Bi-Slob Tail Spin ...

At Brodak's over the past two years I've seen several Bi-Slobs, including my own, go into a clockwise death spiral if the lines go slack. I'm sure that the huge motor offset is the culprit.

Are there any other C-L planes that have this problem?

LAST EDITED ON Oct-11-06 AT 06:13 AM (CST)
 
John,

The Bislob is happier with some wind at your back.

Yes, there is a reason for this to happen. I searched back to the days that I flew full size aerobatics, then the answer became obvious.

To perform a snap roll, pull back rapidly on the stick, and apply hard rudder, and you are now doing a very fast horizontal spin.. or snap roll.
Ailerons may be applied but are not necessary. Basically, you are in a stalled condition, with the rudder getting the rotation going.

Now, if you apply down rapidly, you have a crossed controled spin, that is similar to the entry to a lumchevoc. It will start to tumble. There are several ways to enter the lumchevoc, but one way is to have an inverted climb, down elevator and rudder and aileron opposite each other.

Now look at the BiSlob.. Lots of right thrust and right rudder, perform a very tight loop, and it just wants to do the same horizontal spin or snap roll. With rapid elevator movement, it will roll right in on you. This is aggravated even more if you're at about 40° or more high, because you now have a low wing to start out with. With a good wind at your back, no problem. Light wind to calm, avoid that maneuver!

Of course, all that right thrust & rudder is what helps the Slob be a Slob!

At one of the Sig contests, Bob Arata's fine-flying Boxcar Chief lost its rudder. It immediately went into a flat spin down to the ground. Mot sure why it did that, but it was pretty spectacular.

I had a Flying Fool that had a tendency to do that. right at the top of the wing over if the wind gusted or if you missed the wind even slightly, it would go into a flat spin.

Bigiron

Andy Borgogna
Are any of these bad tendencies made worst because the plane is a biplane. I only ask this because I am scratch building a biplane of my own design and wonder if this is something I need to worry about.
Andy

LAST EDITED ON Oct-12-06 AT 02:07 PM (CST)
 
Just my thinking, I think the BiSlobs fly better and do better tricks if they are tail, heavy so when they do come uncoupled they tend to do funny things.I would love to be able to get the Slob swinging in and out and then give it full up run at it and let it do a vertical snap roll, step back and catch it on the end of lines before it crashed. Has any one done this yet.

LAST EDITED ON Oct-12-06 AT 12:25 PM (CST)
 
Joe,

You Slob!

I always new you were crazy!

Joe,
I bet you juggle chain saws too!

Just my thinking, I think the BiSlobs fly better and do better tricks if they are tail, heavy so when they do come uncoupled they tend to do funny things.I would love to be able to get the Slob swinging in and out and then give it full up run at it and let it do a vertical snap roll and catch it befor it crashed. Has any one done this yet.

The first biplane I built (an S-1 Ringmaster with the original wing blank glued back in and faired over, and two Jr. Satan wings, lower cut up 1" into bottom of fuse, upper one 5" higher, and 1-1/2" forward-stagger) I learned that, if in the middle of a wingover I gave it a crack of full down elevator, it would snaproll under, slacken the lines, and go gyroscopic! I was always able to recover, made many flights ("uncontrolled!") such as this, and repeated these on other bipes: Sig Profile Spad, (McCoy .19) Flying Fool, (Fox .35)
Sig Fokker D-7, (McCoy .35) and some other Ringmasters with scratch-built wings of varying chords.
My scratch-built profile Bipe (profile Sabre fuse, upside-down, scratched wings; this is where I confirmed the 1 degree negative incidence in top wing) was the testbed for the O.S. .40 fourstroke.
Nose-heavy, it did the Dumb-dance like no other! Crashed her by doing inverteds 3 ft. off ground, and snapping down...flat-spin landing, tore lower wing off...Jim Walker Wannabe? That's me!

My friend Dave Dawson and I have been messing around with the Bi-Slob a lot and he has gotten very good at flying his to the point of being able to prop hang his for minutes at a time and fly it almost like a kite. At the basin where we fly we have seen several Bi-Slobs crash including our own when we first got them due to the same problem mentioned above. You go to do a tight loop and the plane slows down and the line weight drops the inside wing tip and the plane falls like a stone. The best way to keep this from happening is to add an additional 1 1/2 oz to the outside wing tip. I believe my buddy Dave adds a little more then that to it but not sure how much.

>Just my thinking, I think the BiSlobs fly better and do
>better tricks if they are tail, heavy so when they do come
>uncoupled they tend to do funny things.I would love to be
>able to get the Slob swinging in and out and then give it
>full up run at it and let it do a vertical snap roll, step
>back and catch it on the end of lines before it crashed. Has
>any one done this yet.

Joe.
I have an E-mail I would like to pass on to you.

Would you please send me your addrdess.

Thanks.

Ken Nash at [email protected]

Marvin,

Could that be why it's called a Fool?

The worst thing about the Bi-Slob tail spins, at least the ones that I've witnessed, is that they are all total disasters. Nothing much left of the planes.

BUT, the engines survive nicely ... even after they've literally been screwed into the ground.

ADD NOSE WEIGHT!

Been there done that

I think that we are all on the same page here with Fox .35 powered Bi-Slobs.

But, what if ...

we drop in an LA-46 or a Fox Eagle .60? I know the prop hanging would be difficult ,unless you go to three-line, but would there be less chance of the BSTS?

Tighter loops? Maybe even enter a stunt contest?

When I replace the wings on my Creme de la Bieslaub I intend to power it with SOMETHING big!

The thing that makes snap rolls more common with biplanes is the excess drag, they slow down to a stall speed much more rapidly than a monoplane and if the power is limted to what it takes to do a Sabre Dance, there isn't enough excess power to accelerate out the stall speed/angle of attack quickly enough to save the plane before it snaps.
A Midwest Hornet and Johnson Blurr were noted snap rollers and the Veco Renegade had a milder tendency to do them. It's caused by too much elevator travel that will cause an accelerated stall abetted by a cooperative airfoil. The long tails on those three assisted in the anomaly.
Bare

LAST EDITED ON Oct-14-06 AT 08:07 PM (CST)
 
I fly a (+10%)900 sq's ST-60 in mine. Tail weight caused it to come in. I added nose weight and Things are perfect. LOTS-O-FUN

OK, Scott. My NIB Fox Hawk .60 will be my Bi-Slob's new power. How much offset? 5%?

By the way, folksies: The thread was originally about clockwise TAILSPINS caused by a combination of extreme motor offset and slack lines ... although the digressions are VERY INTERESTING!

>OK, Scott. My NIB Fox Hawk .60 will be my Bi-Slob's new
>power. How much offset? 5%?
>
>By the way, folksies: The thread was originally about
>clockwise TAILSPINS caused by a combination of extreme motor
>offset and slack lines ... although the digressions are VERY
>INTERESTING!

With the Slob .35 you should be flying on 52-55' Lines
5-7 degrees offset
one oz wing weight

With the 60
SAME THING
Maybe 1-1/2 oz wing weight

TRUST the plane. I went to six inch handle spacing. So much smoother. Wind at the back is the key to good slobin.
Try some nose weight. You just might be surprized.

OH the 60 size plane is way to much fun. Better all around

Scott, how much did you scale up the slob for .60 power?

I'm thinking this would be a good project for my OS MAX-H .60 R/C. Could adjust the throttle to get the power just right for fun! Probably wouldn't need any nose weight with a MAX-H in there either

Colin, THANKS for asking my next question!

CALLING SCOTT!