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Old Feb 07, 2013, 12:53 PM
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Originally Posted by Sundancer View Post
It's looking very smart Mixer. One question though - does it have a bit more dihedral than that once you fit the struts - I hope so.
mixer - To follow on SD's point, will there be ailerons? If not, I doubt there's enough dihedral for adequate rudder only control. I think you said the wingspan was 43"~44". Assuming a 4" wide fuse and 1.5" of dihedral on each tip, this gives 4.3deg on each tip or 8.6deg total. You'll need about 13~16deg total to get a nice handling model without ailerons

John
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Old Feb 07, 2013, 01:23 PM
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United Kingdom, England, Kent
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Originally Posted by pomroyj View Post
mixer - To follow on SD's point, will there be ailerons? If not, I doubt there's enough dihedral for adequate rudder only control. I think you said the wingspan was 43"~44". Assuming a 4" wide fuse and 1.5" of dihedral on each tip, this gives 4.3deg on each tip or 8.6deg total. You'll need about 13~16deg total to get a nice handling model without ailerons

John
Thanks for the information John. It's good to have someone who knows this technical stuff! There are no ailerons and your point about dihedral had briefly crossed my mind. With the adjustable struts set at minimum length for 1.5", by my very rough measurements, at maximum length, an increase of 0.5", the dihedral should almost double. If it doesn't, then it's easy enough to make a longer set.
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Old Feb 07, 2013, 01:53 PM
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Based on experience rather than calculation, I would normally expect to be using in the region of 2.5" under each tip for a 44" rudder/elevator model. HOWEVER, as the EP9 has a pod and boom fuselage with a lot of side area concentrated at the front I think you might well get away with a bit less - say 1.75" to 2". Being a scale model of an aircraft which doesn't have much you won't want to spoil the looks by using more than you need, so the adjustable struts will be handy, you could start off with 2.5" which should certainly be safe and reduce it a bit at a time once you get the model otherwise trimmed.
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Old Feb 07, 2013, 03:57 PM
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Australia, ACT, Canberra
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Originally Posted by RFJ View Post
Here's the deal NO153Y. To get you started you can have mine - if you collect it. I can arrange to be at home tomorrow afternoon. After all It's only 10,648 miles according to the side bar
Ray
Oh bummer Ray,

It appears that Tomorrow has come and gone. I guess i'll have to pass on your lovely gesture

Mixer, she's starting to look good.

Regards,

Glenn.
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Old Feb 07, 2013, 06:25 PM
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Very kind of you to say so, George - and I put my success so far down the help I have received here; before now I have only had my own brain to answer the myriad of minor questions that crop up! The whole interaction and proven experience of those in this corner has made these past nine months a real joy. This summer (assuming we get one), I even hope to make it to some Vintage meeting where I can fly with others, possibly even others from here.

Hello Colonel Blink. You would be very welcome to come and fly with "even others from here" this summer, myself hopefully STOMPING and Ian of The Travelling Tadpole. We are not exactly a Vintage group but well electrified.KBO.. Sky Jiver. The naughty message will not transmit,what am I doing rong?

Re the Tiggy, you have actually hit the issue on the head - I actually wouldn't mind building something a little more intricate, but the reality is that with my short 'modelling opportunity windows' it would likely be a project that would be too long for me to sustain the effort. One for retirement or when Young Pippa Blinkette trots off to finishing school, perchance. Until then, there are any number of alternatives to consider!!



As it says on the decent-sized mug that Young Pippa Blinkette bought me for Christmas, along side a pic of Brains from Thunderbirds:
".....Of course! Now why didn't I think of that?"
Hello Colonel, You would be welcome to come and fly with "even others from here" myself hopefully STOMPING and Ian with his Travelling Tadpole. We are not exactly a vintage club but gently electriflying and established since 1978. KBO Sky Jiver.
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Old Feb 08, 2013, 08:45 AM
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Originally Posted by mixer421 View Post
Thanks for the information John. It's good to have someone who knows this technical stuff! There are no ailerons and your point about dihedral had briefly crossed my mind. With the adjustable struts set at minimum length for 1.5", by my very rough measurements, at maximum length, an increase of 0.5", the dihedral should almost double. If it doesn't, then it's easy enough to make a longer set.
At 2.5" under each tip, I get 14.25deg total which should be safe for initial flights. Good to hear you can adjust from there. Of course, if you want a more scale look, add some ailerons. I expect the full scale had them and in this size model an HXT900 (9gr from Hobbyking @ $3/ea) in each wing could be easily added I think

You probably know this, but here's the dihedral math in detail

total dihedral = 2 x arctan[(tip height) / halfspan] = 2 x arctan[ 2.5" / 20"] = 2 x arctan(0.125) = 2 x 7.125deg = 14.25deg

The function 'arctan', also referred to as 'inverse tangent', is on most calculators. The button would be labeled as 'tan-1' or 'arctan'.

When working with small angles (<=20degrees), the arctan function can be approximated by the quantity 180/pi (remember the constant 'pi' from grade school math? It represents the ratio of circle circumference to diameter which equals 3.14159....). Like arctan, many calculators have a special button that gives you pi's value.

