Insulating Foam? Is that too weird or what?


New member
So.... I'm not entirely sure if I'm in the right spot to post this (Mods, if it needs to be moved, I get it), but I did a couple searches and it looks like I'm definitely not in the common group for designs.

I'm not much of a tech-heavy designer. In fact, I'm about as green as it gets with anything you throw in the air with the hopes that it lands soft enough to throw again.

But I wanted to start somewhere, and I started with solid foam. I remember having those styrofoam gliders everyone had as a kid that you'd throw hard enough to make it do a loop before crashing. But they were light, and cheap, and I loved it. Flite Test has a ton of great ideas with particle board and power and electronics, but I'm really bad at detailed designs, and can't do any computer based plans at all.

So I decided to try insulating foam, cut with razor blades/etc.

For my first (current) design, I went with a PBY Catalina. I know it's nuts to try that first, but I might do 1 engine, I might do 2, no idea yet, I haven't picked my electronics quite so soon. I picked the PBY because at first I thought it would be the easiest wing - and a parasol wing is really smooth and stable.

plane outline.jpg

The foam I used is the $4 hardware store special - a sheet of 48 inch by 24 inch. I cut the basic outline of the plane, then cut additional outlines of the smaller parts of the body and the wings.

After that, I just hand trimmed until it looked right, glued everything with hot glue, then hit it all with a 220 grit sanding block until it was smoother and I could actually get the shape of the wings to look right.

Oh, I should mention I did used to work in a guitar factory in the finish dept - sanding it something I can do better than cutting or measuring, so I depended on that a lot more than I probably should have. Eh, it's a first attempt, I'm not expecting it to be perfect.

For the skin, I was told that a 50/50 mix (I was closer to 30/70 I think) of Elmer's white glue and water was all I needed (I pulled the idea from a youtube video for a guy who did this to pre-made foam gliders), with carpenter's/painters brown paper soaked in that in strips and applied as the skin. It did dry very well, light and solid, so I think it'll work.

plane with skin.jpg

Here's where I'm at now. I need to trim the control surfaces and figure out what electronics I'm going to use. It's really light, roughly under a lb, and it's got a 48 inch wingspan. If anyone has ideas for what power I'll need, etc., let me know. I'm thinking of using the engines as rudder instead of added another control surface back there. Is that something that works well with two engines?


New member
As far as I can tell (I don't have a good scale, just a bathroom one so I have to stand on it holding it), somewhere around 1 lb. Right now it's really tail-heavy, which should be expected since there's no motors/battery/etc yet. As I was applying the skin, it was about twice as heavy (or felt that way), but as soon as it dried out it was really very light.
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New member
Make sure to put a decent amount of power on it, and share your results. I used paper and thinned glue to reinforce my radian, so I know how scarily heavy it is before the water evaporates. :)
Power as a minimum should be 100 watts per pound! As a minimum! Just thought id repeat that. For this bird you may want 2 motors of around 150-180 watts each or a single 250-300 watt (could go more), both could be run on a 3S 2200mah. As for rudder control, you are better off with a physical control in stead of differential thrust as it gives better authority.
Oh and looks awesome btw. here in oz we struggle with building materials so I use wall insulation to great effect. just cut it out, sand it and cover. fly great and and take a hit when crashed! Good luck with this one!
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Old and Bold RC PILOT
P Factor could still be a problem on take off so I would definitely recommend a functional rudder just in case.

The use of differential thrust alone could give an aircraft that will turn rapidly in one direction and barely in the other during take off runs where you need all of the thrust that you can muster.


I like 3D printers...
Cool man. I like PBY's. If it's really about a pound a coupke A pack motors would do the trick. OR you could go a bit bigger with an F pack size.

I have plans out for a 57" foam PBY and it flew great with F pack motors. C pack is probably a bit large. I built a 100" version of my PBY at Flite Fest this year and used 2 c pack equivalent motors. It flew great with differential thrust.

Use counter rotating props and it will turn great in either direction with differential thrust and p factor will not be an issue.

Check out this thread:


New member
For the moment I'm on hold - budget isn't there for electronics yet. However, I did go buy a bunch of paperboard sheets, so I decided to try a one-day build to try to make something just as big (roughly). I wanted to make something that I could pull the motor/etc out and reuse once I crash the PBY. First time with paperboard, so I'm happy.

IMG_20161105_213626.jpg IMG_20161105_213647.jpg

Some of the things this build has that the PBY didn't (that I had to add later):
Control surfaces (no having to cut them out of the wings/etc., YAY!)
Bay for battery/electronics (again, no having to cut).
Hollow, with 2- spar upper and 1 spar lower wings.
Landing gear (well, pontoons, but you know).
Upper wings are canted up and to the sides - should make it more stable on roll and level flight.

Wingspan is 5 feet! It's wider than the PBY. However, I'm worried I cut the fuselage a bit short and that the tail's surface will be less effective.
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New member
So I've been doing a ton of foam board gliders to get used to it. I found that by putting a small hook (like a 3m wall hanger) on the bottom of the nose, I can put a looped string on that and have my friends' kids run with it to get it in the air - once they stop running, it glides back down. So far, I've done 8-10 versions of different gliders with various results, but it's a great way to figure out what designs I do like before actually going back to a powered option.

plane 1.jpg


New member
It also means anything i screw up has no consequences, since there's nothing but foam board to destroy, and it's amazing how much kids love running with these things.