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Old Oct 16, 2009, 04:35 PM
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Cromer,Norfolk, UK
Joined Nov 2006
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Designing for storms - or - "throwing design concepts to see if one sticks"

As I sit here, with a 40-50mph wind blasting against my windows, I have the urge to design something specifically for flying in these stormy winds.

The slope I fly off is not a brick lifting super slope, but it is a near vertical sea cliff face of around 200ft (70m) which does a pretty good job (albeit with awful "rotor")

I was initially contemplating something akin to a Jart or Rodent, but I suspect I may not have enough slope to really benefit from the high energy, high loading of that type of model.

So here's my idea, to be built around 55" span with an MH32 or similar section.

Blue foam wing, balsa covered, glassed, with a carbon I beam spar.

Ply/Balsa fuselage, all glassed, solid balsa tail etc.

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Last edited by MCarlton; Oct 17, 2009 at 06:13 PM.
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Old Oct 16, 2009, 04:50 PM
Confirmed Chronic
screamin' eagle's Avatar
Pacific Palisades, CA
Joined Jul 2004
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My Jart was about 45 oz, and it flew very comfortably (and fast) in big winds on pretty average hills. One local hill is only about 100' high, and in 35 mph winds, the Jart was very comfy.
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Old Oct 16, 2009, 04:52 PM
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Wirral, (UK)
Joined Dec 2003
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Nice design, a bit like the old Ridge Racer. What makes it particularly suitable for stormy conditions on a cliff site with an awful rotor?
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Old Oct 16, 2009, 05:00 PM
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Pacific Palisades, CA
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On the foil, you may want to go with something thinned, or one of the Don Ayers foils the guys use at Fermin. A standard thickness MH32 may be prone to difficulty in blustery conditions.
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Old Oct 16, 2009, 05:07 PM
Phil.T-tailer
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Devon, UK
Joined Jun 2003
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Hope there's room for ballast in there - or are you gonna do extra heavy glass?
its the wing loading you need to design for - around 20oz/sq.ft should be fine for 60+mph (well, its worked for me) - Fermin sleds go 30+oz/sq.ft
why not just ballast up whatever other plane(s) you've got?
Phil.
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Old Oct 16, 2009, 05:08 PM
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Cromer,Norfolk, UK
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Quote:
What makes it particularly suitable for stormy conditions on a cliff site with an awful rotor?
Naff all really, just playing with the design while I work out the details really.

I guess MH32 might be a bit "lifty" so perhaps thinner and lower camber might work.

[IMG]why not just ballast up whatever other plane(s) you've got?[/IMG]

Well, I'm a bit short of slope models at the moment, I've got a Talon and a PMP Sierra Mk2. I did have a PMP Stiletto, but it died. The Sierra doesn't like ballast very much, the most I could squeeze in last winter took the loading up to around 20oz/ft2, but it was a pig at that loading, couldn't really get it shifting fast enough.

I was planning on having the space under the wing for ballast, but to be honest, I'm not quite sure what to do, I'm just bouncing ideas around.

Best models I have flown in big winds so far have been an old Obelix, and the PMP Stiletto (which, sadly, is no longer available).

So rather than buy a kit, I thought I'd design my own.
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Old Oct 16, 2009, 06:20 PM
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Pacific Palisades, CA
Joined Jul 2004
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I think you're on the right track trying the build the weight into strength. The trouble I've had flying ballasted models in big wind is that the models are neither designed for the big wind nor the additional weight. That makes landing (which is frequently harder at many sites when the wind is stronger) even more of a challenge.
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Old Oct 17, 2009, 12:21 AM
more casual than stylish....
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Joined Jan 2003
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Can't go wrong with a Jart. BillO's weighed something ungodly light, like around 35 ounces, so there's no reason it can't be done.
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Old Oct 17, 2009, 12:35 AM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,499 Posts
The 60" Jarteron I recently acquired weighs 60 ounces and flies a 300' cliff with 20mph winds like a dream.
No reason your site wouldn't produce great lift for something along those lines.

mw
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Old Oct 17, 2009, 07:40 AM
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Lima, Peru
Joined Jul 2008
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My JART came out at exactly 40oz.

Considering that I put two large patches of kevlar in the wind saddle area, stuffed the nose with chopped fiber, set in the wing joiner tube in the wings and the fuselage using thickened epoxy and chopped glass, used thick aluminum tubes and a solid steel joiner, and made my fuselage out of three layers of 6oz glass with a fourth layer in the nose, apart from using heavy seam tape to join both sides....

I'd reckon it's quite easy to get a JART at 30-35oz, if you try to save weight.

-Alex
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Old Oct 17, 2009, 11:32 AM
racing fool
Elmer's Avatar
Seattle
Joined May 2005
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Quote:
Originally Posted by MCarlton
40-50mph wind blasting against my windows,

near vertical sea cliff face of around 200ft
Sounds like brick lifting conditions to me.
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Old Oct 17, 2009, 01:38 PM
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Joined Aug 2005
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Quote:
Originally Posted by MCarlton
Naff all really, just playing with the design while I work out the details really.

I guess MH32 might be a bit "lifty" so perhaps thinner and lower camber might work.

[IMG]why not just ballast up whatever other plane(s) you've got?[/IMG]

Well, I'm a bit short of slope models at the moment, I've got a Talon and a PMP Sierra Mk2. I did have a PMP Stiletto, but it died. The Sierra doesn't like ballast very much, the most I could squeeze in last winter took the loading up to around 20oz/ft2, but it was a pig at that loading, couldn't really get it shifting fast enough.

I was planning on having the space under the wing for ballast, but to be honest, I'm not quite sure what to do, I'm just bouncing ideas around.

Best models I have flown in big winds so far have been an old Obelix, and the PMP Stiletto (which, sadly, is no longer available).

So rather than buy a kit, I thought I'd design my own.
Since you've flown the Obelix, how about a version with new thin airfoils for the center section and wings?
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Old Oct 17, 2009, 02:54 PM
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Cromer,Norfolk, UK
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Good thinking DT56, its something I thought about doing a while back. Just had a play about with the basic concept.



Perhaps one of the DA sections, or maybe something like MH22 with a smidge of reflex on the ailerons.
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Old Oct 17, 2009, 02:59 PM
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Quote:
Originally Posted by MCarlton
Good thinking DT56, its something I thought about doing a while back. Just had a play about with the basic concept.



Perhaps one of the DA sections, or maybe something like MH22 with a smidge of reflex on the ailerons.

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Old Oct 17, 2009, 06:12 PM
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Cromer,Norfolk, UK
Joined Nov 2006
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I'm going a bit mad with concept ideas here, so I took the design above in a slightly different direction, for no other reason than the notion that a seperate tail would allow me to use a different section (the "obelix" idea would probably need a neutral CmO?) and that I happen to rather like twin booms.

So, this is the final design, which is to be built at an unspecified date. I suspect that on the day it is finished, we will be inundated with 6 months of light winds...



Looking at the nose, I appear to be developing a PNF...
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