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Old Nov 17, 2012, 08:17 PM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
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Build Log
POP = Pitch-O-Plank

After a bit of discussion over in the Q&A thread starting at #110, I went ahead and cut the parts for the build. Sense this was my first time using my machine in a "parts run" there were a few little bugs that need to get worked out, but that is what prototyping is all about right? Anyway, I'll start out with a few pics of the parts and a vid of my home brewed CNC router doing some cutting.

I am rather pleased as to how well the individual pieces fit with each other. The second pic of the tail is a good example. Just loosely slid in place, they all fit rather snug. The 2 white foam pieces are inserts for the tail and we'll get to why they will be installed as the build goes on.

If you watch the video, note that I didn't edit in any music, so unless you like to hear the whine on a dremel tool, you might want to turn the volume down a bit. The vidoe starts off with a tool "touchoff" that tells the Z axis where the top of the material is so it knows how far to move the bit into the work. The rest is just the machine following the tool path from the cut file.

I'll start cleaning up the burrs and gluing parts tomorrow. Would maybe start on it tonight but I keep hearing this faint cry from the ice box. Think it's them Sierra Nevada Torpedo's calling my name and I really should investigate the phenomenon in some detail.

Mark

CNC First Run (4 min 53 sec)
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Last edited by Quick61; Nov 18, 2012 at 11:50 AM. Reason: Fixed broken html code.
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Old Nov 17, 2012, 09:26 PM
Herk
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Not commenting on the design, but definitely interested

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Old Nov 17, 2012, 10:19 PM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
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Quote:
Originally Posted by HerkS View Post
Not commenting on the design, but definitely interested

Subscribed --- Herk
Hey Herk, feel free to comment all you might like. This is after all a prototype / experiment and I will consider it a relative success if it makes it to a crash landing / re-kitting under it's own power. That's one of the reasons it's only a ~36" span and simple construction. Just a prof of concept build. If it works, great, and if not, we'll figure out what is stopping it and make it work. Shiny?

Mark
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Old Nov 18, 2012, 04:13 AM
I don't like your altitude
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Damned infernal machine,takes all the skill of cutting a myriad of parts by hand away and what about those poor guys who labour to make exacto blades all out of workand the sticking plaster industry bet you never gave that a thought.
I want one
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Old Nov 18, 2012, 08:34 AM
Herk
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Hey Mark, I didn't mean that I was withholding comments. I just don't have enough info to add anything very meaningful. The plane's geometry is a bit of a guess from the picture, and I don't have any info on the airfoil.

Just looking I agree with Kent that you will need a normal elevator. Estimating from the picture, up elevator movement on the pitcherons will mostly just reduce the lift of the wing, but have little effect on pitch. If the wing had substantial sweep that kind of control setup would probably work better.
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Old Nov 18, 2012, 11:44 AM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
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Hey Stuart, they are easy enough to build, and even easier to buy. Yea, the Exacto industry may of taken a little hit, though I still use one to cut the tabs. The micro end mill guys on the other hand picked up a new customer. Those .050" end mills are not the cheapest things in the worlds and I have broken 2 already. Bone head moves on my part, setting up the machine for one and way to fast a feed rate in hard material for the other.

Herk, understood. I'll get a pdf up later today of the layout and dimensions. I have yet to draw it as the only 2D CAD work so far has been the cut files. As for the airfoil, I selected the Wortmann FX-66-H-120. Charles Fauvel used this series airfoil on his AV-36 and others,( FX-66-H-159 - the profile at 15.9%). I went with the 12% thickness as the thinner section has MUCH better results in XFLR at the lower re numbers and remained thick enough to make for an easy build. Not shown in the first pic are the elevators. Those have been added as well as increasing the height and length of the fin, as it just seemed a bit small to me.

Mark
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Old Nov 18, 2012, 12:37 PM
less is more
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United States, CA, Marina
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It's a cool tool

The great thing about CNC over laser cutting is the choice of materials. Lite ply, Birch ply, fiberglass plate. It's all do-able.

It would be nice to make custom control horns on the elevons that are integrated into a rib, thus allowing perfect geometry to hinge line and such.

Kent
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Old Nov 18, 2012, 01:18 PM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
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Quote:
Originally Posted by Knoll53 View Post
The great thing about CNC over laser cutting is the choice of materials. Lite ply, Birch ply, fiberglass plate. It's all do-able.

It would be nice to make custom control horns on the elevons that are integrated into a rib, thus allowing perfect geometry to hinge line and such.

