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Author Topic: Let's talk E20  (Read 49189 times)
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PaulBrad
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« Reply #700 on: August 11, 2017, 10:56:25 PM »

Looking very good Dave. The flying weight is just about right for a model that is flown in wind. Being at minimum weight is nice, but when the wind blows it seems a gram or two above minimum weight is good for handling turbulence. Looks like you have a competitive model for sure.

Paul Bradley
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FF Bruce
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« Reply #701 on: August 11, 2017, 11:42:12 PM »

Yes I agree with Paul looks very competitive. Hope you enjoy your little bird for a long time.
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OkieSoar
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« Reply #702 on: August 12, 2017, 12:10:03 PM »

Had another session this AM before the storms roll in and it's getting closer to decent trim.
But most of the design is owed to George Harris' suggestions and coaching and the info you guys have volunteered in this forum.

The next quest is to find another gram or so to take out.
All of the fittings for this plane are 3D printed so finding ways to thin-wall parts is a place to start.
And a bit lighter tail group.

Thank you all for your many suggestions.
- Dave R
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FF Bruce
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« Reply #703 on: August 12, 2017, 12:22:20 PM »

Well maybe you could try and taper your tips on the wing.That will save weight and give you the same effect as thinning the wing.Just a thought I don't think you need to do much.As I said it looks good as is.
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OkieSoar
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« Reply #704 on: August 15, 2017, 08:23:33 AM »

Well maybe you could try and taper your tips on the wing.That will save weight and give you the same effect as thinning the wing.Just a thought I don't think you need to do much.As I said it looks good as is.

A good suggestion - but there's a practical issue at this size.
It's very difficult to cut a taper in low density foam at these chord lengths.
Tried it several times and the tips burn-through erratically due to the very thin TE.
I've made tapered E20 wings with 40psi foam but the weight penalty compared to 15psi foam is significant.
I have successfully cut tapered cores for larger projects and thicker airfoils with this foam.
Trying to transfer this approach back to larger R/C sailplanes with a vertical stab being cured now.
But for E20 sizes, it's tough.
Even a tail for a 2M R/C sailplane is pretty massive compared to an E20 wing.

Replaced the film covered foam stab with a carbon/foam bagged version and cut 0.1g off the tail weight.

And the AG-19ish continues to be a pleasant surprise.
We still have light breezes most days so motor runs have been kept short.
Got 6 flights recently with a 7sec motor run and 41sec DT time.
All the DTs occurred at ~15ft or higher so I would estimate these flights could have approached 50-60s.
Not sure if that's terribly competitive but it felt pretty good at the time!

None of them landed in the dog park!

- D
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Yak 52
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« Reply #705 on: August 15, 2017, 08:48:05 AM »

And the AG-19ish continues to be a pleasant surprise.

Glad to hear that  Smiley Can I ask how you modified the camber and thickness? (I'm guessing XFLR5, Profilli or similar?)

Jon
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OkieSoar
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« Reply #706 on: August 15, 2017, 12:00:51 PM »

Glad to hear that  Smiley Can I ask how you modified the camber and thickness? (I'm guessing XFLR5, Profilli or similar?)

Jon
It was just done in the foam cutting software (GMFC).
I didn't export the coordinates but will work on that in a little while.
The TE is rather fragile and needs to be thickened just a bit.
Once that's done I can post the coordinates somewhere if that's of any interest.

- D
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Yak 52
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« Reply #707 on: August 15, 2017, 01:06:32 PM »

Once that's done I can post the coordinates somewhere if that's of any interest.

Definitely! Thanks - it will be interesting to see whether XFoil likes them  Wink
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Pappy
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« Reply #708 on: November 20, 2017, 09:17:12 PM »

Here is a sunrise flight profile for my Kaw-Liga 1.0 E-20
from earlier this year. I would be interested is seeing
flight profiles from other E-20 models – please post.

BTW, my test field is about 120 ft above sea level. I didn’t
actually launch from under water. Maybe the barometric
pressure was high that day or the calibration of my Fly-Dream
altimeter is off a little.

- Pappy
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Tapio Linkosalo
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« Reply #709 on: November 21, 2017, 12:21:09 AM »


There is a button on the upper line of controls, "H0", that lets you set the zero altitude. Click that button, then click on the graph to a point that you want to represent the zero altitude, and Voila! your altitudes are reset to read correctly!
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Yak 52
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« Reply #710 on: January 10, 2018, 08:44:01 AM »

Can anybody tell me the current rules you guys in the US use for E20 please?

