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Author Topic: SO Wright Stuff 2022  (Read 1202 times)
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Olbill
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« Reply #25 on: October 15, 2021, 09:49:43 AM »

 More revisions coming soon. I'm close to finishing a model.
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ceandra
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« Reply #26 on: October 15, 2021, 12:03:11 PM »

Cal:

I believe FFM is shipping, at least limited. Sometimes his website updates are a bit late.

Coach Chuck
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Olbill
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« Reply #27 on: October 16, 2021, 03:16:11 PM »

I've uploaded the latest and hopefully last revision (r.2) of the 2022 Finny plan. I added an as built weight chart for how my test model turned out. First flights should be next Saturday Oct. 23.
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Olbill
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« Reply #28 on: October 17, 2021, 03:45:10 PM »

Finny 2022 ready to fly.
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bjt4888
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« Reply #29 on: October 17, 2021, 08:42:30 PM »

Bill,

Very nice.

My students’ first build session is next Saturday. Should be fun.

Brian T.
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« Reply #30 on: October 22, 2021, 02:30:04 PM »

I debuted my Stinger for this year's rules at USIC and the flight times were excellent. It trims very easily, and flies well enough to be fun. This year's rules will bring smiles to many faces as they provide a context for very nice flying airplanes in general. Lots of room for experimentation too!
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bjt4888
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« Reply #31 on: October 22, 2021, 05:03:13 PM »

Josh,

Yes, definitely a nice flying airplane. Thanks for offering such nice kits. I’ve sent students your way.

Brian T
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Olbill
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« Reply #32 on: October 23, 2021, 05:15:51 PM »

The Finny did 3:20 no touch in a Cat 1 site today. This was on high quality rubber b/c I didn't feel like making TSS motors. A ceiling hit on an earlier flight lost about 10' of altitude so moving the CG forward a little might be a good idea.
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Little-Acorn
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« Reply #33 on: October 23, 2021, 08:25:45 PM »

The Finny did 3:20 no touch in a Cat 1 site today. This was on high quality rubber b/c I didn't feel like making TSS motors. A ceiling hit on an earlier flight lost about 10' of altitude so moving the CG forward a little might be a good idea.

Bill, that's great! (What's a Cat 1 site?)

What manufacturer and size rubber motor did you use?

My students will start building this one next week. Weighs in at 7.76 grams without rubber motor. A little ballast in the right place...  The aluminum tube prop hanger is there to allow right-thrust, up-thrust etc. adjustments. Smiley
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Olbill
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« Reply #34 on: October 24, 2021, 04:13:34 PM »

Cat 1 is 8m maximum. I don't know the actual ceiling height but I believe it is about 25' on the high side of the sloping ceiling. The attached photo gives a pretty good idea of the site.

3/02 rubber 12" long x 1.45g. 1500 turns in. Max torque .7 in-oz. Backed off 180 turns to a launch torque of .31 in-oz. I forgot to get the turns remaining but it looks like about 300 using the rpm from previous flights to calculate.

I just used F1M motors that I had on hand since I probably won't ever fly F1M again. TSS rubber probably wouldn't do as well but with enough work it might. I think I only made 3 or 4 flights to find the no touch setup.

Also maybe of interest I set up the initial incidence adjustment by gliding with a lump of clay for the prop and another lump of clay for the motor. After adjusting for a nice glide I put the prop and motor on and tried a low power flight. This looked pretty good but when I added more power the model started diving. I raised the wing LE about 1/8" for the final trim the model flew with for the rest of the day. This was a good setup for no touch flying but for ceiling banging I'd probably move the CG forward a little and use more incidence in the wing.
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bjt4888
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« Reply #35 on: October 26, 2021, 06:58:21 PM »

Bill,

Thanks for the flight data. 3:20 no touch is good flying for this year's rules.

Would you mind sharing the prop pitch you are using? Looks like a prop blade chord of about 2".

Here's a picture of the results of the first in-person build session in quite awhile. It's hard to see, but there are four build stations with most of the flying surfaces finished and covered.

Does the winglet shape and structure look familiar?

