Thanks to my lovely family who got me enough foam, and electronics to make another rocket glider. They also gave me a half a day repreive yesterday and today to work on it. I've been wanting to try a spaceship one , but have been worried about CG, twisting and stiffness of the tail booms. It came out ok, I wound up having to put some parallel stiffeners on the bottom of the wing to help prevent twist.
I couldn't find a decent 3-view that I liked or thought was right, so I just did this freehand from a book I have from pictures and relative sizing. I think it captures the look if not perfect scale. The full flying control surface placement was dictated by the fact that I wanted to put the pivot rod accross the fuse and tie it in just in front of the rocket motor mount. This helps reduce the twist of the tail booms and worked well, and actually came close to where they are supposed to be. Since I was doing a cruciform structure, I had to move the wing placement to the middle of the fuse instead of the upper portion, but I don't think it makes that big of a difference in look. I did not add the later stub strake fins in front of the control surfaces yet till I fly it and see how it does without them. Due to the lack of stiffness of the booms, I glued in carbon tubes in each one and laminated a 3mm cover over the tube, that made them very stiff. The wing still had some twist so I used two carbon tube spars as well.
I mounted the servos as far forward as I could to help the CG, but even single ply, it still came out at 21 oz ready to fly, so I'll have to use a 24mm E-15 or E-18 reload, and will probably go about 400 feet or so. I cut my lead weights into small pieces to try to fit them in and be as unobtrusive as possible under the nose, but they still look like small piles of silver bricks.....
I laminated some .03 styrene on the landing contact surfaces to make them last longer, as well as on either side of the fuse to support the rail buttons for launching. I also used styrene strips on either side of the tail booms to support the pivot rod and it works well, is thin and light. I like this better than using spruce like i used to do.
If I need a higher boost, I'll have to modify it for 32mm motors, which will add 6 ounces of tail and corresponding nose weight and I'll probably have to stiffen the fuse and wing a bit more as well. I don't want to do that...
I was a bit limited in my markings and might have to try to print something on decal sheets after the maiden to finish it up all the way. For now it looks good enough.
Hope you like it, the link to my CG calculation which matches the indoor glide results is here:
Update 12/27 Three good flights today! The E-12 is a good motor, although boost isn't high, glide is quite good. The E-18 loaded in the RC casing was good, but had just a bit of flutter near the end of burnout and is a bit hard. An E-15 might be ok as well. Glide and trim settings were very good, had to tone down the elevator throw as it was quite sensitive.
Flight videos will be live in a bit here:
Since the rocket boost height wasn't that high it's been hanging from my ceiling after about 30 flights.....I finally decided to put a grayson parkjet v2 on it and make it a pusher so I can get some more flight time. I reinforced the bottom nose with doublers to give something or the 2200 mah pack to attach to using velcro and elastic. AUW should be about 25 oz with an apc 6x4 or 6x5.5 prop. Waiting for the motor to arrive now.
Update 12/2013: Got in a perfect pusher flight today, the grayson with 6x4 was perfect and it clibed out of my hand at half throttle and flew really well. Loops at 70% throttle, you just need to watch the speed as there is some flex and you don't want to pull really hard on a pullout, rolls were quite positive and didn't loose altitude. Landings power off were pretty easy, but you can overflare as the controls are quite responsive.
That looks pretty neat. I saw spaceshipone hanging from the ceiling when I was at the google campus the other day, and was surprised to see that the tail had a severe down bend in it to presumably lower the thrust line... it was alot more curvy in person than I expected. I'm curious to see how your more straight-designed mockup flies.
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