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Author Topic: The sub 400mg EZB plunge!  (Read 12930 times)
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adanjo
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« Reply #25 on: December 31, 2012, 06:49:17 AM »


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
Yes, I set F1L and M records there. And Kinoshita san also flew EZB over 20 mins there.
I have never flown Ministick there.
My best time in Ministick in cat2 9m gym is 11mins 51secs.
The 9m gym is the best one to fly Ministick, though we have to install a ceiling bumper because the ceiling vents catch Ministick.
Aki
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ykleetx
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« Reply #26 on: January 02, 2013, 05:11:38 PM »

Aki,  Your 11:51 Mini Stick flight is also better than the AMA Cat II record, like your EZB flights.  Well done!
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dslusarc
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« Reply #27 on: January 04, 2013, 12:36:36 AM »

Here is my EZB update. Made two fins, covered them and attached to the booms. Each fin was 3mg. Also cut out a second motorstick. I decide I will have two lightweight AMA EZBs then one for the "EZB Challenge" with a rolled body and boom (I found my wood I will be using for that). I also cut out tapered prop spars, enough to make 4 props. Also I separated out all my potential prop wood. I have lots of .007, but have a few .006 sheets and a one that is close to .005" but sure feels lot weaker for that extra .001" thickness difference. I also found some .003-.004 I had specially ground for me years ago by F1D.biz that literally looks like paper it is so thin. I had it ground like that as I once thought about making a built up EZB prop and covering it with this near paper thin balsa so it would be all wood so AMA legal but also hoped it to be more truer in pitch distribution since it would be stiffer. This wood though is so fragile that I think a few bumps would just blow holes into it. Anyhow, I also cut out enough wood for two more wings. I want to try two a little lighter.

After I covered what I had for EZB the other day, there was enough on the frame for a ministick wing and stab.  My last ministick was destroyed years ago when the wire bearing pulled out of the fuselage after I launched so decided now was as good of a time as any to make a new one. so I am building a copy of the one I had years ago and the wing and stab are now built and covered with dihedral added.

Don
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Maxout
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« Reply #28 on: January 04, 2013, 08:37:38 AM »

This wood though is so fragile that I think a few bumps would just blow holes into it.

Well Don, you could always send that wood to me. Wink
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dslusarc
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« Reply #29 on: January 05, 2013, 02:43:15 PM »

To new wings made. Uncovered they are 45mg and 46mg. Covering them is next. Then onto my wire nose bearings.
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ykleetx
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« Reply #30 on: January 05, 2013, 02:56:17 PM »

These are substantially lighter.  Well done!
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dslusarc
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« Reply #31 on: January 05, 2013, 05:00:02 PM »

.008" music wire thrust bearing. ~5mg

Don
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dslusarc
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« Reply #32 on: January 05, 2013, 05:05:18 PM »

These are substantially lighter.  Well done!

Hopefully not substantially weaker as well!
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dslusarc
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« Reply #33 on: January 06, 2013, 10:24:23 PM »

Both motorsticks are finished. 73mg each.
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ykleetx
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« Reply #34 on: January 06, 2013, 11:04:44 PM »

Those sticks look pretty strong.  Did you have the tail hook leaning to the left a little? 

It looks like the models will be in the mid 200's.  Very nice.
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dslusarc
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« Reply #35 on: January 06, 2013, 11:14:50 PM »

Those sticks look pretty strong.  Did you have the tail hook leaning to the left a little? 
It looks like the models will be in the mid 200's.  Very nice.

Yes hooks leaning to the left. I learned that lesson the hard way many years ago! I think ~250mg is a reasonable projection. It really will come down to these props. I never had good luck with superthin wood EZB props in the past, the blades would get wavy on me. So need to come up with something other that they way I use to make EZB props.

Do you know what Richmonds EZB weighed that he set the Cat II record at Kent with?
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ykleetx
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« Reply #36 on: January 07, 2013, 05:06:19 PM »

Yes hooks leaning to the left. I learned that lesson the hard way many years ago! I think ~250mg is a reasonable projection. It really will come down to these props. I never had good luck with superthin wood EZB props in the past, the blades would get wavy on me. So need to come up with something other that they way I use to make EZB props.

Do you know what Richmonds EZB weighed that he set the Cat II record at Kent with?

Richmond's EZB was approximately 305 mg at Kent.

I make my prop blades in the usual way (a la Coslick's Hobby Shop EZB article).  This method works well for me.
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dslusarc
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« Reply #37 on: January 10, 2013, 11:44:08 PM »

OK, the two new wings are covered. Both are ~65mg. I think these may be too weak but hard to say as I have no real reference to what they need to be. These wings also have 5 ribs in them. I may put the pyramid on these wings if needed. Props are next!

Don
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ykleetx
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« Reply #38 on: January 11, 2013, 12:11:45 AM »

That's what my wing weighs so it's on track. 

