Martian Spaceship

[John T]

Even I can’t explain why, but I’ve started to build a model based on the Roy Clough “Martian Spaceship”. For those who haven’t come across this aircraft (?) before see https://outerzone.co.uk/plan_details.asp?ID=3863.

The original was designed as a free flight model, but I’d like to put R/C in it and I was wondering if anyone in the forum had actually made one? I know a number of people have built R/C versions before, but from the sound of it with somewhat mixed results.

I’ve found a plan from May 2010 Q&EF international by Paul Witco that I’m using as a basis, but that was built using foam board, which I don’t have, so I’m having to modify the structure accordingly.

I’d originally intended to use elevon control, rather than the conventional rudder/elevator that Paul used on his version, but I read an old post on another forum that this didn’t work very well.  I’d be interested to know if anyone has tried this.

Anyway, this is the structure so far.

[DaveyP]

I like the idea of that, although until I read the article I was looking for a wing of some kind........?

 

Good luck with the build, I will be watching with interest.

[ken anderson.]

hello john, interesting I've seen it before but could never figure out how it could maintain a flight....I'll follow you build etc....thanks.

 

ken anderson...ne...1...flight dept.

[David Davis]

Have you seen this John?

 

https://www.rcgroups.com/forums/showthread.php?1666181-Martian-Space-Ship

[John T]

Hi Ken, I suppose the fuselage (hull?) is effectively an extremely low aspect ratio "wing". It does seem wrong somehow though, I must admit.

Thanks for posting the link David. I had seen it before but it makes interesting reading.

I've managed to do a bit more on my version today. I still haven't decided whether to just use rudder & elevator or split the elevator and fit tailerons as well, so for now I've left the elevator in one piece.

There are 8 fins or strakes in addition to the tail surfaces, so I've made a start on those.  To try and ensure a close fit to the stringers I've used a balsa stripper to put slots into the 3/4" wide 3/32" balsa, dampened them and glued them with aliphatic resin, then used rubber bands to try and hold them in place while the glue dries. I used bits of fiberglass sheet to support them in the correct position.  It's a bit fiddly getting the rubber bands tensioned correctly, but it seems to work.

 

[ken anderson.]

i checked out DD link and they have some video's of Martians flying......i am impressed.... keep going John they look impressive.

 

ken anderson...ne..1...Martian dept.

[Phil Green]

Col, a PANDAS pal, campaigned a 'Windbag' at the 2017 S/C event, its a very similar model, as you can see they fly quite well !

 

https://www.youtube.com/watch?v=ov3ytSx2CHk

[John T]

Brilliant, thanks for the link Phil.  I hadn't seen that before.

Before I'd started this build I downloaded the plans for the "Windbag", but when I looked at it I wasn't sure whether it would cope with the extra weight of the radio equipment. The original "Spaceship" is quite tubby in comparison which is why I decided to go that way instead, but I'm incorporating a couple of features from the "Windbag" in the build.

Hopefully I'll get a bit more done today.  I need to get the motor and tail fitted on a temporary basis so I can work out where to put the R/C equipment to get the C of G somewhere close.

[Nigel R]

This is definitely different - like it, like it ?

[Phil Green]

I do remember Col saying that his gear was mounted as low as poss, on the lower keel. 

It was covered in TOM - tissue over mylar & I believe his had conventional rudder/elevator rather than any mixed 'taileron' type of thing. 

One thing I do remember - that it didnt glide at all, so save some power for the landing!

Cheers

Phil

Edited December 3, 2021 by Phil Green

[John T]

Thanks Phil. As it obviously seems to work I'll stick to rudder/elevator controls then. I'd already decided to keep the gear low down in the hope that it will provide some degree of pendulum stability.

I'll probably use tissue over Doculam to cover the thing. It should only be about 5 grams heavier than mylar, but it's a lot less faff to put on as it already has the adhesive on it. I see the original was just tissue covered.  I can imagine how long that would last...

I've now finished all the fins etc and fixed to motor in place to get an idea where it's balancing, so my next job is to get the gear in place and make a mounting point for the battery. Oh, and I suppose I'll have to make some sort of battery hatch as well.

