Flight B/C

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joshdaposh
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Re: Flight B/C

Post by joshdaposh »

bjt4888 wrote: November 13th, 2022, 5:25 pm
joshdaposh wrote: November 13th, 2022, 10:59 am Hello, I have questions about my Wright Stuff Plane (I have built it using the Freedom Flight Models kit).

1. What really makes the difference between a 1-3 ranking national-level plane and a 4-10 ranking national-level plane? Is it how the plane is built? I doubt it because of the size limitations and most of the teams competing have won at the state level anyway to prove that they are competitive... Is it intricate little additions or removals? Or is it that the 1-3 place planes just had more winds in them?
2. I'm having trouble understanding how to trim my broad flaring-style propellor from Ikara. I heard that people sand it and trim it using small cuts but where...how... From testing it on my FFM plane, I noticed that my plane just dives straight down which probably means my propellor is way too heavy.
3. If a plane has a slow climb at the beginning of the flight will it have a slow descent on the way down? Is there a quick way to test the descent of your plane without having to fully wind it and see it climb and wait a couple of minutes for it to come back down?
4. How do we know which rubber thickness is going to maximize our performance? I've heard that thicker rubbers provide more power but fewer winds than thinner rubber. Wouldn't the obvious choice be to use a thin rubber then? I use a 0.94 rubber but I'm wondering if I should go down to like a 0.6 thickness or just remain at the 0.94.
5. If I just used my propellor out of the box would I be losing any performance from that? I noticed that people tend to change the pitch of their 24cm ikara propellor but what benefit does that have compared to just using it out of the box?
6. I noticed that some people tend to shim the trailing edge of their horizontal stabilizer to create more climb but wouldn't that lead to stalling as the plane descends down?
7. Finally, what CG is optimal for such a big wing for the 2023 FFM Division C kit?
Josh,

If you haven’t already done so, you’ll want to read all the earlier posts from me, Coach Chuck and Jeff Anderson in this forum. Several of your questions have already been addressed.

Here are some additional thoughts:
1. Good rubber motor winding procedures, a good propeller and rubber well matched to the propeller and airplane trim are the critical success factors for the event. Also, lots of practice and testing of slight changes in propeller pitch and rubber density. See previous posts for a video of me winding a helicopter motor from a couple years ago. As noted in earlier posts, any reasonable airplane design will do. Airplane design is only 10% to 20% of the event.
2. The broad flaring Ikara weighs about 2.4 grams and the symmetrical Ikara is about 2.0 grams. So, to keep the CG the same, you’ll need to move the wing forward on the FF kit if you install a heavier propeller. “Dives straight down” sounds like the CG is too far forward (I say this based upon over 200 test flights by my students so far this year). See here for sanding and trimming the Ikara flaring prop for better performance https://scioly.org/forums/viewtopic.php?t=6085&start=70 and here https://scioly.org/forums/viewtopic.php?t=6554
3. You have to fully wind to determine a particular motor, trim, CG and prop and prop pitch effect on the climb, cruise (this is the mid portion of the flight where the airplane stays at the same altitude for 30-40 seconds) and let down (this is the name for the descent).
4. (and 5.) Determine rubber thickness (actually density; see previous posts) is done by lots of test flights. The FF kit comes with three rubber widths (again calculate the density of every motor) try them all with the stock prop and stock prop pitch. Then increase the prop pitch 2 degrees and test all three again. Then increase by 2 degrees and test all three again; etc. Longest flight duration (if rubber winding is consistent) is your best rubber. .06 rubber is not going to be any good on the FF kit with the 24 cm prop. Stick with what came with the kit and calculate rubber density of every motor.
6. Shimming the TE of the stabilizer has only a slightly different effect than raising the LE of the wing. As the FF kit has an adjustable wing incidence angle and doesn’t have an adjustable stabilizer incidence, stick with the wing incidence. Yes, an airplane with too much decalage angle (see my previous posts for definition) will stall. Test small changes in CG location and small changes in wing incidence to see their effect.
7. The starting point CG for the FF 2023 kit is 2.125” forward of the wing TE. Start there and test changes after you have first determined your best propeller pitch and rubber width (density). Moving the CG forward will require more wing incidence and will generate higher lift and higher drag and is probably not the way to go (but test it). Moving the CG back in 1/8” increments (and probably reducing the wing incidence if stalling, is probably a good direction to test. Again, work on the propeller pitch variations and the rubber density first.

Have fun with your airplane and do lots of test flights.

