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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: DH 91 Albatross
20/08/2018 01:00:22

With the wing bolt mounting complete the tail and centre fuselage sections can be joined and with removable nose section built the fuselage is structurally complete.

fusecmplt1.jpg

The nose section is retained by four lugs with a twist on/off action courtesy of special 3D printed formers.

Once in place the nose is prevented from turning by a retaining pin activated by sliding the shallow dome. In the full size it is one of 4 top hatches.

nosepin1.jpg

Yet more 3D printed parts! wink 2

Time to start filling , sanding and painting.

Thread: what is a BEC
18/08/2018 20:45:04

There is no real difference but be aware the classic BEC provides constant 5V although most RC stuff (apart from some of the micro equipment) are safe for 6V.

What is the BEC rating for your ESC.

Unless you are doing something special the on board BEC should be 'adequate' for the servos in a plane that matches the ESCs motor power.

Thread: Stabilisation
18/08/2018 09:49:16

I would point out that the Lemon DSMX stabiliser Rx is 7 channel. Aux2 on the bind plug so you can have the normal 6 channels as well.

At $21.20 I think they are cheap enough to use permanently dedicated to individual planes.

I my experience transferring anything, particularly a gyro, requires significant testing to ensure the set up is correct and any disturbed connectors are sound.

Thread: Servos
14/08/2018 12:43:26

It all comes down to the duty you expecting from a servo.

For a given load cheap servos are likely to wear/fail faster but a fair proportion of that load can come from vibration and linkage friction rather than the actual aerodynamic load generated by the control surface.

With mechanically efficient linkages cheap servo do fine on lighter electric planes. I have 4 cheap 3.7 g micro servos (ailerons and flaps) in a 40" span plane that is now 6 years old and flown regularly.

In any case they are not easily replaceable as the servos were permanently 'built in' as the wing was constructed! wink 2

Thread: Stolen airliner
12/08/2018 14:52:39

I understand he was a qualified aircraft technician but not a pilot.

As a result of this it does make you wonder if some sort of 'key' system will have to be adopted that is required for actual flight that can be issued by a security process to only designated pilots.

Thread: Why not 'cut and glide'?
09/08/2018 13:17:52

If you have the right shaped plane, a ridiculously low wing loading, a belly lander and you time it right, "cut and glide" can take on a new perspective.

Videoed this yesterday but to be fair it took six attempts before I got it exactly right.wink 2

Thread: DH 91 Albatross
07/08/2018 10:39:21

The fuselage mid section built vertically using my "terribly wobbly to start with" technique. wink 2

Mid fuse 1

The formers are 3D printed.

The 6 mm Depron plate between two formers has a 3D printed surround that incorporates the 'nuts' for two of the wing hold down bolts.

Wing mount box

The holes are printed the correct size to be tapped to suite the 4mm nylon bolts.

Mid fuse 2

The completed centre section showing the wing mounting cut out.

Fuse mid wing

More small printed bits will be needed to secure the bolts to the wing.

As this is taking so long I placed the bits together to get an idea of what it will look like.01 Aug 18a

Also to convince me that some progress is actually being made!smile o

Thread: Help with building a depron plane from a balsa plan.
05/08/2018 00:08:04

Darran

Yes you might have to adjust hings to make then fit but how much does rather depend on the size of the model and the thickness of the Depron. By changing the building material you are going to have to get used to building things to 'fit' rather than exactly following the plan construction detail..

Whilst 6 mm Depron may be suitable for formers and possibly wing ribs actually covering the plane in it would be rather difficult. Does a sheet covered balsa plane use the same thickness wood everywhere? True Depron is available in 6, 3 and 2 mm thick sheets.

I haven't built a Dakota in Depron but this Bombardier Q400 is all 3 mm except for balsa spars in the wing, fin and tail plane along with 1/16 ply bulkheads for the motor mounts.

Paint 3 (outdoors)

Even with a proven plan I can only stress how unwise it would be to attempt anything like this as a first Depron build.

I started off some 5 years ago building just a simple Depron 'copy' wing to go on an existing RTF fuselage.

The weight saving using Depron over the original solid foam wing considerably improved its performance to the point the wing eventually failed but I still fly the second 'improved' version on the same, now even more battered, RTF fuselage! wink 2

Low set tailplane

Edited By Simon Chaddock on 05/08/2018 00:15:50

04/08/2018 21:46:57

Darran

The biggest issue with Depron compared to balsa is it is only 1/8 the weight and strength for the same section.smile o

So building from an plan intended for balsa you have to know where and how to use more (ie thicker) depron sections and where the balsa original was sufficiently over strength that a direct Depron substitution is possible.

As far as trimming formers to take account of the thickness of the Depron I wouldn't bother. Yes the fuselage may end up slightly 'fatter' but Depron is so light it will still be a lot lighter anyway and the extra size will only add a bit more stiffness.

Wings are a big more difficult as they more highly stressed anyway and depending on their design the highest stress areas are likely to be beyond the capabilities of Depron.

With the right glue (typically UHU POR) Depron can be glued very well to balsa so it is possible to build up a 'composite' structure where a hard balsa is used for things like the highly stressed wing spars with Depron for the ribs and wing skin.

It does however take a bit of experience, coupled with some trial and error, to arrive at a satisfactory compromise but the final result can give in a very 'efficient' structure that is hard to beat for strength to weight.

