Scioly.org

Posted: **October 24th, 2022, 4:55 pm**

Hi, What is a good torque to launch at? Whenever I'm winding my motor, it goes to about 200 winds less than the predicted number of winds using the equation that was given to me. Am I doing something wrong here?

Also, for Flight Division B, what times are you guys getting? Just wondering!!

Posted: **October 24th, 2022, 6:00 pm**

jander14indoor, Thanks! I will try to bend the needle! :) The CA glue I saw in local stores didn't have viscosity labeled, which was a bit odd. (Loctite...)
bjt4888, I have looked at every forum I can find(still trying to pick up all the vocab used in flying events, there's a TON of new terms...) and am considering making my own propellers from cut balsa, but as of now we're sticking with the Ikara one provided before doing major changes. Those planes look great! (The ones in the background are pretty :D) They remind me a bit of the FF 2023 ones. I'd start a discussion but I don't have enough knowledge to comment yet 😅

danxmemes, I'm willing to post flight times once my partner and I get flying-that should be next week. We're Div C though, I doubt it'd help much. Let me know if you're interested!

Thanks for your advice, everyone!!!!

Posted: **October 24th, 2022, 11:20 pm**

danxmemes wrote: ↑October 24th, 2022, 4:55 pm Hi, What is a good torque to launch at? Whenever I'm winding my motor, it goes to about 200 winds less than the predicted number of winds using the equation that was given to me. Am I doing something wrong here?

Also, for Flight Division B, what times are you guys getting? Just wondering!!

Answer is very much, it depends. Different prop/airplane combinations and different ceiling heights require different launch torque. Give us some details of your airplane, motor, and propeller and we can give better advice.

What is the motor thickness, how are you measuring it, how precisely? When you say it only goes to 200 winds less than predicted, do you mean you can only get to 1800 turns before breaking, but equation says 2000? Are you lubing? How are you winding?

Details, really need details when you ask questions about how YOUR plane is behaving or misbehaving.

Div B flight times. One kit manufacturer I know well is reporting 2 min plus on his kit. He thinks it is capable of 2:30. It is NOT maxed out in wing area, so higher still is likely.

bjt4888 wrote: ↑October 24th, 2022, 9:19 am <SNIP> I'm not showing the propeller as this, in my belief, is one of the keys to the event this year. Students should research possible propellers in this forum (look at previous years forums; maybe especially 2015; hint, hint) and on the NFFS website and other indoor free flight forums and web pages. And, test, test, test different solutions.

Enjoy,

Brian T

I'm going to be slightly, but only slightly, contrarian to Coach Brian's view. He is absolutely RIGHT that to get max time out of these planes you have to match prop to rubber to achieve the most efficient use of the energy you put into the rubber. Its hard, and takes lots of time. The truth of the statement is demonstrated by the consistently good performances his teams turn in.

BUT, underlying that is a big assumption. You've built a good, light plane, have it properly trimmed, and can perform consistently!
For new teams, THAT is your first job. Until you have a plane that can fly well, and know how to trim, you don't have a consistent platform to work on prop-rubber combinations. IF you are new to this, THOSE are your first tasks! Build accurately, build light, learn to trim. These are hard first steps, but very doable, and don't have to take TONS of time.

And once you've mastered that, yes, you HAVE to spend time testing loads of variations to match prop & rubber to your plane to continue improving your times.

Comment on answers you see in this forum. I like to group them to three levels.
First, questions and answers on how to get started. Basic stuff, basic principles. Everybody needs to know these things. Goal, get your plane to fly out of your hand, gain altitude and return to floor under reasonable control. Say 30-60 second flights.
Second, advancing questions. You can build a plane, you can get it to fly, sort of, but need help either with some odd behavior, or how to move the next step. You can get your plane to fly 60 to 90 second flights, but perhaps not consistently. Here things get more specific. Maybe discussion on why you need wing warp, or how to control turn diameter. This is where you start moving up the performance curve.
Third, the really hard stuff, how to get those crazy high times. You are already flying 75% of the capability of this years planes (90 sec plus this year) and want to get nationals winning times. Here's where you get into the really hard stuff, and where information gets sketchier, understandably. I say understandably, because the best flyers want to protect their hard earned edge. And folks like me, who don't coach specific teams (I'm an ES) so don't focus on the last ounce of performance actually may not know specific answers, just directions to attack.

