Great Planes Siren Hotliner ARF Review - Page 128 - RC Groups
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Dec 13, 2012, 09:56 PM
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hanks for that,I will read up on that as suggested, I have been wondering what I could read to learn this, thanks sdstick
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Dec 13, 2012, 10:42 PM
Flying RC since 1962
sdstick's Avatar
neale.... look for college level physics books
Dec 13, 2012, 11:54 PM
The wheels touch down FIRST??
BJ64's Avatar
...or... just remember that you can always convert height to speed, and speed to height.

I found that front-side slope soaring taught me a little about 'energy management'.

Weave back and forth into the headwind... get some height... do a dive to get speed to do a roll &/or loop... pull out early enough so it doesn't come out of the lift band... then weave back and forth into the wind again to get height... etc etc.

That kinda thing...

Dec 14, 2012, 08:50 AM
Registered User
Hi guys,
Well BJ, now that I understand, I read about the basics of slope soaring, and I have been practicing that with my clouds fly, A bit lite and not really designed for it, but does a kinda job of it. If it had a little more weight and not such a blunt wing I could have some fun at it. However it does thermal halfway decent, any way I digress, I received confirmation of shipping from Tower Hobbies to-day, wont hold breath (it is Christmas) so we shall wait and see.
Dec 14, 2012, 05:32 PM
The wheels touch down FIRST??
BJ64's Avatar
Just find a cliff with a decent breeze blowing in your face, and chuck it off.

Resist using the motor - unless you let it go behind you and you need to get it back.

I notice you're i Beaudesert - not all the far from the coast. Though the beaches around there tend to be rather flat.

Maybe you can hook-up with some local Slope Soarers around your way - see where they fly.

It's a different sort of flying, but a very rewarding one. In the right conditions, you can just about fly a housebrick LoL.

Once you get the hang of it, you'll be utilizing 'energy retention' without even knowing it. Out, up, dive, perform move, into the breeze again, out, up, repeat...

The next and final step from there is "DS"ing - Dynamic Slope Soaring (or 'Kinetic' as our US friends would call it). You need the right shaped geography for that - good frontal lift with a big, calm valley behind it. Then you use the front side to get up initially, and gravity in the calmer area of the backside to build up a sling-shot action to turn loops that generate ever-increasing speed.

Those things are the fastest aircraft in the RC world - current outright record stands at 498 mph - no motor!

Sorry about the slightly off-topic chatter, guys, but the Siren is, after all, a 'glider'. Just happens to have a stankin big motor on it as well LoL. And energy retention makes for 10 min flights out a 3 min battery

Here's some of the Oz boys currently over in NZ having some Slope fun (few of them are Qld'ers too ):

Dec 16, 2012, 02:50 PM
Dir. of Innovation at Alert 5
Demon 6's Avatar
Dec 17, 2012, 09:55 AM
The wheels touch down FIRST??
BJ64's Avatar
Chucked a cheapie KeyChain Cam on the Siren this arvo.

Was blowing a gale above the treeline, but I was just itching for a fly.

To avoid that annoying 'shutter effect' these cams produce, 99% of the vid is 'motor off' dive-bombs - with the occasional upwind settling pass. I reckon it's way faster using gravity v's motor anyways...

A Sirens Point Of View (4 min 30 sec)

Hope you like it.


PS - crank that Amp right up and listen to that thing roar...
Last edited by BJ64; Dec 17, 2012 at 10:30 AM.
Dec 17, 2012, 05:35 PM
Registered User
G;day guys,
Maybe its my end, but the vid wont actually play for me
I have played one of your other vids from there beforer, but not at the moment, will try later.
A question guys, how does the siren glide, not something I have read at all.

Any way hope everyone has a good christmas, big family get to-gether here this year, much work, and much much more for the wife.
Dec 17, 2012, 07:29 PM
The wheels touch down FIRST??
BJ64's Avatar
Works fine for me, Neal.

Anyone else having problems watching it?

Maybe try again, mate...

