Hand Launched Glider - A summer project

SteveOBHave · 15 Jun 2009 at 21:11

Being something of a lover of all things radio controlled and of things that fly I've always wanted a radio controlled airplane.

I have the small problem of living in a flat in the middle of London so I have neither the storage space nor the space to really fly a decent RC plane. I have also the minor issue of having to save for a wedding so I can't really spend any significant amounts of money on things that are considered by my better half as a toy. As we all know they are not toys but serious experiments in aerodynamics and a tool for learning.

A while ago I bought one of those foam faux RC planes that are shaped like an F22 Raptor and steers by changing the speed of a prop on either of the wings.

One of these:

Through a combination of crap skills and the aircraft being a pig to control I've given up on it and decided to try building my own. Looking around I came across these things, commonly know as HL Gliders (Hand Launched).

This particular one has radio gear in it and as such is a little beyond my means however it does interest me in as far as the design goes. It strikes me as both fairly customisable and also scalable. So the next trick was to hunt down some plans. It turns out that this is a pretty easy thing to find as there is something of a community out there for RC fliers and they seem perfectly happy to share them around.

I found a few on this site: http://f4bscale.worldonline.co.uk/hand.htm and decided to go with this plan:

It didn't seem too ambitious and being made out of mostly balsa I cautiously expect it to be fairly straight forward in construction. I'm going to take some liberties with the design, I will replace the main strut with a carbon fiber tube for some extra strength and am also considering cutting the guts out of the F22 Raptor thing and seeing what happens when you attach some motors to the wings.

Of course this is all extremely experimental and I have never done anything like this before so it might all end up with a poorly sculptured heap of crap that refuses to fly. I'll keep you all updated if you're interested.

arc@css · 15 Jun 2009 at 21:50

Nice. Brings back memories of my childhood. My brother used to construct gliders like that and some radio controlled ones. Vaguely remember him spending weekends working on it for many weeks before it was ready. Dad would then take us up to a well known spot / hill quite near to where we lived called Truly hill. You'd get all the kite and glider enthusiasts hanging around there flying their models around for ages.
Going off at a slight tangent I seem to recall that he bought one of those rubber band propelled gliders - the band on it was huge. I watched him as he launched it one day in our back garden and off it went, never saw it again. Just watched it disappear over the tops of nearby houses.

If you get any pics of your kit in flight then post a few. That would be great.

SteveOBHave · 15 Jun 2009 at 22:19

Haha thanks - It's not built yet so it won't be flying anytime too soon.

V4NT0M · 15 Jun 2009 at 22:22

arc@css · 15 Jun 2009 at 23:09

Nice vid. Sigh, memories.....

NightSt@lk3r · 15 Jun 2009 at 23:27

A mate and his dad built one of these, unfortunately i crashed it into his neighbours front door.

Malt_Vinegar · 16 Jun 2009 at 00:47

installing radio gear is a piece of pee now with the micro sized gear that is out there nowerdays. Servos seem to have dropped in size to about a quarter of what they once where without losing any power at all..
Electronics have moved on a long way too with Li-poly cells now rather than Ni-cad. Electronic models are really the mainstream now.
Was different in my day. The glow engine was king. The thing is, I am only talking about 10-15 years ago!

SteveOBHave · 16 Jun 2009 at 08:45

I got started on the project last night. I have a hardware store across the road so it was a relatively easy thing to find most of the essential bits.

Sandpaper
Sanding Block
Balsa
Gaffer Tape
Masking tape
Knives
Balsa Glue
Carbon Tube (off the bay)

The first thing I did was cut out the basic shape of the wing from the plan - the scale is based on the size of the wood really - I wanted to be able to fit the entire wing surface onto one piece of the balsa and then cut it when I had finished sculpting.

After cutting it to the desired size I have marked out the High Point of the wing as a guide for shaping.

My chosen method for the sculpting was sanding with 180grit sandpaper - turns out that it is a ridiculously laborious task and I gave up after around an hour of sanding in preference for using the full length of the large knife blade and shaving thin slices off. I wish I had thought of it earlier as it would've save a large amount of time and copious amounts of inhaled balsa dust.

However I'm getting there and it's slowly starting to take shape. I've marked a grid on the trailing edge to ensure that I'm getting a relatively flat finish without major variations on the surface. One irritating thing that I have noticed is that the wood is slightly warped and I chose the wrong side to start sculpting on for a wing unless I was going for a symmetrical profile. Still this is stuff that can be fixed later.