I keep thinking that part of the airframes missing. This is a perfect build for people who don't like cutting out wing ribs ?.

[John T]

After getting distracted with some other stuff for the last few weeks, I’ve finally finished the Spaceship.

As mentioned earlier, I decided to cover it with tissue over Doculam.  After I’d put the Doculam on I must admit that I was almost tempted to try and fly it like this, as I’m by no means convinced that it will fly.  However, the weather wasn’t great, and as it would be a lot easier to apply the tissue without the fins attached I decided to finish it properly.

 

 

In an attempt to recreate that slightly washed out 1950’s comic book appearance I used a pack of Hobbycraft multi-coloured tissue, applied with Wilco satin varnish – mainly because I can do it in the house and it was too cold to dope in the garage.

Fitting the fins turned out to be a bit of a pain.  I originally laminated them against the longerons for a perfect fit, but as I hadn’t realised how much the tension of the covering would change the shape of the fuselage I ended up having to hack them about quite a bit to make them match again.

 

 

It looks like the weathers going to be ok for the next few days, so I’ll get some batteries charged up and see if it will actually fly…

[Trevor]

Looks brilliant - good luck with the maiden!

[ken anderson.]

looks good JT......everything we build fly's once at least....let us know how it does..

 

ken anderson...ne..1....... martian dept.

[John T]

Well, that was, err... interesting.

The first attempt (I take your point Ken, but I would hesitate to call it a flight) lasted about 3 seconds.  After launching it started a descending left turn which I tried to correct, resulting in it instantly rolling right and hitting the ground inverted - not quite what I'd intended!

Other than a broken prop there was no damage.  The original plan has the tailplane set at 0 degrees to the datum, but after looking at the "Windbag" plans I'd already built in a couple of degrees of negative incidence.  As this obviously wasn't enough I wound in some up trim, added a touch of right trim and reduced the rudder throw by half. 

The second flight was slightly more successful.  The model still dipped after launch and just skimmed the ground before I managed to pull in some up elevator.  This was followed by an exciting few seconds as it performed a sharp, high speed left hand turn at head height, and I found that the rudder was still way too sensitive.

By this point I'd gained some semblance of control and climbed away. I was surprised how fast it was and I was still having to correct a lift hand turn, which I'm guessing is torque induced. As it was still under elevated as well it didn't make for a comfortable experience.

After a couple of circuits I decided it would be better to land and sort it out on the ground, rather than try and fiddle with the trims while it was still flying.  All was looking good until I reduced the throttle a bit too much as I approached the fence that surrounds our club strip. Phil G had already warned me about the glide, but I was still taken by surprise with the 45 degree angle of descent, and it bounced off the top of one of the fence posts before I reacted, putting an abrupt close to play for the day.

The post has slightly damaged one lower former and taken out two more, which is easily repairable. I'll also have to replace the covering on 4 bays.

Not catastrophic then, although it wasn't quite as successful as I would have liked. I now feel confident that with a bit of tweaking it should be ok.

Before flying it again I'll reduce the rudder throw even more and probably add some expo.  I noticed that the original Roy Clough design had the C of G a bit further back than the Paul Witco version, and I wonder if I moved it back a touch it might help with the under elevated feel.  However, the original was designed for free flight and I don't want to make the rudder even more sensitive.

 

[ken anderson.]

thanks JT...i would think that it will need very little movement on the controls for its size/weight, maybe only a lot of elevator to flare out a landing? a forward  c/g might calm it down also? ...anyway well done for attempting to defy Gravity.

 

ken anderson...ne..1..gravity dept.

[John T]

The Martians have landed!  (As opposed to crashing inverted or bouncing of a fence post).

The Spaceship has now flown successfully.

 

 

While I had some of the covering off while repairing it I took the opportunity to extend the battery tray to allow for greater adjustment of the C of G without adding extra weight.  I also reduced the rudder movement even further and added a slight touch of right to counteract the torque.  The elevator movement was increased a bit and I mixed in the flap function with the elevator so that I now have a ‘take off’ setting with lots of ‘up’ that can easily be returned to neutral using a rotary slider on the side of my old Hitec Optic radio.

