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Old Sep 12, 2007, 06:00 AM
Flying 3 mistakes high
GlennS's Avatar
Melbourne, Australia
Joined Jun 2004
1,522 Posts
Quote:
Originally Posted by Truglodite
please post pics if you can. a hotwired clark-y on a big bb should be a treat.

kev
Hi Kev, not much progress so far... will take some photos during the build.

Tony, when you used a clark Y for the BBAP1, did you make the wing in three pieces or two?

Glenn.
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Old Sep 12, 2007, 07:24 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Hi Glenn, There are two answers depending on the question. If the question is "did I use two wings and a center section", the answer is no. Just two wings joined together at the center. I think this is what you're asking.

In fact, the wings were several pieces as they were made of fan fold. Bottom, top, full length foam spar (for shape), CF tube (for load), flaperons, wingtips. As easy to build as a KFm wing, easier than the KFm2.

Performance was good, typical Clark Y. The flaperons helped tailor the flight characteristics enormously. A few degrees down for extra lift, a few degrees up for extra speed, 20 degrees down to slow down for landing. Mixed with elevator in "flap" function and mixed with rudder in "aileron" function. Made deploying flaps effortless and gave you less to think about while nursing down that camera.

Make the flaperon slightly smaller (chordwise) at the tip than the root and tip stalls are no concern. Stall will move progressively from root to tip. As the flaperon is deployed, the smaller chord at the tip hangs down less distance, giving the wing good washout. It sounds strange but works really well.

Tony
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Old Sep 12, 2007, 08:29 AM
Flying 3 mistakes high
GlennS's Avatar
Melbourne, Australia
Joined Jun 2004
1,522 Posts
Thanks Tony, yes, the question wasnt very clear, I did mean was the wing made from two wings and a centre section. I was thinking of just the two wing sections joined at the centre with a slight dihedral, say 3 degrees for ailerons/flaperons. I think the dihedral is slightly more for the BBAP2. OK on the tip for taper on flaperons.
Glenn.
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Old Sep 12, 2007, 11:33 AM
Went to mow a meadow
frank48's Avatar
Joined Feb 2007
1,456 Posts
Bb Ap2

Hi Tony

It would be great if you can give me some pointers on how you make the wing joiner on BB AP2. Like you I need to make it in two pieces for tranportation and join at the field. Many thanks for a great plan & plane

Frank
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Old Sep 12, 2007, 12:42 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,532 Posts
very nice work glenn!

here comes the thread jack: i'd love to rig up a hotwire to cut my own wings too. it looks like you're pretty good with your hotwire. would you mind posting link(s) to info you used to build/operate your rig, or the place where you bought it? i've been trying to find the time the past 3 weeks to research diy hotwires, and there's just too many choices to remember. i mainly want to cut light epp & eps, possibly depron.

kev
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Old Sep 12, 2007, 07:14 PM
Flying 3 mistakes high
GlennS's Avatar
Melbourne, Australia
Joined Jun 2004
1,522 Posts
Quote:
Originally Posted by Truglodite
very nice work glenn!

here comes the thread jack: i'd love to rig up a hotwire to cut my own wings too. it looks like you're pretty good with your hotwire. would you mind posting link(s) to info you used to build/operate your rig, or the place where you bought it? i've been trying to find the time the past 3 weeks to research diy hotwires, and there's just too many choices to remember. i mainly want to cut light epp & eps, possibly depron.

kev
thanks Kev, my cutting bow is pretty low tech!
For wire, I use steel fishing wire leader from Kmart. I find that 20Volts on a 750mm length is about right temperature from a variable power supply. Will post some photos on my blog when home tonight.
I print out the aerofoil profile from a program called "Profili" (free version from web) onto paper.
I then cut out the aerofoil templates from masonite and temporarily glue the templates either side of a block of EPS foam with a light spray of 3M77.
Next, the bow is simply drawn over the templates, top then bottom. It helps to stick a pin in the ends of the templates to help guide the start of the cut.
To keep the cut even through the foam, I mark off 1cm units on the block of foam on each side near the templates.
While I am drawing the bow through the foam, my wife calls out the numbers on her side and I check that they are the same on my side! Lots of complaints about smelly foam, but its a great help. <end of hijack>
Glenn.
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Old Sep 12, 2007, 11:13 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,532 Posts
thanks glenn! i wasn't sure if i needed special resistance wire, gravity feeds... if results that good are possible with stainless leader & masonite templates, then a similar low tech hotwire should fit the bill for me. i have a good idea what's needed to build one, but i'll wait until you put it on your blog before i proceed. no rush, i'm in no hurry.

