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Author Topic: The sub 400mg EZB plunge!  (Read 10602 times)
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dslusarc
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« on: December 28, 2012, 11:51:36 AM »

I have built many EZBs over the years. Until recently, the lightest I have built was about 450mg back in 2000 that I flew in the USA vs Japan Cat I EZB contest. That model, which I called "Termite" was 14" long (7" body and 7" boom) and did 20:00 in a local 20 foot high gym. Now with all the 300mg EZBs performing well I decided it was time to try one out so here is some photos and comments as I go along this adventure! 
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dslusarc
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« Reply #1 on: December 28, 2012, 12:36:44 PM »

The Wing and Stab:

Wing Design:
I decided to follow the latest trend of a symmetrical wing that is glued offset to the motorstick. Typically I would build my models with the inner panel longer with the center rib always at the motorstick/wing post junction. I went with slightly longer tips at 4.25" to match what is currently being used. Spars were from some 4.2# A .026 sheet. Front spar is .060" high and rear is .050" high. Tips are from .025 3.7# A grain cut .045 high. Ribs are from .020" sheet 3.9# and cut about .050" high.

Weight of the two wings uncovered were 66mg and 63mg

Stab:
The stab is a template I have used for a long time. It is 21 sq inches and is 10" span. The shape is not a true ellipse, the tips have been "puffed" to allow less spring back from the wood. Outline was 3.8# .020 x .020 and the ribs are .010" C grain sheet 4#. Weight of both stabs uncovered 12mg each.

Covering:
Here is how I cover (see photos). I roll the Y2K film out on a towel then using a frame made from 1/2 x 1/4' balsa (my frame is 12.5" x 30") I spray the frame with 3M 77 then lay it on top of the film. The film once transferred to the frame billows up ad down a good 2" or do so sags on the frame so it fits airfoils just fin. Before covering I cut the film loose from the ends of the frame so the film is only attached on the two long edges.

Once it is on the frame, I hang the frame off the edge of my workbench then lay the parts to be covered on the film upside down. A diluted solution of 3M77 and naphtha is applied to the outline with a brush. The way to apply is dip the brush in the solution then touch the brush right where the film meets the wood outline. The solution will wick out several inches in each direction from where the brush has touched. The next place you apply the solution will be several inches away so the wicking from the next drop meets the wicking from the previous drop. You apply about every 3 inches or so. It kind of depends on the size of the wood. The stab for instance will wick about 4" per drop but the wing about 3". If you watch you can see he "wicking" take place as the film makes little crinkles as the solution moves. Once the outlines are done, I let it sit about 30 minutes then I flip the frame over and inspect for 100% coverage. Where the film touches the wood you will see the film and balsa imbedded into each other. If there is a bad spot you will see no such joint. I then reapply a drop in that area and let sit another 30 minutes. Once I am happy that I see 100% coverage is cut the parts out with a soldering iron.  

Weights after covering are:
wing1: 86mg
wing2: 89mg
stabs are both 22mg each.

To get the correct dilution of 3M to naphtha I do the following:
Using a small glass bottle (I use a Testors 1/2oz bottle from the local hobby shop), I spray the 3M into the bottle for about 2-3 seconds. I have found that you want to push down barely enough to get the 3M to come out, this way it comes out more like a stream not the fine mist of a full spray. I then wait a few seconds for it to stop bubbling then I fill the glass bottle with naphtha then shake vigorously for about 30 seconds. The solution will be a light milky color. Then to test the solution I dip a piece of left over wood. In this case I used a ~5" long piece of scrap wing spar material. Then I dip the end of it in the solution then immediately put the piece of wood on the Y2K film (near the edge of the frame) then let dry for about 30 minutes. Then I pull it off and see how strong it is. If the wood breaks easily before the film joint then the solution is too strong, add more naphtha. I like it to be about the same strength as the wood. This is a personal preference thing but remember the stronger the solution the more weight you will add when covering. Also stronger solution may need to be used for thicker film. The strength I use for Y2K is too weak for Polymicro, so you may need to mix multiple batches. Having covered with microfilm for years I have an idea of how strong the microfilm to wood bond was so I try to duplicate that bond with my Y2K and 3M solution.

By the way, the process I use to cover is exactly how I cover with microfilm. The only difference is that I use water for joining the wing and film together instead of diluted 3M77 spray. Also when covering a wing with microfilm it is best to attach the wing ribs to the film first then let that dry about 20-30 minutes as the ribs will expand from the water and by letting them dry it helps prevent wing spar waviness.

Don  
  
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ykleetx
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« Reply #2 on: December 28, 2012, 01:35:13 PM »

Don,

Great photos and write up.  Is that Y2K or Y2K2 you're using?  The covering and glue on the wing added only 23 mg, so the film is very light. 

