New Products Flash Sale
Thread Tools
Old May 06, 2015, 04:00 AM
lFritZl is offline
Find More Posts by lFritZl
Heads up, Eyes open....
lFritZl's Avatar
South Africa, GP, Johannesburg
Joined Feb 2013
15 Posts
Question
Thermal capable or not?

first of all, I am of mostly a helicopter background, so I'm a relative noob as far as gliding and gliders go.

So, my question is: will this creation (abomination) of mine be able to fly thermals (and if so how well) or am i wasting my time even flying with the motor off?

The wing was originally from the "ikarus dlg" that "thistle2311" designed. The ikarus worked for a while until failing catastrophically on launch (my throws were terrible). But i repaired and saved the wing. I now recently built a powered fuselage for it.

The span is 1.2m (47 in.); auw is 460g (16oz); wing area is 15.66 sq.dm (258.5 sq.in); wing loading is 29 g/sq.dm (8.913 oz/sq.ft) and according to thistle2311's thread the wing uses AG airfoils. The power system is off an old foamie and allows it to climb straight up at 1/3 throttle. And it flies on rudder/elevator/throttle. The CoG has been set using dive tests so that it stays pretty much neutral through the dive.

I have been flying and enjoying it a lot, and as far as i can tell it glides alright. But its always coming down. I have gotten better, my over-controlling heli tendencies have somewhat given way to trimming it and just letting it fly lazy curves across the sky.

I do realize (from reading a ton on gliding/soaring/thermal flying ect.) that it does take practice and time, but am i dealing with a duck here? Or is it worth it to stick with it?

Any input/advice is always appreciated.

Fritz
lFritZl is offline Find More Posts by lFritZl
Reply With Quote
Sign up now
to remove ads between posts
Old May 06, 2015, 06:08 AM
Petem is offline
Find More Posts by Petem
If it flies - I want one!
Petem's Avatar
Werribee, Victoria, Australia
Joined Jul 2008
1,167 Posts
Looks good

Fritz,
The basic layout looks fine; the wing loading is a tad high for a small soarer, but that will not stop it going up once you contact a thermal.
Go flying, have fun, and start plotting your next move into soaring!
It can take quite a while before you start to recognise the rising air; after that it is just a matter of slowing down and circling in the good stuff, and pushing quickly through the sink.
Cheers,
Pete
Petem is offline Find More Posts by Petem
Reply With Quote
Old May 06, 2015, 07:42 AM
2400RDR is offline
Find More Posts by 2400RDR
Out of helis, sanity returning
Tallahassee, FL
Joined Feb 2009
2,375 Posts
Whatever you can do to make it lighter and less draggy would help. From looking at the prop and reading your description of the climb, I would guess that the motor is rather large, and you might be using a large, heavy battery.

So- a smaller motor, smaller battery and folding prop would definitely improve matters.

Now that I've made my guess, what size motor and battery are you using?
2400RDR is offline Find More Posts by 2400RDR
Reply With Quote
Old May 06, 2015, 07:56 AM
JimNM is offline
Find More Posts by JimNM
WAA-08 THANK FRANK!
JimNM's Avatar
Las Cruces, New Mexico, United States
Joined Jun 2002
7,527 Posts
Most things will thermal - shopping bags, small dogs, shopping carts, lawn chairs, heck even red neck trailer houses will thermal (in a tornado...)

2400RDR is right on about the need for a folding prop. Your prop is acting as a speed brake - even more so if it is not stopped . A windmilling prop will cut your glide by 50% or more. Get the brake set on the esc and get a folder prop.

Generally, a glider does better with a large, slow turning propeller. Kv around 950-1000 for 3s battery, 1200-1400 for 2s battery. The size limits of your design may make it difficult to find a low enough Kv motor to be optimal. Pitch is generally 1/2, or less, of diameter. 6x3 or 8x4.

