FlyerBry

My Feedback: (8)

When creating plans from three-view drawings the profile of the plane is easy enough, but how does one come up with correct fuselage former shapes that accurately depict the shape and curves of the real aircraft?

Are there any good books on the subject?

Thanks!

FlyerBry

JonnyJohnston

Well, what particular plane are you trying to create sections for? We will go from there. I may have some, and yes, just lying around here some where.

Jon

ps I have a lofting and conics tutorial for AutoCAD with the lisp files. If you use AutoCAD or another program that can read dwg/dxf files and uses lisp.

dicknadine

are you using Cad or the old fashion way? either way, all you can do is look, look for photos to come up with a relitive close shape. believe there are a couple of programs out there that can convert photo shapes a close cross section. the computor method is way over my head. also it only is scaled by a judge and he has to have a reference to look at. dick

Mike James

Yep...

3-views of the profile type simply do not contain the data required to create accurate cross sections. But...

You can, of course, "eyeball" the shape, go measure a real plane, cut up a plastic model, or accept someone else's drawings. We all do these things. If you have a CAD program that does renderings with light and shadows, you can also do something else...

This may seem odd at first, but it works at least as well as the "eyeball" method. Find the best photos you can of the aircraft you're modeling. Render a view of your plane in your CAD program, doing your best to recreate the lighting, and the reflectivity of the plane. (If you're familiar with your software, it isn't that hard.) Then you can compare where reflections, shadows, and distortions of any kind appear, and adjust your model to fit. Many companies take aerial photos of their planes backlit against a sunset and some clouds. This creates some very useful reflections on a shiny airplane.

If you want to slice up a plastic model, I have an article on how to do that, at http://homepage.mac.com/mikejames/pl...c_to_rc01.html

If you want to use your 3-views directly in CAD, tracing over them, I have an article on that at http://homepage.mac.com/mikejames/rc...drcdesign.html

If others here come up with their own methods, I'd love to see them. We all need to do this task from time to time.

FlyerBry

My Feedback: (8)

Thanks for the replies... I don't have a particular plane in mind when considering the topic. I'm getting into scratch building from plans and started to think ahead to scratch building something that hadn't been done before (or at least plans aren't readily available) and started to think about the process.

I kind of figured part of the process would take some guesstimation of some sort. It seems that someone has always come up with a good technique for this and that when a building problem comes up so I was hoping I could learn a bit in the process. The idea of cutting up plastic models is a good one that didn't even occur to me but it makes perfect sense.

Some great info so far. Thanks!

BMatthews

For stand WAY off sport scale models eyeballing works as well as any method. Like suggested looking at shadow lines and highlights in picture helps a lot. But the best way is to do a bit more researching and come up with better drawings that have sections in them. Sources like Paul Matt, Wylam, Nye and others did great drawings of this sort. There's many others as well. And consider that most small 3 views are so compact that the lines come out way too thick for any sort of accurate guessing when blown up to trace over. Far better to start with finer lined and better detailed plans. But if it's just for fun then have at it.

Rocketeer10

I would agree that with a couple of known cross sections from the 3-view, you can estimate what you need to complete the plan. Such as firewall, the LE of the wing saddle section and perhaps on more cross section aft of the cockpit. The stack the cross sections and loft the one in between. If you care to spend the money Dave Platt has a series of tapes/DVDs on design and construction in his Black Art series. it is called "Scratch This!" and he shows how he does all the desgin work to develop a st of drawings for a Guaridan aircraft. I thought the info pretty appliable to CAD for developing formers, airfoils etc. Check his website at: www.daveplattmodels.com

Cheers,
GY

tom.laird

Hi,
I am currently converting a 3-view to a plan outline by using Corel Trace to convert the bitmap into a vector for use in AutoCad. Is there an easier way?
BR
Tom Laird

Highflight

My Feedback: (4)

I'm not sure there are any easier ways, just different ways. I like and have been using Adobe Streamline for quite a while with good results.

Keep in mind that the only purpose for doing so (the vector conversion) is to get an accurate scale outline for drawing/designing your own plans in CAD (the more accurate the 3-view, the more accurate the vector conversion and subsequent plans you draw). It's still a "hands on" process where you are only using the imported vector drawing as a guide (not as the actual outline for your plans), so any program that can do the conversion at all is probably as good as any other for the purpose.

Highflight

tom.laird

Hi,
Thanks for the reply. Although I am a draughtsman by trade, and have been building kits for about 20 years, this is my first atempt at using Autocad to do this type of plan, so all and any advice is more than gratefuly received. There seems to be plenty of advice, help and reading on this forum so I'll be having a good look before I start.

best regards

[email protected]

CadFlyer

My Feedback: (16)

Regardless of how you do it you must establish a correct reference point that you know is correct and work from there if you want any possibility of it being true. I have been designing the planes in CAD for many years now. When I take a scanned image into Cad the first thing I do is find out the correct dimension of a few key pieces of the plane. Such as, height & width of firewall, lead and trailing edge formers and the tail former (if possible). I have accomplished this many times by contacting the Smithsoniun, AF museum and Grumman history center. They can over the phone give you a few of these key dimension. Then you will have to lay the rest out in cad and match the others up as close as possible to the image/3-views but just make sure that everything lines up and is true with everything else even if the 3-views don't match perfectly. Once you have done this a few times you will have a better understand of where you can "fudge" and where things need to be exact.
Good Luck,
Cadflyer

CoosBayLumber

My Feedback: (1)

Much of what has been noted I believe is correct, however there is some additional data and steps not noted to which you ought to be made aware.

