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Old Feb 28, 2011, 03:05 PM
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United States, CA, Mission Viejo
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Ducted Fan Sailplane Build

This is a build using the fan setup from Knife Liddle for a $100.00 15 pound thrust system.

I am looking at a sailplane with a ready to fly weight target of about 15 pounds. I have been fiddling with this for some time and the build keeps evolving. The next one will incorporate a lot of changes that I keep stumbling over, but I am doing this as a learning curve project.

I am thinking of a wingspan of 150 inches. I want this to fly fairly fast and dont know the airfoil selection yet. I am going to work on the tail first and think ill go with a NACA 0008 for the stab and an 0009 for the rudder.
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Old Feb 28, 2011, 05:24 PM
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good start
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Old Feb 28, 2011, 07:59 PM
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I'm wondering about that exhaust.................is it going to direct enough air rearwards, or is most of it going to be wasted as sideforce? would it be wise to add directional vanes, kinda like the inside of Harrier nozzles? this would make sure that all the air gets pointed in the right direction. could be talking out my a$$ right now, but it makes sense to me that if you don't direct air, it tends to take the easiest route, kinda like any other fluid. just a thought. that exhaust nozzle is very cool though.

Rich
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Old Feb 28, 2011, 09:17 PM
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Pretty neat. What you going to do for the intakes?

bet you had fun sanding that carbon, yuck
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Old Mar 01, 2011, 10:15 AM
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I was going to ask about the intakes ?
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Old Mar 01, 2011, 11:16 AM
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Intake Ducting

My intake would be infront of the fan behind the batteries - right about where GI Joe would be sitting. There will be a big hole where his head would be for the intake.

This is a prototype, and I have already stumbled quite a bit with this build. I want to try to make this one work but I have a lot of changes to make on the next one. There has been a lot of trial and error, and error, and error.

The idea of an intake that can close up I have been tossing around and don't see why that could not be incorporated. I think on this build ill just leave it open but on the next one I think I may try to figure it out. I am just about ready to cut my plug and insert a few inches. I wanted to get a scale like setup and have the ducting behind where the pilot would sit. This got a little small and there is no room for it on this build.

I may try to rig up a test stand to see how the exhuast duct performs.
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Old Mar 01, 2011, 05:33 PM
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I think your exhaust should work just fine. it looks like a good shape for flow, I was just wondering how much you would lose to forward/sideways seepage, without some sort of directional vanes. the only real way to know, would be to place tufts around the edges of the exhaust and see if they blow in a rearwards direction, or if they blow in all directions because of turbulence.

it's very slick though. I like it a lot and it's very nice work. CF is a ^%$#@! to work with, so kudos for the workmanship in form and function.

Rich
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Old Mar 01, 2011, 06:23 PM
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Top Secret - get your Security Clearance if you want to follow along

This is ill bet something that many of you never seen.

I am going to make the fiying surfaces with a solid contoured honeycomb core.

This one is fiberglass that I picked up from JW before he moved away. He said it was from the Skunkworks at Lockheed. I think its about a 4.5 pound density but I am not certain.

I am using some templates same as for a foam core with a hot wire but I have a router on a slide and just run it back and forth with the indicators laying on the top of the templates.

I was debating on if I should disclose this, but here it is. I have been wanting to make a honeycomb cored wing for a long time and this is going to be it.

Stay tuned.... were just getting started.
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Old Mar 01, 2011, 08:11 PM
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Airfoil suggestions

I have not settled on an airfoil for the wing yet. My intent with this build is to ge more than a 3 or 4 minute fly a couple passes and land flight regime.

My picture is some very large and magestic maneuvers with a bit more flight time.

It looks like around an 8" root and a 3" tip - with a 150 inch span. All up weight around 12 to 15 pounds of fun in the sun.
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Old Mar 01, 2011, 08:44 PM
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I love the nomex honeycomb. I got some 1/4 thick OX with I think 282 carbon prepregs as skin, pre made sandwich board. Wonderful stuff!! I built all kinds of slab wings and stabs out of it using balsa LE and TE's. The wieight probably same as 1/4 balsa and and unbelieable modulus.

But a fully airfoil cut honeycomb core is the bomb, its the dream to make wings like that.

I'll be watching you!

You seem to be pretty good and an old hand at composits judging by your work here.
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Old Mar 01, 2011, 09:21 PM
Carbon fiber is our friend
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United States, CA, Lodi
Joined Feb 2001
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That's pretty neat.
The fan looks pretty big sitting in there though and I think it's going to want a lot of air. It might be the case where a 90mm fan could do just as well.

Love the router settup. I like it so much I think I should steal it! I bet it's much faster than a computer operated one.

SC
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Old Mar 01, 2011, 11:46 PM
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St.Catharines, Ontario
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airfoil

here's an airfoil for you to consider. it was suggested by Kevin and is specifically designed for aerobatic gliders, so might be right up your alley. it's a high lift/low drag foil, so worth a consideration at least. here's the foil.
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Old Mar 02, 2011, 07:44 AM
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Airfoils

Thanks Rich

I have had my eye on these airfoils and they keep staying around. I think id like a bit more along the soaring line than the aerobatic, but I am a bit undecisive about this.
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Old Mar 03, 2011, 12:55 AM
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it's the foil I'm using on my 757 build. I figure an RC glider foil is gonna be great for an RC airliner.

you could always go for a classic flatter bottomed foil, kinda like the old Sig gliders, but I figured since you are going EDF, you might want a high lift/low drag semi symmetrical foil to match the power of an EDF. good luck choosing.
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Old Mar 07, 2011, 10:19 AM
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Airfoils

How about the HQ 2,0-12 for the root and a HQ 2,0-10 on the tip?
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