|Jul 09, 2012, 05:18 PM|
A Spaceship for Lazy Martians
Roy Clough’s 1954 Martian Spaceship design is one of the many models that I’ve wanted to build for more years than I can remember. Life in general always seemed to interfere and I never did get around to building it. I was also a bit put off by the apparent complexity of the construction and the time that would likely be needed to build it.
Then, a couple of years ago, QEFI magazine had a construction article (with free full-size plan) which greatly simplified things, mainly by making the bulkheads out of foam rather than balsa sticks. Must build that, I say to myself, then the usual procrastination sets in and it doesn’t go much further.
Until Brokenspar started a build thread here on RCG http://www.rcgroups.com/forums/showthread.php?t=1666181. That looked so interesting that I finally had the inspiration to get going on one for myself. But being a bit short of time (not to mention lazy) I decided to go with the quick-and-easy part foamie version. Probably not as nice as the all-balsa original, but because I didn’t want to spend too much time and effort on something that might not even fly very well, that was fine.
Here, for anyone who may be interested, are a few notes and photos on my build of this modernized semi-foamie version. I’ll keep the notes brief and let the pictures and captions do most of the work.
First step was to make a “build drawing/sketch” in CAD, mainly so I didn’t destroy the original plan, and also to incorporate the various modifications I always seem to make to any design when I build it. Actually, in this case the plan was a bit rough and had some errors and inaccuracies that needed to be corrected. Photo 1 is a low-res indication of what’s involved. Full-size plans are available from QEFI - PM me if you need more details.
Construction starts with lamination of the eight 1/8” x 3/16” curved longerons. Rather than making all eight individually, I started with a single strip 2” wide, made by soaking three strips of medium balsa in water, brushing on PVA glue, clamping in a jig cut from 2” thick blue styrofoam, and allowing to dry for a couple of days [Photo 2]. I then ripped eight 1/8” wide longerons from this, on my bandsaw. A light sanding, and the longerons were done.
I cut the bulkheads from 3mm Depron. There are two choices here. The edges of the bulkheads could be flush with the outer surfaces of the longerons, so they will be visible in the finished model and its surface will consist of a series of “facets” along the length. Or, the bulkheads could be undercut so the covering doesn’t touch them and the surface of the hull between the longerons is smooth and continuous. I chose the second way, and made the bulkheads to match the inner faces of the longerons (that is, undercut by 3/16” from the outer surfaces of the longerons).
Photo 3 shows the longerons and bulkheads for the first half-section of the hull, ready for assembly.
Because of the thickness of the nose bulkhead (2 pieces of 3/16” balsa, crossgrain) and the sharp angle of the longerons at the nose, it’s important to chamfer the edges accurately [Photo 4].
I used foam-safe CA and kicker to join the half-bulkheads to the two base longerons [Photo 5] then added the other three longerons [Photo 6].
[I’ve recently started using a magnetic building board system. I just can’t put into words how absolutely delighted I am with this, and how much easier, faster, and better it makes model building. Five minutes after I started using the magboard for the first time, I knew I would never go back to pins.]
The half-hull structure can now be removed from the board [Photo 7].
I'd be happy to answer any questions, provide more details, etc.
To be continued…
|Jul 09, 2012, 09:33 PM|
That is pretty neat. Do let us know how it works out, keep us informed.
I think I might have gone for a profile style with a simple cross shape of two foam panels interconnected in the middle. It would have looked almost the same in the air flying around. That was my first thought when I saw your thread subject line.
|Jul 10, 2012, 09:40 AM|
Something like this, Earl?
I considered that but thought a "full-bodied" version would be a bit more interesting and satisfying.
Actually, the one I'm building is very easy and is going much faster than I expected. I should have it finished in the next couple of days. Will post progress later today.
|Jul 10, 2012, 06:09 PM|
A fair bit of progress since yesterday, with just a few hours work.
