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Author Topic: Flight times for 2017 SO Wright Stuff  (Read 3647 times)
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Olbill
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« Reply #75 on: March 11, 2017, 02:57:09 PM »

I use this to measure various parts of the building, girders, ducting etc.
https://www.amazon.com/gp/product/B01N64GLDQ/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

I just got one of these. Trying to understand the instructions now.

" The acquiescent edge of the instrument is the back porch".

"The volume measuring result will be display on the main screen finally, previous 3 times result will be display on the first, second, third added line."

Right!
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ceandra
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« Reply #76 on: March 11, 2017, 08:07:31 PM »

Bill:

Get a kid to help! I guess they did not stop at "New Math", now they have "New English"!

Chuck Grin
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JasperKota
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« Reply #77 on: March 13, 2017, 07:19:15 PM »

Brian and Don -
Thank you both for the great replies. I had no idea that I wasn't winding enough, then soon realized that I wasn't stretching far back enough while winding which is why rubber had snapped before when going over 120 winds with a 15:1 ratio winder.

I also did not know to relube the rubber - basically I should lubricate each motor again after each hard-wound flight?
I will give some updates once the practice area is open.
« Last Edit: March 13, 2017, 09:08:24 PM by JasperKota » Logged
ceandra
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« Reply #78 on: March 13, 2017, 07:26:47 PM »

Jasper:

We keep a sandwich-sized ziplock baggie wet with Armourall. It sits on the winding stooge/torque meter, so the kids remember to lube each flight. Keeps it nice and neat, rather than hand rubbing it. Drop the rubber in the bag, squish it around, its ready to go.

Chuck
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dslusarc
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« Reply #79 on: March 13, 2017, 07:41:11 PM »

e rubber - basically I should lubricate each motor again after each hard-wound flight?
I will give some updates once the practice area is open.

This is what I started doing with TSS, lube it well each wind. Still expect the rubber motor to break eventually so make spares. I just broke my SO motor yesterday winding it up to it to 2000 turns. This rubber does not seem to last long wound  hard many times.
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dslusarc
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« Reply #80 on: March 13, 2017, 07:49:14 PM »

Quote from: Olbill

I just got one of these. Trying to understand the instructions now.

" The acquiescent edge of the instrument is the back porch".

"The volume measuring result will be display on the main screen finally, previous 3 times result will be display on the first, second, third added line."

Right!

Bill,

That manual is rather amusing. I used the meter to measure the SO gym I fly in this past Thursday as well as the gym we fly in on Sunday. Was able to find the center of the building then measure out the FAI circle then take a height reading. Also was able to measure the available floor space. Triangle feature works pretty good. I was able to measure the ceiling height from across the room by measuring the hypotenuse then the base leg across the room and it calculates the height.  I am happy with it.

Don
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JasperKota
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« Reply #81 on: March 17, 2017, 03:33:31 PM »

Does the motor have to be wound in a certain direction (clockwise/counterclockwise)? I'm unsure as to what a motor wound backward is.

Practice session went well yesterday! Looking in retrospect I can still wind a more, but glad to say I reached my goal of two minutes.
First run, a minute 40 like usual, although I did wind more than I had before. There was a bit a stalling, so I moved the CG forward a bit (in comparison to the rear wing post)

Next run, 2040 winds, dewound until .42 oz.  Hit the roof twice, came down at 123 seconds with no winds left. Here's the flight: https://youtu.be/A5mfoEwSJIk (ignore the conversation in Chinese in the background  Tongue)

Then decided to switch to the second plane from the FF kit. This one flies more rapidly and has a much smaller circle compared to the other plane. Both planes have the left trailing edge about 3/32" lower than the right, and 1/4" rudder deflection to the left with the stabilizer tilted so the left is a little more than 1/4" higher. This plane was lighter compared to the first, and required more ballast to bring it up to the 7.5 gram minimum.
2055 winds, then dewound to .3 oz torque. 110 seconds, no touch flight, though I launched the plane at my waist. The flight: https://www.youtube.com/watch?v=lv34uVag44g

After that flight, I wound to around 2100, and then dewound to .34 oz. Launched while kneeling, no touch flight at 122 seconds.