SteveOBHave · 16 Jun 2009 at 08:53

After a little bit of investigation - it seems that one of these is the way to go - A razor plane. So that is now on order.

"andy" · 16 Jun 2009 at 09:05

ill keep an eye on this project

and skyfall i literally came in the thread with a link ready to paste of that

damn you !

SteveOBHave · 16 Jun 2009 at 18:16

Well, another update.

After heading back to the hardware store and getting a MUCH rougher grit sandpaper I was able to make much more impact on the wing. The end result is looking not 'too' bad and considering it's my first wing not a bad effort so far.

Overall it took significantly less time than the initial work. I would say that any subsequent wings that I make will be far less time consuming.

Top of the wing

Profile

Leading Edge

Trailing Edge

Tomorrow I will be cutting the tailplane and finishing the wing.

Aero · 16 Jun 2009 at 18:21

Looks nice some effort gone in that already.

SteveOBHave · 16 Jun 2009 at 18:25

Cheers - it's deffo getting there - it's quite an interesting project with lots of learning but not too steep a curve.

SteveOBHave · 16 Jun 2009 at 18:37

Ultimately this is the kind of thing I'm going for:

Darg · 16 Jun 2009 at 19:19

Good luck mate. The gf got me a foam plane a year ago for my birthday. Within a few flights though it'd gotten quite damaged, it was a double engine pusher like your F22 so not the best.

I tried creating a biplane out of garden sticks (the thin green ones) and brown paper as the canvas and it actually got airborne but the thing was held together with sellotape so didn't last long either!

I'd like to get some helium filled balloons and make myself a blimp but helium canisters (even the small ones) are quite expensive anywhere I've checked. Waiting for McDs or somewhere to do some promotion with helium balloons

Thunderbolt · 16 Jun 2009 at 20:28

Had to do something similar at uni over a week, but I'm guessing I had to do quite a bit more maths

atpbx · 16 Jun 2009 at 20:33

My Dad and I made a radio controlled Gloster Gladiator out of Balsa wood way back when I was at primary school.
I helped cut the bits out and put the skin on, we never flew it, just built the model up and hung it up in the garage with some other models and his motorbike.

slylittlefox · 16 Jun 2009 at 22:10

The wing isn't symmetrical - doesn't it need to be?

/noob

KaHn · 17 Jun 2009 at 08:41

slylittlefox said:
The wing isn't symmetrical - doesn't it need to be?

/noob

Which Axis?

If you are looking down on the whole thing then yes it has to be symmetrical about the direction of flight, but for the side view it doesn't need to be symmetrical, normally their is a camber to help produce the required force at 0deg angle of attack (where as a symmetrical wing would only produce lift at angle of attack >0 with the use of an engine).

KaHn

SteveOBHave · 17 Jun 2009 at 09:19

slylittlefox said:
The wing isn't symmetrical - doesn't it need to be?

/noob

It's a perfectly legitimate question and to be honest one that I had to quickly brush up on before answering.

It's probably best to start with the basic theory behind why a wing works and how lift is created.

A wing fundamentally works by causing a pressure differential between the top and the bottom of the wing. The way this is normally achieved is by making the air travelling over the top of the wing travel faster by making it cover a greater distance.

Thiefed from http://science.howstuffworks.com/airplane6.htm

When you get a symmetrical wing you have the same profile across the top and the bottom of the wing and as such when the wing is 'flying' straight on then the air is moving over both the top and the bottom at equal rates thus not creating lift.

So as Khan stated, a symmetrical wing needs to have it's Angle of Attack (AOA) changed in order for it to start creating lift.

This has a couple of effects on the airflow across the wing, firstly it causes a deflection of the air down or up (depending on positive or negative AOA) and secondly it shifts the point at which the leading edge of the wing hits the air up or down having the end effect of making the wing effectively asymmetric again and creating lift.

Clear as mud?

A symmetrical wing has severl uses of which I don't really have application, the most noted of which is improved aerobatic performance, i.e. the wing flys just as well upside down as it does the right way up.

EDIT: Since I am making a glider and it is unpowered I ideally want the wing to work at a 0 Angle of Attack. If I made the wing with a positive AOA then it would introduce added drag and reduce the efficency of the aircraft.