New Technology - Building Foam Airplanes

Written by Lucas Weakley
Using Foam to Build Airplanes
As seen in the Summer 2018 issue of
Park Pilot


One of the questions I am asked the most from my videos and articles is, “What foam do you use for your builds?”

Although I could go into all of the science about how these foams are manufactured and formulated, in this article I want to discuss my experiences with the foams that I’ve used and, hopefully, give you some ideas for your projects. I also want to share my current go-to foam for building my new airplanes. Let’s get started!

Believe it or not, the foam I used to build my first airplane was Depron (depronfoam.com). This turned out to be fortunate because Depron is easy to work with. It cuts well with a sharp X-Acto knife and it’s easy to tape, sand, and glue.

Depron is a trademarked brand of closed-cell extruded polystyrene that is sold as wall insulation and flooring substrate. Depron is also marketed for arts projects and RC modeling. There’s even a variety of Depron that is specifically manufactured for RC use called Depron Aero.

I like this foam. Its stiffness means you rarely need spars or stiffeners. In most cases, the foam forms nicely with a bit of heat, and it’s waterproof because there are no coverings. Sheets come in large sizes with tolerance thicknesses.

This tolerance comes at a price, though. Depron is usually several dollars per sheet. A box of the stuff can set you back a couple hundred dollars! Although this is expensive, any airplane you build out of Depron will have a long life and great performance characteristics. For some, that justifies the costs.

Another foam I experimented with in my early days was BlueCor. Also known as small-cell Styrofoam, this insulation foam was manufactured by Dow and was an extruded polystyrene foam, like Depron. It was waterproof and less stiff than Depron, but easy to cut and sand. It was great for wire-cutting wings and carving out fuselages. It was often used in building full-scale, moldless, composite, experimental airplanes because of its superior strength-to-weight ratio.

A similar foam by Dow, called UtilityFit, is available from Lowe’s (lowes.com). It is sold in 4 x 8-foot sheets that are 2 inches thick. Dow (dow.com) also manufactures UtilityFit in thicknesses of 1, 11/2, and 3 inches.



This RCPowers F-18 (rcpowers.net) is made from 6 mm white Depron foam. The airplane is rock-solid and incredibly lightweight. Lucas expects it to last for many flying days.


I built several airplanes from sheets of BlueCor when it was available. I sanded airfoils, shaped full fuselages, and even built a scale Cessna 152 from this material. It was also useful to keep around when I needed a thicker structural piece of material or I had to embed a servo into a part of my airplane. It was also sold in a folded, perforated form that was as thin as hobby sheet foam.

Arguably the most popular foam for park flyers is Dollar Tree (dollartree.com) foam board. Also known as Readi-Board, this is a polystyrene foam sheet with paper backing manufactured by R.L. Adam’s Plastics (goadams.com).

The paper gives the thin foam board a lot of rigidity and allows the builder to easily decorate the airplane without worrying about melting the foam. Most of the airplanes I own are made of Readi-Board. I use this foam and have recommended it in both my Maker Hangar series (https://bit.ly/2HcUcl8) and YouTube videos (https://bit.ly/2F4JoQ2).

Readi-Board is extremely easy to cut. By removing the paper on one side, it can bend around curves to create complex shapes. What probably makes this foam so popular is its price and availability. Sold at Dollar Tree for $1 per sheet, Readi-Board is easy to source. The cost of airplanes you build with Readi-Board is usually small, and for this reason I would routinely clear out my local Dollar Tree’s stock of the stuff for my ongoing projects.

Although this foam is convenient, it has some drawbacks. The sheet size is only 20 x 30 inches, which is small for many of my designs. The paper backing is also not glued to the foam, so over time, with exposure to humidity and flight stresses, the paper will begin to delaminate.



The Cessna 152, constructed a few years back, was entirely built from BluCor foam, except for the tail, which was made from Readi-Board. Photo by Max Weakley.


This often meant that I needed to rebuild the aircraft after only a few flights at my humid Florida RC flying fields. This can be prevented by coating the foam with wood varnish and a sealer, but this adds unnecessary complexity to simple park flyers.

The foam is also not very precise. The thickness and flatness of the material varies considerably among the sheets that I own, which has become an issue in my most recent builds. I still think Readi-Board is great foam from which to build airplanes. It’s perfect for beginners and seasoned hobbyists alike.

More recently, I’ve been going back to uncoated foam sheets for my new airplane designs. The one I’m using now is Fli-Power Value XPS RC Model Foam (fli-power.com). The sheets are made of expanded polystyrene (do you see a trend here?) and sold in a box of 16 2-foot x 4-foot x 6 mm sheets. You can buy it through a variety of websites, but the box will only set you back approximately $50.

