Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
July 09, 2020, 08:07:34 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 ... 18 19 20 21 22 23 24 [25]   Go Down
Print
Author Topic: First issue of new Aero Modeller has arrived  (Read 37143 times)
0 Members and 1 Guest are viewing this topic.
TheLurker
Platinum Member
******

Kudos: 28
Offline Offline

United Kingdom United Kingdom

Posts: 1,132




Ignore
« Reply #600 on: June 27, 2020, 03:15:32 AM »

Quote from: OZPAF
As it is a dynamic control via moving ailerons your point re lack of control at low speeds
Time for me to reveal how spectacularly dim I am about matters aerodynamical, but surely that's a problem that affects any control surface at any scale regardless of actuation method?  The simplest, nautical, example I can think of is loss of rudder control when a boat slows below steerage way. Even something as "simple" as a gurney strip relies on airflow to achieve its effect.  Or have I got the wrong end of the stick entirely?
Logged
Prosper
Platinum Member
******

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 1,540



Ignore
« Reply #601 on: June 27, 2020, 03:39:31 AM »

Thanks for all the searching fellas - Urs, I hope you had a good meal!

My concern is that if I read the article but didn't ever visit HPA forums, I could think either, 'Oh I see. They've deliberately printed the link wrong - it's a game, and I'm supposed to hunt the video down - what fun!'  . . .or alternatively, 'Oh, doesn't work. Typical. Another snake-oil salesman I expect. Now, where did I put my keys?'

Of course I hope people don't think the latter.


That's the right end of the stick I think TheLurker. I guess John is pointing out that there's the possibility of designing wing and aileron to provide better control at  low airspeed. There are so many variables - deflection. . .pendulum weight. . .pendulum throw etc. that it's difficult to know where to begin.

Stephen.
Logged
DHnut
Gold Member
*****

Kudos: 18
Offline Offline

New Zealand New Zealand

Posts: 784



Ignore
« Reply #602 on: June 27, 2020, 04:19:05 AM »

Stephen,
             That is an impressive exercise and the key is clearly to sensitive pendulum set up but like everything it has limitations. You have a good speed range and providing a spiral does not develop it will control the roll, and normally the model should not be stalling so there is a good flying envelope. I suspect the wandering relates to which wing is stalling first and dropping in that direction. The weight of 1 gm is also very good. I look forward to seeing it in Aeromodeller.
Ricky
Logged
Prosper
Platinum Member
******

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 1,540



Ignore
« Reply #603 on: June 29, 2020, 08:32:36 AM »

Quote from: DHnut
I suspect the wandering relates to which wing is stalling first and dropping in that direction.
That's probably it, Ricky. I can't remember why so many of those flights (which date from mid-Feb to early March) were stally. I know that demonstrating the model's stall recovery was on the list of features I wanted to video, so perhaps I didn't re-trim the pitch for some while, as I concentrated on trying to record other characteristics of the system.

Stephen.
Logged
billdennis747
Palladium Member
********

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 4,104



Ignore
« Reply #604 on: June 30, 2020, 06:18:41 AM »

I have been thinking a lot about Stephen's article and in particular the video. I have concluded that I have no idea about what goes on in flight and will just marvel at how that model flies.
Over the years, I have corresponded with Fernando Ramos in the US who has long used pendulum ailerons (sometimes unnecessarily in my opinion) and he convinced me that vertical pendulums don't work, because of the way they swing the wrong way if the model accelerates into a turn. He proved this by taking a mock-up for a ride in his plane to see what happens. He uses a pendulum at a shallow angle (20 degrees below horizontal) and much less movement. I used this in my SPAD which flew well. Yes, a tiny amount of dihedral crept in in flight but without the pendulum, it would come in. It also held a right turn, which power models mostly don't. The system gives a 'bang-bang' response, not progressive. You can just see the amount of movement.
My only other successful pendulum was the rudder on the BA Swallow. Another one that was hopeless without it. On launch, the model banks slightly left, the rudder heels right at 30 degrees, and away it goes, even in strong wind. I never understood that.
Can't wait for the next instalment.
Attached files Thumbnail(s):
Re: First issue of new Aero Modeller has arrived
Re: First issue of new Aero Modeller has arrived
Logged
TheLurker
Platinum Member
******

Kudos: 28
Offline Offline

United Kingdom United Kingdom

Posts: 1,132




Ignore
« Reply #605 on: June 30, 2020, 09:19:18 AM »

Bill, do you do requests for your Scale Matters column?   If you do, any chance of a bit more about Derek Knight's Gladiator?

Lurk
Logged
Russ Lister
Free Flight Modeller .... sub 250g!
Palladium Member
********

Kudos: 73
Offline Offline

United Kingdom United Kingdom

Posts: 4,398


Russ Lister



Ignore
« Reply #606 on: June 30, 2020, 11:34:23 AM »

Bill, do you do requests for your Scale Matters column?   If you do, any chance of a bit more about Derek Knight's Gladiator?

Lurk

Wouldn't say no to that myself.
Logged
billdennis747
Palladium Member
********

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 4,104



Ignore
« Reply #607 on: June 30, 2020, 12:38:19 PM »

Bill, do you do requests for your Scale Matters column?   If you do, any chance of a bit more about Derek Knight's Gladiator?

Lurk

Wouldn't say no to that myself.
I'm sure Derek won't mind me posting his photos here. The model is 21.5", electric, and gorgeous
Attached files Thumbnail(s):
Re: First issue of new Aero Modeller has arrived
Re: First issue of new Aero Modeller has arrived
Re: First issue of new Aero Modeller has arrived
Logged
TheLurker
Platinum Member
******

Kudos: 28
Offline Offline

United Kingdom United Kingdom

Posts: 1,132




Ignore
« Reply #608 on: June 30, 2020, 01:26:38 PM »

Thanks Bill.

