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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: LEMON RX7
07/07/2020 23:57:10

Martin

I fear the twitching may be the result of the Spectrum module.

My two 7 ch stabs have never given a moments trouble for over 2+ years but it is with a Spectrum tx.

Thread: Martin Baker MB5
07/07/2020 12:44:31

Ray Wood 4

Yes the full size did have contra props and initially the highest ever power RR Griffon at 2340 hp that gave it a superb performance.

The MB5 was considered the pinnacle of piston fighter development not only because it had a good performance but that it incorporated features that would be a benefit in service like its simple pneumatically operated undercarriage, the layout of the wing ammunition boxes to speed reloading and big removable fuselage panels to aid servicing. Even the cockpit layout was considered good enough to be adopted as a 'standard' for future fighter aircraft.

Of course no matter how good the prototype was by the time of its first flight in mid 1944 it could not complete with the ultimate speed of the jet aircraft then in development.

Its cancellation was a great disappointment to Martin Baker so they concentrated on the development of ejection seats and they have proved pretty good at designing those as well.

Thread: A printed but tissue covered wing
06/07/2020 12:19:37

Although the first "printed & tissue" wing worked well enough it ended up a bit heavy at least compared to the Depron original. Could it be made lighter?

A tapered wing with a tapered spar better follows the shape required to resist the bending loads. The spar was still going to have to be in 5 sections limited by the printer bed size but the structural design of each section could be adjusted to better handle the loads involved.

As before the root spar section incorporates the dihedral.

sparroot

Given this particular plane with a Clark Y wing section is likely to be able to pull more positive g than negative I decided as a further experiment to incorporate some carbon tow into a notch printed on the surface of the lower spar flange.

spartow

Otherwise the construction was much a before with printed ribs that were fed in sequence over the spar.

ailerons1

The only difference was the addition of hollow printed wing tips not for any aerodynamic or aesthetic reasons but to support the outer rib against the tissue tension.

The wing is held on with the same three bolts so both printed and Depron wings are interchangeable.

taper-depron

As before it can be rattle can painted after being doped.

taperwing

To within one gram it is exactly the same weight as the Depron wing although it does have very slightly less area.

I am sure it will fly well but the weather will have to calm down some before it can have its maiden.

Still quite a time consuming task to actually put the parts together but atleast it equalled the Depron in weight.

The next question is keeping to the same 1000 mm span would it be possible, using no Depron or carbon, for a complete plane to weigh less than 250 g?

Edited By Simon Chaddock on 06/07/2020 12:23:09

Thread: How Many Wing Ribs
04/07/2020 22:59:40

The spacing of the wing ribs largely depends of how accurate you want the wing section to be. The ribs may be a nice NACA section but the area between the ribs will not. The closer the ribs the nearer the section will be between the ribs.

Now whether the change in the wing section between the ribs makes any significant difference to the performance or handling is another matter. wink 2

Thread: Lightwight foam cowl, Tissue with EZE Dope or thinned PVA?
02/07/2020 18:05:20

PVA and tissue on foam is safe enough. I done it several times. The quality of the tissue can make all the difference as to how easy it will be to do! wink 2.

Thread: propellers
01/07/2020 19:15:11

simon w

Just out of curiosity I looked on ebay for those 10 times 8x6 and they should do fine. Do make sure the prop is a good close fit on the motor shaft using the correct bush included with them.

Remember a prop blade is twisted at a different angle along its length, shallow at the tip but near the root the shape is set by the loads generated when it is working.

The vast majority of the thrust is created by the outer 2/3 of the blade. The bit near the root contributes almost no thrust but it does stop the outer part flying off. wink 2

Thread: Prop advice please.....
28/06/2020 22:32:28

I should ask the questions "What plane is it?" and "How much does it weigh?".

With electric flight most motors and props have about the same efficiency so comparing electrical input to plane weight give a good indication of what sort of performance can be expected.

If the Watts/lb are much below 100 then you wont get much extra performance without straining the 3000 mAh 3s.

Thread: Cg - Skynetic Shrike
25/06/2020 23:26:01

At 850 g the Skynetic Shrike definitely needs you to be CAA registered.

The fines for not being registered are are quite severe if something goes wrong and it is discovered you are not registered.

As a powered glider it certainly should have flown provided the CofG was in the right place as stated in the manual. Does the manual give a range of positions?

What radio were you using and did you check the controls were operating correctly? If they were not then it was never going to fly properly if at all.wink 2

Edited By Simon Chaddock on 25/06/2020 23:53:12

Thread: Hobbyking EU delivery times?
20/06/2020 10:18:33

According to my Royal Mail driver son-in-law one of the effects of Covid-19 has been a huge increase in the volume of parcel mail with people shopping on line. He says the volume is at near Christmas levels and has been for a couple of months. Doubtless Europe is similar so expect delayed deliveries.

