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Alternate Material Experiment

#1
I fly where there is a lot of dew, and I fly first thing in the morning. My brown Tiny Trainer was warping because there is a limit to the waterproofness of untreated brown foamboard. I built a new Tiny Trainer fuselage and a whole Mini Mustang out of 5mm styrene foam with no paper on it. It was difficult to get the parts to go together the same way as with the paper. I put packing tape where the paper would be and it mostly worked ok. The planes fly fantastic. The Mini Mustang is an incredible flier, except for when I am crashing it. It has taught me so much, as did the Tiny Trainer before it. This just swoops through the air begging for aerobatics.

My experience with building the kit Mini Mustang, and building this one from scratch tells me that simply painting the brown foamboard may be a better way to avoid the water problems. Still, this was a good experiment and a great flying experience as well.
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Merv

Well-known member
#2
Great looking plane.
I cover all of my planes with colored packing tape. Quick, easy, cheap & fairly water proof. I get my tape from Tape Planet or Hobby King they both have a good selection of colors.
 
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Brett_N

Well-known member
#3
x2 on the packing tape. Even in Arizona, our fields are wet in the morning.

Amazon has an 8-pack of multiple colors for like $20 - it's 2mils thick and works fine.

for reinforcing I've been using 2.7mil clear along with fiber reinforced.
 
#9
Here's my mix-and-match design I call the Krait. It has a wing with 3D printed ribs and film covering mated to a DTFB fuselage and tail feathers with the paper stripped off and replaced with colored tape. The taped foam weighs very slightly less than the ordinary paper covered foam and significantly less than any painting or water proofing scheme you might apply over the DTFB paper. The tape/foam combo is waterproof because there is no paper. I think it's not quite as strong/stiff as the paper covered foam, but almost. It doesn't seem to "get tired" after long term use like the paper covered foam does. Using tape and a few basic covering techniques borrowed from the way you use Monokote it's easy to cover and seal component edges. Edges are where most trouble starts when using paper covered foam, especially where moisture is involved.

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#11
@Mozella - love the wing (and the plane) - question, what is the LE construction for the wing?

Phil
Actually I changed the wing construction from when this photo was taken. This wing is WAY too strong and a bit heavier than necessary. It had a 3D printed LE with a D tube made from 1/6" x 1" balsa curved over the ribs, old school balsa style. But it was fiddly and no fun.

Now I"m using only a single arrow shaft spar plus a short aft spar to prevent wing rotation. It only goes outboard to the first rib. The new wing is tapered too.

The leading edge is a small 3D printed "D tube". It's solid with 100% infill. The aft edge only about 5mm in height. The LE is curved of course. I printed it in two parts since the half-span is 550mm and my build plate is 300mm. The aft edge of this D tube has a span-wise slot 2mm deep designed to take a flat carbon fiber strip measuring 4mmx1mm. The strip is half submerged in the D tube. The forward part of a typical rib is about 5mm in height to match the D tube and each rib has a 2mm deep slot so that the ribs engage that leading edge carbon fiber strip. The trailing edge is similar but the D tube is replaced with a trapazoid. The technique is a good one. The arrow shaft spar is cheap and light if you shop for the "bendy" versions.
The spar along with the leading edge components make aligning the ribs easy. I printed what I thought was the minimum required full sized ribs along with a half rib in between which goes from the leading edge only back to the spar.

Ailerons are tape covered DTFB.
 
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#13
Here you can see the new version of the tapered, lighter wings. The fuselage is the same. I think only the mid-bay diagonal brace would be sufficient and that three aren't really needed. The bottom of the wing is covered in black and white checker board film and you can just see some of the design where it wraps around the leading edge. Don't think those dark spots are carbon fiber.

You can also just barely see the diagonal stiffener on the DTFB aileron. It's a 1mmx4mm carbon fiber strip inlet into the bottom. I strip the paper from the top and put tape on that side only. Then I cut a slit on the other side using a carpet knife with the blade extended just far enough to cut the paper and and almost all the way through the foam. Next I strip the paper and run a small flat blade screw driver up and down the slit to turn it into a 1mm wide slot suitable for the carbon fiber strip. I glue that in, and then cover that side with tape.

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#15
Now that the photo is on the Internet and has gone to India and back, the diagional stiffener on the aileron is not visable as it is on the photo I have here at home. Trust me, it's there and I hope the text will give everyone an idea of how I installed it.