Brian T
Thank you so much!
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Re: Flight B/C

Post by Maxout »

I'm going to focus specifically on the question of what makes a top placing Flight program, the rest is a matter of cooking up a good plane and flying process per the wisdom provided.

Top 10 Flight programs at the SO Nats are dictated by forces within and without the team. Last year's rules saw an interesting intersection in which the top EWS student was on the top team in the nation. That is seldom the case. A prime example would be that Guha Ekambaram was in the running for best WS student in the nation and his team was eliminated pretty soundly at the state level.

At the high school level what we're seeing is that the best Flight students are involved in the USA F1D program. I wouldn't say that is the true differentiating factor, rather that the best students are gravitating to that. The best students are also all involved in AMA competition. That process has definitely influenced their flying. Unfortunately, this means there is a direct correlation between traveling to contests and having a top 10 Flight program. Is it possible to achieve that status without traveling? Possibly, but it's very difficult because you can't see and handle airplanes and equipment from other fliers, both adults and students, so that you can increase your understanding of building and flying. So now we're zeroing in on what makes the best students: you either need a high level in-person mentor, or you need to travel. It is extremely difficult to progress past the basic levels without traveling. As someone who made it to a competitive level in outdoor flying without traveling, during middle and high school, such an endeavor comes at the cost of nearly everything else you do. I was involved in full scale flying, 4H clubs, and my local church, and getting to a regionally competitive level in my non-SO outdoor flying required me to incorporate flying into all of those non-flying activities because I couldn't afford to travel. I'm not saying there's anything bad about that, rather that you will have to make some choices about what you want to do with the next few years of your life. Personally the only thing I would change in what I did is leveraging my full scale flying to travel to model flying meets. I had that opportunity and chickened out. It worked out in the end anyway. Bottom line: the best Flight students, especially in high school, spend a significant amount of their time on flying activities. They generally choose aviation careers or at least pursue college degrees which could be used in the aviation industry. All of those are good things, but I'm feel that you should understand the level of commitment required to be a top 10 competitor. If you don't want to be an aero engineer, there is absolutely nothing wrong with that, but you do need to make some cost/benefit choices in terms of how much effort you put into Flight vs other endeavors. Perhaps you just love flying model airplanes. In that case consider whether top 10 status really gets you what you want out of flying. Maybe it does, maybe it doesn't.

So let's look at what makes a top 30 Flight student, so we can look at the realistic opportunities for someone who might not want to spend a substantial part of their waking hours pondering toy airplanes (they're all toys, even the ones with missiles). In that scenario, you can choose either a kit or a scratch build and be very successful. If you're on a strong team, I would frankly encourage sticking mainly to kits because most teams that go to the Nats fly kits, and they do fine. As described above, seldom do the absolute top end Flight students make it to Nationals because they typically manage, unfortunately, to be attached to teams that aren't dominant in enough other events. Think of this as a football example: our county high-school is not exactly known for its football team. A few years back, a big time college came down here and recruited one of their students who went on to be a top ranked running back. That high school team is currently 2 and 8, so like I said, not exactly a renowned team. So you have to bloom where you're planted, and you might get bigger opportunities in the future.

Now down to how to implement the above: build good airplanes, keep a quality notebook of each build, documenting weights, techniques, etc for each component of each build. Get quality tools and materials and learn how to use them. Download "The Best of INAV" at indoornewsandviews.com and read it. Now read it again. Ok, one more time. Now pick stuff that's immediately useful that you've read and practice it. Fly as often as you possibly can in the best conditions you can find. This could mean flying outside on calm evenings. You might lose a plane or two to a thermal and discover the miracle of soaring while you're at it. Keep records on the adjustments you make and the power systems that work. Learn how propellers work, how to adjust them, and how to make your own propellers better than commercially available ones. Become truly skilled at covering your plane as perfectly (not necessarily tightly) as possible. Learn to trim the plane to fly with as few warps as possible, in a stable manner, without and excessively forward CG. Learn how consistently get your plane to your target altitude with minimal error. And of course, learn to optimize rubber motors and wind them to 110%.

Long winded reply, I'm sorry, but I felt your question deserved this level of honesty and completeness.

By the way, that super annoying kid named Josh Finn that wouldn't stop flying toy airplanes in the church gym graduated with two engineering degrees. He said in 2015 that no one would ever again make a living wage selling freeflight competition kits. In 2019 he went full time at some outfit called J&H Aerospace, and in 2022, for the first time in easily 20 years, there were more than 10 juniors flying AMA endurance events at the US Nats. It's been a fun ride, and I'm not done with it.
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Re: Flight B/C

Post by coachchuckaahs »

Josh hit on some major stuff there!

