Spacewalker half scale 168" electric

[Andy Boylett]

Thanks Phil.

I have been thinking more about the receivers as I was intending to put one in the end of each wing, one in fus front and one in fus rear. However, to do this would mean having to have break points in the 2 wing and the fus rear wires so that they could be taken apart for transport. Any views?.....or is this just the same as having breaks in the servo wires?

[Phil Clark]

No problems as far as I'm concerned.......same as a servo wire.

[Ross Bathie]

Hi there Andy looking good! just a qgick question, what size prop will you be swinging and what sort of flight time do you think you will acheive?

Thanks Rossco

[Andy Boylett]

Hi Ross,
To fly reasonably, without prop-hanging or similar high energy moves the plane will 'need' 220watts/kg. So at say 40kg (about 37 at present) it needs 8800watts.

Because I fly electric it is easy to build up a bank of knowledge on flight duration by always flying 10 minutes and then seeing how much battery charge is required (more difficult to do with fuel users!). Now I find that for an average flight (again without doing 3D tricks), the amount of power used is about half of the 'needed', or 4400w in this case.

At 4400w and 50volts the current draw will average 88amps.

So 88amps for a 10minute flight is 88 x 10 / 60 = 14.6 amp.hours

The batteries I am using will have 30amp.hours. I like to not use more than 2/3 of the battery, so this would take 14 minutes, leaving a nice margin.

However, my son Sam will be the pilot and he has spotted that we could probably fly with just 20amp.hours of batteries on board. We use the HobbyKing Turnigy nano-tech batteries and these are capable of delivering their full capacity every time, without any detriment to the battery. Hence, 20amp.hours would still have a 3.6 minute margin on a 10 min flight. It would also knock 4kg off the planes weight.

Regards
Andy

[Andy Boylett]

It was really useful going to the LMA show last Sunday as it helped us to understand some of the issues with moving big models around. As a result I have spent time this week in modifying some aspects of the plane.

The wing centre section training edge was just sheeted, comming to a poit where the top and bottom sheets meet. However, this edge has proved to be vulnerable to knocks as well being useless for helping when picking and moving the plane. I have now remove 45mm of trailing adge and replaced it with solid balsa.

Undercariage. This is built exactly to scale which meant it ended up being attached to both the wing centre section and the fus (just in front of the wing leading edge). With the centre section in place I couldn't get the fus front half through the caravan door. It could have gone in the car, but with a 100kg wheelchair ih there that was tricky as well. To get the centre section off, the undercarriage had to be removed first. So no I have modified the wing centre section and attached a ply piece that extends out and forward of the leading edge so that the undercarriage is attached to the centre section only.

The tail group alos needed to be dismantled! I had thought it would go in the caravan but because of the wire stays it would not go through the door. Does anyone have any tips for quick but reliable release of wire stays?

Any other tips to do with building in bits that help transporting would be appreciated.

Cheers, Andy

[Ron Pearman]

Is that soft solder?

[Andy Boylett]

Is that soft solder?

yes it is.

[Ron Pearman]

It's just that, if they are load bearing, in the instructions for Duncan Hutson's SE5, he writes " It is strongly recommended that bracing wires are silver soldered rather than soft solder joints which will almost certainly fail in flight."
Ron.

[Stuart Solomon]

Andy, if you use a bolt as a pin through the clevis, you will only have the points of the thread as a bearing, much better to use a proper clevis pin, smooth all the way and just a small split pin to hold.

Stuart

[Andy Boylett]

It's just that, if they are load bearing, in the instructions for Duncan Hutson's SE5, he writes " It is strongly recommended that bracing wires are silver soldered rather than soft solder joints which will almost certainly fail in flight."
Ron.

Thanks Ron, I'll use silver solder then if that is better.
Cheers, Andy

[Andy Boylett]

Andy, if you use a bolt as a pin through the clevis, you will only have the points of the thread as a bearing, much better to use a proper clevis pin, smooth all the way and just a small split pin to hold.

Stuart

Stuart,
I agree, it definately would be a little better, althought they don't really have to turn at all as they are in a fixed postion.

Those 2 bolts you can see are the ones I have 2 remove to get the tail apart. I think if used a clevis and a split pin they will be very fiddly and the split pin will need replacing often as it will fatigue. I'd quite like some sort of sprung clevis/split pin if anyone knows where to get one?....When I asked the question earlier about easier ways of assembling/disssasembling for moving the model around this was the sort of thing I hoped may be known about. Having to constantly take small bolts or clevis/split pins apart is very fiddly. There has to be a better way
Thanks, Andy

[Tony Collins 1073]

How about a plain shank bolt threaded just as far as it needs?

