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Mac790

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Hello Gray
I believe the vertical is 16ft^2.
Do you remember the rudder size, I'll try to find it in your previous attachments tomorrow.
I see. I think that just cutting off some of the lower area is going to take away from the smooth elliptical shape. I will see if I can make the entire aft portion smaller.
Did you forget about mother nature check out that dolphin picture, thick belly (probably after dinner:gig:) and slim tail, proportions are really important. But if you are going to build the aluminium fuse don't even worry/think about it, it's hard enough.
The main spar sits between the pilot and the RIO, between the RIO's instrument panel and, the aft spar will be pinned.
Ok now everything is clear, I was looking on your top view and I was worried but it seems that everything is OK.

Seb
 

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Gray Out

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Hello Topaz,

Must say that piercing the firewall with the mounts seems iffy to me, given the actual purpose of the thing. Those rubber grommets aren't likely to survive an engine fire for any significant time, and will allow smoke and gases into the cockpit unless the latter carries a positive pressure compared to the engine compartment. Any chance the mount can be modified so that those legs don't have to pierce the firewall?
Problem solved.;) It may not seem like it, but I listen to everyone.
See picture attached. I still have to work out the motor frame, but on a positive note, the box which denotes where the motor will be is the actual size of the motor clearances. I attached an attachment that shows the motor around which I'm designing it...a rotary.

Just a thought. Seems like any significant air gap between the bulkhead and the seatback would allow a little convection to cool the latter. Even just an inch or two.
Problem solved.;)
The gap is now 0.8 feet to the forward firewall. The sound and heatproofing will still be implemented anyway.

Is the aft spar carrying the drag and torsion loads from the wing, or just the torsion loads? If (edit) it is (/edit)carrying drag loads (which would be fairly common), what's keeping them from crushing the rear cockpit longeron inwards? Some sort of beam on each side, under the armrest, carrying the load to the seat-back bulkhead and forward to the main spar attach? Like I said, I haven't read through the whole thread, so perhaps you already have that resolved.
I haven't completed the full connections yet. Both spars are however connected to much more than just the frames or longerons. As you can see by the picture attached, there are inner and exterior closure ribs (red) which will spread the loads out into the fuselage framing, longerons and skins in that area. A small frame like you describe to fend off the longitudinal loads will definitely help, but I didn't get to any of that yet.

All of this is picking nits - it's a great looking airplane. I'll look forward to seeing how it develops! :gig:
Thanks for the kind words. Nit pick all you want. All help is appreciated and humbly accepted.

Thanks
 

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Gray Out

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Hello Mac,

Did you forget about mother nature check out that dolphin picture, thick belly (probably after dinner:gig:) and slim tail, proportions are really important. But if you are going to build the aluminium fuse don't even worry/think about it, it's hard enough.
No I didn't forget Mother Nature. If you forget her, Father Time kicks your behind.

Nor did I forget to try to reduce the area. I am still thinking about how I may want to do it since the aft most bulkhead where the shaft connects to the propeller is now about 9 inches diameter and I'm not sure what is the minimum I can get away with.

Thanks
 

Topaz

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...Problem solved.;) It may not seem like it, but I listen to everyone.
See picture attached. I still have to work out the motor frame, but on a positive note, the box which denotes where the motor will be is the actual size of the motor clearances. I attached an attachment that shows the motor around which I'm designing it...a rotary....
Interesting. Who is the supplier on that motor? I haven't kept up on motors much, and I didn't know that there is a 100hp rotary (Wankel, right?) available on the market today. I thought the only offerings were much more powerful.

I wasn't necessarily suggesting that the engine mount couldn't touch the main bulkhead, only that I had a concern with the mount tubing actually passing through the bulkhead. Conventional tractor motor mounts are attached to the firewall bulkhead, and that kind of bolt-through attachment seems to be fire-proof enough. If this works for you, though, then cool. :)
 

Topaz

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...Nor did I forget to try to reduce the area. I am still thinking about how I may want to do it since the aft most bulkhead where the shaft connects to the propeller is now about 9 inches diameter and I'm not sure what is the minimum I can get away with.
Mostly a matter of structure and airflow separation. And ease of construction.

While the inflow field to the prop will tend to keep the airflow attached over a steeper tailcone angle, the effect diminishes the farther forward from the prop you go, and the logical place to start 'pinching' the fuselage is right aft of the wing trailing edge - an area already prone to separation.

