Scallops on wing Q..

[Joe Yau]

Just wondering if fairly deep scallops formed on a geodetic type wing would effects flight characteristics?

Thanks in advance

 

[Randy Ryan]

Well I have serious doubt it has any appreciable effect, in free flight we (some of us anyway) referred to that as creating an "average" airfoil section. Geo or conventional, the actual section of the airfoil lies somewhere between the rib camber line and the drawn down curve of the covering. If you lay it out you'll find it really quite minimal.

[Joe Yau]

Just curious, but how did they form?  Is that a plastic (ie monocote) cover or just tight shiny doped silkspan, etc.??

I don't know exactly how it got that way..  (didn't build this one)   I believe it's doped/polyspan.  This plane does have stability issues in level flights.   

[Randy Powell]

Built in turbulators.

[GregArdill]

This plane does have stability issues in level flights.   

The next question is, what is causing the instability?

Can anyone be sure it is because of the shape induced by the covering?

G

[George Hostler]

I don't know exactly how it got that way..  (didn't build this one)   I believe it's doped/polyspan.  This plane does have stability issues in level flights.

Usually things like that happens when the builder runs the grain of the covering material chord-wise, instead of span-wise. When you say it's unstable in level flight, what is happening?

[Gerald Arana]

What George H. said. 

GA

[Joe Yau]

Usually things like that happens when the builder runs the grain of the covering material chord-wise, instead of span-wise. When you say it's unstable in level flight, what is happening?

It just wont loc-on level flight both right side up & inverted.. as it would wander (not hunting), sometimes is acceptable and other times could be a handful.   but goes away in the maneuver.  (variies with conditions of course) It's like it has a mind of its own.. very tiring to fly at times.  But not sure if this has anything to do with it.

[John Stiles]

I'm thinking there may be some free play in the control system somewhere, or a linkage maybe flexing.

[RC Storick]

Built in turbulators.

Except not as bumpy as rat droppings.

[John Cralley]

Maybe tail heavy. Add a little weight to the nose and see if that cures it.

[EddyR]

I think it has the effect of reducing the airfoil and changing its profile. Why use a good airfoil and then reduce it to that . Looks like some ringmasters I have seen.
Ed

[Steve Helmick]

This is the Chris-Craft Saturn you fly with the .40VF? Move the LO's back 1/8" at a time, while leaving everything else alone.  Also...what is your handle spacing? Hardpoint handle?   Steve

Edit: One thing I've noticed is that combat fliers often don't fly level very accurately/smoothly. My conclusion is that they are not concentrating on their plane, but sometimes looking for their opponent.

[Jim Kraft]

Seal the hinge lines if it has not been done already.

[Joe Yau]

This is the Chris-Craft Saturn you fly with the .40VF? Move the LO's back 1/8" at a time, while leaving everything else alone.  Also...what is your handle spacing? Hardpoint handle?   Steve

Edit: One thing I've noticed is that combat fliers often don't fly level very accurately/smoothly. My conclusion is that they are not concentrating on their plane, but sometimes looking for their opponent.

Steve, I have tried everything on this plane including LO & handle etc.. It's not it.  I'm more interested in finding out if the scallops has an effect or not on the plane at this point.  My other planes loc-on just fine.. well, you saw my Pathfinder last weekend. 

[Steve Helmick]

Steve, I have tried everything on this plane including LO & handle etc.. It's not it.  I'm more interested in finding out if the scallops has an effect or not on the plane at this point.  My other planes loc-on just fine.. well, you saw my Pathfinder last weekend.  

So, what's the line spacing at the handle, and is it a hardpoint?    Steve

Edit: As many people have built these Geo-Rib wings, I doubt if that's the problem, especially the caliber of fliers who use 'em.

Edit Again: Bring it on down to "The Scobee" on August 10-11 (check me!) and get somebody to fly it. I like to get PW to fly somebody's airplane just before his official! 

[George]

Except not as bumpy as rat droppings.

But those are turdbulators... 

George

[Joe Yau]

So, what's the line spacing at the handle, and is it a hardpoint?     Steve

It is a Ted's hardpoint Handle with spacing at 3.75". 

As many people have built these Geo-Rib wings, I doubt if that's the problem, especially the caliber of fliers who use 'em.

I never said the Geo structure is the problem..  the original question was if deep scallops from the covering would effects flight performance. 

[Joe Yau]

Seal the hinge lines if it has not been done already.

The hinge line are sealed. 

