Starcraft Wraith

[EchoVictor]

I was chatting with a friend of mine, lamenting the fact that I haven't found a cool computer game to "get in to" for a while. So, she loans
me her copy of the popular RTS game "Starcraft". I put the disc into my PC, and up pops the install utility menu, complete with game art
backdrop. That's as far as I got..... :D

You see, in the background of the start-up utility is a picture from what I'm guessing is one of the in-game cut scenes. On this background
is a 3/4 view of a really cool-looking, "vulture"-winged fighter. I instantly knew I had to turn this puppy into a rocket.

A little bit of Google and Yahoo! searching (gosh I love the internet!!!) and I found these pictures of the Starcraft "Wraith".......

http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/SCFleet.jpg
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/SCWraith1.jpg
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/SCWraith2.jpg
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/SCWraith3.jpg

Next up, build pics!

Later,
EV

[EchoVictor]

Alright,

so I do a little bit of drawing/tinkering in PowerPoint, and I come up with using a BT-60 and Bertha cone for the main body. Right now I'm
starting with 9" long, but I can always cut it down to the 7.5" Baby Bertha length after the swing test. The bottom wing cannon is a BT-50
at the standard 2.75" motor length, and the upper wing cannons will start with BT-5's. I also decided to go with BT-5's for the rear stabilizer
booms.

Here's a shot of the tubes on top of my fin alignment guide;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/536c37fb.jpg

Next up are the wings. The bottom one is pretty straigtforward, but the uppers have an odd dihedral. To get the look I wanted, I settled on a
20 degree angle for each, making the dihedral a total of 40 degrees between the two wing surfaces.

Here she is with wings mounted;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/80ec6423.jpg

For the cannon housings, I just mounted a 24mm motor tube onto the bottom wing. For the uppers, I had a couple of 2" long BT-5 sections
with little winglets rolling around in the spare parts bin. Perfect!

http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/c17b6a34.jpg

Well, it was getting late last night, so I quick mocked up what the cannon will look like. The bottom one is simply a section of BT-5, while the
uppers are a couple of spare little tubes I had laying around from somewhere.

http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/509b4afc.jpg

More to come tonight!

Later,
EV

[CPMcGraw]

Alright,

so I do a little bit of drawing/tinkering in PowerPoint, and I come up with using a BT-60 and Bertha cone for the main body...

(Lots of great text and photos snipped for brevity...)

Eric,

Nice job on the Wraith. It's a shame this is one of those designs that cannot be accurately rendered or simulated on RockSim without forcing it to do odd things.

How are you going to balance the asymetrical fin arrangement?

[EchoVictor]

I really hadn't given that much thought. I mean, I know that the mass and drag is going to tilt it towards that bottom wing, but enough to really mess up the flight path? I dunno....

Thinking out loud here, I suppose I should try and balance with some sort of drag on the top of the airframe. I guess I could put a little "air brake"-type plate up there, kinda like what's on the top center of an Estes Strikefighter.

What about moving the engine mount off-center in the body? (Use a 2x18mm into BT-60 cluster ring and block off one half, placing the motor at the root of the bottom wing?)

Later,
EV

[CPMcGraw]

Thinking out loud here, I suppose I should try and balance with some sort of drag on the top of the airframe. I guess I could put a little "air brake"-type plate up there, kinda like what's on the top center of an Estes Strikefighter.

What about moving the engine mount off-center in the body? (Use a 2x18mm into BT-60 cluster ring and block off one half, placing the motor at the root of the bottom wing?)

Since you've already glued the wings in place, the addition of some form of drag-inducing item to the top of the model can adjust the final flight path in a pleasing way. You want the model to fly with that one central fin/pod down toward the ground as it gently arcs over. Perhaps something similar to the Orbital Transport's boxy motor shroud, mounted on either one or two pylons directly opposite the central fin. Keep this as light as possible; you're not really looking for altitude performance here, just a really spectacular flight, but there's no need to build it like a battleship, right? Some 1/16" balsa should be sufficient.

I don't know if this can be rendered in RockSim, either. But I think you get the general idea...

[EchoVictor]

Well, the build is pretty much complete. I may add a detail here or there, but this is the main form.

Front 3/4;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0240.jpg

Rear 3/4;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0241.jpg

and a close up of the wings/tail boom area;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0242.jpg

I did a swing test with a C6-3 in back, and she passed with no additional nose weight. I hope to fly her this weekend on a B6-4 at first.

Later,
EV

[CPMcGraw]

Looking forward to a flight report, EV.

[Green Dragon]

Really neat looking bird.

( Of course you'll be posting the plans at BARclone, right ? :) )

~ AL

... I'd hate to meet up with that in space , it's packin some heavy-duty artillery......

[EchoVictor]

Well, the Starcraft Wraith had her first flight last weekend.

Here she is on the pad....
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0256.jpg

and here's lift off.
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0257.jpg

The first flight was on an A8-3, and it was, how shall we put it, "not pretty". She did a complete parabolic arc to about 50 feet up
and came down nose first under power. The ejection charge fired while on the ground. I just didn't have the heart to photograph the
wreck. There was however, surprisingly little damage. Both wings were sheared off at the dihedral, and that was about it.
Next step is to add some nose weight and try again....

