Gieseke Bear Nobler trimming issue

[Ivan Bolton]

Hi all I have built this Bear Nobler which  generally flies very well indeed.  It's powered by a Tom Lay tuned ST 51 and weighs around 59 ozs.  However I have a trimming issue.  When provoked for example in the bottom corner of a triangle or the bottom corner of the hourglass it drops the outer wing - sort of hinges.  It can be made to do it in the bottom corner of squares also by pulling hard.  The model flies level  inverted and upright without any trim on the trim tab.  It's very smooth in all of the other manoeuvres and shows no vices.  I have tried removing lead from the tip - no effect.  I have moved the leadouts back and forth no effect.

Any ideas anyone??

[Dave_Trible]

Ivan I would first suspend the airplane from the lead outs and adjust the lead out guide until the airplane hangs nose down. 1 1/4-1 1/2 degrees.  Seal the hinge lines-especially flaps. Keep pulling out tip weight until the tip stays up. You may need more outboard flap area in the form of an added tab.  A fair way to check this is to do tight horizontal eights with the intersection at or above 45 degrees. Watch the intersection to see if the airplane shows a rolling motion either way right when you change control direction.  Bob G told me many years ago if its above 45 it's flaps-if it's below 45 it's tip weight. That's quite true unless the flap assymetry is just too far off. Try the tip weight until  that tip rides high and/or the line tension gets too light.

Hope it helps

Dave

[proparc]

Sounds like a classic case of not enough tip flap area to me. Based on the photo,it looks like you have none

Where's Mr. Buck on this one!

[Doug Moon]

I have built several of this version.  They are good flyers but they have some quirks about them for sure.
Measure the span of your inboard flap vs the span on the outboard flap.  As noted the flaps are very small especially out towards the tip of the flap.  It might be possible your inboard is longer than your outboard if you built in the assymetry, so we are not talking much, but it can be enough.  I have had this very situation.  On one of my models that was 52oz with a piped PA 65 witgh the inboard flap longer than the outboard and it had no issues and I flew it all over the place including the nats for years. On the same model built later that was 60oz with an OS52 it showed up.  Just like you are talking about.  

Bob always said keep it light.  You can tell with the small flaps light weight was always on his mind.  

How to fix it?
As mentioned above be sure to tape the hinge lines on the flaps.  If this doesnt cure it.  Probably wont.  This maybe a bigger issue than a leaky gap.  
You will need to add a tab to the outboard flap as far out as possible.  How big?  Enough area to make the outboard total area just a little larger than the inboard.  I thin hard piece of clear plastic inserted into the trailing edge several inches long sticking out 1/2" or less might do the trick.  Measure each flap and find the area and compare.  Then you know how big to make the tab to get the sizes equal or a little more on the outboard side.

Please keep us informed of how it goes.

[Gene O'Keefe]

Those T&L .51's run great don't they ? ( I have two from Tom ) ... looks like an APC prop - what size ? ...very nice looking model.

[Randy Cuberly]

I have built several of this version.  They are good flyers but they have some quirks about them for sure.
Measure the span of your inboard flap vs the span on the outboard flap.  As noted the flaps are very small especially out towards the tip of the flap.  It might be possible your inboard is longer than your outboard if you built in the assymetry, so we are not talking much, but it can be enough.  I have had this very situation.  On one of my models that was 52oz with a piped PA 65 witgh the inboard flap longer than the outboard and it had no issues and I flew it all over the place including the nats for years. On the same model built later that was 60oz with an OS52 it showed up.  Just like you are talking about.  

Bob always said keep it light.  You can tell with the small flaps light weight was always on his mind.  

How to fix it?
As mentioned above be sure to tape the hinge lines on the flaps.  If this doesnt cure it.  Probably wont.  This maybe a bigger issue than a leaky gap.  
You will need to add a tab to the outboard flap as far out as possible.  How big?  Enough area to make the outboard total area just a little larger than the inboard.  I thin hard piece of clear plastic inserted into the trailing edge several inches long sticking out 1/2" or less might do the trick.  Measure each flap and find the area and compare.  Then you know how big to make the tab to get the sizes equal or a little more on the outboard side.

Please keep us informed of how it goes.

My guess is Doug (our current National Champion) knows about as much about this particular airplane as anyone...so I would definitely listen to him.

Looking at the pictures it would seem that your outboard flap is significantly shorter than the inboard flap and that's a prescription for exactly what you described on just about any stunt plane.  If anything the Outboard could be a little longer than the inboard and cause fewer problems that could be corrected with more tip weight. 

Randy Cuberly

[RandySmith]

Hi all I have built this Bear Nobler which  generally flies very well indeed.  It's powered by a Tom Lay tuned ST 51 and weighs around 59 ozs.  However I have a trimming issue.  When provoked for example in the bottom corner of a triangle or the bottom corner of the hourglass it drops the outer wing - sort of hinges.  It can be made to do it in the bottom corner of squares also by pulling hard.  The model flies level  inverted and upright without any trim on the trim tab.  It's very smooth in all of the other manoeuvres and shows no vices.  I have tried removing lead from the tip - no effect.  I have moved the leadouts back and forth no effect.