I don't know. Much as the 'pressure recovery' fuselage shape sure is sexy and might gain you a few knots if you can pull it off, I'm not sure it's worth the extra time to build the compound-curved shapes. And if the airflow does separate, you'll not only get the extra drag of that separation, you'll interfere with the efficiency of the propeller. It will now be operating in a turbulent inflow field over at least part of its rotation, and that's a receipe for noise, vibration, and reduced thrust at all airspeeds.

Haven't seen Orion around here for the last few days, and I'm sure he'd have a far more experienced opinion on this situation than I do.
 

Gray Out

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Interesting. Who is the supplier on that motor? I haven't kept up on motors much, and I didn't know that there is a 100hp rotary (Wankel, right?) available on the market today. I thought the only offerings were much more powerful.
Topaz,

These are Rotamax. They are a new line for aviation and range from as low as a FAR 103 65HP to as high as 360HP. The PDF I have is quite large and won't attach, but send me an e-mail by private message and I'll send it out to you. They have information on there for all of them in that range. The one I chose is for the ASTM-SLSA, but they have experimentals in there too for insanely loww prices...ie, 130HP for $6,600.00.:shock:

Thanks
 

Topaz

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Huh. I'll send you that PM, although my own design doesn't need a motor - at all. Still, it's nice to keep up on what's going on, and I do want to do a motorglider/cruising airplane someday. :)
 

Gray Out

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I don't know. Much as the 'pressure recovery' fuselage shape sure is sexy and might gain you a few knots if you can pull it off, I'm not sure it's worth the extra time to build the compound-curved shapes. And if the airflow does separate, you'll not only get the extra drag of that separation, you'll interfere with the efficiency of the propeller. It will now be operating in a turbulent inflow field over at least part of its rotation, and that's a receipe for noise, vibration, and reduced thrust at all airspeeds.
Topaz,
Thanks for the info. Is that "pressure recovery" fuselage like the pods? I never heard of that term. I attached a picture of what it sounds like to me.


Edit: I tried to attach a fuselage study that I remember I had also. If I'm correct in how I interpreted it, that pressure fuselage shouldn;t even be bothered with. It was too big.:depressed

Thanks
 

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Topaz

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Topaz,
Thanks for the info. Is that "pressure recovery" fuselage like the pods? I never heard of that term. I attached a picture of what it sounds like to me....
Couple of different things come to mind. I got the term "pressure recovery" from an excellent series of articles by John Roncz (the airfoil designer) called "Designing Your Homebuilt" that appeared in Sport Aviation back in late 1989 and early 1990. The articles used as an example a design called the "Forte" that John and his partners were going to build for their own personal use. As far as I know, the airplane was never actually built. Basically the idea was, as I understand it, to use the aft fuselage shape to return the pressure to near-atmospheric, and so provide a 'push' (or at least a drag reduction) to the fuselage overall, since the pressure around the top, sides, and bottom of the fuselage forward of the wing (but aft of the stagnation-pressure areas on the nose and front-most portion of the canopy) are seeing lower-than-atmospheric pressure. The curved 'inflow' shape supposedly promotes that, but I suspect that it takes a significant CFD study to shape the fuselage to get any significant effect. Roncz had access to that kind of software, so he could do the optimization that was necessary to combine that shape with one that would supress flow separation on the wing root - an even bigger potential source of drag.

The other option - and one closer to the image you included with this post - is the so-called "wake field propeller" and body. The effect is most commonly cited with reference to the Cessna Skymaster, where the energy input from the aft propeller can force the airflow to remain attached to even a very steep inflow angle on the aft fuselage. The propeller effectively operates in - and modifies - the "wake field" of the fuselage shape. The net result can be interpreted as either increasing the efficiency of the propeller (sometimes to values in excess of 100%) or a net reduction in drag for the fuselage, when either is compared to a case where the propeller is absent, which generally produces massive separation. I personally think that saying that the propeller has over 100% efficiency (compared to a similar propeller on the front of the body) is a spurious argument, and that the drag-reduction description is more accurate. However, it must be said that the propeller - when in 'on design' conditions - does have a net thrust increase, since it's operating in slower, lower energy air than the free-stream. Modern submarine designs make extensive use of this technology. Why don't we see it on airplanes? It's highly dependant upon "on-design" conditions, particularly the angle of attack of the prop/body combination with respect to the airflow. Airplanes see significant changes in angle of attack. Submarines generally don't.

I don't think it's applicable to a practical airplane design, but if you're interested in the wake-field propeller from a purely academic standpoint, look up the following AIAA paper: AIAA-86-2693, "Aerodynamic Design of Low-Speed Aircraft With a NASA Fuselage/Wake-Propeller Configuration." It's probably out of date research by now (it's from 1986), but it's a good introduction to the concept.
 
