Monday, February 1, 2010

Milled EPP “How To” & First Demo Plane w/It @ 5.5oz's w/Battery


“I wonder if anyone’s tried milling EPP?”

THAT was the very SECOND thing I thought when I first saw milled depron.

The FIRST thing I thought was…

“Wow – that’s a great idea! Take an already extremely fragile material and make it even more brittle! Nice!!!” :-)

Seriously – that was my 1st thought! :-)

That said – the idea of milling depron to lighten the overall load of the plane was indeed brilliant… a game changer for sure… if… IF you have the time… and the finances… to keep building plane after plane after plane… after smashing these now “hyper delicate” 3D machines. :-(

Being the preacher of EPP as the “budget conscience builders friend” :-) …I just had to give milling a try in EPP! A quick search online gave me nothing. I couldn’t find anyone else trying it. :-( So… I was on my own.

I gave it a shot – and came up with a plane design I liked to test it on - the Nikitis Animal.


Because I absolutely LOVE a fast roll rate – and the Animal is WAY quick that way! :-) This isn’t a post on the Animal though – so, for more info on that, please click HERE for a link to an RC Groups build thread on the Animal. NOTE: This is also the plane that won the 2005 ETOC! It’s a great plane! Devin McGrath (ETOC E-X Games winner 2006) was kind enough to answer my many questions on his a few years ago. You can see a picture of him “one hand” hovering his HERE (1st & last pictures on the page show him with the Animal) – and more pics of his Animal, including the setup he was flying it with HERE. And lastly on Devin, you can see him fly his Animal at the ETOC competition by clicking HERE (note, this may download the video directly to your computer depending on your computers settings).

Lastly on the Animal itself – let me mention that this was the also the plane that Scott Foster used to win the ETOC 2005 with… and… the plane that he used to introduce to the world the potential of airplanes with variable pitched props! Check him out flying it with a variable pitch prop by clicking HERE.

Ok, now on to milling EPP. First let me explain the tools. As you will see in the pictures below in a minute, I have a standard Dremel tool. Nothing fancy. It’s a setup my wife bought me years ago – before I was even into this hobby. It came with a few drills, sanders, etc. VERY basic. I think it was in the $30 or $40 dollar range at the time. So, that was what I had in my “shop” already to work with.

By adding just 3 parts to that basic Dremel tool… I was able to do the milling. Total cost was under $25 (not sure the costs now?) not counting the Dremel tool I already had.

THE THREE THINGS YOU NEED besides the Dremel.

FIRST – you need a “Dremel Multipurpose Cutting Kit, Item # 565.” I bought mine at Home Depo – though I’ve seen them at Lowe’s, WalMart, Target, etc. Pretty much anyplace that sells Dremel tools should have it. See picture below (double click on it or any of the pictures below, to make them bigger)

SECOND – you need a “Dremel High Speed Cutter, Item # 115.” You can purchase it at the same places I mentioned above.

THIRD – you need a small piece of Plexiglas. Buying full sheets of this is expensive… so I checked out my local Home Depo for scrap pieces – and they had a whole bin of them. So I picked this up, a piece plenty big enough – for only a couple dollars. NOTE: I only wanted mine to be about 7 inches – but if you intend on milling out spaces BIGGER than 7 inches – you will obviously need a bigger piece of Plexiglas than I’m using. The idea here is simply to use the Plexiglas to “extend” the base of Dremel Item # 565 (shown above) by gluing it to the Plexiglas.

So, note in the pictures below, that I cut the Plexiglas into a circle approx 7 inches in diameter. I did this by taking rough measurements then drilling a hole in the center. From there I traced a circle using a nail in the hole I just drilled attached to a string – attached to a pen! :-) Pretty “low tech” huh!?! :-)

I then cut out the circle with a coping saw and sanded down the edges to make them smooth – so it would be easier to work with – and not liable to “snag” the EPP while I’m working.

Next I used a Dremel bit to enlarge the hole in the center of the Plexiglas (where I’d originally drilled the hole in the center) so that it’d be large enough for…

a.) The bit to fit through (Dremel Item # 115)

b.) “EPP Dust” to pass through unhindered while milling! :-) Don’t want that to get balled up in there & melt! With the space I left for it to pass through, it worked fine. ZERO overheating! NO melting issues whatsoever!
  • PS – this might be a good time to mention – that ANYTIME you are working with fine dust particles… from pretty much ANY MANMADE product… you should wear a facemask  of some kind while you work!
Note the space for a & b above in the following picture.

