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Old Jan 28, 2009, 09:40 PM
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Spekd'out's Avatar
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XCBD 157" CrossCountry Design by Drela

I am very interested in this design by Mark Drela which was introduced in the XC on the cheap thread. It seemed obvious that it needed its own thread so here it is. Take note that its intended to be REF (rudder, elevator,flap).I don't suppose anyone is that quick of a builder to have built one yet No specs on AUW which is an interesting topic. It has 1330" sq. area or 9.236' sq. which means at max FAI mass of 5 kg (176.37oz or 11 lbs) loading would be 19 oz/ft. Not sure of the lowest practicle flying weight but at 10 oz/ft it would weigh 92oz or 5lbs-12oz (2.608kg).
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Old Jan 29, 2009, 11:13 AM
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I was going to comment but I see this is the composite XC Bubble Dancer and am not familiar with it. Good Luck. Sounds like a Cross Country Monster!
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Last edited by ozmo01; Jan 29, 2009 at 12:47 PM. Reason: add XC
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Old Jan 29, 2009, 11:48 AM
Stealth Plane Works
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USA, MA, Stow
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I was about to start a build thread

I was literally minutes away from starting a build thread. I will be building a wing and set of tail feathers for John Elliott using stressed carbon skins and Hi Load 60 foam.

Since you started a thread I plan to just use this one.

Just to recap for those who didn't see the posts on the other thread, the XCBD is a REF Cross Country plane designed by Mark Drela.

Even though it looks like a scaled-up Bubble Dancer, it is a very different ship. The airfoils are similar in performance (lift and drag) to the AG4x airfoils used in the Supra, and this ship will be able to carry weight and move. The high aspect ratio wing will also put it in a very different performance class from the BD.

Both the REF design and the airfoils will make it easy to fly and very forgiving, again characteristics you will want in an XC plane. It will have a light wing loading, but be able to carry ballast for windy days.

If the prototype XCBD works as well as it promises, I will be selling wings and tail feathers for them. A fuse may be in the works at a later date.

Anker
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Old Jan 29, 2009, 11:51 AM
Stealth Plane Works
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Quote:
Originally Posted by ozmo01
I was going to comment but I see this is the composite Bubble Dancer and am not familiar with it. Good Luck.
You are mistaken, it is NOT a Bubble Dancer. The Bubble Dancer has different design parameters, uses different airfoils, has a different planform, and was designed for a different purpose. What they have in common is that they are REx ships designed by Mark Drela, that's it!

I am being pretty forceful because I can see that the looks and the name are going to invite assumptions like yours'.

Actually, I may start a new thread. The title "XC Bubble Dancer" is misleading. If the original author of the thread can rename it, please rename it to XCBD.

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Old Jan 29, 2009, 01:33 PM
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Anker,

The plans say XC Bubble Dancer, what else would you call it?

Not trying to start anything, but if you use the Bubble Dancer initials you will get people calling it a Bubble Dancer.

Jay
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Old Jan 29, 2009, 02:33 PM
Stealth Plane Works
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Quote:
Originally Posted by soholingo
Anker,

The plans say XC Bubble Dancer, what else would you call it?

Not trying to start anything, but if you use the Bubble Dancer initials you will get people calling it a Bubble Dancer.

Jay
We should have edited the plans. Mark and I agreed that it should be called the XCBD, just the initials.



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Old Jan 29, 2009, 04:38 PM
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Thanks Anker, I'm sure we will be fine from here on in. I was going to ask what kind of foam you used. Care to leak out how much is the foam core set goes for? I have been cutting templates on the CNC at work lately so I may cut them myself , but good to consider all the options. I was not able to use the AG23 file posted, how thick is the section?

I may be thrifty on this build and use Dow blue or pink foam. Not sure if better foam is readily available in my area. I wish I had more 3-D programming experience, it would be neat to machine a fuselage plug for it on the CNC. I do have a more competent machinist friend that I may have to pay a visit. I may be able to get some "scrap" kevlar from a kayak manufacturer close by, for the fuse lay-up. I may also try salvaging spar caps from composite hockey sticks for the wings.