Will wait to see more progress.

I'm interested in a plan or photo of your 7-7 model.  What prop and motor did you use for the 20:00 flight ? 

-Kang
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dslusarc
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« Reply #3 on: December 28, 2012, 01:52:36 PM »

I do have a plan for it. Looking in my notes I made it in 1996 not 2000. I will post it as soon as I find it. I drew it up on CAD so have the file somewhere. I recall having to launch it on my toes as high as I could reach as the prop flared so much it vibrated/shook and the model would descend for about 1-2 minutes, by then it was about a foot off the floor and if all went well it would climb out of it then go to the ceiling  Grin 
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dslusarc
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« Reply #4 on: December 28, 2012, 01:53:09 PM »

By the way it is Y2K2 film.
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dslusarc
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« Reply #5 on: December 28, 2012, 02:12:14 PM »

I found the Termite plan. Here it is. It is actually a 7"' body and 8" boom. This was made when I use to love to make wing tips by bending over a soldering iron!
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ykleetx
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« Reply #6 on: December 28, 2012, 02:43:17 PM »

That is an interesting layout.  A big stab to compensate for the short boom. 

No wing offset.  Is this to fight the tendency of the model to roll right (aka right "wing tuck")?  How much left thrust did you have?  Was there any wash on the wings at rest?

What size motor did you use?  Do you have info on launch torque and turns backed off?

How consistent was the model in flying 20 minutes?  Were there any problems with ceiling bumps turning into dives to the floor?

Thanks for answering the questions!
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dslusarc
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« Reply #7 on: December 28, 2012, 06:33:58 PM »

Yes the big tail was to keep tail volume up. The lack of offset was actually to try and make the model intentionally crab/stagger around with the nose up to prevent a fast climb to the ceiling. If I recall correctly it was about 1-2 minutes of staggering around down low to the ground then about 4-5 minutes to get to the ceiling then ceiling bumping until ~15 minutes on the clock then about 5 minutes to come down 20 feet from the ceiling. I came close to setting the Cat I EZB record one day I was at the ceiling at 18 minutes and was BSing with some guys and it drifted a few feet and the wing tip touched the side wall and it slid down the wall. It would have done ~23, I wound for another attempt and the model flew straight for some reason and hit the far wall, I tried to nudge it with the steering pole but then one of the wing struts broke and then the wing failed and the model hit the ground then rolled itself into a ball on the ground in a "death roll".    

The model had about 1/16" opposite wash. I will have to see if I still have notes on the motors used. It would do 18-20 pretty consistently in the gym. Stability was fine during bumping, it is when I added more turns and torque to try for the EZB record is when the "fun" really began. The body was really not strong enough but low ceiling flying typically required stiffer bodies than high ceiling as to keep the rubber weight high you had to use short heavy loops, I think it flew on about .039 x 10" long. My high ceiling EZBs at the time which were heavier flew on longer thinner loops, like 11" of .035, the EZB I did 28:10 with at USIC weighed in at 610mg but used less rubber size than my Cat 1 EZB weighing much less. CAT 1 EZB flying is quite different than high ceiling flying. You basically are flying the model overpowered so it needs a stiffer body. I once took an EZB I had flown in the gym to Akron and wound it the same way. It eventually climbed about 80 feet and deadsticked about 50 feet up.    
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ykleetx
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« Reply #8 on: December 28, 2012, 10:52:07 PM »

There's a dearth of information on Cat I EZB flights.  If you can dig up the motor info, that would be great.

Before Coslick set the current Cat I record of 21:44 in 1996, the previous record was 18:40 or so, also set by Coslick in 1995.  Coslick tells me that he only had one other 20+ minute EZB flight of around 20 minutes.

Here is the info on Coslick's Flight

model weight .455 g
motor 8/93 Tan II, .028" x 8" (~ .300 g motor)
1800 turns, backed off 150, launched at 0.1 in-oz
prop ??

Interestingly, Coslick used a shorter, thinner, and lighter motor than your 20 minute flights.

Josh Finn has recently flown a 18:44 flight at the Cat I site, St. Luke's, in Atlanta.

In 1994, in the USA vs. Japan EZB Postal, Satoshi Kinoshita of Kawasaki City flew 20:04 using a .738 g model.

Does anyone know of any other 20+ minute Cat I EZB flights?
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ykleetx
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« Reply #9 on: December 28, 2012, 11:09:43 PM »

Don,

That's very clever to induce a crab in the model under high torque.  2 minutes is a long time to do that and adds to the flight time.  4-5 minute climb to the 20' ceiling is very very slow.  I'd be curious how you wound the motor and how much you backed off.

