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Member postings for Simon Chaddock

Here is a list of all the postings Simon Chaddock has made in our forums. Click on a thread name to jump to the thread.

Thread: Gyro assisted CofG
16/01/2019 14:56:19

I have my doubts about using a single gyro to enable flight with a true 'unstable' CofG as distinct from a 'poorly positioned' one.

A single gyro for longitudinal stability would work but only if it was kept with strict limits as once say any roll was present automatically applying elevator alone could well make the situation worse particularly if any form of aerodynamic stall occurred.

A full 3 axis gyro is better but even then the sophistication of its on board logic as well as other inputs, like air speed, angle of attack and even level of power are really required for the system to work out the appropriate control inputs to ensure an unstable plane never gets into a situation from which it cannot recover.

To be realistic RC plane stabilisation is there to help the pilot control the plane, which is does very well, whereas a full drone system with GPS really controls everything and simply lets the pilot move it in a chosen direction and speed.

It is perhaps worth remembering that such autonomous flight capability is one of the reasons behind the new "UAV" regulations which unfortunately effect all forms of model flying.

Thread: Antonov AN2
15/01/2019 11:26:55

With temporary too strong springs in the spring units the fuselage can sit on its printed/Depron wheels.

UCwheels

The tailplane and elevator. 2mm Depron skins over a Depron shear web.

Tailplane1

The 5 g elevator servo.

Eleservo1

The tail plane is braced.

Tailbrace

The brace is also 3 mm Depron but with a balsa leading and trailing edge.

The elevator halves are joined with a short section of thin wall glass fibre tube.

To keep things light and simple the elevator is top tape hinged with invisible (matt) tape.

Thread: Gyro assisted CofG
14/01/2019 11:44:03

suoertigerfan

Likely because a military gyro system costs £ tens of thousands rather than £ tens and is fully duplicated or triplicated in case of failure.

And the plane will crash spectacularly if anything goes wrong.

Thread: Antonov AN2
13/01/2019 22:23:46

Now comes the tricky bit the scale printed undercarriage.

With the lower wing centre section in place all the undercarriage mounts are available so after many hours of both CAD and printing........

UClegs1

All printed, even the pins are cut off bits of filament. The only metal will be the stub axles'

The printed spring units are in about the fully relaxed position but should give nearly 1" (25 mm) of travel once the appropriate rate springs are installed.

Part of the design philosophy is that it should shear off before tearing out the fuselage mountings as I can always print more undercarriage. wink 2

12/01/2019 23:38:04

reg

I must say I am pleasantly surprised how well the cheap A8 is performing. The only bit I have actually replaced is the extruder heating element. Entirely my own fault as I broke one of its wires when i changed over a nozzle..

Yes it will have all the flaps. Full span on the lower wing, half span on the upper.

From this video it appears the upper flaps travel a bit more than the lower. I don't think the ailerons droop.

.

Edited By Simon Chaddock on 12/01/2019 23:39:04

12/01/2019 20:07:45

 

Just fuselage planking.

The basic fuselage skin substantially complete using thin strips of masking tape to hold the last plank in place until the glue dries..

PlankCmplt

And it is pretty empty inside!wink 2

Inside

The ESC will go on the cockpit floor with its fins sticking out underneath in the air stream just about where the oil cooler is in the full size.

Edited By Simon Chaddock on 12/01/2019 20:08:30

11/01/2019 17:00:28

After some effort all the formers are in.

Allforms

At this point i realised I had completely forgotten the undercarriage mounting that is outboard of the fuselage!

Fortunately UHU POR remains soft and rubbery for quite some time (days) so with care it was possible to extract the offending former and replace it with a new one.

Allforms1

A close up of the U/C mounting that is part of the printed fuselage former.

UCmounting

The bracket carries the top if the spring unit and is also the attachment for the flying wire.

The fuselage is still a bit wobbly but the rigidity increases as piece of the Depron skin goes on.wink 2

Thread: Latent Servo Response
11/01/2019 12:24:22

It can be frustrating but I would put in down to a temporary loss of signal or poor servo connection.

The actual cause may now be difficult to trace as everything has now been given a substantial "shake".

All you can do is make sure everything follows good practise principles when you rebuild and maybe use a different Rx..

Thread: Antonov AN2
10/01/2019 17:06:01

As it is a Depron build the principle of "hollow" is used where possible so lightweight printed fuselage "ring" formers will be used.

The fuselage 3 view tile printed to the correct size to match the cowling.

Fuseprint

A typical former in the main cabin area.

Former C

It is 6" ( 152 mm) tall and 5" (127 mm) wide and weighs just under 2 g.

After some hours printing the full set of ten.

Tenformers

With the fuselage flat side area cut out of 3 mm Depron the first three formers are glued in and the tail brought together..

Firstforms

This feels like a very 'conventional' form of construction but using unconventional materials! wink 2.

One disadvantage of using printed formers is that there is no possibility of any 'adjustment' once printed as there can be with say a balsa or ply so they have to be "exactly" right. So once construction actually starts a few have to have their CAD files altered and be reprinted. Easy enough to do but time consuming.

The six scrap formers - so far!

sixscrap.jpg

With absolutely nothing inside the fuselage at least there should be no problem positioning the battery.

 

 

Edited By Simon Chaddock on 10/01/2019 17:13:30

09/01/2019 15:34:26

Motor cooling?

My own view is that provided some air passes over, and preferably through, the motor it does not take a huge amount to dissipate the heat as there is quite a bit of surface area within the motor and inadditon its rotation ensures the air is moved about quite a bit. This the opposite of say an ESC where the heat is generated by a relatively small area which is itself buried within a plastic 'chip' and in many cases further surrounded by thick a heat shrink blanket.