The foam is weatherproof, easy to form, and less rigid than Depron, but more flexible. You can use Value XPS to fold airfoil shapes by adding a layer of tape to support the leading edge curve during bending. (The tape can be removed when the foam is glued in place.) The sheets are also precise and have a large format, which is how I was able to make the modular fuselage of my Buster test airplane and the shaped wing of my Atlatl Glider.



Lucas recommends building his Maker Trainer 2 design (makezine.com/2014/07/25/maker-hangar-2-07-maker-trainer-2-build) with Readi-Board because it’s easy to use. This airplane was specifically designed around the size of the foam sheets.


I’m not supported by this company, but I can’t recommend its foam enough. I feel like the cost is well worth it for the quality, and I plan to do many more projects with it.

I’m sure I’ll find some more types of foam to experiment with in the future. I plan to start building some composite RC airplanes soon, but that’s a story for another time.

I hope you got something out of this column. Let me know if I missed one of your favorite foams. Until then, see you in the sky!






17 comments

Interesting article, but I thought you would like to know you missed a foam board product that has been around since 2012. Model Plane Foam is also made by Adams. Fly power is essentially the same as MPF. RC Foam approached Adams to sell it packaged for them after the exclusive period we had established with Adam's had passed. The difference is I sort through each box and cull out imperfect sheets, am able to squeeze 17 sheets in almost every box and recently reduced the price to $40/ box for A grade. A rougher surface version is available for $30/ box for guys building "disposable" planes or those that will be shaped and sanded. Here is the whole story of the product and company: https://www.rcgroups.com/forums/showthread.php?1533245-Model-Plane-Foam-... I think you will find shipping from MI to FL will be less than from CO as well.

Flite Test and I’m sure others sell a foam board that has brown paper covering. It’s not waterproof but more water resistant than the Dollar Tree foam.
Thank for your informative article on the subject.
Cheers

Grey type on a white background is difficult to see, or read. Please, stop trying to reinvent the wheel. Use black type.

I can not believe you totally left this group out of your post. They are 100% dedicated to building with Foam core board.
https://www.flitetest.com/

MPF, Model Plane Foam is manufactured just for models, and emphasis is placed on flatness, and thickness consistency. It is slightly more flexible than Depron, so handles impact better, especially in the cold.

It is WAY cheaper than Depron, which has lost its usefulness since the "new" Depron is no longer flat, and dimensionally consistent.

Search for "MPF" on the world wide web.

Thanks for the info.

thanks

What is the most popular glue used to make these foamies?

Hot Glue is mostly used, but PVA types of White Glue. I often use White Gorilla Glue or Elmer's Wood Glue with great results. I live in a HOT climate (Arizona), and Hot Glue isn't always the best solution. :)

I too have not monitary
Ever since the withdraw of Depron from the market I have been using MPF.
It IS a USA made product and developed by modelers for modelers.
How could anyone NOT support it use. Buy American !
http://www.modelplanefoam.com/

Value XPS appears to be extremely similar if not exactly the same material.
Size, boxing and price point make my conclusion credible.

Regardless, I use MPF exclusively in my offerings.

What ever small curvature it may be delivered with can easily be overcome by
designing the parts layouts to be symmetrical.
That makes curves Cancel each other out and keeps the Smoothest side
on the Visible parts of the model.

I have found other so called "Depron" offerings to be more difficult to work with and less sand-able if not down right "cheesy" in it's makeup.

Regardless, Foam is cheap enough for anyone to make up their own mind.

So that my 2 cents

Bob @ Hoosier Cutout Service

Depron is no longer available.

This article is out dated. I read it hoping for some good news on foam availability. No good news. Pretty worthless.

Now that Depron is no longer being shipped to the USA, this article is outdated and may even confuse people. I don't know of any comparable product to Depron that is available in the thinner sizes, like 3mm or 2mm sheet.
Model Plane Foam is the closest substitute, along with the fan fold insulation that it basically comes from, but its currently only available in 6mm thick, unless you are able to hot wire cut sheets down to the lighter thicknesses.

Hello,
Why doesn't the article mention MPF - Model Plan Foam? It has a nice thickness consistency and comes in 24" X 48" sheets. I really like it. Available at http://www.modelplanefoam.com/
Thank you!

Enjoy a Blessed Day
Michael W Hetrick
AMA# 67381

great

I would like to build a foam plane but how do you find out what electronics ,motor ,servos ect.

I built balsa control-line stunt planes for many years and have an instinctual need to build a nice looking airplane. I love working with MPF! It cuts smoothly, sands beautifully, is sturdy, straight, and works great with Gorilla White glue. Paint it with Apple Barrel water based paint from wally world, thinned 50% with water and brushed on. Amazing stuff.

I have a source for the old Bluecor Fanfold.
I am trying to see if there is still interest in using for RC planes.

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