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Old Sep 06, 2010, 01:29 PM
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Ontario, Canada
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Quote:
Originally Posted by Griffindor View Post
What foam are you working with? Will the paint eat my foam, and was the paint heavy or what?

Thanks.
Water based acrylic craft paint will not harm any type of foam. As for weight, depends on the foam, how it's applied, how many coats, and the size of the plane, etc. On my smaller 24" WS planes, it added 0.5oz. For a BB42, it could be 1 oz or more.

The lightest paint jobs will be with an airbrush and applied in thin coats. Brushed on will be the heaviest, especially if you've peeled any of the film... the foam soaks up the paint like a sponge!
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Old Sep 06, 2010, 03:37 PM
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Quote:
Originally Posted by Griffindor View Post
What foam are you working with? Will the paint eat my foam, and was the paint heavy or what?

Thanks.
These BB 33" (I add a little and make them 34.5" WS), I am using standard Blue Core Fan Fold construction foam. Depron would be lighter. However I leave the plastic on and this makes a very strong plane. I only remove plastic at glue joints.

I used craft paint.

All the foams you can use Craft paint, in the little bottles available at all the craft stores. It is water based and does not attack foam. Others are Testors, Tamya sparys or bottles (acrylics), Krylon H2O, Krylon Creative, artist acrylics, and maybe some more.

If the can of paint says it contains acetone, Toulene, or petrolium distilled products, DO NOT USE!

Sharpie markers work well too, along with all the colored packing tapes.

A BB 33" should gain 1/3 to 1 ounce with paint, and top coating. Brushed or sprayed. Yes brushes can lay it down thicker, but thinning the paint with a little water helps a lot. Even stripped foam (rough surface) won't drink so much paint if it is diluted! jjust remember do not try to cover in one coat, it will always show ghosts anyway, 2 thin coats is usually enough! No need to prime either!

Worried about adding an ounce (28 grams) to a 33" or 44" BB is not even a concern. So much wing area to begin with. I can land my painted undercambered BB's at around 2 to 3 MPH all day long, even slower, or vertical decent if there is some wind!

Fred
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Old Sep 06, 2010, 06:24 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
North AL, USA
Joined Nov 2009
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Built a 12" BB For Indoor - Questions

The BB I built has the 4-40 UC wing. It has good glide characteristics, but when I power up the motors from an Air Hogs (two motors, thrust differential, mounted in a "push" configuration) it just dives under power. I tried to adjust the angle of the motor but that didn't seem to help much. I'm pretty sure I have CG right too (about 1/3 back on the wing) glides OK as mentioned). I think I have the horiz stab angle correct, I followed the plans -- maybe that needs to have a little up added.

If I built a kfm2/3 wing, do you think putting these motors either in a push or pull configuration might work? I'm willing to give it a shot, but since I don't have working control surfaces, what kind of wing incidence would I need? Would there need to be any special angle for the motors? I'm kinda out there with this one, but really want to get this working so I can fly indoors. I think a pull configuration (motors facing forward) would be best, as getting CG a little further forward would be better.

Any suggestions are appreciated. I'll try anything, as it only takes a few minutes to whip something out on a bird this size...

Thanks!
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Old Sep 06, 2010, 08:05 PM
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Attica, MI
Joined Dec 2006
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R1,

I built one of these awhile back out of 3mm EPP. Had a similar experience, so I ended up moving the motors off the wing to a lower position on the fuselage to get the thrust line more in line with the center of drag. I used a CF flat to support the motors away from the fuselage.

My advice is to stay with the UC wing for this small size. You need the slower flight envelope that it will provide for the Aero Ace gear.

Ken
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Old Sep 06, 2010, 08:30 PM
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What is the average weight of a blu baby??Mine weighs 9 oz
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Old Sep 06, 2010, 09:01 PM
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Quote:
Originally Posted by planeflyer94 View Post
What is the average weight of a blu baby??Mine weighs 9 oz
Depends. Most of BB33's I've built with the stock UC wing came in under 7oz.

BB33 with a KFM3 wing and ailerons was nearly 11oz.

BB42 came close to 16oz.

BB24 was about 5oz.

