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Old Aug 25, 2014, 08:22 AM
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Aresti 2M development.

Hi Guys,
sorry to have been "off the air" for a while - a combination of circumstances, and none very pleasant I'm afraid.

However I am back now.

OK, some of you have been kind enough to show interest and have been following the development of the Aresti planes (80" and 108") - so here is a bit more news:

The Aresti 108 prototype has been constructed by Radek Munzar and is on its way to UK for Testing. Hopefully all will go well for this monster.

For the Aresti 80 (2M) though, life I am sorry to report, has not been quite so easy.

As many of you may know, I have used the semi-elliptical clipped wing planform - for no really good reason other than I like it, and of course it does carry quite a lot of wing area to the tips in a rather nice way.

But... as I have found out by testing here in Taiwan under a very wide variety of conditions, the planform/wing section combination that I originally designed, can have problems when combined with the double cusped JHSYM10 symmetrical section.

What can happen if you get it "just wrong" is a complex interaction between the chord at the tip, and the tip section itself. On this wing in fact, the section is the same all along the wing with no variation other than the actual chord and hence the actual physical thickness.

To cut a long story short, the ensuing event can be a particularly vicious and almost unpredictable high speed tip stall. Not what you really want to see on an aerobatic plane.

To combat this, what I have had to do is to redesign the proportions of the wing planform slightly, and also as an added safety measure, modify the tip section slightly as well - though its still 100% symmetrical.

Red face dept:

Basically I got it wrong on the 2M, but happily the later designed Aresti 108 does not have this problem.

NewAresti 2M CNC positive moulds are now under construction in China, while the old ones will be destroyed. Actually the new moulds also allow us to make a few mods that will enhance the structural integrity of the plane quite a bit especially the fuselage.

Hopefully I'll have more positive news to report in the very near future.

Cheers,

James.
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Old Aug 25, 2014, 10:41 AM
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James

I may ask the question why this High speed stall wasn't noted in the various flight tests in England ?

The reports sounded like the model ( 400gr heavier as in series) was flown through all it's paces.

http://www.rcgroups.com/forums/showt...ghlight=aresti
Thomas
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Old Aug 25, 2014, 01:37 PM
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taller fuse please

for the crazy guys that like to fly knife edge among us
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Old Aug 25, 2014, 08:18 PM
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Originally Posted by wakumann View Post
James

I may ask the question why this High speed stall wasn't noted in the various flight tests in England ?

The reports sounded like the model ( 400gr heavier as in series) was flown through all it's paces.

http://www.rcgroups.com/forums/showt...ghlight=aresti
Thomas
Hi Thomas - the model on test here in Taiwan was closer to (what would have been) the production version with with moulds directly made from the CNC positives, and it was with those that we did discover a problem.

The planes sent to UK for testing were made from "quick" moulds from new positives and with slightly different wing planform and tip section, as per my post.

Problem is that the quick moulds are not suitable for production, though as you observe, the stall problem seems to be fine and has no occurred on the UK testing.

That at least is one thing good.

I hope to get the new PRODUCTION moulds done in the next couple of weeks.

Thanks for the interest.

Cheers,

James.
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Old Aug 25, 2014, 08:19 PM
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Originally Posted by JGAF View Post
taller fuse please

for the crazy guys that like to fly knife edge among us
I think you'll be happy with it JG, especially if you consider the 108 as the fuse on that one is over 250mm high. Like a good sized canoe paddle in fact.

Cheers,

J.
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Old Aug 25, 2014, 11:38 PM
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That's a bugger James . BUT good on you for putting your hand up and making the right adjustments and doing new moulds
There is a huge amount of work , time , and money goes into to designing and building. And from what I've learn and experienced in my short time , is that what computer shows is not always right. Real life testing always irons the bugs out.
Glad to here the 108 is the goods

Looking forward watching these come to life

Tim.
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Old Aug 26, 2014, 03:16 PM
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Quote:
Originally Posted by Doc James H View Post
Hi Guys,
sorry to have been "off the air" for a while - a combination of circumstances, and none very pleasant I'm afraid.

To cut a long story short, the ensuing event can be a particularly vicious and almost unpredictable high speed tip stall. Not what you really want to see on an aerobatic plane.

Cheers,

James.
but high speed flicks are a big fun aerobatic move?

hope circumstances are getting better for you - I'm told that time is a great healer

Phil.
in a spin - horizontal
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Old Aug 26, 2014, 03:32 PM
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Hi James, very interesting report from you, as you may know I have prototype #4 and it demonstrates this problem very clearly, pull enthusiastically on elevator and it does a snap roll to the left! However I would not have said that it was 'vicious and almost unpredictable'
I did report this to Tony.
That all said, go gentle on the elevator and it is a great model to fly, it does a great inverted flat spin :-)
So I am looking forward to Aresti Mk 2

Yours
Pete

PS Wakumann, this fault was reported, however, we did not understand why my model exhibited this fault and other models did not.
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Old Aug 26, 2014, 03:33 PM
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I agree phil.. We want to do it on a DS punch out.. Ninja stars are one of the fav moves haha
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Old Aug 26, 2014, 03:44 PM
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I agree phil.. We want to do it on a DS punch out.. Ninja stars are one of the fav moves haha
Hey - Ninja Stars rock !

Swoopdown's Ninja Star (0 min 47 sec)


Phil.
full down elevator for recovery...
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Old Aug 29, 2014, 02:11 PM
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Great to see you posting again Jim - hope life is getting better for you.

Regards,
Greg
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Old Sep 02, 2014, 07:39 AM
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See the new pics for the BIG Aresti 108 on the Sloperacer blogspot
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Old Sep 02, 2014, 08:53 AM
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United Kingdom, England, Hitchin
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Quote:
Originally Posted by Pete B View Post
See the new pics for the BIG Aresti 108 on the Sloperacer blogspot
Indeed - impressive, though probably at least a year away I suspect.

http://www.sloperacer.blogspot.co.uk...otype.html?m=1
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Old Sep 02, 2014, 04:00 PM
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Wow. That is impressive
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Old Sep 03, 2014, 11:25 PM
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Originally Posted by Pete B View Post
Hi James, very interesting report from you, as you may know I have prototype #4 and it demonstrates this problem very clearly, pull enthusiastically on elevator and it does a snap roll to the left! However I would not have said that it was 'vicious and almost unpredictable'
I did report this to Tony.
That all said, go gentle on the elevator and it is a great model to fly, it does a great inverted flat spin :-)
So I am looking forward to Aresti Mk 2

Yours
Pete

PS Wakumann, this fault was reported, however, we did not understand why my model exhibited this fault and other models did not.
Hi Pete - glad you can handle the beast! Quick hands mate!

Actually when I tested it here it seemed OK, and it was only when I thought I had it tamed and was yanking it all over the place that the problem emerged.

What happens is that the boundary layer detaches at the tip, then rips down the entire length of whichever wing is affected cancelling all of the lift - with the obvious result.

Couple of pics from Tony Fu of the "Bigresti" which he is now fitting out for testing.
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