Very happy with the results! There's still more room for winds, and I'm hoping to experiment with a flaring blade prop soon. Vanguard P-18 should be arriving over the weekend, so planning on focusing on trimming it next session. Thanks for the feedback from my previous posts!
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calgoddard
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« Reply #82 on: March 17, 2017, 05:45:24 PM »

JasperKota -

The rubber motor has to be wound in the proper direction in order to produce forward thrust.  This direction depends on whether the propeller is right-handed or left-handed.

A propeller that turns clockwise to produce forward thrust, when viewed from aft, is called right-handed. One that turns counter-clockwise, when viewed from aft, is said to be left-handed.

Almost all propellers used in model airplanes are right-handed.  Sometimes fliers use a right-handed prop and a left-handed prop on a scale model of a twin engine airplane.  

The propeller, and the rubber motor, of a single propeller model are typically wound clockwise, viewed from the front of the model.  Almost all winders have cranks that are turned clockwise in order to wind clockwise. The only exception I can think of is the Rees winder used on larger outdoor scale models.

Both your flights in the videos you posted recently look very good.  I am impressed that your airplane recovers so quickly when it collides with an obstruction. This is a good characteristic to have in an indoor model since it is hard to get the launch torque just right to get a no-touch flight that maxes out just below the beams and like fixtures. This is especially true in WS competition where you only have time for two official flights in the 8-minute Flight Period.

Any flight in a typical HS gym of a 2017 WS airplane over 120 seconds would probably finish in the top three in most regional Science Olympiad competitions. You are doing quite well. Keep up the good work!

In regard to the 123 second flight, how many turns did you back off, and how many turns remained unused when the model landed?  This is critical information that you need to record and analyze after each flight.  It tells you a lot about how well your rubber motor is sized for the prop, air frame, and trim you are currently using.



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Foosier
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« Reply #83 on: March 21, 2017, 08:50:44 PM »

Cal,

Can you provide more detail on this comment?   "In regard to the 123 second flight, how many turns did you back off, and how many turns remained unused when the model landed?  This is critical information that you need to record and analyze after each flight.  It tells you a lot about how well your rubber motor is sized for the prop, air frame, and trim you are currently using. "

I was able to coach our middle school teams WS squad to a 4th place at state and the High school teams Copter to a 6th place finish at state, but I definitely feel like this is a piece of information I could understand better.  We really worked on trimming and winding and matching the prop to the rubber, but much was trial and error.  Any additional details which would accelerate learning for next year would be appreciated.

Thanks!
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ceandra
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« Reply #84 on: March 21, 2017, 09:54:45 PM »

Foosier:

There are other posts referenced on the hysteresis of rubber. But the basic story is, lets say you are shooting for 0.25 oz-in of torque. You can wind up to this, and might get say 1500 winds. Or you can wind well past this torque, to near breaking, to say 2500 turns, and then back off say 100 turns and be back at 0.25 oz-in torque, with 900 more turns in the rubber. The winding torque is much higher than the unwinding, and so if you stop on the way up, you miss out on a substantial amount of energy that could be stored in the rubber. On heli's, you only unwind enough to prevent stick warp/breakage or slamming into the ceiling, typically only 30-50 turns. The numbers above are example only, but give you the idea. So wind it hard, then unwind to desired torque. Note also that you want to stretch the rubber while winding. We stretch about 7X the original length, turn about 50-60% of the turns at full stretch, and then walk in while watching the torque. This helps get a lot more winds as well. As does lube.

Generally, if you use up all the rubber (no turns left) in the air, the plane stops flying and loses altitude quickly. Again, generally, people have found that if you use up all the rubber, especially with a low ceiling, you have too thick a rubber, and you are not optimized for time. While the mileage may vary, some have said that having about as many winds left at touchdown as you took off on winding leads to a balanced flight. A full row of knots probably means too thin a rubber. No winds, too thick. Outside of that, optimize based on the stopwatch. If you only have one rubber width, and it is reasonably close (say 1/16" for this year's prop), then you can play with pitch. No winds? Add pitch. Too many winds? Take off pitch.

