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Author Topic: Let's talk E20  (Read 83725 times)
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Stan
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« Reply #975 on: December 31, 2021, 02:07:31 PM »

I agree with some of the guys, let's try to keep things simple. Not bogged down by difficult rules or details.
Let's make it difficult to get much over one minute by using short motor runs so that the models do not need to get super high.
As for motor run times, what is so bad about just setting your normal timer for a 10 sec run and then holding the model the required seconds?
Just count out loud: One thousand one, one thousand and two, and launch for an 8 sec run.
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Slowmatch
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« Reply #976 on: February 10, 2022, 07:06:19 AM »

Some wing developments...

Solid balsa CLG style wing
Root chord: 80mm
Aspect ratio: 7.4
Weight before sealing: 8.9g


Semi-Solid wing
Root chord: 100mm
Aspect ratio: 6.1
Weight before covering: 7.45g

Both have very thin 5% catapult style airfoils. I see the challenge of E20 as the balance between:
- thin enough airfoils
- big enough wing area (low aspect is better)
- structural stiffness
- wing weight (especially to the 1oz minimum for NFFS Rules)

If the semi-solid method is successful then I may adapt if for more camber/undercamber.

Both wings have a lot of dihedral as they are intended for minimal pylon fuselages.

My Ferry 500 conventional stick and tissue wings come out at about 7.5-8g covered with an aspect ratio of 5.33. Hard to beat weight/area - wise but the require 9% airfoils to achieve the required stiffness.
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spr
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« Reply #977 on: February 10, 2022, 12:28:40 PM »

I agree with some of the guys, let's try to keep things simple. Not bogged down by difficult rules or details.
Let's make it difficult to get much over one minute by using short motor runs so that the models do not need to get super high.
As for motor run times, what is so bad about just setting your normal timer for a 10 sec run and then holding the model the required seconds?
Just count out loud: One thousand one, one thousand and two, and launch for an 8 sec run.

We just approved national rules for E20 in Finland. Same as NFFS, except max motor run cut to 15 secs (Flyoff 10 s).  Even 15 s is a bit overkill for 90 sec max.  20 s is way too much for small fields.

We have also competed with 8 s motor time and 60 s max. Fairly simple to reach max, although at shorter run times the Peterborough type FET timers  are giving advantage to electronic timers, because they  fade power already 2 secs before stopping. Helps the transition though Smiley
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Slowmatch
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« Reply #978 on: February 15, 2022, 10:55:59 AM »

I've just started building Ralph's Thermite E20 design.

http://parmodels.com/thermite-e-20-by-ralph-bradley
https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=14519.msg245189#msg245189

I needed a quick 'US Style' model for Luke Goymour's recent anouncement on his new Facebook group (https://www.facebook.com/groups/252734703568141) of 'Buckminster Mondays' - a series of competitions flown to the NFFS Rules. All of my previous E20 models have been for Peterborough Rules comps, either Ferry 500 or Open E20 with an 8 second run and a lot more power. I've also toyed around with the idea of high aspect ratio so I was happy to build Ralph's design as a learning experience and comparison.

My E20 timer can be configured to 20 seconds (and has hard stop, dynamic brake and DT) so I will use that on this model.

So far I have the wings and tail built and covered.

The wing is 5.5lb/in2 quarter grain covered in esaki and weighs in at 8.4g. The tailplane weighs in at 1.34g.


Jon
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Ralph B
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« Reply #979 on: February 17, 2022, 09:06:47 AM »

Hi Jon:

Thanks for posting your Thermite. It's looking very nice so far and I'm interestested to hear how it works out for you.

Ralph B
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Slowmatch
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« Reply #980 on: February 17, 2022, 09:51:04 AM »

Hullo Ralph,

Thanks for making the plan available Smiley
I'm doing a more detailed thread here if you are interested: https://www.rcgroups.com/forums/showthread.php?4073181-Thermite-E20

Jon
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Slowmatch
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« Reply #981 on: April 26, 2022, 06:47:12 AM »

I've now finished my RB Thermite. Weight came to a pleasing 27.8g with a 180mAh and my timer/band burner.

Unfortunately I piled it in while trimming at the Buckminster 'Electric Mondays' E20 comp, but my old faithful Aeromodeller Ferry 500 won the Open Rules comp. This model maxed out at Peterborough last week too. It has a very predictable and powerful climb - turn up, one trim flight and then bosh out the comp flights - lazy flying really!

The Thermite showed good potential with thrust/weight ratio but the first powered flight ended with manic multiple looping into the ground  Roll Eyes

There are comp details on the FB E20 page.


Jon



https://static.rcgroups.net/forums/attachments/6/3/7/9/5/2/a16098281-148-279048554_10166292450350201_2315103590993073124_n.jpg

https://static.rcgroups.net/forums/attachments/6/3/7/9/5/2/a16098263-32-IMG_20220425_114243412.jpg

https://static.rcgroups.net/forums/attachments/6/3/7/9/5/2/a16098271-228-IMG_20220425_114309273.jpg

https://static.rcgroups.net/forums/attachments/6/3/7/9/5/2/a16098267-103-IMG_20220425_114332880.jpg
Let's talk E20
Let's talk E20
Let's talk E20
Let's talk E20
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Slowmatch
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« Reply #982 on: May 01, 2022, 05:41:17 AM »

I took my Ferry 500 out for some lazy flying yesterday. Of course the model decided not to behave as soon as it saw the camera Roll Eyes The wind was mostly thermal infill and from all directions which affected the climb consistency - it's better with a bit more wind. But a lovely afternoon to be flying!

https://www.youtube.com/watch?v=O5yyjdJ_UGc
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Gary Dickens
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« Reply #983 on: May 01, 2022, 06:32:27 AM »

Nice field, that's not Peterborough, is it?

Gary
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Slowmatch
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« Reply #984 on: May 01, 2022, 06:50:13 AM »

Cheers Gary,

Yes it is, but not the usual PMFC Ferry Meadows field. This meadow is just a few steps from the Nene though  Wink


Jon
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Russ Lister
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« Reply #985 on: May 01, 2022, 07:26:53 AM »

Nice flights Jon ... I do hope I can join in one day.

I didn't recognise the field either .... is that near the CL 'embankment'? Never been to that part.
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Slowmatch
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« Reply #986 on: May 01, 2022, 07:49:23 AM »

Not that one either Russ  Wink  This is just one of the meadows near me, not an official spot.

Plenty of E20 activity planned now, you should have a go Cool
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Russ Lister
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« Reply #987 on: May 01, 2022, 07:54:02 AM »

Aah, I see. For all the time I have spent at Peterborough, I haven't wandered as much as I should!
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