NOTE: Don’t forget to sand / smooth off the edges of the hole you just enlarged in the center of the Plexiglas… before proceeding.

Next, glue the Plexiglas to Dremel Item # 565 as shown in the following pictures. NOTE: I used a flexible glue (“UHU Creative, Foam Safe” to be exact) so that I could remove it if I wanted to – but pretty much any glue that adheres to plastic should work just fine. If you are having trouble getting it to adhere, just rough up the surface where you’ll be gluing (on the surface of BOTH the Plexiglas & the Dremel Item #565) with some sandpaper. That usually does the trick.

Next, insert the cutter, Item # 115 into your Dremel tool – then screw it into Item #565. NOTE: You will have to unscrew the front “cap” (for lack of a better word) off of your Dremel tool – to expose the threading that is there. The pictures below show it better than I can explain it. So, take that “cap” off to expose the threads, then screw on Item # 565.

Now, notice in this picture below, how the bit is extending out below (or "above" in this picture) the surface of the Plexiglas. Obviously, the depth at which you have this protruding below the Plexiglas – is the depth of which you are going to REMOVE material / EPP. So, adjust this to whatever depth you choose to remove material. To adjust, simply use the adjustment knob (knob is on left in picture below) that is built into Item # 565.

Congratulations – you are now ready to mill some EPP! :-)

“But wait!” you say, “I don’t know how deep to go / how much material to take away / how much to leave – AND – I don’t have a pattern for my plane!?!”

Good questions – for sure!

Well, on the depth question first. Honestly… I can’t answer that – as, first of all, I don’t know what depth / thickness EPP you are using! :-) Secondly, I don’t know the density of the EPP you are working with. Yes, I could tell you the density & the thickness of what I’m using – but in my opinion, that would probably only lead you astray – and here’s why…

I’ve purchased EPP from a variety of vendors (the ones I recommend are listed in the right column of this blog) and one thing I’ve noticed is that each vendor’s density & thicknesses… are slightly different. They are almost ALWAYS different from other vendors – but, often times slightly different from batches I’ve ordered from the same vendor too. So… for me to get super precise on depth / me telling you to remove or leave “X Amount” – would be foolish of me… as the batch of EPP you are working with… is virtually guaranteed to be different from mine.

Don’t fret though! :-)
This is still VERY doable for you!

Simply take some scrap pieces of EPP that you have on hand / THE SAME BATCH YOU ARE GOING TO BUILD / MILL FROM – and experiment a little – to see how much material you can remove / how thin you can go… and still have enough thickness / “skin” left to hold the milled sections together. You want it as thin as possible / you want them light (that is the point here after all!) but you don’t want it to end up so thin that they tear to easily! :-( Experiment a bit – and you’ll quickly discover a depth that you are comfortable with. Try it – and you’ll see that its really a straightforward process.

So on the “How deep should I mill it?” question – that’s my answer.

Now, on making a pattern for your plane / templates as to what material to mill away & what material to leave the “full thickness” of the EPP… now that’s a tough one! :-)

Honestly, this was by far the most time consuming part of the build for me – making the templates! First off, let me show you what I came up with, and then I’ll try to explain how I made them.

First, obviously, I needed to get plans for the plane I wanted to build / mill. I had previously traced out plans off of a Nikitis Animal – so I was all set with that. If you need plans – I don’t have any for the Animal that I can email legally. But, there are plenty of sites online where you can download free plans for a variety of other planes (see links for some such sites in the right hand column of this blog).

Once I had plans, I made a 2nd set of plans and started experimenting with how I was going to remove as much material as possible… yet still leave myself enough structure to support / maintain the shape of the plane.

I poured over many MANY pictures of depron planes that had been milled for idea’s… looking to “discover” the strategies that they had employed. My thinking went this way – “Since depron is way WAY more brittle than EPP – then a strategy that works for depron milling (where to leave the depron full thickness & where to mill it out) should work brilliantly in EPP!”  Or… so my thinking went! :-) And, it seems to have worked out well. :-)

Here is a picture of the fuse and the way I drew it out. I’d measured everything out and then shaded with pencil the parts to REMOVE / to mill out. I then went through with an exacto knife and cut out all the parts of the template that would be milled out in EPP. In the following picture you can see the shaded area’s yet to be cut out – and the top already cut out.

