Slightly less Simple Soarer

by Hugh Cherkas | April 30, 2014 | (8) Posted in Projects

Slightly less Simple Soarer


Having built some of the simpler Flitetest designs to try and teach myself to fly, and with reasonable success, I decided to have a go a modifying one of the FT aircraft designs for a bit of an experiment and for fun.

I built the FT Simple Soarer around christmas time as my first plane because the level of damage that can be done is so minimal, and it sounded like a great beginner platform to fly with. I had a great amount of fun with it in the glider configuration and the motor configuration, but a few crashes too many on a gusty day killed it. I wanted to make the step up from a 3 channel to a 4 channel aircraft, so I went about building the FT Delta, and after having what seemed like endless failed launches on my own I wondered what I could be doing wrong. I then got my friend to throw the Delta whilst I controlled it, and I was shocked by how fast it seemed compared to the SS. The Delta flew great and it was good to experience the "bank and yank" flying technique. However the Delta didnt last long as my inexperienced thumbs caused it to plummet to the ground at great speed.

I decided to go slightly back to the drawing board in terms of which aircraft would last the longest, and at one staged  convinced myself that buying something like an AXN or a Bixler would be a smart move, but then what is the point when I can build something that I can fly for about £10 (excluding electronics obviously). I knew that I wanted a 4 channel plane that was reasonably docile and could introduce me to 4 channel flying well, so I decided that I would modify the plans for the FT Simple Soarer to become the "Slightly less simple Soarer".


I started with one clear idea in my head to try and improve this aircraft, which was to add ailerons (obviously) and to remove the dihedral, leaving only polyhedral. This was incredibly simple, as all I needed to do was draw some alternative lines on the plans and cut them. The lines which I changed where the innner-most section of the wing panels which were originally designed so that it would give a good amount of dihedral to the wing. Instead I made these completely straight to make the middle of the wing completely flat. This simple modification also eliminates the somewhat annoying problem of the wings rocking from left to right on the fuselage because of the dihedral, however it's not a hard obstacle to get over without removing the dihedral.

When thinking about the ailerons, I decided that I wanted to re-shape the wingtips a bit too. I took inspiration from the Robin DR300/400 which have a ployhedral wing, that gets slightly narrower towards the tip, with a very angular design. I cut the ailerons to what I thought would be an appropriate size to give good roll authority in the air. I was happy with the wing when I had finished, and was set to build the fuselage and tail pretty much as per the FT plans.







I also added flaps as a last minute choice just as a quick experiment. I had 2 servos left over from the Delta so there was no reason why not. I realise these are not completely needed, but it will be a good learning experience. They are not the biggest flaps in the world, but I'm sure they will have an effect in flight.


I cut out the fuselage exactly like the FT plans of the Simple Soarer, but I decided a bit more modification was required to the tail, because in all honesty I really did not like the tail design of the original plane. I instantly new that I wanted a T tail design, which mean bypassing the cut out for the horizontal stabilizer to sit in on the original plans. An issue that I wanted to resolve with my own designs was the long control wires that ran the vast majority of the length of the planes, which I personally found was annoying because they bent a lot inside the fuselage and sometimes got a bit snagged from the transition from inside to outside. The fix to this was simple, which was to put the elevator and rudder servos on the tail itself. In order to make this possible I had to make the vertical stabilizer twice as thick so the servos would be held in well enough. The dimensions of the vertical stabilizer are much smaller than the original plane as the rudder will not need to have as much of an input as they did on the 3 channel plane. I used the same dimensions for the horizontal stabilizer as the original, but made it straighter, purely because of looks, but it also gives a bit more surface area on the elevator. You can see how I mounted the servos on the tail and supported the elevator with an old coat hanger wire in these photos. I also decided to add a steerable tail wheel.


