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Mar 21, 2018, 07:12 PM
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AleRRon's Avatar
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Van's Aircraft RV-4

Somehow somewhere I came across this small airplane described as "The all-around capabilities of the RV-4 are impressive. It is capable of excellent "sport" aerobatics. Several RV-4 pilots have successfully competed in organized aerobatic competitions, scoring well against specialty aerobatic airplanes."
Learn more at

Anyhow, I thought it looked pretty cool, and might be a fun flyer. Wing loading looked promising (large wings) and I just liked the lines. I am thinking of building a sem-scale foamie. The fuse would be a monobloc design pioneered by Tony years ago and proven to be a strong design. The wing would be a strut-reinforced full airfoil with ailerons so it would be a 4 channel bird. 40" wingspan. 2" wide monobloc from green Lowe's foam. Everything else from 6mm MPF.

I "built" one in Sketchup today to see how it would looks, and I have preliminary 2D plans. See attached pics of what it might look like. I am interested in feedback and ideas. I know that building scale models has downfalls and that sometimes certain mods are needed to make a good model flyer.

Let me know what you think!
Bob (Ale R Ron)
Last edited by AleRRon; Mar 21, 2018 at 07:25 PM. Reason: Added dimensions and materials
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Mar 21, 2018, 07:17 PM
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AleRRon's Avatar
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The real plane

Forgot to include pics of the real thing
Mar 21, 2018, 07:42 PM
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Whiskers's Avatar
I'd go up in size on the horizontal tail surface. In fact I'd make it as big as I could get away with and still preserve a nice semi-scale look.
Mar 21, 2018, 08:02 PM
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AleRRon's Avatar
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Whiskers, I'm sure I could. I've heard before that it can be necessary. Why is that? Is there some guideline or rule of thumb or principle about how large the tail surfaces need to be on models as opposed to actual full size planes?
Mar 21, 2018, 09:11 PM
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Whiskers's Avatar
It's all to do with scale effect.
One of my worst experiences in RC was doing an initial test flight of a true-scale model a friend had built.
This friend had built a full-size ultralight which flew just fine. The model, however, with it's little true scale horizontal tail surfaces was horrible to fly.
Actually on a reasonable amount of throttle it was OK, but when powered down, even moderately, it became uncontrollable.
So there I was, flying this guy's brand new plane and wondering how I could get it back on the ground undamaged.
In the end I brought it in under power to about 3 inches off the deck and cut the throttle. Fortunately it fell out of the air in a way that was satisfactory. Not pretty, but no damage.
Funny thing was that flight messed up my thumbs for quite a while. They had been educated to know that certain inputs delivered certain results. The chaos of dealing with such an unpredictable model made them quite confused.
Anyway, that was the last time that model flew. It became a static display piece.
Another one was built with nice size h-surfaces and it was a delight to fly.
Mar 22, 2018, 07:40 AM
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Whiskers's Avatar
Hmmm... I may have been deceived by the drawings above.
I've just had a good look at a 3V of the RV-4 and note that it's not too bad in regard to horizontal tail surface area.
It should be pretty good as is.
However, I don't think I could resist giving it a bit more cord and span. Just a bit...
Apr 05, 2018, 05:30 AM
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AleRRon's Avatar
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virtual model

I've been working on learning Sketchup, which is a very steep learning curve, and building this plane in virtual space before cutting foam. I figured it's a good skill to develop, and I can make sure it all fits correctly before actual building and avoid wasting foam. I thought it would save time in this way, but I think I have a good 40 hours in front of the computer so far. So much for computers saving humans time.

In any case, I attached some pics of what it would look like. There is an Xray as well that shows all the components including the internal monobloc, but not the electronics.

Soon, I'll start the cutting and building. I hope to post the cutting plans soon, but I have not built nor test this plane yet so cannot vouch for it's functionality until then. But if someone wants to try it out before it's been tested it might help.
Apr 06, 2018, 09:12 AM
Retired CAD guy
birdofplay's Avatar
While enjoying this thread,

I have discovered that the "BIG" Vans RV site has downloadable drawings
in DXF and DWG formats.
Not the best quality, but they are a a start.