[john e. holliday]

The covering as I see it in the pictures should not hurt the flying performance of the plane.   I have had several that look like that until I learned that iron on coverings have a grain/shrink direction to them.   How many know that the shrinkage is along the length of a role of iron on coverings.   Silkspan and poly-span have a grain to them that should run span wise other wise you get what you see in the pictures.   Silk and nylon have to be pulled more span wise than chord wise also.   As far as the plane wandering in lever flight, in some cases it was stiff controls for me.   Also if things are not lined up with each other loose controls will be the culprit.   Most of all and I have done it,  pilot not holding his hand still while turning/walking in the center of the circle.  Wish I could see the plane in person so I could really tell you.   But, as stated before, get someone else to look at the plane in person and/or fly it.

[Joe Yau]

As far as the plane wandering in lever flight, in some cases it was stiff controls for me.   Also if things are not lined up with each other loose controls will be the culprit.   Most of all and I have done it,  pilot not holding his hand still while turning/walking in the center of the circle.  Wish I could see the plane in person so I could really tell you.   But, as stated before, get someone else to look at the plane in person and/or fly it.

Hi John,  Every aspect has pretty much been looked at in the last 4yrs  (CG as per plan to more nose heavy vs tail heavy, LO, elev PR,engine dn trust, pos ins on stab, more flaps vs less flaps, etc, etc)  Would be great if someone like Paul would take it for a spin and see what his thoughts are. and hopefully its not one of those odd days the plane decides to flys better.  

Here's an old clip of the plane at the 2009 WCSC contest.  Back then I had a 4-stroke on it, and it used to hunt at 4.8/lap and was manageable at 5.2 or so.    and after numerous hours spend trimming to cure the hunting issue, it left with inverted flight would not loc-on.   you could see the inverted flight in the video, as I tried to fly 5', it would drop to 2' at times. so I had to fly high.

 

[John Stiles]

Can't tell a whole lot from the clip, Joe; but looks to me like it flies real nice....either that or the
Pilot is an expert at correcting for little variations.

[Joe Yau]

Can't tell a whole lot from the clip, Joe; but looks to me like it flies real nice....either that or the
Pilot is an expert at correcting for little variations.

It was just the inverted flight that had an issue.  It was nerve racking trying to get it down to 5', then on the 2-3rd lap it wandered down to 2'     the rest of the flight were o.k.   

[Steve Helmick]

"It is a Ted's hardpoint Handle with spacing at 3.75"."

My feeling is that's a lot of handle spacing, but I don't know how quick the controls are setup. I would suggest cutting the spacing to 3" or 3.25" and just fly upright and inverted with it. Another thing to look at would be your neutral setting...that can do it very easily.   

The considerable turbulence off the trees upwind makes trimming at Rice Mill Rd. site only do-able early AM, IMO. As in, "The crack of dawn". I got there before 7am and it was too windy and turbulent to trim anything except prop testing.  Steve

[Joe Yau]

"It is a Ted's hardpoint Handle with spacing at 3.75"."

My feeling is that's a lot of handle spacing, but I don't know how quick the controls are setup. I would suggest cutting the spacing to 3" or 3.25" and just fly upright and inverted with it. Another thing to look at would be your neutral setting...that can do it very easily.   

Steve, I have tried 3" spacing and it was way worst..  and even 3.5" was still pretty bad.  as it wanders even more and I couldn't exit the triangle and a few other maneuvers cleanly without a bobble or two.   Actually 3.75" is as good as it gets at this point, or maybe even slightly wider might help. but I might over control some of the maneuvers.

The considerable turbulence off the trees upwind makes trimming at Rice Mill Rd. site only do-able early AM, IMO. As in, "The crack of dawn". I got there before 7am and it was too windy and turbulent to trim anything except prop testing.  Steve

Actually, no one is suppose to be flying before 9:00am at Rice Mill unless you're flying electric.  Otherwise I would of been there early Sunday morning.  I usually do my testing and trimming at the Coquitlam field in the week days.

[Steve Helmick]

With the normal turbulence from the corner of the field, you're never going to have perfect level laps at the Rice Mill Rd. site, IMO.
Look at your neutral setting or pour a new pilot's circle pad.  Steve

[John Stiles]

Might try a different set of lines/handle I'm sorta bad about over-controlling while inverted...it's a mental defect no doubt....but like Steve said, it should get a little better with closer spacing, not worse. I tend to panic a little with my favorite planes...I know this as a fact, because I won't even attempt inverted flight on brand new planes for at least 5 or 6 flights. I'm gonna hafta quit drinking strong caffeinated coffee

[john e. holliday]

Watching the video, it looks to me  like you are following the bushes in the background for level flight.  Another question I have, do you have another plane to fly to see if it is the plane or the pilot.   That one inverted lap looked like you relaxed too much.   Might try inverted with the plane and see if stays level at where you start the inverted level flight.   As stated it could be handle setting.  Borrow another plane if you can and try it.