The main issue that I wanted to resolve with the original plane was the weak point on the fuselage just in front of the tail, which I found will easily shear clean off through the foamboard even in small crashes. Both my friend and I have had this problem so I didnt want it to happen again. My dad came up with a good idea to fill the entire of the rear fuselage with expanding foam which would stiffen up the whole area and hopefully prevent damage from small crashes. I'm yet to see if this still works, but I can say that there is a very noticeable difference in stiffness between the two even by just squeezing the foam. I soldered some extensions for the servo leads and ran them through the expanding foam up to the receiver. You can see the holes which I drilled to fill the fuselage with the expanding foam. I drilled more than one so that the foam could expand out through the other holes instead of out the front of the fuselage which would have been a pain to get rid of once it had set.

Power Pod

The foamboard power pod design is good, however they do suffer a lot of wear and tear which isn't ideal because I ended up rebuilding them several times. I read a good article about making power pods out of a material called correx plastic which wouldnt be as easily damaged. Unfortunately I cannot find the article to give credit to. I also saw another article which says to extend the power pod ( which seems like a good idea in order to give room to put the battery instead of having it on the bottom. I combined these 2 ideas to give this result.




I'm using an old plush esc for this plane. It's been a bit dodgey in the past bit it seems to be working okay, apart from the fact that there is no heatsink anoymore. I mounted it on the bottom of the power pod to get as much air past it as possible to cool it down. At some stage I will replace this esc.



I cut an angle on the front of the power pod to give it a downward thrust angle, which I didn't do with the previous plane and it is clear that this is an essential step to stop the plane from pitching up with throttle.

 I also decided to raise the wing above the fuselage about 5cm. There was not much of a reason behind this, but I wanted to experiment with how the plane would fly with the roll axis being above the fuselage. I expect that it will not have much of an effect but it is removable, and also provides a good place to mount a camera against if I choose to. 



The very last thing I have to do is to add the landing gear, to the power pod. I will use an old coat hangar wire again and sandwich it between a couple of bits of plywood, then velcro it to the power pod using elastic bands too. By doing this, the landing gear will come off in a very hard landing instead of causing damage to the power pod.

I'm looking forward to flying this plane for the first time, and I hope it will fly nicely. I know that this plane will not fly like that original Simple Soarer, and hopefully more like a simple trainer. Hopefully it will retain some of the gliding capabilities though. Please feel free to leave any comments, questions or useful tips I can use to make this better. As I said the main objective behind this was to experiment with the design and trying to improve it slightly, so I shall see how it performs in the near future.

I will post another article once I have test flown this and report of the positives and negatives.

Thank you for taking the time to read this article.


I never ended up posting a follow up article on this plane, so I thought I'd give a quick summary for the few that may end up on this article somehow.

In general it was incredibly easy to fly, in fact if it had have been any more docile I think it would have become a nightmare to control. The ailerons really could have done with being a bit larger for a higher roll rate, but there were no issues with what it already had, it just would have been nice to have had a bit more maneuverability. The all up weight was really quite heavy, so there was really no element of gliding available after all. The expanding foam in the fuselage really helped with durability, but I managed to knacker it in the end with some absolutely horrendous "flying". The only thing I did not expect at all was that it required a very strong throw to get it sufficiently airborne. This may have been down to the fact that I had a slightly under powered motor, but once in the air it flew and climbed just fine.

Just a quick update, partially just to assure that this was in fact successful, and would encourage people to modify plans as much as possible as there is a lot to be learnt from it


stay-fun on May 29, 2014
Nice design! Thanks for sharing! I'm working on a modified simple soarer with ailerons too (for an endurance plane). Right now I've left the dihedral in and removed the polyhedral, and just added ailerons (and thereby making the wing chord 5cm longer). It still has a lot of stabilizing power due to the dihedral.

I have a question. What is the benefit of the chord of the wing becoming narrower at the wing tips? My guess is that the tips would stall first, since the tips have the least lift, leading to a tip stall. And man, i HATE tip stalls...
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chodgson on May 29, 2014
Because of the under-cambered airfoil at the wing tips, tapering the trailing edge of the wing raises the trailing edge, which effectively reduces the angle of attack of the wing tips, making it less likely for them to stall. This effect is known as washout, and is specifically intended to prevent tip stall problems. It is normally achieved be twisting the wing slightly from root to tip, but with the way this wing is built, the tapered trailing edge should do it. Additionally, the fact that only the wing tips are undercambered is already helping to maintain tip lift.

