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Author Topic: What Did You Do Airplane Wise Today?  (Read 96119 times)
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Smithy64
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« Reply #1800 on: September 16, 2019, 05:15:29 PM »

Thanks Jon I will keep ploughing on till I start to get somewhere thanks for the extra info

Neil
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MKelly
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« Reply #1801 on: September 16, 2019, 05:21:32 PM »

New stab for Navion is done - it looks better.  I used Krylon instead of dope to seal it - we'll see how it holds up.

Mike
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Smithy64
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« Reply #1802 on: September 16, 2019, 05:24:13 PM »

New stab for Navion is done - it looks better.  I used Krylon instead of dope to seal it - we'll see how it holds up.

Mike

Looks really good hope it does the trick for you


Neil
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lincoln
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« Reply #1803 on: September 16, 2019, 06:08:34 PM »

As long as we're talking about books, I HIGHLY recommend William McComb's "Making Scale Model Airplanes Fly". At least if you're patient and have a good magnifying glass. Was being advertised in the classifieds of Free Flight Digest, but I don't know if it still is. Last time I checked, there was a sample copy of the Digest at Free Flight.org

My own approach to trimming is to get the model flying well at very low power, adjusting wing, tail and cg as required. Then I add a little power and correct for any new problems with thrust line adjustments. For instance, if the nose comes up too far and the model stalls with power, downthrust is called for. There's more to it than that, but it might give you some idea.

I should think turning either way would be ok with that little stick model.

If the nose bearing won't allow thrust line adjustments, it may be worthwhile to change it.

----------

As far as twisting tails go, hypothetically the diagonal rib solution would be the lightest of the ones mentioned. A balsa core with thin bass laminations over it would be stiffer and lighter than the other way around. Heavily plasticized dope would help, too. Maybe nitrocellulose lacquer instead of dope. Probably, there's a thread around here about plasticizing dope. I know it can work because the tail on my Severely is still straight after many years. But Micro-X doesn't make the dope I used anymore.

-----------

When translating English to American, change Heath Robinson to Rube Goldberg.
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lincoln
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« Reply #1804 on: September 16, 2019, 06:19:27 PM »

P.S. I don't know how many Americans still know about Rube Goldberg. If I'm not mistaken, his cartoons were only published until 1964.
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Indoorflyer
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« Reply #1805 on: September 16, 2019, 11:07:16 PM »

Lincoln, probably the same number who know about "Fibber McGee"
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Jack Plane
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« Reply #1806 on: September 17, 2019, 03:07:36 AM »

Rube Goldberg and Fibber McGee and Molly (Jim and Marian Jordan)...

...reading the Wiki entries for both hugely enlivened my morning - thanks!
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Indoorflyer
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« Reply #1807 on: September 17, 2019, 08:46:30 AM »

I always get a kick out of the reference, especially "Rube Goldberg." Pursuant to this topic, I looked up an airplane that I saw a couple of times at an annual Phoenix, Arizona airshow back when  I was a young schoolboy...my Mom referred to the "Goldbug" as the "Goldberg." It was rather rough looking, but the builder flew it all around, attending a bunch of fly-ins and airshows.  It would make a good FF model. It went through several rebuilds, this is the version I saw.  (Replogle Goldbug)

http://www.aerofiles.com/rep-goldbug.jpg
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Smithy64
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« Reply #1808 on: September 17, 2019, 09:14:55 AM »



I should think turning either way would be ok with that little stick model.

If the nose bearing won't allow thrust line adjustments, it may be worthwhile to change it.
-----------

When translating English to American, change Heath Robinson to Rube Goldberg.


Thanks Lincoln I took your advice and rebuilt the fuselage and changed the nose to add a thrust line adjustment I thought it was a worthwhile modification even if I just learn from the process.

I’d never heard of Rube Goldberg but I see his work is very similar to Heath Robinson, excellent stuff, everyday is a school day.

Neil
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Smithy64
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« Reply #1809 on: September 17, 2019, 10:11:21 AM »

Redesigned stick plane with some downward thrust built in this time in the hope I can get this one to fly better, it seems to glide well so I may try it later with power.

Neil
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LASTWOODSMAN
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« Reply #1810 on: September 17, 2019, 12:36:32 PM »

     Hi Smithy64.  What is your all up model (what is that model? ) weight in grams, including prop, and what is your total  wing area in square inches?    Huh  This will give us a better idea in order to understand why it won't fly, and help us to give you sage advise.
Also what kind of motor, size, strands, etc.   Have you balanced it on the plan CofG ?  How much clay weight did you add, if any?