What plan are you considering building from?

Edited By Simon Chaddock on 04/08/2018 21:50:19

Thread: DH 91 Albatross
31/07/2018 14:53:33

The wing centre section showing the Lemon 'stab' Rx, the four ESCs and the UBEC.

Stab Rx

A full test of the wing functions using RC.

The final operation is to install the wing retaining bolts but to do this I also need the fuselage centre section.wink 2

Thread: Don Valley mfc Open days 2018
29/07/2018 20:54:33

John
Indeed a pity about the weather but I did at least get one rather nerve wracking flight nevertheless thanks for all the efforts of the club members to prepare the site to the usual high standard.

As all but one battery was unused it took me quite a bit longer to discharge them to storage level than it did to charge them up!wink 2.

Hopefully next time.

27/07/2018 23:02:06

John

Despite the weather forecast I've loaded the car with half an acre of Depron so should be there bright and early tomorrow. wink 2

Thread: Re: Peter Miller's Don't Bin It, Fix It Article
27/07/2018 16:55:20

"Repairs are always cheaper than a new one"

Yes but it rather depends on how much it cost in the first place and how you value your time!

Nevertheless

My Depron 3/4 size 'agricultural' Ballerina modified with its out runner buried within a 9 cylinder printed radial.

06 May 18

06 May18

The result after a 'cartwheel' resulting from a last minute go round having decided it was not going to stop quite as close to me as I wanted - doh! 18 Jul 18

18 Jul 18

But the following day.

19 Jul18

Notice the difference in the front lawn!

Thread: Unwanted realism!
27/07/2018 11:05:56

I fear yesterday was the end of my A4b (V-2 with wings).

10 May 17

Set up to do its usual VTO it rose as normal to about 20 feet and then the fan disintegrated!

No thrust, little airspeed and pointing straight up the result was inevitable. It toppled over and dived into the ground.

The collected bits.

25 Jul 18

The bits of Depron at the back are what was 'chewed up' by the disintegrating fan and ejected out the back along with 7 of the 8 blades! The last one was retained "impaled" into the Depron.

25 Jul 18 blade

Clearly the fan hub burst which is not that surprising as the EDF was not cleared for 4s operation and whacking the throttle fully open from a standstill is likely to be pretty hard on the fan's structure but for a VTO with only aerodynamic stabilisation you have no choice. At 2 years old it is perhaps surprising it lasted as long as it did.

Built only as an experiment to see if a cheap EDF could provide the thrust to lift off an air frame vertically meant it was very light built and delicate but it did achieve the intended result and flew remarkably well. It was never intended as a 'keeper'.

As with my other 'built up' Depron structures all the 'electrics' survived the crash completely undamaged and could be used in something else. wink 2

Thread: Don Valley mfc Open days 2018
26/07/2018 17:55:07

Hmmm.

Just don't look at the wind forecast on "Windyty" for Carcroft at 3 pm on Sunday!

19 kts gusting 38!

Thread: P38 Lightning
21/07/2018 14:49:41

Superb printing but I hate to think of its crash resistance or the possibility of any subsequent repairs.

I will follow with interest.

Thread: DH 91 Albatross
20/07/2018 11:25:18

This is a very slow build but a bit of progress, the motors do all turn and the desired way too! Of course having counter rotating props is not actually scale as on the original they all turned in the same 'Gipsy' way - or in other words the opposite to virtually every other small engine manufacturer!  

Only 'tick over' as the wing was not restrained in any way but very slow and stable none the less.
Just a test 'lash up' so there is quite a bit more to organise the wiring and to install the BEC as well.

Edited By Simon Chaddock on 20/07/2018 11:30:23

Thread: Binding two transmitters
16/07/2018 15:57:44

With Spektrum you can certainly bind two (or more) Rxs to the same Tx 'model match' memory. When binding the Rx 'handshakes' with the Tx to record the Tx's unique code. This process cannot take place to get one Rx to record multiple Txs codes.

Of course with 27/35 HHz you can have more than one Tx drive an Rx, as many people have accidentally found out! wink 2

Thread: Model enlargement
15/07/2018 20:08:54

The other aspect to consider is that most model planes are considerably over engineered (to provide some degree of crash resistance) so a modest increase is size probably does not need much strengthening so Peter's 1/16 method is likely to be quite adequate.

Such scaling does create a problem if the model is only just strong enough in a particular area or prone to a specific failure in a crash. Scaling up will make this weakness worse but how do you know where it is likely to be?

Few, if any, models are designed using the detailed stress analysis of full size so designing, or modifying, a stressed structure comes down to experience based on trial and error!

15/07/2018 00:23:31

fb3

The problem is that all other things are not equal!

In simple terms a beam of 1.5 times the physical size is 3.375 the weight bit it has rather less than 3.375 times the physical strength and stiffness. This means that a bigger plane scaled up and constructed in exactly the same way will actually be a bit weaker for its weight! sad

The plus side is that a physically larger structure makes it easier to incorporate a more complex and efficient structure that makes better use of the material so saving weight and/or increasing the structural strength. In addition bigger planes have more efficient aerodynamics so proportionally require less power to fly.

Scaling a plane up (or down) presents a set of very interesting variables to fly well. wink 2.

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