Martian Spaceship

[ken anderson.]

well done JT and Mike......looks like you have it near sorted.

 

ken anderson...ne..1...Martian's have landed dept.

[John T]

20 hours ago, john stones 1 - Moderator said:

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

Judging by the shape that some of my airframes end up it was probably warp, although I did build it on an impulse ?

It is surprisingly quick though and there was hardly any wind yesterday morning.  If you get the nose high you can slow it down quite a bit, but the side to side rocking become more pronounced.

[David perry 1]

Crickey...it is fast.

[John T]

I just shows how much drag you get from unnecessary items such as wings... ?

[Colonel Blink]

Yup, that is MUCH faster than my Windbag! It might be because the Windbag has much wider horizontal strakes (where the wings on any right minded design would be) which enable it to 'lay on the air' and give some semblance of lift, enabling it to fly slower? What I find with the Windbag is that the rocking motion only really occurs when you try and control the model in any way - leave it to its own devices and it settles down after a few seconds. One theory is that the underside of the octagonal fuz is a bit like a very small wingspan with a huge amount of polyhedral and the rocking is in actual fact extreme Dutch roll...... I'll leave it to the aerodynamicists amongst us to argue the pros and cons of that one!

 

As for tailerons - DO NOT TRY TAILERONS!!!! Some others have tried them, and the bloody things were uncontrollable, with any amount of 'aileron' input causing massive instant rolling, inversion, dives, explosions and the total collapse of Western civilisation as we know it. Best stick to simple R/E control, which will at least mean you can kid yourself you have input into where the thing goes.

 

They are mad as a box of frogs, never a relaxing flier, but conversely never fail to make people stop and look!

 

https://www.rcgroups.com/forums/showthread.php?2863243-Windbag-by-Colin-Read-NOT-for-TBD2-but-for-CAP2017!

[Simon Chaddock]

Colonel B

I think you might find the rocking motion results from vortex shedding. Above a certain angle of attack the "wing" vortices alternate altering the lift resulting in a powerful 'roll rocking'.

My model HP 115 does it and so did the full size one, much to the alarm of the test pilot when it first happened. It started above a critical angle which in effect limited how high the nose could be safely lifted to limit the speed on approach. I believe some of Concorde's complex wing twists was to control the way the vortex behaved to allow its  high alpha landing approach.  

 

JT

A very interesting video.

I was amazed how little incidence your Martian required for lift but then I suppose it was travelling quite fast.

Have explored what happens at higher attack? It probably will not stall in the conventional sense.      

[John T]

Colonel,

Thanks for the post. I've just spent the last half hour reading your Windbag thread. I wish I'd come across it before I built the Spaceship as it would have answered a lot of the questions I had about it, not least of which were, would it fly, and yes, there are other people mad enough to build one!

9 hours ago, Simon Chaddock said:

I was amazed how little incidence your Martian required for lift

The original plan for the Spaceship didn't show any incidence at all. I added a few degree because I didn't see how it could possibly fly without it. The original free flight version did have the C of G a bit further back though, but I'm not sure I'm brave enough to try that with the rudder being as sensitive as it is!