Dec 17, 2012, 07:46 PM
Flying RC since 1962
sdstick's Avatar
Works perfectly here
Dec 18, 2012, 08:59 AM
Registered User
Hi guys,
Thanks BJ, The vid is working fine, it is 1150 PM, not long home from work and when I opened thread, there was the still in the frame, and it plays fine, this morning was all black!
Anyway good vid good flying and good editing,on ya!
Does the siren glide-thermal?, And if someone can tell me off the top of their head, good c of g starting point, for a novice on this type of plane, I will hunt it down if not.
Spent as much time readding thru the thread as I can afford to-day, and I am seeing 75-80 mm from L/E as a good start point for c of g, thoughts??
Last edited by neale; Dec 18, 2012 at 07:32 PM.
Dec 18, 2012, 10:55 PM
Registered User
Hi again guys,
I was given a trashed out motor and box to use for setting the siren.till mine arrives, so I have dummy fittedit to my planw and started to see what fits where. And I have found I can just, just fit the ESC behind the motor and box, and fit the battery behind that, except I will need to dremal the battery tray somewhat to do it, and that will allow me to move the c of g around a lot more, and allow me to use 3s and/or 4s If I put the battery behind the motor and box, with esc behind that, I think I am only going to be able to use 4s, so as to keep the c of g somewhere reasonable,I think. I am going to be taking out the first cross brace out of the battery tray to do it, but still leaving most of the sides in place
Anyone got thoughts on this in relation to any probs???, I am nervous about all this!
PS I will reract what I said aboutbeing able to use 3s and 4s if I put the esc up front I can only use 4s to get the c of g at around 80mm, and I only have one 4s 2200, but I can get more!!
However If I put the esc at the rear I dont have enough room as the esc is taking all spare room, even to tuck the aileron leads in !!
So it looks like the only way to do this is the esc forward, as a comsequence The furthest forward the c of g will be is at 80mm does anyone think this is a problem??
Thoughts please, as I am wanting a bit of feedback before I dremal!
Last edited by neale; Dec 18, 2012 at 11:36 PM.
Dec 19, 2012, 05:33 AM
The wheels touch down FIRST??
BJ64's Avatar

I have mine set-up with the motor up front, the battery in the 'standard' pozzie, and the ESC behind all that.

Flown it on both 3S and 4S in that config, and it seemed to do ok.

I'm not an expert, but it seems to fly no probs with the CG anywhere around the 75-85mm mark i.e. it's not as sensitive to a 10mm CG difference like some other airframes might be.

The weight of whatever motor you poke in it right up front, of course, could be the determining factor.

The difference in weight between a 3S and 4S LiPo isn't all that much, and if it's roughly where it's meant to be, it's not all that far from the CG (so up or down a few grams doesn't matter all that much).

I'd still be opting for motor/battery/ESC rather than trying to cram the ESC up front. Just my opinion. Yes, it can be a fair bugger to get the aileron wiring to cram down when you put the wing on - particularly if you're running a big-arsed Speedie.

Your DLux 100A is a pretty chunky thing - but then again, my 80A Plush isn't exactly small either. I think mine is longer, whereas yours is a bit more square-ish but a tad shorter. I did a test on my fuze with the DLux 70A, and I reckon it would have gone in ok. I think the 100A is 5mm longer?

I reckon you could get it all in there behind the LiPo without too much hassle. You might have to do a bit of a fiddle to get the wing on - I always have to rearrange my over-long motor wires + ESC to get the darn wing to seat down properly without jagging the aileron wires etc.

That's half the fun


PS - don't be scared to put a few tens of grams of lead up front somewhere (if you can find a place inside the fuse - it's pretty tight in there) to bring the CG forward - if you've got half a kW or more of powerplant in there, it should still fly nicely for you.

Whichever way you decide to go, just be careful not to take too much of the battery bay 3-ply out without doing some FG/Carbon reinforcing. I'm pretty sure that the ply insert adds to the structural strength around that wing saddle area. If you take out the cross-piece, you may need to lay some stengthening matting in that area.

I'd say - go with the motor/LiPo/ESC config without removing the ply cross-piece. Tape a fishing sinker or two up front if your CG is way out of whack. I'd be more worried about the integrity of the wing saddle if you go removing too much wood v's a 10mm shift in CG.

Others may advise differently...
Last edited by BJ64; Dec 19, 2012 at 05:43 AM.
Dec 19, 2012, 05:05 PM
Registered User
Thanks for the input BJ,
I can undersstand what yoursaying about not being as sensetive to c of g moment, and I will consider it a learning curve to try an d get it how I like it Later,Just want to avoid tail or nose heavy, ato the extreme anyway!
Be a bit easier to set up with a slightly smaller esc though.
Looking at it as a whole, I will probably be able to get the esc to drop to the bottom of the fuse, at the rear, if I cut out a little of the ply tray, need to cut more if the batt is at the rear, so I will give it a go as you suggest.
Thanks BJ, good to have a bit of a sounding board.
Dec 19, 2012, 05:25 PM
Flying RC since 1962
sdstick's Avatar

Start with your cg on factory recomendation (55mm). Sailplanes are no fun to fly tail heavy... no fun at all!! Take your time and get a good measurement indoors with no wind. Use a stand and not your finget tips.

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