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Member postings for Nigel R

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

Thread: Design & Build Sport Twin
26/03/2019 17:30:22

Must confess I've been rather distracted from this of late, getting some foamboard airframes up together. Anwyay...

20190311_230546.jpg

...there are some U/C doublers are being stuck in - 1/32" ply running between the two pairs of spars.

Which brought me to...

20190325_223545.jpg

...getting the lower wing sheeting being applied, with contact adhesive. I pin down some blocks to hold the spars straight and in the right place, and use jig strips at the TE to keep everything straight. Two cocktail sticks get poked through the sheet into the spar to keep the sheeting aligned during the whole operation. Takes me about 20 minutes to get a surface done by the time the glue is on and dried and it is all pressed down and stuck.

Next job is to install the 1/4" ply U/C blocks, before the the upper sheeting goes on. I'll be using a torque rod U/C so the inboard end gets a second ply block.

Next time I don't think I would bother with two spars, it took a fair old while to double up on the bits and put them all in. I think I'd just make the main spar a bit more solid, maybe use 1/4" square spruce or basswood.

I'm still wondering whether it is worth putting in some flaps. Might be a bit tricky at this stage. But I could still chop the ailerons in half and add extra servos. Hmm.

Thread: Electric Cars.
26/03/2019 17:06:00

Are the beta testers always pleasantly surprised when they are able to charge quickly on a public unit?

Percy, you are very fortunate to be in a position to be able to do that. I might be able to charge from the mains, but no chance of solar or a storage battery in the garage (no garage), and many people will not be able to charge at home because of not having off road parking (new estates, flats, inner city, etc).

And I agree as soon as electric hits mainstream numbers it will be made to be as expensive as running a full IC car, that tax take is not going to be missed.

Edited By Nigel R on 26/03/2019 17:11:47

26/03/2019 16:29:58

2.5million cars were sold in the UK last year, of which 60000 were electric, two thirds of those were plug in hybrids (money's on them being company cars bought for tax exemption), leaving 20000 electric only.

So, less than 1% of all cars sold in UK last year were electric.

We're not at "serious uptake" yet, by quite a long way.

Nobody runs their electric shower for 9 hours a night.

 

Edited By Nigel R on 26/03/2019 16:31:27

26/03/2019 16:19:34

I have approximately zero confidence that I could do a family holiday in the south of France by EV. Maybe I'd have to accept hiring a car to do a self drive holiday. Or flying and hiring. We're not loaded enough to have a special away trip car as well as an EV.

My family are 130 miles away. Obviously that's within range. But not a round trip, if it was needed, without a charging stop. It probably will be at some stage.

Are you serious about the infrastructure comment? The video above sums up where the infrastructure is at. Patchy, at best. As for charging at home, can our existing grid cope, I can't recall the outcome of that discussion, but yes, for most trips charging at home would work for me.

Thing is, all of the above goes away if you have a plugin hybrid. As it does for most people. It is, the sensible transition option.

Thread: LiPo Internal Resistance
26/03/2019 14:53:31

Heat is pretty much the prime dictator of how fast battery chemistry changes (well, degrades, more specifically) so it's a sensible limiting factor to use. IIRC about 40 degrees at the end of a flight is about as high as you'd want to go.

Taking battery weight would add more complexity to the equation - IIRC the weight per unit capacity is quite constant across a reasonable range of "C" ratings, so it would make a good enough proxy for a rule-of-thumb type calculation.

26/03/2019 14:11:05

Interestingly (and quite reassuringly from my point of view) the equation posted by PeterF effectively converts to conductance first...

"Max current = square root(6 * Capacity / IR )"

The "capacity / IR" term is the last column in my post.

The square root operation is the reverse of working out dissipated heat by using current squared, or another way of putting it, this looks like a rule of thumb for "max heat per unit weight of battery"... and working backward to get the current which will cause that amount of thermal energy. I'd assume "6" is an arbitrary value worked out from "if it gets hot" type checks...

"Effective C rating = 1000 * Max current / Capacity"

and then turn that current into a C rating.

So I'm not sure I'd explore my post too much because it seems that exploration is already done

Thread: Electric Cars.
26/03/2019 13:35:22

Absolutely that. I'd buy a hybrid without thinking twice. I'd not buy an all electric, at all, yet. But I think we've all said this before, no serious infrastructure means no serious uptake of full electrics.

On the other hand, I would absolutely buy an electric vehicle for commuting to work, but it would cost very little, have two wheels and go at a top speed of about 20mph.

Thread: LiPo Internal Resistance
26/03/2019 13:26:45

I haven't got any more complex than "if it gets hot when you come down, and the flights have got shorter, its getting old and tired."

to answer your question a bit better, conductance is the reciprocal of resistance, and I would expect to find that, given a consistent C rating, the conductivity is more or less proportional to cell capacity.

Just checking your figures:

3300 mAh, 8 mOhm (1/8mOhm = 125 S) = 37.9 S/Ah
2200 mAh, 11 mOhm (1/11mOhm = 90.91 S) = 41.3 S/Ah
1800 mAh, 20 mOhm (1/20mOhm = 50 S) = 27.7 S/Ah
1600 mAh, 22 mOhm (1/22mOhm = 45.45 S) = 28.4 S/Ah
850 mAh, 35 mOhm (1/35mOhm = 28.57 S) = 33.6 S/Ah
280 mAh, 140 mOhm (1/140mOhm = 7.14 S) = 25.5 S/Ah

in brackets is the basic conversion to conductance (in Siemens, "S"

the last figure is the conductance normalised by cell size

they're all quite close!