Still a lot of trial and error, but recording the winds left (or at least an estimate) can help you understand the relationship between winds left and the stopwatch. You can estimate winds by recording "1/4 row of knots" etc., and still get a relationship. Note that also if you change the trim of the plane, you may have to change the rubber (more or less winds left). The winds late in the flight contribute to cruise and letdown. If the rubber is too thin, then late winds cannot hold the plane up, and it lands with too many winds. If too thick, the rubber has too much power for a gentle letdown, you use it up too much in cruise, leaving nothing to help in letdown. A thinner piece would have enough for letdown, and have more total turns (more time).

Use your "additional" fields of your log book for value. Don't stop at 3 extras. My team records, among other things, CG location, decalage, prop number, prop pitch, prop flex (if flaring), peak torque, launch torque, backoff winds, altitude, first lap altitude, rubber width, rubber length, etc. While some (CG, Decalage) may not change much, you may find over the months you did change, and getting back to that "magical" flight is impossible if you did not record the nearly-stationary items as well. Or figuring out what you did change that now put you in the magic. Data is power!

Chuck
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calgoddard
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« Reply #85 on: March 21, 2017, 10:35:05 PM »

Foosier -

Ceandra has given you good information.

If an indoor model airplane lands "dead stick" (no turns left in the rubber motor) the motor width is too big.

If an indoor model airplane lands with too many unused turns, the motor width is too little.

You will read a lot about "matching rubber to prop."  This is the process of determining the appropriate width of the rubber motor to max the flight time.

Experts go by length and weight of the rubber motor, and not by width. This is because the density of the rubber, and its thickness, vary along its length in a given  batch of rubber, whether it be TAN II or Tan Super Sport, for example. Also, it is not possible to strip rubber to a target width with great precision over the entire length of a rubber motor.    

Ceandra stated "While the mileage may vary, some have said that having about as many winds left at touchdown as you took off on winding leads to a balanced flight." Change - - balanced - - to "close to maximum duration".

Winding rubber motors for SO helicopters is an entirely different endeavor. You can't win the event with a no-touch flight in a typical HS gym. The helicopter has to plant on the ceiling in order to have a chance to win. Backing off winds is not normally done in the SO helicopters event.

  

« Last Edit: March 21, 2017, 10:54:08 PM by calgoddard » Logged
Olbill
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« Reply #86 on: March 21, 2017, 11:21:45 PM »

To expound a bit on the preferred way to measure rubber - length and weight - there's actually more to this issue than minor variations of rubber strip thickness and density. All rubber batches that I've come in contact with vary in thickness of the strip. I'm not talking about the width of the strip - whether it be 1/8", 3/32" or whatever. The thickness of rubber strip in the other direction varies by a significant amount. I have 3/02 Tan II rubber that is .039" thick or sometimes even less. I have 5/99 Tan II that measures .047" or more. Just using these two number you come up with a variation in thickness of over 20% for the larger compared to the smaller. That means if one person is flying 1/8" wide rubber that is .047" and another is flying 1/8" wide rubber that is .039" then the first person's motor will be 20% heavier per unit length than the second person's.

Almost every time I go flying some person will ask me what width motor I'm flying. My usual answer is "I have no idea". And this is the actual truth.
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mkirda
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« Reply #87 on: March 23, 2017, 02:44:06 PM »

To expound a bit on the preferred way to measure rubber - length and weight - there's actually more to this issue than minor variations of rubber strip thickness and density. All rubber batches that I've come in contact with vary in thickness of the strip. I'm not talking about the width of the strip - whether it be 1/8", 3/32" or whatever. The thickness of rubber strip in the other direction varies by a significant amount. I have 3/02 Tan II rubber that is .039" thick or sometimes even less. I have 5/99 Tan II that measures .047" or more. Just using these two number you come up with a variation in thickness of over 20% for the larger compared to the smaller. That means if one person is flying 1/8" wide rubber that is .047" and another is flying 1/8" wide rubber that is .039" then the first person's motor will be 20% heavier per unit length than the second person's.

Almost every time I go flying some person will ask me what width motor I'm flying. My usual answer is "I have no idea". And this is the actual truth.

And also why loop length and weight are more important things to know.

Last week I knocked together a simple SO model. I wanted to see the times I could get. I built it heavy. Time was well over 3:30 in a 42' ceiling.
Then I discovered that it was still significantly underweight. I glued on a penny, then added some more clay.

