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Long time problem possibly solved

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Long time problem possibly solved

Post  Cribbs74 on Thu Apr 24, 2014 6:32 pm

As you all may well know the old Ebay Ringmaster was my entry bird to .35 sized planes. It has served me well, but has always been a little squirrely when power was down or the winds were higher than 8mph. I remember the first time I flew it I was told it was tip high level and inverted, to compound the problem I had an engine issue developing at the same time which came to light when the rod let go last year. After I repaired the engine and the power was on point I forgot all about the tip high.

Last weekend during flight the winds were around 8-10mph and I noticed some of that old silliness that was happening a year ago. Since my covering from my last repair removed itself in flight I took some time and checked my wing drop. Lo and behold my wing was falling on the inboard side! It dawned on me that I never did the check after I built it and just added the standard 1oz and flew it.

So.... I have added some more weight and I hope it will cure this ongoing problem. The Ringmaster doesn't fly as well as my PA planes, but is a heck of a lot of fun in it's own right.

And here I was considering retirement for it!

Ron
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Re: Long time problem possibly solved

Post  RknRusty on Thu Apr 24, 2014 8:17 pm

I bet it really will fly better now. The breeze could have been getting up under that tipped up wing and flipping it in on you. Plus whenever you pull out of a bottom corner, that wing is jumping up too, even in calm conditions. When I'm checking a plane out, I was taught to fly a bunch of lazy 8s and keep an eye out for that outboard wing lifting or dropping in the corners, especially if you make hard turns.
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Re: Long time problem possibly solved

Post  Ken Cook on Thu Apr 24, 2014 8:27 pm

Ron, a few things can happen with a Ringmaster. The original which what you have is even more prone to this problem. The wing itself due to design lends no torsional resistance other than the covering. Covering when this plane was designed was silk or silkspan. Iron on coverings provide some torsional strength but they need to be constantly monitored. Adding tip weight may solve the tip high situation, but it's not the correct remedy. It would be far better to twist the  wing (Inboard or outboard)  reheat and lose the tip weight. When the momentum of that weight get's going it becomes that much harder to stop it. This means that when you start into a outside maneuver for instance, at the bottom of the outside loop, the wing can dramatically drop due to the weight in that tip wanting to keep going. The complete opposite can happen in the inside maneuvers but this can make the outboard tip rise up at the top of the circle which can result in the plane flying back into the circle. A properly trimmed Ring on .015's shouldn't need anymore than 5/8 oz. of tip weight. This is all speculation though. I have no idea of the weight of the wings panels inboard vs outboard or if crash damage has plagued the wing in the past. I'm just stating that excessive tip weight should be discouraged.

The solid leading edges of the Ring also break right where they exit the fuse. This can also cause funny business. We fly them hard and after a few hundred flights they start developing fractures at the fuse. This can be expedited by hard landings and hard maneuvers. The wing just doesn't fall off and sometimes even goes unrecognized. Flexing the wing manually usually reveals this condition. If  the wing is tip high, I would sight down each trailing edge and determine which might be the culprit and heat and straighten. A simple trim tab made from light aluminum like soda can material taped onto the trailing edge of the outboard wing can provide a lot of adj with little weight penalty. Ken


Last edited by Ken Cook on Thu Apr 24, 2014 8:49 pm; edited 1 time in total
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Re: Long time problem possibly solved

Post  RknRusty on Thu Apr 24, 2014 8:38 pm

Ken, I'm glad you posted that. There's a lot more to trimming than I know, so I probably should refrain from giving advice.

I've had to add a trim tab to the Yak because the flap coupler is impossible to bend. I've had it twisted way way out of shape trying to get the outboard flap down, and it springs back to the original position. I finally cracked it, wicked it with CA and made a tab.
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Re: Long time problem possibly solved

Post  Cribbs74 on Thu Apr 24, 2014 8:50 pm

Ken,

I worked very hard to get my wings straight!  lol! 

A trim tab may cure the problem and thank you for the advice. I have cracked the Leading edge in two places during an abrupt ground contact during an outside. This was the reason the outboard wing covering was removed to begin with.

I was always under the impression that the outboard wing should drop when held nose to tail. In this case the inboard wing was dropping.



