divad_strebor
Well-Known Member
- Joined
- Jun 2, 2008
- Messages
- 100
G'day everyone... Some of you may have already seen my posts in "introduce yourself" but for those who haven't, here is the design I have in mind to build in the next couple of years.
The requirements of the design are:
- The aircraft must be registerable in Australia as an ultralight
- Must have good STOL capabilities
- Must have good visibility
- All metal construction (Aluminium wings/tail feathers, steel tube fuselage)
- Must cruise like its NOT STOL. (eg: 100kts+)
The way I had in mind to achieve numbers 2 and 5 is to have BIG fowler flaps, coupled with ailerons (eg: 40 degrees full flap, 12 - 15 degrees aileron deflection. Give or take) and to have clean lines when the flaps are up (eg: streamlined single struts, low fuselage surface area, etc)
I posted a picture in my other post which I will post here as well (grab_008.jpg) which shows the basic layout I initially came up with when I started pulling all this out of my head and into the computer. That 3d model was done on a simple freeware 3d modeling program called metasequoia, and is very handy for producing the "look" you want. Its easy to use (compared to AutoCad) and its free, so its got a lot going for it.
After producing the model in Metasequoia, I export it to AutoCad. I then scale the model to give me the wingspan I want, then start rebuilding each airfame component with AutoCad solids, rounding off to common sizes as I go. All the other shots I will be uploading here are what I have done so far in this step.
Some of the questions I have so far:
- As was brought up in the other topic, I'm not sure if the tailboom will be stiff enough. The plan as it stands at the moment is to make it from 6"dia 7075 T6 aluminium with approx 1/4" wall thickness. I can get the tube if I want it, but its not cheap, so I want to be sure that it will be suitable before I start spending money.
- As you can see in the front view image, it has a gull type wing. I have a reasonably good idea of how to produce spars for this feature, but I'd like to hear other ideas as well.
- I intend to attach the strut to the rear mainspar (ie: the middle set of lines in "grab_13"... the rear set is the aileron/flap hinge line) and I'm not sure if the wing would be tortionally strong enough to be supported that far behind the center of lift? Are there ways of making the wing rigid enough?
- I'm not sure how many ribs should be in the wing or how far apart they should be. In designing model aircraft I used a rule of thumb which was pretty well right for EVERY size aircraft I ever built, eg: 4' span right through to 12' span. That rule of thumb was roughly 3" spacing between each rib. It did vary a bit in some aircraft, it depended on what the aircraft was designed to do. But it was a starting point. Is there such a rule of thumb when it comes to full size?
Thats all the questions I can think of right now, I know I have more, but I've driven 2115km in the last 4 days so my brain is pretty much mush. Anyway, heres the pictures...
Disclaimer: The model is FAR from finished. I know there are bits missing from the fuselage structure (for example), but I'm not getting too carried away finishing it just yet as I am vividly aware that major dimensions may change yet. The multi-faceted look of the flying surfaces is simply to keep the file size down. I can make it all look smooth, but the file size goes through the roof and slows my PC to a snail's pace.
The requirements of the design are:
- The aircraft must be registerable in Australia as an ultralight
- Must have good STOL capabilities
- Must have good visibility
- All metal construction (Aluminium wings/tail feathers, steel tube fuselage)
- Must cruise like its NOT STOL. (eg: 100kts+)
The way I had in mind to achieve numbers 2 and 5 is to have BIG fowler flaps, coupled with ailerons (eg: 40 degrees full flap, 12 - 15 degrees aileron deflection. Give or take) and to have clean lines when the flaps are up (eg: streamlined single struts, low fuselage surface area, etc)
I posted a picture in my other post which I will post here as well (grab_008.jpg) which shows the basic layout I initially came up with when I started pulling all this out of my head and into the computer. That 3d model was done on a simple freeware 3d modeling program called metasequoia, and is very handy for producing the "look" you want. Its easy to use (compared to AutoCad) and its free, so its got a lot going for it.
After producing the model in Metasequoia, I export it to AutoCad. I then scale the model to give me the wingspan I want, then start rebuilding each airfame component with AutoCad solids, rounding off to common sizes as I go. All the other shots I will be uploading here are what I have done so far in this step.
Some of the questions I have so far:
- As was brought up in the other topic, I'm not sure if the tailboom will be stiff enough. The plan as it stands at the moment is to make it from 6"dia 7075 T6 aluminium with approx 1/4" wall thickness. I can get the tube if I want it, but its not cheap, so I want to be sure that it will be suitable before I start spending money.
- As you can see in the front view image, it has a gull type wing. I have a reasonably good idea of how to produce spars for this feature, but I'd like to hear other ideas as well.
- I intend to attach the strut to the rear mainspar (ie: the middle set of lines in "grab_13"... the rear set is the aileron/flap hinge line) and I'm not sure if the wing would be tortionally strong enough to be supported that far behind the center of lift? Are there ways of making the wing rigid enough?
- I'm not sure how many ribs should be in the wing or how far apart they should be. In designing model aircraft I used a rule of thumb which was pretty well right for EVERY size aircraft I ever built, eg: 4' span right through to 12' span. That rule of thumb was roughly 3" spacing between each rib. It did vary a bit in some aircraft, it depended on what the aircraft was designed to do. But it was a starting point. Is there such a rule of thumb when it comes to full size?
Thats all the questions I can think of right now, I know I have more, but I've driven 2115km in the last 4 days so my brain is pretty much mush. Anyway, heres the pictures...
Disclaimer: The model is FAR from finished. I know there are bits missing from the fuselage structure (for example), but I'm not getting too carried away finishing it just yet as I am vividly aware that major dimensions may change yet. The multi-faceted look of the flying surfaces is simply to keep the file size down. I can make it all look smooth, but the file size goes through the roof and slows my PC to a snail's pace.
