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Old Feb 27, 2010, 04:58 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
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Hack & Slash Scratch Build... Advice Welcome.

Hey guys,

After the success of my two previous plank designs I want to put together a conventional plan form.

I'm looking at a 48" span, with fast nimble hack and slash aerobatics in mind, built for those lighter air days (around 15mph +/-5mph), aileron,elevator and rudder, one piece wing, fat fuz to make it building, installation and ground friendly

Wing will be bagged carbon using a MH32 section (its what I had to hand and think it a good versatile section?), fuz either carbon or glass/carbon/diolen mix up over a foam core (maybe lost foam).

Heres a first draft concept drawing, how do the proportions look? Does the stab have to much span?

Your thoughts are welcome

Cheers

Steve
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Old Feb 27, 2010, 09:56 AM
Vitruvian JART
Reed's Avatar
San Francisco
Joined Mar 2003
5,024 Posts
Looks good, here are my quick thoughts:

1. You might want to do some basic calculations regarding the size of the stab and fin. There is no perfect science for it but something about the stab does look a little big to my eye.

2. MH32 has a fairly high pitching moment and won't fly inverted all that well. For aerobatics you might consider the good ol' 6060, RG14, or even 374. Maybe even try a symmetrical section like the 8020.

Good to see another scratch project hitting the boards. Looking forward to this one!
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Old Feb 27, 2010, 10:04 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
West Yorks
Joined Feb 2007
1,110 Posts
Hi Steve

Looks good to me too.

At 48" span and fairly close coupled the stab looks about right to me.

Are you going to fit a rudder? Please!

Not a great fan of MH32 either TBH, I think there are better sections out there, like maybe MG06 or even RG15, particularly if you're using two wing servos.

I'm sure you'll do another great job with it, whatever you decide

Tim
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Old Feb 27, 2010, 10:41 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
Thanks guys

So MH32 is out , I do like RG15, think thats whats on my Mini Dragon. MH32 is no good if its struggles inverted. I'd like to steer away from symmetrical sections, I've played alot with them already.

I'll dig out the coords...

Been tinkering with the drawing, mainly the tail, enlarged/reshaped the fin slightly to accommodate the rudder, given a little more fuz underneath on the tail end, reduced the stabs span by 40mm and increased the chord a little.

and of cause theres going to be a rudder Tim!
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Old Feb 27, 2010, 11:55 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
I've found a script file for RG15a which gives a nice set of coords, cant find what the difference with 15a is tho... any ideas?

I've put it in the drawing and scaled right it gives me an extra 3-4mm in wing depth so should make servo choice easier.

edit...

Apparently RG15a has less camber... good or bad?
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Last edited by Thepasty; Feb 27, 2010 at 12:24 PM.
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Old Feb 27, 2010, 12:27 PM
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Cornwall, UK
Joined Oct 2006
1,089 Posts
Any camber is not going to be good for inverted flight?
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Old Feb 28, 2010, 03:55 AM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
Ok maybe someone will be able to help with this question


The horz stab, I get that mounting it higher than the wing stops the wing masking the horz stab at certain angles of attack and keeps the stab in cleaner air right?

I'm asking because if I were to bring the stab down a bit it would make much easier connection to a snake or the like coming back from the nose. As it is now the snake would come up at a bit of an angle, but seeing as I'm going all moving tail I wonder whether that isnt such a bad thing?

So much to think about

cheers

Steve
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Old Feb 28, 2010, 07:40 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
West Yorks
Joined Feb 2007
1,110 Posts
Quote:
Originally Posted by Thepasty View Post
Thanks guys

So MH32 is out , I do like RG15, think thats whats on my Mini Dragon. MH32 is no good if its struggles inverted. I'd like to steer away from symmetrical sections, I've played alot with them already.

I'll dig out the coords...

Been tinkering with the drawing, mainly the tail, enlarged/reshaped the fin slightly to accommodate the rudder, given a little more fuz underneath on the tail end, reduced the stabs span by 40mm and increased the chord a little.

and of cause theres going to be a rudder Tim!
Hi Steve

Good news on the Rudder

I'm pretty sure the Mini Dragon is RG 14, like your Opus.

RG 15 is slightly more cambered, and slightly thicker, but that makes it easier to get your servos in...

HN 1038 (as used on the Shooting Star) is quite nice too

Tim

Who IS going flying today..
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Old Feb 28, 2010, 11:07 AM
If it can-it will!
cliffhanger's Avatar
Gower South Wales UK
Joined May 2007
2,075 Posts
+1 for the MG06 airfoil, as Tim suggested.
It's what's on my Prodij, and I've got nothing but good to say about it.
It's fast, flies inverted with ease and has great flapperon response for snap flaps/4 axis flying, yet also flies really well in light lift.
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Old Feb 28, 2010, 11:25 AM
Vitruvian JART
Reed's Avatar
San Francisco
Joined Mar 2003
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Starting to look very aerobatic back there!

I've never flown the MG06 but it sure looks like it would do just as advertised. Me likey.

All moving tail rids you of the blanking concern, most likely. Can be fiddly and a little bit less robust than a direct connect, but overall good mechanism for a light aerobat, IMHO.
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Old Feb 28, 2010, 01:54 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
I used the DS-19 on this. I hinged the ailerons at 22.5%. The camber get tweaked a pinch because it used a double tapered balsa aileron. It's EPP so who knows what it really is when it's all done.

I tend to over-size the tail surface a bit to help the glider recover faster and track well on the exit of maneuvers.

I this what you mean by hack-n-slash or are you referring to something different?

Orangutan Prototype (3 min 28 sec)
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Old Feb 28, 2010, 02:14 PM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
Thats exactly the hack and slash I'm thinking of. thats some pretty awesome flying

I wonder how DS19 works inverted with a lot less wind/lift?

Looks good tho

I've found coords for it atleast, one thing I havent been able to do with MG06, anyone know where I can find some?

RE the all moving tail, I wasnt planning on doing a crack and stuff, I was hoping to get it moving by an external link. Fitting a crank etc doesnt sound like fun to me.

Steve
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Old Feb 28, 2010, 02:19 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
Here is another little video of a smaller glider with the DS19 in light lift. Here the ailerons are 25%. The key to making the DS19 work is having the flaperons coupled to the elevator. I use more flaperon deflection couple with down elevator to tune the inverted flight.

I would say that the DS19 needs 20mph winds for full-on hack-n-slash. If the the air is really predictable you can do a lot in 15. But.....I really like hack-n-slash .


For sustained inverted flight in light lift I put the spoilerons on the thottle stick. I can then dynamically feed in spoileron when I'm inverted to maintaining it hands free. This also works great for inverted hovers right in front of you because you can slow it down. It does require a little practice to get used to using the throttle sick all the time. In the big lift of the first video I never used the throttle for any of the maneuvers. They were all done with flaperon to elevator coupling.

Slope Monkey In Light Lift (1 min 49 sec)
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Old Feb 28, 2010, 02:28 PM
Fly fast, Dont crash.
Thepasty's Avatar
Cornwall, UK
Joined Sep 2006
2,459 Posts
Thats not bad considering the wind strength, similar gradient on that slope to what I fly so was cool to see.

What weight was the slope monkey in the vid? Mine will come out heavier I'm sure.

thanks for the info, all good stuff
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Old Feb 28, 2010, 02:39 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
That Slope Monkey is 9.5 oz. It's a little 36"er. Wing loading is around 7.5 to 8 ounces/sq. ft.

Adam
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