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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: Single servo ailerons
15/08/2019 10:24:20

Hmm.

Regarding oversized engines and servos.

With double the power (90 vs 45) our metaphorical Acrowot won't be flying that much faster (approx 25% if I remember my basic drag vs power calculation right).

Perhaps another way of stating it - the force on the controls is not massively increased.

I've used the servcalc.xls (can be googled and downloaded) spreadsheet for a while. A big assumption on my part is that is correct.

Anyhow, it shows:

For a 18" x 1.25" aileron surface, at 50mph, surface deflected 30deg, servo deflected 45deg - a fairly standard setup for a 40 class sport aerobat I would suggest - the required torque is a mere 2.5 oz-in (per aileron). For both together, a still tiny 5oz-in.

Now up the speed by 25% or so, after fitting that big 0.90. I'm rounding up a bit here, to 65mph. The same surface now needs 4.2oz-in - for both a total of 8.4oz-in.

How much does an antique S148 have available? 33oz-in.

Our Acrowot will need to travel at 125mph before that poor old Futaba is overwhelmed.

If the .45 gets the AcroWot to 50mph, then 125mph in straight and level would take just over 6 times then power. I leave the size of that 2 stroke glow to your imagination. Yes, you might get that in a full power dive, although with an Acrowot, I'd be surprised, it is no pylon racer.

If you want faster response, yes, you could replace the assumed bargain basement standard slow old analogue servo. But, you still need only go to a singular servo.

If you really want to use two servos, go ahead, this is all for fun after all, and using two servos is certainly a thing that works.

But the argument against the single servo on the basis of speed or power simply doesn't hold any water.

Thread: Even Later In The Day
14/08/2019 17:42:23

yes, put the build up! yes

Thread: Electric Cars.
14/08/2019 17:23:48

Agreed, Don.

**LINK**

The pie chart is interesting though; cars at 40% are clearly the biggest "single contribution" to greenhouse gas emissions.

If we all drive electric cars then all that section simply drops off the chart and moves into another graph labelled "emissions from power generation" which conveniently makes it a somebody else's problem (apologies to Mr Adams) as far as the car industry is concerned.

On a more serious note, air travel is so much less frequency that, despite its very high emissions, it is still a quarter of the private car emissions.

Also on a serious note, I see that emissions and waste from brakes and tyres are being examined in electric cars, perhaps with a view to using these components as a proxy measure for levying an electric car version of the road tax.

14/08/2019 17:13:47

Shaun - thank google not me smiley

Thread: Design & Build Sport Twin
14/08/2019 15:47:07

Many thanks gents smiley

Denis I have had the same thoughts a number of times throughout the build - the day is not too far off now!

Thread: Electric Cars.
14/08/2019 14:11:55

Actually not sited in Nullarbor - it's a test site in urban Oz (Perth) in use as to work out whether a static diesel gen plus EV is better than a diesel car alone, according to google.

**LINK**

And, its working out better* than a vanilla diesel bus according to the operator's calculations.

I guess if you don't have a grid covering the entire area you want your EV's to travel in, you need something. And what is the grid in many places if not a fossil fuel powered generator? (yes, I know, wind turbines and nuclear and solar panels and what have you).

But you probably knew all that already, didn't you?

 

* in fuel use

 

Edited By Nigel R on 14/08/2019 14:13:58

Thread: Single servo ailerons
14/08/2019 14:03:30

"After further bench checks I found that my Flash 8 TX triple rate switch was in the mid position and the exponential was set at zero instead of -35%. This had given me 5/16th deflection instead of the 1/4" recommended. Balance point within parameters"

Hmm. Well, report back after you've flown again.

It is worth nothing that thousands and thousands of Wots have been flown with no expo, no rates and a single central aileron servo.

My opinion - dual servos aren't the panacea they are sometimes made out to be, especially on a traditional style sport model, and differential - should it be needed - is quite easy to achieve with an offset servo horn, or on the torque rods themselves.

Thread: Electric Cars.
12/08/2019 17:28:42

or paddles laugh

12/08/2019 15:23:38

"Gross overpopulation is the elephant in the room unfortunately."