I don't know if "traveling" follows or leads expert fliers. But, there are MANY opportunities to improve your flying skills outside SO, and to excel all the way to international competition. My team of 4 SO kids, including Guha, will represent the USA next month in Romania. They all started in SO.

We delved into travelling to contests about the same time we won the Cornell Nats WS event in 2019. I would say we got good at SO and then branched out, but I have seen others go the other direction. There is NO DOUBT that experiencing competition in many classes of flying broadens your perspective and gives you more skills to top out in SO. We thought 8g (7.5 back when) was a "fragile" airplane. But then we built 3.1g Limited Penny Planes. And then F1D at 1.4g, and much larger! Now the LPP's are tanks and the SO planes slabs!

Beyond the involvement in other flying events, some keys that Josh pointed out that I strongly agree with:

1. Fly. A lot. And again. Typically by the time we got to Nats we had around 500 flights. We knew what worked and what did not.
2. Logs. Do NOT short change the log. You need many columns (we have about 20) of information on each flight. Sometimes the log takes longer than the flight.
3. Experiment. Change things. BUT ONE AT A TIME. Record the changes in your log, and understand the impact on the flight. The stopwatch will tell you if you improved or not (along with altitude reached)
4. Read. There is a TON of information to be had on indoor flying. While you can ask here, you will get far fuller answers by reading the resources Josh pointed to. I would add past years of this forum as a resource.
5. Get a mentor. Even if they do not have any indoor experience, a dad or local adult with aero experience can see things that you may not see right away. I knew NOTHING when I started coaching around 2016. I flew outdoor R/C pylon racers, so I knew airplanes, but this was completely different! Having a set of eyes that are scientifically or engineering inclined will help whether they know indoor (yet) or not. You can visit the AMA website, www.modelaircraft.org, to find nearby clubs, and then visit and see if someone is willing to get out of their comfort zone.

Coach Chuck
Last edited by coachchuckaahs on December 3rd, 2022, 11:41 am, edited 1 time in total.
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2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
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Re: Flight B/C

Post by poonda »

tested a high aspect ratio design and i'm not sure how to fix some weird behaviors;

upon launch the plane starts circling left but then straightens itself out by a weird dutch roll process that eventually results in a right turn
after this weird launch, the plane climbs about 5ft and then maintains altitude for roughly a minute
there aren't any issues in the glide and nothing is loose or broken

anybody know how to fix this? i've never seen this before
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Re: Flight B/C

Post by Maxout »

poonda wrote: December 2nd, 2022, 7:01 am tested a high aspect ratio design and i'm not sure how to fix some weird behaviors;

upon launch the plane starts circling left but then straightens itself out by a weird dutch roll process that eventually results in a right turn
after this weird launch, the plane climbs about 5ft and then maintains altitude for roughly a minute
there aren't any issues in the glide and nothing is loose or broken

anybody know how to fix this? i've never seen this before
Post photos if you can. High aspect designs make me nervous and don't seem to be the best solution this year. They tend to be very aeroelastic in any year, but last year we didn't have a choice. This year we do. Fun fact in spite of that: last year's designs do appear to be legal for Div B, or at least some of them.

Verify that you have both left thrust and left rudder trim, and also that your stab isn't tilted so the right side is higher than the left, as that can also cause problems. the stab also must be warp-free, or it will twist the tailboom at high speeds, causing the stab tilt to change, sometimes dramatically.
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Re: Flight B/C

Post by jgrischow1 »

I was trying to help my kids with their plane today and we weren't having much luck. Guru Division C kit. I didn't see them build it but it didn't look too bad. Everything on the plane looked to me like it should be doing a standard left turn. Stab tilt, rudder, etc. I think this was not supposed to happen, but the wing seems unbalanced or something because the wing posts weren't straight up and down...the wing was leaning to the left (which again I would think would induce a left turn). However, what happened was either a nasty left roll right into the ground, or, if they adjust the incidence and wing mount position, it would stay up longer but almost look like it was fighting itself...alternatively want to go left then right. Either way, we couldn't get even one full orbit around the gym no matter the winds. Any ideas?
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Re: Flight B/C

