Daisy Cutter 60 - Page 8 - RC Groups
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Jun 05, 2010, 06:45 PM
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Polishing and waxing the plug. She needs a few coats of wax still. I will be using PVA so the mould should be perfect. After this, I will construct the parting board:
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Jun 07, 2010, 10:27 AM
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Wind Tunnel Testing

I took the wing to Weldon yesterday to "test" her out in the smooth wind-tunnel conditions. I held the wing in the 30mph wind at varying angles and was surprised by how lifty the wing is. It was satisfying although not scientific.

Gary Legerton and Jason Lilly were there and offered up great advice as always. Thank you guys.
Jun 08, 2010, 01:41 AM
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DC60 Mockup Images

I am closing in on the final design of the DC60 and have some 3d cad images showing the design concept.

The vertical tail section has been selected. I will be using a symmetrical supercrital section. It has generous volume to fit a full size tail servo and will offer a meaty mounting surface for the horizontal stabilizer.

The horizontal stabilizer section is still pending.

The wing plug is finished and locked in. As mentioned before, the wing will easily fit 4 full size servos plus all the wing ballast you can think of.

The fuselage is a very large 4" diameter, with substantial width carried well into the tail boom for superior strength and stiffness. The final fuse may be reduced to 3.5" diameter. One common complaint of the smaller planes is that they flex too much and are difficult to control at high speed and loads. This fat tail-boom design is intended to eliminate that issue. The shape of the fuselage is parabolic for low drag for the high volume it contains. The tail moment is long for added stability.

The goal of this project is utilize airfoils and design elements that are not currently used in DS gliders. Other than the T-tail configuration, this plane will be unique in many ways. The hope is that some of these design elements will prove viable and will open up the possibilities for improved DS planes in the future.

The current specs are as follows:

Daisy Cutter 60
Wingspan: 60"
Wing Area: 480 sq in.
Aspect Ratio: 7.5
Length: 48"
Wing Loading: 48 oz. / sq ft.
AUW: 160 oz. (10 lbs)
Airfoil: nasa hsnlf(1)-0213
Vertical Stabilizer Airfoil: naca/langley symmetrical supercritical
Horizontal Stabilizer Airfoil: pending selection
Jun 09, 2010, 01:08 AM
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Fuselage candidate selected

I worked for several hours on the fuselage shape tonight and have settled on a final design. The specs are as follows:

DC60 Fuselage
Length: 48"
Max Width: 3 1/4"
Width at Front of Vertical Stabilizer: 2"
Shape: Parabolic
Nose Radius: 1/8"

The photos are of a full-size print of the fuselage with the root of the vertical stab represented. I am working out the final location of the wing, with the nose length to be between 12" and 14". It is a very high volume fuselage with room to spare. There are no inside-radius curves in the tail boom to result in flex as you would find with a pod-and-boom type fuselage (i.e. hotliners). You could fit a baseball in the fuselage behind the wing, for mental scale. Wing will be high-mounted for stability since I lack any appreciable dihedral in the wing.

Much is left to work out before the plane is completed, but the end is in sight. I will be ordering the fuselage plug by the end of the week. I plan to sleep it a few nights to be certain.
Last edited by Aerogance; Jun 09, 2010 at 02:15 AM.
Jun 10, 2010, 10:03 PM
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Vertical Stabilizer Templates

I made the templates for the vertical stabilizer today. I will block out some foam and get the tail cut this weekend.

Also, the fuselage plug is on order from the turner. I do not have an ETA yet, hopefully next week sometime.
Jun 11, 2010, 11:02 PM
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Vertical Stabilizer Test Core

The jigging is complete and the first test core cut using the new templates for the DC60 vertical stabilizer. It took only 2 passes to get the wire temp, wire speed and jig dialed in. I should have a useable core tomorrow. Here are some photos of my progress:
Jun 11, 2010, 11:28 PM
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Last edited by Cory; Jun 11, 2010 at 11:30 PM. Reason: oops
Jun 12, 2010, 02:41 PM
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Vertical Stab Core