Good luck - soaring is addictive.
JimNM is offline Find More Posts by JimNM
Reply With Quote
Old May 06, 2015, 12:05 PM
peterlngh is offline
Find More Posts by peterlngh
Registered User
Joined Apr 2012
3,029 Posts
I concur. It will soar if you replace the prop with a folder and probably won't with a windmilling prop. I have a heavy DG 1000, about 15.5 oz. wing loading, and it will soar beautifully in strong lift despite the fact that it has to be going about 30mph to avoid dropping into a spin. I use just enough throttle to kick the blades out to use as a air brake when I'm diving it in for landing at the short end of my strip.

Cheers!
peterlngh is offline Find More Posts by peterlngh
Reply With Quote
Old May 06, 2015, 01:53 PM
nateyok is offline
Find More Posts by nateyok
Registered User
United States, CA, Long Beach
Joined Oct 2014
58 Posts
If you could lose about 4-6 oz somewhere that would be good. How is the responsiveness of the rudder, just looks small in the picture. And why is the fuse so big, making it smaller would cut major drag. I think it looks nicely done though for an abomination
nateyok is offline Find More Posts by nateyok
Reply With Quote
Old May 06, 2015, 02:58 PM
Bmwjoon is offline
Find More Posts by Bmwjoon
Registered User
Joined Mar 2015
65 Posts
What motor battery in there? Try a little bell motor on 2S with a folding prop. If you lost some weight it will help Alot.

Great luck !
Bmwjoon is offline Find More Posts by Bmwjoon
Reply With Quote
Old May 07, 2015, 05:57 AM
lFritZl is offline
Find More Posts by lFritZl
Heads up, Eyes open....
lFritZl's Avatar
South Africa, GP, Johannesburg
Joined Feb 2013
15 Posts
Thanks everyone. Some food for thought.

Quote:
... So- a smaller motor, smaller battery and folding prop would definitely improve matters.

Now that I've made my guess, what size motor and battery are you using?
At the moment it has a 2826 2200kv, 6x4 (cut down 7x4 that had a chipped tip) and 800 3s. It is clearly to big,... but it was what i had "lying around", so i chucked it in there. As far as i know the rpm is to high for a small folding 6x4 / 7x4, it will likely throw a blade and explode the front of the plane.

I can maybe free up a 2822 1400kv on 2s 800 and get a 8x6 folding. That rpm setup should be fine for folding? But I would unfortunately only save at most 15g (0.5oz) on the motor and 27g (0.95oz) on the battery. I not sure the folding prop vs "fixed prop and spinner weight", but I'm assuming that folding would be lighter, so there would be a bit of weight loss there to.

Quote:
...A windmilling prop will cut your glide by 50% or more. Get the brake set on the esc and get a folder prop.
Quote:
I concur. It will soar if you replace the prop with a folder and probably won't with a windmilling prop.
I already have the brake set, prop is stopped except for the high speed gliding/diving flybys.... which do sound awesome.

Quote:
How is the responsiveness of the rudder, just looks small in the picture. And why is the fuse so big, making it smaller would cut major drag.
The rudder works pretty good, it will almost roll (well at least a huge descending barrel roll) if the stick is jammed to the side on high rates. I actually 3d printed the fuse formers, then planked/sheeted the fuse. It is that size due to the parts i had at hand, primarily the spinner. So if it comes down to it I could readily make a smaller sleeker fuse. Truth is I really didn't expect to have this much fun with this. I had the old wing, and spare components. I though maybe at best i could just have a good flying plank to "muck-about" with..... It's well past that stage .

,Fritz
lFritZl is offline Find More Posts by lFritZl
Reply With Quote
Old May 07, 2015, 06:11 AM
Bmwjoon is offline
Find More Posts by Bmwjoon
Registered User
Joined Mar 2015
65 Posts
Try emax cf2822 on 2s nano 2s950 and a 11x7 or 12x6.5 folder. 20 something grams on a 400g model is significant.
Bmwjoon is offline Find More Posts by Bmwjoon
Reply With Quote
Old May 07, 2015, 06:24 AM
JimNM is offline
Find More Posts by JimNM
WAA-08 THANK FRANK!
JimNM's Avatar
Las Cruces, New Mexico, United States
Joined Jun 2002
7,527 Posts
For high speed motors, you need an 8mm root for the folding props. The smaller 6mm roots are for gearbox application and have a max rpm around 7000.