Another session this Friday to finish up for the first team. The other three high school teams will be building each Saturday for the next three weeks.

Brian T.
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Olbill
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« Reply #36 on: October 26, 2021, 11:54:19 PM »

Nice looking work!

I used the big Ikara with carbon rod hub. Blade area behind the spar was removed. Pitch 12.6.
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bjt4888
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« Reply #37 on: October 27, 2021, 02:05:20 PM »

Bill,

Thanks. The wing and flying surfaces in the foreground were built by one of my students that attended the Indoor Nats in Pontiac this last Summer. He flew LPP and CLG at the Nats. Since hes's an experienced builder now, he's a little ahead of the others. All the students did a nice job so far though and two are complete newbies.

Wow, seems like pretty low pitch on your prop. I'm guessing the flaring is pretty soft maybe.

Thanks again for the great design and flying data. We have our first flying day on November 7.

Brian T.

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calgoddard
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« Reply #38 on: October 27, 2021, 08:42:04 PM »

Bill -

I have small quantities of some of the better batches of TAN II rubber that I reserve for personal flying in LPP and A-6 contests.

It is definitely better for indoor flying than any batch of TSS rubber I have used.  For these two indoor classes, I would say that I can get as much as 10% longer flights in a Cat I site, on average, with the same models.

TSS rubber, particularly some of the later batches, seems to yield much higher torque after winding hard compared to TAN II rubber.  Thus TSS rubber is just fine for outdoor flying with F1G (coupe), P-30, FAC models etc. We don't back off winds in outdoor flying for obvious reasons. When I wind an indoor TSS rubber motor hard and back off turns, it doesn't seem to deliver the remaining energy as well as a similarly wound TAN II rubber motor. 

I wish I could quantify this better for you, Brian and Chuck.  I can envision a test set up where a strain gauge is mechanically coupled to a rear hook on a motor stick with a prop.  The motor stick would be mounted to the outer end of an arm whose inner end is pivotally mounted on a tripod. A prop and a wound rubber motor connected between the prop shaft hook and the rear hook would propel the motor stick in circles to simulate air flow during a flight.  The output of the strain gauge would be electrically connected through a suitable interface to a PC and software would display a graph of the torque varying over time.

Rather than spend hours setting up such a test rig, I just let my stop watch be my guide.

As you are well aware, this discussion is moot because the manufacture of TAN II rubber ceased around 2002. Even if you can find it, the per gram price of a good batch of TAN II rubber is very high, and you don't know how it was stored.  I guess some students at Nationals might have access to May 99 TAN II but I think that would be very unlikely.  Proper construction, optimum trimming, building to minimum weight, and optimum winding will likely determine the winner amongst the best WS competitors, and not the batch of rubber. Of course there is always the luck factor in any free flight contest. But as they say, you make your own luck.

In regard to the best best batch of TSS rubber for indoor flying, in my experience 10/05 TSS rubber has produced the longest flights.  In my experience, 9/09 TSS rubber has produced the longest flights outdoors. When flying outdoor models, thermals and wind conditions make a far greater difference than the batch of rubber.
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Olbill
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« Reply #39 on: October 28, 2021, 01:16:47 AM »

My best Cat 1 WS flight of 2015 (which I believe used 2 grams of rubber and a similar airframe) was 3:30. That was done on 1/15 TSS. I think something in that neighborhood should be possible this year with TSS.

That 3:20 flight probably didn't ever go much above 20'.
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ceandra
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« Reply #40 on: October 28, 2021, 11:32:34 AM »

Cal:

While we see similar in F1D, I think the SO planes are heavy enough that little difference is seen. We have only used TSS for SO, and have had good success with it. We have seen slight differences on batches, but overall the rubber is fairly consistent.

It would be easy to start chasing rubber vintages, and TII rubber, but without working the basics of trim, balance, build, and prop/rubber matching, the differences would not produce a winner that was not a winner to begin with. We even do initial testing of our F1D's with TSS, saving the good stuff for closer to competition time. On those lighter planes, the good vintages of TII make a huge difference in the later portions of the flight.

