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Jan 01, 2014, 09:17 AM
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Scale Build-Off 3: 40" TBD-1 Devastator


This will be my first attempt at a build contest. Although I have used CAD several times to redraw and scale some of my scratchbuilds, I have not had any of them published or built by others. Therefore, I will consider myself an amateur.

The TBD-1 Devastator is most famous for its poor performance as a torpedo bomber at the battle for Midway Island in WWII. Nearly all of them were wiped out by Japanese fighters and AA fire during the battle. It is the plane flown by Ensign George Gay, the only survivor of his squadron. He was shot down and rescued after the battle was over. At the time it entered service in 1937 the Devastator was the most advanced airplane in the US Navy. It was the first Navy monoplane, the first airplane with a totally enclosed cockpit, the first all metal airplane, and the first with hydraulically folding wings. However, with the rapid advances in aircraft design of the time, the Devastator was quickly obsolete. After the battle of Midway, it was withdrawn from service. None survived the end of the war.

My design will be sport scale and is based on a FF plan found on The Plans Page. It was first published by Alan D. Booton in the August 1938 Air Trails.

I will go into more detail how I draw my plans in my next installment. Need to stop and get ready for Church.

Jim
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Jan 01, 2014, 09:30 AM
Big gov never Works
St. Martin's Avatar
Go, JIm!

Fuzz
Jan 01, 2014, 11:49 AM
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aymodeler's Avatar
Great topic for a build! I'm subscribed.

I always felt that the Devastators got a bit of a bad rap at Midway. They went in alone with no fighter cover and orders to hold formation and fly straight in on their targets. A recipe for suicide that would have resulted in horrific losses no mater what you were flying. Strict radio silence and limited knowledge of the exact position of the Japanese fleet prevented the kind of coordinated attack that would have given them a fighting chance.

But their sacrifice pulled all the Japanese attention (and fighter cover) down low and left the skies wide open for the dive bombers which turned out to be the true devastators of the Japanese fleet.

No doubt that the Devastator was outclassed by newer designs, but those planes and the incredibly brave pilots who flew them are true heroes that helped turn the course of the war! Sorry for the history lecture

Quote:
Originally Posted by JIMA
My design will be sport scale and is based on a FF plan found on The Plans Page. It was first published by Alan D. Booton in the August 1938 Air Trails.
What/where is "The Plans Page"?
Jan 01, 2014, 12:51 PM
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I would like to include my design process in the hopes that some others may see how easy it really is. Any one with some basic computer skills and some basic drafting skills can do this.

So to get started. Several months ago I lost my old computer. The monitor quit on me. Since the old computer is almost a decade old and hopelessly obsolete, I decided not to waste money on a monitor when I could just spend a little more and get a new laptop. The old computer was a desktop and I had been wanting a laptop anyway so that I could sit back in my recliner and design. On my old computer I had a free copy of Turbocad that I had learned to use and liked it quit well. When I went to download that free version to my new laptop, I found that it was no longer available. Now this was a problem because I did not have hundreds of dollars to buy a new cad program and I did not have the inclination to learn a new program. There were some other free programs on the net but all would require a large learning curve. So reluctantly I went to the Turbocad website and to my delight found they had a new 2d version for non-professionals like me at a very affordable price and that would be compatible to my new windows 8 laptop. At less than 50 bucks it was a no brainer for me so I instantly downloaded it. All this long story was to let you guys know that you don't need a ton of dough to get started in cad with a state of the art program.

Now I have a new computer, a new cad program, and an airplane plan chosen it is time to get started.

I start by downloading the plan to my computer. The plan is in pdf form and in several files. Turbocad can not use pdf files but can use .bmp files. To get from a pdf to a bmp I first print the file. Then I scan it back into my computer as a bmp file. While it is still in the scan program that came with my printer/copier, I take the time to crop the file to just the outlines of the plan. Once the files are cropped they are ready to be imported into a Turbocad file.

After starting a new Turbocad file, I import the bmp files by using the insert command and inserting the bmp files as objects. Once they are all inserted, I move them around until they are all lined up and I now have the original full plan visible on the screen and ready to start tracing.

The tools I use most often are layers, polyline, parallel line, perpendicular line, and snaps. With these tools you can draw almost the whole plan.

Now that I am ready to start drawing my own plan, I start by tracing the outlines of the plan I am using as a reference. You can do the same with a 3 view if you have all the ribs included. The first step to tracing is to create some layers. By tracing each section in different layers, you can work on each section or object over the top of another without altering the reference object. For example, I always like to work on fuselages first so I start by creating a new layer. Then I lock the first layer, on Turbocad it is the 0 layer. The 0 layer contains the plan that I imported. By locking the layer I prevent myself from accidentally changing it. By doing my tracing in another layer I am able to trace over the top of the plan without altering it. Later, I will make a layer for the fuse ribs, a layer for the stab, a layer for the wing, and a layer for the wing ribs.