thanks again,
kev
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Old Sep 13, 2007, 09:43 AM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
3,919 Posts
Help with BluEndurance Maiden

BluEndurance had her maiden this AM and left me puzzled. I'm sure it's a result of my attempt at the Big Wing, but pitch axis was all but uncontrollable. I had to fight her the whole time. Under any throttle she'd pitch up. If I trimmed it out she'd dive straight for the deck with power off. I read Tony's post on the other thread about climbing with throttle. What I'd like to know is if I can fix it.

kendall
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Old Sep 13, 2007, 10:35 AM
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Joined Nov 2006
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THe pitch angle of the motor. If you have down thrust with the motor the plane will maintain level flight even if you are throttling up. I had the exact same problem with Tony's SE5A because I didn't follow the build guide with the down thrust. Correcting that fixed the flght characteristics.
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Old Sep 13, 2007, 11:16 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by tuppertn
BluEndurance had her maiden this AM and left me puzzled. I'm sure it's a result of my attempt at the Big Wing, but pitch axis was all but uncontrollable. I had to fight her the whole time. Under any throttle she'd pitch up. If I trimmed it out she'd dive straight for the deck with power off. I read Tony's post on the other thread about climbing with throttle. What I'd like to know is if I can fix it.

kendall
Congrats on the maiden (I think). In this order. Check CG, check motor thrust angle, check incidence.

If you got it to glide, it will fly. Bad motor thrust angle will, as Kurpal attests, cause you grief, particularly if the thrust angle is up. This situation would be greatly aggravated by a rearward CG. An excessive incidence angle would aggravate it even more. By the time you get to that point the plane should be a bucking bronco and very hard to fly.

The thrust angle should be approximately - 3-4 degrees down, as measured from the stabilizer. Wing incidence should be about + 2 degrees, also as measured from the stabilizer.

Try that stuff Kendall, I'm sure it will help.

Tony
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Old Sep 13, 2007, 03:36 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,532 Posts
^---^..., and luckily you have a flat wing saddle & firewall motor mount. adjusting incidence is easily done with a razor & straight edge. thrust line adjustments are as simple as adding washers between the firewall & motor mount. it may be a good idea to use shims on the wing saddle to test various incidence angles before you commit by cutting the saddle.

another bit of designing insight: because your fuse length:wing span ratio is quite small, tail controls will be somewhat temperamental even after everything is tuned correctly. ie: it's like trying to accurately control the position of a slot machine lever with your hand only 6" from the pivot. control will be way more shaky compared to holding the handle 18" from the pivot point (3x leverage=1/3 force).

i wouldn't expect the bbendurance to fly easily (fly easily=large flight envelope) like a normal bb, it'll never happen. i wouldn't let that get you down though. it is what it is, and pretty much all record breaking planes are designed to extremes that makes them have very small flight envelopes. that's why you never see newbies breaking records. at least you know you can bring her down in one piece as is, and there is likely room to improve control. heck, even my run of the mill bbap1 60" doesn't allow for much slop. if i look away for 5 seconds & the wind hits it wrong, it could easily enter a fast dive. building & piloting precision is key; that's just part of the small endurance style flight envelope.

-kev
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Old Sep 13, 2007, 03:47 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
3,919 Posts
A better maiden report...

Sorry about the earlier post being rather hasty. The wife was pushing me out the door to take the baby to swimming lessons.

Conditions this morning were a touch windy--10-12mph, but unlimited ceiling. I made 5 flights for a total of about 13 minutes.