LASEWOODSMAN
Richard
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Smithy64
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« Reply #1811 on: September 17, 2019, 04:08:32 PM »

Did some more test flying with at least a little success 2 slow motion video links attached to my Instagram account, so likely only viewable if you have a Instagram account. Later flights I managed to get it to turn but my battery went on my phone so no video of those. Couldn’t get it to climb very high but at least it was fairly stable. It did seem to climb better the other day with the 6” prop wasn’t as good climbing with the 5” it now has. It was fun and as you see I had amazing views

https://www.instagram.com/p/B2hlSmkgmy3/?igshid=1ffcxqz7qvdsd
https://www.instagram.com/p/B2hjn19Aopx/?igshid=1cwk79krufb37

Neil
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Smithy64
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« Reply #1812 on: September 17, 2019, 04:28:04 PM »

    Hi Smithy64.  What is your all up model (what is that model? ) weight in grams, including prop, and what is your total  wing area in square inches?    Huh  This will give us a better idea in order to understand why it won't fly, and help us to give you sage advise.
Also what kind of motor, size, strands, etc.   Have you balanced it on the plan CofG ?  How much clay weight did you add, if any?

LASEWOODSMAN
Richard


I can answer some of that, about 20.5g total weight, 32 square inches wing, 2g of weight added to nose the rubber I’m a bit vague on, all I can tell you is its double strand. I don’t think it showed the CofG on the plan.

Neil
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LASTWOODSMAN
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« Reply #1813 on: September 17, 2019, 05:07:18 PM »

    Hi Smithy - great flights in your two videos above.  Shocked  Thanks for the information on your plane.    It looks like you are well on your way.   Cool

LASTOODSMAN
Richard

PS    Your two videos worked for me, and I do not have an Instagram account.  Smiley
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Smithy64
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« Reply #1814 on: September 17, 2019, 05:22:36 PM »

   Hi Smithy - great flights in your two videos above.  Shocked  Thanks for the information on your plane.    It looks like you are well on your way.   Cool

LASTOODSMAN
Richard

PS    Your two videos worked for me, and I do not have an Instagram account.  Smiley

That’s good to know I’ve never shared a link on Instagram before.

Neil
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RolandD6
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« Reply #1815 on: September 17, 2019, 05:59:56 PM »

   Hi Smithy - great flights in your two videos above.  Shocked  Thanks for the information on your plane.    It looks like you are well on your way.   Cool

LASTOODSMAN
Richard

PS    Your two videos worked for me, and I do not have an Instagram account.  Smiley

Worked for me too and I do not have any kind of social media excepting HPA of course.

Interesting to see the flights in slow motion. How did you do that?

Paul
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Smithy64
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« Reply #1816 on: September 17, 2019, 06:07:15 PM »

   Hi Smithy - great flights in your two videos above.  Shocked  Thanks for the information on your plane.    It looks like you are well on your way.   Cool

LASTOODSMAN
Richard

PS    Your two videos worked for me, and I do not have an Instagram account.  Smiley

Worked for me too and I do not have any kind of social media excepting HPA of course.

Interesting to see the flights in slow motion. How did you do that?

Paul


Slow mo mode on my iphone it’s incredible what you can do with a phone these days

Neil
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lincoln
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« Reply #1817 on: September 17, 2019, 06:19:22 PM »

The videos worked for me.

If it stalls like that in the glide (or at low power) as well, maybe you just need some down elevator (or less up elevator). Or else you're throwing it too hard.

If it does NOT stall in the glide, then you might need more downthrust. Alternatively, it might help to move the c.g. back slightly and use a little down elevator. Or, maybe you're throwing a bit too hard.

It helps a lot of you can adjust the thrust line between flights, while you're still at the field.

Here's one way to make an adjustable prop bearing:
https://static.rcgroups.net/forums/attachments/2/8/0/3/6/a1955320-101-sleek-streek-sht-1.gif
You could probably use regular solder or even lash everything with thread and use CA. Or bend up a u shape from the top of a soda can or something, with two drilled holes.

Another nice nose bearing:
http://www.endlesslift.com/wp-content/uploads/2011/10/Cloud-Tramp-024.jpg

You could probably make something similar from a paper clip if you're good at bending wire. Here's a drawing of a wire nose bearing as seen on some really light indoor models. I'm sure it would also work fine if made from a paper clip.
https://freeflight.org/Library/TechLibrary/ThrustBearings.pdf

The old plastic nose bearings as found in those models from the dime store that come in a plastic bag work ok, and they can be gently persuaded to accept thrust adjustments. You might have to adjust again after a while, I suppose.

