Building For Indoor Flight Duration.

We've had an enquiry from a new member who has a project on his hands.
I'll possibly move this thread to a new category ... maybe "Indoor Models" ... but for now it's a build project.

He e-mailed me this.

Hi Phil, thanks for your attention.
My model aircraft is not RC! It is hand lunched without any engines. There is an indoor competition that the model aircraft which has the most range is winner! also aircrafts must be hand made. We cut airfoils and put them beside each other, then we will cover it. I will attach a few photos 4 u.
Best wishes,
Amir

He did attach a few pictures but they just look like a standard towline glider.

Amir, .... please transfer any pictures to this thread & we'll all help as much as we can.

I'll direct him to this thread and see if he posts any more on the subject.

Pol.

I wonder if Amir wants something like this .... Microfilm will work on gliders as well :lol:

you need carbon fiber for all the ribs and spars.

Tony B. AKA Blooper wrote: you need carbon fiber for all the ribs and spars.

I don't think weight is the main problem here Tony ... If distance is the objective then even a heavy but fast model may be better than a light slow one.
You'd need to throw the heavy one a bit harder but that is just putting more energy into the flight ... which is a good thing.

I'd go for a built up balsa wing but a Pod & Boom style model so as to reduce drag .... (Could even do without the POD) :lol:

i would have thought being indoor lightness would be a big help.

cf tube fuse, very light balsa wings.

Jumbo jets have a glide angle of 20:1 ! Problem is, that's at 600kph!

Klipkopwildlife wrote: Jumbo jets have a glide angle of 20:1 ! Problem is, that's at 600kph!

My point exactly Tony.... Compare these two gliders coming in to land .... a heavy, fast, pylon racer type... or a very light thermal soarer... which will need the longest strip?

The thermal model will take ages to land but may not cover as much distance when launched from the same height. :S

The old boys at the indoor events have some interesting designs,I missed one from last wednesday its open to everyone and over 70 people turned up.Apparently quite a few midairs.

Which ever way we look at this it's a simple maths problem.

Providing the models are launched from the same height, the one with the shallowest glide angle is going to go the furthest .... regardless of speed.

I think that this simply means cutting drag and you won't get much better than a carbon boom for that.
Next is the wing section & aspect ratio. ..... high aspect ratio is more efficient & I believe a very thin flat bottomed or undercambered section is best for that.... (Correct me on this please)

www.airfieldmodels.com/information_sourc...s/about_airfoils.htm

Another thought ... a very long moment arm will mean you can get away with a smaller tail area & still get the same stabilizing effect.
A smaller, thinner tail area means less drag.
Weight is not the problem ... a heavier model will fly faster but may may have the same glide angle .... streamlining is the key to success.

Pol.

Speed isn't everything - don't forget that surface area (wetted area) drag cubes up with speed, so a fat slow flyer could have less drag than a greasy spear!

The faster model is less likely to be upset in flight by any turbulence, (ie air con!) than the slow one, but it will also hit obstacles harder, and cause itself more damage.

Eric wrote: Speed isn't everything - don't forget that surface area (wetted area) drag cubes up with speed, so a fat slow flyer could have less drag than a greasy spear!

The faster model is less likely to be upset in flight by any turbulence, (ie air con!) than the slow one, but it will also hit obstacles harder, and cause itself more damage.

Quite correct about the drag Eric ... I thought about that a few minutes after I'd posted. ..... HONESTLY! :lol:
I've got a funny feeling that seeing as Amir is only trying to build a model that will fly in a straight line indoors ... no aerobatic performance to consider ... I think he'll need as near to a flat sheet wing section as he can get & still retain some rigidity ... maybe a carbon spar leading edge??? :S
One of his main concerns will be accurate building so that the thing will stay in a straight line ... Possibly a bit of polyhedral like the one in my picture.
I remember messing about with gliders as a kid & my polyhedral ones always seemed more stable.

en.wikipedia.org/wiki/Drag_%28physics%29

polyphilla and polyhedral...... your biased.

Just my 2penny'oth!

At the bottom line its all going to come down to the (overall) lift/drag ratio.

At low Reynolds numbers the normal factors change a bit and at very low Reynolds numbers things change a lot, hence 'a bee can't fly' syndrome.

If it is just a straight line issue then the bigger the better and within limits the weight only determines how fast it travels along the same path. Full size gliders can just about achieve 60:1 and probably half as much again when in the ground effect.
The downside to size is the aerodynamics get more and more sensitive to get that last little bit of performance.

So does he have a size and weight limit?
These will set the basic aerodynamic characteristics.

Anything with undercamber is going to be too draggy in my opinion. High aspect ratio, flat bottom, somewhere between 6 and 8%. I go with the long boom to hold the empenage, which will be thin section, even just card.