Now I am ready to start tracing. The first thing I always draw is the centerline. Almost all of these old FF plans have a keel that runs down the center of the fuse on the side. The TBD is no exception. I start by zooming in real close to the front of the fuse at the center keel and start a line on the keel. I then draw the line all the way to the rear of the fuse and note the angle of the line. This is important because later I will need to know the angle of this line so that I can rotate my tracing to a perfect horizontal. I usually just type the angle off the side for later reference. The center line is also used to reference other lines later.

The next step is to trace all the outlines of the fuse. For this I use the polyline tool for drawing but the zoom tool is probably the most important. By zooming in and out of the drawing I can get more accurate with the lines. After the outline is drawn, I use the perpendicular line to mark where the fuse ribs will be by drawing perpendicular from the center line. I just draw one line to mark where they will be but do not draw the full width of the rib. That will be done after the drawing is scaled to the size I want to build. Once all the outlines of the fuse have been drawn, I then use the select tool to make a copy of my outline drawing and paste it outside the original plan. I will then use that copy to finalize the plan.

Next, all the rest of the plan needs to traced each part of the airplane on a different layer. The wing only needs to be traced on one side. Once the wing half is finished, cad can make a mirror copy of the half side to finish out the full wing.

Once all the outlines are traced, it is time to scale the plan to the size I want to build. For example, I want to build a 40" airplane but the plans were originally drawn at 26". To get to 40", I had to scale up the plan by the appropriate amount to reach my goal. I don't remember exactly how much that was but the math is easy to do. Divide 40 by 26 to get the amount to scale up the plan

Another thing to keep in mind is that the original plan was drawn on paper and then scanned to the website I downloaded it from. Over the years, this paper has shrunk with time plus the plans were drawn by hand. As a result the dimensions of the different parts may not match exactly. For example the fuse ribs may not be exactly the same length as drawn on the fuse outline. One of the steps I have developed to fix this problem is move the rib over the fuse plan and then edit it to fit the fuse outline.

Now I have reached the point in my description that matches the point where I am at on the current plan. I have all the outlines traced. I have filled in all the structure for the wing and mirror copied it and am now in the process of editing the wing ribs to match their positions on the wing. The plan for the TBD uses a very good looking semi-symmetrical airfoil. Some of these old FF plans do not. I will be using the airfoil as is in this design.

Now if someone can explain to me how I can take a screenshot of my progress I would like to add it as an attachment.


Jim
Jan 01, 2014, 12:53 PM
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www.theplanpage.com
Jan 01, 2014, 01:00 PM
71% of the world is runway . .
Bart83's Avatar
Nice subject , good luck and have fun !

Cheers,

Bart
Jan 01, 2014, 04:09 PM
Isaiah 40:31
rc capo's Avatar
Now if someone can explain to me how I can take a screenshot of my progress I would like to add it as an attachment.


Jim[/QUOTE]

I just googled it:

http://forums.turbocad.com/index.php?topic=1694.0

I work with photoshop, Illustator, and after effects alot. I google or Youtube a question.

You have inspired me to give tcad a go.

rc
Jan 01, 2014, 04:14 PM
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Download the free program "Jing" From Techsmith...http://www.techsmith.com/jing.html
You can screen capture, record and share - All free.,..
Jan 01, 2014, 08:24 PM
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Thanks guys.

I will have to give them a try.

While reading Dale's thread on his entry, I ran across his reference to some tutorial videos specifically on designing electric rc aircraft. I wish I had run across them years ago. So I will not be going into how to use Turbocad as that information is available on the videos. Instead, I will highlight the procedures I use in my design process.

Here is a link to Dale's build. https://www.rcgroups.com/forums/show...0#post27046788

Now, as soon as I can figure out how to get these screenshots working, I will load up a pic of my design.

Jim
Jan 01, 2014, 09:22 PM
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Here goes my first attempt at a screen capture using Ping.
Jan 01, 2014, 09:49 PM
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This is the extent of what I will post here for a while as I am still working on my Dauntless. Framed up most of the right wing half today before heading out to a birthday party for my oldest. She turned 25 today. Starting to feel like an old fart now. Saturday will be the start of Little League Basketball for my other off-spring. At thirteen she is still keeping me young at heart. So some of my time for the next couple months will be taken up coaching the team.

Jim
Jan 02, 2014, 12:46 AM
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D-Rock's Avatar
Hi Jim, great start on the Devastator. I also use Turbo CAD and trace the 3-views the same way. Any thoughts on power yet?

D-Rock
Jan 02, 2014, 10:58 AM
Übung macht den Meister..
Deuce's Avatar
While I have TurboCAD on both Windows and Mac, I use the Mac version most, and therefore am more familiar with it. This will be an interesting process to compare similar techniques on different platforms.

(For those not familiar with both T-CAD versions, despite sharing a name, the Win and Mac versions are two different programs.)

More to the point of the thread (well, sort of!), it is interesting to look into so many of the inter-war aircraft that, while state-of-the-art, were simply not equal to the task of the war that came. Also, how quickly the industry reacted to the new-found demands of "modern war," is just as fascinating.

James
Jan 03, 2014, 12:15 AM
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Bill Smudge's Avatar
I'll be keeping both eye's on this one Jim, should be quite interesting.

Certainly an aircraft that deserves all your efforts..


Bill


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