Anyway, there are about a bazillion ways to do it.
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Knightflyer
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« Reply #1818 on: September 17, 2019, 07:14:03 PM »

P.S. I don't know how many Americans still know about Rube Goldberg. If I'm not mistaken, his cartoons were only published until 1964.
My teen boys refer to Rube Goldberg pretty regularly, but they're gamer geeks.
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lincoln
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« Reply #1819 on: September 17, 2019, 08:21:55 PM »

Lincoln, probably the same number who know about "Fibber McGee"

The only thing I know about Fibber Mcgee is what his closet sounds like when you open it. I seem to remember hearing the sound effect on a radio show called Music to Go to the Dump By, which, at least once, we listened to while driving to the dump.
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Prosper
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« Reply #1820 on: September 18, 2019, 09:41:39 AM »

Today I flew my 1/20 scale Praga Air Baby model, 21.6",549mm wingspan. https://youtu.be/h2EWlhbQ8_8 . It has pendulum ailerons and is powered by a coreless electric motor fed by a supercapacitor. Just like its first flights yesterday, it put on a good demonstration of Crazy Flying. The model is a hybrid: the wings are the (unpainted) scale wings intended for use on the finished model, but the remainder is balsa sheet lashed up for the test flights. It's all held together with CA and sticky tape.

I'm completely puzzled by the weird rock 'n roll behaviour. I've never had a pendulum setup exhibit such behaviour before, and unless I can correct this there's no point in going on to turn the lash-up into a proper scale model. It is amusing to see though - yesterday was windy and the model made some remarkable helter-skelter flights, rocking and rolling all the way.

Stephen. P.S. the nose broke off in the landing shown in the video. It's not intended to dangle there like that Smiley.


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Howie911
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« Reply #1821 on: September 18, 2019, 10:07:27 AM »

Anyone remember the board game "Mousetrap"?  Very Goldbergesque (I just made up that word).  It might have even been fashioned after one of his drawings.   Grin 
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strat-o
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« Reply #1822 on: September 18, 2019, 12:36:08 PM »

Stephen, the stability of your Praga prototype is a head scratcher.  Almost like PIO (pilot induced oscillations) where the pilot reacts to turbulence but by the time the control input has been made the plane has already corrected itself.  It could be that the mechanism has some friction and is somehow responding late.  It's like it is always behind the curve in correcting itself.  Kind of like phugoid oscillations in the roll axis.

Marlin
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lincoln
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« Reply #1823 on: September 18, 2019, 03:07:51 PM »

I wonder if the system is oscillating at a resonant frequency. If so, you could try magnetic damping. Just an aluminum or copper bit moving back and forth very close to a powerful little magnet. If this doesn't make sense, try sliding a rare earth magnet over an aluminum plate or down a copper or aluminum tube. It will work with much thinner aluminum than shown in this video I found:
https://youtu.be/1RI9lkRg3m8?t=130

Warning: I didn't watch the whole video, though I doubt there are any horrifying surprises in the rest of it.

Damping grease of a suitable grade might work if the mechanism includes a bearing with a fair amount of contact area,  but it will give somewhat different results in cold weather than it will in warm. You might be able to extract some from the knobs of a dead stereo or a broken camera lens mechanism.
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Prosper
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« Reply #1824 on: September 18, 2019, 04:58:43 PM »

Thanks for the comments Marlin and lincoln; yes, this is what I'd hoped people would say, because it chimes with my thinking. Hysteresis; resonance. . .The wings are high aspect-ratio and are (relatively) heavy, meaning lots of inertia. The pendulum system isn't the lowest-friction example I've made, but I do know I've made 'stickier' installations without this phenomenon occuring - and on low-wing models come to that, and with wings just as heavy. This rocking behaviour occurs infallibly, whether the model is climbing, diving, turning. . .it does it all the time. The model can even perform a full stall and recover straight ahead - but with the wings rocking all the while Shocked . Somehow the average of all these rocks and rolls allows it to stay airborne in quite gusty breezes. . .but it's not a "good look" in scale terms!

I deliberately chose a low aileron deflection because the ailerons are very long (more than 1/2 total wingspan). Previously I have always gone for an aggressive aileron deflection, such as 30° up aileron with 15° tilt of the model. There is something about the whole setup. . .inertia; system delay. . .I'm hoping that I can 'break the chain' by some simple means such as shortening the pendulum or changing the bobweight. Otherwise the project's a goner. Maybe magnets and al. dampers are too much for a model that's already overweight. . .but I haven't watched the video yet lincoln.

Stephen.
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