1. The pitch thing: The first ground roll was a slow throttle up deal because I wanted to double check the rudder trim/right thrust before she got airborne. Still she rotated almost immediately and was off the ground in about 12ft. For the other full throttle take-offs she was airborne in literally 2-3ft--gobs and gobs of lift. Initial few seconds of climbout was a very encouraging constant 50-60 degrees. I had to hold some down elevator to keep her there, but I figured I'd get 3 mistakes high and then trim her out. Then craziness started happening. A gust of wind made her pitch up and she wouldn't quit. I really thought a control rod was binding or something. I managed to get her up 200-300ft and throttled back and she seemed to level out at first, but she wanted to porpoise at 1/4-1/2 throttle. I tried trimming for level flight at 1/2 throttle, but couldn't find the balance. She was either porpoising or diving. I got fairly close to level flight, but when I cut the power she took a steep dive for 40-50 ft then caught herself, sorta. She came out of the dive, stuck her nose up and continued to porpoise with power off. With 60% elevator exponential it was still overly sensitive.

2. Turning: Turning was slow, but adequate. Obviously she wouldn't barrel roll like a BB32, but it appears she has adequate rudder authority for the task.

3. The Wing: Holy wing flex, Batman. She looks great on climbout, but on a couple of dive recoveries (big time loading) the wing tips were flexing near 45 degrees.

3. Performance: The KDA20-22L/GWS 10x4.7SF is a winner. Full throttle gave adequate power for those 60 degrees climbouts. Needless to say with her trim issues I didn't try any aerobatics, but there were times that she got completely vertical (not on purpose) at hung there momentarily at WOT. Thrust must be somewhere around 22-25oz. The datalogger (its maiden flight as well) showed my max draw at 12.5A in the air (13.4A @ 10.29V for the run-up proir to ground roll). Max power was 149W. I drained a total of 789mAh from the 3s/2250. The trim trials at 1/4 throttle were 2.4A, 1/2 throttle was 6.3A. Altimeter logged my max altitude at 308ft with most of my time spent around 200-220ft.

As to the other stuff: Motor angle is 4 degrees down/4 degrees right. Wing incidence is right on at 2 degrees. I set the CG at 4.875" back from the LE at the root. That's a hair over 38% on a 12.75" cord because I wanted it a touch forward for the maiden. I left, however, with the overall impression that it was too far back as evidenced by the porpoising glideslope.

More confusion : So I'm confused where to start. I feel like I want to move the CG forward, but I understood from Tony's "climbing with power" post (brilliant BTW) that trimming with the CG forward makes the power-climb thing worse. There must be a way to make her behave. She looks soooo good on the wing.

I've attached a few vids of her craziness and a couple of stills of the fuse/motor angles. Please excuse the unedited videography. Wife was on the camera and was having issues finding the plane on the little screen. Lost it in the sun a couple of times. There's a fair amount of redundency in these. Just FF through the high and faraway parts. I hope it's good enough for you to get an idea of what she was doing.
http://www.youtube.com/watch?v=UO6P9cKP68U
http://www.youtube.com/watch?v=9qe_HSNB9SQ
http://www.youtube.com/watch?v=1rZ8GOTmDYM
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Old Sep 13, 2007, 03:58 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,532 Posts
omg that's an amazing climb rate! must be more that 45deg. reminds me of a hotliner.

sorry, with my pc & those vids, i can't make out much detail when you're farther away. from what i see in the pics your incidence & thrust angle are just about where they should be.

the way you describe its behavior though, i'd guess it needs a more forward cg & more down thrust. just a wild guess, but if i was at the field & wanted to make some quick changes that's probably what i'd try first.

have you noticed any twisting in the wing during flight?
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Old Sep 13, 2007, 04:19 PM
Always Ready!
warhead_71's Avatar
Chicago, IL
Joined Dec 2006
5,179 Posts
With that much wing and no bracing, I'm sure you're getting a lot of wing flutter too.
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Old Sep 13, 2007, 04:28 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,532 Posts
argh, i should've read your whole post first. i think your priority should be wing bracing. if you're getting that much flex, you need struts. the other adjustments are kind of pointless if the wing is going to be all over the place. got bamboo skewers?

kev

[edit: hehe, or you could do what mr flash always does when things don't fly quite right; make it a biplane. ]
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