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Old Apr 06, 2008, 10:56 PM
RC Connectors dot com
glenn2626's Avatar
United States, CO, Colorado Springs
Joined Jan 2008
1,170 Posts
Woot! The Redskinsmobile flies!

Hi all - FINALLY got a decent flight on the Redskinsmobile.

Wore out two lipos without breaking anything. (note I didn't say 'crashing'). It was too cold and getting dark so I called it a night.

I finally got over my fears and got her up to 50ft or so before doing much of anything. That has been my problem all along. The only times I crashed today was when coming in for a landing or was too low to recover from a mistake.

Note to other newbies - GET IT UP THERE. Other people have said it hundreds of times before, just DO IT.

Thanks to all of you for suggestions & encouragement. And especially Tony for such an easy-building cheap easy-flyer. I was showing her to a neighbor tonight and he was lamenting how his son built a nice 8-foot wingspan model with carbon fiber & other doodads but has stopped flying it because it's too pretty (& expensive) to crash. Needless to say I pointed out my $2 airframe & wings.

Now for a question: She flies great (once trimmed) at 1/3 to 2/3 throttle. Above that and she really noses way up and heads for the sky. At full throttle I nearly had to do full down elevator to keep it from climbing too fast (and stalling).

Is this normal? And if not, suggestions for fixing it?

Thanks!
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Old Apr 06, 2008, 11:02 PM
Registered User
Ipoh, Perak Malaysia
Joined Jul 2006
3,973 Posts
Are you using the UC wing saddle for a KFm wing? If so, you need to shim the back portion of the wing saddle by about 6mm to reduce the incidence angle of the wing.

If that is not the problem, you will have to put in more down thrust.

chewy

PS the above two problems are NOT mutually exclusive.
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Old Apr 07, 2008, 06:48 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by warhead_71
I WILL build another, bigger, stronger, and with KF3 wings... going for duration and camera platform next time
Ha! I knew it. You're hooked! You'll love the BBAP1. She's a big strong gentle girl with the heart of a Soviet weightlifter. I'm currently redesigning the plans to make them simpler, clearer etc. As well, there will only be a KFm3 option for the BBAP1. The UC airfoil doesn't even compare with the KFm3 for this application.

It will be posted in the next day or two. I'll note the changes here.

Tony
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Old Apr 07, 2008, 07:11 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by glenn2626
Hi all - FINALLY got a decent flight on the Redskinsmobile.

Wore out two lipos without breaking anything. (note I didn't say 'crashing'). It was too cold and getting dark so I called it a night.

I finally got over my fears and got her up to 50ft or so before doing much of anything. That has been my problem all along. The only times I crashed today was when coming in for a landing or was too low to recover from a mistake.

Note to other newbies - GET IT UP THERE. Other people have said it hundreds of times before, just DO IT.

Thanks to all of you for suggestions & encouragement. And especially Tony for such an easy-building cheap easy-flyer. I was showing her to a neighbor tonight and he was lamenting how his son built a nice 8-foot wingspan model with carbon fiber & other doodads but has stopped flying it because it's too pretty (& expensive) to crash. Needless to say I pointed out my $2 airframe & wings.

Now for a question: She flies great (once trimmed) at 1/3 to 2/3 throttle. Above that and she really noses way up and heads for the sky. At full throttle I nearly had to do full down elevator to keep it from climbing too fast (and stalling).

Is this normal? And if not, suggestions for fixing it?

Thanks!
Glenn, it's as normal as rain. Airplanes are supposed to do that (to a point). Let me explain: For an aircraft to be stable the center of gravity must be ahead of the center ot pressure (AKA center of lift). This state, if untrimmed, causes the nose to drop so we give the elevator a little up trim. This creates a state of equilibrium, like balancing a teeter-totter.

Gravity is pulling the nose down and for our purposes, we can say that is a constant, regardless of speed. But the tail is holding the nose up based on the air being deflected by the elevator.

More speed = more air over the elevator = more nose up force being applied.

Hence, add throttle and the nose goes up. It happens to all aircraft, of all sizes. When we trim, we are trimming for a certain speed. Add power, nose goes up, re-trim. The same for virtually all aircraft.

It is perfectly normal for the nose to go up, what we don't want is "ballooning". That is when the nose goes up so much the aircraft runs out of airspeed and stalls. Fortunately the fix is easy.