So, when you read the questions and replies, recognize where YOU are in this journey (Oh My, I'm getting pretentious here me thinks). Focus on the questions and answers appropriate to your stage. If you are a beginner, don't ignore the advanced stuff, but maybe put it on the back burner until you are ready for it.

Jeff Anderson
Livonia, MI

Posted: **October 25th, 2022, 6:06 am**

jander14indoor wrote: ↑October 24th, 2022, 11:20 pm
danxmemes wrote: ↑October 24th, 2022, 4:55 pm Hi, What is a good torque to launch at? Whenever I'm winding my motor, it goes to about 200 winds less than the predicted number of winds using the equation that was given to me. Am I doing something wrong here?

Also, for Flight Division B, what times are you guys getting? Just wondering!!
Answer is very much, it depends. Different prop/airplane combinations and different ceiling heights require different launch torque. Give us some details of your airplane, motor, and propeller and we can give better advice.

What is the motor thickness, how are you measuring it, how precisely? When you say it only goes to 200 winds less than predicted, do you mean you can only get to 1800 turns before breaking, but equation says 2000? Are you lubing? How are you winding?

Details, really need details when you ask questions about how YOUR plane is behaving or misbehaving.

Div B flight times. One kit manufacturer I know well is reporting 2 min plus on his kit. He thinks it is capable of 2:30. It is NOT maxed out in wing area, so higher still is likely.

bjt4888 wrote: ↑October 24th, 2022, 9:19 am <SNIP> I'm not showing the propeller as this, in my belief, is one of the keys to the event this year. Students should research possible propellers in this forum (look at previous years forums; maybe especially 2015; hint, hint) and on the NFFS website and other indoor free flight forums and web pages. And, test, test, test different solutions.

Enjoy,

Brian T
I'm going to be slightly, but only slightly, contrarian to Coach Brian's view. He is absolutely RIGHT that to get max time out of these planes you have to match prop to rubber to achieve the most efficient use of the energy you put into the rubber. Its hard, and takes lots of time. The truth of the statement is demonstrated by the consistently good performances his teams turn in.

BUT, underlying that is a big assumption. You've built a good, light plane, have it properly trimmed, and can perform consistently!
For new teams, THAT is your first job. Until you have a plane that can fly well, and know how to trim, you don't have a consistent platform to work on prop-rubber combinations. IF you are new to this, THOSE are your first tasks! Build accurately, build light, learn to trim. These are hard first steps, but very doable, and don't have to take TONS of time.

And once you've mastered that, yes, you HAVE to spend time testing loads of variations to match prop & rubber to your plane to continue improving your times.

Comment on answers you see in this forum. I like to group them to three levels.
First, questions and answers on how to get started. Basic stuff, basic principles. Everybody needs to know these things. Goal, get your plane to fly out of your hand, gain altitude and return to floor under reasonable control. Say 30-60 second flights.
Second, advancing questions. You can build a plane, you can get it to fly, sort of, but need help either with some odd behavior, or how to move the next step. You can get your plane to fly 60 to 90 second flights, but perhaps not consistently. Here things get more specific. Maybe discussion on why you need wing warp, or how to control turn diameter. This is where you start moving up the performance curve.
Third, the really hard stuff, how to get those crazy high times. You are already flying 75% of the capability of this years planes (90 sec plus this year) and want to get nationals winning times. Here's where you get into the really hard stuff, and where information gets sketchier, understandably. I say understandably, because the best flyers want to protect their hard earned edge. And folks like me, who don't coach specific teams (I'm an ES) so don't focus on the last ounce of performance actually may not know specific answers, just directions to attack.

So, when you read the questions and replies, recognize where YOU are in this journey (Oh My, I'm getting pretentious here me thinks). Focus on the questions and answers appropriate to your stage. If you are a beginner, don't ignore the advanced stuff, but maybe put it on the back burner until you are ready for it.

