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Newbie to flat field / thermal.

Started by Big Phil, May 26, 2014, 09:59:41 am

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Big Phil

Morning all.

I'm about to take my first step into flat field and thermal soaring.
I've been flying the wonderfull slopes of South Wales for a couple of years now and have decided it's now time to try this type of flying so any advice would be greatfully excepted.

I've picked up an old, but mint Algerbra 100 elevator/rudder only model and bungee launch set.
With my slope models I tend to max out aileron and elevator throws but is this the norm' with 2 channel  thermal models?

I'm hoping to try some glide tests later at a local field to get the 'feel' of a 2 channel model.

As ealier mentioned any advice on this model, or flying in general would be most welcome.
Many thanks


No experience of the Algebra but for thermal soaring I don't use huge control throws. In fact the less you use the controls the better as all control movements create drag.
Basic Research is what I do - when I don't know what I'm doing!.


Have you flown rid/elev on the slope? If not try that first as you'll be more comfortable flying in a place you know. R/e models tend to be slower to react to turning inputs as they use the secondary effect of yaw (roll) to turn. This is also the case for levelling out again. This all means you have to be thinking ahead a lot more. I haven't done much flat field thermaling for a good while but it is very relaxing, and you get to practice landing a lot!!


May 26, 2014, 12:15:34 pm #3 Last Edit: May 26, 2014, 12:22:20 pm by Patmac
First, get a copy of George Stringwell's RC Thermal Soaring. There are a couple of copies on Ebay this one looks OK.
I have the earlier edition & still refer occasionaly to it after 30 years. 

Just did a search on Amazon & came up with these options, the one I have is the first on the page.
Pax vobiscum

Big Phil

Thanks guys,
I've just ordered a copy of the book from Amazon.
Unfortunately I was unable to glide test it today, maybe later in the week.
I'll let you know how it go's.


The Saint. (Owen)

You don't need to glide test the book Phil.  :''
Electrickery is the work of the devil.
Proper aeroplanes are powered by engines.

Big Phil


Hi Phil, have you tried out the Algebra yet ?

Re the control throws, IMO they do need as much throw as for slope flying but best with lots of exponential dialled in. You need to be able to quickly pick up a wing if hit by a gust when landing. Also if you get into a really strong thermal there can come a time when you need to persuade the model to come down. Without spoilers the safest way is to spin it down. This needs a powerful rudder to initiate the spin & powerful elevators to prevent it becoming a spiral dive which could over-stress the wings.

I don't fly any flat field pure gliders now (prefering electric self launch) but when I did I found it convenient to set up the trim of any new glider at a slope in a moderate to light breeze. 
The aim is to get the model to have as wide a speed range as possible. This is best achieved using the dive test to set the cg as far rearwards as you feel comfortable with. Once that's done the model will be sensitive to turbulence when flying slow, making thermal spotting easier & able to be speeded up to a fast flat glide with a little down trim in order to get out of sink quickly & penetrate upwind when necessary. A Tx with phases is a godsend for this.
The Algebra isn't as fast or as efficient as the modern mouldies but it isn't a floater either & can be made to move quite quickly. However on the slope it should stay up in lighter lift than the likes of the Alula. 

Once flying on the flat it's a case of getting to know the signs of thermal activity, sussing out the area you fly in, studying the model's behavior at all times, practicing thermal turns & spot landings.
For spot landing practice I found it best to use a marker such as a bright coloured hanky size bit of rag weigh or pinned down near where the bungee would land. I tried to land on it every time but no lawn darting. Also I timed each flight especially when there wasn't any thermal lift to be had in order to see if my skills were improving or not. I didn't bother keeping a detailed log, just a rough note on the day & relied on memory of last time out.

Sorry if I've gone on a bit too long but I hope you find it some help.

Pax vobiscum

Big Phil

Thank you Pat, most helpfull.
I have not flown yet, work/family commitments stopped me going out last weekend.
This weekend light (6 mph) winds forecasted and I'm wondering if this is ok to try it on my favourite slope.

I must be honest my biggest concern is a wing dropping on landing,  having never flown without ailerons.
I've even considered converting the wings to a 4 servo set up.