The other half-sections of the bulkheads are glued in place on the semi-hull assembly [Photo 8] and the remaining three longerons added [Photo 9]. The structure was surprisingly strong and rigid at this point [Photo 10], and the covering should add a lot more of that.
Soft 3/16” balsa filler pieces added to the nose area [Photo 11], and sanded. 1/16” ply motor mounting plate glued on front, and equipment shelf (consisting of 1/64” ply laminated to 3mm Depron) glued to side longerons between nose and Bulkhead 1 [Photo 12].
I will be using a HK C2404-1900 brushless motor and Plush 10A ESC. I have no real idea of what power will be needed, but I’m aiming for a ready-to-fly weight of no more than 8 oz. At 100 watts/lb, which should be plenty, I’ll need 50 watts which the C2404 will run at on a 2-cell lipo and a GWS 7035 prop. Apparently it’s important to use a small diameter prop to minimize torque effects. That motor can take up to 9.5 amps, equivalent to around 65 watts on 2S, so I could go up in power (with a GWS 7060 prop) if necessary.
I will put all the equipment in the nose area, so I have to build only one hatch (my least favorite job on any model, and a bit fiddly on this one). Photo 13 shows the ply mounting plate drilled for the motor screws, the bottom of the nose drilled for the motor wires, and the basic hatch construction done.
I decided to sheet some of the fuselage tail end area, to provide a bit of reinforcement for the fin and stab mounting, and a place for the pushrods to exit. I used scraps of 3mm Depron (which the fin and stab will be made from) as temporary spacers while doing the sheeting [Photo 14].
This has gone pretty smoothly and quickly, and I should be able to finish up in the next day or so. More soon...
|Jul 11, 2012, 11:30 AM|
Your build is fascinating!
Maybe one day we should have a build off just for bizarre vintage models - lifting bodies, and annular wings and things?
|Jul 11, 2012, 06:08 PM|
Harry D, Whats the length.
Harry D, What is the length of the "fusalage" ommitting the tail surfaces?
Then what is the "span"? Back about 1999 I built one from Skip Ruff's plan ( was in Model Builder) and ideas of C-fiber, balsa sticks and 0.25 diesel. I flew it for maybe 2 years but a barbed-wire fence put it on the shelf in a wind one day.... It was 54" long.
I thank you for any information on these two measurements. I thought about building a very light balsa frame and covering it with 3mm Depron but am too chicken ( weight you know):
|Jul 11, 2012, 08:23 PM|
Thanks, Brokenspar. Your post inspired me to get going on my own MSS. I'm looking forward to seeing how you finish yours off, and how the original compares to the "simplified" version.
Tex, referring to the illustration in Photo 1 of Post 1, which is what I'm basing my current build on:
Overall fuselage length, from front of firewall (motor mounting plate) to rear of fuselage, is 33.1".
Diameter of the fuselage (hull) is 9.7" at its widest point, excluding strakes (the narrow side "fins"). Strakes are each 0.8" wide, so I guess you could say the "span" would be 9.7+0.8+0.8 = 11.3".
|Jul 12, 2012, 08:29 PM|
I used HK “3.7 gram” servos. Including wires, connector, and arm, actual weight was 4.9 grams. Which is still OK, but I sure wish vendors would include those components when stating servo weights, since most servos don’t seem to work too well without them.
Photo 15 shows the servo installation, and the completed hatch. For the first time ever, I decided to try gluing servos in. I used a very small amount of low-temperature hot glue, which seemed to hold firmly enough. For the hatch, I used a retaining pin at the front, and a magnet at the back. A “handle” will be provided by part of the bottom skid when glued on later.
With this build, I got a bit carried away with trying to minimize weight. Originally, I was going to put the servos in the tail but found that the extension cables would weigh more than twice as much as the servos. So I put the servos in the nose. Then I discovered that the usual wire pushrod and plastic sheath setup would weigh even more than the cables. So I decided to use 1 mm carbon fiber pushrods, with supports consisting of short (1/4” or so) lengths of sheath tubing supported by Depron strips across the bulkheads. To align these supports, I used 3/32” piano wires, temporarily clipped to the servo arms and run to the exit locations near the back of the fuselage [Photo 16].