Jan B
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Old Jan 29, 2009, 05:04 PM
Stealth Plane Works
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Jan,

Thanks for changing the title.

I use Hi Load 60 exclusively. For stressed skin construction the compression strength of the foam is paramount.

The problem with the AG23 posted is that it uses exponential notation, I believe. I changed it to use regular decimal notation.

I'll put it in the Files section in a moment. Woops, this isn't Yahoo groups, so I attached it as a .txt file.

I'll charge $100 for a set of cores, plus shipping. I can cut the cores for the "tube spar", cut a spar slot for a capped spar, or leave it with no cutouts, your choice. These cores are close to perfect, thanks to my CNC setup and a lot of tweaking and programming.

If someone wants cores I'll be happy to take orders now.

Anker

Quote:
Originally Posted by Spekd'out
Thanks Anker, I'm sure we will be fine from here on in. I was going to ask what kind of foam you used. Care to leak out how much is the foam core set goes for? I have been cutting templates on the CNC at work lately so I may cut them myself , but good to consider all the options. I was not able to use the AG23 file posted, how thick is the section?

I may be thrifty on this build and use Dow blue or pink foam. Not sure if better foam is readily available in my area. I wish I had more 3-D programming experience, it would be neat to machine a fuselage plug for it on the CNC. I do have a more competent machinist friend that I may have to pay a visit. I may be able to get some "scrap" kevlar from a kayak manufacturer close by, for the fuse lay-up. I may also try salvaging spar caps from composite hockey sticks for the wings.

Jan B
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Old Jan 29, 2009, 05:58 PM
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USA, CA, San Luis Obispo
Joined Jul 2005
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Quote:
Originally Posted by Anker
If the prototype XCBD works as well as it promises, I will be selling wings and tail feathers for them. A fuse may be in the works at a later date.

Anker
If/when you decide to sell bagged wings and tail feathers I would certainly be interested in set. I don't have the ability or desire to do bagging and this would be a perfect addition to my AVA and Supra!

Thanks,
Brian
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Old Jan 29, 2009, 06:31 PM
Axle209
Sacramento
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This design looks promising for a building project down the road.
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Old Jan 29, 2009, 06:41 PM
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Tennessee
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Very interesting design for cross country. I see only one problem. Or rather don't see one problem. The stealth fuselage will do nothing for keeping the model in sight at 4000 feet.
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Old Jan 29, 2009, 07:05 PM
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Quote:
Originally Posted by Anker
Jan,

I'll charge $100 for a set of cores, plus shipping. I can cut the cores for the "tube spar", cut a spar slot for a capped spar, or leave it with no cutouts, your choice. These cores are close to perfect, thanks to my CNC setup and a lot of tweaking and programming.

Anker
Does that include the tail feathers as well, and I guess they're Hi-Load 60 as well.?

I was finally able to get the root foil loaded into Compufoil. There was still one expo notatation in your file.
I get 8.9% thickness with 2.19% camber
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Old Jan 29, 2009, 07:45 PM
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Quote:
Originally Posted by ChuckA
Very interesting design for cross country. I see only one problem. Or rather don't see one problem. The stealth fuselage will do nothing for keeping the model in sight at 4000 feet.
That doesn't matter, the wing will have disappeared at 2800 feet.
There was discussion of the chord size on the other thread. I will be using mine for sport flying so in my case I am not too concerned.
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Old Jan 29, 2009, 08:05 PM
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United States, AL, Madison
Joined May 2002
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Quote:
Originally Posted by ChuckA
Very interesting design for cross country. I see only one problem. Or rather don't see one problem. The stealth fuselage will do nothing for keeping the model in sight at 4000 feet.
Chuck, the only thing you can see at any real height is the wing. Even the stabs are gone... if you're daring enough.
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Old Jan 30, 2009, 12:04 AM
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USA, CA, Selma
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How about as an electric with Bubble Dancer type wing structure?

John
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