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orion

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Thank you for the input - I have seen the process you describe and it works great. The problem though is that for now I've only seen it with round tube, not square. The other drawback is that you have to have specially cut and formed tools, which for that process can be somewhat costly.

I've spent the last week or so mulling over several different ideas, and I think I've finally arrived at a couple of conclusions regarding this project. One of those is that I should probably stick to something that I know well. While I know aluminum fabrication very well, I know composites even better.

So, as of today (03/12/05) it looks like the airplane will be based on a composite structure however, the process to manufacture it will be very different from what we see in the industry today. There's still a few bugs to work out but it looks really promising, and I'm more sure of it working right the first time.

The wings will most likely still be aluminum though.
 

Dieselfume

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I believe GM has been using a similar "hydroforming" process for making frame rails on pickup trucks. I can't imagine the setup being cheap, but if you crank out hundreds of thousands of frames a year, it certainly cuts down on production time.
 

orion

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As I mentioned above, the aircraft has been relofted to better reflect the composite approach. The wing is still anticipated to be aluminum but the body will be molded.
 

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dustind

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How is the airplane comming? The pictures look great.

Also, is it possible to use an unducted fan on your airplane? If it makes a difference, I was thinking of making a more rounded cowling if I bought your airplane in order to fit an automotive engine.
 

orion

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Unducted fans usually don't work too well in tractor configurations.

The work is now a bit slow since I had to go virtually back to square one to redesign the concept for the new laminate approach (for the fuselage). I am still working out some of the ideas and bugs. If I did this like everyone else, it would be relatively simple but I'm trying to improve on some of the techniques of assembly, so now the little details are taking a bit longer.

I've got some other upcoming work starting next week so I'll be off this set of design tasks for a couple of weeks. I will however post update pictures as soon as I have them.
 

Leighton

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Hey Orion,

odd question, are you designing the plane or are you designing the Kit?
i dont want to stand on my own d*** here but i wouldve thought it would be easier to design the plane and then find a way to turn it into a kit? (ala Van's) im sure you have rationale behind it...

ps, am loving the concept pictures thus far, VERY sexy looking plane.
 

orion

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Both tasks are being done simultaneously. While what you say is true, it would have been easier just to concetrate on the plane at first, the problem with that approach is that if you don't take into consideration the issues of amateur assembly, you will often have to redesign the airplane as it enters the kit development process. I don't want to do all this twice.

As long as you do this up front, the process is not all that difficult, although there is a bit of problem solving that you would not have to do otherwise. However, I've been doing this in one form or another for quite a while so it's not really a big deal. The issue I have now though is that I'm working with several new approaches to the construction process and its associated structures and techniques.

One of the issues is that the outer surface will come to the builder all finished. This will eliminate all sanding, painting, polishing, etc. (sort of like an RC ARF). But to do this right, the assembly process has to take into account the few areas that will need things like structural fasteners that will have to extend through the skin. This has to be done so that the items that penetrate the outer skin will detract as little as possible from the provided aesthetic and it is this that is forcing me into several tight structural corners. I think I got most of it solved but I still have to model it all to make sure.

However, in the mean time, I still have to make a living for now with other contracts, so the process is not going as fast as I would like. Oh well, back to the grind :gig: .
 

orion

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04/28 update - Based on several emails I received over the past few weeks, there were a number of folks interested in what the tandem aircraft will look like. Since I was still tweaking the single, I took one of the variants and did the stretch modification just to get a quick preview.

A couple of the mods being evaluated for the single are a slightly shorter tailcone and a slightly modifed tailcone loft that will result in the aft end being a couple of inches higher off the gorund.

This latest configuration of the single is then what I used to crate the tandem aircraft attached here:
 

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orion

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Here is another iso view, this time from the front. The goal for the interior loft was such that the two crew can sit comfortably, without the aft passenger having to straddle the front seat.

Besides the fuselage stretch, the longer airplane also needed the wings a bit further aft to account for the heavier tail.
 

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orion

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And finally, here is just a plain side view. I haven't really decided what to do about the canopy yet since what we have here is pretty large. It could be done in one piece as shown but there is also an opportunity to split it in such a way as to incorporate a bit of a roll-over structure between the seats. Don't know yet.

I also haven't decided yet whether I like this shorter tail or whether I should keep the original longer one, which extends a bit over a foot past where this one ends.
 

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Falco Rob

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Orion,

I'm no aeronautical engineer but I can see your problem with how to deal with the canopy. If the tandem version is in one piece it will be quite heavy and also a bit of a handfull to restrain when opening in a strong wind - it's basically a large sail.

Maybe the centre roll bar as you suggested and two canopies each hinged at their rear edge, like some military jets. Clear access for entry / egress and a fail safe locking mechanism may be a bit of a challenge to engineer but it would give additional strength to the cockpit sides and also look very cool!

