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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: Airbus A350 for 50 mm EDFs
11/12/2017 12:32:53

How will it be launched?

Well certainly over head! Its not the weight that is the problem but how and where to hold it.

There is quite a large flat sided area under the wing to contain the U/C on the full size so there is a chance that will provide sufficient surface to get a grip. It has the advantage it is also in about the right place.

Underside

And there are two NACA ducts in just about the right place for cooling air to the ESCs. wink 2

09/12/2017 22:45:36

the tail fin fixed to the tail plane.

Tail fin 1

On the full size the fin spar passes in front of the tail plane so it needed some 'printed' brackets to fix securely and with the right sweep angle.

Tail fin 2

When the tail plane assembly is mounted in the fusealge all the bracket will hidden.

08/12/2017 16:45:17

The tail plane in progress. It is quite modest in area but by comparison the elevators are pretty generous.

Tailplane 1

There are no ribs, just a shear web and 2 mm Depron skins. A printed U channel spar supports the elevators. The elevators them selves have a hard balsa leading edge to provide the necessary torsional stiffness. The horn will be on the inner edge of each elevator as the micro servo can only contained within the tail plane at its root.

The fin will be built directly onto the tail plane. The rear of the fuselage will then be cut open and the whole tail assembly glued in place

Well that's the plan! wink 2.

Edited By Simon Chaddock on 08/12/2017 16:46:26

Thread: Twin power set ups
08/12/2017 00:20:18

Now if you have an 'inline' twin a motor out is not a problem provided you have the power.

Complete

I can, and do, switch one off for fun or for maximum endurance.

Thread: Airbus A350 for 50 mm EDFs
06/12/2017 00:54:27

Thanks for the kind words gentlemen but things do go wrong!

The centre part of the fuselage was originally just a 'test' to prove the construction technique but it got incorporated into the working fuselage.

At that time I had not even considered the wing construction or its section so the bottom line is the wing does not fit properly onto the underside of the fuselage! sad

After a bit of thought the only solution was to reprofile the wing mount which required the fuselage underside to be cut open and I would then have a find a way to repair several un-repairable printed formers. smile o.

Cut out 1

Printing new cross beams and simply gluing them in proved relatively simple.

The wing will now fit 'snugly' and more important at the correct angle of incidence.wink 2

With the fuselage underside temporarily 'open' it will also make running the long rudder and elevator servo wires a great deal easier so the tail plane and fin are top priority!

Edited By Simon Chaddock on 06/12/2017 00:55:39

05/12/2017 17:36:33

To save weight the motor wires are extended using 16 AWG lacquered magnet wire.

A short test on a 2s to make sure the soldered connections are sound.

With the nacelles glued into the wing and all the wires brount through the wing down to the root the wing halves can be glued together.

Wing complete 1

The nacelle glued into the wing.

Wing complete 2

All complete it weighs 9 oz (255g)

Thread: Two Tiny Motors
05/12/2017 13:44:25

I suppose it all depends on what you call a 'tiny' motor.

OneTenor's are the same diameter but 3mm 'thinner' than the pair I am using for my Airbus A350 and that has a 60" span!

Edited By Simon Chaddock on 05/12/2017 13:45:57

Thread: Full size landings
03/12/2017 19:07:21

From my gliding days I certainly would consider double deck bus height very high to flare.

I took one of our tug pilots up in our Bocian 2 seater to give him a glider pilots perspective.

No problem for him to fly it except lack of use of the rudders in a turn but the biggest comment was on the landing where he said you just flew it onto the ground.

This is largely true as when compared to a tail sitter (Auster) the glider fuselage sits on the ground almost at the normal flying angle.

If you really try to 'hold off' to virtually the stall angle, as the tug pilots do, the glider nose will drop at good 6 feet before the wheel touches the ground and you will likely break something... .

Thread: 2 and 4 STROKE DESIGNS
03/12/2017 01:25:57

It is a bit unfair to compare aero and road going engines as they have different aims. Aero engines seek power to weight rather than power to capacity.

If you have the inclination and the skill you can build a true hemi head model engine although you have to get clever with the rocker and push rod alignment to do it.

I have actually run this 60 year old 5 cc petrol but it was made by my Dad.

5cc1

The engine on its 'display' stand.

display1

Long before the days of electronic ignition so it has 'points' and a coil.

With a scavenged sump and positive feed to the big end from a separate oil tank it runs on ordinary 'pump' petrol.

From memory it turns a 9x6 at close to 10,000 rpm. Quite a modest performance but it was built for fuel economy over power.

Edited By Simon Chaddock on 03/12/2017 01:34:45

Thread: All moving tail
03/12/2017 00:34:19

Flyer

Compared to a conventional elevator an all flying tail with its pivot close to the MAC is in effect almost fully aerodynamically balanced. On this basis it is not "should I make the elevator servo bigger?" but "could I make smaller?". wink 2

The bigger issue is the extreme effectiveness of an all moving tail with small angle changes which means there really must not be any slop or flexibility in the linkage.