Any ideas anyone??

Why don't you try adding a trim tab to the outboard flap, about 1 sq in, and seal the hinglines on flaps and elev.
The 60 ounce weight could be a big issue in causing this, You may wind up making larger flaps
first see if the tab and sealing stops it.

Regards
Randy

[Brett Buck]

Sounds like a classic case of not enough tip flap area to me. Based on the photo,it looks like you have none

Where's Mr. Buck on this one!

   There may be no way to put enough flap area on this one, it's only works to some extent. I assume that the airplane is stalling in the corners due to excess weight.

    Brett

[Steve Fitton]

Any possibility that the big, heavy APC out front is contributing to these issues?


Oh, and nice looking model you have there!  I am especially partial to models with yellow on them for some reason. 

[Avaiojet]

I edited this reply because I thought he had an adjustible tab on the wingtip.

Charles

[Ted Fancher]

Ivan,  if this is a problem you can't live with (I wouldn't!) you might want to consider replacing the flaps if sealing the hingeline doesn't make the stall go away.  As Brett suggested, this is almost certainly a wing loading issue and the defining characteristic of Bob's Bears and its precursors (Gieseke Noblers) was a significant reduction in flap chord and span versusthe Nobler on which they are based in search of tighter corners for Bob's FAI endeavors.

Although 59oz is a "lot" for any Nobler it isn't insurmountable particularly with the extra power you've installed.  I would plan to use full span flaps that have a chord of approximately 20% of the total (wing plus flap) chord from root to tip.  This will significantly increase your ability to keep the excess mass aloft during maneuvering and should have no negative effects that can't be corrected easily  (the airplane will be a little slower responding to control inputs but the desired respose can be regained by increasing line spacing at the handle, for instance).  The bonus will be that you can maneuver aggressively without stalling.  Be sure to seal the hingelines as discussed in may SH threads.

I also noted you've got the outboard "fixed" end of the flap deflected up, probably to counter a warp causing the outboard wing to fly high when upright.  I'd encourage you to attempt to straighten the wing so that it isn't necessary to have a "roll tab".  If you're unable to unwarp the wing consider "tweaking" the outboard flap up a hair relative to the inboard to combat that roll tendency...keeping the full span flaps. 

Finally, it's safe to say you'll "never" want more inboard flap area/span than outboard so don't ever start out that way.

Ted Fancher

[Ted Fancher]

A quick PS to the above.  You might want to try simply flying a couple tenths of a second faster per lap and see if the hinging/stalling goes away.  Lift goes up as the square of airspeed and if a bit faster lessens or eliminates the problem it'll give you an idea as to whether or not to go to the effort to replace the flaps which will likely allow you to fly at the lap times you prefer without suffering the evil consequences.

Ted

[Ivan Bolton]

Just to let everyone know I have been reading the replies to my trimming problem  avidly.  I am really most  grateful for all of the helpful,  knowledgeable and experienced advice given  in answer so far to this problem. 

To answer to a few queries.  The prop is an APC 12X6 but I have also tried a wooden RSM 12X5.5 wondering indeed was that contributing,  but alas  no.   The trim tab is now actually level (the photo was taken just as the model was finished and  before the it was trimmed and the tab had only had its linkage attached and wasn't set).   The TL 51 (one of two  I got modified one Italian one Chinese)  performs beautifully and I'm very pleased with it.  I have not tried the Italian one yet.

The wings are asymmetrical as per plan and indeed the inner flap is longer than the outer and therefore has more area (now I know better!!!)

From what you all say my inclination is to construct a set of larger flaps eventually with the areas corrected, according to Ted's calculations  (built up and sheeted to save weight),  having first tried Doug's suggestion of the area enlarging flap trim tab perhaps  as proof of concept.

Interestingly the model does not show any signs of this vice in square outsides even if I provoke it. 

I'll also lean the motor a bit (there is  some headroom to do this)  as Ted suggests to see if the problem is alleviated by a slightly faster lap time.  I very much like the way this model flies and I think is is a good match  for  the ST 51 and I will be delighted if I can get this issue sorted: I don't think I can live with it!!

[Steve Fitton]

What lap time have you been flying at up to this point?

[Howard Rush]

Interestingly the model does not show any signs of this vice in square outsides even if I provoke it.

This suggests that there may be a warp in the wing or flap (or both) or an anomaly in the front part of the upper surface of the outside wing.

[RandySmith]

This suggests that there may be a warp in the wing or flap (or both) or an anomaly in the front part of the upper surface of the outside wing.

