Sigma

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Wayne_H
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Location: Temora, NSW. Australia
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Sigma

Post by Wayne_H »

Hi All,

I recall the Sigma being discussed on the previous forum, but I haven't found any info this time round.

Just wondering if any members have any experience with the Sigma, particularly it's performance 'on the button'.
https://outerzone.co.uk/plan_details.asp?ID=3843

Thanks,
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
GeeW
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Joined: 16 Feb 2018, 19:45

Re: Sigma

Post by GeeW »

I know it is of zero help, but I still have an urge to give a Sigma a go.....

Gordon
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Shaun
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Joined: 15 Feb 2018, 21:49
Location: West Yorkshire

Re: Sigma

Post by Shaun »

The Sigma is on my future re-build list for RCM&E.. I seem to remember it flew very similar to the Impala on the button.

Shaun
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Shaun
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Re: Sigma

Post by Shaun »

Don't forget to build the carry case as well :D
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Wayne_H
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Re: Sigma

Post by Wayne_H »

Shaun wrote: 05 Jun 2018, 23:39 Don't forget to build the carry case as well :D
Roger that!

I've already got the wing, so its just the remaining bits (and the box of course :P ). It will more than likely be another 'foamy' (nice & quick 8-) )

Thereafter, the only challenge will be finding a slope near our new town :shock: .
I wonder how it would go off a bungee....... :o :?
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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Shaun
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Location: West Yorkshire

Re: Sigma

Post by Shaun »

You could also make a banded on power pod - just like we did for the mass Impala launch years ago at Ponte for flat field use.

Shaun
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Wayne_H
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Re: Sigma

Post by Wayne_H »

Well, a decision has been made :shock:

Rather than a strap on power pod, I'm going for a permanently mounted electric motor in the nose, with the power pack located on the CofG. As & when I find a slope, I can elect whether to remove the prop & use a smaller battery for just the Rx & servo(s) if conditions are light, or leave all "as is" in stronger wind conditions.

I've used this method successfully before on a variety of sailplanes up to 5m span.

I'll post updates as construction progresses, including details of the nose modifications.
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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Wayne_H
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Re: Sigma

Post by Wayne_H »

Preliminaries:

wing - already in one piece - is a Union foam job, suitably reinforced. It is almost a direct replacement for the original, simple enough to convert to 2 pieces with a carbon rod joiner.
wing.jpg
The chosen motor - a 2212 6T (2200Kv) - should go well on only 2 cells, using a Graupner folding prop pinched off an old S400 combo. The nose will need to be enlarged "slightly" to accommodate.
nose mods needed.jpg
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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Wayne_H
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Re: Sigma

Post by Wayne_H »

Managed to get a little time over the weekend to sort out the nose modifications:
screen shot of the pdf scan of the modified nose
screen shot of the pdf scan of the modified nose
As you can see, the changes to the side profile are minimal/subtle, but the nose has had to be widened noticeably. I think it will still look like a Sigma in the air :)
Sigma_motor in nose_LR.pdf
It's a "roughie" but you should get the idea.
(187.75 KiB) Downloaded 258 times

All the bits have been printed out & glued onto cardboard for templates. The structure will be 2mm foam for the fuse (with strategic reinforcement) & the tailplane, while fin will be 4mm foam.

I bench ran the motor with a Graupner CAM 9" x 4.5" on 2 cells and there is plenty of thrust. I haven't done a current check yet but neither the 12A ESC or motor got even warm. Looking good so far!! :D
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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Wayne_H
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Re: Sigma

Post by Wayne_H »

Only limited progress to report:
1. Nose configuration & altered formers & fuselage drawing finalised
2. Templates made for all fuselage parts & tail surfaces
3. Sides & doublers cut out
4. Motor bench run with Graupner CAM 9" x 4.5" folding prop - 11 amps on a 2s pack. Should provide a 'brisk' climb :o
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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