Next flight, the prop broke on landing.
I figure that I will laminate them with fiberglass next time. I can take off some clay.
Not sure I will have it with me for West Baden.

Regards.
Mike Kirda
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JasperKota
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« Reply #88 on: March 25, 2017, 12:46:29 PM »

Apologies for the late reply! In regards to the 123 flight, there were no turns left at landing, and I backed off around 12 turns with a 15:1 winder.
The last practice session frustrated me a bit. Last week, I was able to achieve a no-touch flight backing off to .32 torque. Yesterday, using the same plane with no adjustments made, and backing off to .3 torque still resulted in crashing into the ceiling

During one of the crashes, the wood in front where the propeller was attached snapped, and I glued it back with CA. After testing with other planes, I went back to this one and switched out a stock trimmed down 15 cm ikara propeller for a trimmed flaring blade propeller. 1875 winds, and I backed off 75 winds to .26 torque. 117 seconds, with around 100 winds left after landing. Here is the flight: https://www.youtube.com/watch?v=M0q2AFRmabU

Something I noticed was that the circles were much, much larger (larger than I would like) than previous flights. Note that this is the same plane as the 123 second flight I posted last week. Does the flaring blade propeller also make the circles larger, in addition, to make the plane climb slower? While building the plane, I glued the propeller hook so that it was slightly turned towards the left, which aids in turning. I suspect that after the break, I may have glued the hook back on improperly. Plane still has rudder deflected 1/4" to the left and left stabilizer around 1/2" higher than the right, with a wing warp (left TE slightly lower than right). Should I add more rudder deflection and tilt the stabilizer more?

I was able to test the new Vanguard P-18 I received in the mail and it was very simple to build. Best flight so far is merely 82 seconds, but I haven't flown it much yet.

A bit disappointed, but I'm looking forward to experimenting with the flaring blade prop more and seeing if I can improve my times, as well as consistently fly above 2 minutes without hitting anything. The ceiling is 23 feet, though, and I hope the venue at states to be higher.

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Olbill
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« Reply #89 on: March 25, 2017, 08:51:31 PM »

Don't get discouraged about the different power requirements on different days. You have to figure this out every time you fly. My method is to pick a very conservative number for your first flight each day and then adjust from there. Everything can make a difference = air temp, barometric pressure, motor variations - you name it. That first flight is going to determine your direction for the rest of your flying session.
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calgoddard
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« Reply #90 on: March 29, 2017, 09:14:08 AM »

Bill -

In my posts I try to give some context and include extra information so that people with various skill levels might benefit from the same.  This is one of my excuses for writing long posts.

I was privileged to get some mentoring from the late Cezar Banks when I got back into this hobby around 2005.  I remember his disgust when I talked about the width of the rubber motors that the students I was helping were flying with. He was a patient teacher and a master in a number of indoor duration events, such as F1D and Penny Plane, as you well know.

I am a convert to the length and weight standard for measuring indoor rubber motors.

I have a question for you.  Let's say your rubber stripper has previously been adjusted to strip rubber for an A-6  motor and you need to strip rubber for a Limited Penny Plane motor.  By way of example, my records indicate good results flying my third Limited Penny Plane (LPP3) with a 2.17 gram rubber motor approximately 36 inches long (strand length) made from TSS 10/05 rubber.  Assuming this scenario, how would you adjust your rubber stripper and produce a rubber motor of this size?  I am still struggling with the concept of completely disregarding the width of the rubber motor.  It seems to me that the stripper has to be adjusted to strip rubber to some initial target width, e.g. 0.100 inches in this example, so you can measure the results and re-adjust the stripper to produce a rubber motor having the desired length and weight.

For many years I have used a rubber stripper that I purchased new from Ray Harlan. I believe that I have developed a reasonable skill set for using that tool in the best manner.  At the risk of incurring the anger of experts, I still resort to using a digital caliper that I bought from Ray Harlan when I am making up rubber motors for indoor flying to give me reference widths. 

I also have many flight logs that indicate the max winds, back-off winds and launch torque for my LPP3 motors flying in our local indoor Cat I site. However, as you are well aware, winding for max indoor duration is a whole different subject covered extensively elsewhere on this site.