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Re: Long time problem possibly solved

Post  Ken Cook on Thu Apr 24, 2014 9:03 pm

I had no intent to criticize your building. My point was to be interpreted as no matter how straight you build a wing, the covering once shrunk is going to twist the wing. This can have a aileron affect on the wing causing one or the other to fly tip high. When I stated wing drop, I meant that this is happening during flight. Yes, you do want the outboard wing to drop first over the inboard. The concerns are when too much weight is applied to the outboard wing. A few factors can contribute to a plane flying tip high. A warp, a fuse not glued square to the root, a stab that may be slightly crooked. I've also seen trailing edges not properly squared to the tip of the rib which also can cause a aileron input to the wing. Again, I didn't want this to sound condescending. I was just stating that working with the wing and this usually takes two, can give you very good flying results without the funny business of having too much wing tip weight. Ken
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Re: Long time problem possibly solved

Post  Cribbs74 on Thu Apr 24, 2014 10:18 pm

Ken,

I didn't feel you were criticizing at all. I always feel you give sound advice. To be totally honest I am mediocre when it comes to building a straight wing. I rely on the shrinking to correct my deficiencies.  Laughing 

As you know this plane was in pretty rough shape when I received it. The wood was brittle and yet still Sterling heavy... I wouldn't be surprised at all if heavier wood was used on the inboard wing.

I have sighted down the wing at every perceivable angle and it's straight. I will try and fly it with the extra tip weight and if it still wants to behave poorly I will start experimenting with trim tabs.

I have another built, but unflown late 50's Ringmaster hanging from my shop ceiling. I may go through it and start over again.

Ron
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Re: Long time problem possibly solved

Post  roddie on Fri Apr 25, 2014 12:10 am

Looking through my plans.. the "Voodoo" (Riley Wooten-Carl Goldberg kit G-13) has a 1" longer inboard wing panel. I thought it was the opposite.. to possibly omit tip weight. There is one extra #2 inboard rib.

Here's a Ring wing and fuse (kit S1-395) I have that my Uncle built about 30 years ago. I need to figure out engine mounts for a Fox .35 It doesn't seem to be anywhere close.


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Re: Long time problem possibly solved

Post  OVERLORD on Fri Apr 25, 2014 12:38 am

Roddie,

The outboard wing is shorter because when flying in circles, the distance covered by the outboard wing is longer than the distance covered by the inboard wing. As they are both connected to each other,  the outboard wing has a higher speed. Therefore it gives more lift. To compensate that, the wing is shorter. The starboard wing tip weight is to compensate the weight of the lines pulled by the inboard wing.



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Re: Long time problem possibly solved

Post  roddie on Fri Apr 25, 2014 12:57 am

Thanks Lieven. That certainly makes sense. I just identified a partially-built wing that was given to me many years ago by my Uncle... as belonging to that "Voodoo" I mentioned. I do have the 1/2 size plan.. but no other parts or kit-box to have made the connection previously. It was given to me almost 30 years ago.. along several other unfinished models/plans etc. that I've managed to save after all these years.
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Unequal wing lengths

Post  Oldenginerod on Fri Apr 25, 2014 5:41 am

Good information on wing length guys.  

A while back I was given 2 models called a "Jitterbug" I believe.  They were apparently scratch built by the older gent who gave them to me using plans from local Melbourne hobby shop Hearn's Hobbies.  I rememger going there as a kid on my rare visits to the city and drooling over all the stuff they had- that's another story.  

Both planes look virtually the same except that one has a longer inboard wing.  I could never figure out why.  It always seemed back-to-front to me because the longer wing, to my untrained thinking, would create more drag and inboard weight, causing the plane to turn in.  This is, I believe a later build due to plastic film covering being used instead of tissue like the other plane, which has even length wings.  The previous owner was a little vague about the planes, but remembered that 20-30 years ago his kids all learned to fly on them.  They show no battle scars whatsoever so must have performed adequately.  I wonder whether the earlier build had some bad habits so the second build was altered to try to overcome a problem.  I'm only speculating here, but maybe that's my answer.
He couldn't remember what engines he had used on them, but at 24"-26" spans, I suspect an .09 was used.  The older tissue covered version might get a Cub .09 for period correctness and be kept for display, with the more robust film covered one probably getting an Enya .09 (if it's not too heavy) and being flown.  (I know talk a lot about flying but never seem to get out for a go- uncooperative family I'm afraid)   Sad 

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Re: Long time problem possibly solved

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