RC Airplane Project

I was asked some questions about my project in a filament thread so I thought, hey just start a project thread!

First off I am using SketchUp make. You can get it here if you want. http://www.sketchup.com/download. When you download you get the full blown “pro” tool but at the end of the 30 day trial period they grey out some menu items and you get the free version. I found it a great and intuitive CAD tool. It only takes hours to get fairly good at it (but of course, I learn new stuff and get better and faster everyday) It has some limitations and gothca’s with 3d printing but for a free tool it is pretty awesome!

The goal of the project is 5 foot wing span STOL type aircraft (Short Take Off/Landing). I am loosely modeling off a Cessna 170.

So off course with a 5 foot span and using a Taz 6 we are going to have to build up sub-assemblies to make a whole.

Wing first:
Since the Taz 6 print bed is 10.8 inches square I am working so that pieces are never more than 10.5 inch. That includes a 1/2 overlap for locking on span wise part . So finished assemblies will be 10 inches.

The main wing has just 5 unique parts: Arrayed here for Printing:

Here is an exploded view of the 5 parts showing how they will assemble:

So 7 parts to make a 10 inch section. (two sets of ribs needed) An assembled section:

Now finally we take the sections and connect them:

That’s the theory! Now for reality.

So the short version of this story is it works. These shots are all of V1. The long version is that if you refer to the exploded view I used tight tolerance tab and slot assembly style here plus many intricate interlocking aspects to make it strong.

I have really struggled with getting the parts to fit. I have experienced a learning curve on parts accuracy issues detailed in other threads (Here: https://forum.lulzbot.com/t/bad-accuracy-of-finished-parts/4315/1 and here: https://forum.lulzbot.com/t/filament-tolerances/4318/1 if you care) So Version two Wing is being drawn now and is going to simplify over all intricacy and move away from tab and slot.

This is a very interesting project.
I’m looking forward to see your version 2 wing design.
I’ve been using Sketchup Pro for several years.
If I have Sketchup questions, using Pro gets me answers from the Sketchup people.
If I have trouble with getting my models solid, I scale them up x10 or so, make them solid and
check them with Solid Inspector.
This is the 1st time I’m in User’s Gallery, I’ll stop back from time to time.

LOL! That was one of the very gotch’as I was referring too above. I learned that one the hard way!

I am robajohn on the SketchUp forums as well as here. Are you on there? If so you are NOT GJG there.

I meant to answer your questions from the other thread as well and I got side tracked!

Oh, me and $20 words! It’s just a fancy word for “where parts touch”

I plan to use flanges like this: (but no rivets! :slight_smile: ) Where it says “Fay Seal” make that “Fay Glue”

Don’t know if you saw this -

FliteTest reviews the 3D Lab Print’s P38 model


LOL! Well, yes and no! That model comes from 3dlabprint.com and I saw that guy doing a P-47 build on youtube a couple of months ago.

and THAT is exactly why I have a printer now! LOL!

For those of you not all into airplanes you can see where the ailerons fit in to the picture…
So in the contentious battle of strength to weight ratio I got all crazy in designing the aileron skins which would be significant portion of the strength while having as little weight there as possible. I think I over did but my OCD really loves all the curves! :slight_smile: So first I drew the skins and end pieces:

The skin is 10 inches by 6 inches. I drew this to be a little ‘androgynous’ So here you can see EITHER and left and right set OR I can splice the left and right and make a single 20 X 6 inch aileron.

Try not to waste too much print bed! :slight_smile: I bought a TAZ 6 for the size after all! :wink:

All the aileron parts printed out:

And assembled, it come out at 2.99 ounces for a 10x6 inch piece. I am pretty happy with this number!

Your aileron parts look good.
For an airplane of the size you are building, less than 100 grams per aileron is very light weight.

I don’t think I’m GJG on the Sketchup forum - I think I went there today for the 1st time.
Now I know what a Faying Surface is.

Nice design. Are you planning to cover with monokote or something else? Electric?

Yes! Ultracote in my case but I will try not to get tooooo RC nerd on the Printer forum! :slight_smile:

Absolutely! I sold all my old Nitro motors and converted to all electric in 2012 and I have never regretted it once. In, fact I am not sure this wing would hold up to the sharp vibrations of a nitro engine? I mean I could make it do so but electric just makes everything better with the possible exception of your plane does not get lighter as the flight goes on! :wink: (on the other hand your center of gravity does not change as fuel burns off)


Sorry, it seems I set off the alarm there!