Thanks in advance for your words of wisdom.  I have learned a lot from your posts on Hip Pocket Aeronautics.  I still remember you showing me the best way to tie a rubber motor when you were flying in one of the Tustin blimp hangars around 2011.
 
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Olbill
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« Reply #91 on: March 29, 2017, 09:37:29 AM »

I start out by cutting several 1" lengths of rubber and a few 2" lengths. I run a 1" piece thru my stripper, weigh it, and then make whatever seems like an appropriate adjustment to the stripper. Then I repeat the process until the weight of the 1" piece is withing a milligram or two of my target weight. Then I strip a 2" piece as a check. If that looks good I cut off a length of rubber a couple of inches longer than what I need for my final motor and strip it.

I'm usually making motors from several different batches of rubber in order to find which motors are best for whatever I'm trying to accomplish. If I switch to a different batch then I repeat the process above. Even if you don't switch to a different batch of rubber you may find that the thickness of the strip changes enough to require adjustments to the stripper. Of course this is extremely critical for F1D where every milligram of rubber is important.

I think Leo and Kang have ways that may be easier and/or more accurate but I'm old and tend to stick to what I'm used to.
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calgoddard
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« Reply #92 on: March 29, 2017, 10:25:56 AM »

Bill -

Thanks for explaining your rubber stripping procedure.

In my hypothetical scenario, the stripper was previously adjusted to strip a rubber motor for an A-6.

When you start stripping sample 1 inch and 2 inch segments of rubber, in the process of getting ready to strip a rubber motor for an LPP, how do you initially determine how much to adjust your stripper?  

Kang always seems to have a big supply of rubber motors ready to go. They are in tiny manila envelopes with notations written on the same, as I recall. I have never seen him strip rubber and make up rubber motors.  I'll have to discuss this with him the next time I see him.  

I realize that much more accuracy is required in making up rubber motors for an F1D.
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mkirda
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« Reply #93 on: March 29, 2017, 11:25:22 AM »

I'll tell you what I do.

For SO I would cut a length slightly longer than the desired length, then weigh it. I now have a reference weight per length.
Then determine the percentage width I need to hit my target weight.
Use a non-spring loaded micrometer to get the width. Multiply that by the percentage determined above.
Adjust the stripper to that width. Test it with some sacrificial rubber. Adjust until you get it right.
Then strip the piece you cut.

It should end up within just a few milligrams of the target.
As with everything, practice makes perfect here.

As density changes over the length of the rubber, if you just strip it to that width, you'll end up with a bell curve around your target length.
Say it is 19" loop desired, you'll end up with +/- 1/2" roughly by not measuring each length.

I do have a spreadsheet that calculates this. I also have a version for my iPad. They are quite helpful tools for this.

Regards.
Mike Kirda
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Olbill
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« Reply #94 on: March 29, 2017, 12:06:33 PM »


When you start stripping sample 1 inch and 2 inch segments of rubber, in the process of getting ready to strip a rubber motor for an LPP, how do you initially determine how much to adjust your stripper?  
 

I just guess at it.
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jdpsloflyer
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« Reply #95 on: March 30, 2017, 02:18:52 PM »

Foosier -

Ceandra has given you good information.

If an indoor model airplane lands "dead stick" (no turns left in the rubber motor) the motor width is too big.

If an indoor model airplane lands with too many unused turns, the motor width is too little.

You will read a lot about "matching rubber to prop."  This is the process of determining the appropriate width of the rubber motor to max the flight time.

Experts go by length and weight of the rubber motor, and not by width. This is because the density of the rubber, and its thickness, vary along its length in a given  batch of rubber, whether it be TAN II or Tan Super Sport, for example. Also, it is not possible to strip rubber to a target width with great precision over the entire length of a rubber motor.    

Ceandra stated "While the mileage may vary, some have said that having about as many winds left at touchdown as you took off on winding leads to a balanced flight." Change - - balanced - - to "close to maximum duration".

Winding rubber motors for SO helicopters is an entirely different endeavor. You can't win the event with a no-touch flight in a typical HS gym. The helicopter has to plant on the ceiling in order to have a chance to win. Backing off winds is not normally done in the SO helicopters event.