[John Rickett]

Andy,
If, as you say, each cable is loading bearing (and you are happy with the breaking strain) then the crimps aren't good enough. For a crimp to work, the peaks and troughs of each cable coil fit into the troughs and peaks of the doubled-back part in much the same way as the threads on a nut and bolt fit together. From the photos, the cables are just lying side by side and relying only on the pressure exerted when the brass tubes were flattened........... you need a proper crimping tool if you don't want those crimps to pull apart.
Regards

[Andy Boylett]

Andy,
If, as you say, each cable is loading bearing (and you are happy with the breaking strain) then the crimps aren't good enough. For a crimp to work, the peaks and troughs of each cable coil fit into the troughs and peaks of the doubled-back part in much the same way as the threads on a nut and bolt fit together. From the photos, the cables are just lying side by side and relying only on the pressure exerted when the brass tubes were flattened........... you need a proper crimping tool if you don't want those crimps to pull apart.
Regards

Hi John,
I am using 54kg load cable, 0.9mm with nylon coating bringing it to 1.0mm. Yes, I have just used pliers but I guess I need some of these http://www.tecni-cable.co.uk/Tecni-Cable-Crimp-Tool-for-Double-Copper-Ferrules-115-007-023
Regards, Andy

[Andy Boylett]

How about a plain shank bolt threaded just as far as it needs?

yes if I can find some very small ones

[Tony Collins 1073]

Just melt the nylon casings together as they lay side by side before crimping with your normal pliers and they will NEVER pull apart.

[John Rickett]

Andy,
I'm sure those pliers will be fine. To obtain the breaking strain rating you would need to strip the coating at the ferrule, though my guess is those cables are not really taking much strain - except when you bang against them putting the model together! But if you get the right pliers and ferrules you know that the joints are not going to fail prematurely.

[Andy Boylett]

Andy,
I'm sure those pliers will be fine. To obtain the breaking strain rating you would need to strip the coating at the ferrule, though my guess is those cables are not really taking much strain - except when you bang against them putting the model together! But if you get the right pliers and ferrules you know that the joints are not going to fail prematurely.

Thanks for the help John...always learning

[Andy Boylett]

Just been checking the full size drawings and I have done the rigging wire points on the underside of the fus wrong . The 2 wires are supposed to come down to 2 different attachment points. Here is a piece of the full size planes drawing....

Wires.jpg (11.97 KiB) Viewed 12138 times

[Mike Booth]

Andy, I hope you will forgive me for playing the role of 'Devil's Avacado' as we like to call it sometimes.
You have clearly put a great deal of time and effort into this creation, not least money.
Bearing this in mind we all hope that you will be rewarded with a fine contribution to the LMA show circuit for many seasons.

Several points come to mind, this is an open forum, so I offer these, based on my observations drawn from a 25 year membership with the LMA.

Many times i have seen very large models constructed under the banner of the LMA.
A great deal were 'state of the art' in their day and deemed to be huge in scale only to be superceeded, by something even more impressive in ambition the next year.
So we get to today where 1/2 scale is not common but not unknown to the point where we are staggered.
Fortunately the standards set in place by the LMA are stringent to say the least and for good reason.
These 'aircraft', for this is just how the CAA see them, are no longer models and cannot in any way be compared to anything that went before.
In the quest for 'biggest' in the association, (as clearly in the past this was almost a competion), some people forgot that they were building something to a scale that had never been done before .
Nor did they have any experience on type, construction or flying characteristics, and would jump from one subject to the next without really knowing what mistakes were made with the previous subject.

Fortunately you have chosen a subject which will have very forgiving flying characteristics, should all the normal parameters be in place.
However, it is still an aircraft at half scale and nothing can be taken for granted regarding the operation of something this size.
The mistake I have seen many make in the past,..

Regardless of the standard, all of these creations are in unplumbed depth's for the same reasons.
Therefore the need for signing off and certification regarding flying tests is crucial.
Even then, it would be the most confident in the LMA that would approach a public display with only a few flights 'on type' as at least twenty could be regarded as test flights.
Its a bit like a mini Farnborough and frankly no one, however well the 'aircraft' flys to start with, can truely know all its habits and envelope for some considerable time.

I often wish more members had access to fullsize light aircraft, where the inspection of internal control runs and system's would open the eyes of many that are aiming to fly something just half the size.

Ok I appreciate wing loadings are much lighter and know that nobody will be sitting in the prototype.
However, there are still people and property underneath.
One look at the fullsize and I think 5mm fittings would become the norm with anything over 1/4 scale or 3.5 metre wingspan.

I wish you luck and commend you on the apparent standard of construction, but do please take heed of all good advice.
Your other smaller project will show you nothing of what the Spacewalker has in store, remember it is half scale and unique in design and construction!

Regards Mike.