Motor & battery size make a huge difference here. Also how neat you build counts!
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Old Sep 06, 2010, 09:07 PM
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Quote:
Originally Posted by ruff1 View Post
The BB I built has the 4-40 UC wing. It has good glide characteristics, but when I power up the motors from an Air Hogs (two motors, thrust differential, mounted in a "push" configuration) it just dives under power.
FYI:

Everything you ever wanted to know about the AA planes and power systems can be found in the AA Toolbox:

http://aatoolbox.no-ip.org/

There isn't much mention about thrust angles.

I am with dz1sfb, the thrust line may be the culprit. If you look at the AA Bipe or the AA Jet, it had a pretty extreme thrust angle... it pointed backwards and down at 15+ deg.

Now, I did mod a Silverlit 'U-Build-It' single prop plane with rudder. Replaced the wing, and H. stab with larger BB sized versions. It worked fairly well.
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Old Sep 06, 2010, 09:12 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
North AL, USA
Joined Nov 2009
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Quote:
Originally Posted by dz1sfb View Post
... I ended up moving the motors off the wing to a lower position on the fuselage to get the thrust line more in line with the center of drag.
Thrust line, that's it. I think I'll run a popsicle stick through the fuse along the thrust line, moving the motors forward too to get better CG.
Excellent advice, I'll give that a shot! Thanks!
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Old Sep 07, 2010, 12:51 AM
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Quote:
Originally Posted by ruff1 View Post
Thrust line, that's it. I think I'll run a popsicle stick through the fuse along the thrust line, moving the motors forward too to get better CG.
Excellent advice, I'll give that a shot! Thanks!
2 cents worth. Most airhogs have some up trim in the horizontal stab/elevator so when the thrust is applied it causes the plane to climb, but not so much that the glide is affected adversely.

Fred
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Old Sep 07, 2010, 01:42 AM
BEC
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Quote:
Originally Posted by Freddie B View Post
I can land my painted undercambered BB's at around 2 to 3 MPH all day long, even slower, or vertical decent if there is some wind!

Fred
I presume you're exaggerating to be dramatic. To have a 3 mph stall speed a plane would need a wing loading on the order of 1 ounce per square foot....which would mean a BB33 that weighed around two ounces. Not impossible, but unlikely.....
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Old Sep 07, 2010, 03:22 AM
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Hello All,

Wonderful to see the success of this plan! Unfortunately, this thread is SO long that it's virtually un-navigable! I'm going to be (or rather, my students will be) building this plane for their first plane in our Flight Club (an After School club). Sorry to bother you with these questions, as I'm sure they're answered somewhere in the 1000 pages of the thread (!!), but I just can't read it all.

1.) Most of my students have little to no experience w/ RC. Some do, however, and I'm expecting them to catch on quickly. I'd really like to have this be a 4 channel plane--so that they have experience learning with ailerons. I'm hoping that even if there are ailerons on the plane, it still could be flown using only elevator/rudder control. Is this true, or am I asking too much? In other words, does the presence of ailerons require the pilot use them? (I was hoping to just unplug the aileron servo or turn it's travel down to 1% to 'disable' it for total newbies)

2.) Are there plans for an aileron wing? How about a KF/aileron combo? I love the idea of building one of these neato KF airfoils, and as mentioned, I'd like them to get experience with ailerons.

3.) How do you build a wing with dihedral? I've done a lot of reading but haven't found a real solid explanation. It sounds like you build two wing halves, cut the inside edge (the ones that will face together) at the desired angle, then use a bent piece of metal tube to hold the spars at that angle. Is that about right?

4.) I don't suppose there are any basic step-by-step instructions for building the BB? I'm hoping to give my students some pointers while building, but hopefully not having to hold their hand the whole way.

Thanks so much for your help. About 20 Thai kids are really going to appreciate your efforts. As will I (this will be my first scratch build!)
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Old Sep 07, 2010, 06:30 AM
Slipping the Surly Bonds
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Attica, MI
Joined Dec 2006
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Doughpat,
I may risk the ire of some folks here, but the BB is a purpose designed 3 channel RET plane. It excels at that. This in my opinion is not a good airplane for ailerons. One exception would be the 42" size with the KFm3 wing, and that is with alot of aileron differential to counteract adverse which shows up in this design when equipped with ailerons.

The problem is the result of too much lateral fuselage area ahead of the center of gravity. This moves the center of pressure ahead of the CG so that when the aircraft is rolled the nose wants to head to the sky rather than falling through the turn. A little bit of this is normal and requires some coordinated rudder, but it is a very pronounced characteristic in the BB design.