Unless you are interested in an A/C from some third world manufacturer, you should not have to go to the efforts of translating information out of a book or magazine. Especially when we are considering some very small drawing which was made to fit the paper. I have done this a couple of times already, and most often the publisher (or the reader) thinks the small drawing a work of art. Only the original draftsman knows where the fudging went on. I did a plan from some magazine 3-view a few years ago in which the A/C had swept wings. No surprize when I found that the angle for the leading edges to the wings did not match between the top view and the bottom view.

Take heed of what has been noted about inaccuracies of the plan to actual dimensions of a real A/C when you get going. Many of the photo altering softwares will permit you to alter the X-Y scale factors. Thus if you have a known length and a known span, the factors can be altered a few percentages in order to come out correctly.

Keep the drawing units fully the same until you are completely finished. As dimensions for A/C are generally given in real feet and inches, do all your linework at this 1=1 factor. In Autocad, you can then easily open up a Paperspace drawing, XREF in the lines or whole work from the three-view, and alter the ratio to fit the paper or your proposed model scale. Thus, for a light plane, it may have a wingspan of 30-40 feet, and do all your drawing (or tracing) at that ratio. To do this, open up a dummy drawing in Paperspace, and set the ratio within the window to 1/8XP or 1/12XP. You can easily go back and forth between the model sized plan and the real sized plan by doing it this way. Then when finished, it can readily be plotted out to that point, and see if maybe there needs to be an adjustment or so.

One other item, do not put too much effort into the drawings. As mentioned use the edges only for alignment. After you get a few lines drawn, then it is time to see how the small scale A/C matches up to the time proven model A/C formulae. Most often you will need to enlarge the tail feathers, and lengthen the fuselage. Don't be concerned with but the outline and position of the wing. Real A/C airfoils seldom replicate the performance on a model A/C, so do not put too much effort into this. Go with a model airfoil from the beginning and use the incidences noted in the formulae for setting the wing A.O.A. too. If the model aircraft you are thinking of is going to use retracting gear, then the real airfoils are often too thin to permit a fit. Thus you need to plan on using a thicker airfoil from the start.


Wm.

Rocketeer10

A company I have used to convert raster to vector is http://www.designpresentation.com/
You can ask for a quote and they are reasonably fast in turning around jobs.
GY

Highflight

My Feedback: (4)

Omigod, Gerry, don't pay for it!

PM me, and I'll give you my email address where you can send some .tif scans of your 3-views.
I'll turn them into vectors, put 'em into Autocad, export them as a .dxf and email it back to you so you can import it into your CAD program and get to work.

That's way too easy of a thing to have to pay for.

Highflight

dicknadine

cutting up a plastic model sounds good-- however where did their cross sections come from ? again its eye-ball all the way. one of the best is the old Wyams(?) plans. the same old story exists-- what documentation does the judge have. are YOU satisfied ? dick

FlyerBry

My Feedback: (8)

With all the talk of using CAD, what is the best way to get started. I have a copy of TurboCad which is very affordable but I don't want to learn one program only to be disappointed that I didn't learn ACAD from the start. Is there a "lite" version of ACAD that has the minimum bells and whistles necessary for model aircraft design at a reasonable price?

FlyerBry

CoosBayLumber

My Feedback: (1)

Best situation here is to attend an Adult school or Night school that has a technical program. We have three of these schools around here that generally teach it at about $30-$50 per semester at some high school. Most of these schools that offer CAD drawing learning usually use Acad. They often use either the latest full blown educational version or the Lite version. Not too many outside the big city will teach with any other software, generally because the industry talks Autocad, not OtherCAD.

Even if you do not choose to purchase Acad after completion of the semester, you easily pick up enough tricks that it helps at home with whatever you obtain. Big thing in going to any of these type of classes, is that you need to learn how to connect and use the computer hardwares associated with CAD. If you do not find out how to connect and use these items, you may be paying some techy to install the item in your home for megabucks. And just because the instructor po-poos your questions with a responce that "Once you are hired by a biggie firm...." let him know you are going to be a one man or part time firm, so need to know.


Wm.

FlyerBry

My Feedback: (8)

No problem with the hardware for me. I'm an IT guy. I actually used to support a bunch of interior designers that used ACAD R12/R13. I knew all the details of supporting ACAD but never learned how to really do anything with it beyond a few lines for test prints and such. If I had known then that I would be into RC I would have paid more attention to the software!

BillS

The Drawing Room at:
EngSw.com
might give you some ideas.

Thanks.

Bill