Hippogriff
New member
Or: Everybody's got these cool new biplanes, and I'm just here like
This all came about because the Explorer's wing is by default the exact length of my backseat, which makes transporting a little dicey with regard to closing the doors. So my dad suggested, as a joke, that I make it a biplane. Then I took him seriously, and this happened.
Pictured at the top is actually attempt number one, which was ruined by adhesion promoter when I tried to paint it. Attempt two suffered a catastrophic crash in high wind, and I didn't get a picture of it before crashing. So I'll take a picture of that once I put it back together.
Attempt number one is made with the spare trainer wings from two kits. The upper wings are cut down nine inches on each side, and the lower are cut down ten. The tape on the wings covers the polyhedral allowances.
This is the inside of the upper wing, showing modifications for servo allowances; measurements are from center line.
This is the inside of the lower wing; the two holes in the bottom surface are where the ski hardpoints tab into. The hardpoints are made of 4" sections of leftover strut, with an inch and a quarter between the tabs, so it sits on either side of the spar. This then gets a hole about 3/4" from the front and about in the middle vertically, where it pins into the ski itself.
Here's the design for the first edition of the skis. The original location of the mounting hole is marked there; after taxi tests where the Explorer's thrust angle proved tricky, the proper hole should be 3" from the rear, instead of 3" from the front.
This is what it looks like folded and glued - again, with the hole too far forwards. With a bit of tape on the bottom, these will work just fine on solid surfaces. However, they'll bog down hard in snow.
On this version, I maintained removability with some plastic tubing and a dowel. There's an extra control horn on the top wing, and then one on the bottom, where the top wing servo controls both ailerons. This saves me some wiring holes in the bottom of the plane. The bottom wing also had a platform on the top, built from some assorted small scraps, which keeps the bottom wing from rotating.
I have a video of the first version in the air; it wasn't my best flying, considering I accidentally trimmed the darn thing for additional up instead of down. Given that, it actually handled okay. It was just a little weird, considering it's very long for a biplane. Much as I'd have liked to make a new tail with a bigger surface, I didn't have the surplus waterproof foam.
The plane is a wee bit less stable and it seems to have a higher stall speed. I'm presently running a C-pack, 4s battery, and an 8*4.5 prop, temporarily absent a reverse 9*6.
That would have been about it, and I'd be posting a picture of everything painted. But, after hearing from plastic modelers about how adhesion promoter really helps, I tried some. Don't know if it was the temperature from my paints having gotten cold, or whether it was the stuff itself, but the promoter soaked straight through the waterproof paper and bubbled it right off, such that I no longer trusted the wings structurally. Fortunately, when I ordered my C-pack, I also got an extra Explorer kit while it was on sale. So, time to go at it again, but with a slightly different design goal: get the entire biplane conversion out of parts that were in the kit. The only things you need extra are a couple of mini control horns and linkage stoppers, plus some extra BBQ skewer. I also noticed that on rough landings, the bottom wing would go askew, so that had to be fixed, the tubing in the cabane struts was already pulling out of the foam, and the skis that bogged down in snow needed to be fixed. No all-together pic yet, gotta fix it up for that first.
After I get repairs done in the next couple days, I'll take a proper picture, and post a bit more on processes.
This all came about because the Explorer's wing is by default the exact length of my backseat, which makes transporting a little dicey with regard to closing the doors. So my dad suggested, as a joke, that I make it a biplane. Then I took him seriously, and this happened.
Pictured at the top is actually attempt number one, which was ruined by adhesion promoter when I tried to paint it. Attempt two suffered a catastrophic crash in high wind, and I didn't get a picture of it before crashing. So I'll take a picture of that once I put it back together.
Attempt number one is made with the spare trainer wings from two kits. The upper wings are cut down nine inches on each side, and the lower are cut down ten. The tape on the wings covers the polyhedral allowances.
This is the inside of the upper wing, showing modifications for servo allowances; measurements are from center line.
This is the inside of the lower wing; the two holes in the bottom surface are where the ski hardpoints tab into. The hardpoints are made of 4" sections of leftover strut, with an inch and a quarter between the tabs, so it sits on either side of the spar. This then gets a hole about 3/4" from the front and about in the middle vertically, where it pins into the ski itself.
Here's the design for the first edition of the skis. The original location of the mounting hole is marked there; after taxi tests where the Explorer's thrust angle proved tricky, the proper hole should be 3" from the rear, instead of 3" from the front.
This is what it looks like folded and glued - again, with the hole too far forwards. With a bit of tape on the bottom, these will work just fine on solid surfaces. However, they'll bog down hard in snow.
On this version, I maintained removability with some plastic tubing and a dowel. There's an extra control horn on the top wing, and then one on the bottom, where the top wing servo controls both ailerons. This saves me some wiring holes in the bottom of the plane. The bottom wing also had a platform on the top, built from some assorted small scraps, which keeps the bottom wing from rotating.
I have a video of the first version in the air; it wasn't my best flying, considering I accidentally trimmed the darn thing for additional up instead of down. Given that, it actually handled okay. It was just a little weird, considering it's very long for a biplane. Much as I'd have liked to make a new tail with a bigger surface, I didn't have the surplus waterproof foam.
The plane is a wee bit less stable and it seems to have a higher stall speed. I'm presently running a C-pack, 4s battery, and an 8*4.5 prop, temporarily absent a reverse 9*6.
That would have been about it, and I'd be posting a picture of everything painted. But, after hearing from plastic modelers about how adhesion promoter really helps, I tried some. Don't know if it was the temperature from my paints having gotten cold, or whether it was the stuff itself, but the promoter soaked straight through the waterproof paper and bubbled it right off, such that I no longer trusted the wings structurally. Fortunately, when I ordered my C-pack, I also got an extra Explorer kit while it was on sale. So, time to go at it again, but with a slightly different design goal: get the entire biplane conversion out of parts that were in the kit. The only things you need extra are a couple of mini control horns and linkage stoppers, plus some extra BBQ skewer. I also noticed that on rough landings, the bottom wing would go askew, so that had to be fixed, the tubing in the cabane struts was already pulling out of the foam, and the skis that bogged down in snow needed to be fixed. No all-together pic yet, gotta fix it up for that first.
After I get repairs done in the next couple days, I'll take a proper picture, and post a bit more on processes.
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