It can be caused by two factors basically. Too much wing incidence or too little downthrust. If you have a KFm wing on a BB with the saddle cut for the 4-40 airfoil, you have too much incidence as Chewy noted. Simply lower the front of the wing saddle by 1/4" (or raise the rear by the same amount) and your problem vanishes.

If that isn't the case, it is your motor's downthrust. The BB's thrust angle should be -4 degrees, or the same angle as the forward upper portion of the fuselage. Easy.

If those things are already right, simply trim for a faster speed. You may have your BB trimmed for it's best glide, which is not the same as it's best cruise speed.

Try this stuff out, remember the teeter-totter, and it's a breeze. Let us know how it works out.

Tony

PS: Your message to newbies is important. Get the plane away from the ground. Fly your new plane two mistakes high. There is nothing to hit up there.
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Old Apr 07, 2008, 11:00 AM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
3,919 Posts
Quote:
Originally Posted by Tony65x55
Get the plane away from the ground. Fly your new plane two mistakes high...
I agree. I like to have at least 500-800ft of altitude for each of those 2 mistakes.

kendall
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Old Apr 07, 2008, 04:00 PM
treefinder
springer's Avatar
SE MI
Joined Oct 2004
9,428 Posts
Man, off line for 20 hrs and three pages to read!
Nub: from 3 pages ago, the control arm on servo sits just off center when tx is center trimmed, flipping it makes it same amount off the other way, so i just trimmed it to center. Need to ck the full travel if I flip it though. I've heard about "zeroing servos" but don't know how to do that with the 9 gram hextronic ones - any help?

Also, I can't believe you actually buy control horns! All this time I thought you were as cheap as i am! If you stay in one place long enough, you will get tons of those cute little blue/clear fake amex cards that make great horns!

Way too windy to fly today (wife wouldn't even work in her flower gardens and that's a spring compulsion!) Plus gotta get taxes finished, so will wait til tomorrow to try out all you guys' suggestions!

Tony: great discussion on power/climb. But a question: What happens if you have too much down thrust? and (I still get screwed up on the definition - down thrust for tractor is fwd end of motor shaft down, right?) I just looked at my bb w/ailerons and motor shaft looks to have more angle down at front than the front of firewall - more parallel to the top surface of fuse nose. Will that cause the plane to fly nose up? Doesn't seem to be a problem at low to mid speeds, and I attributed the nose up/pop up at high throttle to the Uc wing and KFM incidence. hmmmm???
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Old Apr 07, 2008, 07:15 PM
Tinkerer
jfhspike's Avatar
RI
Joined May 2005
184 Posts
Quote:
Originally Posted by SpinningInPres
I used zip ties for control horns...works really well...

PS
When you say "control horns" do you mean "the control arm on the servo" or "the thing on the aileron/rudder/elevator surface that the other end of the wire/pushrod attaches to?" I see in your picture of your camera-bay that it looks like you're using ordinary control-horns on the surfaces; perhaps that's a zip-tie attached to your servo?

-John
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Old Apr 07, 2008, 07:16 PM
Registered User
Prescott, AZ
Joined Jan 2008
356 Posts
Pics of my 42" Blu-Baby Semi Sport Ready for Maiden

Hi All:

Here's some pics of my newly completed BB 42" with Semi Sport Wing (I took the Sport Wing and added a little dihedral). I'm going to maiden it tomorrow am early before the winds pick up to the standard 15 - 25 that we've had.

She's all ready to go, balanced perfectly with the 4 AAAs providing receiver power (I fried my BEC).

She's weighs 29 oz w/o battery, 35.5 oz AUW and is pulled by a 2217/9 motor on a 10 x 6.

I built this as my training platform for 4 channel flight. The wing is bulletproof with CF arrow shafts as spars running all the way to the end of the wing. I used the threaded shaft to attach the winglets which I added as crashing/training wheels.

Thanks to everyone (esp. Tony) for their pics and notes that allowed me to build this fine bird!

PS
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Last edited by SpinningInPres; Apr 08, 2008 at 03:19 PM.
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Old Apr 07, 2008, 08:36 PM
did a reversed Immelman..once.
SKYPILEIT's Avatar
Novi, Michigan
Joined Nov 2002
2,247 Posts
New Blue baby..

