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Schueler DG505 FES

Here is where you can discuss to your hearts content the merits of sustainers.
Jolly Roger
Posts: 489
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Schueler DG505 FES

Post by Jolly Roger »

Last Summer I converted my Schueler DG505 to FES. Now that I've finally tested it yesterday I thought I'd share why and how I did this.

First, why?

Well these photos show me launching the DG in the Lake District exactly 10 years ago in very marginal conditions. 20 minutes in, the lift died completely, the model sank quickly out of sight, there was a pause of about 10 seconds, and then a sickening crunch. Honestly, I've relived that moment so many times.

Luckily (!) it landed vertically on a wingtip, so damage was limited. But I resolved never again to launch the DG if there was the faintest doubt about the lift. Result? The poor DG got air under its wings maybe twice a year.
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Jolly Roger
Posts: 489
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Schueler DG505 FES

Post by Jolly Roger »

Fitting an FES seemed like the answer: I would be able to fly my lovely DG safely in a much broader range of conditions, and feel far less stressed while doing so.

You can spend a lot of money on highly-specced, high power electric gear, but I just wanted a simple, cheap set-up that would give me enough power to climb positively if the lift failed, like the sustainer motors regularly fitted to full size sailplanes. In my experience 60W/lb is fine for this.

So running through some numbers, I estimated the new AUW of the model would be about 30lbs, so I'd be aiming for 1800W total power. I have loads of 5s packs so adding two in series to get 10s seemed about right, giving about 40V off a full charge. So I'd need a motor and prop that pulled about 45A to hit my 1800W target. I also wanted to limit myself to a 15" prop as this would be fairly unobtrusive and potentially allow enough ground clearance for a ROG take off from a smooth surface if the chance arises.

This is where it got a bit tricky as there still isn't that much data to guide you in choosing a specific motor, but I did some sums, read a heap of motor reviews and reckoned about 245kV would work ok.

This was my final set-up:

15" x 10" folding Aeronaut prop £15
Hobbyking Turnigy Aerodrive SK3 - 6364-245KV Brushless Outrunner Motor £64
AeroStar Advance 120A HV (6~12S) Brushless ESC (Opto) £88
10s LiPo (made from 2 x 5s 4500mAh packs in series) £60 each

Total cost: £287 (it was much cheaper last Summer).

I can't describe the joy in removing the 2lbs of lead ballast from the nose - basically the weight of the new motor, prop and shaft. In other words, the weight gain of the model was more or less just the weight of the LiPos.

Next came the question of whether to cut the nose off. Nope, I couldn't do that. It's just too pretty. So I extended the motor shaft with some steel rod and a coupling, then glued a ball-race in the nose to keep everything secure and vibration free.

I also added a large compression spring so that when I loosened the 4 mounting bolts, the motor would retract itself into the model, hiding the prop shaft from the Scale Police etc. "Move along gents, nothing to see here..."
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Jolly Roger
Posts: 489
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Schueler DG505 FES

Post by Jolly Roger »

In action, the whole system works exactly as I hoped.
The prop smoothly spins up to speed and the model sets off up its 30 degree glide path with the faintest of noise.
All the electric components run coffee-cup warm, and checking the LiPos after each flight suggested they could give about 15 x 1 minute relights, with 30% charge to spare. Static power is 1850W with fresh cells. The prop is invisible unless you look closely on a flyby. It can be removed in about 30 seconds by undoing one bolt.

Lithium beats lead every time!

Looking forward to lots more air-time with my DG. ;)
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Elliot Howells
Posts: 292
Joined: 18 Mar 2015, 08:18
Location: West Wales
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Re: Schueler DG505 FES

Post by Elliot Howells »

Rog,

that's superb, so pleased for you, it is, without a doubt the best investment/ insurance you can make for a large glider.

I'm no pro, but if you take my advice, get an extra long FES compatible retract if you plan to ROG, Rog. ;)

My 1/3 ASH26 is now my favourite model and I can flat field her anyday which is just as well being the only tug pilot in my club...

I have also converted a KV Discus (4m) and my KV B4 (4.5m) both currently untested, I've also fitted bungee tubes for self launching off the slope which I hope might aide the 2 latter models as they definitely won't ROG due to prop diameter.