Jeff Anderson
Livonia, MI

I am using a slightly modified j&h kit, with 3/32" rubber, the propeller is the same one from the kit. We are lubing every 2 flights, winding up to .4 inch ounces on the torque meter before moving in. We stretch 5x the relaxed length, but still are only able to achieve the 1500 out of the predicted 1700 for our rubber. I'm sure that more winds would = to more time in the air? As for trimming, my partner and I are still working on that part. Thanks though!!

Posted: **October 25th, 2022, 8:49 am**

Dax,

I agree with all of Jeff’s suggestions on process.

Is the 1,700 turns you mentioned calculated using the formula? If so, note that these are turns to break the motor. Note in my previous posts and in the document I attached to an earlier post that getting 80% of breaking turns is a pretty good winding. Also note that in YouTube video showing me winding that I wind to 1.2 to 1.4 inch ounces befor backing off to launch torque (launch torque is specific to your airplane/propeller and trim, but 0.25 to 0.35 in oz might be a good start for a 24 ft ceiling height gym. More launch torque will give you more climb height (if the airplane is properly trimmed) and a change of 0.02-0.05 inch ounces from your starting point torque might give you 2-6 ft more height.

Yes, keep asking good questions and include specific data on your trim settings and winding process and specs so that we can give good suggestions.

Brian T

Posted: **October 25th, 2022, 9:31 am**

Can someone explain rubber hysteresis to me? I understand that de-winding decreases torque, helping you avoid hitting the ceiling, whereas if you don't de-wind, you get in less winds before hitting the ceiling. Am I understanding this right? The entire concept is a bit fuzzy to me and I'm not sure if I completely understand it--will better understanding come with practice and experience? Should I attempt a graph like bernard did in 2015? (i have read all forums I can find and the verbal descriptions just aren't clicking with me if you know what I mean)

Posted: **October 25th, 2022, 10:20 am**

pumptato-cat wrote: ↑October 25th, 2022, 9:31 am Can someone explain rubber hysteresis to me? I understand that de-winding decreases torque, helping you avoid hitting the ceiling, whereas if you don't de-wind, you get in less winds before hitting the ceiling. Am I understanding this right? The entire concept is a bit fuzzy to me and I'm not sure if I completely understand it--will better understanding come with practice and experience? Should I attempt a graph like bernard did in 2015? (i have read all forums I can find and the verbal descriptions just aren't clicking with me if you know what I mean)

Cat,

Without getting into the basic science, the concept is that you retain a significant portion of the energy of a full winding to 80-90% max turns when you backoff turns to a selected launch torque. So, you have much more energy in your system than you would have had if just winding and stopping at the launch torque. You also have many more turns.

Graphing or charting torque during both the wind up phase and the backoff phase is interesting, but not absolutely necessary to understand the concept. Flying at various max torque/launch torque specs and recording flight times and climb heights will demonstrate the concept to you. You will find that winding to a max torque of 1.1 in oz (with .062 g/in rubber; or approx .094" rubber) and backing off to a launch torque of 0.4 in oz (for example) will potentially give you a significantly different result from winding to 1.2 or 1.3 and backing off to the same 0.4 launch; even though the turn count difference between 1.1 and 1.3 might be only one or two winder turns (or 5 maybe, depending upon the number of uses of that rubber motor).

Enjoy your airplane/energy testing system!

Brian T

Posted: **October 25th, 2022, 10:35 am**

Cat:

Basically, hysteresis means there is a step change based on direction. For example, if you pull a toy along with a string, the toy follows behind you. For every foot you move, the toy moves a foot. However, if you reverse direction, you move several feet before the toy begins to move at all. It was displaced say two feet to the right (you are moving to the left), but when you reversed direction it is now displaced two feet to the left, for a change in relative displacement of 4 feet. This is one case of hysteresis.

In winding and unwinding rubber, the torque increases as you wind. However, when you stop winding and reverse direction, there is a step decrease in torque. The unwind torque follows a similar shape but lower torque curve than the winding. The difference is energy lost to friction (heat).