Then ...
Outerzone also has some RV plans like the RV3 and RV-6 from old RCModeler mags.
PDF's without vector :<{
Without checking , I PRESUME that those surfaces have already been "adjusted"
for RC use and stability.

All this searching got me thinking ...
OK ok ok hang on ... I gotta recall what that was now ... ummmm errr

So I'm thinking or combining several methodologies.
1.) 3D Milling the Fuse halves from a block of extruded Foam. I got a new Toolpath program.
2.) Then Build the Wings from MPF/Depron Foam sheeting for lightness,
3.) and then adding Cheek Cowls that are 3D Printed, possibly the Canopy too.

Meanwhile I'll be looking for those cutting plans here ;>} !
Apr 06, 2018, 09:38 AM
Registered User
psychedvike's Avatar
Nice looking project. I'm always looking three projects ahead. I was thinking of a cosmic wind but this could be a better option. I will be following with great interest. Keep us in the loop. In the mean time I gotta get back to work on my Fokker E III so i can start on my Bee Gee and then maybe this one. By then you will have some of the bugs worked out for us. Thank for sharing you work.
Apr 07, 2018, 05:19 PM
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AleRRon's Avatar
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OK looks like I need some help here now. I created a 2D JPEG image of the components. I emailed it to Staples and asked them to print it out a according to the image size (36" x 48") with the aid of a 6" scale on one side. Unfortunately they cannot do it in a way to preserve the scale size of it. They can print the image, but it won't come out the right size. Sketchup is weird and not really set up to print anything. You can export an image, but not in a format that works well for printing. You're supposed to export the file to Layout, which is designed for printing. But I don't have Layout, nor am I going to buy it.

Can anyone help out? I can provide the Sketchup .skp file, or JPEG or PNG file if anyone knows how to convert that into something that can be printed full size or tiled.

I posted the 2D JPEG file

Apr 07, 2018, 06:44 PM
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AleRRon's Avatar
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Sketchup file
Apr 07, 2018, 09:10 PM
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Whiskers's Avatar
You can export the .skp file as a .jpg from within Sketchup.
When I right click on the image you posted I get the option to save it as a .jpg. Mind you, in this particular case that may stand for Jagged Pig-ugly Graphic.
Apr 07, 2018, 10:17 PM
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AleRRon's Avatar
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Right, that’s what I did and that’s what I got. I’m wondering if there someone out there in RC land who has Sketchup Pro and Layout and can create a proper PDF file of the cutting plan suitable for printing in high res. Or can take the skp file and use another program to generate a PDF.
Apr 08, 2018, 04:30 PM
Scratch building addict
rotagen's Avatar
I'm in the same boat now messing with sketchup making a plan for my new warbird. Managed to use layers and trace out a nice design, saved it in pdf and jpg or bmp. Jpg and bmp quality sucked. And there's no way to crop the output 2D graphic which is huge. And I don't/won't buy any expensive adobe product to crop it.

Here's how I finally got decent line quality, export as pdf with good settings which I forgot, make it big on your screen, (same size each time) take few screenshots, piece them together as a bmp or jpg on graphic software and crop, then size image using pixels per inch = dpi per inch....bit of a pain. Use online bmp to pdf converter, then you should be able to print tiles with cut marks etc.

Or even easier use good ol' "tileprint " (was 15 bucks made by an RC-er) to size objects in a jpg or bmp and print tiles.

Also theres a free pdf tile program which includes a "summary tile of your pdf. I used it but I found printing good matching margins was hard, in my hands adobe pdf reader printed better tiles with just the untiled image.
Apr 08, 2018, 04:55 PM
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AleRRon's Avatar
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You can export from Sketchup Make as JPEG TIF or PNG. First you have to pull in your image window because Sketchup will export whatever is showing on the window. Kind of like “print to screen” in Windows. I have a Mac. In any case, you pull in the side edges to match what you want to print. In my case I pulled in to the edges of the box I drew to hold all the cutouts. It was 36 x 48. 36” is the widest our Staples can print.
I then exported as a JPEG and emailed that to Staples and they printed it. But the printer needs a 1/2 “ margin, so the image printed 35” wide when in fact it should be 36” wide. Pretty close so I decided to take it and use it. I came home and redid it with a window width of 35” and may have Staples print that and it should be right

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