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Author Topic: Ministick and microstick - trying to get back into indoor!  (Read 17467 times)
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Flyguy
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« Reply #150 on: February 26, 2018, 12:05:43 AM »

That was a fun test, so I thought I might as well upload the video (I'm not videoing much in Teaneck because I'm too focused on using the flying time!).

I almost feel a little bad about posting the micro plan, I should have noted that it's definitely not a model for beginners. I know from being in the club lately that people have problems trimming minis, they can be tricky, and the micro only complicates the problems, so I would strongly recommend not to start with that. You can get a bunch of A6 plans online, and the people who were flying p18-like models who have now built A6's are getting very good flights, so I think it's better to start with an A6 instead of a finicky micro.

The micro flight in the video was with a 12" loop of .015" thick rubber that I stripped.
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Flyguy
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« Reply #151 on: March 03, 2018, 08:41:59 PM »

Beautiful work Flyguy! I will be anxiously waiting to see how it goes! Please make sure the first flight stays well below the girders as you won’t be the only one to be disappointed if it doesn’t!

Well it stayed below the girders on the first flight at least! Good news is that the 20" AR6 flies nice, went up about 20 something feet on the first test and did over 5 minutes, flies nice and a little slower. Unfortunately, it went up to about 40 feet on the second test and those vicious girders ate it! Really unforgiving of any mistakes. Slid down into the big I beam, you can only see a little bit of the wingtip sticking out. My friend also lost his first A6, so that's it for him this year (he's getting ready for outdoor). I've already built a new 20" A6, photo attached. Only differences are that I put the wing/stab leading edges at a 45 angle to see if that helps with the airfoil, and the stab has a higher AR, but slightly less area. We'll see what happens, would be nice not to have to build another for a while! This one came in a little light at 1.15 grams.

Also working on another mini, given that I've lost 4 (still have one left, didn't lose it last time!). Already built the original design 4 times, so I changed it this time.
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cessnadriver
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« Reply #152 on: March 03, 2018, 11:20:24 PM »

It sounds like the new, higher AR design is a winner!
Sorry to hear the second flight stayed up there. What was the difference from the first flight?.....more rubber turns?...or?

I haven’t given up on the Micro yet. Getting close to an attempt at Living-Room-Flying it. I’m not expecting major
success but would like to at least say that I tried.

I’m looking forward to building an A6 since the  size of the materials used to construct an A6 will seem large compared to the Micro.

I am also working with my own, home grown rubber slitter (using a razor blade segment) with some degree of success but I doubt that I can get much below .030” strip size.

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Olbill
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« Reply #153 on: March 04, 2018, 01:28:25 AM »

Unfortunately, it went up to about 40 feet on the second test and those vicious girders ate it! Really unforgiving of any mistakes. Slid down into the big I beam, you can only see a little bit of the wingtip sticking out.

I wonder at what point you are going to spend some serious effort on learning altitude control?
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Flyguy
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« Reply #154 on: March 04, 2018, 11:29:01 AM »

Easier said than done at this site. I've had dozens of flights where I was just skimming the rafters, paying close attention to the torque. However, if you end up as little as 1 or 2 feet too high for whatever reason then there's a good chance you will lose the plane, and it's very hard to control the height to within that limit, more than welcome to hear any advice on getting that fine control. My friend has been flying very conservatively, has been winding to low torques, yet he has also still lost planes (I think this time because the air was a little warmer), as has every single flyer at the site. Take a ride over and do some flying and I think you'll realize the challenges of this site. Also you have to remember that I'm not fine tuning the same plane over and over (keep losing them!) and that I'm experimenting with different props etc., so that raises the risk of going a few feet too high. The only way to be totally safe is to keep it at least 5 feet below the rafters, but then your times are lower, so eventually you take the risk.
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Flyguy
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« Reply #155 on: March 04, 2018, 02:50:57 PM »

It sounds like the new, higher AR design is a winner!
Sorry to hear the second flight stayed up there. What was the difference from the first flight?.....more rubber turns?...or?

I haven’t given up on the Micro yet. Getting close to an attempt at Living-Room-Flying it. I’m not expecting major
success but would like to at least say that I tried.

I’m looking forward to building an A6 since the  size of the materials used to construct an A6 will seem large compared to the Micro.

I am also working with my own, home grown rubber slitter (using a razor blade segment) with some degree of success but I doubt that I can get much below .030” strip size.

I'm holding off on any conclusions about the 20 incher until I get some more flying time in with it, but it does look good. Yes I went to a little higher torque/more turns on the second flight, but .07 oz-in generally seems to get it up just about 30-35', so who knows, it went up just a few feet higher and that's the kiss of death in this site.

