Inverted Vantage
Formerly Unknown Target
- Joined
- Jun 19, 2008
- Messages
- 1,116
So yea, got this paper napkin version of an aircraft I'm planning to do (first a 5 foot UAV, then a 25 foot full version much later). I posted some general questions in the "Composites" sub forum, and here's a rough layout with nothing more than "gut" calculations - so I fully expect you guys to tell me a ton of stuff is wrong with this - but that's good! I want to know what to focus on 
But, if I'm wasting your time, please let me know.
To start off with, the aircraft is designed for test purposes, specifically engine testing and experience building with aircraft/rocket engine construction - so range, load carrying, all that stuff isn't really important. It will have to withstand 9+G loads, carry one person safely, and have an emergency parachute system (not shown on this doodle).
I've also built it at full scale (25 feet long with about a 33 foot wingspan from tip to tip), and will scale it down later when building the scale model.
Construction is either 3 ply fiberglass/PV foam/ 2 ply fiberglass sandwich, or 3 ply carbon fibre/2 ply kevlar (probably the former, the latter combination is too expensive! lol). A composite (probably carbon fibre with a foam core and several layers) will be used for the two main wing spars and the connecting spar between the forward canards. Carbon fibre push/pull rods will be used for steering, and the entire canard would rotate (as opposed to elevators on it), for ease of construction (although I was browsing through old pages and someone asked if this would make construction easier on a Long-EZ, and the answer was a resounding no, so please correct me if I'm wrong).
Each part (colored differently) is moulded seperately using a foam female mold, created out of a CNC machine, and then glued together using indenting joints (technical term is?), such as this (if you guys have a better moulding option, please tell me!) :
...with the spacing in between the joints filled with glue and sanded down n the outside to create a smooth surface. The bulkheads would also work like this - they would be about an inch thick, and mounted into indents inside the fuselage, then glued into place. Then, the upper portion of the mould would be placed on top and the bulkhead would be glued into place there. The bulkhead would then be supported by about an inch or so worth of carbon fibre embedded in the fuselage all the way around it's circumfrance (except about an inch or so on either side where it meets the fuselage seems).
The aircraft will be powered by two 600 lb/f (scale model) or two (or one, if it proves to be too big) 1500 lb/f (full version) rocket engines, fueled by propane/LOX (liquid oxygen).
In this exploded view, you can see the largeish LOX tank (green) right behind the pilot's seat, and the slightly smaller propane tank (light blue) right behind it. Tank quantities are unknown at the moment, as I have not done any math (I am -stupid- bad at math, which is why I'm going to ship this to my rocket guy to figure out the quantities). At the very end are the two rockets.
Protecting the pilot are three firewalls (aluminum? what should they be made out of?), visible as the green-gold plates, one behind the rocket engine, one behind the propane tank, and one behind the pilot's seat. Would shaping these into a semi-conical shape deflect any blasts rearward sufficiently, or would it be pointless? Would it be a problem to not implement these on the scale model, due to cost/machining problems?
Now on to the fuselage sections - as I already noted, they would be machined using female moulds (so that I could get a decent indent), and would be about 2 inches thick, maybe 3 to give adequate roots for the bulkhead joints. The black parts are the wing and canard spars - also previously noted, the canards rotate entirely, not just with elevators. I'm worried about the canard fairings producing some nasty turbulent drag - do you think that might be a problem? The spars are made of carbon fibre/kevlar reinforced foam, or fiberglass reinforced foam. They don't go fully through the wing, and they taper off to follow the wing's taper - should I go about doing the wing a different way? I would like to have a thin symetrical airfoil, to take advantage of the carbon fibre's smoothness and to provide good aerobatic performance. If I'm wrong with this, please let me know
Er, I think that's about it...oh, wait, almost forgot. I need a tail. I don't know where to put one to make the rod linkages easy to do (I have had NO experience doing rods and pulleys). I put the wing low on the fuselage and made the entire canard section rotate in an effort to make it as easy on myself as possible, but I don't have any way to put a rudder on easily - I thought about doing it EZ-style and sticking them on the winglets, but I wouldn't have the faintest idea how to do the pulleys and whatnot for that. It won't fit on top in the rear without moulding it so it would be bolted onto the upper carbon fibre shell, with the control cable running along a raised spine on the top of the aircraft, and I had strength concerns about that. Any ideas?
