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Old Mar 05, 2013, 12:00 PM
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Germany, NRW, Lünen
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3D-Foamy Pitts with some changes

Hi,I'm a bloody beginner in scratchbuilding, but I´ll show you my first scratchbuild planes. First I build an indoor shocky. Pilot is my son. I use EPP colored in black for this. You see it on the right.

But I'm a real big fan of biplanes like a Pitts. So I found the plan at 3D-Foamy.com and build 2 versions of this real nice airplane in 7 mm EPP. On the left you see the indoor Pitts. Span is 90cm. Weight is 400 gr. Powered with 2S 600 Lipo. Enough for 5 Minutes flights. I do some changes in the plan so I doubled the Wings on top in the first 1/3 and sanded the leading edge.


Without colors...

The shocky...




Now I build a new Pitts for outdoor flying. Using the same shape in 110 % (span 100cm). I made wings with a NACA Profile and covered the ribs with 5mm EPP. I use 4mm carbon tubes to stif the wings. This seams a little to thin. Next time I'll use 6 mm. The fuselage is 25 mm EPP and 10 mm EPP. The weight is now 800 gr and I powered the plane with 3S 2200 Lipo an Aeolian 2826 brushless motor. Prop is 9x5. Today was the maiden. Sorry, no video, because I was so nervous. But after some trim it flights real great. Some quicker as the indoor version. I built in 3-4 degrees thrust to the right in the firewall but this is not enough. I think 5-6 degrees is better. But I gave some klicks right on the rudder and I`ll test it a little more before I make some changes at the firewall.
3D flight is inpossible with this motor. But rolls, loops, turns, even like a real plane is possible.









This is how I made the Wings:



I use UHU-POR hinges. This is a special contact adhesive.

Greats Peter
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Old Mar 07, 2013, 12:53 PM
This is kid stuff.
Mazzepa1's Avatar
USA, AR, Harrison
Joined Aug 2010
745 Posts
Impressive

Kyrill,

I congratulate you on an excellent looking Pitts. Glad to hear that it flew well. I continue to notice the preference of EPP as building material by modelers from Europe. EPP has some very desirable characteristics, but finish is not one of them, IMHO.
That being said, your result is more esthetically pleasing than most EPP planes I've seen. Rather than me listing questions , would you care to elaborate on your finishing techniques?
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Old Mar 07, 2013, 01:17 PM
12th Pursuit Squadron
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Garland, Tx.
Joined Mar 2002
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Very nice aircraft, thank you for sharing with us.

J.P.
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Old Mar 07, 2013, 02:47 PM
This is kid stuff.
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USA, AR, Harrison
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Originally Posted by TheAeronut View Post
Very nice aircraft, thank you for sharing with us.

J.P.
I get down to Murphy every now & again and I'd be interested in seeing what y'all are up to. 12th Pursuit Squadron, combat flying perhaps?
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Old Mar 07, 2013, 06:59 PM
12th Pursuit Squadron
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Garland, Tx.
Joined Mar 2002
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I haven't flown combat in a couple of years, although I have one or two friends twisting my arm to get back in. Cash (CashRC) prefers scale, but I mostly flew SSC. These last few years have been mostly foamy planes and most recently sheet foamy stuff.

Holler when you are down this way. I am in the NorthEast corner of Garland, so Murphy is just a few miles up the road.

J.P.
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Old Mar 08, 2013, 01:29 AM
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Originally Posted by Mazzepa1 View Post
Kyrill,

I congratulate you on an excellent looking Pitts. Glad to hear that it flew well. I continue to notice the preference of EPP as building material by modelers from Europe. EPP has some very desirable characteristics, but finish is not one of them, IMHO.
That being said, your result is more esthetically pleasing than most EPP planes I've seen. Rather than me listing questions , would you care to elaborate on your finishing techniques?
Of course I'll do:

You are right! EPP finish is not very good to get a scale looking model. But if its in the air nobody can see the finish details! Possible is to iron it with low temp and a paper between EPP and electric iron. EPP is stable up to 110 degrees. The great advantage over depron is the flexibility. If you have a hard landing or a crash in the air with another plane mostly there is no damage. (Indoor flight, combat etc.)

I've got some EPP blocks for free!. 127 x 40x 7 cm. It is black EPP. (dark grey)
I use a Band saw to cut it not a hot wire.
My bandsaw is able to cut a high up to 15 cm.
So I tiled the Blocks in some 15 cm wide parts.
Now I'm able to saw the EPP in every thickness I wish.
Sanding the surface is not necessary after sawing. Only the edge of Wings etc. to get it in round shape.
Up to 10 mm I cut the shapes with a new cutter knife. At right angles with a ruler I made out of a piece of wood (20 mm).
I cut one rib of plywood and cut the other ribs of EPP around the plywood one with the cutter knife.
I colored the Airplane with silver paint before glueing everything together.
I mask it with sticky tape and brush it with a normal spray can (for cars etc)
While using Nylon hinges at rudder and elevator. The ailerons became spezial UHU-POR hinges.
For that I use sticky tape to prepare a line of 1 mm at the wingside and the aileronside of the hinges. Exactly at that point this parts come together. Than put the UHU-POR glue on all this lines where you can see the EPP between the sticky tape. Directly after that stripping the tape and let the glue dry for 20 minutes. Than press the ailerons and the wings together for a short time. Thats all. You need no more stripping tape at the upper or lower side of the wings, so there are no problems with the painting.