Kent
Yes, you are correct, a router will take on material that a laser hes trouble with, though I am dreaming of a 40 - 80 watt laser for a future project. As for now, I'm very seriously thinking about a 2W blue solid state laser to mount on the Z axis so I can engrave part #'s on the pieces as they are being cut. I think that would be a nice feature. A 2 watt, properly cumulated, will make a nice burn mark on wood and such rather quickly.

For the elevators on this one, I am going to drive the hinge rod it's self to move the control surface, so the geometry should be about as shiny as it gets. As a plus, there are no external horns, cranks, pushrods, etc.. Note pic of ribs in the first post and CAD drawing below.

Mark
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Old Nov 18, 2012, 02:03 PM
less is more
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Be careful with the elevator throws. Because it is a plank, it will not need much elevator throw to make it jump. That is, once it is moving. I would think that 10 degrees up and down would be plenty.

I'm still having trouble hand launching the Plank 101 in calm air. As in, it can't be done. I just dives straight down. I've seen other Planks suffer the same problem. Because of this, for the first test glide, I'd suggest a low force bungee launch.

Launching in good ridge lift with some up trim is no problem.

Kent
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Old Nov 18, 2012, 03:27 PM
I don't like your altitude
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For the elevators on this one, I am going to drive the hinge rod it's self to move the control surface, so the geometry should be about as shiny as it gets. As a plus, there are no external horns, cranks, pushrods, etc.. Note pic of ribs in the first post and CAD drawing below.

Mark[/QUOTE]

Like it!I prefer a clean wing if possible.Have you decide on material for the hinge rod?
Stuart
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Old Nov 18, 2012, 03:40 PM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
Joined Jan 2011
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Quote:
Originally Posted by Stupot46 View Post
For the elevators on this one, I am going to drive the hinge rod it's self to move the control surface, so the geometry should be about as shiny as it gets. As a plus, there are no external horns, cranks, pushrods, etc.. Note pic of ribs in the first post and CAD drawing below.

Mark
Like it!I prefer a clean wing if possible.Have you decide on material for the hinge rod?
Stuart[/QUOTE]

3mm CF tube - it's what I have on hand and has worked well in the past on such things as full flying tails and the like.

Mark
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Old Nov 19, 2012, 12:35 AM
Just call me crash for short
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United States, OH, The Plains
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Got all the parts free from the material and deburred today. The fuse is just dry fit, no gluing as I kept getting distracted with phone calls from friends and family. Something about happy birthday and well wishing.... eh... Who has time for such stuff when there are wings to be built. Anyway, all ready to start gluing things up tomorrow.

The pdf file has a top view with a few dimensions, as Herk was kind of asking and it would be great to recieve his input, good, bad or ugly.

Mark
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Old Nov 19, 2012, 03:20 AM
I don't like your altitude
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Joined Sep 2011
3,382 Posts
Happy birthday!Have one of those talking torpedoes on me.
Re the plan and cut parts,have I seen that S shaped fin design in one of Peter Wick's articles?
Also the elevators.I was going to ask at some point about their positioning.I'd noticed on the Windlord that they were inboard.Do they have enough authority in that position or am I missing something.
Regards Stuart
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Old Nov 19, 2012, 03:41 AM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
Joined Jan 2011
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Quote:
Originally Posted by Stupot46 View Post
Happy birthday!Have one of those talking torpedoes on me.
Re the plan and cut parts,have I seen that S shaped fin design in one of Peter Wick's articles?
Also the elevators.I was going to ask at some point about their positioning.I'd noticed on the Windlord that they were inboard.Do they have enough authority in that position or am I missing something.
Regards Stuart
Thanks and done did!

The only time I have seen elevators on the outboard was when they were mixed in with the ailerons because that was where the ailerons need to be. Other than that, they are almost always inboard. In this case, inboard is also the further most point on the wing so i would suspect that they will have the most authority there. Take a look at the AV-36 - elevators are inboard / center / furthest point back. Worked for them.

Mark
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Old Nov 19, 2012, 01:20 PM
Herk
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Virginia USA
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Hi Mark, I've tried to rationalize your wing with straight lines and multiple panels. It looks pretty reasonable. Anyway - based on what I've been able to do, it does look as if you can get some elevator effect from the pitcheron panels.

Have you decided where you are going to locate the starting CG???

Do you happen to have the pitching moment data for that airfoil? If you don't have published data, but you have run it on XFLR5, then it would be the point on the CM curve where CL = 0.
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