Again, component size is your limiting factor with the little glider. You will reach the event horizon of diminishing returns if you have not already. Can you get a 22mm or and 18mm motor? Then you will have even higher Kv...

With the right esc and rx, you could drop to 1s lipo....then there is the diminishing returns issue again.
JimNM is offline Find More Posts by JimNM
Reply With Quote
Old May 07, 2015, 07:32 AM
JimNM is offline
Find More Posts by JimNM
WAA-08 THANK FRANK!
JimNM's Avatar
Las Cruces, New Mexico, United States
Joined Jun 2002
7,527 Posts
- Oh yeah, another thing I forgot to mention... good job on the proof of concept, so far. Most people would not tackle the project. Not only did you step out of your comfort zone - you met and exceeded your goals.

Nice work!
JimNM is offline Find More Posts by JimNM
Reply With Quote
Old May 27, 2015, 03:58 AM
lFritZl is offline
Find More Posts by lFritZl
Heads up, Eyes open....
lFritZl's Avatar
South Africa, GP, Johannesburg
Joined Feb 2013
15 Posts
Right, so i have the 1400kv motor in, but i am still running 3s (I like the backup power to pull it out of bad situations .....and its still plenty fast enough to turn heads ). But its 28g lighter (saved a bit on the esc as well). A couple of folding props also on the way. One that will work on 2s option and one for 3s.

I was away recently in dullstroom (high altitude, wide open spaces, known for trout fishing and with plenty of birds of prey). So thought it would be a great place to have a proper go with this plane. Ended up having some of the most enjoyable flying i have ever had. Got to fly 3 separate times with birds of prey. Got to experience at least some thermal activity. Although i think they weren't all that strong, Its turning early winter here and non of the birds did more than about 4 revolutions before gliding off to another tree, or disappearing downwind. I had at least 2 turns in a "proper" (all be it weak) thermal, where the plane noticeably gained height. Unfortunately i couldn't stay with it. In one case i was meandering around the field about tree height and slightly upwind and an eagle/hawk/buzzard (I'm no bird expert, but it was brown) took off out of a nearby tree and caught lift right where the plane was. He must of noticed the plane was in lift when i had not. It was truly amazing how much he gained from just a few turns in it before gliding of.

.... and thanks JimNM it really has exceeded my goals, In fact its opened up a whole new section of rc flying that I'm really enjoying. I'm already thinking a thinner sleeker fuselage is in order, to try and get even more out of it. Once the props arrive ill maybe get stuck in.

,Fritz
lFritZl is offline Find More Posts by lFritZl
Reply With Quote
Old May 27, 2015, 11:48 AM
peterlngh is offline
Find More Posts by peterlngh
Registered User
Joined Apr 2012
3,029 Posts
It sounds like you're hooked, Fritz. Welcome to the club and keep following those birds around. They might make you feel inadequate but they won't steer you wrong.

Cheers!
peterlngh is offline Find More Posts by peterlngh
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product Quadcopter with thermal imaging capability yvesOttawa Multirotor Talk 0 Apr 18, 2015 10:04 PM
Discussion Floaty and thermaling capability vigli Hand Launch 2 Apr 06, 2014 01:08 AM
Found WTB-FMA Balance Pro HD w/A123 capability or not steve1814 Aircraft - Electric - Batteries & Chargers (FS/W) 1 Mar 09, 2008 02:51 PM
Mini Graphite - To thermal or not to thermal conradc Sailplane Talk 1 Oct 26, 2005 10:47 AM
Mini Graphite -To thermal or not to thermal conradc High Performance 14 Sep 04, 2005 10:30 PM