Wright Stuff C

[coachchuckaahs]

I think you'll be disappointed with a gearbox, especially one that gears up. I have RC planes with gearboxes and they need strong prop shafts, good quality gears, ball bearings, etc... stuff that is way too heavy for WS. We are building light and usually end up with only about 0.5 grams ballast, not enough leeway for a gearbox.

Let's assume for the moment that gearbox and prop could be 1.5g, If we're gearing up, i think the prop has to be smaller - less blades, less pitch - still 8cm? Is that how you would see this?

I think the idea is that the prop is already too small. Instead, the gearbox would allow a shorter fatter piece of rubber, allowing a shorter motor stick and less winding. However, the gearbox losses may make this not feasible.

Coach Chuck

[coachchuckaahs]

PM sent, thanks.

.

Did not get the PM

Coach Chuck

[Airco2020]

I think you'll be disappointed with a gearbox, especially one that gears up. I have RC planes with gearboxes and they need strong prop shafts, good quality gears, ball bearings, etc... stuff that is way too heavy for WS. We are building light and usually end up with only about 0.5 grams ballast, not enough leeway for a gearbox.

Let's assume for the moment that gearbox and prop could be 1.5g, If we're gearing up, i think the prop has to be smaller - less blades, less pitch - still 8cm? Is that how you would see this?

I think the idea is that the prop is already too small. Instead, the gearbox would allow a shorter fatter piece of rubber, allowing a shorter motor stick and less winding. However, the gearbox losses may make this not feasible.

Coach Chuck

How do I think about how fat the rubber needs to be? If the gear was 5:1, and pretend the losses were small, It seems like the torque from the rubber band would need to be 5X to get the same performance out of the same prop? How much more torque is a .125 motor than a .064? 2X, more? Or is it how much you can wind up to, .064 maybe .3 -.5lbs but .125 can wind to 1 - 1.2 or something like that. I know there is some equation in here that is way over my head but I'm not sure how far in the fatter direction I need to go?

[CrayolaCrayon]

Let's assume for the moment that gearbox and prop could be 1.5g, If we're gearing up, i think the prop has to be smaller - less blades, less pitch - still 8cm? Is that how you would see this?

I think the idea is that the prop is already too small. Instead, the gearbox would allow a shorter fatter piece of rubber, allowing a shorter motor stick and less winding. However, the gearbox losses may make this not feasible.

Coach Chuck

How do I think about how fat the rubber needs to be? If the gear was 5:1, and pretend the losses were small, It seems like the torque from the rubber band would need to be 5X to get the same performance out of the same prop? How much more torque is a .125 motor than a .064? 2X, more? Or is it how much you can wind up to, .064 maybe .3 -.5lbs but .125 can wind to 1 - 1.2 or something like that. I know there is some equation in here that is way over my head but I'm not sure how far in the fatter direction I need to go?

You can wind .125 beyond 2.0. Inch ounces for sure. I've been able to wind one has hard as 2.5 personally, but some around here may of been able to achieve higher torques.

[coachchuckaahs]

Let's assume for the moment that gearbox and prop could be 1.5g, If we're gearing up, i think the prop has to be smaller - less blades, less pitch - still 8cm? Is that how you would see this?

I think the idea is that the prop is already too small. Instead, the gearbox would allow a shorter fatter piece of rubber, allowing a shorter motor stick and less winding. However, the gearbox losses may make this not feasible.

Coach Chuck

How do I think about how fat the rubber needs to be? If the gear was 5:1, and pretend the losses were small, It seems like the torque from the rubber band would need to be 5X to get the same performance out of the same prop? How much more torque is a .125 motor than a .064? 2X, more? Or is it how much you can wind up to, .064 maybe .3 -.5lbs but .125 can wind to 1 - 1.2 or something like that. I know there is some equation in here that is way over my head but I'm not sure how far in the fatter direction I need to go?

