creating scale shapes from 3 views
09-24-2008, 05:25 PM
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creating scale shapes from 3 views
ok, i am creating plans for a cessna 421a from a three view
http://richard.ferriere.free.fr/3vues/cessna421_3v.jpg
and i am trying to make my cross sections to make formers out of in a 2d cad program. the problem is, how do i figure out all the cross sections when i cant see any contours or anything? mostly thinking about the aft fuselage section starting around the door.
http://richard.ferriere.free.fr/3vues/cessna421_3v.jpg
and i am trying to make my cross sections to make formers out of in a 2d cad program. the problem is, how do i figure out all the cross sections when i cant see any contours or anything? mostly thinking about the aft fuselage section starting around the door.
09-24-2008, 06:39 PM
#2
RE: creating scale shapes from 3 views
From your 3-view shown the only information you have is the width and height of the cross sections. I would search for a better three view with actual cross sections.
09-24-2008, 08:52 PM
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RE: creating scale shapes from 3 views
You could likely get enough out of that to make up a "stand way back and squint" scale model but that 3view lacks seriously for making a decent scale model plan. Think of it this way.... if you blew up that sketch to the model's full size the lines would be around an inch wide.
Also as mentioned by Jim above there's just no way to determine the sections other than in a very general way and assume that they are scale versions of the only one you have which is the maximum width shape shown in the front view. If the full sized craft alters the shape then you have absolutely no way of knowing this from this small sketch.
Now if you can find a LOT of pictures of the plane from various angles and lighting conditions you can learn a lot about contours and shapes but not with any real accuracy. Certainly not to competition level of any sort. For that you need some seriously informative full on drawings with sections from a draughtsman you know you can trust for accuracy.
Also as mentioned by Jim above there's just no way to determine the sections other than in a very general way and assume that they are scale versions of the only one you have which is the maximum width shape shown in the front view. If the full sized craft alters the shape then you have absolutely no way of knowing this from this small sketch.
Now if you can find a LOT of pictures of the plane from various angles and lighting conditions you can learn a lot about contours and shapes but not with any real accuracy. Certainly not to competition level of any sort. For that you need some seriously informative full on drawings with sections from a draughtsman you know you can trust for accuracy.
09-24-2008, 11:27 PM
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RE: creating scale shapes from 3 views
Actually, without having all the planforms at the necessary stations poses a problem if you want an absolutely dead-on scale job. However, there are ways to get extremely close.
You have the top view and side views I presume along with the few cross sections provided. If you mark off where you want the additional stations for your other bulkheads, you have the width of the fuselage at that point and also the height and depth from the centerline. In one of the Dave Platt video series, Scratch This!, he explains a method of using a grid pattern to create the intermediate bulkheads. He also addresses the same process for doing wingribs from just the root and tip ribs. For me to go thru the entire process would be an extremely long and drawn out procedure. What I suggest is that you get that video series and watch and understand how he does his plans. He even mentions how to deal with jogs and cuts in the fuselage cross section. It's a definite learning experience.
You have the top view and side views I presume along with the few cross sections provided. If you mark off where you want the additional stations for your other bulkheads, you have the width of the fuselage at that point and also the height and depth from the centerline. In one of the Dave Platt video series, Scratch This!, he explains a method of using a grid pattern to create the intermediate bulkheads. He also addresses the same process for doing wingribs from just the root and tip ribs. For me to go thru the entire process would be an extremely long and drawn out procedure. What I suggest is that you get that video series and watch and understand how he does his plans. He even mentions how to deal with jogs and cuts in the fuselage cross section. It's a definite learning experience.
09-29-2008, 02:39 PM
#6
RE: creating scale shapes from 3 views
Your head on view represents the tallest section of the fuselage. Its perimeter provides the exact shape at that point.
Look at the top down view. The shape is identical back to a point toward the rear then the same shape is retained but
gets smaller and smaller all the way to the rear of the horiz stab. Double check this against the width & height to assure
this is correct.
Given this is true, there is a perimeter shape of the nose just ahead of the intersect point with the windshield. Because
you are able to measure from nose to tail and cross width of identified shapes on the drawing you can use these as
transition points to create a hot wire foam fuselage or to create new cross sections for use in CAD. Personally, by the
time you finish you could have already hot wired it... : )
The additional former shapes are subsets of the known ones because for the most part the fuselage is symetrical. Take
measurements across the top down view and side view to confirm if there are actual shape changes... It is rear on the
typical airframe prior to the late 70's. There are few, very few scale three views of civilian aircraft. Why? No one uses
a three view with a 1:1 airfame. All three views are artist renderings, not engineering drawings. The drawing referenced
is from a Cessna marketing brochure used to illustrate the general layout of the airframe.
