Initial Trim

[Ken Culbertson]

This may be the wrong forum so move it if it is:

I have completed the initial changes to the ARF Nobler I got to get me back in shape while I build a real airplane.  I need some advice from those of you who can trim a plane by just looking at it.  There is a problem with it rolling in on me on the 1st corner of the Reverse Wingover.  It is 20mi to our flying site so I can't be running out after work to put in a couple of flights everyday.  The plane is otherwise trimmed (I have followed Paul Walker's method).  Wings level,  CG a bit on the tail heavy side where I am used to it, turns the same inside and out, flap movement reduced to kill the float in the turns.  30+ point loops, squares, eights with great line tension till I try an upwind corner.  It literally rolls in on me.  I know how to avoid disaster when it does this but that is not how you get your pattern back in shape.  Some things stick out and I need opinions which one might be my best shot.

1) Tip Weight - the Top Flight nstructions say to add 1oz but the wing already has a fully buckshot loaded weight box in it.  The outboard wing will fall if balanced on the fuselage center line. Do they mean an additional 1oz?  I have tried to research this with no luck.

2) Leadouts - I added adjustable leadouts but all I have tried so far is moving the front (down) line back to 1/2" from where the Up line  was.  You can cure a lot of ills by moving the leadouts back only to create other issues.  Both already appear to be behind the CG.

3) Engine Offset - there isn't any.  I used to use 2 degrees.  Is that still enough?  I can see the .60 size planes pulling your arm off with that much offset.

4) Side area and Rudder - Added 5sq" area to rudder and some deflection.  Side area aft to the CG is huge in my opinion.

5) Prop - I was using a 10-6W.  Now using a Brodak 10-5.  Corners better, engine appears to run better.

6) Venturi - This is my least knowledgeable item.  The engine is a low mileage "Big Art" OS35s.  I have not touched it other than to take the back plate and head off twice to inspect.  The venturi is short and has about a 4-5cm center hole.  Am I perhaps cutting the power too much?  How big should it be?  Is tall better than short?

7) Finally I don't think I have wiped down this set of lines in about 30 years. To be fair, 29 of them were spent in a box but how much does that add to the drag?  They will be wiped on the next trip.

If anything on the list just jumps out at you and says "IDIOT", that is what I need to know.  The plane is in the shop getting a nose job.  I have had it with having to take off the spinner, prop, muffler and needle valve just to remove a cowl that is the wrong color and doesn't fit anyway. 

Thanks!

[Steve Helmick]

With as much wing offset as the Nobler has, if the outboard tip goes clunk when you set it upside-down on a table, your tipweight should be safe enough to start. Paul almost always says folks have too much tipweight.

However, if you like the CG kinda aft, then you'll need to move the leadouts kinda aft to match up. You could hang it from the leadouts from a single nail in the rafters to ensure the nose is down a tad. You might also run the "Line2" or "Line3" calculator to establish a better starting point for the LO location. Or, you could just get all scientific and set the LO's about 3/4" aft of the CG for now.

I'm with you on the engine offset...1 to 2 deg. is a good thing. If nothing else, when your lines go slack, they'll get tight again quicker. Can't find fault with that.

You're absolutely sure the wing is level, both upright and inverted? Are all hingelines sealed? Steve

[Tim Wescott]

Consequence of too much tip weight: your plane looks awkward in the maneuvers, particularly the square corners.

Consequence of too little tip weight: your plane is a splintered wreck, and you have pulled muscles from running away to save the plane, or yourself.

Does it roll in on the 2nd or 3rd corner of the wingover?  The 4th?  Have you done any other square maneuvers?  How does it fly at 45 degrees upright?  Inverted?  How does it do in the round manuevers, and inside compared to outside?

If it tends to go light on the lines every time you do a corner, then you have too little tip weight, or the leadouts are really in the wrong place, or the outside flap is considerably stiffer than the inside.  If the problem isn't obvious in the shop -- add tip weight, get the problem sorted, and take the tip weight out.

