Hey guys, I've been looking around at different ARFs and Scratchbuild plans and i'm unsure as to which is the best? I realize that the question is quite subjective but I'd love to get some input and experienced opinion on the matter. I would prefer that it be a scratchbuild but let me know what you think. The end goal is to have the slowest possible/ most stable plane that is able to carry a gopro.
Another question I have as to aerodynamics is this: Is building a bigger wing in comparison to the fuselage the key to the slowfly effect? For example, would it be a good idea to use the same wing as the fowl flyer with a small tubular fuselage?
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Thread: The Best/Most Stable Slowflyer?
03-11-2013, 12:46 AM #1
- Join Date
- Jan 2013
The Best/Most Stable Slowflyer?
03-11-2013, 12:53 AM #2
For stability, use a fair bit of dihedral in your design. That is, the wings tilt upwards from where they meet the fuselage towards the tips, making like a V shape when seen from the front.RR5 Alien 5" - KISS FC · KISS 24A ESC · Lumenier 2206 2350kv · HQ 5x4x3 · HS1177 · Unify Pro · X4R-SB · Lumenier 1300mAh 4S 60C
03-11-2013, 01:01 AM #3
Look at the flitetest nutball."If at first you don't succeed, skydiving is not for you"
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03-11-2013, 01:23 AM #4
You said it - this is a VERY subjective question.
In my opinion, if you are looking for a stable, slow flying airplane capable of carrying a GoPro, then the Bixler/Sky Surfer can't be beat. It is inexpensive, durable and has fantastic flight characteristics.
Think efficiency for your application in terms of aerodynamics. What is an efficient wing to meet your requirements? Two of the most important parameters from this standpoint are wing loading and aspect ratio. Wing loading is simply the weight of the aircraft and payload divided by wing area. Aspect ratio is the ratio of the wing length to wing chord (width from leading edge to trailing edge).
Slow flying airplanes typically have low wing loading and high aspect ratios. This equates to long, narrow wings. So, does this mean that longer is better? No, at least not to a point. At some point, the structural requirements of a looooong wing "outweigh" the wing loading requirement. Your question is, "what is the optimal wing design for a slow flying, stable aircraft capable of carrying a GoPro?" Um, I don't know.... There are more parameters to consider.
What flight times are you looking for? What size batteries are going to give you those flight times? That will impact wing loading and fuselage size.
What airfoil are you using? This is an often overlooked parameter of a scratch built RC aircraft. Most scratchbuilt RC planes use either a Clark Y airfoil or some type of KF airfoil. Both work, but neither is ideal for flight duration. Plus, the Clark Y creates a strong, pitch down moment requiring either a longer fuselage or larger horizontal stabilizer than possibly necessary. Now, I've been called an "Airfoil Diva," and many will argue the finer points of the necessity of airfoil design.
Now that I've said all that, think long, thin wings. You can taper them from the wing root to tip or just use a constant wing chord. A wingspan of 1400mm to 1800mm will work nicely for carrying a GoPro at a stable, slow speed. Think wing loading in the neighborhood of 10 to 12 ounces per square foot. Not sure what airfoil I'd go with, off the top of my head. Something close to but not quite symmetrical.
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03-11-2013, 01:29 AM #5
I'm not sure the nutball would give the best GoPro video. I have had great success capturing video from the Fogey, and it is definitely slow if you want it to be. I found extending the nose about an inch & a half and adding about 2.5 inches of height to the stabilizer smoothed it out great. Because I am cheap and use the HK wing cam I have two mounts inside of the fuse, one at 45 deg and one at 90 where the lens pokes out through a little hole.
I had to cut grooves in the nose for the tabs on the pod because the added length brings them up further but, for a two dollar plane, who cares. I also forgo wheels when I use the 45 position. I have thought about building up a little mount to get the camera over the prop for a level shot, but I received the Bixler so to heck with that. I have a couple of videos under the Fogey scratchbuild thread that can give you an idea of how slow she goes.
03-11-2013, 01:36 AM #6
Lol, I just looked at the Fogey thread myself, not only have you built it, you have gopro video from it, I'll shut up now. Listen to earthsciteach, he's by far smarter than me.
03-11-2013, 06:09 AM #7
03-11-2013, 08:01 AM #8
- Join Date
- Jan 2013
Thanks guys for the insight, especially you earthsciteach! So I'm not totally sure what the airfoil design I went with is called (or even if it has a name) but it is very similar to the one laid out in the Fowl Flyer Scratchbuild. The wing is 60" long with a slight dihedral. My next question is this: What kind of angle should I have the wing at? (angle of attack?) Based on the what you can see from my picture, what do you recommend for a fuselage? Hopefully my picture doesn't reveal some fatal flaw in my design thus far.. haha.
Thanks again, I really appreciate the wealth of knowledge on here!
03-11-2013, 11:54 AM #9
- Join Date
- Sep 2011
- Ponce de Leon, Florida, United States
My most stable slow flyer, was actually a much larger version of the Old Fogey. It had a very large under cambered wing, and flew hands off perfectly. Too perfectly.
One time during a maiden test of the design, I decided to try doing a loop. As I reached the top of the loop, the now upside down plane, which had no strap for the battery, decided it didn't need the battery any more, and dropped it. The plane remained inverted, and slowly descended, still upside down, towards a patch of woods. When I had caught up to it, I found it, resting unharmed, upside down, in the one clearing in this wooded area. It was my best "hands off" flyer ever.Have you checked out FT Groups yet? The local group for my part of Florida can be found here... http://ftgroups.com/group/45
03-11-2013, 04:05 PM #10
- Join Date
- Feb 2013
I just saw your post and I wanted also something really stable, I have therefore built this one .. which is very stable in the air. should have little near ten hours to build. and the result says it even and this is a good slowflyer as wel..
there no go pro yet..but this is the goal..
Last edited by Anthemius; 03-11-2013 at 04:10 PM.