[Joe Yau]

With the normal turbulence from the corner of the field, you're never going to have perfect level laps at the Rice Mill Rd. site, IMO.
Look at your neutral setting or pour a new pilot's circle pad.   Steve

That's quite true..  But the thing is all my other planes flys just fine like my  .46LA Pathfinder, 4-stroke Score, Evo .36 Primary Force, and my Stalker .61RE Magnum Plus.  My Score had some tracking issue at first but with some adjustment on flap vs elev adj & 1/2 turn down on the elev PR  then it loc-on.  and the Flapless Primary Force  tracks unbelievablely well.. loc-on tracks both ways..  I could fly 2'  upright & inverted.  and also Keith ol' Magnum Plus was very solid both ways as well.    does that not rule out the condition & handle spacing or me?

Might try a different set of lines/handle I'm sorta bad about over-controlling while inverted...it's a mental defect no doubt....but like Steve said, it should get a little better with closer spacing, not worse. I tend to panic a little with my favorite planes...I know this as a fact, because I won't even attempt inverted flight on brand new planes for at least 5 or 6 flights. I'm gonna hafta quit drinking strong caffeinated coffee

The handle spacing were ruled out long ago as it made it hard to fly precise. as mentioned above its not it.  I could have a few strong Starbuck's coffees and no problem flying level flights with my other planes.. I might rush the maneuvers a bit, or hit the corner harder then normal..  but if the plane is dialed-in it shouldn't be a problem.

Watching the video, it looks to me  like you are following the bushes in the background for level flight.  Another question I have, do you have another plane to fly to see if it is the plane or the pilot.   That one inverted lap looked like you relaxed too much.   Might try inverted with the plane and see if stays level at where you start the inverted level flight.   As stated it could be handle setting.  Borrow another plane if you can and try it.

As mentioned above in reply #16 & 22, its been done. and the next thing I did was fly my other planes.. in fact I often flew back to back flights with my other planes in numerous session to isolate this problem.  I have a feeling it's the wing at this point.

On the inverted flight after the 3rd lap I flew high, as if I bring it any lower, it'll wander down to 2'  which is not a good idea for the official flight.

[Joe Yau]

Thanks all for the replies!  

Looks like I'll have to do some more experiment on the wing...

[Steve Helmick]

Have you tried adding a sharp edge radius to the stabalizer (like Alan did on his Gypsy)? I still think it's possible your handle neutral is not perfect...and it needs to be!  Steve

[Joe Yau]

Have you tried adding a sharp edge radius to the stabalizer (like Alan did on his Gypsy)? I still think it's possible your handle neutral is not perfect...and it needs to be!  Steve

Yes, I have a small carbon rod on the LE of the stab.  It did helped a bit like 2%. (it changed the turn characteristic slightly but tracks better level.    I also tried VG on the stab twice, and didn't like it at all.. I removed them already.   I'll check the handle neutral next time out.  

[Steve Helmick]

Joe...IMO, you probably can't just "check" the neutral adjustment. I think you need to adjust it (but be able to put it back where it was) one way and maybe then the other. Regardless of what you do, be prepared to put it back as it was!

Some years ago, I was watching a very experienced flier, and his upright level flight was diving, not grooving. When it got to 3', he yanked on some up and got back to 5', then it dove again, and again, about 3 times per lap. Inverted, it was "grooving" at 7'-8', losing him lots of points. I suggested that his neutral was off, and causing that, but he wouldn't adjust it, and did the same thing the next official. Oh, well! 

My story was with the SV-11 from several years ago. It was ok, generally, but my takeoffs were too sudden and too steep. Mike and Pete told me to adjust my neutral, but I dragged my feet. Finally, I changed one clip, just 1/32" and fixed the steep takeoff. Yes, I was shocked, but I was a happy camper.  I hope you have a similar result! Steve

[john e. holliday]

Steve is right about adjusting the neutral on  the handle for your flying.  I noticed on several planes I have that I could not get the laps the same altitude upright and inverted.   Once I figured out that I was flying high inverted I changed the neutral on the handle.   What difference it made in getting the invert down where it belongs.  For some reason never had trouble with upright level laps even after changing the neutral for inverted.