Ell :)
Jolly Roger
Posts: 489
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Schueler DG505 FES

Post by Jolly Roger »

Cheers Ell, really good to hear from you.

I think we’re both preaching to the converted here :D . Couldn’t agree more that it’s the easiest way to maximise safe stress-free flying with big heavy gliders.

Thanks for the idea about the FES retract. I assumed these included a clever mechanism so that they could unfold as they lowered to give the extra clearance, meaning you wouldn’t need to lengthen the aperture and doors in the bottom of the fuselage. But no, it looks like they are just normal retracts with longer arms. Disappointed sigh.

I’ve actually extended the arms of my FEMA retract already to get the scale high ground clearance of the DG1000, and this gives 2” ground clearance below the 15” prop with the fuselage running level, and 4” with the tailwheel on the ground. This doesn’t sound enough for a grassy field, so I either need to extend the arms further and lengthen the aperture and wheel doors, or re-engineer and build a new mechanism. Or build a dolly...which I think look rubbish. Even as I type this I know I won’t do any of these things. 😉 I reckon I’ll just keep sloping it for now.

While we’re talking FES, I can’t believe none of the German manufacturers are yet providing scale FES hub and prop assemblies with the beautifully-streamlined, fully concealed hinges and the flush-fitting blades. More and more full-size are being equipped with FES, so the range of model sailplanes will only expand. Maybe they’re worried that the spinner needs to be profiled to each model, but I reckon a generic design in a range of popular scales would be workable.

Rog (but only off tarmac😁)
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Philkiteflyer
Posts: 103
Joined: 17 Mar 2015, 21:53
Location: Invercargill, NZ

Re: Schueler DG505 FES

Post by Philkiteflyer »

Or you could bungee launch FES off to get some flying height and then engage the FES - like the EDF boys do . .

Just a thought,
Phillip C
(Still procrastinating inNZ Lockdown)
"Keep it simple stupid"
Jolly Roger
Posts: 489
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Schueler DG505 FES

Post by Jolly Roger »

Philkiteflyer wrote: 28 Aug 2021, 12:16 Or you could bungee launch FES off to get some flying height and then engage the FES - like the EDF boys do . .

Just a thought,
Phillip C
(Still procrastinating inNZ Lockdown)
It’s a good suggestion Phillip but I’m not sure I could be bothered with the faff of setting out/collecting up the bungee and making a release mechanism. I’m finding the older I get the more I value easy experiences. Models that get flown the most are those I can pick up, fully-assembled from my workshop. Models that take longer than 5 minutes to assemble rarely get flown. I know, lazy aren’t I?

Hope you’re coping with lockdown ok. My sisters are going stir crazy in Auckland. :(

All the best,
Rog
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Philkiteflyer
Posts: 103
Joined: 17 Mar 2015, 21:53
Location: Invercargill, NZ

Re: Schueler DG505 FES

Post by Philkiteflyer »

Jolly Roger wrote: 29 Aug 2021, 22:45
Philkiteflyer wrote: 28 Aug 2021, 12:16 Or you could bungee launch FES off to get some flying height and then engage the FES - like the EDF boys do . .

Just a thought,
Phillip C
(Still procrastinating inNZ Lockdown)
It’s a good suggestion Phillip but I’m not sure I could be bothered with the faff of setting out/collecting up the bungee and making a release mechanism. I’m finding the older I get the more I value easy experiences. Models that get flown the most are those I can pick up, fully-assembled from my workshop. Models that take longer than 5 minutes to assemble rarely get flown. I know, lazy aren’t I?

Hope you’re coping with lockdown ok. My sisters are going stir crazy in Auckland. :(

All the best,
Rog
I seem to remember you were in the country and flew from a neighbours field? Would he mind if you had a wee box (with the bungee inside) fixed to a fence post.
Then all you need to do is go over, pull the bungee out, stretch it. Just trying to get you in the air with less fuss . . . :mrgreen: :mrgreen:
Well if thats too much work for you, the only aother option is a dolly, with a drive system to get it back to you. Something I've been thinking about trying myself.
But you are getting more flying than me, weather has been wet, windy and cold for three weeks before our current lockdown. But your sisters are in for another 2 weeks :cry: :cry: . We move up into level 3 on wednesday, but that just means takeaways are available. Still no flying.



Cheers all
Phillip C
New Zealand
"Keep it simple stupid"
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