Thread: Full size landings
01/12/2017 16:31:44

If you don't mind spending a rather geeky 20 minutes watching 10 landings it does seem not all do exactly the same thing but all do flair (or reduce the rate of descent) to some degree just before touchdown.

The A320 was probably the best 'greaser' but in most cases lowering the nose and opening the lift dumpers causes the undercarriage to squat down rather than any impact with the runway.

From a model flyers point of view what is noticeable is how beautifully constant is the rate of descent on finals!wink 2

Thread: Airbus A350 for 50 mm EDFs
01/12/2017 11:07:19

The outer wing panel is a remarkably simple affair. All 2 mm Depron with no ribs or spar just a pair of shear webs.

Outer panel 1

The 'curled up'wing tip is sanded from a pre-formed blank of 4 laminations of 2mm Depron glued together and held with rubber bands over a suitable diameter cardboard tube until dry..

Tip blank

The tape top hinged aileron is cut out from the wing. and a 3.7 g servo inserted through the wing bottom skin. At the inboard end of the aileron the wing is just thick enough to hold the servo which is simply glued between the top and bottom surfaces.

The linkage has considerable mechanical differential incorporated in the linkage.

The inner and outer panels glued together.

LH wing 1 This shot does rather highlight its extreme root to tip taper.

With no ribs in the outer panel and open braced inner wing ribs feeding the servo wire through is fiddly but no real problem.

The half wing and the nacelle, complete with motor and prop, weigh 140 g which suggests the target weight of 24 oz (680 g) is achievable.

Edited By Simon Chaddock on 01/12/2017 11:09:25

Thread: Legislation Proposal at last
28/11/2017 23:28:34

The CAA may not be aiming for model plane flyers in particular but if the legislation has to include the safety of the general public at large, as distinct from the safety of other man carrying aircraft, then if is hard to justify that a model plane is any safer than a multi rotor of the same weight, in fact as planes tend to fly faster - it isn't! wink 2

Thread: Airbus A350 for 50 mm EDFs
27/11/2017 11:09:40

The first inner wing panel complete.

LH cmplt

The nacelle pylon fits in the wing slot.

LH under 1

The complete wing and nacelle (including the motor and ducted prop) weighs 98 g.

As it all seems to fit together the 8 individual parts for the second nacelle are printed off.

2nd nacelle 1

This is where printing really excels. Although the above represents about 4 hours printing it only requires a touch of a button (well almost!) and all the prats fit together perfectly. wink 2

Just out of interest a comparison if the root and tip wing ribs.

Root Tip

It does show just how tapered the wing is and the curved up tip "winglet" is even smaller still!

Thread: Peterf's twin 90mm EDF Blackhorse Mig 29 build log
25/11/2017 20:53:32

Very nice!

Thread: Build a model from twisted wire?
24/11/2017 22:31:20

I think if you do some bending tests (bending is what occurs in air frames) you will find that a twisted wire on its own makes a poor 'beam' for its weight and its not that good as a compression strut either if it is used as part of a 'built up' structure.

In most high strength to weight structures it is how the compression forces are accommodated that tends to limit how light it will be.

Mr Wallis's 'tubes and flanges' make structurally efficient use of the material wink 2

Thread: Eric "Winkle" Brown
24/11/2017 22:04:44

And it will be virtually impossible for anyone to ever again accumulate as many different military aircraft types in his log book!.

Thread: Anet A8
24/11/2017 12:35:00

One area where 3D printing excels is in duplication. wink 2

These are the 8 individual pieces (2 on the left, 6 on the right) that make up the 2nd nacelle for my Airbus A350. The initial components took quite some trial and error to get right and although this picture represents about 4 hours worth of printing it was all done at the touch of a button (well almost!) and the bits all fit together exactly. Oh joy!

2nd nacelle 1

With very thin (0.3 mm) walls and single layer (0.2 mm) bottom surfaces to save weight it is about at the limit of what my A8 can reliably print so it was important to print everything whilst the machine maintained its physical settings. Even changes in the ambient air temperature made a difference!

Thread: Pesky Little 1S Lipos!
24/11/2017 09:20:03

brokenenglish

I would avoid leaving any LiPo for long periods (months) fully charged. At best it reduces the available capacity a bit, at worst it can cause what happened! Yours is a big cell with a lot of energy in it.

Unlike other cells LiPo do not like 'low slow' charging. The important factor is the cell voltage must never be allowed to exceed 4.2V. This requires the charger must absolutely stop charging as soon as that voltage is reached.

My bench test LiPo is used 'as required' and it is only charged when I think I have used at least half the capacity and I want to use it some more, otherwise I leave it alone. It is a retired (slightly puffed) flight battery and is now 3 years old.

Thread: Anet A8
23/11/2017 16:49:43

I get mine from Ebay too.

**LINK**

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