My win in LPP at Nationals this year was with TSS, on a Gowen Carbon Penny, using a flaring prop with basswood spar. We are finding that this year's WS plane uses the same range of rubber loop sizes as our LPP's, though we are still on our first prop. Most years we make at least 25 props!

Coach Chuck
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« Reply #41 on: October 31, 2021, 04:22:13 PM »

Got a 3:16 flight out of my hybrid-wing plane this morning, but only 2:32 of it should count. Launched from a baseball infield outdoors, but a slight breeze carried it over the right-field fence, still climbing... and from there the land slopes down to a road. The plane went up maybe 40-50 feet above launch height, circled for a while, and began descending. After 2 min 32 sec it was back down to the same height I launched it from, which should have ended the flight... but the plane was still 20-30 feet above that road at the bottom of the hill, took another 44 sec to get all the way down. So realistically it was only a 2:32 flight, but I'm pretty happy over that.

That was with a .075" Tan Super Sport(TSS) rubber motor with 1,500 winds. Next task will be to try a .072" motor, and even a .069" motor, in hopes the plane can be adjusted to climb more slowly, to only 20-24 feet (the ceiling height of our local school gym), while saving enough extra energy to circle at that height for a longer time before descending to the floor.

But wishing won't make it so. Gonna take a lot of trying, adjusting, and re-motoring before it actually does those things - if it ever does them.

Video at https://youtu.be/Ip8pm0h68H4  Plane launches at 0:21. Becomes more visible around 2:40.

Apologies for the poor camera work, sometimes blurry, sometimes clear, sometimes can't see the plane when the sky is the same light-grey color. Read the notes in the Youtube video. Good thing tournaments don't depend on video quality, or we'd come in dead last every time.
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bjt4888
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« Reply #42 on: October 31, 2021, 07:09:48 PM »

LA,

Nice job. One quick note. Climb height for any particular propeller type, propeller pitch and trim combination is usually managed by launch torque not by going to thinner rubber. Thinner rubber might warranted if landing with almost zero turns remaining.

Also, I’d recommend winding your motor more aggressively. .075” rubber (which is typically about .050 g/in and should produce a 14” loop if exactly 1.5 grams total and using two black rubber o-rings) should take 1,750 turns even if wound moderately (this is 85% of breaking turns using the John Barker equation). The teams I coach will wind to 85% plus for every flight except for the first “trim safety check flight”. Always winding fully, and then backing off turns to desired launch torque will give data that is easier to analyze.

Brian T

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Little-Acorn
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« Reply #43 on: November 02, 2021, 12:03:46 AM »

Thanks, Brian. I just threw in a bunch of winds to see if the plane would fly with them, and not enough to break things. Wasn't trying to max it out.

Now that the plane is acting like (more or less) a real plane, I made a torque meter today out of scrap Melamine shelf wood and Midwest 1/4" plywood as a first step to getting serious in tuning and adjusting it. Same basic principle as several other torque meters I've seen, a slim spring-steel wire in a rigid tube, with one end of the wire anchored and the other glued and bent into an aluminum tube hook. Put a dial face around the hook end, and a pointer glued to the hook, which goes through a frictionless (almost) bearing. Then calibrated it by hanging weights on a round pulley of a certain diameter and measuring the angular deflection of the pointer.

Considering my inexperience at this, can I get you all to indulge me with a "stupidity test"? I put a 1.5 gram .075" motor (incl. one O-ring) on the meter and wound it with 1,000 winds. I did NOT back it off after the windup, unlike what I'd do with an actual flight. Held the winder and rubber motor parallel with the meter axis throughout and eyeballed carefully to eliminate parallax. I got a torque reading of 0.265 in-oz after those 1,000 winds. This motor was almost new - it had been wound to 1,000 winds one time previously. Obviously nowhere near its max capability.

Those of you with accurate torque meters, if you have such a motor (.075" wide TSS, one loop, 1.5 grams) lying around, can you do the same to your motor? What torque reading do you get? Remember, after winding 1,000 winds, do NOT back off a hundred or so winds as you would normally do. Take the reading as soon as you've cranked the 1,000th wind.

