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YC-14 Build (From MikeysRC)
- Thread starter dezertdog
- Start date
Does the proxy above work for you?
dezertdog
Senior Member
I was looking through my build scrap to see if I had enough to make winglets and realized I had enough to rip up some tip extensions to make a dihedral wing. I've wanted to wrap my head around dihedral effect for a while ever since I heard Bixler talk about it in an older video. Better time than any I guess!
When I scaled up the fuselage 2" in width to accommodate the 1" foam I didn't extend the wingspan also. For a weight cost of ~45g these new tips will add an additional 8" bringing the total span to about 53" and should contribute to roll/slip stability. Seems like a no brainer to try, especially given what I'll learn making them.
From what I've learned so far I need to be careful that I don't end up creating a yaw-roll coupling or "dutch roll" behavior. I have no data on how they interact with a KFm3, or a specific understanding of how it will interact with my fuselage and overall design, but got I'm going to give it a shot and see how it comes out.
I'm thinking somewhere between 5-6 degrees of angle should be about right, but I'm working out figures in a few EDA calculators to back up my hunch.
Anyway here is the progress so far, all the bits to assemble the new tips so they match the KMf3 steps.
When I scaled up the fuselage 2" in width to accommodate the 1" foam I didn't extend the wingspan also. For a weight cost of ~45g these new tips will add an additional 8" bringing the total span to about 53" and should contribute to roll/slip stability. Seems like a no brainer to try, especially given what I'll learn making them.
From what I've learned so far I need to be careful that I don't end up creating a yaw-roll coupling or "dutch roll" behavior. I have no data on how they interact with a KFm3, or a specific understanding of how it will interact with my fuselage and overall design, but got I'm going to give it a shot and see how it comes out.
I'm thinking somewhere between 5-6 degrees of angle should be about right, but I'm working out figures in a few EDA calculators to back up my hunch.
Anyway here is the progress so far, all the bits to assemble the new tips so they match the KMf3 steps.
dezertdog
Senior Member
Funny - all this measurement, math etc I've been pouring over the last couple days to understand what I'm doing and in the end it's as simple as setting the table angle on the band saw and ripping it. About 30 seconds overall.
Here are the new tips mocked up, should be about 5.5 degrees. Next is fitting with the sander for a solid joint and triple checking symmetry, angles etc.
Man that thing needs a coat of paint! I like the new look already.
Here are the new tips mocked up, should be about 5.5 degrees. Next is fitting with the sander for a solid joint and triple checking symmetry, angles etc.
Man that thing needs a coat of paint! I like the new look already.
dezertdog
Senior Member
I'm sitting here looking at other planes, like the Bixler itself and those tips must be in that range easy. By my math 15% would require about a 1" rise at the tip. I'm going to mess with it for a bit here and see what feels right now that I'm getting used to a more extreme angle.
dezertdog
Senior Member
I bumped it up to 10 degrees, on such a large wing it looks less but I triple checked the math. I'm reading that it's a fine line on a wing with such a large aileron between good tendency and ending up with coupling effect so I think I'm going to stick with this for now. I can always split the bottom open with an x-acto and shim it up later if I want to go steeper, a bit harder to come back down.
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dezertdog
Senior Member
We're glued up, after final tweaking while glue was setting trying to match them exactly I ended up at 11 degrees. Now if I could remember where I put that darn power sander...
dezertdog
Senior Member
Finally found some time to wrap these tips up. I'll probably add a bit more glue and tape to beef the joint up since it's going to be primary contact for bad landings, but I'm pretty satisfied with the shape and symmetry at this point. The new 3S Turnigy showed up too (first flights were on a 2S, though the motors are rated up to 11v), so the next flight should give some pretty interesting results!
dezertdog
Senior Member
That went VERY well! Loving the new characteristics.
- More lift, easier hand launches, better low slow flight.
- Roll stability much increased, once I get the CG fine tuned it should fly hands off no problem.
- Slight yaw/roll coupling, turns are much easier to coordinate.
- Seems more stable flying at odd angles to the wind.
- Feels like it will fly inverted, need a bigger field to feel comfortable trying this. Under power 400' goes by pretty quick.
- Tip stall behavior seems very predictable, easy enough to recover even at low altitude.
- Seems to lose some roll stability with flaps down at low speed, flaps only for power takeoff now until I understand this more.
- 3S battery is what this thing wanted. Straight level flight at 1/4 stick, tons of power to spare to get out of tight spots.
- The CG moved back a little, which helps my pitch control. I can make a nice tight loop now!
- More lift, easier hand launches, better low slow flight.
- Roll stability much increased, once I get the CG fine tuned it should fly hands off no problem.
- Slight yaw/roll coupling, turns are much easier to coordinate.
- Seems more stable flying at odd angles to the wind.
- Feels like it will fly inverted, need a bigger field to feel comfortable trying this. Under power 400' goes by pretty quick.
- Tip stall behavior seems very predictable, easy enough to recover even at low altitude.
- Seems to lose some roll stability with flaps down at low speed, flaps only for power takeoff now until I understand this more.
- 3S battery is what this thing wanted. Straight level flight at 1/4 stick, tons of power to spare to get out of tight spots.
- The CG moved back a little, which helps my pitch control. I can make a nice tight loop now!
dezertdog
Senior Member
Also spent some time with the rattle can after today's re-maiden. Left the bottom surfaces bare for now, going to hit them with gray to give me some orientation.
View attachment 5107
View attachment 5107
dezertdog
Senior Member
Not quite done yet, the bottom is going to get a shot of gray and then I'll probably spruce it up with some yellow stripes like Mk I. Mostly the plane just couldn't be purple anymore, the wife has a thing against Purple and Gold.
As a side note to the painting, the Rust-Oleum Professional Enamel went on like a dream. Didn't eat the foam at all, made for some fast painting!
http://rustoleum.com/CBGProduct.asp?pid=95
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