On Electric -

Nor do you have to clean the oil off of everything when you are done…


Roger that! “Just say No to slimers!” :slight_smile:

I agree, electric is nicer in many ways. I wouldn’t have thought of printing a frame and covering it like that. Cool idea!

Well the guy mentioned above is selling his STL’s where you print the skin too. I am just not ready for that level of CAD yet plus covering just has to be soooo much lighter. Well, and I bought one of his planes and he includes special .ini files for Cura that frankly, I am not ready to play with yet. I may post those later and see if more experience users can tell me what it is doing?

Now factor in that what I really wanted was a laser cutter- you would just cut thin flat wood pieces to these shapes and build the structure up from them. The cost of laser cutters just won’t come down though so I switched to printing which just keeps getting better and cheaper. Of course, printing gives me another axis to work with and I love that but I think I am still “thinking” 2D when I design. I do plan to grow into the 3 rd. dimension gradually though! :wink:

I completed the redesign of the wing parts to eliminate a lot of the intricate interlocking I had of the parts before. Now I am just counting on good old fashioned glue. Well and some 5 MM carbon Fiber rods. :wink:

Here are all the distinct parts that will make up the wing. Not many distinct parts but the parts on the right will repeat many times!

We are concentrating on the center wing tonight. It is the toughest part strength wise and print wise as it will be the where the wing and body tie together…
This is the Center wing Leading edge. For me, this was the trickiest print I have done to date as every single side is open. I printed a single layer under the top lightening holes then I cut that single layer out with an exacto blade. It has to be tough as all wing forces will concentrate here. Note the mounting lugs.
Here is everything needed to assemble the center wing section printed out;
The three ribs and two spars glued together
Then the leading edge glued to the main spar. The Carbon Fiber rods are not glued into their grooves yet. They are just for show at this point. but they are coming and will be key!

That’s coming along nicely. Any flap or slat action planned on the leading or trailing edges?

LOL! you are such a mind reader! That is one of the reasons why I did this more like a kit instead of wing sections printed with the skin already on.

I am going to do a version one with simple flaps/ailerons.

Once I confirm it will fly and hold together I will build another wing, the back 2/3’s of which wont change except for flap tracks versus simple flaps. However, the front third will will get movable slats up front. BWUH HUH HUH!
Mt first balsa scratch built project folded a wing on the first flight…

So I am going to make sure this one project will fly before I get fancy and print all the linkages that will make this move!

I plan to print version 2 of that blue plane as well!

Love that Taz6! That is 60 inches of trailing edge spar in one print!

I am in retail and I worked all through Christmas in case the Servers/databases crashed. I got a 3 day weekend for news years though and I got a lot finished.

First, I showed you the aileron construction on the last page. Now we are going to do the flaps. in case you are not a fellow airplane nut here is where flaps fit in the scheme of things!
So As you will recall I made a right and left aileron but I also had plans to join them and make bigger ailerons OR flap. So here is a right and left unit and I simply glue them together using the control horns as a splice.
I thought this was pretty brilliant when I first drew it up. distinct parts make all the wing control surfaces but in the end it’s just gluing parts together. I mean, duh, no big deal.

Here is two 20 X 6 inch flaps and 2 10X6 ailerons ready to go.

So here is the heavy lifting- main wing assembly! There is LOT printing that went on here, check out that pile of parts! :slight_smile:
First I put the main and trailing edge spars together with the 5 mm carbon fibre rods I purchased. Then I started putting the back ribs into trailing edge spar… You can see both spars with the CF rods here and the beginning of the ribs…
Then I snapped the other end of the ribs into the main spar then glued them. So here is the center third of the wing…
It was getting late so I did not get to do the front third yet So there is still a good bit of that pile of parts left! : ) Here is the back two thirds of a 68 inch span wing though

I am still drawing the body. I finished the wing this weekend and started covering. Here are the results of a little experimentation.

We had several conversations at the flying field about weather iron on covering would stick and whether ironing it on would melt PLA.

As to sticking yes and no, depends on the brand of covering. I stayed 50 degrees below extrusion temps on the final shrink.

It came out looking really good though! (IMHO) I ordered a couple of rolls of covering so next weekend I will tackle the whole wing!