Is your reading anywhere close to mine (0.265 in-oz)? Mine could be WAY off - this test is to reveal if I did anything stupid in building and calibrating this critter. Wouldn't be the first time. I'd like to know if I'm anywhere within the right ballpark.

Thanks, all!
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Olbill
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« Reply #44 on: November 02, 2021, 12:50:00 PM »

I don't have an answer but if you want to calibrate your meter you can attach an arm to the meter hook and hang a weight from it. A one ounce weight on a one inch arm would give you 1 in-oz of torque. Then intermediate values will be proportional to the one in-oz deflection.
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bjt4888
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« Reply #45 on: November 02, 2021, 02:11:20 PM »

LA,

I have a 1.5G loop of .051 g/ in, which is approximately .075” that I can test for you in about an hour.

Bill’s method for checking calibration is, of course, best, but I have always used the “wire torsion” calculator to determine length and thickness of torque meter wire elements. All the meters I’ve made calibrate very close with this method.

Brian T
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« Reply #46 on: November 02, 2021, 03:46:18 PM »

Yes, Bill, that's how I calibrated it. Just want to know if I screwed anything up.

Brian, thank you! I'd like to compare my experimental reading with your known-good one.
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« Reply #47 on: November 02, 2021, 07:53:07 PM »

LA,

Here's my winding result. 5/2014 Tan SS .051g/in 14.25" loop with two small plastic o-rings; total motor weight 1.483 grams. .051 g/in is more like .0768" width if you use the average density of 1/8" strip of .083 g/in (average based on typical 1/8" strip weight of 1 gram/foot; however, when measuring density of actual 1/8" strip "blanks" before stripping, I have lots of data that shows variance from .076 g/in to .085 g/in; usually, contiguous blanks are a little closer in density, but still show as much as 5% variance).

Stretch to 6x relaxed length (about 84" stretch), wind in 38x15 turns at full stretch and walk in for remainder of 67x15 (1,005 turns), finish winding with motor about 15" long. Torque was 0.32 inch ounces. This was the third use of this motor. For the fourth use of the motor, I wound to about 84% of maximum (John Barker equation project breaking turns at 2,065) or 1,725 turns; 65% at full stretch and remainder while walking in torque was 1.0 inch ounces. I would guess that this motor could take about 1.4 - 1.5 inch ounces before breaking.

So, your result sounds logical. Could be differences in actual motor density, vintage, etc. My memory of 5/2014 is that it is a little on the "stiff" side. Best to measure motors in density. Width is not really measurable. Overall motor weight, minus weight of o-rings, divided by length of rubber (2x loop length plus about 0.3" more rubber stored in the knot). This is easy to measure and more accurate.

Brian T.

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Olbill
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« Reply #48 on: November 03, 2021, 09:52:47 AM »

This may or may not be pertinent to this discussion but here's a tip for low ceiling flying that I've never seen talked about before.

When you're finished winding and are backing off turns to reach a target launch torque, the motor will have some stored energy that doesn't show on the torque meter. The behavior of rubber is so complicated that I won't attempt to describe how this happens, but it is easy to see and extremely important for setting the max altitude of the model.

My technique for dealing with this is to back wind until the desired torque is reached. Then I thump the motor with my finger several times. After each thumping the torque will go up. Then I back wind some more until I reach the target torque again and repeat the thumping. I repeat this until the torque doesn't change any more when I thump the motor.

I'm sure there are other valid approaches to setting launch torque but this is mine. Using this method and a digital meter I can usually hone in on a no-touch launch torque in 3 or 4 tries.
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« Reply #49 on: November 03, 2021, 10:41:51 AM »

Bill -

I have never heard of your thumping technique before.  Intuitively it makes sense that it would improve the chances of consistently achieving a high no-touch flight in a Cat I flying site.  Thanks for telling us about this.

It has also been recommended to massage the knots of the wound rubber motor and spread them out uniformly.

Of course the final back-off turns should be made when the wound rubber motor extends between the winder and the torque meter the same distance as the hook-to-hook length of the model.
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