Regards Peter
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Old Mar 08, 2013, 03:05 PM
This is kid stuff.
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Originally Posted by TheAeronut View Post
I haven't flown combat in a couple of years, although I have one or two friends twisting my arm to get back in. Cash (CashRC) prefers scale, but I mostly flew SSC. These last few years have been mostly foamy planes and most recently sheet foamy stuff.

Holler when you are down this way. I am in the NorthEast corner of Garland, so Murphy is just a few miles up the road.

J.P.
Don't be too surprised if you hear from me about the middle of May.

Stephen
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Old Mar 08, 2013, 04:12 PM
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Kyrill,

Thank you for the information. I am learning to utilize EPP for construction, just finished a PZL P11c kit from here:
http://napolskimniebie.pl/ I didn't get the wing shape quite right, but overall I was quite pleased with the result. During this exercise I became familiar with using an iron to smooth and shape EPP after cutting/sanding. A very useful technique.

Of particular interest is to hear that none of your EPP was cut by hot wire. The EPP I've worked with so far exhibits surface irregularities that I ascribe to difference in density between the walls and interior of the individual cells. My guess is that the lower density interior melts away from the heat source further resulting in a slight depression in each cell. No matter the cause, this "roughness" makes it difficult for me to get a good seal along the edge of masking tape to get a nice, sharp line.
So then, does your mechanically cut EPP present a more even surface than hot wire, or laser cut EPP? Also, you enjoy the advantage of being able to cut whatever thicknesses you desire, I'm envious of that.

The airfoil you chose has an unusually sharp leading edge. Does that feature impart any particular characteristic in flight? Just for efficient wind penetration, perhaps? The flat bottom leads me to ask how well the plane flies inverted?

UHU/POR seems to be similar to a contact adhesive we use quite a bit for EPP joining, Welder glue. It also makes a very good hinge, all I do is butt the 2 pieces together, run a thin bead of Welder along the joint, then squegee the bead to a very thin layer along the joint. Walk away until it dries and viola, a tough, very flexible hinge. It will take paint quite well, which is good because if you don't paint it, it will yellow after some exposure to sunlight.

Halten Sie fliegen.
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Old Mar 09, 2013, 02:28 AM
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Originally Posted by Mazzepa1 View Post
Kyrill,

The airfoil you chose has an unusually sharp leading edge. Does that feature impart any particular characteristic in flight? Just for efficient wind penetration, perhaps? The flat bottom leads me to ask how well the plane flies inverted?
That is not right! I've sanded the edge to the normal shape of the foil. The picture I show ist to explain the EPP layers at the edge before sanding it.

I flew the plain now for three times. Last time there was 4-5 bft wind. So the plane came up against the wind and came up suddenly to vertical flight. Hoovering first time 2 meters above the floor with full throttle. I used a few seconds to became it to horizontal flight. The motor thrust is up to 800 gram the planewight is also arround 800 gram. Then I use 3/4 up to full throttle to fly against the wind. Its a better slow or parkflyer I think not für wind like that.
I can't say anthing about inverted flying. I used the time for trim and some landing experience. Aerobatic will come later.
I have not installed some crosswires between the Wings, I think its better to do that before practice some hard aerobatic figures.

So long Peter
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Old Mar 12, 2013, 11:28 PM
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Originally Posted by Kyrill View Post
That is not right! I've sanded the edge to the normal shape of the foil. The picture I show ist to explain the EPP layers at the edge before sanding it.

I flew the plain now for three times. Last time there was 4-5 bft wind. So the plane came up against the wind and came up suddenly to vertical flight. Hoovering first time 2 meters above the floor with full throttle. I used a few seconds to became it to horizontal flight. The motor thrust is up to 800 gram the planewight is also arround 800 gram. Then I use 3/4 up to full throttle to fly against the wind. Its a better slow or parkflyer I think not für wind like that.
I can't say anthing about inverted flying. I used the time for trim and some landing experience. Aerobatic will come later.
I have not installed some crosswires between the Wings, I think its better to do that before practice some hard aerobatic figures.

So long Peter
I was referring to the final rounded shape of the original image not the lines drawn on to show the material as bonded before shaping.

Quite right, I'm getting the cart ahead of the horse. Too early in the process for fancy aerobatics.

Please do keep is up to date as you develop the Pitts.
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