You could test glide the wing with the fuselage ballasted with the right weights and see how it handles the load.

My EZB flies slower than a F1D.  Sanborn's F1D passed my EZB when we flew in Atlanta last month.
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dslusarc
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« Reply #39 on: January 11, 2013, 12:26:39 AM »

Well them maybe all will be OK. All in all I am pleased with how these new EZBs are turning out. Not sure on prop size, was thinking of a 12" diameter 24" pitch flaring shape. I tried a 10/20 once years ago on a light EZB and the prop was very light for the time about 65mg but rpm was rather high so went back to 14" and it flew better but then that model was ~500mg. I was thinking of trying a 10" but with over 2:1 P/D. My ministick prop is a 7/17 prop which is 2.4:1 so why not a 10/24 for EZB?
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ykleetx
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« Reply #40 on: January 11, 2013, 03:37:56 AM »

My prop was 11.75 x 23, symmetric blade, for Cat IV and 11.75 x 19, moderately flaring blade, for Cat I with scrubbing.   For no touch Cat I or II, I would think 12x24 full flaring would be good.  I have a 13.25 x 26 full flaring prop that I would like to try in a low ceiling site.

Have fun experimenting!
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dslusarc
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« Reply #41 on: January 17, 2013, 07:50:45 PM »

Sorry for the lack of updates. I have been getting my butt kicked by the latest flu bug going around. Just getting over it now. Hope to get back to these props over the weekend.

Don
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dslusarc
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« Reply #42 on: January 19, 2013, 04:37:24 PM »

Here is my first prop. Seems I do not have the lightest wood for the blades. The blades are 66mg for the pair. 81mg with spar wood. This will be a 12/24 prop. 
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ykleetx
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« Reply #43 on: January 19, 2013, 08:22:43 PM »

Yes, 66 mg for a small prop is heavy.  Do you have another sheet of similar thickness and density?  If so, I would like to know what is the weight of the sheet divided by its area -- a figure in mg / in^2 (or mg/si).

The lightest wood that I have used is just under 5 mg/si.  My 11.75" props have ~4 si per blade.  My total weight budget is something like:

blades x 2                 40 mg
spar x 2                    18 mg
glue (blades to spars)   2 mg
hook                          3 mg
total                        63 mg

I have some of this light wood if you would like a sheet.

-kang

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dslusarc
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« Reply #44 on: January 19, 2013, 08:52:19 PM »

That is good info. My blades are 4.63 sq inches each and .005" thick so that comes out to 5.4# wood. The sheet was not marked for weight so I will try other sheets. This wood calculates to 7.13 mg/sq inch so I am guessing your 5mg/sq inch wood is ~.005" 3.8# density?

Don
 
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green-man
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« Reply #45 on: January 20, 2013, 03:52:55 AM »

Hi Don,

It's very difficult (but not impossible) to cut these ultra-thin sheets without surface compression from the spinning blade increasing the density of the finished sheet.

Nick.
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ykleetx
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« Reply #46 on: January 20, 2013, 12:46:06 PM »

Another thing is to try a blade with slightly smaller area.  Richmond's prop is only about 3.5 si, and so was Max Zaluska's.   Both had narrow chord blades.
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dslusarc
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« Reply #47 on: January 20, 2013, 02:28:46 PM »

Nick: I have heard that surface grinding and cutting thin sheets can compress the wood. Maybe that is the case on this sheet. 

Kang: 3.5 sq inches may make these blades usable after all! Is there a plan for Jims prop anywhere? What was his diameter and pitch? 

Don
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ykleetx
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« Reply #48 on: January 20, 2013, 03:16:59 PM »

Don,

I copied Richmond's prop for my "BS 6" EZB.  A plan is available in the Builder's Plan Gallery.

His prop is 13 3/8" x 30" -- a rather "large" and high pitch prop.  Probably a little too "big" for the 250 mg EZB.  I have mine pitched lower, around 24 to 26", but  I think the true pitch during flight is much higher than that, as the blades flare significantly.  I haven't used this prop, yet, for the ultra light EZB, but I would like to try when the opportunity is there.

-kang
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dslusarc
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« Reply #49 on: January 21, 2013, 12:00:01 AM »

All the .005-.006" wood I have comes out to about 6.5 mg sq inch. I did find one sheet of .007 C that weighs  6.5 mg/sq inch so if I can sand it down a little that might work. My new blade design is 3.5 sq inches so now I am looking at ~46 mg or so for a pair of blades.  I also finished my blade form today, I added some fiberglass cloth to the back side of it to keep the twist and to make it stiff so I am now ready to form some blades. I have to also figure out how much to dilute the wood glue used for attaching the blades onto the spar. I have never used thinned out wood glue to attach prop blades before, I guess I will start with a 50/50 glue to water mix  Huh

Don
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