-Kang
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dslusarc
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« Reply #10 on: December 28, 2012, 11:55:04 PM »

I wanted to reduce the time the model was bouncing on the ceiling. If you hit the ceiling too soon with too much torque you can break a prop or sometimes the model will fly in larger circles or go straight as the bouncing is so violent so I tried to get the ceiling contact time at a point that was less "violent" so the bumps were more controlled. The site we flew in was a small gym, about 100 x 75 feet so it was easy to get a flight to get out of control on you. In that USA vs Japan contest we flew in, Larry Loucka flew a 17:44 with an EZB weighing about 850mg. His model had a pyramid on the top of the wing center section which we had been trying to help control wing twist.

I am surprised Coslick used such little rubber. I have found that my EZB time suffers with rubber to weight ratios below 1.2 to 1.  I always try to maintain that rubber ratio or greater. I am still digging through my notes to see if I can fly my records from then.  I recall backing off little on those flights and landing with less than half a row of turns. The low backoff is why it was so unpredictable at launch. Sometimes it would climb to the floor and land! The prop flared so much that the blades fluttered, we called it the vibrator prop and it barely pulled which is why I had to launch as high as I could reach, only after the torque fell off and the prop stopped fluttering then it would start to pull.
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« Reply #11 on: December 29, 2012, 10:14:51 AM »

Sounds like Don's EZB strategy is similar to mine with the exception of the flopping about. It takes me about 45 seconds to get to the ceiling on most flights, with the climb being about 45 degrees nose-up. I suppose this could be remedied with a decent flaring prop, but I haven't had much success with them. The 18:44 flight was made with a narrow blade non-flaring prop. I did make it close to 18 with a flaring one, though. My props turn pretty fast...2800-3000 turns is the norm.

Don, I wish I had some of that Y2K...getting under 300 mg is really a pain with OS (but it can and has been done many times). What stiffness specs are you using for your tail booms?

Can anyone tell me how much success Louka had with his wood cabanes? I've been considering those for some time now as a means of building lighter wings without the wing tuck issues.

-Joshua Finn
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dslusarc
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« Reply #12 on: December 29, 2012, 01:33:26 PM »

The pyramid works but can break easily which is why I stopped using it. We made them from .025 x .025 and they extended about 2" on either side of the center post. I use to make a cabane ~5" span about 1.5" high then glue it to the wing at a diagonal. Then once it was dry I glued the other two remaining pieces on to complete the pyramid. We used them back when models were much heavier so they may have been taking more abuse back then than they would now.

Not sure on my tailbooms yet have not cut them out. That is todays work.

The lack of Y2K2 is why I proposed years ago that microfilm be allowed on EZB and Int. Stick as some of us predicted back then that the supply would run out and it would no longer be "commercially available" (as per AMA rules), mainly due to the fact it was an experimental run of film not a production thickness. When Y2K2 first came out it was almost banned because there was no certainty if it would be around years later and consequently would no longer be "commercially available" however it survived the vote of the indoor board so was allowed. So now years later what some of us predicted has unfortunately come true. I was basically tarred and feathered for my proposal to lift the covering restrictions on EZB and Int Stick but I still stand by my reasoning. Those who have the Y2K2 now have an advantage in these events, if microfilm was allowed then you can pour your own "Y2K2" as the weights are nearly identical. In my proposal the weight difference I calculated on an EZB was ~8mg saving with microfilm vs Y2K2. I could not get most people to see the logic of the argument, they simply knee jerked when they saw the word "microfilm" and then personal perceptions of the "difficulty of microfilm" took over and it was voted down. Once it was voted down I then bought 4 rolls of Y2K2 and saved them for only EZB and Int Stick use exclusively.

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« Reply #13 on: December 29, 2012, 01:48:29 PM »

You save about 15 mg overall using Y2K2 instead of OS film.  May be Don would consider selling a small length of the film for EZB enthusiasts.  I used OS film on my EZB except the ultra light one.   The Y2K2 came from Mark Bennett.  More recently, I received about 5' of Y2K2 from Bob Loeffler, a modeler from Phoenix.  I'm saving it for my HLS.
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ykleetx
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« Reply #14 on: December 29, 2012, 04:13:59 PM »

Additional Info on Coslick's 21:44 Flight

model weight .455 g
motor 8/93 Tan II, .028" x 8" (~ .300 g motor)
1800 turns, backed off 150, launched at 0.1 in-oz
prop 13.25" D x 23" P




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« Reply #15 on: December 29, 2012, 06:30:50 PM »

>Does anyone know of any other 20+ minute Cat I EZB flights?