That is a stunning piece of work.  From the pic. in AM I thought it was a much bigger model than that. 

Logged
billdennis747
Palladium Member
********

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 4,104



Ignore
« Reply #609 on: June 30, 2020, 01:53:16 PM »

Thanks Bill.

That is a stunning piece of work.  From the pic. in AM I thought it was a much bigger model than that. 
Yes, it's the detail at that size that is astonishing.
Logged
Squirrelnet
Platinum Member
******

Kudos: 43
Offline Offline

United Kingdom United Kingdom

Posts: 1,081




Ignore
« Reply #610 on: June 30, 2020, 01:54:25 PM »

Great shots Bill

+1 for some more detail on Derek's build in AM

Here's another pic taken last summer at the OMFC 50th, it looked impressive then, without the engine fitted. Last time I saw it was at Bushfields before the lock down where Derek was doing some taxi tests. I hope he's has found some suitable KK grass to trim it out, it's a hugely impressive model
Attached files Thumbnail(s):
Re: First issue of new Aero Modeller has arrived
Logged
OZPAF
Palladium Member
********

Kudos: 186
Offline Offline

Australia Australia

Posts: 5,654



Ignore
« Reply #611 on: July 01, 2020, 05:01:48 AM »

Quote
As it is a dynamic control via moving ailerons your point re lack of control at low speeds
Time for me to reveal how spectacularly dim I am about matters aerodynamical, but surely that's a problem that affects any control surface at any scale regardless of actuation method?  The simplest, nautical, example I can think of is loss of rudder control when a boat slows below steerage way. Even something as "simple" as a gurney strip relies on airflow to achieve its effect.  Or have I got the wrong end of the stick entirely?

Yes that's true Lurk - what I had in mind but didn't actually say(age is my excuse Smiley) is that it is a dynamic control as compared to say a thrust line adjustment which is basically static - ir retains a constant value, over a range of airspeed. Dynamic implying that the effect of any surface will vary with speed.

Quote
That's the right end of the stick I think TheLurker. I guess John is pointing out that there's the possibility of designing wing and aileron to provide better control at  low airspeed. There are so many variables - deflection. . .pendulum weight. . .pendulum throw etc. that it's difficult to know where to begin.

That is another part of the scenario - wing planform and span lift distribution would seem to have a lot to do with aileron effectiveness. Check out the differences between say a top RC F5J glider of high AR and narrow tips and say a light slow moving RC Indoor pattern model.

I'm impressed with how well Stephen's aileron's work at his model's low Re no's.

The gearing would also be a major factor - perhaps the most important actually - so that there is sufficient correction applied before the gust induced roll is allowed to develop. Perhaps though there may still be gains to be had from optimising the aileron plan form - less drag for the same restoring force.

John
Logged
OZPAF
Palladium Member
********

Kudos: 186
Offline Offline

Australia Australia

Posts: 5,654



Ignore
« Reply #612 on: July 01, 2020, 05:07:30 AM »

Derek's Gladiator is very impressive Bill. Obviously he has trained ants to do the detail work Smiley So many tasks in the build requiring excellent workmanship, with so many chances to slip up!

John
Logged
Prosper
Platinum Member
******

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 1,540



Ignore
« Reply #613 on: July 02, 2020, 05:55:46 AM »

Thanks for the clarification John. I don't intend to go far with optimising (or trying to anyway) the external factors, because I'm almost exclusively a scale modeller so don't have the freedom of choice where wing shape or aileron shape are concerned.

Bill, thanks for the comments. I recall the Fernado Ramos arguments from a previous HPA discussion a few yrs back. I think Tom Arnold made a more detailed telling of his aerial experiment, but I'd like to know more. . .was the test pendulum exactly at the CG, was there turbulence. . .something must have been up, because it seems he didn't 'prove' anything at all. Sorry if Mr. Ramos is a saintly figure in modelling or his findings have become sacred over time and all that, but there it is.

And yes I can't provide a scientifically rigorous explanation of what's going on, but try this, it works for me:

People talk of a pendulum swinging one way or the other to effect a correction - but ditch that and think of the pendulum not moving. Imagine it's hanging straight down towards New Zealand (if the model is flying straight) or is inclined by a small angle dictated by the model's curved path, if the model is in a balanced turn. Inclined, but unmoving, that is. Now imagine that there is no slop or play whatever in the links between the pendulum and the ailerons. None at all (this isn't quite true in reality, but it's very close to being true). Now imagine an almost complete absence of friction in the same links. So when the model is caused to roll around the unmoving pendulum, by a gust, the ailerons are deflecting even as the roll starts. Any lag is down to friction, and we're satisfied that that's really small. So the counter-roll aileron is being fed in even as the roll gets going.

Stephen. PS amazing Gladiator - one for the annals. I thought it was much bigger too. Great artistry.
Logged
billdennis747
Palladium Member
********

Kudos: 62
Offline Offline

United Kingdom United Kingdom

Posts: 4,104



Ignore
« Reply #614 on: July 02, 2020, 07:40:33 AM »

I recall the Fernado Ramos arguments from a previous HPA discussion a few yrs back. I think Tom Arnold made a more detailed telling of his aerial experiment, but I'd like to know more. . .was the test pendulum exactly at the CG, was there turbulence. . .something must have been up, because it seems he didn't 'prove' anything at all. Sorry if Mr. Ramos is a saintly figure in modelling or his findings have become sacred over time and all that, but there it is.
No, he isn't 'a saintly figure in aeromodelling' but he has been building scale models since the 1960s, including many pendulum-equipped models which work for him, and others.
Logged
Pages: 1 ... 18 19 20 21 22 23 24 [25]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!