Furthermore, I agree that it adds something to the style of the plane as well.:)
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stay-fun on May 30, 2014
Oh thanks for explaining that! That makes sense!
I did notice that i couldn't get my own simple soarer to tip stall, it does have the under camber wing tips, but no tapering. So... How come Hugh's plane does tip stall actually?
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Hugh Cherkas on May 30, 2014
yeah I was wondering about that. It only happened a few times but definitely seemed to drop a wing on some occasions. Perhaps I'm not fully recognizing what a tip stall is but my initial thought was that it was tip stalling when the wing drops.
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chodgson on May 30, 2014
Yah I guess there are a lot of variables to consider:
- the loss of lift due to the reduced area caused by the taper
- the increase in lift due to the effectively reduced AoA
- the loss of lift due to the effectively reduced camber caused by the taper
All-in-all, it seems reasonable to expect these to at least balance out to be equivalent in terms of tip-lift to the original design. But I'm not really an expert, I just happened to be reading an article somewhere specifically about this effect and thought I'd chime in. Sorry but I can't seem to find the article again, even with the power of google...
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Hugh Cherkas on May 29, 2014
Thanks for this useful info. I had only previously known about the twist in the wing to achieve washout. I'll have to try this on something a bit more exciting to fly next time!
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chodgson on May 30, 2014
Note that it only has this effect because of the design of the wing - if there was a flat bottom, it obviously wouldn't work - unless you twisted the bottom up as you built it. Do-able but probably not easily repeatable on each tip of the wing.
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Hugh Cherkas on May 29, 2014
I narrowed the tips mainly for experimental purposes, just to see how it would affect the flight. A couple of the tugs where I go to fly full scale gliders have this design and they are great looking planes in my opinion. As you say it does tend to tip stall a bit but it was quite docile and didn't cause me any major issues. If I built another one I probably wouldn't narrow the outer parts of the wing to such an extent and probably increase the size of the ailerons too, as the roll response seemed a bit sluggish.
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stay-fun on May 30, 2014
I have noticed on more gliders that there is poor aileron control. HK walrus and the techpod. In both gliders i had to set up 100% aileron to flap mixing to have decent control. I do have to admit that i like crazy rates, I'm used to that due to my helicopter background.
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Wimp on May 30, 2014
Great job! Have you thought about puting a turtle deck before and after the wing???
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Hugh Cherkas on May 30, 2014
I hadn't previously but now someones's mentioned it, it would definitely make it look more professional. Having said that, I've looked for posterboard in the UK, but I can't seem to find any, certainly not under that name. I usually end up using card or thick glossy paper from magazine covers and the like, but it works.
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davidio1000 on June 3, 2014
i'm also in the UK, I used thick card for my FT spitfire, it worked really well actually,but it tends to be a bit crinkle-prone, I was wondering where you got your foam board, I only found it at 'Pegasus art' for £5 per sheet plus shipping! which makes it almost as cheap to buy a hobbyking model.
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Hugh Cherkas on June 4, 2014
Hi David, I get my foamboard from Hobbycraft. They advertise is as 4 pounds per sheet but there has never been an occasion where it hasn't been on 3 for 2, so 8 pounds for 3 A1 sized sheets which I think is fairly good, although I always go to the shop to pick it up as I have 2 locally, so not sure about shipping
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1959cutter on May 28, 2014
I like this,as I have adapted the one sheet glider at 200% fuse for a glider(aspire) that had a very weak tail.
its much lighter than the original and stronger in the tail/fuse section.
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MyAKAndI on June 1, 2014
Can you give me the name of that one sheet glider? I want to try it out!
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1959cutter on June 6, 2014
mike springer on rc groups has the plans OSG or just google one sheet glider OSG plans.
its a lot like SS but at 200% the fuse is perfect...120" wings didn't work out so well
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Slightly less Simple Soarer