Cal's summary is about the right level of technicality for me, and I expect most SO coaches.  I buy pre-stripped rubber of varying widths that span the size that came with our kits so we can test each size with our planes and the stock prop.  Variables for us are plane weight, trim, rubber size, prop, and #winds.   Although we try to get plane weights as close to the spec, some are heavier due to the student's building skill, and how many times a plane has been repaired.  This affects the width of rubber to some degree to get the best duration for that plane.

After the regional meet, we are now testing flaring props, improved winding techniques, and stressing each rubber motor width on a torque meter.  This is the first time I have demonstrated torque and winding relationships.  Winding to max torque and backing off while watching the meter was a learning experience for all of us, and added to our knowledge of how to get the most out of rubber.  With the few practice sessions we have left, I hope to get the kids to understand how to adjust the flight altitude using back off turns,  Our gym is 23', State will be about 20'  We will have to learn how many back offs it will take to fit the gym we have and then to reduce the altitude for the State meet. 


It does not matter the length of the loop for us.  Each width equals a typical loop length for the 1.5g spec.   I think the technical issues here are beyond the abilities of myself and typical SO students.

Jerry
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Olbill
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« Reply #96 on: March 30, 2017, 03:30:12 PM »

You wouldn't want a nitro burning 1000 hp motor in a mpg challenge event. Motor length is extremely important.
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calgoddard
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« Reply #97 on: March 30, 2017, 05:54:39 PM »

Bill -

Thanks for Reply #94.

Your guess is probably a pretty good estimate.

jdpsloflyer -

I think Bill briefly touched on the following point recently in one of his posts, and it bears emphasizing.

Students can practice, test, record, etc. and determine that rubber motor X wound to Y turns and backed off to Z torque will cause model No. 1 to reliably climb to 20 feet.

At the WS competition, using all the above on official flight No. 1, the No. 1 model climbs all the way to 20 feet, keeps climbing, hits an obstruction at 23 feet, and the flight ends prematurely.  What happened?  Temperature changes affect the ability of the rubber to store and yield energy.  They also change aerodynamic drag.  Changes in humidity and barometric pressure also affect the way very light models fly.

WS competition is particularly challenging because there is only time to do two official flights in the 8-minute Flight Period.  There is no time for practice flights.

By way of comparison, when I compete in our local Penny Plane event I have four hours to log three official flights. My score is the total of my three official flights.  I have plenty of time to conduct trim flights and play around with different rubber motors.  My better indoor models never seem to fly exactly the same way at each contest.  This is due to the factors mentioned above.

Here is another thing to consider.  Variations in humidity can cause balsa wood to shrink or expand, albeit in very small amounts dimensionally. Nevertheless, this can affect the trim of a model. For this, and other reasons, I prefer CF spars.

The best WS fliers are experienced and make good adjustments for the second official flight.  Since only the longer of two flights counts, the students get a mulligan.          


« Last Edit: March 30, 2017, 06:23:39 PM by calgoddard » Logged
JasperKota
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« Reply #98 on: March 30, 2017, 10:01:51 PM »

New personal best with a flaring blade prop today at 2min 9 seconds Smiley it was a clean flight, and there's still about a foot to climb before hitting any obstructions. The states venue is also a foot higher than my usual site which I hope will garner me a few extra seconds.

I'm very glad I invested in a torque meter - no hit flights are much more common now, and I'm hardly worried about breaking rubber. I did have a couple breakages with rubber wound to around 110 winds when it handled 140, but I made the mistake of not paying attention to the meter while winding. I suspect I was stretching too far back, though, and the rubber was pretty old. Lubricating after each wind has lengthened it's life span tremendously though.

Tested with some thicker rubber, though I believe it's a bit too thick after landing with a dead stick and descending very rapidly. Approximately how many winds can a 1.4g (minus two o-rings) .072" take? I was winding 110.

With a flaring blade prop and my usual .065 rubber, the plane lands with many winds left, so I do need to go thicker.
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Olbill
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« Reply #99 on: March 30, 2017, 10:57:25 PM »

.072" is not usable information. The motor length would be usable information.
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