From 3 views to plug?
04-26-2002, 08:18 PM
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From 3 views to plug?
I have full size three views of a sport jet I'm designing. Looking for suggestions to go from 3 views to a plug to be used for making molds. TIA
04-27-2002, 01:42 AM
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3-Views to Plug
Hi,
If you're using a CAD system, you use this "eyeball" method to get close, and to refine the cross-section shapes. Create 3 "plan holders" in your CAD program, which can hold images of your 3-views. (Side view, Top view, and Front view) - (See image attached)
First, use your CAD program to do just the outlines, then go back and gradually start creating and refining cross-sections. I've used this method with good success on 3 different models, and it works.
Of course, if you're not using CAD, then you'll have to create some overlays (I suggest gridded Vellum) to refine your cross sections.
I usually then create the parting board first, from the side view of the fuselage, using the cutout as the center "keel" in the plug, and attach half formers at the appropriate places on this keel. Then, you can either sheet or plank the thing, or cut blocks of foam to fit in between the formers and sand it down to the level of the formers, to create your basic shape. I highly recommend the sheeting/planking method over the foam method, as it produces a more precise shape, and is a lot easier to correct and glass. The foam will require a LOT of filler before glassing.
There's a complete tutorial on my web site (below) on the "Design and Building Tips" page.
Good luck!
If you're using a CAD system, you use this "eyeball" method to get close, and to refine the cross-section shapes. Create 3 "plan holders" in your CAD program, which can hold images of your 3-views. (Side view, Top view, and Front view) - (See image attached)
First, use your CAD program to do just the outlines, then go back and gradually start creating and refining cross-sections. I've used this method with good success on 3 different models, and it works.
Of course, if you're not using CAD, then you'll have to create some overlays (I suggest gridded Vellum) to refine your cross sections.
I usually then create the parting board first, from the side view of the fuselage, using the cutout as the center "keel" in the plug, and attach half formers at the appropriate places on this keel. Then, you can either sheet or plank the thing, or cut blocks of foam to fit in between the formers and sand it down to the level of the formers, to create your basic shape. I highly recommend the sheeting/planking method over the foam method, as it produces a more precise shape, and is a lot easier to correct and glass. The foam will require a LOT of filler before glassing.
There's a complete tutorial on my web site (below) on the "Design and Building Tips" page.
Good luck!
04-27-2002, 12:46 PM
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3 views to plug
Thanks for the rely. The big problem is I'm not quite sure how to "create" the cross sections. BTW, these 3 views happen to be hand drawn. This is my first attempt at designing from the ground up. Any additional assistance would be appreciated. Thanks
04-27-2002, 07:04 PM
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Cross-sections, plugs, etc..
This is easy with a "boxy" trainer, and of course becomes trickier with a more modern compound surface shape. If you've already drawn 3-views, then you already know the outermost dimensions of all of your parts, so draw rectangles at those dimensions, and start smoothing the corners.
You must have some idea of the overall shape in mind...
Will it be round, or maybe like a private turboprop, a "rounded oval", "rounded triangle", or something else? Once you have that in mind, this is what I would do:
Start at the nose, and work your way back to the tail. Typically the first section or two will be the most round, with the shape changing to accomodate the "cabin", engine compartment, landing gear, etc. On average, pick at least 6 or 8 sections to define. Only you can decide how the shape should look. The landing gear area, for example, might have to be a little more "square, to make sure that the gear can retract inside. (or the gear doors could have a "bulge" in them, as an option) The shapes all obviously have to allow for your engine, etc..
Decide what you want the thing to look like, and draw a horizontal and vertical centerline on some paper. Then draw all of your sections on separate pieces of transparent acetate, or on tracing paper, vellum, etc.. The reason you do that is so that you can stack them up, and see how much the shape changes from one section to the next. Most aircraft have smooth transitions from one shape to the next. A compass and a french curve will help you draw smooth lines. I'd draw half a former at a time, then flip it over to create the other half, assuming that you want the thing bi-laterally symmetrical.
If you're not comfortable with this, I suggest making a small "hand toss glider" sized model out of foam or soft balsa, just creating the shape by hand. When it looks right, carefully band saw it into sections, and look at the shape that way. If your small model is precise, you could even trace those slices, and enlarge them to the proper scale. Typically, a fuselage will achieve it's widest point at about the same place as the wing's thickest point.