Then I glued the Depron strips in place [Photo 17], removed the wires, and put the tubing pieces in place [Photo 18]. This setup did end up being very light (about 5 grams total) but was probably more trouble than it was worth, and I don’t think I’ll be using it again.
So, ready for covering now [Photo 19]. I will be trying Ultralite film (also known by a dozen or so other names - Solite, Litefilm, etc etc) for the first time.
I covered each of the eight fuselage sections with a separate piece of film. I was really impressed with this film - went on easily, stuck well, shrunk up perfectly, is very light, and seems plenty strong enough. Thankfully, I didn’t encounter the dreaded “Solite stick”, when two adhesive sides come into contact and can’t be separated. Apparently some colors are worse than others for this, and silver is one of the better ones.
One minor glitch was that there was more sag between the curved longerons than I was expecting [Photo 20] but that was easily fixed by trimming back the edges of the three largest bulkheads to clear the (sagged) film.
Photo 21 shows the basic covering completed. Covering was, for once, a very enjoyable part of the build, and I was pleased with the way it turned out.
Still to come: installation of tailfeathers, strakes, and equipment. I’ll keep right at it, because now I’m really keen to get this done and see how (if?) it flies.
|Jul 14, 2012, 08:00 AM|
The covering looks fantastic! To my mind, covering is even more stressfull than a maiden fight I particularly like the way you can just see a sugestion of the internal structure. I have a feeling this one is going to fly just fine
|Jul 15, 2012, 05:53 PM|
Ready to fly
I forgot to take any photos during fabrication and installation of the tailfeathers and strakes. No matter, as that was all pretty basic and there wasn’t much to show anyway.
I cut the horizontal stab, elevator, fin, and rudder from 3mm Depron. Glued some 3 x 0.5 mm carbon strips to the stab and fin at the hinge lines, to stiffen them up (this was essential). Beveled the elevator and rudder, and hinged them using ordinary Scotch #600 transparent tape. Until recently, I’ve always used Blenderm for this kind of hinging but have never liked how rubbery and overly flexible it was. This is the third model I’ve used the #600 tape on and I much prefer it. Cheap, too.
Photo 22 shows the fin and rudder installed and connected up, and Photo 23 the stab and elevator. I put a couple of carbon strips on the underside of the elevator in an attempt to stiffen it up a bit, but they didn’t seem to make much difference.
Strakes (the narrow “fins” running along the length of the fuselage) were just cut from 3mm Depron and glued to the longerons, on top of the film covering. I was a bit concerned about how well these would hold, because there are three joints (two layers of film, and the strakes themselves) involved. But it proved to be no problem at all, and the strakes seem to be very firmly in place. The Ultralite film has excellent adhesion to balsa and to itself, and the glue I used for the strakes (http://www.hobbyking.com/hobbyking/s...dProduct=17535) seems rock-solid too.
Photo 24 shows the RC equipment installed in the nose area. I used a Hobbyking Micro Orange receiver, which I’ve always had good success with, velcroed to the first bulkhead.
ESC is a Turnigy Plush 10A. A GensAce 2S450 lipo will be held in place with the velcro straps shown [Photo 25].
So, all done. Photos 26 to 29 show the final product, checked out and waiting to fly.
I’m very pleased with the way this whole thing turned out. The build was fun and easy to do, went smoothly and quickly, and resulted in a pretty nice-looking (and certainly different) model.
Final ready-to-fly weight, with GensAce 2S450 lipo, was 6.7oz. The C2404 motor with a GWS 7030 prop draws about 50 watts, for a power loading of around 120 watts/lb. Should be plenty!
Flight report to come, if we ever get some decent weather.
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