I will report back as soon as I maiden it.

Many thanks


May 29, 2014, 11:28:02 am #9 Last Edit: May 29, 2014, 11:56:43 am by Patmac
Light slope wind should be ideal for trimming the Algebra. Here's a video of my 100" Diamond chasing Alulas in a breeze that was just enough for them, most of the time the Diamond was flying higher than they could manage.

The Diamond with a fairly heavy glass fuse & foam obeche wings, weighs in at 5lb, I would think your Algebra is lighter than that with a similar wing area - around 800 sq ins.

If you keep the speed up on the final approach the rudder should be powerful enough to be able to keep the wings level then raise the nose slightly just before touchdown. The fast approach helps maintain control through any turbulence, IMO a cartwheel will do more damage than a fast landing.
BTW the Diamond is around 25 years old & started life to the old 100S comp standard - i.e. 100" span, 800 sq ins max & rudder/elevator only. I retro fitted ailerons & depite not reducing the dihedral the roll rate is reasonable - witness the roll near the end of the video.
Pax vobiscum


Don't worry about wing strikes. I learned to fly on the slope with rudder elevator and it was never an issue.  R/E was the predominant form of glider flying long before the zagi was invented.

Start by flying on days where it's sunny with light winds. If you fly in tough conditions you will probably get disheartened quite quickly, especially off low launch heights. Give your self a chance at first.

It's a thrill to get away in a thermal.  But not always easy.

Sent from my GT-I9505 using Tapatalk

Big Phil

Evening all.
I managed to maiden the Algerbra over the weekend.
Light winds were forecasted for Sunday so a few of us met up at one of our favorite slopes which has a huge flat area on top.

We carried out a glide test  which went perfect...straight and level, and oh such a long glide.
Wind was approx 6 mph so there was only one thing for it, chuck it off the slope edge   :-)
My mate did the honours of giving it the throw while I nervously held the tx.....it was a perfect launch, again straight out but this time climbing gently.
I carried out a few circuits while I gained enough height to carry out a dive test,  it instantly pulled out showing it was nose heavy but it wad flyable.
Turning with rudder only is strange...turns were not smooth at all, infact quite jerky. Maybe I was over steering then trying to correct ?
Each turn saw me losing a bit of height and then with elevator input saw the model bobbin g up and down.

Now for the part I dreaded,  the landing....after following advice from my more experience flyers I  went further back behind me and carry out a gradual turn while slowly loosing height.
First attempt saw the model flying past much to fast to land, 2nd attempt was perfect, it landed sweet.

Later I had my first bungee launches on the flat top of thr slope. These went well with no issues,  but were rather short flights.

One thing I found with this model is that it will drop a wing and stall if you try and turn  while travelling to slow.

Overall opinion, it flew and i did not break it, not sure if I like rudder only though...more practice maybe.



June 03, 2014, 12:45:53 pm #12 Last Edit: June 03, 2014, 12:52:57 pm by satinet
You can have too much rudder travel. I don't hold to the turn everything up to number 11 theory tbh.

R/E (rudder elevator) is not like flying ailerons - the response is generally slower and you have to fly differently (start turning before you get there). Although it does depend on the model. I had a gentle lady and it was relatively snappy on the rudder.  a club mate has a multiplex mini milan vtail (R/e only model) that can roll quite easily.  If a plane doesn't have enough dihedral and/or insufficient rudder it can turn quite poorly. I would tend to assume the algebra is a fairly sorted design though (?)

If you are banding the rudder stick full and waiting for a turn that will probably not work well.


How to thermal your RC glider, the good old downwind technique.
Instead of flying upwind where you almost fly blindfolded in terms of thermals (Unless there is circling birds or other indications that there is lift) it is much better to have a wind indicator that shows the point where the wind is blowing to. Wait for a small Wind direction change from the normal, and fly to that point.
3 meter Topmodel Diva/Thermic dream at almost 2,8 kg with 2x1800Mha 3 cell battery, and Spektrum DX8 with Vspeak,,,, and TM1000 + altimeter in the glider

Dynamic soaring will change your life..