Another way to start is to just draw all of your internal equipment onto a copy of your 3-views, (radio, engine, landing gear, servo linkages, etc.) and go from there. If there are specific questions, ask them here. There are a LOT of people reading this forum who have successfully designed and flown good looking models, and I'm sure that one of us can help you. A lot of them have traded ideas with me, and it's been a great experience!
You must have some idea of the overall shape in mind...
Will it be round, or maybe like a private turboprop, a "rounded oval", "rounded triangle", or something else? Once you have that in mind, this is what I would do:
Start at the nose, and work your way back to the tail. Typically the first section or two will be the most round, with the shape changing to accomodate the "cabin", engine compartment, landing gear, etc. On average, pick at least 6 or 8 sections to define. Only you can decide how the shape should look. The landing gear area, for example, might have to be a little more "square, to make sure that the gear can retract inside. (or the gear doors could have a "bulge" in them, as an option) The shapes all obviously have to allow for your engine, etc..
Decide what you want the thing to look like, and draw a horizontal and vertical centerline on some paper. Then draw all of your sections on separate pieces of transparent acetate, or on tracing paper, vellum, etc.. The reason you do that is so that you can stack them up, and see how much the shape changes from one section to the next. Most aircraft have smooth transitions from one shape to the next. A compass and a french curve will help you draw smooth lines. I'd draw half a former at a time, then flip it over to create the other half, assuming that you want the thing bi-laterally symmetrical.
If you're not comfortable with this, I suggest making a small "hand toss glider" sized model out of foam or soft balsa, just creating the shape by hand. When it looks right, carefully band saw it into sections, and look at the shape that way. If your small model is precise, you could even trace those slices, and enlarge them to the proper scale. Typically, a fuselage will achieve it's widest point at about the same place as the wing's thickest point.
Another way to start is to just draw all of your internal equipment onto a copy of your 3-views, (radio, engine, landing gear, servo linkages, etc.) and go from there. If there are specific questions, ask them here. There are a LOT of people reading this forum who have successfully designed and flown good looking models, and I'm sure that one of us can help you. A lot of them have traded ideas with me, and it's been a great experience!
05-13-2002, 12:53 AM
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From 3 views to plug?
Mike great information as always. I have been searching the web for 3 view drawings of a lear 24E with no luck. Would you happen to know of where a person could aquire these 3 views and the naca airfoil for a century III wing? Thanks for sharing the wealth of information you possess.
05-13-2002, 06:19 AM
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For Viper16
Well, first of all thanks for making me look like a genius. (But I assure you I'm not.)
Hmm...
Doesn't seem to be much readily findable on the Lear 24 on the internet. I did my usual ("Sherlock", on a Mac) search, using both "Learjet" and "Learjet 24" as search criteria, and got very little, other than some used aircraft for sale. Bombadier's site wasn't much help either. I did find this, which is pretty technical. It's research on the Lear 24 for a flight simulator profile, that has a lot of stats about the aircraft's performance. The advisor on this research was Michael Selig, so it's probably good data.
http://amber.aae.uiuc.edu/~jscott/si...24/linear.html
If I run across any other model 24 info, I'll let you know. The airfoil is pretty simple. If you can find out the NACA number, I can plot it for you and email the plot to you in any graphics format you prefer. Just let me know.
Hmm...
Doesn't seem to be much readily findable on the Lear 24 on the internet. I did my usual ("Sherlock", on a Mac) search, using both "Learjet" and "Learjet 24" as search criteria, and got very little, other than some used aircraft for sale. Bombadier's site wasn't much help either. I did find this, which is pretty technical. It's research on the Lear 24 for a flight simulator profile, that has a lot of stats about the aircraft's performance. The advisor on this research was Michael Selig, so it's probably good data.
http://amber.aae.uiuc.edu/~jscott/si...24/linear.html
If I run across any other model 24 info, I'll let you know. The airfoil is pretty simple. If you can find out the NACA number, I can plot it for you and email the plot to you in any graphics format you prefer. Just let me know.