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plncraze

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If you search the site you will find some responses by Orion about these topics. I had been interested in them as well and Orion's responses were enlightening. The short answer is that both the pressure recovery fuselage and wake prop are point designs. Once they are away from the design parameters they are expected to work in their efficacy drops. If you had the experience though it would be interesting to try to enlarge the "point" in which they work as airfoil designers did with the laminar bucket.
 

Gray Out

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Hello to all...Happy New Years,

Did some more work and have the general structural position arrangement made for the fuselage (99%), wing (100%) and the v-tail (90%). I attached 3 quick pictures to give an idea and for perusal or comments.

I'm still working to complete the fuselage and v-tail and will provide those soon...however, I have come to the point where the final loft and finalization for the wing is almost upon me, so it is time to disclose the foil selection. I have received some information which has pretty much confirmed my initial selection. Thanks goes out to Topaz. I have decided to iterate different foil planforms utilizing the GA35A315 inboard encompassing the entire flapped area and flaps then transitioning to a GA35A415 outboard to the horner wing tips.

The first is to use either foil for the full span with the symmetrical taper of .5 in chord and height. This did not reduce any time for construction.

The second, and the one I chose, is sort of a mix between what I chose and some things which were verbalized (written) that made some sense. As above, the 315 will start at the root and shoot outboard to the flap/aileron junction with a symmetrical taper of .5 in chord and height. At the transition, (which you can see was flawless :)) the 415 will shoot outboard to the hoerner tips with a symmetrical taper of .5 chordwise only and the height of the foil will remain constant to the tip. In other words, the height at the tip, plus the hoerner cutaway, will be the same height as the height at the transition. This provides a thicker section outboard to delay stall at the tips as will the higher camber for the tip and the ailerons at higher a'soa. I'm not certain what consequences this planform triggers, but any advice is welcome since this will be the final loft and rearrangement of all components..again.:depressed

I'm attaching a couple of pictures of the lofted foil for a visual idea. The red is the 315 and the yellow is the 415. The plan view with the original wing is only to provide a perspective on the flap and aileron junction and will be replaced with the new foil. I think this (these) foils are amazing if their drag curves are indicative of their CL range and performance. The CM is also quite low which should reduce pitching and subsequently more control surface drag. Still learning how to better interpret the curves, but, again, a discussion with some diagrams explaining how to interpret them further is welcomed and appreciated.

Question. What causes this foil to have such a high increase of lift with such a minimal increase in drag from a CL of .1 to about .9 and how do I know the best "bucket" range? For example, the CL in cruise for the Peregrine is .272 and the CL for climb is .775. Is that the "bucket" boundaries?

Thanks
 

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bmcj

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Hi Gray Out,

Be careful about having the front spar too far back. A friend of mine was doing an aerobatic demo at a Florida airshow in the Murphy Renegade (Spirit?) for the Murphy Aircraft folks. It had a long nose rib with the lead spar set an arm's length behind the leading edge. During one of the maneuvers, the whole leading edge folded forward of the spar, making it necessary for him to bail out. The Renegade wing has been redesigned because of this. This was when the Renegade was first introduced, so I believe that all kits/plans (did they make a kit?) went out with the redesigned wing.

Bruce :)
 

Gray Out

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Hi Gray Out,

Be careful about having the front spar too far back. A friend of mine was doing an aerobatic demo at a Florida airshow in the Murphy Renegade (Spirit?) for the Murphy Aircraft folks. It had a long nose rib with the lead spar set an arm's length behind the leading edge. During one of the maneuvers, the whole leading edge folded forward of the spar, making it necessary for him to bail out. The Renegade wing has been redesigned because of this. This was when the Renegade was first introduced, so I believe that all kits/plans (did they make a kit?) went out with the redesigned wing.

Bruce :)
Hello BMCJ...

Thanks for the warning. I will most certainly revisit that issue when I am lofting out the final. An arms length huh?:ermm: I always thought that the main spar should be placed at the thickest portion of the foil? Right now the Peregrine has the greatest distance of 1.7' from the leading edge to the spar at the root where it connects to the fuselage and it gets smaller outboard to .8' at the tip. What was the maneuver and what was the findings for the failure?

Speaking of the foil. Topaz has pointed out something so obvious that I feel kind of angry that I didn't catch it. The outboard foil is no longer a GA35A415 because when I made it a constant depth without tapering like I did the chord, it is now well above a 20% foil, so I will change it soon.