Thread: Spitfire cannons
19/06/2020 13:20:00

Richard Clark 2

You may be able to draw a scale Browning gun barrel but could you then make 8 of them as Tony B did in a reasonable length of time?

3D printing does have its strengths, particularly where multiple copies are required.

Thread: DH Tiger Moth 1400mm
18/06/2020 21:28:08

Bob

Superb!

That is amazing detail.

Unless you can find an motor that goes the same way round as a Gipsy the prop will be wrong too. wink 2.

Thread: Where can i buy 2mm pushrods 750mm long
13/06/2020 12:40:27

Chris

I appreciate you are working with an already built model but at some point the weight of really long rods/snakes is better addressed by simply moving the servo towards the tail or in the extreme putting the servo at the tail with a short direct linkage!

It is mechanically more efficient so the servo can be smaller/ lighter and still generate the same force on the control surface. wink 2

Just saying.

Thread: Help! New aerial for Spektrum Rx.
12/06/2020 19:14:53

There was time when most 2.4 gh 6 channel rx only had one aerial.

I still have several planes that I still fly with a single aerial 2.4 rx.

For a small foam job just stay 'in line of sight' and below 400' - like you are supposed to. wink 2

Thread: Lipo lead question
09/06/2020 10:53:47

It is normal for a 'Tx' LiPo to have several different style of plugs so it can be used with different Txs.

All the red and black wires are connected to the battery + & -..

My 2200 3s Tx LiPo is left connected but is always balanced charged.

Thread: A printed but tissue covered wing
09/06/2020 08:33:02

With the particularly calm weather yesterday it has it maiden and it flies.

Sorry about the video I did not centre the camera correctly so it was always pointing a bit to the left.

Plenty of power and it did loop and roll without breaking.

Does this method of construction have any particular advantage? Not really unless you are desperate to build something, have a 3D printer but no balsa or foam! wink 2

It has been an interesting exercise.

Now if the printed structure could be made from a plastic that could withstand the heat involved for a shrink film and with a carbon spar the result might be rather more practical.

Edited By Simon Chaddock on 09/06/2020 08:33:30

08/06/2020 14:33:13

Testing the completed wing with ailerons added.

Although quite adequate the tissue does not stick particularly well to the PLA even after it has been doped so it gives a rather blotchy appearance over the red framework.
As there is no foam in the wing it could safely be painted with a 'rattle can'. Even a light application of "chrome silver" gives a very 'solid' covering.
silverwing2
The wing ended up weighing 132 g so adding 51 g compared to the Depron original but at 464 g (16.4 oz) ready to go and with 160 Watt available it should still have a 'spirited' performance.
06/06/2020 22:36:20

With the Depron wing carefully cut away from the fuselage suitable wing mounts for the M4 nylon bolts and threaded fuselage mountings could be designed and 3D printed. Printed mounts for the aileron servos were added.

Took the best part of a day of trial and error to get it exactly right.

wingon1

There are two bolts just ahead of the spar and a single central bolt at the wing trailing edge.

The servo wires run through holes in the ribs 'melted' with small soldering iron.

This allowed the tissue covering to start.

tissue1

Thread: Servo Advice
06/06/2020 17:02:44

My own view is the installation of the efficiency of the linkage and hinges has more to do with servo reliability than differences between brands.

Provided the servo is adequately powerful for the duty and all the available servo force is actually transmitted to the control surface it is much more likely to be damaged by a crash or handling than to fail in service.

Thread: Just saying hello!
06/06/2020 12:37:59

Robert

An impressive build.

Whilst I can fully appreciate the reason behind the layout of your undercarriage it is generating a horrendous lever on the retract servo.

The full size, although with a hugely complex action, was at least fully braced spreading the vertical and horizontal loads between the front and rear spars.

I must admit i can't immediately think of an easy solution but I fear a 'pulled' U/C will always be a risk.

Thread: Electric help required
04/06/2020 22:17:52

Dougie

Outerzone have a plan and a 'period' review of the Astro Flight Porterfield Collegiate.

The original kit came in at 63 oz although it was suggested that a heat shrink film would save up to 8 oz over the cloth and dope used.

A Brushless motor and LiPo instead of a geared brushed and NiCd would save some more weight so my guess is it would be realistic to assume it might be near to 48 oz or 3 lbs particularly with modern lightweight RC gear..

At that weight a 450 Watt motor would give it a 'lively' performance with a power loading of 150 Watts/lb. It would cruise 'sedately' with a corresponding increase in flight duration on less than half of that figure.

I hope this helps.

Edited By Simon Chaddock on 04/06/2020 22:18:32

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 Yes - for the first time
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