So, in a hypothetical, lets say you can wind to 1000 turns to get 0.4 torque. However, you may be able to wind to say 2000 turns at 1.2 torque, and then unwind 200 turns to get the torque to 0.4. This means you have 1800 turns in the rubber at 0.4 launch torque, instead of 1000 turns. This is hypothetical, but may be representative of some rubber setups. This represents a substantial increase in the stored energy in the rubber at a given launch torque.

Bottom line, because of the unwind torque curve being lower than the wind torque curve, you always want to wind to the highest "safe" torque and then back down to launch torque, rather than simply winding to launch torque.

A video I made last year at https://youtu.be/KG6spsA058E talks about matching prop and rubber, and shows some torque curves. I do not recall if it touches on hysteresis.

Coach Chuck

Posted: **October 25th, 2022, 1:43 pm**

pumptato-cat wrote: ↑October 24th, 2022, 6:00 pm jander14indoor, Thanks! I will try to bend the needle! The CA glue I saw in local stores didn't have viscosity labeled, which was a bit odd. (Loctite...)
bjt4888, I have looked at every forum I can find(still trying to pick up all the vocab used in flying events, there's a TON of new terms...) and am considering making my own propellers from cut balsa, but as of now we're sticking with the Ikara one provided before doing major changes. Those planes look great! (The ones in the background are pretty ) They remind me a bit of the FF 2023 ones. I'd start a discussion but I don't have enough knowledge to comment yet

danxmemes, I'm willing to post flight times once my partner and I get flying-that should be next week. We're Div C though, I doubt it'd help much. Let me know if you're interested!

Thanks for your advice, everyone!!!!

Cat,

Good job doing your research. This will serve you well all season long. Starting with the Ikara is a good idea. A second step prop would be the simple customized Ikara you saw in the 2015 forum “design” thread. Any terminology questions are welcome.

The three airplanes in the background of the picture I linked are outdoor free flight models. The red and white airplane is a 48” span “Unlimited Rubber” plane I built (all balsa) when I was a teenager (half a century ago). It requires a 30 strand 36” motor of 1/8” strip (so, basically 100 ft of rubber strip). The airframe weighs 4.0 ounces and the rubber motor weighs 3.0 ounces. The rubber motor powers the airplane to about 400 ft in about two minutes and it then glides unpowered in circles.

The airplane with the purple wing is a current FAI international class F1B rubber powered model and its wingspan is about 5 ft. This airplane uses a 12” long motor made up of 30 strands of 1/8” rubber strip. You wind this motor to 120 inch ounces and it climbs like a rocket to bout 400 ft till the turns run low and then transitions to glide in circles for about six minutes (in calm evening air).

The white airplane that you can see only a portion of is a relatively current international FAI class F1C “gas” (actually alcohol) powered model. It has a 9.5 ft wingspan and is powered by a 0.15 cu in internal combustion engine that turns the tiny 7” propeller at about 27,000 rpm (and about 140 decibels). This airplane class climbs like a dragster to about 400 ft in about 4.0 seconds before transitioning to a circular glide. The F1C is a loaner to the US Junior world championship team.

All these models are out as demos for my students to look at for the fun of it.

Brian T

Posted: **October 25th, 2022, 4:43 pm**

bjt4888 wrote: ↑October 25th, 2022, 8:49 am Dax,

I agree with all of Jeff’s suggestions on process.

Is the 1,700 turns you mentioned calculated using the formula? If so, note that these are turns to break the motor. Note in my previous posts and in the document I attached to an earlier post that getting 80% of breaking turns is a pretty good winding. Also note that in YouTube video showing me winding that I wind to 1.2 to 1.4 inch ounces befor backing off to launch torque (launch torque is specific to your airplane/propeller and trim, but 0.25 to 0.35 in oz might be a good start for a 24 ft ceiling height gym. More launch torque will give you more climb height (if the airplane is properly trimmed) and a change of 0.02-0.05 inch ounces from your starting point torque might give you 2-6 ft more height.

Yes, keep asking good questions and include specific data on your trim settings and winding process and specs so that we can give good suggestions.

Brian T

Thank you!!! Your video and guide were really helpful as well!!

Scioly.org

Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C

Re: Flight B/C