It is a mistaken idea that if you fly with the rudder (on the right stick) you will not know what to do when you have ailerons. The sweet thing about RET especially a BB RET is that you have normal rudder function for take off, but effective roll control at flying speed. All we are doing with the rudder and dihedral on the wing is creating lift differential which then rolls the aircraft when we yaw. Ailerons are of course more direct roll control without yawing, except in the BB extreme adverse yaw is created, which then is more not like flying a real plane than using the rudder on this design.

Not dis-ing the Blue Baby, it is one of my favorite planes. Just not with ailerons. Which leads me to another thought that there really is a hunger out there for a good 4 channel foamie design that has all the good characteristics of the BB. That is a challenge I should take on.

I do believe that the situation could all change if you simply flattened out the top of the fuselage on this design and stretched the tail a bit for more moment. Effectively making it into a shoulder wing model with less lateral fuselage area in front of, and more behind the CG. That would be a winner for sure. In fact I now know what my next design will be.

Ken
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Old Sep 07, 2010, 09:17 AM
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Quote:
Originally Posted by BEC View Post
I presume you're exaggerating to be dramatic. To have a 3 mph stall speed a plane would need a wing loading on the order of 1 ounce per square foot....which would mean a BB33 that weighed around two ounces. Not impossible, but unlikely.....
We are talking ground speed here, not airspeed! Exaggerating, not at all, in fact I'm known for being too honest. Think GWS Slow Stick. With throttle management, slight head wind, lots of elevator pulsing, and keeping rudder moving to control wing rock, you can all but harrier this plane to the ground (undercambered that is). Maybe we can get some video.

Nice 7-10 MPH winds you can also land going backwards, using high alpha spurts. I can kite mine up high in the wind, and get no ground speed. Airspeed does not equal ground speed, turn her around into the tailwind and you have to land at 10+ mph!

Just having fun!

Fred
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Old Sep 07, 2010, 09:36 AM
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doughpat

Great plane for teaching building and early flying experiance. Good to see you are teaching and aerodynamics is a plus for those kids.

I just built the KFm3 wing, ailerons, and I agree the BB flys so bad with a standard aileron setup, I may junk the aileron wing. Adverse yaw is the worst I've ever experianced. Differential, and lots of it will be required, but not so sure that it would help enough to cure the bad traits. dz1sfb is spot on with his explinations.

I also agree that if you build a 4 channel plane, planning on disabling the ailerons to fly only Rudder/Elevator for newbys, they will get used to the controls in a wrong fashon. If you learn to yaw and turn the plane with other than the aileron stick, they will get confused when transitioning to 4 channel. You should set the rudder channel to the aileron channel when using Rud/Elev only. Aileron planes fly like R/E planes, only more precise. The BB flys so well R/E that you would think it had ailerons.

You are right about dihedral, two wing halves. The joining is with glue, and the edges sanded to the proper angle. The metal tube idea works with round spars, but there are so many other methods, and simple hardwood or bass joiners cut to the angle work with wood pars, or no spars at all. The BB 33" works well with the recommended fiber reinforced strapping tape as the "spars". Whatever you do will probably work.

There are so many pages on this 'million view' thread, but some pointers I photographed are only a few pages back (Page 599), maybe that would be a start? Here is a quick link to that page, and starts on post #14954. Just Click on this link: http://www.rcgroups.com/forums/showt...pp=25&page=599

I designed a trainer system a few years back, foam 36 & 42" WS planes that look like an ugly stick. R/E/T had a 42" WS, 6:1 aspect ratio. The A/R/E/T had a 5:1 aspect ratio, with the same wing area (wider cord). They share the same basic fuselage, and both fly great. Simple build too.

Good luck, and chime in with any/all questions!

Fred
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Old Sep 07, 2010, 11:14 AM
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Ken,

Thanks so much for the well-worded and specific reply. Very interesting stuff. I'm surprised that these planes are so responsive to subtle things like the shape of the fuselage. Neato.

Fred,

Got it! I'll connect the rudder servo to the ailerons, and i'm sure the kids will figure it out once we transition into ARET planes. I'm most concerned about them learning to recognize that controls are 'reversed' when the plane is coming towards them (or inverted). And the usual stuff (stalls, learning to land on target, basic maneuvers, etc.)

Sounds like an awesome plane. Any opinion on the KF foil vs. regular undercambered?

Thanks again.
Ryan Lenz
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