The total stored energy will scale with the total mass of the rubber. The number of winds will scale with the cross sectional area (or width), as will the torque (both running torque and peak winding torque). Assuming proper lube, stretch winding, etc.

Coach Chuck

[bjt4888]

that sounds like a bit of a threat...

It wasn't directed at you, but yes. I've gotten a lot of help here (thank you!), and I've respected requests not to share certain things. I feel like I should put on my flame suit because I know not to expect much support in my argument (understandably):

I can see Luke losing interest in WS because he's unhappy with the build rule. It's clear to him that other kids are directly benefiting from years of adult expertise that is unavailable to him because of my limitations. He knows I have certain skills to offer and he doesn't like that these have been carved out and forbidden. He's right. We'll respect the build rule, but be cool about it and help him out to whatever extent he needs, even if by PM if you don't want to post publicly (as some have done, thank you). Don't worry, he'll never compete against any of you, if anything because the rest of his Science Olympiad team is also weakly represented.

In general, I don't see a bright future for Wright Stuff if it eventually boils down to the same handful of heavily coached teams winning every year, and the other 35,000 high schools in the country know they don't stand a chance.

We started 4 years ago, and had nothing but the forums and the documents put out by SO. We are now highly competitive. I was not an indoor flyer. But the kids were tenacious, and just needed a little encouragement and direction. What I did not know, we asked on the forums, and we got good. In a hurry. First year we were 7th at Nationals, because the kids built (scratch, not kits) 12 planes and about 25 props. And took notes and tried new things. Yes, we have a starting point now, but quite frankly, the FF kit is VERY similar to our 2017 plane, which was strongly influenced by Bill Gowen's Carbon Penny plans. If you look at last year's forums, I was VERY active in sharing ideas and solving problems. This year we have yet to fly (first testing next Friday). I think you will find you are well ahead of many schools in that you have already flown a significant amount, and should have a storehouse of data in your logs to this point. That is the key!

Having the experience primarily helps us to shorten our trimming cycle, and know what to adjust when we see poor performance. But all of that has been posted on these forums. Yes, I bring 4 seasons of experience to the table, but some of my kids are in their third season, so it is their experience too. There is little I need to do other than making my kitchen table available, and organizing gym access (we need to rent a gym, since we are home schooled).

Keep asking questions, and keep encouraging people. But don't think the kids cannot learn or extend themselves. My kids do the observing, logbook, and adjusting (as well as all the building. They won;t let me touch the thing).

As far as times, they are also linked to conditions (altitude of facility, height of ceiling, HVAC, etc.) and do not serve much purpose in publication. There are enough times published so that you can get a feel for whether you are performing well.

One more thing I am doing is opening a flight workshop for our state schools, trying to help other schools in NM become competitive, and not frustrated.

Coach Chuck

Eric,

Sorry to be not posting lately. I coach four high school and one middle school team and they have been building in my workshop almost every day for the last two weeks. They’ve completed 9 WS airplanes with 3 almost done and two gliders almost done.

Just wanted to encourage you and your son and reinforce Chuck’s comments. I was a new SO coach in 2012 and helped one HS with glider. Knowing that Stan Buddenbohm was the top current competitive glider guy, we built his kit and practiced a lot and placed second at Michigan States (glider is the event that I know the most about). The next year, I coached three high schools in Glider and all had the potential (with better, flapper glider this year) to win at States, but nerves resulted in a 3rd and 4th. In my third year of coaching, Wright Stuff was the HS event. My three high schools built the Freedom Flight kit with a custom flaring propeller similar to the one shown on Chris Goin’s Double Trouble Plan. I bought a Harlan rubber stripper and we did very thorough testing of rubber loop density and finished in first place that year at Michigan States with a flight time of 3:46 in 22’ scrubbable ceiling. Two of the teams we beat that year finished 1st ant 4th at SO Nationals and our 3:46 compared well with other top State winning times (Southern Cal winner 3:45 in 24 ft no touch). My teams have continued to compete very successfully since. In seven years, we’ve won Michigan States 3 times and medaled (2nd or 3rd or 2nd and 3rd) every other year but one.

