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Member postings for John Cole

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

Thread: Hello, Retired and restarted hobby after 40 years
24/01/2013 12:51:42

Well worth looking through the specific section of this forum for Beginners.

I also returned to hobby after a long absence. My advice:

1. Join BMFA to get the Insurance - important even for a small model.

2. Get a Simulator to run on your PC and a lead to connect your Tx to a USB port.  Flying RC model planes is great fun, but initially not easy.

Practice on an RC plane simulator helps.

Edited By John Cole on 24/01/2013 12:52:32

Thread: What goes up - questions
24/01/2013 12:42:49

When a wing stalls, it loses some but not all of its lift. You can think of the lift as coming from increased pressure below the wing and reduced pressure above it. Close to (but below) stalling speed most of the lift comes from the latter. At the stall, the lift from below the wing is slightly increased. That from above the wing is much reduced. So at and just beyond the stall, the wing does not generate enough lift to support the plane without increasing airspeed.

The Lift Coefficient just below stalling AoA may be about 1.0 (for e.g. NACA 0012) and drops at slightly higher AoA down to about 0.6, but it then rises to above 1.0 at AoA of 35 degrees. This data is for Re similar to ours, ignoring end effects.

So the stalled plane can continue to fly supported only by aerodynamic lift, but at a much higher AoA. The section drag coefficient at this high AoA is much increased. This is of course exactly the condition produced by a dethermaliser.

DB's statement that "at the critical point (i.e. at the stall), most of it (i.e. lift) disappears instantly." is I think slightlly misleading, but MANY authors claim ALL lift disappears at that point - nonsense. However you will need to look hard to find good wind-tunnel aerodynamic data on performance at AoA significantly beyond the stall.

 

Edited By John Cole on 24/01/2013 12:43:36

Thread: Won't supply to Scotland - Kings Lynn for a start, but who else?
24/01/2013 10:39:14

KLM DO in fact deliver to Aberdeen. They do not deliver to some areas some distance to the north and north west of Aberdeen that have a postcode starting with AB (AB 37 38 41 42 43 44 45 51 52 53 54 55 56). They DO deliver to all other AB postocdes (Aberdeen City, west to Ballater, north of Dyce).

If you lived in Aberdeen or close to it then they would deliver to you.

Thread: trying to find what magazine this appeared in
23/01/2013 19:31:02

There's a topic called "Sales, Swaps, Wanted's and Giveaways". Try there, starting a new thread called "BMFA News, issue 111". Might help if you give the date, too.

23/01/2013 19:15:06

I shold repeat that on a new thread if I were you.

Not much to do with Falcon / min - e - falcon

Thread: Folding Pusher Prop - Help please
23/01/2013 14:36:47

Thank you all for your comments and suggestions.

Simon: what you say about cleanliness is true on the glide, but with power-on there's a significant improvement in efficiency in pusher mode, as the fuselage is not in the prop-wash.

Thread: Credit where credit is due. Very good customer care from GiantShark.
23/01/2013 10:06:20

FIrst class post: I've just had a Christmas card + letter delivered 4 weeks after the date printed on the envelope by Royal Mail and posted first class.

If domestic mail is delivered 3 days or more later than it should be then provided you can show this you are entitled to a book of 6 First Class stamps.

Thread: Folding Pusher Prop - Help please
22/01/2013 19:21:15

Wingman: O/D canard. Yes, low kV motor.

Simon: thanks. Good point about reverse-opening. I think I would need to put some kind of stop in to prevent that. It's for prop-protection not aero. With this size of prop I was concerned that a standard O-ring based propsaver could drive the prop into the aileron of the canard's wing, damaging it.

22/01/2013 17:17:17

I am building a 1-kilo model that will need a folding pusher prop. to go on a 5 mm shaft 300 watt motor, probably an 11 * 6 conventional prop equivalent. I know nothing about folding props, but almost all the ones I see are used in tractor mode.

Do I need to buy something special, or will pretty much any folder do?

Do I need to leave the spinner-part in place, or remove it?

Thread: trying to find what magazine this appeared in
22/01/2013 11:57:34

It's available from Traplet so presumably one of theirs.

Thread: flight times query??????
20/01/2013 19:14:43

1. Tie a string to the tail and tie the other end to something solid.

2. Switch on and advance to half power, and start a timer.............

Thread: Switch Repair
20/01/2013 13:20:50

Peter: rates controlled by a pot on a "computer" Tx?

Thread: Plan download unzipper?
20/01/2013 11:14:36

If you right-click on a zipped file, the Windows drop-down menu gives you the Extract... option.

Thread: Switch Repair
20/01/2013 11:08:42

I would assume it's a 2-way switch. Look inside and see if it has 3 wires attached: common. high and low.

Thread: how do you store or what do you store your lipos in during winter
20/01/2013 11:06:19

Avtur: See my reply above.

19/01/2013 19:47:59

Provided the plugs are correctly insulated, stored LiPos are very safe. But it's best to part-discharge them before storage as otherwise they lose a little capacity over time. It then doesn't matter what temperature you store them at, provided it's cool or cold. You will see people saying the "mustn't freeze". They CAN'T freeze as they contain hydrocarbons not water. They are certainly safe to minus 20 degrees C: the temperature of a domestic freezer.

Thread: 787 problems
19/01/2013 10:29:03
Posted by Simon Chambers on 16/01/2013 14:02:18:

Interesting article here on the failure modes of a LiIon cell (which LiPo is a type of): **LINK**

I find this visualisation most interesting:

Some of the data shown here is not consistent with that published by Sony - who make them. Specifically the Collector dissolving does not occur above 1.1 volts, and the safe minimum working voltage is below minus 20 degrees C, though they should not be charged at below 0 degrees C. There appears to be no lower safe limit to storage temparature. No metallic plating below 5.0 volts. Must not rupture within one hour at 130 degrees C.

See: Sony Lithium Ion Technical Handbook

Thread: February 2013 issue feedback
18/01/2013 15:26:18
Posted by GrumpyGnome on 18/01/2013 15:08:21:

Not too sure about the survey on page 9 - I'm sure when I was in school, you couldn't have 138% of respondents smiley

Well, you can if you are allowed to tick more than one box. But in this survey it seems that exactly 69% ticked one (or more) of the top-five boxes and 69% also ticked "Can't remember". The second figure implies that 31% did NOT tick that box and ticked at least one other box. But 32% ticked "family introduction".

THEREFORE some people must have ticked "Can't remember" AND another box.

Or possibly a typo not picked up in proof-reading.

Thread: Cold weather storage
18/01/2013 15:11:15
Posted by Martyn K on 18/01/2013 14:19:17:
Posted by John Cole on 18/01/2013 13:47:09:

I think any problem is likely to be caused by humidity / condensation rather than low temps. In which case a dehumidifier is going to be cheaper to run than an electric heater. I use one.

Thanks for the suggestion, I'll see if I can find one in our local bargain shop.

Martyn

Some people sell water-absorbing crystals as a "dehumidifier". That's not what I mean. What I use essentially contains the workings of a fridge, a fan and a water collector bucket and is electrically-powered. Something like This. Might get one from FreeCycle / Freegle.

Thread: Is it possible to open adverts in a normal window?
18/01/2013 15:01:49

Chrome obeys the Control Panel settings.

If FF doesn't then scroll though the FF settings pages until you see something similar.

Or switch to Chrome - it's quicker.

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