Not trying to discourage you on the micro, just a heads up that it might be tricky. It is really nice to have something small enough to fly in the living room, my minis are too big for that, so that part is fun. If you can only strip to .030, then you'll need to use a single strand motor for the micro, I showed how I did that earlier in this thread. In the meantime start saving for a stripper, it's worth it in the end. Good luck, it's nice to get at least a little success for some encouragement to continue.

Yup, the A6 really has some lumber compared to the micro. That's what encourages people to give it a shot, plus all the ones I've seen have flown really nice. And as you can probably tell from this thread, they build pretty fast!

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Flyguy
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« Reply #156 on: March 06, 2018, 09:05:25 PM »

Just finished my new design mini stick, but there's no flying tomorrow, given the current forecast of 8-12 inches of snow! Good time for building though.
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cessnadriver
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« Reply #157 on: March 06, 2018, 11:02:53 PM »


I'm holding off on any conclusions about the 20 incher until I get some more flying time in with it, but it does look good. Yes I went to a little higher torque/more turns on the second flight, but .07 oz-in generally seems to get it up just about 30-35', so who knows, it went up just a few feet higher and that's the kiss of death in this site.

Not trying to discourage you on the micro, just a heads up that it might be tricky. It is really nice to have something small enough to fly in the living room, my minis are too big for that, so that part is fun. If you can only strip to .030, then you'll need to use a single strand motor for the micro, I showed how I did that earlier in this thread. In the meantime start saving for a stripper, it's worth it in the end. Good luck, it's nice to get at least a little success for some encouragement to continue.

Yup, the A6 really has some lumber compared to the micro. That's what encourages people to give it a shot, plus all the ones I've seen have flown really nice. And as you can probably tell from this thread, they build pretty fast!




Flyguy

Getting close to flying my version of your Columbia Micro. Picture below. (I hope.....Don’t look too close, it’s pretty crude).

I will start with a single strand motor and would appreciate some advise on how to wind the motor without rolling the little plane up in a ball! Wind on the plane? If so what stooge configuration? Or is it better to wind on a fixture and then install wound motor on the plane? Any help would be appreciated!



Al
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Flyguy
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« Reply #158 on: March 06, 2018, 11:38:14 PM »

I'm impressed, particularly if this is your first Micro! nice round wingtips and nice elliptical stab, what's the weight? You never wind on the plane on indoor, usually you wind on a torque meter then transfer to the plane. If you don't have that, then just make a hook and clamp it to something solid and you can wind on that. Do some searches on HPA, here's an extensive thread on winding, torque meters, winding methods etc. that should answer all of your questions:  http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=3650.0
Good luck!
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cessnadriver
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« Reply #159 on: March 07, 2018, 12:01:30 PM »

I'm impressed, particularly if this is your first Micro! nice round wingtips and nice elliptical stab, what's the weight? You never wind on the plane on indoor, usually you wind on a torque meter then transfer to the plane. If you don't have that, then just make a hook and clamp it to something solid and you can wind on that. Do some searches on HPA, here's an extensive thread on winding, torque meters, winding methods etc. that should answer all of your questions:  http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=3650.0
Good luck!

Thanks Flyguy. The winder forum is quite interesting. Recently I was working on adding a digital readout to my 10:1 winder, making use of a magnetic pickup and an Arduino. I got the prototype working in but that project, like many others is “temporarily” on hold!

I have a couple of torque meters (twisting music wire, with a disc and pointer) that I made a few decades ago. They may be useful, or serve as a reference in making a new one to wind small cross section motors.

My immediate problem is figuring out how to get the wound motor from a winding fixture to the hooks on the Micro, having only two hands to work with (neither of which belong to a surgeon!). I tried moving the wound motor from the winder to a stick with two posts, and then to the hooks on the plane, but still seemed to need a third hand. I’m sure it will eventually come to me but hope that the little Micro will survive my learning process.

The plane was built from materials on hand and 4# Balsa is not yet part of my inventory. My initial goal is to learn how to build these delicate airframes before making any major investments in materials and tools. If anything I produce actually flies (i.e., at least two laps around the living room) that will be “icing on the cake”.

Having said that, my Micro weighs .652 grams without the motor! Plenty of room for improvement!

Al
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Olbill
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« Reply #160 on: March 07, 2018, 12:10:45 PM »

Start here:
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=3650.0
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Flyguy
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« Reply #161 on: March 07, 2018, 01:18:01 PM »

Yes, that's the exact same link I gave in my reply above.

Al - usually I remove the front part first and attach that to the prop hook, holding the plane with one hand, then remove the rear part and attach it to the rear hook.
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cessnadriver
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« Reply #162 on: March 07, 2018, 02:48:16 PM »


Al - usually I remove the front part first and attach that to the prop hook, holding the plane with one hand, then remove the rear part and attach it to the rear hook.

