, filling any resulting holes, and cutting back the cylindrical extension, you can make a nearly perfect ACO nose. The only deviation is that in the AH tooling they clipped the back corners of the wedge a bit, so they would need to be built up somehow (I'd sculpt small pieces of styrene to the right shape) to get a 100% correct ACO nose. The last gremlin is that the Asteroid Hunter was on steep discount and is now shown as out of stock...it may be discontinued.

Isnt the AH cone in the scifi pack?

Good point about the SF pack. I'd get 'em while you can, chances are they made a fixed number of the parts and might not re-run them just to keep the NC pack in production.

I bought one of the AH kits when they were available cheap. I've also got a sci-fi pack on the way from Belleville Hobby, but since they're in a box with BP motors, it'll probably take a while. I intend to use the cone for my AC Orion clone as-is, since it isn't worth it to me to start modifying the cone. Instead, I plan build it as a "Block-2" model, which will account for the updates and some other minor changes I've made.

FWIW - Estes has the AH back in stock today, I just ordered another with some other stuff. Maybe I'll build a Block-2 Manta Bomber next...

I received my Sci-Fi pack from Belleville Hobbies last week, which came by slow boat since it was shipped with a box of motors. So, I was able to proceed with my clone. I didn't take any pictures of the build, so there's no build thread, but I'll post the final product.

As part of my "Block-2" thinking, I've made a few other changes to it, which include a belly-mounted lug on a stand off (an "ion cannon"), plus added underwing weapons stores. There's a cluster of "laser torpedos" under on side, and a "particle cannon" under the other. This adds to the Block-1 ship's quad turbo-lasers in the nose, and is further enhanced by a new sensor array in the nose, the "Strangelove Forward Array Targeting System" (or S-FATS), with fire-control handled by an Astromech droid in a socket behind the cockpit. The Block-2 craft is outfitted more for attacking capitol ships instead of dogfighting. Yes, I making this up as I go along and am drawing willy-nilly from multiple different sci-fi references.

Incidentally, my Sci-Fi cone pack switched out the Zarconian Cruiser cone for a second Interceptor cone. Which is fine, I probably wouldn't have used the deleted one, whereas I might find a use for the other. I was already planning a Vindicator clone (though Excelsior pulling the plug has cramped my plans), so I'll either clone a USS Pleiades, or maybe design something entirely different...

Rick, are these 1/8" or 3/32" thick fins?

Also, just for your imagination, I took one of the super cheap Photon Probe kits: (I have 3 more on the shelf good for parts at $8.)

• changed it to 3 sets of fins/strakes,
• threw the balsa away and hand cut TTW fins
• built the strakes up to the full 1/4 width by using 1/8" fore and aft of the TTW fins, then 1/16" on both sides
• 24mm MMT, an F39 in Rocksim states 2300 feet
• last but not least used the super long nose cone out of the SCI-FI pack. Not sure what model this nose cone was from but it looks cool!

Still building it, then a PSII Argent, and then this model.

I'm fairly certain that its 3/32 - or, at least that's what I used (but in basswood). I actually finished painting my clone last night, though there's a bit of detail work that I'm going to do with a brush yet. Then the decals, and only then will I photograph and post it. But its pretty cool already, I did a countershaded paint job that I then overmisted with a fine black spray...

Incidentally, along the lines you are talking about, if someone modified a Photon Disruptor (use the lower tube and T-fins) and combined that with the Orion/AH nose cone, they'll wind up with something more than a little like the Centuri Python...

EXPjawa said:

I'm fairly certain that its 3/32 - or, at least that's what I used (but in basswood). I actually finished painting my clone last night, though there's a bit of detail work that I'm going to do with a brush yet. Then the decals, and only then will I photograph and post it. But its pretty cool already, I did a countershaded paint job that I then overmisted with a fine black spray...

Incidentally, along the lines you are talking about, if someone modified a Photon Disruptor (use the lower tube and T-fins) and combined that with the Orion/AH nose cone, they'll wind up with something more than a little like the Centuri Python...

Click to expand...

Cool paint job, sounds sweet and your right about the Python. It is almost a direct copy. Thanks for the info.