Later,
EV

[EchoVictor]

2nd flight Update:

Flew her this afternoon on a B6-4. Exact same (poor) results, except this flight was only about 20 feet up and landed 15 feet from the pad. Luckily, no damage this time. The flight arc was again in direction of the lower wing, so that's definitely the problem.

Potential idea for stability is tilting the rear fins downward at the end of the BT-5 booms.

Later,
EV

[Ramjet]

2nd flight Update:

Flew her this afternoon on a B6-4. Exact same (poor) results, except this flight was only about 20 feet up and landed 15 feet from the pad. Luckily, no damage this time. The flight arc was again in direction of the lower wing, so that's definitely the problem.

Potential idea for stability is tilting the rear fins downward at the end of the BT-5 booms.

Later,
EV

Sounds and looks to me like the problem is more the weight of the lower pod/fin not being balanced. Try taping a string to the tip of the nose and see how it hangs. I bet it hangs canted with that pod downward. Balance it with weight first, then drag if it's still needed. Or offset your motor mount to get the thrust through the center of gravity.

Ramjet

[EchoVictor]

^Bump^

After my poor second flight results, I tried to do a little tinkering with the rear stabilizer fins. First, I cut 'em off;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0530.jpg

Then I re-glued them on with about a 10~15 degree down angle;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0538.jpg

Third flight was a few weeks ago on a B6-4 with the same nasty results - 50 foot arc in the direction of the lower wing, and lawn-dart under power. As with the first try, the wings sheared at the dihedral.

She'd been sitting in my range box in pieces for weeks, but after taking some good-natured ribbing about the poor performance of this one in another thread (ahem, PAUL, ahem :rolleyes: :D ), I figured I might take another look at her....

I repaired the wings (AGAIN), and my next plan was to move the motor tube from being centered in the BT-60 to offset. Upon close inspection, I wound up not having to do any cutting, as the third launch/power prang had loosened the engine mount up enough where I could just push it up through the top of the body tube.

Well, a little cutting on some matte-board, and I had two offset centering rings;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0785.jpg

Here it is installed;
http://i73.photobucket.com/albums/i204/EchoVictor/Rocket%20Stuff/100_0790.jpg

Any bets on how she'll do now? :D

Later,
EV

[Daniel Runyon]

Man, I sure am glad some of these old design threads are getting resurrected... that is one spectacular looking ship! Very interesting watching the progression of hacks to get this to fly right... awesome!

[CPMcGraw]

Any bets on how she'll do now?

If this helps, but still doesn't solve the problem, you might have to try a vectored motor mount. The thrust angle may have to be "tilted" to compensate for the excessive drag from the large pod.

[handeman]

If this helps, but still doesn't solve the problem, you might have to try a vectored motor mount. The thrust angle may have to be "tilted" to compensate for the excessive drag from the large pod.

That was my thought too.

As for bets? 3 to 7 she flies straight enough to get a chute out.

[Solomoriah]

Get an expended engine casing. Run a string through the nozzle; put a knot in it so it doesn't come out. Put the casing in the engine mount (friction fit if you don't have an engine hook) and hang the rocket upside down by the string from the nozzle.

If it hangs straight down, the engine mount is lined up with the center of gravity.

Of course, this doesn't account for drag...

[barone]

Get an expended engine casing. Run a string through the nozzle; put a knot in it so it doesn't come out. Put the casing in the engine mount (friction fit if you don't have an engine hook) and hang the rocket upside down by the string from the nozzle.

If it hangs straight down, the engine mount is lined up with the center of gravity.

Of course, this doesn't account for drag...Great idea! :) (You gotta love this forum....so many ideas.)

[handeman]

Great idea! :) (You gotta love this forum....so many ideas.)

You got that right. Never thought of that one.

[EchoVictor]

Well, after the multiple attempts documented here, we have......

SUCCESS!!! :D :D :D

Finally, after three fin-shattering crashes, the Starcraft Wraith actually flew this weekend on a B6-4. The flight wasn't the prettiest thing in the world, with a whole lot of tail wiggle, but she got a good 300' or so of altitude before coming down nicely under 'chute.

I'm not sure if the wiggle was from the high amount of wind at take-off, or perhaps from the 15 degree down-angle I had added to the tail stabilizer fins. Next step is to try it on a calm day. If I still have the tail wiggle, I'll put the stabilizers back in their original position.

Later,
EV

P.S. Given the mutliple cracks visible on the fins and the slight dent now present in the plastic nose cone, my brother has given this one the nickname of "Lumpy the Pit Bull".....

[CPMcGraw]

Well, after the multiple attempts documented here, we have......

SUCCESS!!! :D :D :D

Finally, after three fin-shattering crashes, the Starcraft Wraith actually flew this weekend on a B6-4. The flight wasn't the prettiest thing in the world, with a whole lot of tail wiggle, but she got a good 300' or so of altitude before coming down nicely under 'chute.

I'm not sure if the wiggle was from the high amount of wind at take-off, or perhaps from the 15 degree down-angle I had added to the tail stabilizer fins. Next step is to try it on a calm day. If I still have the tail wiggle, I'll put the stabilizers back in their original position...

It was more likely wind and a nagging thrust-vectoring issue. Give consideration to yet another prototype, and introduce about 3-5 degrees of angle into the motor tube. It sounds to me like the previous changes are getting close to "ideal".

Keep plugging at it. It sounds like an interesting model is about to come out of this ordeal...