If it tends to go light on the insides and not the outsides, then you have a warp.  Either your flaps (or wing) are tweaked, and it's always rolled counter-clockwise as seen from the back, or your tail is tweaked, with the stab not level to the wings.  You should be able to put the spinner on the toe of your shoe and sight down the back of the airplane -- the stab should be perfectly parallel to the wings.  If it's rotated, fix it -- probably by cutting underneath the tail and compressing that side.

[Brett Buck]

This may be the wrong forum so move it if it is:

I have completed the initial changes to the ARF Nobler I got to get me back in shape while I build a real airplane.  I need some advice from those of you who can trim a plane by just looking at it.  There is a problem with it rolling in on me on the 1st corner of the Reverse Wingover.  It is 20mi to our flying site so I can't be running out after work to put in a couple of flights everyday.  The plane is otherwise trimmed (I have followed Paul Walker's method).  Wings level,  CG a bit on the tail heavy side where I am used to it, turns the same inside and out, flap movement reduced to kill the float in the turns.  30+ point loops, squares, eights with great line tension till I try an upwind corner.  It literally rolls in on me.  I know how to avoid disaster when it does this but that is not how you get your pattern back in shape.  Some things stick out and I need opinions which one might be my best shot.

1) Tip Weight - the Top Flight nstructions say to add 1oz but the wing already has a fully buckshot loaded weight box in it.  The outboard wing will fall if balanced on the fuselage center line. Do they mean an additional 1oz?  I have tried to research this with no luck.

2) Leadouts - I added adjustable leadouts but all I have tried so far is moving the front (down) line back to 1/2" from where the Up line  was.  You can cure a lot of ills by moving the leadouts back only to create other issues.  Both already appear to be behind the CG.

3) Engine Offset - there isn't any.  I used to use 2 degrees.  Is that still enough?  I can see the .60 size planes pulling your arm off with that much offset.

4) Side area and Rudder - Added 5sq" area to rudder and some deflection.  Side area aft to the CG is huge in my opinion.

5) Prop - I was using a 10-6W.  Now using a Brodak 10-5.  Corners better, engine appears to run better.

6) Venturi - This is my least knowledgeable item.  The engine is a low mileage "Big Art" OS35s.  I have not touched it other than to take the back plate and head off twice to inspect.  The venturi is short and has about a 4-5cm center hole.  Am I perhaps cutting the power too much?  How big should it be?  Is tall better than short?

7) Finally I don't think I have wiped down this set of lines in about 30 years. To be fair, 29 of them were spent in a box but how much does that add to the drag?  They will be wiped on the next trip.

If anything on the list just jumps out at you and says "IDIOT", that is what I need to know.  The plane is in the shop getting a nose job.  I have had it with having to take off the spinner, prop, muffler and needle valve just to remove a cowl that is the wrong color and doesn't fit anyway. 

Thanks!

   This may be helpful:

https://stunthanger.com/smf/open-forum/functions-of-trim-adjustments/msg66267/#msg66267

   Brett

[Ken Culbertson]

Does it roll in on the 2nd or 3rd corner of the wingover?  The 4th?  Have you done any other square maneuvers?  How does it fly at 45 degrees upright?  Inverted?  How does it do in the round manuevers, and inside compared to outside?

Under 45 degrees if flies beautifully.  Turns a little better outside than inside and (thanks to your advice to check for stab tilt) I noticed that there is no tilt BUT the flaps are down about 2-3 degrees with the stab level - oops.  Now I know why it tracks like flat as a pancake inverted and bounces a bit upright. That has to be fixed but it is not causing my problem.  I checked the stiffness and both flaps are the same.

To answer your question on the 2nd & 3rd corner - I have never gotten that far.  Anything that requires an upwind corner triggers evasive actions.  As a result I have not tried that corner inverted since it is the only one in the pattern.  Inside and outside squares are effortless and no loss of tension at the top of the eights.  2nd corner of the hourglass a bit light but controllable.  The only maneuver I cannot do at all is the wingover.  Overhead eights are a religious experience and the 3rd loop of the Clover is loose.

I am thinking that I am going to add tip weight till it droops and move the leadouts back till it stops.  I used to fly with Bob Gieseke before adjustable leadouts were just part of any new ship.  I have seen him move them as much as 3" in one day so there must be something to it.  If it was practice time, the wind was under 20 and it wasn't raining, Bob flew.