In my case the fairly close fitting scale crankcase will help to duct the cooling air entering from just behind the prop and through the motor. Well that the theory. wink 2

A further interesting item is that despite the AN 2's size and weight the wings are simply pin jointed to the fuselage which means that all the flying loads are carried just by the rigging!

My AN 2 will have a span of 48" (1220 mm) so can be built as a 'one piece' plane. At that span and with "working" rigging it is quite possible that the wings can be made of Depron with no spar. We shall see.

The cowling on the AN 2 is big and circular which suggest it could also be printed.

The motor bulkhead and "cone" that supports the motor mount itself.

Bulkhead 2

A single printed component. Note the 4 cooling air exit holes that lead directly into the fuselage.

The motor and the ASh 62 are individually bolted to the motor bulkhead with captive nuts behind.

The full two part cowling.

Cowl 1 The ASh-62 is quite visible inside.

Cowl 2

Now to build a fuselage to match.

Printed formers with a 3 mm Depron skin?

08/01/2019 22:51:39

With the Albatross structurally repaired but waiting for a major revision to the electric I wondered about building something else.

My first thought were to the Short Seamew.

frontleft.jpg

I even went so far as to buy a suitable 4 blade prop (10x8.5) and a 950 kV motor.

10x8.25.jpg

The biggest issue were those long under carriage legs cantilevered off the underside of the mid mounted wing.. Fine for a landing on an smooth aircraft carrier but by comparison any model field is "rough".

By chance the Antonov AN 2 came into the picture. A four bladed prop (actually a better match) and it was specifically designed for rough field work.

cockpitview.jpg

The AN 2 uses a big Ash-62 1000hp radial (a licensed built Wright Cyclone) and in a cowling big enough to really see the engine within it.

So how about a near scale printed Ash-62 sized to match the 10" prop and with the motor completely hidden within the crankcase.

cyclone1.jpg

cyclone2.jpg

After a good few hours of printing a 9 cylinder radial.

ash-62.jpg

Looks solid but it is completely hollow, even the push rods. and with a ruling wall thickness of just 0.3 mm. It is even printed in two colours, crankcase and push rods silver, cylinders black. Actually it is aa bit of a 'plastic kit' as it is made up of 74 printed parts all glued together!

A bit unusual - build the engine first and then scale the air frame to match!

 

Edited By Simon Chaddock on 08/01/2019 22:55:26

Thread: New Tv. It's Good But...........
02/01/2019 23:50:40

Our TV normally faultless is showing the same sort of occasional interference.

Now it just so happens that high pressure is sitting right over the UK at the moment. Just a coincidence?

Good flying weather though.

Thread: Dave Burton (BEB)
01/01/2019 17:07:54

My sincere condolences to his family.

He was a major contributor to this site for as long as I can remember.

Thread: Laminations
29/12/2018 00:17:18

If time is not a constraint use thinner strips!

I would bet 1/32 would bend easy enough without any softening but you would obviously need twice as many!

If you want to get really clever use hard(ish) wood for the inner and outer laminations and softer in between. Just as stiff and saves a bit of weight..wink 2

Thread: Prop Clearance Question?
22/12/2018 19:41:33

Richard

Whilst learning all the technical "equations" is to be lauded there is some advantage. at least initially. in going down a fully recommended solution simply because you know it will all work. If it then don't fly too well its probably down to you.wink 2

Although I have a good grasp of the technical issues of magnetism and electricity I had little idea of what combinations of battery, motor and prop would work well enough to fly an RC plane.

Having achieved controlled flight with an out of the box ready to fly plane this formed a starting point for me to change things a bit a a time to alter its performance so it better suited my flying conditions and abilities!

Thread: Gatwick drone incident
20/12/2018 10:23:06

A new form of terrorism?

It certainly gets the headlines!

Thread: IC and Electric
19/12/2018 13:02:32

Trevor

I think you are probably right.

not only are the power curves of IC and electric (particularly brushless) different but with electric the change in motor torque is created the instant the throttle is moved.

Probably not that significant in normal flying but it will produce dramatically different effects opening the throttle when 'low and slow' particularly on light and powerful electric planes! wink 2

Thread: T/E thickness
17/12/2018 20:21:53

I suppose it all comes down to just how 'ding proof' you want (or need) the trailing edge to be.wink 2

With the right carpentry skills it is perfectly possible to insert a hardwood strip for the actual trailing edge or even a carbon strip, however it is the trailing edge so provided it is handled with care "in the hanger" it should have an easier life than the leading edge. Does it really have to be that indestructible?

Thread: Hi all..
14/12/2018 18:28:46

Hi Quentin

I am sure in time you will get to love/hate the UK weather just as we Brits do!

Yes cold is bearable but in time it is the cold & damp that gets a bit "wearing".

I am afraid it is one of the reasons I moved to electric - It always starts regardless of the conditions!wink 2

.

Thread: EDF How to calculate what size needed?
10/12/2018 15:14:54

Stearman65

It does rather depend on how you want the EDF glider to fly.

To emulate the rapid near vertical climb of performance electric gliders you would have to at least double their already substantial power level when using an EDF. This would require very high C rated (and expensive?) batteries to achieve and you will still get less than 1/2 the powered flight time compared to a folding prop installation of equivalent performance.

Adding more battery capacity to extend the flight time will obviously reduce the climb performance proportionally.

In practise the only reason for using an EDF is where scale air frame appearance takes precedence over performance limitations or that you simply want to do it regardless!.wink 2

.

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