Notice in the following picture the many MANY lines I drew out. I had everything measured very precisely – so as to be sure to ALWAYS have at least “X” amount of structure left over / full thickness of EPP to “frame out” that piece.

How much “structure” did I leave? Again, I can’t answer that – as it’ll depend on both the thickness & the density of the EPP you are using. You are going to have to experiment with that & decide it based on the exact foam you are working with.

So yeah - this step took allot of playing around to get it worked out – but, it was well worth it! And, I now have plans for this plane – and I can build em rather quickly now that the plans are done – as the milling itself goes very VERY quickly!  Just “sink” the bit into the foam, and then move it back & forth within the space you are milling – kinda like you’d mow a lawn… back & forth across the space till it’s done.


Now – a couple comments about the airbrakes… and how I milled those.

Below are several close-up shots of the templates I made for my air brakes. Now… I’m very much still experimenting with air brake designs – so I’m in no way “pushing these” as the best or anything… I’m simply showing you how I did what I did – and showing you the exact air brakes as used on the plane in the pics & video.

You’ll notice that I used a foam board material to make the template (rest of the plane’s template is made out of “3 for a $1” poster board at the Dollar Store!) for these air brakes. The reason I did that was because I wanted to be able to make it so that it’d fit together like a puzzle (note the A:A, B:B, a:a, b:b, matching system) so that everything would be precise / both brakes identical left & right. The entire thing put together makes up the SIZE of the brake. Take out the middle 2 pieces (see picture below) and that space that is now “missing” is the space that gets milled.

The holes in the air brakes template? Those get removed ENTIRELY !!! See picture below of the finished Air Brakes to see how the holes go all the way through the milled out section.


FIRST – trace out the template for your air brakes / the outside shape
SECOND – trace the 6 circles / “holes” that will go all the way through the EPP
THIRD – trace the inside “milled shape” (by removing the 2 removable center pieces)
FOURTH – “drill” / mill ALL THE WAY THROUGH the EPP / make the holes now (if you wait & do it later, you’ll rip the EPP. :-(
FIFTH – mill out the center 2 area’s (the space in the template that is removable) 

See the above finished air brakes.

The “pins” you see sticking out of the air brakes (in a couple of those pictures) I made from really REALLY small pieces of Carbon Fiber – with a small piece of tape at the top (so I can get a grip on em). I use these as pins – so that I can take the air brakes on & off the ailerons. I did this for 2 reasons. One, because I wasn’t sure if I’d like them on / how the plane flew with them on! So I didn’t want to “commit” to them by gluing them down! :-) Turns out this concern was unfounded – as it flies GREAT with them on! Wouldn’t want to fly it without them now! :-) The second reason to have them removable though – is the weight of them. If you leave your plane sitting around for a length of time… the extra weight of the ailerons (with the air brakes on them) starts to bend them down… because the weight is so far back behind the hinge line. This is NOT a problem in flight – as the brakes themselves “pull” the ailerons to “center point” during flight. But, have them sitting in your hobby room… and they’ll pull the ailerons down. :-( So, I made them removable to alleviate this problem – a problem I’d discovered while experimenting with air brakes on other EPP planes I’ve built.

Now, having said all that about making them removable – another option storage wise is simply to hang your planes by the prop. The air brakes aren’t on the plane in the following picture – but, you can see how I’ve simply hung my plane from the ceiling of my hobby room.

Well, that’s about it. I’m sure many of you out there will have all kinds of questions for me. Please DO write & ask! I love interacting on this stuff. If I don’t know the answer – I’ll tell you – as some of you are WAY beyond me / way more technical on things than I am. But, if there is some way I can help, I want to. After all - that’s why I bother writing all this down on this blog! :-)

Have fun - and please send me pics of any planes you build in EPP and mill out!

Oh - and be sure to watch the video of this plane (click HERE or view at the top of this page) and comment on it on YouTube.

Thanks, I look forward to hearing from you.