Thanks Flyguy,

Just another example of how I tend to overlook the obvious!

Al
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« Reply #163 on: March 08, 2018, 12:19:28 AM »

Flyguy,
I don't have any 20", high AR models but I think you would find the following interesting. Google 'NORWIND' Indoor flyers and you should be able to open the 'Norwind' web site put up by Tom Tomlinson.  On the top line the is a heading 'plans' and scrolling down you will find a plan for an 'Easy A6 foam duration Model' designed by John Taylor.  To my eyes it is a beautifully proportioned aeroplane with 15" span an an AR of  8. The plan says it flies on a 10" loop of 0.04 rubber. Obviously with the foam surfaces it won't be down to 1.2g but people tell me they will do three or four minutes.  John Taylor is an interesting chap. An aeromodeller as a boy so naturally applied for an apprenticeship at nearby AVRO. He was bright so they sent him to Imperial College ,London to get his 'bits of paper'. He was put in charge of the wind tunnel, then was involved in many things, including the Vulcan' and finished up as Technical Director. When he retired he took up aeromodelling again and that is when I met him. One of his aerodynamicists was Reg Boor who made Larrabee's work accesible to a lot of modellers. It is interesting that Reg helped Bernard Hunt with his spreadsheet and John was co author of Bernard's paper on testing balsa wood.
John
 

Just completed this based on the above.

4.3g without motor.

Regards
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« Reply #164 on: March 08, 2018, 05:20:34 PM »



Al - usually I remove the front part first and attach that to the prop hook, holding the plane with one hand, then remove the rear part and attach it to the rear hook.

Flyguy,

Is it common/appropriate to make fine trim adjustments at a flying site on a small plane like the Micro by bending/twisting tail booms, spars, etc.? Or is solvent-softening glue joints and repositioning control surfaces the preferred method?

I am getting the impression that the trim on my sudo-Micro is very susceptible to handling and that small tweaks make a noticeable difference in flight trim. Seems like the light weight structure can change shape quite easily with handling in the process of removing and replacing the motor after winding. Of course I’m still at the ham-handed beginner stage, hoping that I will develop some degree of finesse before too long.

Shadow,

Nice job on your new plane!


Al
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Flyguy
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« Reply #165 on: March 09, 2018, 10:40:06 AM »

Yes, a little bending or twisting is usually sufficient for some trimming. Sometimes I'll do some glue softening, usually that's for changing something like the tailboom angle or wing post angle, but that's it.

Nothing should change shape. I think what you're referring to is that the fuselage twists a little when you put the motor on. You want that! It should twist slightly so that the left front of the wing is raised a bit (wash in) to counter the left twist from the torque. If your plane is torquing in to the left, then sand the fuselage between the wing posts very lightly and slowly until you have enough twist to get rid of the left spiral, that's important.

I have a new A6, a new mini, and a new no-cal, looking forward to flying next week!

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« Reply #166 on: March 12, 2018, 07:59:32 AM »


My two last A6's both came in under 1.2 grams and I wasn't trying to build light (sturdy instead), so I'm pretty sure that I can make a higher AR wing and still keep it around 1.2 g, in fact, my high AR version weighs less than my medium AR version, and they are both underweight. However, right now I'll stick with the current wing, 8.5 AR, since it looks like it can do over 7 min and I've barely flown ittt, first time out and it's already close, and it stayed under 35-40 feet the whole flight, that's all the altitude that's available, plus it just looks 'right'.

However if anyone out there knows anything about higher AR A6's (category has been around forever, seems like someone must have tried it) let me know, otherwise sooner or later I think I can build a light A6 with like a 13 AR, if I do I'll report back, nothing like actual flying to figure out these things, plus this is what makes it fun - actual data. new balsa from greenman should also be here any day now...

Came across this today and thought you might be interested, if you haven’t seen it already. Can’t say for sure what the AR is but it looks high. Maybe more info from the builder could be had.

Have gotten down to ~.024” with my razor blade rubber stripper and will try for .012” (“impossible dream”?). I made some trim mods on my Columbia Micro to tighten the turn. Hope to try it today.

Al

https://flyhaffa.com/model-aircraft-of-the-month/feb-2017-model-aircraft-of-the-month-jeff-renza6-indoor-model-aircraft/
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« Reply #167 on: March 14, 2018, 10:17:38 PM »

Thanks Al, always interesting to read these things!

