Author Topic: Flights of Fancy  (Read 50800 times)

Re: Flights of Fancy
« Reply #425 on: 12 April, 2022, 12:13:51 pm »
You may be interested to know (if you didn't already) that a lot of rubber powered duration models (e.g. Wakefield & similar classes) use single blade props.
As do some of the F2A models (control line speed, models can go over 180mph, propellor blade tips a lot more).

Re: Flights of Fancy
« Reply #426 on: 12 April, 2022, 12:33:14 pm »
It gets worse, the latest C-130T (the J is now 25 years old), which is an upgraded H-model, has 8-bladed props. They're multiplying!
Wind turbines are an interesting comparison, they have different constraints from aircraft and are almost all three blades. With three blades turbines get close to the theoretical efficiency limit (the Betz limit), but they could get closer with four blades and a lower efficiency per blade. Using four blades would improve an individual wind turbine, but in a wind farm a better use of the extra blades is to add more three bladed turbines. There are a few two bladed wind turbines, which would be an even better use of blades in a wind farm, but they are not common. I think the reason is that mechanical control of the rotation about the vertical axis is more difficult with two blades, because the moment of inertia changes so much between blades vertical and horizontal.

TheLurker

  • Goes well with magnolia.
Re: Flights of Fancy
« Reply #427 on: 16 April, 2022, 09:11:57 pm »
What's the difference between this iteration ...


... and this iteration?



Clue.  The first iteration *didn't* do this ...  https://vimeo.com/ 700046074 (yes, yes I know - bolt em together)  which is why the second go has brand new wings, with *matching* dihedral top & bottom and the longitudinal dihedral (decalage) is about half what it was.  The 1st attempt "flew" like a drunken turkey.

Andy's launching it on my behalf for many complicated reasons, but mainly because my hand launches are a bit hit & miss.

For those that need to know these things.  Flying weight is 24.6g inc. motor (16" loop of 1/8") at 2.8g and the flight filmed was at 600 turns, which is about 50% max for the motor fitted. 
Τα πιο όμορφα ταξίδια γίνονται με τις δικές μας δυνάμεις - Φίλοι του Ποδήλατου

TheLurker

  • Goes well with magnolia.
Re: Flights of Fancy
« Reply #428 on: 29 April, 2022, 07:56:06 pm »
Indoor Scale Nats. last weekend.  Second day was FF.  Some newsreel (not mine) from the FF day.

A summary showing both how well models can fly as well as how tricky it can be to get them to fly well.   Pedaldog, keep an eye out for the Consolidated Coronado    https://youtu.be/L2ior65DF54

A couple of the winners :

Jon Markovitz' electric Bristol Scout  https://youtu.be/NedV_PXS6cE
Richard Crossley's Aeronca Chief - https://youtu.be/MZgSJxzO7eo

Τα πιο όμορφα ταξίδια γίνονται με τις δικές μας δυνάμεις - Φίλοι του Ποδήλατου

andytheflyer

  • Andytheex-flyer.....
Re: Flights of Fancy
« Reply #429 on: 01 May, 2022, 08:26:15 am »
What's the difference between this iteration ...


... and this iteration?


Work of art Lurk, work of art.  Very nicely done.

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Flights of Fancy
« Reply #430 on: 01 May, 2022, 10:52:42 am »
Indoor Scale Nats. last weekend.  Second day was FF.  Some newsreel (not mine) from the FF day.

A summary showing both how well models can fly as well as how tricky it can be to get them to fly well.   Pedaldog, keep an eye out for the Consolidated Coronado    https://youtu.be/L2ior65DF54

A couple of the winners :

Jon Markovitz' electric Bristol Scout  https://youtu.be/NedV_PXS6cE
Richard Crossley's Aeronca Chief - https://youtu.be/MZgSJxzO7eo



Amazing stuff!

How is the flying part judged? And how does the “pilot” get it to land? Does the engine cut out after, say, 20 seconds?

TheLurker

  • Goes well with magnolia.
Re: Flights of Fancy
« Reply #431 on: 01 May, 2022, 11:42:06 am »
Quote from: AndyTheFlyer
Work of...
*Blushes*  If you think that's OK, you should see some of the stuff that the experts knock together.  Stunningly good work.

Quote from: PaulF
Amazing stuff!
Isn't it though?  Way out of my league.

Quote
How is the flying part judged? And how does the “pilot” get it to land? Does the engine cut out after, say, 20 seconds?
For the scale stuff flight is judged on meeting some minimum qualifying time plus extra for time above the minimum.  Often there are bonus seconds for ROG (rise off ground i.e. a take-off) to compensate for the reduction in endurance that goes with ROG and an aesthetic judgement of "realistic" flight characteristics.  I don't know how the realism bit is judged, one of life's mysteries on a par with the scoring for ice-dancing & rhythmic gymnastics to me.

All sorts of incredibly clever and astonishingly light electronic wizardry is available to those who use electric motors.  Speed controllers that can be programmed to give a particular engine rev profile over a given timeframe.  So a burst for take-off, drop to cruising revs at desired time/height and then wind the revs down to bring it into land.  See Jon's Bristol Scout.

It's a bit simpler with rubber & CO2.  Gravity wins after the motor no longer has enough torque (rubber) or gas (CO2) to keep the model at the Vmin required to hold level flight and after that you're into little more than a power assisted glide.  See Richard C's Aeronca Chief.
Τα πιο όμορφα ταξίδια γίνονται με τις δικές μας δυνάμεις - Φίλοι του Ποδήλατου

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Flights of Fancy
« Reply #432 on: 01 May, 2022, 12:32:37 pm »
Thanks!