This should be pretty easy to do on this Cessna. Obtaining photographs with which to confirm assumptions on shape &
proportion will make this even easier.
Hope this helped
Look at the top down view. The shape is identical back to a point toward the rear then the same shape is retained but
gets smaller and smaller all the way to the rear of the horiz stab. Double check this against the width & height to assure
this is correct.
Given this is true, there is a perimeter shape of the nose just ahead of the intersect point with the windshield. Because
you are able to measure from nose to tail and cross width of identified shapes on the drawing you can use these as
transition points to create a hot wire foam fuselage or to create new cross sections for use in CAD. Personally, by the
time you finish you could have already hot wired it... : )
The additional former shapes are subsets of the known ones because for the most part the fuselage is symetrical. Take
measurements across the top down view and side view to confirm if there are actual shape changes... It is rear on the
typical airframe prior to the late 70's. There are few, very few scale three views of civilian aircraft. Why? No one uses
a three view with a 1:1 airfame. All three views are artist renderings, not engineering drawings. The drawing referenced
is from a Cessna marketing brochure used to illustrate the general layout of the airframe.
This should be pretty easy to do on this Cessna. Obtaining photographs with which to confirm assumptions on shape &
proportion will make this even easier.
Hope this helped
09-29-2008, 06:17 PM
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RE: creating scale shapes from 3 views
I've heard of people buying a scale plastic model and cutting sections on a table saw or similar. You can probably find a local airport that is willing to help you by letting you take pictures of the real thing. Your best bet is to meet some mechanics.
09-30-2008, 06:04 AM
#9
RE: creating scale shapes from 3 views
Hi!
I found that there is 3d model of it. Look here http://www.flightsim.com/cgi/kds?$=main/review/c421/c421.htm
I think it is possible to extract it from simualtor file.
Here kit: http://www.yhmodels.com/big_.asp?pid=408&pmodel=YH175
Another build: http://www.rcuniverse.com/forum/m_46..._1/key_/tm.htm
Kostya
I found that there is 3d model of it. Look here http://www.flightsim.com/cgi/kds?$=main/review/c421/c421.htm
I think it is possible to extract it from simualtor file.
Here kit: http://www.yhmodels.com/big_.asp?pid=408&pmodel=YH175
Another build: http://www.rcuniverse.com/forum/m_46..._1/key_/tm.htm
Kostya
09-30-2008, 07:20 AM
#10
RE: creating scale shapes from 3 views
Actually you need not do any of this considering there is a planset from Hostetler,
laser cut short kits, retracts, spinners, and fiber glass components for it.
CESSNA 421C 24%:
Cowl, Windshield available from:
Fiberglass Specialties
15715 Ashmore Dr.
Garfield, Arkansas 72732
Phone: (479) 359-2429
FAX: (479) 359-2259
Web: www.fiberglassspecialtiesinc.com
E-mail: [email protected]
Decals available from:
Cajun R/C Specialties
602 S. Angel St.
Kaysville, UT 84037
Web: www.cajunrc.com
E-mail: [email protected]
Retracts available from:
[link=http://www.robart.com/retracts/drawings/HOST421main.pdf]Click To view mains drawing[/link]
[link=http://www.robart.com/retracts/drawings/HOST421nose.pdf]Click to view nose gear drawing[/link]
Robart Mfg. Inc.
P.O. Box 1247
St. Charles, IL 60174
(630)584-7616
Web: www.robart.com
E-mail: [email protected]
Laser Cut Short and Full Kits:
Laser Innovations, Inc.
Phone: 219-672-2794
E-mail: [email protected]
Precision Cut Kits
Phone: 609-538-1388
Web: [link=http://www.precisioncutkits.com]
PCK Website[/link]www.precisioncutkits.com
E-mail: [email protected]
CESSNA 421 C GOLDEN EAGLE 24% HOSTETLER 118"
CESSNA 421 24% REPL. WING ONLY HOSTETLER 118"
CESSNA 421C GOLDEN EAGLE 27% HOSTETLER 133"
Cessna 421C
Scale: 24% Span: 118" Length: 104.77" Power: 3.6 to 8 cu.in.
(Both Engines) - $51.50 plus $7.00 S & H
Cessna 421C
Scale: 27% Span: 133.25" Length: 117.87" Power: 4 to 8 cu.in.
(Both Engines) - $62.50 plus $9.00 S & H
[link=http://images.google.com/images?hl=en&q=Cessna%20421%20turbo%20eagle&um=1&ie=UTF-8&sa=N&tab=wi]RCU 421 build thread[/link]
10-05-2008, 04:03 AM
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