So yea, if the aircraft looks simply wrong, or too draggy (probably going to cover those wheels with pants), or something I'm doing is completely, well, bad, please let me know! Thanks
Oh, and before I forget, some pictures of the thing actually put together, and a video of the assembaly;
But, if I'm wasting your time, please let me know.To start off with, the aircraft is designed for test purposes, specifically engine testing and experience building with aircraft/rocket engine construction - so range, load carrying, all that stuff isn't really important. It will have to withstand 9+G loads, carry one person safely, and have an emergency parachute system (not shown on this doodle).
I've also built it at full scale (25 feet long with about a 33 foot wingspan from tip to tip), and will scale it down later when building the scale model.
Construction is either 3 ply fiberglass/PV foam/ 2 ply fiberglass sandwich, or 3 ply carbon fibre/2 ply kevlar (probably the former, the latter combination is too expensive! lol). A composite (probably carbon fibre with a foam core and several layers) will be used for the two main wing spars and the connecting spar between the forward canards. Carbon fibre push/pull rods will be used for steering, and the entire canard would rotate (as opposed to elevators on it), for ease of construction (although I was browsing through old pages and someone asked if this would make construction easier on a Long-EZ, and the answer was a resounding no, so please correct me if I'm wrong).
Each part (colored differently) is moulded seperately using a foam female mold, created out of a CNC machine, and then glued together using indenting joints (technical term is?), such as this (if you guys have a better moulding option, please tell me!
) :
...with the spacing in between the joints filled with glue and sanded down n the outside to create a smooth surface. The bulkheads would also work like this - they would be about an inch thick, and mounted into indents inside the fuselage, then glued into place. Then, the upper portion of the mould would be placed on top and the bulkhead would be glued into place there. The bulkhead would then be supported by about an inch or so worth of carbon fibre embedded in the fuselage all the way around it's circumfrance (except about an inch or so on either side where it meets the fuselage seems).
The aircraft will be powered by two 600 lb/f (scale model) or two (or one, if it proves to be too big) 1500 lb/f (full version) rocket engines, fueled by propane/LOX (liquid oxygen).
In this exploded view, you can see the largeish LOX tank (green) right behind the pilot's seat, and the slightly smaller propane tank (light blue) right behind it. Tank quantities are unknown at the moment, as I have not done any math (I am -stupid- bad at math, which is why I'm going to ship this to my rocket guy to figure out the quantities). At the very end are the two rockets.
Protecting the pilot are three firewalls (aluminum? what should they be made out of?), visible as the green-gold plates, one behind the rocket engine, one behind the propane tank, and one behind the pilot's seat. Would shaping these into a semi-conical shape deflect any blasts rearward sufficiently, or would it be pointless? Would it be a problem to not implement these on the scale model, due to cost/machining problems?
Now on to the fuselage sections - as I already noted, they would be machined using female moulds (so that I could get a decent indent), and would be about 2 inches thick, maybe 3 to give adequate roots for the bulkhead joints. The black parts are the wing and canard spars - also previously noted, the canards rotate entirely, not just with elevators. I'm worried about the canard fairings producing some nasty turbulent drag - do you think that might be a problem? The spars are made of carbon fibre/kevlar reinforced foam, or fiberglass reinforced foam. They don't go fully through the wing, and they taper off to follow the wing's taper - should I go about doing the wing a different way? I would like to have a thin symetrical airfoil, to take advantage of the carbon fibre's smoothness and to provide good aerobatic performance. If I'm wrong with this, please let me know
Er, I think that's about it...oh, wait, almost forgot. I need a tail. I don't know where to put one to make the rod linkages easy to do (I have had NO experience doing rods and pulleys). I put the wing low on the fuselage and made the entire canard section rotate in an effort to make it as easy on myself as possible, but I don't have any way to put a rudder on easily - I thought about doing it EZ-style and sticking them on the winglets, but I wouldn't have the faintest idea how to do the pulleys and whatnot for that. It won't fit on top in the rear without moulding it so it would be bolted onto the upper carbon fibre shell, with the control cable running along a raised spine on the top of the aircraft, and I had strength concerns about that. Any ideas?
So yea, if the aircraft looks simply wrong, or too draggy (probably going to cover those wheels with pants), or something I'm doing is completely, well, bad, please let me know! Thanks
Oh, and before I forget, some pictures of the thing actually put together, and a video of the assembaly;