Howard is correct  and It also could be a misalignment between the flaps-and -stab/elev. Check those carefully.
 That cause the same problems  too, and as I said earlier, you may want to replace the flap with larger ones. Right at 60 ounces is a lot for a plane Bear recommended to fly at 42 ounces

[Joseph Lijoi]

Howard is correct  and It also could be a misalignment between the flaps-and -stab/elev. Check those carefully.
 That cause the same problems  too, and as I said earlier, you may want to replace the flap with larger ones. Right at 60 ounces is a lot for a plane Bear recommended to fly at 42 ounces

Randy...I think this is a Bear Nobler which is about 650 square inches.  The Gieseke Nobler is about 500 square inches which is what I think you are referring to when yoau mention the 42 ounce weight.  Maybe some clarification is needed.  Up to you guys if 60 ounces is too heavy for this ship at 650 squares.  I think the original Bear was in the low 50 ounce range.

[Ivan Bolton]

Joseph is right about the size of this Nobler, it is not the 35/40 sized Gieseke Nobler as kitted by Topflight or as per the UHP component kit..  It states on the plan that: 'this model should be kept to under 60ozs',  it doesn't say how much under 60 ozs, mind!! 

The plan was drawn by Steve Moon in circa 1995.  I seems to have been designed for a piped 40/46 motor, hence my feeling that it would be fine for  the TL tuned  ST 51.

[RandySmith]

Randy...I think this is a Bear Nobler which is about 650 square inches.  The Gieseke Nobler is about 500 square inches which is what I think you are referring to when yoau mention the 42 ounce weight.  Maybe some clarification is needed.  Up to you guys if 60 ounces is too heavy for this ship at 650 squares.  I think the original Bear was in the low 50 ounce range.

Hi Joseph
I think your right, I went back and took a close look at the plane,I had just never heard Bob refer to it as a Nobler, just called it the Bear, I have flown many of these Bob built, I think his were around 52 or so ounces, so 59 wouldn't be a dealkiller.
I would still recommend the same things, add a tab to the outboard flap
Seal all the hingelines,
and Check the alignment of the plane wing flaps elev and stab

Thanks
Randy

[Brett Buck]

Randy...I think this is a Bear Nobler which is about 650 square inches.  The Gieseke Nobler is about 500 square inches which is what I think you are referring to when yoau mention the 42 ounce weight.  Maybe some clarification is needed.  Up to you guys if 60 ounces is too heavy for this ship at 650 squares.  I think the original Bear was in the low 50 ounce range.

     So, its not a Nobler?  That's a different story. However, it is a very familiar story that our current National Champion should know all about:

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=8593&mesg_id=8593&listing_type=search

    One for the ages.

    Brett

[RandySmith]

     So, its not a Nobler?  That's a different story. However, it is a very familiar story that our current National Champion should know all about:

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=8593&mesg_id=8593&listing_type=search

    One for the ages.

    Brett

So as they say......whatz old is new again !!   :-)

Randy

[Doug Moon]

    So, its not a Nobler?  That's a different story. However, it is a very familiar story that our current National Champion should know all about:

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=8593&mesg_id=8593&listing_type=search

    One for the ages.

    Brett

I have actually built 5 different versions of this particular model.  Only one would not fly well enough to compete and that was my fault as the weight at inital flight was 70oz.!!  HAHAHAAHAH  What a disaster that was.  That was my second attempt.  My first one was 54oz and built with just enough wood to get it through one season and then it folded up.  So on the second one my thinking was "This one isnt going to break up on me."  Hence the excessive weight!  That was so long ago too!  What a ride it has been. The next one took me to within 3 points of wining advanced at the nats and many expert wins along the way.  It started out at 52 oz. with PA 61 later getting a 65. I got a ton of instruction and building tips on that one that I still use today.  It lasted many seasons.  The model in the thread BB referenced is the 4th one I built.  The last one was 630 sqrs with an ST60. Its gone too.   maybe one day I will build another one these with a more blunt LE.


Reply 77 explains the problem with model #4.  Once I corrected that it actually became a pretty good flier.  Even at that weight.  I flew it for a while and now it is somewhere up in the northeast last I heard.  I even saw it making flights at Brodak in Flying Models one year.    

It should be noted the plane had much larger flaps than were originally built due to the stall caused by the improper controls.  So with the proper control ratios the larger flaps made the plane a very good flier. It was docile and preditable. A great combination. 

I didnt go back and read that whole thread but there is a lot of info in there.

[SteveMoon]

When I inked the plans around 1998, Bob G said that the plane had never actually
been given a formal name, but was commonly referred to as the Bear. He told me
to call it The Bear Nobler on the plans as this was an evolution of the Gieseke Nobler,
in particular the yellow G N that Bob had flown with a piped Super Tiger 34. The Bear
has a wing area of 650 sq in, and span of 55.75".

This plane later evolved into the '99 Bear which was a larger version, then the 'Big Bear'
which is what Doug has been flying since the early 2000s.

Steve

[Doug Moon]

...then the 'Big Bear'
which is what Doug has been flying since the early 2000s.

Steve

Sometimes you hear it referred to the Geo-Bear as well, since it uses a Geo-Bolt wing.  This is the plane that I fly and I named the Riff Raff per the paint scheme.  If that makes any sense...