I finally got some test flights in today with my new high AR A6 and it's looking really good, seems slightly slower and nice slow climb and good cruise, which is what you want in this site. Here's a test flight and some other flying in the armory: https://www.youtube.com/watch?v=PJhj7koQrvA

I focused more today on my mini, I finally have a bass spar prop (like .025 bass) that flexes evenly and is fairly smooth, ministick did well over 8 minutes, so I'm happy  Smiley
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« Reply #168 on: March 14, 2018, 11:13:59 PM »

The first A6 in this video is the best flying A6 I've ever seen. And as you might guess I've seen all of them.
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« Reply #169 on: March 14, 2018, 11:49:45 PM »

Thanks Bill, that really means a lot coming from you, no doubt you've seen a lot of A6's flying at this point! So I really appreciate that feedback - I thought it flew noticeably slower and was happy with the first time out performance, so good to have that confirmed; I'm building a back up for next week!

Also, the flaring prop (variation of your design) can be tricky to get smooth, but once you get it it's really nice (was easier to tune for the A6, ministick version is harder), that really helps to get the slow climb and long cruise. Really looking to some flying next week, unfortunately I have to leave a little earlier.

Another interesting thing is that the margin of stability stuff indicated benefits of reducing the stab area for a higher aspect ratio stab, which is hard to do for rubber flyers (we like large stabs), but this version flew nicer with the higher AR (but less area) stab.

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« Reply #170 on: March 15, 2018, 12:12:54 AM »

I was also impressed by your A6's flight Larry. Very smooth and stable as well. There are nos signs of Reynold's number problems and it seems like you have hit a winning formula. I've got to admit that I'm no indoor expert but you have shown that with a class formula based on a wing area and weight - Span is the way to go. even though you have the same wing loading - minimum weight and wing area per the rules - the induced drag is clearly lower and this is what I feel has increased your cruise time.

Yes a higher AR stab is more effective - more efficient, but can have hassles where you have a wide speed range, but that's certainly not the case here. It's hard to know exactly but stability calcs for low AR tails - around 3.5-5, indicate efficiencies as low as 40%. This means that 60% of the stab is generating mainly drag. It may help in a dynamic sense with damping but is also extra weight.

No doubt the prop is also contributing to the good performance particularly with the flaring prop working well.

John
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« Reply #171 on: March 15, 2018, 08:30:27 PM »

Thanks John, it is interesting that the wider (higher drag) stab from my older A6 resulted in a very gentle stall, but that problem didn't arise with the new narrower stab (same length, higher AR, slightly lighter), it flies as smooth as glass. That and the wing seem to be examples of less drag in action. This wing/stab combo gave very nice flying characteristics as can be seen in the video, so I'll leave it alone and build another for back up!
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« Reply #172 on: March 15, 2018, 10:46:10 PM »

A General “Newbie” Question: When cross section dimensions are specified with a single dimension, e.g., Micro Rubber cross section is .015”, or prop spar cross section is .025”, does this imply that the second dimension is the same?......or does this mean that the section is round?

In the case of rubber crossection dimensions I would expect the section to be rectangular (including a square being considered a rectangle) and that two dimensions would be specified. Most rubber motors I have seen are not square.

Is a .015” Rubber motor actually .015” x .015”?

Thanks for any clarification on this.

Al
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« Reply #173 on: March 16, 2018, 12:20:51 AM »

Rubber width is usually the specified width x the thickness of the uncut strand which is generally around .040". So in your example an .015" motor would be something like .015" x .040".

This is a particularly bad way to specify rubber b/c the thickness of the uncut strand can vary from the high .030's to almost .050". The preferred way to specify a motor is by length and weight. Then you can specify the strand density in terms of weight divided by a unit length like grams/inch, grams/centimeter, pounds/mile (not really) or whatever you prefer. I use grams per inch which mixes English and Metric units but I like it anyway. Most of the rest of the world uses grams/centimeter which I will eventually switch to if I live long enough.
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« Reply #174 on: March 16, 2018, 10:53:37 AM »

Rubber width is usually the specified width x the thickness of the uncut strand which is generally around .040". So in your example an .015" motor would be something like .015" x .040".

This is a particularly bad way to specify rubber b/c the thickness of the uncut strand can vary from the high .030's to almost .050". The preferred way to specify a motor is by length and weight. Then you can specify the strand density in terms of weight divided by a unit length like grams/inch, grams/centimeter, pounds/mile (not really) or whatever you prefer. I use grams per inch which mixes English and Metric units but I like it anyway. Most of the rest of the world uses grams/centimeter which I will eventually switch to if I live long enough.

Thanks Olbill,

You confirmed what I suspected. Guess I will just determine the density of the rubber I have and work with motor weight as 25% of total weight, and the limits of my home made rubber stripper, for the time being.

I am still in doubt about the .025 in prop spar dimension. Seems like a pretty spindly spar. I have seen prop spars specified as .025 x .060 (not sure which dimension is the frontal dimension). With a single dimension is there an implied Balsa stock thickness or is the spar actually a .025 in round?

Guess I will just have to use my own judgement, as uninformed as that is!

Al
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