Smoothie, lacks line tension

[Allen Eshleman]

About two weeks ago my "cranky Nobler" met it's demise for now anyway,  hitting a light pole.  I was just getting it trimmed.  I tried longer lines, thinking they were 60 ft.  However, they were 70 ft. 

No problem,  I had an already built Smoothie from someone's cache.  My brother transferred the B-40 and Nobler Tank to the Smoothie.

So far,  I have had three flights.  I haven't done anything more than inside loops for several reasons.

1.     Line tension is not real good, despite a 1/4 inch or more rudder off set.

2.     Engine run is not consistent yet.  I am using the Brodak Nobler tank - Uniflow.  The fill line is at 90% to the airflow.  The overflow is capped off during flight.  No real good 4-2 like I had with a standard vented tank.  I'm using Brodak 10% nitro 11/11 castor/synthetic fuel.  Fox RC gold long Glow Plug.   First flight was with an 11.5/4 APC prop that got nicked up due to hitting the ground during take-off.  The last two flights were with an APC 10/5.  I still have and APC 11/4 to try,  APC 10/6,  and a Top Flight 11/4 wooden propeller.  I also have some Top Flight 11/6's which pulled well in the Nobler.

What can I do to increase the line tension.  It doesn't have adjustable lines.  That doesn't mean they can't be changed.

Any ideas would be welcome 

[Wynn Robins]

go through the same things you did with your nobler -


check the "rake" of the leadouts by hanging the plane by the leadouts and observing how the fuselage hangs in the horizontal plane - (I am picking you will see it tail down )

move the leadouts back until the nose is level with the ground - or slightly down

if it is nose down - move the leadouts forward until the fuse is level (or nose slightly down)

check your tip weight - this should be just enough to make the wings track through loops the same upright and inverted

use a bigger prop

rudder offset does not create tension - it creates YAW - which you dont want......and you will find out why in square corners!!!

[Dick Pacini]

The Brodak B40 instruction manual says to use a 10-5 prop.

[Wynn Robins]

The Brodak B40 instruction manual says to use a 10-5 prop.

and real world learning says a bigger prop helps with line tension - and the Brodak 40 is happy with an 11" prop up to 6" pitch.....

[Derek Barry]

more tip weight, more pitch. that will get you started.

[Matt Colan]

use and 11 inch prop, check your leadouts, tip weight, and line length.  I'm using 60 foot .015s on mine, with a Brodak 40 and an 11-5 Zinger prop.  I also think I got about 1 ounce of tip weight in mine.

[peabody]

I believe that the rudder offset is way too much....the full panel wing offset is plenty
An "area tab" on the outboard flap helps (4 square inches).
Leadouts ful forward...

Have fun.

[Derek Barry]

I believe that the rudder offset is way too much....the full panel wing offset is plenty
An "area tab" on the outboard flap helps (4 square inches).
Leadouts ful forward...

Have fun.

I agree with the rudder offset being too much. I do not use any rudder offset.

If you are having line tension problems you move the leadouts BACK!!! This will point the nose of the plane away from you!

 Butt he already said that his leadouts were NOT adjustable.

[Steve Fitton]

Just out of curiosity, what sort of lap times on what length lines is this low line tension Smoothie getting?

[Eric Viglione]

Just out of curiosity, what sort of lap times on what length lines is this low line tension Smoothie getting?

Bingo! That's my first question too, since most trim options you are going to try are speed sensitive adjustments. A small plane like a smoothie usually needs need to fly about 5.0 - 5.2 laps on 57-60ft lines, depending on it's weight, to be in the ballpark before I even thought about playing with trim. This should buy you some line tension too.

I would also make 100% sure the tank is shimmed for equal inverted and upright laps first too. If you don't have a symmetrical engine run of the proper speed, it's not time to evaluate trim yet. For instance, if it get's loose on outsides, and the motor is also richer on outsides, then there may be nothing wrong with the trim, just the speed on outsides, etc. Once you do get a reasonable lap time, and the tank shimmed, trim to suit whatever's left that it's still doing wrong.

