Building Without Plans - RC Groups
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Jan 01, 2015, 08:47 PM
AndyKunz's Avatar
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Building Without Plans


PREFACE: About a month ago I was asked to publish on RCGroups my "Building Without Plans" article that was in Flying Models January 2013. I retained the rights to this article as part of the deal with Carstens prior to them closing their doors.

I will break the article (as submitted to FM) into multiple posts over the next little bit. There will probably be more photos than in the printed version, and more info in the captions.

I urge you to ask questions! This was a fun build, and the model now hangs in my brother's physics classroom at a high school in NJ to encourage students regarding aviation.


SCRATCH CONSTRUCTION SANS THE PLANS!

This summer (2012) our area was in a drought. I had not mowed my lawn since early May, and everything was brown. Some trees had already started turning as if it were autumn. It made for great flying all summer, as we never missed a weekend due to rain. A week or so before Labor Day we had some rain, just enough to start reviving the grass enough to mow again. Then came the big news – remnants of Hurricane Irene would be visiting us for the Labor Day weekend. Three days of rain, no work and no flying. What to do? What to do? I know, I'll build a model!

I had long wanted to build a stand-off scale micro model of the Fairchild A-10 Warthog. I had started gathering bits for it – two E-Flite MiG-15 fans, some Spektrum ultra micro servos, Castle 5A ESCs – but didn't have plans. I did find some good 3-views on the Internet, so I built directly from them. What I'm going to describe in this article is how it was accomplished, and how you can do the same for a model that you've wanted but don't have plans for. We will look at techniques and some shortcuts that are appropriate for a one-off model, especially a smaller one. Basically, we will scale the 3-views to the right size, sketch in some rough plans, and build.

There are many Internet sites with 3-views. I find them simply by searching for the plane I want, downloading several different versions until I find one with the largest pixel count and detail. Get in the habit of collecting 3-views this way and you'll never lack for a building project.

I usually scale micro Pattern planes to about 100 sq in of wing area. For others I use a comparable Horizon Hobby UMX model as a reference. Horizon doesn't have any twin EDFs though, so I looked up the MiG-15 specs and found that it had about 53 sq in. As a twin, I would want to have more area to carry the weight of the extra fan and battery. I decided to target 90 sq in. The added weight would mean it would need to fly fast too. It's a jet – speed is a good thing!

I imported the 3-view images into Adobe Illustrator and scaled the wings to the area I wanted. You need to do a little math here to convert the image from the imported size to the desired size. For instance, if you calculate the wing area as imported and it comes out to 50 sq in at 20 in span, and you want 90 sq in, you need to find the square root of the ratio 90/50 and scale the dimensions by that number. If you have a spreadsheet program this can be very easily performed. (FRANK – CAN WE PUT A SPREADSHEET ON THE WEB?) (2015: Here's the spreadsheet link)

The 3-Views I selected for my source were in three files, and scaled differently. After I got the top view scaled, I imported the side view and then had to manually scale it and align it so that the fuselage length was the same in both views. I got it to within 1/16” which was close enough and, because the side view was larger, it would also adjust automatically for the way the length would decrease as the sides were pulled in. By the way, since we're not making a Scale Masters project, “close enough” will be a key idea to remember. Finally I imported the front and rear view and scaled it to match the top view. This gave me the shape for the formers I would need as well as the scale dihedral.

To be continued...
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Jan 01, 2015, 09:24 PM
Registered User
jtroutt19's Avatar
Awesome Been waiting for this! Can not wait to read the rest!
Jan 01, 2015, 10:13 PM
Registered User
DGrant's Avatar
Subscribing.. this will be interesting. Thanks for sharing.
Jan 02, 2015, 01:58 AM
B for Bruce
BMatthews's Avatar
but.... but.... by using the 3views and doing the things you're saying aren't you creating plans to work from?

I guess I'll just have to read the installments as they come.
Jan 02, 2015, 05:01 AM
An itch?. Scratch build.
eflightray's Avatar
True scratch building to me, no plan, no kit of parts, just experience over the years.

I start with a 3-view, import it into SketchUp and scale it to get the relevant dimensions.
Way back when, it was a case of using a copying machine to enlarge a 3-view big enough to copy onto some graph paper, then draw out the graph squares at the size required

Then it's out with a roll of wallpaper backing paper, draw just the outlines and possible former locations. A sort of 'plan' but not what anyone else could build from, I doubt I could even build a second identical one. Most of the 'plan' is in the builder head. (Make that, most of the mistakes are in the builder head ).

Many of the foamie scratch builders probably draw on the foam, or just dive in and cut it using the TLAR method.
Jan 02, 2015, 08:14 AM
Registered User
Those mis-matching three views are a PITA!

Sounds like you do about what I do, but with different software. I convert the drawings to .jpg's, edit them in Paint, then trace them in TurboCAD.

I trace the wing area shown on the plans, then use the sq. root of the desired wing area/original drawing's area to rescale the overall drawing (using half a panel works well enough).

Once I get the outline, it's time to import the airfoil and hardware files, then start drawing. Over the years, I've standardized my files library, including a selection of airfoils I like.

I usually save off a copy of the traced, sized drawing, for use in making covering templates. That way, I don't have to remove the innards or play with layers when doing markings.

A suggestion for those wanting to try their hand in drawing up their own plans, but not sure about doing a scale ship is to do a "scale model of a model". Pick a set of plans from the Outerzone, etc. If it's in .pdf format, convert it to .jpg with a snapshot tool, then trace over the model drawing as you would a scale ship. It'll most likely have a simpler outline and will have the proportions to fly better than a lot of scale models.