Looks good PS...please let us know how the maiden flight went...I may want to build an aileron BB to go with my R/E 32 inch baby.
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Old Apr 07, 2008, 09:58 PM
In Rc for a LONG TIME FFAA#1
laserman's Avatar
Canada, ON, Ottawa
Joined Jun 2004
1,375 Posts
well almost done had a good time at the LHS, saw and was really temped by the parkzone ember but was able to hold off on that!! but was able to get all the goodies i wanted and then i went to snappy tire looking for a stand to have my dremel scroll saw so i can do some work, and well they said they did not have any thing my FB was with me and saw a folding work table on sale for 13$ and i grabbed it and as well in the propane torch area they were clearing out micro butane torch for 3$ with tank of butane grabbed that as well and the wife said when i came back looks like you got a few deals!! at the lhs was able to get my control horns and a few spare props and a few other goodies as well, the one thing was some nice black props so i grabbed them they ranged from 10 4,7 to 865 and one quad prop for electric so i am happy there as well
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Old Apr 07, 2008, 10:00 PM
If it flies, its cool
bondohead's Avatar
Atlanta
Joined Apr 2007
1,114 Posts
let me get it strate. building a 33" for a low timer. actuly this will be his first real plane. i want it to be as lite and floaty as possable. in the plans in post 1 just dont use the ffm strip? one peace wing? how do i make it form to the bend in the feuse to form an airfoil?
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Old Apr 07, 2008, 10:05 PM
Registered User
Joined Sep 2004
2,744 Posts
Bend FF

Quote:
Originally Posted by bondohead
let me get it strate. building a 33" for a low timer. actuly this will be his first real plane. i want it to be as lite and floaty as possable. in the plans in post 1 just dont use the ffm strip? one peace wing? how do i make it form to the bend in the feuse to form an airfoil?
Two three four ways;

Two popular is over a rounded Kitchen counter top, some use a round 3 inch pvc pipe........... I'll try to find the detailed instr for you.

[edit; see posts 3261 and 3262; 26 sec video how to bend on counter top edge; end of edit]

LarryR : )
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Last edited by LareeRudee; Apr 07, 2008 at 10:12 PM. Reason: Video to bend
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Old Apr 07, 2008, 10:08 PM
If it flies, its cool
bondohead's Avatar
Atlanta
Joined Apr 2007
1,114 Posts
i built an stc over table but i dont see any relif cuts un this one
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Old Apr 07, 2008, 10:14 PM
Registered User
Joined Sep 2004
2,744 Posts
Scores/relief

Quote:
Originally Posted by bondohead
i built an stc over table but i dont see any relif cuts un this one
I always scored them; I think it was Tony said there is no need to score them.

LarryR : )
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Old Apr 07, 2008, 10:27 PM
Registered User
hqmq's Avatar
Joined Sep 2007
115 Posts
Motor Update

Thanks again everyone for your motor suggestions (especially chewy). I tried to think up a solution for getting a small gear to fit on my 3mm prop from the 3800kV brushless that would still fit in a normal gearbox. As I was thinking of different solutions it dawned on me that buried in a box somewhere I still had several motors and props for a GWS EPS-C geared brushed system. So I dug through and found it, bought a new mount ($1.25 for LHS) and a new shaft ($1.25 as well) and mounted the new set up with a 9070 slowfly prop on my 33" BB. WHAT A DIFFERENCE!!!

The brushed system is heavier than my brushless but it provides a lot more power and is more efficient (longer flight times) than my overloaded brushless. My final conclusion is that when my FC28-22's get here from hobbycity I will use them to finish my 42" BB and leave the brushed system and 10C batteries on the 33" for fun flying and for teaching my wife. (she says that she is my copilot and it's about time she got her own plane )

In anycase the little BB is flying beautifully. Having some extra power really helps out when I add a little too much elevator in a turn or start to get a pendulum effect in the wind. It makes for much easier takeoffs too (I used to have a max of about 10 degree climb which made for some scary hand launches! Now she will climb 30-40 degrees and not even WOT). Thanks again for all your help with my motor decisions.


SpinningInPres: Your 42" BB looks beautiful. Mine will be my first aileron trainer too (after I get the hang of her with just rudder/elevator). Hope mine is as good looking as yours when it is done!
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