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Old Jul 25, 2015, 04:30 AM
Darthwonga is offline
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May the Farce be with you
United Kingdom, Scotland, Dundee
Joined May 2006
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My Sundowner has these specs:

Scorpion HK3-4025 550kV
6S 6000mAh Turnigy nanotech
11 x 14 APC
~2.5kW
Weight 3.62kg

The peak speed I measured with my eagletree gps was 150mph. Landings are uncomfortably fast with no aids, managed to rip out the UC a couple of times when I got it wrong. I tried the drooped aileron approach, which helped a little but reduced roll response. In the end I modified the wing to have split flaps along the whole trailing edge inboard of the ailerons. Has made a huge difference, landing no longer feels like a Formula 1 pitstop! You have to remember to land with power on, like a warbird, it'll fall out the sky if you just kill the throttle on finals. I've got photos of the conversion lying around somewhere if anyone wants me to post them.
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Old Aug 02, 2015, 09:57 PM
ohnow is offline
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Quote:
Originally Posted by Darthwonga View Post
My Sundowner has these specs:

Scorpion HK3-4025 550kV
6S 6000mAh Turnigy nanotech
11 x 14 APC
~2.5kW
Weight 3.62kg

The peak speed I measured with my eagletree gps was 150mph. Landings are uncomfortably fast with no aids, managed to rip out the UC a couple of times when I got it wrong. I tried the drooped aileron approach, which helped a little but reduced roll response. In the end I modified the wing to have split flaps along the whole trailing edge inboard of the ailerons. Has made a huge difference, landing no longer feels like a Formula 1 pitstop! You have to remember to land with power on, like a warbird, it'll fall out the sky if you just kill the throttle on finals. I've got photos of the conversion lying around somewhere if anyone wants me to post them.
I know what you mean. The SD36 was hard to slow down on our paved runway and like others mentioned it will stall on the final turn. When I finally added flaperons with an elevator mix I couldn't believe how much it slowed down. I copied the settings to the larger SD50 and I hope they work.

I'd love to see some pics if it's easy for you. I think your idea is really interesting. I'm thinking of changed from Dean connectors for higher amperage but not sure if they are needed. Can you tell me the style of connector you use and your average amp draw if you know it?

Thanks for responding!
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Old Aug 02, 2015, 10:30 PM
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Update from my maiden failure last Sunday. I could not control the rudder enough to compensate the pull to the left. I tried different expo settings and several taxi tests but before I could do it well enough the tail raised so I had no ground steering but the small rudder had not bit yet so it pulled left off the runway and didn't clear the last fence post. So, I have a damaged leading edge. Could have been a lot worse of a maiden flight!

Going to try a gyro for the rudder next time.
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Old Aug 02, 2015, 10:37 PM
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USA, GA, Atlanta
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Where were you flying?
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Old Aug 02, 2015, 11:45 PM
brushless55 is online now
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big ignore list
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United States, CO, Longmont
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just wondering who has the fastest speeds with the SD50 ?
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Old Aug 03, 2015, 06:44 AM
Darthwonga is offline
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May the Farce be with you
United Kingdom, Scotland, Dundee
Joined May 2006
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Now that you mention the rudder, I remembered that I increased the size of that too - added around half an inch onto it's width. The swing on take off is pretty bad, need to make sure you increase the throttle gradually, don't just throw it open, and use a little up elevator at the start of the roll to keep the tail wheel on the ground until it has enough speed for the rudder to work.

Here's some pictures of my wing mods. The flaps are laser cut from 1/16th ply with plenty of bracing. They can deploy to about 75-80 degrees down, but I've not had the balls to try that in flight - generally I use about 50 degrees. Needs down elevator mixed in, but it makes a huge difference to the landing approach. First time I tried them, I chopped the throttle about 5 feet off the ground, as I normally would landing the Sundowner with out flaps, and it just stopped and fell out the sky (cue another re-gluing of the undercarriage!). I have a load of photos of the modification process if you want to see them, and I can laser cut a set of parts if you're interested - send me a PM if you are.

I've also fitted a BrainCube lighting system (disclosure - I run the business, this model is a company demonstrator), really helps you see where those skinny wings are on approach. I also added black trim to the top of the wing tips for the same reason - the white just disappears against cloud.

Here's a vid taken from a camera on-board the Sundowner, pre-flaps:

Sundowner 50 - First Video

Had to rein it in a bit, there was another guy flying at the time, but there are a couple of speed runs in there.

Cheers,

Olly
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Old Aug 04, 2015, 03:04 PM
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Quote:
Originally Posted by HaventFlownSince2014 View Post
Where were you flying?
Stone mountain radio control flyers.
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Old Aug 04, 2015, 03:29 PM
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@Darth~ That is a helluva job there sir! Looks really solid.
Have you any pics of your lighting systems installed?

@ohnow~ I know that fence line all too well. FWIW I found the sd50 to track a little better in the grass, and to keep that up elevator pressure like said above.
If you ever want to really open her up with some wider airspace, bring it on down to the Patch.
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Old Aug 04, 2015, 03:48 PM
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Nice post Olly. You did a great job on the flaps! I'm about a half pound heavier than your set up but I'm running two 4S 5000 mah in series so it's probably that. Good idea on the rudder too. I guess a gyro wouldn't matter if the wheel or rudder can't bite. I did order a gyro. I haven't toyed with those yet

I tried florescent green tape on the LE to help with the wings disappearing but it didn't work. Tried lights on the LE of the sd36 but they were too small and not bright enough. I have bigger and brighter ones for this model. I'll check out your light setup.

Did you re-enforce anything else due to the high speed and g's?
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Old Aug 09, 2015, 03:34 PM
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Like others have said my stock spinner is not doing well at the high rpms. I know the spinner size is 2.5" and I have a collet I'm using for the stock spinner, but how can I find out the specs I need to buy a tru-turn? I think I may need to replace my current collet because I'm not sure I can find out the size of thread. Hopefully I can get a used tru-turn.
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Old Dec 01, 2015, 12:23 AM
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My name is Geng
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i gave birth to this thread almost 8 years ago... pretty crazy. just want to stop by and say hello.
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Old Dec 01, 2015, 12:52 AM
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Flying Full Size & Fun Size :)
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Howdy! :-)
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