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Author Topic: Nationals Trial Event  (Read 255 times)
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ceandra
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« on: April 18, 2017, 10:46:20 AM »

I have been asked by our coaches to look at getting our HS kids to try the electric Wright Stuff trial event.

Since we only have a month, have to move quickly. Anyone have any starting points for capacitor/motor? Supplier, or salvage from some equipment? Any pointing in a decent starting direction would help. Plane itself should not be a big deal to get something together in time.

Thanks
Chuck
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Rossclements
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« Reply #1 on: April 18, 2017, 02:31:56 PM »

Talk to Fred Rash, He is probably the most knowledgeable person on the subject.

Ross
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ceandra
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« Reply #2 on: April 18, 2017, 03:18:46 PM »

I did find a little in a prior proposed trial event. Supercapacitors are available from Digikey and Mouser, generally 5F capacitors have a max voltage of 2.7V if the restriction is 3V max label. I have not found any that are labelled 3.0V. Unfortunately, this means simple charging from dry cells may not be possible, as exceeding this voltage for more than a second is not allowed (per the spec sheet). The rules say the capacitor may not be charged with more than 3.0V. Not sure if this means the input to the charger (if we used a digital charger like those used for LiPo's), or the max charge into the capacitor. I guess it would be easier/safer if they allowed a 5.0V label on the cap, but limited the voltage at launch to 3.0V. Then charging could be as simple (I think) as connecting to two series dry cells.

Motors, with and without gearboxes, are available at Plantraco:

http://www.microflight.com/Online-Catalog/Motors/GB05-Gearbox-with-motor

Should be interesting to try things out and see what works!

Chuck


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frash
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« Reply #3 on: April 18, 2017, 10:39:01 PM »

NFFS Sympo 2011         Capacitor-Powered Free flight and the Science Olympiad – Chuck Marcos

If you have a NFFS 2011 Sympo, look for Chuck Markos article. He got me interested and he and I flew these cap planes one year at the USIC.

Use a 10F, 2.7V capacitor. Most electronic supply houses have them. There are about 3 or 4 versions of 7-mm dia "pager" motors and at least one good 6-mm dia motor that could be direct drive or geared. The TriTurbo prop is good for 7-mm motors or geared 6-mm motors. BSD Micro RC sells most of this stuff except for capacitors. Trial Event Capacitor Wright Stuff specified charging with 2 AA alkaline cells. I built 3 of Chuck's design, but no complete airframe survived to today. I literally made a few hundred flights, some to learn something but most were simply recreational flying. I did not try ROG much which was specified for the High School (Div C) event since I have only mentored Div B or Middle School.

I really enjoyed this trial event and hoped that it would become an official event.

I'll try to scan and post Chuck's article. I know that I have his blessing without asking. NFFS probably will not protest.

Make a tissue rectangular tube to plug in the tail boom. Simplifies storage and repairs and swapping parts.

Fred Rash

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ceandra
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« Reply #4 on: April 18, 2017, 10:42:24 PM »

The trial event this year is limited to 5F capacitor, 7g min weight, and does not ROG. But, still interested to see article and learn from past efforts!

Chuck
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calgoddard
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« Reply #5 on: April 19, 2017, 06:58:20 PM »

I am sorry to learn that the powers at the SO National organization are pushing e-Wright Stuff again. I thought this event was dead due to the following reasons elloquently explained by an expert indoor flier, LeoP, a few years ago:

"Having started indoor flying by being a coach for SO Wright Stuff, I , too, would be glad to see Wright Stuff back in the event list.  However, I am of the very strong opinion that the only power used should be rubber and not electric in any way.  The reason I feel this way is because of fairness issues.

When the capacitor powered planes were first proposed, I built several and ran a great deal of tests.  I found that the nominally specified capacitors could differ in capacity (which equals flight duration) by nearly a factor of two depending on manufacturer and manufacturing tolerances.  This led to some (richer?) SO teams buying a large number of capacitors and selecting for the ones with the greatest capacity.  I had already seen a similar thing in the AMA battery powered indoor class (both free flight and radio controlled) as small LiPo cells of the same mAh rating could vary by 50% or more in storage capacity.  I think this makes for very unfair competitions.

Some will say that the same is true for rubber powered planes as there is a difference between poor and excellent rubber.  However, the difference in energy storage capacity between the very best rubber (Tan II 5/99 or 3/02, for example) and the currently available Tan Super Sport is less than 20% (and more like less than 10% for the better batches of the current Tan SS).  A well built, tuned, and flown rubber powered plane using Tan SS will be competitive.  However, for electric powered planes, only those students who have selected the best storage cells or capacitors from a large number will be competitive at the state or national level.  I think this unfair and biased toward the richer schools.

LeoP"

I have a great deal of respect for Leo's opinions.  He is very rigorous in his application of science and engineering to our hobby and has a great deal of experience.  

Let me just add that in my personal experience, May 99 TAN II rubber is probably only about 5% better in terms of energy storage capacity than the better batches of TSS rubber that have been sold during the last few years since Leo voiced his opinions set forth above. Some outdoor fliers say that June 2016 TSS rubber is as good as any batch of TAN II rubber ever made. Even if May 99 or March 02 TAN II rubber are still 5% better than current TSS rubber, it is very unlikely that WS fliers will be able to obtain any of the former.  
« Last Edit: April 19, 2017, 07:16:38 PM by calgoddard » Logged
frash
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« Reply #6 on: April 22, 2017, 08:20:20 PM »

Science Olympiad Nationals Trial Event

NFFS Sympo 2011         Capacitor-Powered Free flight and the Science Olympiad – Chuck Markos

Now posted in the HPA Plans > Miscellanous > Miscellaneous Articles for all those who are interested. At least 75 downloads thus far.

Yes, the rules have changed somewhat since the original article by Markos.

Fred Rash
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