Thanks a bunch.

[Ken Culbertson]

   This may be helpful:

https://stunthanger.com/smf/open-forum/functions-of-trim-adjustments/msg66267/#msg66267

   Brett

Thanks Brett - It was helpful.  You can't get your reflexes back if your plane flies worse than you do! 

[Tim Wescott]

To answer your question on the 2nd & 3rd corner - I have never gotten that far.  Anything that requires an upwind corner triggers evasive actions.  As a result I have not tried that corner inverted since it is the only one in the pattern.  Inside and outside squares are effortless and no loss of tension at the top of the eights.  2nd corner of the hourglass a bit light but controllable.  The only maneuver I cannot do at all is the wingover.  Overhead eights are a religious experience and the 3rd loop of the Clover is loose.

Overhead eights -- because they're so beautiful you thank God, or because they're so scary they make you pray?

If you can't do the first turn of the wingover because it's upwind, how are you doing the first turn of the overhead eights, which is identical but for your body position?

I'm wondering if you may be down on power.  I've never used the OS 35S, I understand it's a great engine -- but it's still a baffle-ported 35.  Most of the Nobler ARFs that I've seen have bigger engines (even a 46LA makes a good engine for that plane, but only because it is Stunt's most Versatile Engine).

[john e. holliday]

My ARF Nobler started life with box stock Fox .35 Stunt.   It was assembled per instruction after replacing the lead outs and bell crank.   It flew great for me right from the start.  Full pattern on second flight.  It now hangs with an EVO 36 on the nose minus the cowl and about 1 ounce of lead on the tail.   It still flies great but fuel tank is not large enough.   Need more break in the EVO.   

Sounds like you need to put every thing back to kit settings and balance with the heavier engine.   Also I fly on .015 X 60 cable center of handle to center of plane.   

[Ken Culbertson]

My ARF Nobler started life with box stock Fox .35 Stunt.   It was assembled per instruction after replacing the lead outs and bell crank.   It flew great for me right from the start.  Full pattern on second flight.  It now hangs with an EVO 36 on the nose minus the cowl and about 1 ounce of lead on the tail.   It still flies great but fuel tank is not large enough.   Need more break in the EVO.   

Sounds like you need to put every thing back to kit settings and balance with the heavier engine.   Also I fly on .015 X 60 cable center of handle to center of plane.   

Did you change the leadout positions when you changed the bellcrank or add tip weight?

[john e. holliday]

No.  It was assembled box stock. except for lead outs and bell crank.

[Ken Culbertson]

Overhead eights -- because they're so beautiful you thank God, or because they're so scary they make you pray?

If you can't do the first turn of the wingover because it's upwind, how are you doing the first turn of the overhead eights, which is identical but for your body position?

I'm wondering if you may be down on power.  I've never used the OS 35S, I understand it's a great engine -- but it's still a baffle-ported 35.  Most of the Nobler ARFs that I've seen have bigger engines (even a 46LA makes a good engine for that plane, but only because it is Stunt's most Versatile Engine).

Tim - I know this is old but after re-reading this thread I thought you might like to know what made this plane a star performer.  You hit of the problem when you mention not having the problem in the OH8.  That got me thinking.  It was power and with 3oz less nose weight by the 8, it stayed out.  Also, since the entry corner of he OH8 is not judged, I do tend to whip it and soften the corner a bit.  So I went back to my 10 x 6w prop and cranked the engine up a bunch.  No more coming in on me.

It now flies better than I do which is all you can ask of a practice plane.

Thanks

[Tim Wescott]

Tim - I know this is old but after re-reading this thread I thought you might like to know what made this plane a star performer.  You hit of the problem when you mention not having the problem in the OH8.  That got me thinking.  It was power and with 3oz less nose weight by the 8, it stayed out.  Also, since the entry corner of he OH8 is not judged, I do tend to whip it and soften the corner a bit.  So I went back to my 10 x 6w prop and cranked the engine up a bunch.  No more coming in on me.

It now flies better than I do which is all you can ask of a practice plane.

Thanks

Thanks for the update.