I'm still looking at several options at this point and may explore one further...but I'm not sure as of yet.

Thanks
 

Topaz

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...Speaking of the foil. Topaz has pointed out something so obvious that I feel kind of angry that I didn't catch it....
Don't be hard on yourself. This is a huge learning process. I shudder to think about the mistakes I'm still making! :gig:
 

Gray Out

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Hello to all,

Thanks Topaz...I got over it fairly quickly.:)
Okay. I completed the general structure arrangement for the V Tail and the fuselage so I am attaching some pictures for perusal. Please feel welcome to point out anything that may appear to be out of the normal.

Obviously some things will change. I had a very difficult time trying to tie in the V structure because of the damned shaft position and had to go with a centerline beam. If anyone has any simpler suggestions it would be appreciated. The reason that you find the forward spar on the V so close to the leading edge is because it was pointed out that there were some failure by divergence for the Bonanza's so I'm attempting to eliminate that so I had to beef it up.;)

Now it's brake time then on to the foils and re-loft the final iteration to start the actual plans and dimensioning. Then for obvious reasons...a scale model.

Speaking of the model, I was thinking of making it 1/4 scale and an idea came to me. If I bought the engine and propeller for the prototype first (since it will probably not change in HP or brand) I was thinking maybe I can use it to power a wind tunnel that I can use to test the scale model? It would give me a chance to break in the motor and get data on the design before I build it out. Any suggestions? Any suggestions on scaling the wind velocity from the propeller for the scale model in order to get the accurate data? Any ideas?:ermm:

Thanks
 

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Topaz

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...Okay. I completed the general structure arrangement for the V Tail and the fuselage so I am attaching some pictures for perusal. Please feel welcome to point out anything that may appear to be out of the normal.

Obviously some things will change. I had a very difficult time trying to tie in the V structure because of the damned shaft position and had to go with a centerline beam. If anyone has any simpler suggestions it would be appreciated....
How about a beefed-up ring frame at the forward and aft spar stations of the V-tail? You'll need some rings anyway to keep the aft fuselage stiff, so why not kill two birds with one stone?
...Now it's brake time then on to the foils and re-loft the final iteration to start the actual plans and dimensioning. Then for obvious reasons...a scale model....
You missed a step. Or three.

Unless I've missed a bunch of posts, you need to finish up the stability and control analysis so that you have a reasonable idea of how the thing will actually fly. If you're still picking out wing airfoils and geometry, that work is far from complete.

Then it's on to calculating the loads on all the parts, resulting from all the pertinant points on the flight envelope.

Then on to structural analysis for all the parts, using those loads, to ensure that what you've drawn can actually support the loads it'll bear in service.

Then you can start thinking about drawing dimensioned parts and plans.

I know you've got Raymer's Aircraft Design, A Conceptual Approach. All of that book's work - the complete conceptual phase design - needs to be done before you start working on your loads calculations, etc.

I wouldn't bother with a model until at least the conceptual work is done. The shape and size of the fuselage and flying surfaces may change during the course of that work, rendering your model useless.
 

Gray Out

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Hello Topaz...

How about a beefed-up ring frame at the forward and aft spar stations of the V-tail? You'll need some rings anyway to keep the aft fuselage stiff, so why not kill two birds with one stone?
Well, actually this has already been done with the other ring frames beefed up as well because I calculated the components to a factor of 5 instead of 7 and forgot to add them to the drawing. I will need to reposition and recalculate them a bit further, but I'll leave that for the final loft. I have attached them for perusal.

You missed a step. Or three.
Unless I've missed a bunch of posts, you need to finish up the stability and control analysis so that you have a reasonable idea of how the thing will actually fly. If you're still picking out wing airfoils and geometry, that work is far from complete.
Chances are good that you may be right. With my limited knowlege and experience it may be 57 steps missed, but, I'm doing the best that I can with what I have and, I'm not designing the new and improved shuttle. I do however understand that either one can kill you if done incorrectly so I am proceeding with intended speed and caution.

Stability and control analysis is probably 99% complete with some exceptions to recalculating to the new figures for weights and distances. You would be surprised at how much "calculating" and "analyzing" has already been done. See summary attached.

Then it's on to calculating the loads on all the parts, resulting from all the pertinant points on the flight envelope.
Done...see summary attached.

Then on to structural analysis for all the parts, using those loads, to ensure that what you've drawn can actually support the loads it'll bear in service.
Done to a close calculation. The final calculations will be made when the final loft is taking place and little if any changes are made to the design. See attached main spar section for perusal.