It will take many, many generations before attitudes change worldwide to accommodate a sensible discussion on population levels.

however, it's not all doom and gloom -

simply keeping this next bit to facts as presented by wiki:

western & european birth rates have levelled off

asian areas are levelling off

african growth remains high and is estimated to do so for the next hundred years

median population growth predictions are to around 10 billion.

note european populations have been quite stable for a while; when other areas adapt to increasing longevity with falling birth rate the population there will also stabilise.

I would (personal opinion) note that this level of population doesn't seem to allow much of the natural world to remain very natural, which is beyond unfortunate, and it will need a remarkable shift away from fossil fuel to maintain living standard. Sadly humanity seems incapable of self limiting to a lower level which would allow a better coexistence with the other billion or so species that were here first.

 

Edited By Nigel R on 12/08/2019 15:28:56

Thread: Design & Build Sport Twin
12/08/2019 15:11:08

Seems ages since I last updated. I've been doing some small jobs finishing off a lot of the woodwork. Shaping the wingtips, tapering controls, attaching the tail feathers, making tank hatches, fitting in the control run outers, control horns, wing mount stuff sorted, all the kind of bitty jobs that tend to accumulate at the end.

There is little woodwork left - main jobs are to get the fuselage nosecone mounting blocks done, glue on the nacelles and sheet the fuselage underside - before getting to covering and fitting out.

20190810_223110.jpg

Thread: Extra Hot Chilli
12/08/2019 14:31:39

I agree.

If you don't have a feature, you can't use it wrong!

Thread: The Aerodynamics of the Spitfire
12/08/2019 13:52:08

Yes the Mustang and Spit were certainly the cream of the crop and very very close indeed; a few tweaks to the Spitfire cooling could have had that top speed on a par. Like you say by then, not needed, and I guess the development interest had (or was just about to be) switched to jets anyway.

Thread: Extra Hot Chilli
12/08/2019 11:38:42

Are you intending on doing anything fancy with the throttles, any special mixes or so forth to keep one engine at idle while you can start/run/throttle the other, or a differential mixing for taxying?

Thread: The Aerodynamics of the Spitfire
12/08/2019 11:32:23

Nice post Colin.

I guess any successful project needs a champion (Mitchell) and a talented team behind them (led by Smith).

"The superior level speed of the P51B, C and D with similar Merlin engine to the Spitfire VII, VIII and IX was found by the North American development team to be due to the very low drag of the cooling system"

The P51 cooling setup used "waste" heat to provide a small amount of thrust. Working very much like a ramjet, with the fuel burning stage replaced by the radiator. It was a very clever piece of engineering.

**LINK**

The Spitfire system had been intended to use the same principle but did not achieve that goal. There is a transcript of a presentation by Atwood on the Mustang system here:

**LINK**

Seems the Mosquito got it about right though!

"It seems that most other contemporary airplanes attempting to take advantage of the Meredith Effect failed for one reason or another to combine an efficient duct system with a properly designed and regulated exit-closing mechanism and did not develop the energy recovery inherent in the Meredith method. They generally used 10 percent or more of their power available at high speed to overcome cooling drag. A notable exception was the DeHavilland Mosquito multi-purpose plane with the same Rolls-Royce engines and which used a wing leading edge radiator mounting with a short and direct inlet duct"

Thread: Extra Hot Chilli
12/08/2019 10:31:43

Looking good, some quick progress there.

Flaps are to be standard 'plain' flaps?

Have you any idea what the all up weight is likely to be?

Thread: Hospitalised, my own fault - but ?
09/08/2019 11:59:20

"sharp the trailing edge of a current APC i/c prop' can be as compared with the old nylon and g/f"

I still use a number of the Graupner Super props, though they're getting quite hard to find now.

Probably less efficient than APC, but also significantly less efficient at cutting things.

Thread: Drone harassment
09/08/2019 11:54:44

Seems to be some excellent supporting evidence there for the forthcoming money collection scheme...

...not! devil

Thread: Methanol versus Petrol?
09/08/2019 11:50:42

The glow market was saturated.

Create a new market (electric, petrol) = keep selling stuff.

Thread: Solartex, any tips?
09/08/2019 11:43:59

"Having already gone over it to presumably shrink it, why would you then go over it AGAIN to stick it all down? "

Tex is pretty good at adding strength, so once you have it taut, stick it permanently to the underlying structure.

Thread: Hospitalised, my own fault - but ?
08/08/2019 14:23:18

What about a hook and bungee?

Doesn't need to be much of a bungee if the thing has that much power.

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