Here's how the small angle approximation math works for the example above

total dihedral = 2 x (180/pi) x [(tip height) / halfspan] = 2 x (180/3.14159) x [ 2.5" /20"] = 2 x 57.296 x 0.125 = 14.32deg

John
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Old Feb 08, 2013, 02:40 PM
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United Kingdom, England, Kent
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Originally Posted by pomroyj View Post
At 2.5" under each tip, I get 14.25deg total which should be safe for initial flights. Good to hear you can adjust from there. Of course, if you want a more scale look, add some ailerons. I expect the full scale had them and in this size model an HXT900 (9gr from Hobbyking @ $3/ea) in each wing could be easily added I think

John
Thanks for the detailed math John. My old maths master, 'Spider' Beck, would be proud to know that I understood all of it. And he wouldn't even let us use a slide rule or 'guess stick' as he called them, calculators would have given him apoplexy!.

I have seriously thought about adding ailerons and I think it would be possible to do it with a single servo in the fuselage but I'd like first to see how it flies with just rudder / elevator in case there is a weight issue. I could build a second pair of wings later with ailerons and the possibility of using them as flaperons to more closely simulate the STOL performance of the full size.

I'm feeling a little sad as I'm in the last stages of serious balsa bashing - just a few more bits of 1/8"square to complete the elevators then it's all down to sanding, doping, ironing and wire bending.
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Old Feb 08, 2013, 04:15 PM
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Originally Posted by mixer421 View Post
Thanks for the detailed math John. My old maths master, 'Spider' Beck, would be proud to know that I understood all of it. And he wouldn't even let us use a slide rule or 'guess stick' as he called them, calculators would have given him apoplexy!.

I have seriously thought about adding ailerons and I think it would be possible to do it with a single servo in the fuselage but I'd like first to see how it flies with just rudder / elevator in case there is a weight issue. I could build a second pair of wings later with ailerons and the possibility of using them as flaperons to more closely simulate the STOL performance of the full size.

I'm feeling a little sad as I'm in the last stages of serious balsa bashing - just a few more bits of 1/8"square to complete the elevators then it's all down to sanding, doping, ironing and wire bending.
Mixer - Your doing a beautiful job on a wonderfully obscure project; it just oozes personality! Like my Fleester and Champion projects, I also really enjoy getting away from the mainstream birds. A 2nd wing with flaperon capability is a great idea.

I'm also always a little sad when I move beyond the framing stage; that part is always fun while presenting unique challenges, all good for the brain cells. What keeps me going is knowing how great it's all going to look during an overhead flyby with the sun shining through that translucent/transparent covering you put on.

Hang in there; covering always goes faster than you think. We're all with you in spirit and looking forward to the video, pics, and flight report

John
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Old Feb 09, 2013, 02:35 AM
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Ilkley, West Yorkshire, UK
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She's really coming on well now, Mike! Re the ailerons, that reminds me that I really should take the bull by the horns and try the fourth channel myself one day soon.....

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Originally Posted by Sky Jiver View Post
Hello Colonel, You would be welcome to come and fly with "even others from here" myself hopefully STOMPING and Ian with his Travelling Tadpole. We are not exactly a vintage club but gently electriflying and established since 1978. KBO Sky Jiver.
Thanks for the offer SJ! I may well take you up on that come the summer, though your club may have an issue with the fact that though I am insured, I have no A (or is it B?) test......
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Old Feb 09, 2013, 04:40 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by mixer421 View Post
I'm feeling a little sad as I'm in the last stages of serious balsa bashing...
I've found I tend to cover some items whilst the glue is drying on others, so I don't have sharply defined 'building' and 'covering' stages. The downside is that I never manage to take those nice pictures of the whole uncovered structure fitted together....
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Old Feb 09, 2013, 01:25 PM
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She's really coming on well now, Mike! Re the ailerons, that reminds me that I really should take the bull by the horns and try the fourth channel myself one day soon.....
Most of my previous models have been 4 channel and it tends to make you a lazy flier, usually ignoring rudder input. It was only recently with the Fun Cub (one of those awful foam things for the benefit of real model fliers) that I've started to teach myself to use a bit of rudder for cleaner turns. Of course with these modern computer radios, you can cheat and do it with mixing but much more satisfying to do it properly.
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Old Feb 10, 2013, 07:55 AM
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Well I had to take a photo of her 'naked' didn't I? I stitched the wire strut anchors to the wings and put her together with some temporary struts set at 1.5" dihedral - they're too short to give the full 2.5". 1.5" doesn't look too far out of scale but 2.5" will probably not look good so the aileron wings are definitely worth doing later.
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Old Feb 10, 2013, 11:05 AM
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Very, very nice Mixer. Another 1/2" a side wouldn't spoil the scle looks so much and |I reckon it would fly OK with that.
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Old Feb 10, 2013, 09:57 PM
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Originally Posted by mixer421 View Post
Well I had to take a photo of her 'naked' didn't I? I stitched the wire strut anchors to the wings and put her together with some temporary struts set at 1.5" dihedral - they're too short to give the full 2.5". 1.5" doesn't look too far out of scale but 2.5" will probably not look good so the aileron wings are definitely worth doing later.
Beautiful work mixer. Love the pregnant guppie fuse!
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Old Feb 11, 2013, 04:50 AM
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Very, very nice Mixer. Another 1/2" a side wouldn't spoil the scle looks so much and |I reckon it would fly OK with that.
I just hope I can make a good job of covering, time to practice with the solarfilm polyester methinks!

Perhaps the deep fuselage will help with stability because of some pendulum effect?
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