Then you can start thinking about drawing dimensioned parts and plans.
Actually, not only is "then" right now, but, through this whole process, then has always been now. I have tried with extreme difficulty to follow a systematic step 1, step 2, then step 3, method and it did not work because I always found myself going back to step 1 when things changed at step 3, so, I just proceeded as change required it and at this point in time, it is time to think about a final iteration and on to the plans for the model. Don't get me wrong...it could be months before the first dimension is drawn.

I know you've got Raymer's Aircraft Design, A Conceptual Approach. All of that book's work - the complete conceptual phase design - needs to be done before you start working on your loads calculations, etc. I wouldn't bother with a model until at least the conceptual work is done. The shape and size of the fuselage and flying surfaces may change during the course of that work, rendering your model useless.
I don't believe I have "done" the entire phase, although it can be said I tried, but instead I had to adapt a lot of it for aircraft that is in the lower velocity range. I think the book is an excellent "compilation" of works from many authoritative sources, but to be quite honest, the book is not for weight and velocity restricted craft even if it can be used for that purpose.

I want to apologize for providing such a small summary for your review. It usually takes a long time to find it then paste it and then hope the file isn't too big to attach it. I started to do that for the community to peruse and comment, but I gave up on providing the bulk of the work because the participation on the work done was so disproportionately "absent". Don't construe this to be a sign of ungratefulness...I am very grateful for all comments on the design, it's just that it was a lot of work that triggered a lot of questions that have still gone unanswered, so I take the best guess and hope the test pilot is smart enough to bring a parachute because I have not considered a BRS for this design.:para:

I do have it all and will be happy to provide it to you or anyone else that would like to look at it. Just drop me an e-mail, but be aware that the spreadsheets and information calculated and gathered so far is quite large.

Everything will be fine. If I was able to make a paper plane that flew across the room when I was much younger and only knew how to fold the paper, I think I can design the Peregrine to take-off, fly and land safely...at least more than once.:)


Thanks
 

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orion

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......I'm doing the best that I can with what I have and, I'm not designing the new and improved shuttle.

......I don't believe I have "done" the entire phase, although it can be said I tried, but instead I had to adapt a lot of it for aircraft that is in the lower velocity range.
Whether designing a shuttle, a fighter or an LSA, the steps within the typical design process are identical. True, for higher performance the subsequent analysis will tend to be more detailed but the phases for lower speed need to be covered just as for higher performance applications.

The reasoning you post above is typical of those who are trying to convince themselves that this need not be so difficult but who don't have the background necessary for a complete understanding of the process.

To be fair, we of course have not seen your work nor what it covered but given what you show and what you ask, I'll agree with Topaz and suggest that it does bring up a basis for concern.
 

Gray Out

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Hello Orion,

Whether designing a shuttle, a fighter or an LSA, the steps within the typical design process are identical. True, for higher performance the subsequent analysis will tend to be more detailed but the phases for lower speed need to be covered just as for higher performance applications.
It is my unqualified opinion that this has been covered. If and when the time comes a second "qualified" opinion is always an option and some of those errors can be mitigated. I consult this forum often and that has been helpful.

The reasoning you post above is typical of those who are trying to convince themselves that this need not be so difficult but who don't have the background necessary for a complete understanding of the process.
I never thought of it that way but I would have to say this may be true. In all reality, I can't think of a single time that I considered my work "professional" or declared my knowledge "superior". However, I am in a very knowlegable forum from where I learn so that puts me in the category where I can't be selective about from where I learn. Another point I would like you to know is that I would never undermine the intelligence or effort that was required from someone to obtain "complete understanding of the process" and many times praise their efforts.

To be fair, we of course have not seen your work nor what it covered but given what you show and what you ask, I'll agree with Topaz and suggest that it does bring up a basis for concern.
I would be lying if I told you that I do not respect your person or your position. I consider you an intelligent and accomplished individual. For those reasons, I thank you and Topaz for expressing your concerns and I apologize if they have caused any inconvenience. I will make an effort to be more cautious. My work is public and available at your request. I would be honored to have any qualified individual square me away.

Would you share some of those concerns so that I can go back and study it again? I would appreciate it more than I would a lecture on what is "typical" of people like me. I know how that one goes already.

I want to end this by saying that many times these forums don't always "express" true meaning to what is being written and there may be times where I may have failed to "express" it as such, but I say hello to everyone on posts and responses and I always thank them on the same. I say this because I didn't construe your response to be combative and did not want you to think that my response is retaliatory. It isn't.

Thanks
 
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