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Author Topic: New model for upcoming season  (Read 1087 times)
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BR549
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« on: July 18, 2017, 05:40:02 PM »

My learning continues. My second EZB build is done, just waiting for the season to start here in Oklahoma.

I checked out a couple different plans for ideas and dimensions, then drew up my own design called Angular Momentum. Prop design is from the Hobby Shop EZB in INAV #107.

All up weight is 1.780 grams, half the weight of my first attempt. Living room tests are very promising. I work on an Air National Guard base here in Oklahoma, so I've started the process to use a hanger here for testing/practice.

https://scontent-dft4-3.xx.fbcdn.net/v/t1.0-9/20108107_10155475199284847_8308045329176760811_n.jpg?oh=c9ab97cc1cf74f155ab9faa0f993248a&oe=5A065A1E
New model for upcoming season
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Skymon
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« Reply #1 on: July 19, 2017, 03:42:01 AM »

That looks very neat.
I notice you didn't make up the prop from strips, it's just single piece for each blade.

I find it very satisfying to see the weight dropping off with each model.
There's a lot to learn with indoor. A lot of new techniques.
I'm only a few months in to that journey.

Having a hangar to practise in must be great !

Best of luck with your building and flying.

Regards
Simon
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BR549
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« Reply #2 on: July 19, 2017, 05:53:42 AM »

Thanks Simon

Yes, I made the prop out of one piece this time. I'll try the strip method in subsequent attempts.

Daytime temps are over 100 here and the hanger is uncooled. By the time it cools off they are going to start renovations, hopefully I'll get some time in it. Currently the club flies in a basketball court so it would be a nice change.

Bob
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BR549
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« Reply #3 on: September 19, 2017, 08:46:14 AM »

Made my first flight this past weekend and was very happy with it.

I logged 4:24 in a basketball court. It has a (I believe) 26' ceiling with hanging girders and lights so I couldn't really push it hard at all.

I've already started work on my next build, this one will be an F1L.
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Skymon
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« Reply #4 on: October 17, 2017, 10:51:15 AM »

Any more flights logged?
S
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BR549
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« Reply #5 on: October 19, 2017, 11:42:42 AM »

Last weekend I spent trying to learn how to fly it. Fiddled with wing post heights and started trying to get my rubber matched to the prop, somewhere around .068-.072 gm/in seems to be the sweet spot. I did have a couple more flights around 4 minutes, and neither went up more than 18 feet or so.

Learning a lot at this early stage of my free flight career. Going to start on my next EZB soon, try to chop the weight again.

Thanks for asking.

Bob
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Olbill
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« Reply #6 on: October 19, 2017, 12:20:28 PM »

The rubber you're using seems awfully heavy for the model but it could be b/c your model is heavy for the size. Just for comparison motors for my LPP are around 50 to 60 mg/inch. Or are you calling out the weight for the loop rather than the strand?

Leo has stated that he intends to go completely metric soon. I would hate to have to learn a new set of standards for my rubber but grams per meter does make more sense than grams per inch. I'll have to think about whether I want to do that or not.
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cglynn
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« Reply #7 on: October 19, 2017, 02:25:58 PM »

Bill (or Leo), real quick here, so as not to go too off topic, but what advantage do you see in using g/m as opposed to g/in?  Is there a level of precision to be gained, better for effective communication with the international crowd, or does it make any math used for flight predictions easier as the units for rubber weight and model weight will agree with one another?


Bob, I will second what Bill said about rubber weight.  Rubber of that density can fly a model over 3g with ease, so there may be some other culprit.  Have you tried playing with the center of gravity?  I have observed models with a CoG that is too far aft will have difficulty climbing, and require oodles of power to even begin to perform.  Next time you fly, try moving the CoG forward.

Another thing to look at is your prop.  For whatever reason, the single piece blades I have built never held their twist very well, and became inefficient.  Those props would require lots of power for limited duration. 

Hope that helps a bit.


-Chris
« Last Edit: October 19, 2017, 02:50:24 PM by cglynn » Logged
mkirda
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« Reply #8 on: October 19, 2017, 05:15:15 PM »

The rubber you're using seems awfully heavy for the model but it could be b/c your model is heavy for the size. Just for comparison motors for my LPP are around 50 to 60 mg/inch. Or are you calling out the weight for the loop rather than the strand?