Thanks,
Jon
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FF Bruce
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« Reply #711 on: January 11, 2018, 01:17:04 AM »

Yak 52, if you go back to reply #128 you'll see the rules except for the weight that is now 30gr. and there have been a few new timers made that give you a full 20 sec. run. I don't have one as of yet but they do look good.
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Yak 52
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« Reply #712 on: January 11, 2018, 04:40:58 AM »

These are the rules we are using for E-20 ;  wing span not over 20" (proj.) ,motor- parkzone 3616, battery-160 mAh lipo 1cell,prop 2.5",Luke's timer.Direct drive only,no geared motors, 90 sec. max with 20 sec. resister used for motor run,three flights,fly off's 10 sec. resister and still 90 sec. max,till you win.Motor runs will not be timed but if there is a timer malfunction it can be an attempt.Flight of less than 20 sec. is also an attempt.These are the ones we used at our contest and it worked out well.We will try it again in Aug.  Grin   Bruce

Thanks Bruce. I've quoted that post to bring it up here for my own reference.

Is the Parkzone 3616 the same as the Eflite EFL9052?


Jon
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FF Bruce
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« Reply #713 on: January 11, 2018, 10:23:20 AM »

Jon, that is a good question.I have not seen the Eflite EFL9052 but if it's the same dia. ,length and weight it should work .
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Yak 52
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« Reply #714 on: February 11, 2018, 10:06:30 AM »

Here at the PMFC we are getting a bit of a buzz going about E20 for our summer season of competitions. We've reintroduced the class as a tribute to Ian Middlemiss (Boffin99) who spent so much time developing the 'Ferry 500' version of E20 for small field flying at Ferry Meadows.

We will be flying a fixed motor class to be known as Peterborough E20 and also an Open E20 class where any motor can be used. The fixed motor for this year is a GWS 12mm brushed can specified by Ian, a fairly heavy but very tough set up and a Peterborough FET Timer that gives an 8-9 second motor run.

The hope is that the Open Class will promote developments using more up to date equipment as there has been quite a lot of progress in small motor design for racing quadcopters and the like in recent years.

The draft rules can be found here: http://peterboroughmfc.org/FlyingRules/PeterboroughRulesFF.htm#E20

 and an article here: http://peterboroughmfc.org/technical-articles2018/E20Competition.htm


Jon
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jrc3
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« Reply #715 on: February 15, 2018, 10:25:37 PM »

Hi all, having learned of the EAP-20 (and E20 for that matter) from this thread, I have recently downloaded the plan from the Willamette Modelers Club and have been puzzling over it. The drawing only shows the profile for the ribs in the constant chord section of the wing. Can anyone tell me if the outer panels taper in thickness from the polyhedral break to the tip? Does the high point of the wing remain a straight line from root to tip? I’m trying to envision how the shape of the ribs evolves as the trailing edge angles forward, but I’m not quite seeing it.

Thanks to all who have posted in this thread previously, I have read it all and it has been an education.
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FF Bruce
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« Reply #716 on: February 18, 2018, 01:05:56 PM »

jrc3,I would think that the thickness of the rib would be reduced by the same % as the chord is reduced.As for the high point with just the T.E. moving forward, it to would move forward.The effect would not be much on a model this small. I hope you build one, if I remember the EAP needed a little more tip dihedral and a little more rudder area but is a very good model.
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NeilH
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« Reply #717 on: February 18, 2018, 04:02:45 PM »

jrc3, you might also look at FF Bruce's "mini-e".  The plans are here in the plan gallery and it is a very competitive design.
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Will fly for fun
jrc3
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« Reply #718 on: February 19, 2018, 11:33:05 AM »

Thank you for the replies, they are helpful. Bruce my thinking as well was that the thickness of the airfoil should vary in proportion to the chord, and that the high point would move forward with the trailing edge. I think the source of my confusion is that the top spars are parallel to the leading edge, so would then hit the outer panel ribs at different points relative to the high point. But as you say the effect is probably minor on a model this small.

Any thoughts on washout/in, fin offset, or stab tilt for the EAP-20? The plans say to fly right/right. Does the right climb come from right motor thrust? Sorry for all the questions, but my only recent experience has been with small hlg/clg gliders and this type of model is new to me.
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FF Bruce
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« Reply #719 on: Today at 01:13:13 AM »

For the most part you should go with the tried and true wash out of both tips, not a lot 1\32 to 1\20th then wash in the right main panel 1\16 should be enough.You will then need a small amount of right rudder (very small) possibly some right stab tilt (looking from the back the right side is higher than the left) but just a little and after a few test flights if the glide is good but it still doesn't want to power to the right add a little right thrust.Did I mention put the CG at around 75% and add or remove incidence till you have a nice level glide then start your adjustments. That is what I would do. Hope this helps looking forward to you telling us about your model.       Bruce 
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