The 2200 packs come out quite good, are they a higher C rating?

Thread: Help with heat shrink film on rounded fuselages please
25/03/2019 14:02:41

"Am I doing it wrong thinking I can cover the whole top and sides of fuselage in one go? "

I think you'll struggle.

I would make a seam running along the top of the sides (assuming the sides are flat and the top deck is curved).

You could try making the seam along the top centre, doing one underside piece, and two side/top pieces. But, the taper of the fuselage will make it trickier than using four pieces.

On that basis, I'd go with the usual four piece method, bottom, sides, top.

Thread: What's your rate limiting step?
25/03/2019 10:36:29

Ribs. Loads of identical bits, all need to be accurate. Not the most interesting bit. Rest of wing build is ok. But I always try and get the wing done to nigh on complete first, before doing anything else.

Sorting pushrods and controls. Always seem to make lots of small mistakes when doing this. Should probably learn something from that.

Thread: Spektrum Radio repairs ?
25/03/2019 10:26:09

David, fair points, thanks for explaining

Thread: Does your club prohibit the use of after-market receivers?
25/03/2019 10:23:34
Posted by David Davis on 25/03/2019 06:43:06:

I have an Orange DSM2 receiver and a spare remote aerial from a Spektrum AR6200 receiver. Is there any reason why these may not be used together?

If such a combination would improve the performance of the receiver, I have two transmitters which I could use, a Spektrum DX9 and a Spektrum DX6i. Which transmitter would be better or are they both equally compatible?

The Orange remotes are supposed to work with Spektrum RXs, so presumably that implies compatibility and that it should work the other way around.

DX9 has two aerials, I believe. DX6i has one.

That said, I have personally not had any radio link performance issues with my DX6i (I did break that fiddly weak aerial hinge, of course).

Thread: Help with heat shrink film on rounded fuselages please
25/03/2019 09:24:45

"Is there a 'knack'."

A prehensile tail is quite useful, as are feet that operate a bit like hands.

Failing that (!) you just have to stabilise things with your knees a bit. It's always awkward.

"not easy is it when the fuselage isn't square"

Can only echo the above advice. Cut oversize, by a good few inches (its not waste if you need it to get the stuff on properly). Tack down the centreline, then s-l-o-w-l-y stretch and stick the film (it will mostly stick by itself if you are stretching it against and around the curved structure), bit by bit by bit, using the iron at its normal temperature. Start at the middle, work outward. Don't rush it, don't use a heat gun, don't turn the iron up. It's amazing what the film will conform to given time, moderate heat and a bit of tension. Even really tight curves. Do use a fresh scalpel to finish up, and blades only seem to cut cleanly for one lump of structure (e.g. the fuselage) before they're a tiny bit blunt and start to tear the film - factor that in, get a new pack of blades, don't be shy about changing blade regularly.

Thread: Spektrum Radio repairs ?
22/03/2019 11:14:21

indeed it will, I suppose I was questioning whether you thought it was a pure money grab move or whether it might represent a consolidation to improve the central repair effectiveness whilst farming out the simpler repairs to a 'franchise' (as it were).

another question or two if I may, do you believe multiplex take a different approach?

or is your potential switch more to do with the reliability of kit?

PS not trying to be awkward or provocative, although realise my earlier post could have come across a bit blunt

21/03/2019 15:22:46

"In my view the reason for moving all of the service and repair work to one single location in Europe is to make more profit for the owners."

Do you know this, or is it assumption?

Thread: Servos 3d model
21/03/2019 14:57:46

Well, they would, wouldn't they?

I'd go analogue - less load on the BEC.

The XL-17HMG look very similar spec (speed, torque and weight) to the HS82MG, I can't see any reason they wouldn't work.

HS82MG, set of 4 is £55.

XL-17HMG, 4 for £45.

Thread: NEW POLL - Does your club have a safety officer, or is the emphasis on individual members to each be their own safety officer?
21/03/2019 14:30:45

I need to be able to vote both.

But I rarely see the safety officer, he flies Sundays, and I don't.

We look after ourselves fairly effectively. We have a few simple rules. And hopefullly, enough common sense to fill in the gaps.

Thread: Dekan Simple Delta
21/03/2019 14:13:54

Quick update, I've changed the motor.

It's now sporting a 2500kv thing, spinning a 6x4 prop at lots of revs. This draws 220W!

It is now quite fast. Although with the electrics hung out in the breeze, there is scope to make it faster with some fairing.

Thread: Pizza Box Flyer
21/03/2019 14:04:58

Had a few more goes today. Increased movement to about 60deg on all surfaces - perfect. I also cleaned the muck off the prop, which made quite a difference.

This thing really encourages totally daft flying.

I spent most of the flights harrier/hovering at just a few inches above the grass.

A few donks, but at near zero forward speed and near zero height, nothing gets damaged. Pick up, relaunch, continue with the absurd.

Absolutely brilliant fun!

Thread: Does your club prohibit the use of after-market receivers?
20/03/2019 17:22:50

Agreed Don, but I had to ask... hard to drop the engineering habits sometimes.

Trees move at an astonishing rate, and fences and hedges have a remarkable ability to change height.

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