Leo has stated that he intends to go completely metric soon. I would hate to have to learn a new set of standards for my rubber but grams per meter does make more sense than grams per inch. I'll have to think about whether I want to do that or not.

But grams per inch is so bastardized, it makes perfect sense! That's Merika!
{tongue planted firmly in cheek}

Regards.
Mike Kirda
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Hepcat
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« Reply #9 on: October 19, 2017, 06:32:54 PM »

Response to #6,#7 and #8 on units.

I grew up with 'Trad' units but have been forced into a lot of 'Napolionic' units at times.  The 'Nap' units grouped in tens can can be handy at times because it makes a few bits of simple arithmetic even simpler if you live in a country which does not sell calculators.  Unfortunately for 'Naps' things in nature don't restrict growth in steps of ten and the old 'Trad' units are often more appropriate in practical work.  However my rational has backfired somewhat when it come to g/m or g/inch for the specific weight of rubber.  I used to have two bits of Scotch Tape on the edge of my desk which were 36 inches apart because rubber that length seemed convenient when using a rubber stripper.  I now have the two markers one meter apart so when I cut a length of rubber for stripping I just drop it on my scale and there is my g/m automatically.  Also you find there are fewer decimal points and zeroes in your note books.
John
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Olbill
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« Reply #10 on: October 20, 2017, 12:15:18 AM »

Bill (or Leo), real quick here, so as not to go too off topic, but what advantage do you see in using g/m as opposed to g/in?  Is there a level of precision to be gained, better for effective communication with the international crowd, or does it make any math used for flight predictions easier as the units for rubber weight and model weight will agree with one another?

-Chris

Two advantages - (1) standardize units for better communication with overseas modelers and (2) build some new brain cells.
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dslusarc
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« Reply #11 on: October 20, 2017, 11:29:08 AM »

Just when I was getting use to grams per yard.... Grin
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leop
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« Reply #12 on: October 20, 2017, 02:11:15 PM »

Bill said it.  The majority of fliers in FAI classes and events use metric units.  Communication is easier with metric units.  Also, younger fliers, especially those in schools with good STEM program, use the metric system fluently.  I need to consider this when coaching Science Olympiad teams.

The one sticking point is how to measure torque.  The fliers using the metric system use gram-force - centimeter.  This is not an SI specified unit for torque (newton-meter is).  The difference is a factor of 9.806650: one kilogram-force - meter is 9.806650 newton-meters.  However, I will be using gram-force - centimeter for torque.  This unit, although not SI, is widely used.  And, it is no where near the craziness of the milligrams per inch that many of us non-metric fliers use for rubber linear density.

LeoP
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mkirda
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« Reply #13 on: October 20, 2017, 04:34:39 PM »

LeoP,

I think we should use Fig Newtons per inch.

Of course I'm hungry, so that might be why. Grin

Regards.
Mike Kirda
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BR549
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« Reply #14 on: October 20, 2017, 06:32:32 PM »

Thank you for all the comments.

I'm sure the weight, combined with a crude prop and other inefficiencies is no doubt the reason for the rubber size. I also simply haven't tried smaller rubber yet. Next time out I will and see how it flies. As it is I've had it scream to the ceiling and bounce off the iron at times, and have to fetch the retrieval pole of shame when it didn't bounce.

I know so little that every bit if information helps.

Bob
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cglynn
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« Reply #15 on: October 23, 2017, 09:18:57 AM »

Bob, the screaming to the ceiling tells quite a bit actually.  To me, it seems like you are carrying too much rubber, overpowering the model, and also unnecessarily increasing the flying weight.   For the EZB and F1L events, I start my motors at around 85% to 110% of the model weight.  That usually gets me in the ballpark to get decent flights from which I can experiment.

So for your 1.7g model, Try motors that are 12" long by 1g, 1.25g, 1.5g, 1.7g, and maybe even heavier. 

For what its worth, I personally fly on as little rubber as needed to get the turns and torque required for the time I want to fly at a given venue.  This results in little backoff, and few turns remaining at the end of a flight.  I feel the lower the overall flying weight, the better the flight performance. 
Other fliers go the other way and throw gobs of rubber on a model, back off a ton of turns, and land with a ton of turns....but they still fly excellent times (and usually beat me in competition...so there is that.)

Hope that gives you some more direction.  Keep experimenting and collecting data.  Remember, only change one thing at a time.  You will get there.  Have fun

CG
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