Cut the core this morning and will work on mylars and cloth later. Should have in the bag tonight.
Jun 12, 2010, 05:41 PM
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Quick update: the core is in the bag.
Jun 13, 2010, 11:17 AM
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Pulled the vertical stab out of the bag. It looks good, but has a slight warp toward the top where excess resin pooled at the TE coupled with a minor shaping issue from the wire cutting process. . I will attempt to sand it to true but may just make another one.
Jun 15, 2010, 07:43 PM
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I need to select a section for the horizontal stab. Current sections are:

Wing: nasa hsnlf(1)-0213 / from 1985
Vertical Stab: naca/langley symmetrical supercritical / from 1966

I am thinking of using something more recent for the horizontal stabilizer. If anyone has a high-speed section they have designed or seen, pm me. Thanks!
Jun 16, 2010, 07:39 PM
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here are the links to the sections used:


naca/langley sym sc foil
Jun 16, 2010, 10:47 PM
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The final piece

I selected the section I will use for the first prototype's horizontal stabilizer. I also settled on the planform for the horizontal stab.

The horizontal tail section is the nasa sc(2)-0012. It has been wind tunnel tested and starts to develop appreciable shock at mach 0.81. It is 12% thick and has zero camber. Oddly, the last 40% of chord is comprised of straight lines. I figure this may make elevator mods easier if anything. I am not planning to use any twist in the horizontal stabilizer, and I can't remember seeing information on using twist on this type of surface.

I mocked up the plane on a 48" steel spar tube and took a photo:
Last edited by Aerogance; Jun 16, 2010 at 11:01 PM.
Jun 16, 2010, 11:30 PM
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Design thoughts

I wanted to make the DC60 distinctive and use shapes and designs that we as RC builders would never look at under normal circumstances.

The main wing airfoil is promising and well tested on full size craft and in the lab. If I get the wing loading right, it should perform very well. It has low drag and no mach effects to mach 0.7 at normal aoa. Since I want the DC60 to fly 350mph, this is well within the section's limits. Assuming the section has good stick feel in varying conditions, it will be used on the DC110 for a shot at 450mph+.

The vertical stabilizer is a symmetrical version of a supercritical rotorcraft airfoil. My thinking is that since this high-speed section is designed to operate in a turbulent environment it should do well in a DS circuit with nasty shear turbulence. It is carries its thickness along most of the chord so it should add considerable stiffness. The larger volume will also allow for easier hardware install. This may be the first use of a rotorcraft section on a DS ship.

The horizontal tail section is a supercritical section with well documented performance characteristics. The horizontal tail will be perhaps the first use of a SC section on a DS plane on a lifting surface. If it blows, I can easily change it. I hope it works because it will open up a complete catalog of unused high-speed airfoils for future planes.

The fuselage shape is a revolved conic section. The advantage of this shape for a ds plane is that it allows for a wider tail boom that should be significantly stiffer in bending and torsion. The conical section is believed to have less drag than other shapes (i.e. elliptical). It is easy to fabricate on a lathe with a template.

The vertical tail has a large root chord so that the transition from the vertically stiff tail to the tail boom will result in less of a weak spot. Many planes break at this location so this I my solution to the problem. The fuselage is 2" in diameter at the leading edge of the vertical tail and I plan to have a decent fillet in this area to avoid the traditional sharp inside radius here. Also, I can fit a full size servo in the tail if I choose.

The wing will be a high-wing (hence the T-tail) but a little research has shown that low wings have the edge at very high subsonic speeds. I believe the high wing will be more stable and therfore be easier to fly smoothly and result in less pilot-induced drag.

The wing has wide root chord and relatively wide tip chord. I learned from the MiniDS that the wider chords are easier to see. If you can't see your plane, you can't go fast. Look at a jetliner at 10,000ft on approach to an airport and you can easily see the wing. Most of gliders dissappear at 2000ft.

These are the philosophies behind the design decisions. Fingers crossed she lives up to my expectations!
Jun 19, 2010, 01:26 PM
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Vertical Stabilizer Testing Jig

I fitted the first bagged vertical stab to my JW so I can flight test it. My JW's speed and performance is well known so it is the ideal test platform. The tail was splined and gooped to the JW fuselage. The DC60 tail is smaller than the stock JW one, but looks close in size so it should still provide sufficient stability.
Last edited by Aerogance; Sep 25, 2010 at 02:12 AM.

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