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Old 12-01-2012, 06:17 PM   #1
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Default Biplane!

I'm kind of designing this as I go along:



The wings are 7 1/4" x 30", ailerons on the bottom only.

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Old 12-01-2012, 10:48 PM   #2
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Best of luck!

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Old 12-02-2012, 12:54 AM   #3
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Originally Posted by mclarkson View Post
Best of luck!
Thanks

Progress on the fuselage:




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Old 12-02-2012, 12:57 AM   #4
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I'm a big proponent of the "design as you go" method, particularly if using dollar tree foam or depron. If it looks like it should fly, it will fly. That usually holds true.

All of my landings are three point landings if you count the spinner, too
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Old 12-02-2012, 10:08 PM   #5
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Close up of the main landing gear from the underside:



... and a plywood reinforcement for the tail skid:



I'm planning on having the wire tail skid extend up into the edge of the rudder, then down through that piece of plywood (as someone here suggested). The free-pivoting one on plane #4 is not ideal for ground handling - hopefully this will work better.

Fuselage covered with tape, being inspected by my assistant Wayne:



Next up the wing struts and servo installation, then I can glue on the lower wing.

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Old 12-03-2012, 12:20 AM   #6
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And more

Gluing the fuselage to the lower wing:



Whilst setting up to do this I discovered that the tail end of the fuse points off to one side half an inch or so (measure twice and cut once and all that...). I decided that the tail planes will just have to be off to one side a bit, but still parallel to the center line. Let's not tell anyone, OK?

I then set up in a similar way to stick on the upper wing:



Not shown, I added some gussets from the struts to the underside of the wing, but essentially it's just a hot glue butt joint from the wood struts to the packing tape surface. Think that will do it? Or should I add some pins down through the top of the wing? I've still got the inter-plane struts to add, you know...

I like the way it's looking! Especially those big fat tires I picked up at a swap meet somewhere



Need a "pilot" head to glue on the top there...

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Old 12-03-2012, 05:35 PM   #7
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Stopped at the Goodwill store to see if I could find a pilot - got a little carried away:



I think I'll go with the dog in the middle. He kinda looks like he's flying

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Old 12-04-2012, 12:17 AM   #8
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Imbedding the tail skid in the rudder:



Finished vertical stab / rudder w/tailskid:



And here's the whole thing so far:



It's supposed to rain all day tomorrow but be fairly nice Wednesday. Shooting for maiden flight then

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Old 12-04-2012, 01:12 PM   #9
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That really looks nice, and went together fast.
Nice job.
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Old 12-04-2012, 10:14 PM   #10
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Originally Posted by pd1 View Post
That really looks nice, and went together fast.
Nice job.
Thanks! I'm having a lot of fun with this foam core stuff

We're ready for the maiden flight, hopefully tomorrow:





I hope it doesn't spend much time in that first pose!

Weighs in at 15.65 oz with no battery. Taxi tests out in the yard show excellent ground handling - I can actually make it go where I want it to .


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Old 12-05-2012, 10:47 PM   #11
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It flies!

It was really too windy for the maiden flight of a 1 lb foamie, but I did it anyway. I held up my pocket anemometer for a while and was getting about 8 - 12 mph and a gust of 20 mph . But the direction was good...

It flew great, considering the wind. Can't wait to try it on a calm day .

The ground handling thing is fantastic! I'm able to land it way down the field and taxi back - this is a new thing for me!

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Old 12-05-2012, 11:40 PM   #12
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Glad it flew well.

Paul
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Old 12-06-2012, 12:36 AM   #13
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very nice! how did you tuck away the landing gear inside thefuse?
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Old 12-06-2012, 04:25 AM   #14
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Congrats! I laughed at your collection of potential pilots. (I have a boxful myself. )

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Old 04-24-2013, 11:15 PM   #15
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I'm revisiting this basic design . The original is still flying, and people seem to like seeing it, but frankly it's kind of a dog in the air. With those narrow ailerons only on the bottom wing, it has little aileron authority. And the rather blunt leading edges of the KF wings + all those interplane struts make a lot of drag, which make it slow.

So, using my new hot wire cutting ability I'm making a new biplane! So far I've got the wings done and the sides of the fuselage cut out. Gluing wood longerons to the sides in the picture:



Instead of struts in the middle I'm going to do a solid block of foam shaped like cockpit windows, streamlined, and then just two outboard struts instead of those Z shape things. I expect that will cut the drag quite a bit. It's going to be a "stagger wing", with the upper one set an inch back from the lower.


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Old 04-27-2013, 11:31 PM   #16
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The bits and pieces so far, just stacked on top of each other:



I'm not going to do any interplane struts at all - shooting for fast

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Old 04-28-2013, 06:15 PM   #17
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Your 'cabin biplane' layout should work fine. We had a similar kit with regular top wing in front stagger around in England for years that was well regarded and I once did a similar layout to yours, with back-stagger, that flew fine.

I don't think you've got such a massive power to weight ratio that she'll need interplane struts

Hate to be a boring old fuddy-duddy, but it looks much nicer with a 'proper' wing section Doesn't need a 'pilot' either...

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Old 04-29-2013, 12:15 AM   #18
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I like everything about the "proper" wing section versus the KF version; looks better, and more importantly, it performs better .

With the big wide cockpit section to provide a lot of purchase for the wing/fuselage glue joint, the interplane struts are completely unnecessary.

Dereck, what's this similar one you're thinking of?

Here it is so far:



Yes, the landing gear is a lot taller than it needs to be. I got lazy and salvaged it from an earlier plane .

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Old 05-05-2013, 12:54 AM   #19
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OK, all the control surfaces work; ready for the motor & final fiddly bits, then the maiden flight, currently scheduled for Tuesday morning


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Old 05-05-2013, 02:11 AM   #20
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Looks a bit odd, but nothing that looks like it won't work.
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Old 05-05-2013, 03:05 AM   #21
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Cool looking plane. The colors are perfect!
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Old 05-05-2013, 09:30 AM   #22
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Originally Posted by dgjessing View Post
I like everything about the "proper" wing section versus the KF version; looks better, and more importantly, it performs better .
I'm with you there. I've got myself into a few heated discussions with KF fans on the merits (or lack of) of the KF airfoil. For me the only merits are simplicity and speed of build, end of story.

I ended up building a KF wing for my Elf discus launch glider to prove the point one way or another. Average flight time went from 61 seconds with the standard wing to 37 seconds with the KF wing. And it stalled pretty much like any other wing disproving the 'un-stallable' claims often made. Case closed I think.
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Old 05-06-2013, 05:38 AM   #23
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No such thing as a wing that won't stall.

You can limit power and control throws to make it very hard(er) to stall the main wing before the elevator lacks authority to hold the nose up.
The Ercoupe (full scale) used this method to make the aircraft "safe" for people learning to fly. (it almost made it safe for a beginner...)
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Old 05-06-2013, 05:45 AM   #24
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Originally Posted by fhhuber View Post
No such thing as a wing that won't stall.
I know that, you know that, but try telling the KF fans that
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Old 05-06-2013, 06:11 PM   #25
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After looking up the KF airfoils... selection of which of the many "stepped" airfoils would make a huge difference in what speed range the wing would be good for.

I played with something that was almost a variation on the theme... They can work. they all will have limited speed ranges for efficiency partly based on step sizes.

In a way it could be said that you can't stall the KF airfoils with the steps on top... because its already stalled. That's a pretty inefficient way to try to glide. The 1, (paper airplane typical) 2 or 5A might work out ok for some sailplanes... I'd want power for all the rest.
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