Hi Kang san. I joined this Forum just now.
I have done 25mins 30secs at a 7.4m gym over 10 years ago.
Cat2 flight was 26mins 24secs at a 9m gym.
My ezbs were about 0.5g.
Good flying, Aki
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« Reply #16 on: December 29, 2012, 08:32:01 PM »

Wow! Thanks for all the good info. I don't fly EZB's these days but maybe I'll get back to it. Meanwhile it's safely (I hope) stored on my hard drive.

I'm afraid I don't  belong in such rarefied company. My best EZB weighed around 0.6g, but it was pretty rigid, or at least the wing was, as I had one little piece of fantastically good wood for the spars.  Best flight was 14:48 at Glastonbury CT, but as I recall it was a no touch that didn't even get up to the retracting barriers that hang from the ceiling around the edge of the central area. Does anyone know how high they are? (Those blue things.) I think it was probably about Cat 1 height or a bit lower. Certainly the ceiling in the middle is much higher.  Wish I could have flown my EZB at a site with a clean ceiling. Or learned how to get my model to climb before it was destroyed. Unfortunately, a careless scale flyer launched into it, and busted it into many pieces. Can't bring myself to build one since then. Maybe if the Weymouth hangar was still there, but they tore it down when I was getting interested in airplanes.
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« Reply #17 on: December 29, 2012, 09:21:54 PM »

Hi, Aki,

Those are incredible times.  Do you have information on the motors (length, weight, turns, turns remaining) and the prop?

-Kang

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dslusarc
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« Reply #18 on: December 30, 2012, 12:44:01 AM »

Here is my tailboom and motorstick. The tailboom is from some tapered 3.7# stock I got from F1D biz years ago. My boom is .070 x .060 tapered to .045 x .030 x 9.25" long. I cut two and they both weighed in at 19mg. I put one on deflection gage and with a pin (120mg) deflection is about 0.8 inches.  If I put the actual stab on it it barely deflects as all.

The motorstick is from the thicker side of the 3.7# tapered stock. I am going with a 6" stick. The front is .070 x .134  then middle .083 x .151  then rear .076x .130 . The weight of the blank is 63mg. For the "EZB Challenge" I will be rolling a motorstick from .008" 4# and the blank should be about 30mg. I may roll a tailboom for the challenge as well, I have not decided yet.

Don
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ykleetx
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« Reply #19 on: December 30, 2012, 01:33:43 AM »

Looks like the EZB will be very light ...
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« Reply #20 on: December 30, 2012, 07:04:33 AM »

Hi, Aki,

Those are incredible times.  Do you have information on the motors (length, weight, turns, turns remaining) and the prop?

-Kang


Prop D340 P590

Cat1, 7.4m, '02,Mar,18, 25:30
Tan2 May99, 298mm, 0.59g, 2360-190turns, 9.5gcm, 275

Cat2, 9.0m, '01,Mar,13, 26:24
Tan2 Jul99, 315mm, 0.62g, 2500-180turns, 8.4gcm, 400
It was cold, only 13 degC indoor. So, lots of turns remaining.

These times may be good, but it is not very important.
I could do good times just only because I could fly at very good gyms.
Aki
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« Reply #21 on: December 30, 2012, 08:41:11 AM »

Don, that is some really good wood. I wish I could even approach those weights. Most of my booms are 35-40 mg and smaller dimensions.

I rigged up a pyramid cabane for my 75 mg EZB wing last night and the results were impressive. I think that will allow me to launch with much higher torque. I'm thinking about making a longer motorstick, but that will have to wait a little.

With your rolled tube fuselage, what do you project the weight will be?
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dslusarc
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« Reply #22 on: December 30, 2012, 01:17:36 PM »

My final weight is really going to be dependent on the prop. I was reading my 35cm notes and found a nice 12" prop blade shape I will use on my EZB. I wish EZB had built up props, my 35cm prop was 45mg. I am also actually considering making two new wings.
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« Reply #23 on: December 30, 2012, 02:56:56 PM »


Prop D340 P590

Cat1, 7.4m, '02,Mar,18, 25:30
Tan2 May99, 298mm, 0.59g, 2360-190turns, 9.5gcm, 275

Cat2, 9.0m, '01,Mar,13, 26:24
Tan2 Jul99, 315mm, 0.62g, 2500-180turns, 8.4gcm, 400
It was cold, only 13 degC indoor. So, lots of turns remaining.

These times may be good, but it is not very important.
I could do good times just only because I could fly at very good gyms.
Aki

Thank you for the info, Aki.  They are incredible.  Is the Cat I building the same one where you set your F1M and F1L records?

One day, some of us would like to come to Japan and fly with you.

What are your best times in Ministick in these gyms?

-Kang
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« Reply #24 on: December 30, 2012, 02:58:30 PM »

Lincoln,

Why don't you take the EZB challenge and join the fun?  Give it a shot.
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