So, I’m relating this to hopefully encourage you and your son. Don’t be discouraged. It is not true that a handful of “heavily” coached teams will necessarily come out on top. That being said, there is an approach that I teach my students and recommend to others that essentially begins with “best practices research”. Read, read, read and discover what the best do and copy them to learn. There is a tremendous amount of info already out there in the past year’s Scioly forums and in Hip Pocket. Till you’ve built an exact copy of Bill Gowen’s designs (or other top designs) and flown it, you won’t really be able to learn fully the benefits of each design element. Also, I don’t know that the term “heavily coached” applies to me. Till a year ago, I had a very stressful full time job. I present best practices ideas to my students, we discuss and they build their airplanes 100% themselves. I stay after them to be sure that practices are scheduled regularly and I attend their practices to teach them the iterative process. By the middle of the season, they don’t really need me there except for moral support.

Normally, I will keep flight times as private team information as the Michigan States is highly competitive. But, I will share one bit (hopefully to encourage you to reach higher). On our first day of testing, we are flying 15% longer flights than any reported in this forum (or others). This is the only flight time data I will report this year, but, of course, we expect to improve as testing progresses. So, research - build, research - build, etc. Top level is achievable by anybody.

One more bit of Bio on me. I am not a top level indoor free flight flyer. I built a Wally Simmer EZB as a middle schooler and had fun with it and we used to fly ultra light Delta Darts for fun indoors. My free flight background is outdoor AMA gas from about age 12 -16. I put the hobby away mostly till I saw that the schools in my area needed help. I love teaching “hands-on” science. I read a lot because I love to read. Philosophy, history, classic literature and music are my primary interests (above Aerospace). My professional background includes: enterprise strategic planning, large project management, communications and government budgeting/finance.

Keep at it and have fun.

Brian T

[lechassin]

We just sent Luke off to his first meet, I have to wait till tonight to hear how he does.

Having confirmation that the total energy is based only on the weight of the rubber suggests to me that gearing up is a hopeless cause.

This is marginally off-topic, but I'm sitting here with my morning coffee and nothing else to do, so here goes: there are real planes with geared props but they're always geared down. The increased efficiency of a larger diameter prop trumps the weight of the gearbox. It's not commonly done because the huge prop's precession causes fatal accidents. A good example is my personal favorite airplane ever, the Sukhoi Su-31, which is dangerous enough that it's mostly crashed, er-- flown by specialists from ex-USSR:
https://www.youtube.com/watch?v=e4lxXBIsbBg&t=129s

2'36", no other stunt plane anywhere can hang like that, even after being modified to use the same powerplant.

By gearing up, you're doing the opposite and causing inevitable losses.

[lechassin]

Brian, Thank you! Your post is exactly what we wanted. Combing your post and knowing what's in other posts gives us a real-world target.

One thing is clear: if you moved to another state, the trophies would soon follow. You and Chuck inspire your team in a way that I cannot, namely because I, er, uh, well, let's just say that I've never worried about being good with kids, and it looks like that just caught up with me... I look at your bio and I can see why you're good at this event. You're curious by nature, and seeing the kinds of jobs you've listed, you're good with people.

Worse, for whatever reason(s) Luke's school obviously views the build events as known losers; any time invested there is perceived as wasted, they prefer to concentrate on the book-ish stuff where tools aren't required. That's a huge hurdle, hopefully my 8th grader and his friends will have a better experience if Luke does well this year.

[bjt4888]

Eric,

With the good results your son is getting, hopefully he can start to fix his school’s negative view of build events. Good luck with the “working with students” part of SO. I’m thinking you’re better in this than you let on.

Brian T

[lechassin]

Thanks for the encouragement. Hopefully if Luke does well the coaches will get involved. They're nice folks, they just don't seem like the GitterDun types.

How do you get more than one kid into the same room? I've tried and it's like herding cats.