My .02 for what it's worth,
EricV

[jim welch]

Allen , you gotta admit when you ask a trimming question here you sure do get some talented answers and advise (Dick,Wynn,Rich,Matt,Derek,Steve,Eric),these guys can make a 2x4 turn a corner......a couple of these gentlemen helped me fix my smoothie at a down south contest.Mine rolled across the circle inverted from the overhead, did 2 outside loops, cut off and i gave it full up when it hit the end of the lines,  cut off,did an inside loop and landed very nicely.All of that from giving it up from the top of the circle to the dramatic end and landing.With lots of advise and laughter, took out the rudder offset,outboard 1.0 oz wingweight,double star 40 lite on 11.6 prop,58 foot lines,10 % fuel,never slower than 5.0...4.8, better lap times and flys very nicely.I also bought the brodak tank for the smoothie...solved all the run problems.......Jimmy

[Steve Fitton]

Allen , you gotta admit when you ask a trimming question here you sure do get some talented answers and advise (Dick,Wynn,Rich,Matt,Derek,Steve,Eric),these guys can make a 2x4 turn a corner......a couple of these gentlemen helped me fix my smoothie at a down south contest.Mine rolled across the circle inverted from the overhead, did 2 outside loops, cut off and i gave it full up when it hit the end of the lines,  cut off,did an inside loop and landed very nicely.All of that from giving it up from the top of the circle to the dramatic end and landing.With lots of advise and laughter, took out the rudder offset,outboard 1.0 oz wingweight,double star 40 lite on 11.6 prop,58 foot lines,10 % fuel,never slower than 5.0...4.8, better lap times and flys very nicely.I also bought the brodak tank for the smoothie...solved all the run problems.......Jimmy

Ha!  That wasn't two outside loops, that was a spin!  I was sure that plane was toast, that save was a great example of not giving up on a hopeless situation

[Larry Cunningham]

I had a Twister that taught me enough to get through the pattern. It had the rudder offset (about 1/4") indicated on the plan. An outside loop just touch the rudder against the ground and broke it off - the ship kept flying, and I suddenly noticed considerably improved line tension.  So I cut the rudder apart and installed it completely flat and it worked well.

Later I crashed that ship several times, and broke its nose off.  I had been using an angled plastic engine mounting plate, 2 degrees. However my repair amounted to two pieces of 1/8" Lite Ply glued to either side of the nose. This left the nose too thick to use the engine mounting plate, so I mounted the motor flat. Again, I noticed an improvement in the line tension. A couple of things were involved: 1) the engine offset was 0 degrees, and 2) the model was a bit nose heavier.

After I built one with adjustable leadouts, I initially set the leadouts far aft; the model didn't seem to have particularly good line tension. Bill Melton saw it and said I needed to move the leadouts FORWARD, which I did, and found some improvement. It seems that having the model crabbing along is not optimum trim for maximizing line tension.

These features were all counter to my initial assumptions. In summary, if the model is in good trim it typically has good line tension.

One final note, as you learn to fly better your model may seem to have better (or at least acceptable) line tension. One likely reason is that you are flying smoother, and the model loses less energy to jerking movements. In addition, you learn to trust the model a bit more and realize that it can be maneuvered even with very little line tension.

The other feature is that an experienced pilot becomes quite good at energy management, trading off kinetic and potential energies, including smoothly altering the diameter of the flight hemisphere.

It all adds up to trimming and flying expertise that we see exhibited by better Stunt fliers.

Just sayin' - remember, these are my opinions and I've never won a Nats. ;->

L.

"To believe in something, and not to live it, is dishonest." -Ghandi

[peabody]

not to take the Champ to task....BUT, if the aeroplane lacks line tension overhead, moving the leadouts forward generally helps...it cuts the yaw way down.
most do not complain about a lack of line tension when flying level......
have fun!!!