 

 

I’ve found that the stub fin on top is a convenient handle for an underarm launch.  Using the ‘take off’ setting and launching it up at 45 degrees with full power results in a stable climb out.  If the launch setting is reduced to neutral the climb stops completely and the model shows a surprising turn of speed at full throttle, considering its limited power.

After the first successful flight I added -25% expo to try and calm the rudder a bit more, not something I normally use.  It still needs to be treated with respect, but it’s much better than it was.

Now it’s been trimmed out it’s not difficult to fly, but it doesn’t behave like a conventional aircraft.  It can fly quite slowly in a nose high attitude, when it will gently rock from side to side but remains under full control.  It doesn’t seem to be possible to stall it.

The glide doesn’t really exist in the conventional sense.  I found that starting the landing approach reasonably high and reducing the power to about 30% results in a steep decent but with enough power for a decent flare, and chopping the throttle just before touch down results in a smooth arrival.

The most challenging part about flying it is orientation. As there is no wing it’s quite difficult to see how much bank is applied, and I certainly wouldn’t want to fly it very far away or in poor visibility.

If anyone else is afflicted in the same way and fancies building one, here are the settings I used:

Motor BL-2208/14 with a 20A ESC. Using a 7 x 4 prop and an 850mAh 3s battery gives about 85W, which is more than adequate.

Weight without battery is 10.5oz. At the moment I’m flying it with the C of G at 34%.

The rudder has 7 degree movement each way.

The tailplane has -3 degrees incidence relative to the datum. I’d increase that to -5 degrees if I build another.

Elevator has 20 degrees movement each way.  The flap mix gives an additional 10 degrees up for take-off, with the mid (cruise) position set at 5 degrees.

[Don Fry]

Perhaps I might turn down the invitation to build one. But I applaud and celebrate your bloody minded quest to make it work. I bow to you. It flew. Well done. 

[Trevor]

Congratulations! the flying experience sounds rather similar to other 'wingless wonders', My Miss Hyperion had similar rocking tendencies. The high thrustline also caused a lot of negative throttle-to-pitch coupling which made landing challenging. All good fun.

[ken anderson.]

well done JT...pushing the boundaries there.....

 

ken anderson...ne...1...boundaries dept.

[J D 8]

                I recon we can think of such flying machines as very very low aspect ratio wings/lifting body's that have little damping in the roll.  I think if I were making one for rc it would have taileron controls. Still all good fun and well done for getting it to go.?

[Simon Chaddock]

John T

A spectacular success. Any video?

I suspect size becomes an important factor, the bigger the better, as with bigger it is easier to build light yet still be just strong enough.

I would agree with the concept of elevons and if I was doing it, and I might, the extreme roll sensitivity of such a design would encourage me to install a gyro!

One certainly made the maiden of my HP115 remarkably stress free.

Not quite a Martian spaceship but still a tiny span to length ratio.

 

A very long time ago (64 years!) my Dad drew up plans for a 36" long scale R101 airship for me to build in balsa & tissue for a school 'DIY' competition.

Not powered but it did amaze me how easily it could be made to 'fly' just pushing it along by one finger on the tail cone.

p.s.

I did not win anything as my Dad 'ratted out' to the head that he had drawn up the plan!   

 

[John T]

I took the Spaceship to the club field again this morning, and thanks to Mike filming for, me got this video of a short flight. I still need to work on the landings though...

 

 

 

I had toyed with the idea of tailerons myself when I first started building it (see my first post), but after seeing Phil Greens link to the Windbag video I decided to stick with rudder/elevator as it obviously worked.  Now I've flown the thing I'm not sure that tailerons would be any better.

The HP115 looks interesting Simon.

 

[john stones 1 - Moderator]

Love it, was that at warp speed, or impulse power ?

[Phil Green]

3 hours ago, John T said:

I took the Spaceship to the club field again this morning, and thanks to Mike filming for, me got this video of a short flight.

 

Excellent, well done John!    it seems to fly a bit faster than Col's Windbag?  Maybe the wind or the lens   ?