One other thing I've noticed is the very low sills, which implies that the fuselage sides must be quite heavy / well reinforced to carry the bending and torsion loads.

Is this just a matter of more composite laminates or do you have a sill beam of some sort?

Rob

ps. a very slick looking aeroplane, BTW.
 

orion

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When it comes to tooling up all these pieces, the sills may end up a bit higher. However, the reason for the low sides is to increase the overall visibility. I've piloted several airplanes where the canopy seems to cover only just the head, or the lower window edge is just about at my shoulder. I never found this very satisfactory since if the cockpit was wide enough for me to fit comfortably (a rare event), the sill was far enough away so that I could see only straight out the side, but very little down. On some airplanes this was very disconcerting when coming into a tight strip.

I also used to own a couple of Grummans - quite a difference in visibility between these airplanes and many homebuilts. For that matter, many certified airplanes too. That memory alone drives me often to design airplanes with plenty of glass area.

But as you say, the low sill will require a very stiff fuselage with a substantial amount of reinforcement. I've been looking at the engine loads and the rather close coupling between the upper and lower engine mount firewall hardpoints. Originally I was going to incorporate a steel framework into the laminate there but, later, I concluded that a good laminate with a correct design will be lighter and do a much better job of distributing the engine and nosegear associated loads.

The overall fuse is pretty tall so incorporating the necessary structure is relatively simple. The canopy sill (actually the whole cockpit length) will incorporate a longeron, but it will be a built up graphite part of the overall laminate makup.

I still haven't made up my mind whether I like the shorter tail cone or not. I think that will take a couple of days just staring at the pictures. All part of the design process I guess.
 

dustind

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Are you choosing the tail length based on looks? Will it fly any differently after it is finished? I assume the longer tail will have smaller control surfaces due to the extra leverage?

I am not sure which tail looks better.

Both models look great.
 

CNCRouterman

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OAL-Tail section

Bill,
Does the longer version have better spin avoidance/recovery characteristics than the shorter version? Is it going to affect the manufacturing process, ie: will there be any extra challenges in building the tools or forming the initial skin? Personally I like the longer version a little better. However, I would let the answers to the above two questions drive the vote more than the aesthetics.

On the other hand, I suppose that the shorter version would be a tad more responsive, as in quicker, true?

Which would have less drag, the shorter one with less wetted area, or the longer one with gentler curves?

What is the airspeed velocity of an unladen swallow?

Had a MP moment there.
 

orion

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In my experience, about half of the effort at this stage of a development is placed on aesthetic refinement. We of course all have different views on what's attractive, but the major component of design for virtually any product is, to the best of one's ability, maximizing that product's appeal.

In answer to your questions, the shorter tail version addresses an issue of production, while still trying to address my valuation of its aesthetics. Personally, I like the longer tail. I think it looks better and airplanes with longer tailcones fly better, suffer from lower trim drag, fly with better response (more lever arm for the control surfaces to respond through) and provide a greater resistance to spin. And yes, when you have a longer tail you can reduce the size of the tail surfaces.

The issue I ran into is that the fuselage outer skin will be fabricated from a toughened acrylic plastic (similar to some cars of today). This plastic is vacuum formed and the only machine locally that can do my prototypes is limited to just under twenty feet. This is no problem for the single place but may become an issue for the larger tandem airplane since I do not want to make the fuse in two parts, with a vertical splice line somewhere at the aft portion of the cockpit.

The goal is to produce the single and tandem with the same tool. The only change would be an inserted tooling piece in the cockpit middle for the elongation.

As far as the surface drag is concerned, the difference between the two is only about 1.5 feet and as such, the drag difference would most likely be immesurable.

African or European?

Nit!
 

CNCRouterman

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Datum points?

Is the fuse` length mesured from the firewall or the front of the engine cowling?

Pass the Holy Hand Grenade, and remember thine number of wheels shalt be three, five is right out!
 

orion

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Amazing the perspective one gets after much consideration, a few glasses of wine (last night, not this morning), and several hours of nothing but playing with the geometry. The bottom line, the long version won out. I relofted the tailcone of the single a bit higher at the end than before (only about an inch or two) and stretched the loft to accomodate two pilots my size. When I got the last variant lofted and rendered, it just looked right.

The fuselage structure of the tandem is now just a hair less than twenty feet, making it a tight fit for the vacuum machine but I think it is possible. This then allows the parts to be made by this machine for all four variants of this design.

Eric, the length I am concerned with is from the forward recessed flange located at the firewall (recess is for sliding the cowl over), to the aft bulkhead, located just under the main spar and hingeline of the horizontal tail.
 

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orion

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And here is the two place. The cockpit is actually a bit shorter than in the previous pictures, allowing for a slightly smaller canopy. I think I'll open the canopy upward about an aft hinge, in a similar fashion to that of an F-14. I may still play a bit with the canopy lines to see if I can make it make more structural sense.
 

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