Need some small aircraft statistics

[Lotnikus]

Hello
I want to design a model using numerical methods. One of many things I need for this project is mathematical formulas that would allow me to predict weight of wings, fuselage and tail. I couldn't find these anywhere, so I decided to create them on my own.
For this I need to gather some statistical data of some models and then find a correlation between their geometry, purpose and mass. Eventually, with some luck, I can find mathematical formulas connecting these factors and predict mass of a model during the design stage. It would be nice to gather as much data as possible, so every piece of information is very valuable.
Of course we can't treat every model the same, so I decided to look only for 'similar' models. Similarity here refers only to used materials and size.

Here's, how you can help me:

I'm looking for models with wingspan from 1.5m to 4m, with wings and tail made of classical materials (wood, balsa, plywood, etc.), small amounts of carbon or glass fibre are ok. Every material used for fuselage is ok. Engine also is not important. You can add models with piston or electric engine, and even gliders but please, add information about it.

If you have some free time and wish to help, spend some time measuring geometry and mass of your (or friend's) model (models) and fill in a form (You can tell others about it too :) ):

http://ageii.webpark.pl/anken.htm

Thanks to this I will try to create a database of models and then hopefully extract information I need. I would gladly share my results here, if I find anything

It's very important for me and I would be very grateful for any help

Lotnikus

[slipstick]

Predicting the mass of an element is very simple. All it needs is calculating how much of the various materials are used to make the wing/fuselage/tail and then looking up the density of the material.

Statistical analysis of a random collection of examples is not much better than guesswork.

Steve

[Lotnikus]

Yes, calculating quantities of various materials and looking for their densities would be a good method in some cases.
However there is one drawback for me here in this method:
I need theese estimates for an early design stage, where I don't know, how my model is going to look like inside in detail, so I can't calculate any quantities of materials.
Besides, since it's an early project stage I don't need very precise estimations.

[eflightray]

As someone who has built models using balsa wood for many years, selecting the wood is almost an 'art', density/weight can vary so much, easily double. That's why a balsa modeler will often spend ages going though the model shops stock looking for just the 'right' wood for the job.
If an electric powered model or free flight model, then the lightest is often required, if an I.C. model, then the weight may not be as important and plywood will also be used.
There are variations in foam density. The amount of resin used on/in fiberglass could make a big difference to weight. Even the quality of the paint finish makes a difference.
Scale models are often heavier because of the extra detail required.

There are so many variables that what you seem to be asking for could take a lifetime, even then with new/different materials being used, would never be up to date.

Just looking at all the various forums here on RCGroups for the different types of models, let alone the different models within each forum, would make the task impossible. Even choosing one class, say competition glider, the number of variables is enormous. And even they change subtlety from season to season to gain the latest advances and advantages.

And to me the most important thing of all cannot be incorporated in to a numerical system of design, what the final object looks like.

Some model manufacturers do use CNC machines to create their kits of parts, but someone still needs to use their creative ideas to 'design' the model in the first place.

[biber]

For manned aircraft, Lotnikus' statistical method is quite common and well proven.
Basically every manned aircraft type does go through the stage, where statistics are used to give a reasonably accurate picture of the numbers to be expected.
Of course, it works better for them, as they are designed more thoroughly in terms of structure mechanics, so they tend to have a very similar grade of material utilisation.
But I don't see, why well done statistics on models wouldn't work.

biber

[Lotnikus]

Yes, I want to use methods from designing manned aircraft in designing smaller, unmanned ones. When I gather enough data I always can reject small parts that differ from the rest too much. I just need to have enough statistical data.
Believe me, I know what am I doing and what is my aim. Only thing I don't know is taht if I will doo it. And I can't even try it without your help.

[Montag DP]

Lotnikus,

Sounds like a reasonable idea to me and I don't see why it wouldn't work. I may even be tempted to use some of the information you glean in early design stages of my own models.

What I would suggest is to create a thread in "Electric Plane Talk" (near the top of the RCGroups home page) asking people to give some specific information about their models: dimensions, weight, construction, power system type, or whatever you think is relevant.

Good luck,
Dan

[Lotnikus]

Thank you for your supprot
But I would like to see your models in this database. You can add smaller ones, let's say with wingspan from 1.2m
Every information I ask for is in the form:
http://ageii.webpark.pl/anken.htm

Lotnikus

[slipstick]

Sorry but, unless I'm reading it wrong, your form is asking for rather too much. I'm not prepared to pull my existing models apart in order to find the weight of the horizontal and vertical stabs or empty the fuselage to weigh all the equipment separately etc.

But if I ever build a new plane of the materials you're interested in I'll try to remember.

Good luck - Steve

[Lotnikus]

No, of course I'm not asking to tear apart your model. Only if you can disassemble it easy and fast. For example I build my models in a way I can easily disassemble them to transport and assemble them before flight, so it would be no big problem for me to measure parts. I think more people do their models this way.
Also, if you have any equipment burried and glued deep inside your model so you can't or don't want to pull out, you can usually find weight of theese components for example on manufacturer's website.


But if I ever build a new plane of the materials you're interested in I'll try to remember.
I'd appreciate that, however I would like to collect data as fast as possible.
Please, forgive me my impatience, but i'v been trying to look for help for a while with no luck and here is one of the last places where I'm trying, and slowly loosing hope for any help

regards
Lotnikus

[lincoln]

I've read a paper about something like this. I believe it was in an issue of Soar Tech. Suggest you contact Herk Stokely. Contact info at the UIUC low speed aerodynamics project, if not elsewhere, I bet. Happy Googling.

If you can't find it in a reasonable time, send me a PM and I'll see if I can find the article.

Some very detailed data here on a highly optimized wood wing and tail surfaces:
http://charlesriverrc.org/articles/allegrolite2m/Allegro_Lite.pdf

[Lotnikus]

Thank you lincoln
this data sheet about allegro lite is even more detailed tahan I need, nevertheless I'll add it to my database.

I'd also like to thank those few who also helped and filled in the form. The search is still on however. I'm still waiting for help.

regards
Lotnikus