I did that with a scan of the Mini-Mambo and came out with a delightful flyer that weighed less than half the weight of the original, yet had about 10% more wing area.

CD

CD
Jan 02, 2015, 11:15 AM
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AA5BY's Avatar
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Jan 02, 2015, 12:51 PM
Registered User
Using 3 views is 'challenging' .
FEW are similar when overlaid, most being grossly varying.
I've even found erm.. accuracy problems in Arthur Bentley drawings.. Formers don't match (at all) .. Sigh.
Had to triple check that. Even Idols can seemingly have clay feet
Maybe I'm too picky being a designer for over 35 years.
Still one presumes whomever is drawing is... alive.. during the work.

Plan forms and Former sections are all that's needed IMO.
Trace the outlines, cut and assemble.. Not Rokit Science.. just work.
Method & materials entirely up to the builder..
Like TRIX (remember those?) ... plans are for Kids :_)
Jan 02, 2015, 01:33 PM
AndyKunz's Avatar
This is going to be fun with you guys reading along! I hope to learn a thing or two myself!

Andy


Most programs will allow you to print a PDF and/or tile the output. Since I have a large format inkjet plotter, I printed three copies of the 3-views out and checked the results, but you could have them printed at your favorite office supply store. My wing area worked out to be 93 sq in (close enough). I was shocked at how big the fuselage would be. VERY roomy inside compared to the micro Pattern models I had done in the past. I was also shocked at how big the nacelles turned out. Placing one of the E-Flite fans on the side view, the scale outline dwarfed the little guy. Because I had what I felt was sound reasoning behind me regarding the wing loading and area, I decided to ignore the nacelle size difference. We'll have to wait and see how that turned out ...

So far I had invested about an hour and a half, including the Internet search. Now that I had workable 3-views at the right size, it became time to convert them into crude plans. This is where “close enough” really shines! The first thing to do was make sure that the left and right sides of the top view were identical. In fact, it turned out that the right wing panel was 1/8” more span than the left. To compensate, we would need to pick one side as the master. I chose the left (larger) side, since it would allow me to build on the right side by simply moving one rib a little farther out from the root. I began marking the centerline and then LE and TE outlines I would use for building, being sure to make left and right identical. This marking of lines is necessary because the enlarged 3-views show the pixels as large squares, making a very wide line. Simply dividing the line down the center with a straight edge and pen took care of that for me. After the outline was in place, I needed to mark the rib positions and the location of the spar, then of the ailerons. Aileron sizing was done according to the TLAR principle of model aircraft design (That Looks About Right), with a smidgen of round numbers – they're 3/4” wide to fit some stock I had handy and that's about the same as the scale ailerons would be, although mine are more of the span than scale would have been. The stab was “designed” the same way.

On to the fuselage side view! First it is necessary to select a reference (datum) from which all other measurements are made. I chose the straight line which is the bottom of the aft fuselage, and drew a line all the way forward and aft on it, and the LE of the wing as the fore/aft reference point. There is no need to trying to have a 0-incidence line, we are looking for a reference for construction. The bottom of the fuse on the A-10 is remarkably straight, and the LE of the wing is an easy transfer to the top view. By referring to the front and rear views, as well as some photographs, I decided to make the bottom of the fuse squared off, just like many of the other micros I've built, and to have the top of the fuse (which is also quite straight for much of its length) as a curved sheet. This would be light, strong, and simple to build.

On the side view I was able to mark off a top line which included only one change of angle, and that point corresponded nicely with what could become a hatch. This meant we would need a former at at least that location. I also wanted one at the LE and TE for mounting purposes, and one at the LE and TE of the stab and the front of the battery hatch up front. After locating these, a few more were added to keep things straight (or curved, as the case may be). Next, I translated these locations to the top view, and then drew rectangles that matched the outlines onto a sheet of paper. The rounding for the top side was copied off the front and rear views, and the curves for the formers between them were roughly interpolated. The fine fit would be handled by a sanding bar – these drawings only had to be “close enough.”
Jan 02, 2015, 01:37 PM
Hope to get out of life alive
kenh3497's Avatar
Add one more reader to the mix.. I have a LOT to learn!

Ken
Jan 02, 2015, 01:52 PM
AndyKunz's Avatar
Quote:
Originally Posted by BMatthews
but.... but.... by using the 3views and doing the things you're saying aren't you creating plans to work from?
SSHHHHHH!!!!! We don't want to scare them away! We're trying to create Scratch Builders here!

Andy
Jan 02, 2015, 03:17 PM
The "pro" in procrastination
Steve85's Avatar
Quote:
Originally Posted by AndyKunz
SSHHHHHH!!!!! We don't want to scare them away! We're trying to create Scratch Builders here!

Andy
Hee hee! This will be fun...

Steve
Jan 02, 2015, 03:23 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by Steve85
Hee hee! This will be fun...

Steve
Yep, a thumbs up from my side of the monitor as well. I hope my friendly smak talk mood came through clearly enough....

And let's not forget that not only is plagiarism allowed but it's encouraged. Take a proven design, change the outline tip shapes, sweep back or unsweep the fin and rudder, fatten or skinny up the fuselage and you have a whole new look.

And plans or no it helps to have a solid background of studying other plans so the builder has some idea of good and bad building practices. Otherwise sticking faithfully to someone's proven design has a lot to recommend it.
Jan 02, 2015, 03:25 PM
AndyKunz's Avatar
Most certainly, Bruce!

Andy
Jan 02, 2015, 03:28 PM
Registered User
LesUyeda's Avatar
"by using the 3views and doing the things you're saying aren't you creating plans to work from? "

I wasn't going to point that out, but since you did.:-)))))))))))))

Les


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