Post by bjt4888 »

jgrischow1 wrote: December 2nd, 2022, 8:58 pm I was trying to help my kids with their plane today and we weren't having much luck. Guru Division C kit. I didn't see them build it but it didn't look too bad. Everything on the plane looked to me like it should be doing a standard left turn. Stab tilt, rudder, etc. I think this was not supposed to happen, but the wing seems unbalanced or something because the wing posts weren't straight up and down...the wing was leaning to the left (which again I would think would induce a left turn). However, what happened was either a nasty left roll right into the ground, or, if they adjust the incidence and wing mount position, it would stay up longer but almost look like it was fighting itself...alternatively want to go left then right. Either way, we couldn't get even one full orbit around the gym no matter the winds. Any ideas?
A bad roll to the left can usually be fixed by increasing left wing washin. Hopefully the kit instructions have info about this setting. It's basically a twist in the wing so that the left wing trailing edge is lower than the leading edge. Depending upon the design, for this year's airplanes, the twist amount can either quite small, like 1/8" - 1/4" or quite large (Freedom Flight kit) like 0.5" or a little more.

Adjusting wing incidence will somewhat improve the rolling/diving, but adjust the washin first. Also check the balance point of the airplane to make sure it is per the kit recommendation.

Brian T.
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Re: Flight B/C

Post by Maxout »

jgrischow1 wrote: December 2nd, 2022, 8:58 pm I was trying to help my kids with their plane today and we weren't having much luck. Guru Division C kit. I didn't see them build it but it didn't look too bad. Everything on the plane looked to me like it should be doing a standard left turn. Stab tilt, rudder, etc. I think this was not supposed to happen, but the wing seems unbalanced or something because the wing posts weren't straight up and down...the wing was leaning to the left (which again I would think would induce a left turn). However, what happened was either a nasty left roll right into the ground, or, if they adjust the incidence and wing mount position, it would stay up longer but almost look like it was fighting itself...alternatively want to go left then right. Either way, we couldn't get even one full orbit around the gym no matter the winds. Any ideas?
I'm going to be extremely blunt here because my lot in life this season seems to be fixing Guru planes at every meet I attend. The Guru plane this year is a hot mess that escaped any substantive testing before it was released. I've worked on trimming almost a dozen of these darned things in the past two months. Only after two specific modifications did any of them end up flying nice happy climbing circles. The two major design flaws are these:

1. The fin is too small. Because it's too small, any amount of fin offset sufficient to get a turn going results in a spiral dive.
2. The stab ribs are literally the wing ribs scaled only in the chord dimension, so you end up with 10% more camber in the stab than the wing. This is what you'd do if you wanted the plane to fly backwards. Anytime the plane picks up any speed over cruise, it dives straight in.
2b. Since the kit isn't supplied with a covering frame and has the audacity to claim that wrinkly covering won't hurt flight performance, you end up with baggy covering. There being no mid-panel ribs in the tail, the tail ends up even more baggy than the wing. Now the stab is effectively 20% more cambered than the wing. Ouch!!!

So how to fix it since you've spent the money on these kits and they're not exactly cheap anymore:
1. Get a cheap crappy foam plate from wally world, as thin and floppy foam as possible, cut a second fin from it just like the existing one. Glue it to the LEFT tip of the horizontal tail. Don't remove the existing fin, you need both of them for the model to fly well. Turn trim will become more stable.
2. Cut the trailing edge of the horizontal tail loose from the back of the fuselage. Glue a 1/4" thick block between the stab trailing edge and the fuselage. Yes, 1/4". I'm not kidding.
2b. Now add at least .5g of clay to the nose and locate the wing so that with a rubber motor loaded, the model balances about 3/8" ahead of the wing trailing edge. The wing absolutely must not be more than 2.75" aft of the nose on the Div C plane. Add more clay as needed to get the plane to balance correctly with the wing positioned accordingly. Adjust wing incidence as needed for a stall-free cruise.

Now you have a flying airplane that is horribly inefficient, but it'll at least fly. Expect about 70 second flight times at maximum torque (1.2 in-oz). If you move the rear hook forward 2", you can use a 2g loop of 1/8" rubber for power and the model will climb and cruise better, usually 100-110 second flights.

If you want a cheap airplane that just flies, lasercutplanes.com will set you up with something you'll like.
Last edited by Maxout on December 3rd, 2022, 7:33 pm, edited 1 time in total.
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Re: Flight B/C

Post by Frost0125 »

Hi!

I'm new to build events, and ordered a J and H Aerospace kit for flight. Since it is supposed to arrive in the next few days, I looked at the extra items necessary for build, and it mentioned a winder. Is there anyway to get a winder at a brick and mortar store (preferred) , or fairly quickly (within next week)? Or even DIY
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Re: Flight B/C

Post by pumptato-cat »

No. Doesn't J&H sell winders? I don't know of any brick and mortar stores that sell winders in NC.
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