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Author Topic: Tab on the outside flap  (Read 899 times)

Offline Matt Piatkowski

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Tab on the outside flap
« on: June 15, 2021, 03:20:39 PM »
Hello,
Th left wing is 1" longer than the right wing. Flaps have the same shape and length.
Total wings area with flaps:715 in.^2.
Do I need the tab on the outside flap TE to avoid flight dynamics disturbances in certain maneuvers?

If yes: what size of this tab to start with and where to attach it w/r to the outside flap end?
Thanks,
M

Offline Dan McEntee

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Re: Tab on the outside flap
« Reply #1 on: June 15, 2021, 04:30:16 PM »
Hello,
Th left wing is 1" longer than the right wing. Flaps have the same shape and length.
Total wings area with flaps:715 in.^2.
Do I need the tab on the outside flap TE to avoid flight dynamics disturbances in certain maneuvers?

If yes: what size of this tab to start with and where to attach it w/r to the outside flap end?
Thanks,
M


   Like Ty mentioned, you might add a tab to the outboard wing to counter a warp, but not to the flap. You need to fly the model first, get tip weight finalized and see if it drops the outboard wing in inside and outside corners. If it flies fine, no tab needed. Some used to design the outboard flap with more area so they could carry more tip weight for better line tension. The extra area was supposed to help keep that wing level in the corners. If more flap area was needed, thne the tab was added.  Not done so much these days, I think.
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Offline De Hill

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Re: Tab on the outside flap
« Reply #2 on: June 15, 2021, 04:34:35 PM »
A tab attached to the outside flap was also called a wart.
De Hill

Offline Leonard Bourel

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Re: Tab on the outside flap
« Reply #3 on: June 15, 2021, 05:35:00 PM »
Hey Matt are you sure you need a trim tab ? When you fly the model what is the wing doing in level flt both right side up and inverted?  If when you are flying both ways the wing is up you need more tip weight .If it is down both ways you need less tip weight If the outboard tip is up when flying upright and down inverted you need a trim tab up on the outboard wing flap and if the outboard tip is down in level flt when upright and up when inverted you need a trim tab down on the outboard tip I usually make these tabs about an inch wide and bend them in the center and temp tape them to the flap until I get the size I want  and the amount of bend I want  so that the wing is perfectly level both ways It really helps to get someone with a keen eye to check this for you while you are flying Many will tell you that the plane looks level both ways but not everyone can see it Best Len 

Offline Ken Culbertson

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Re: Tab on the outside flap
« Reply #4 on: June 15, 2021, 06:21:16 PM »
I think the tab Matt is referring to is the one you would attach to the outboard flap to combat hinging in corners.  I have found that about 2-4 sq" of extra flap on the outboard is about right for a 60-63" wing.  My experience is that adding area to the outboard is not as effective as the concentrated area from a tab near the end of the flap.  Whatever you do you are putting a band-aid on something else wrong with the design or the control ratios.

Ken
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Offline Howard Rush

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Re: Tab on the outside flap
« Reply #5 on: June 15, 2021, 06:50:49 PM »
Matt is correct about flight dynamics disturbances. The effect is too subtle for me. Its at the Brett Buck trimming level.
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Offline Matt Piatkowski

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Re: Tab on the outside flap
« Reply #6 on: June 15, 2021, 09:24:16 PM »
The plane is in the final stage of delicate trimming.
I have already adjusted the angles of flaps to counteract a minute warp in the wing (60.75" span).

Len,
This angular adjustment was very small and I had to make six flights, mostly level, and level inverted at 5 feet for the person watching the plane to finally say "outside tip down in level flight and up in level inverted but I can barely notice this". We were lucky with the wind - it was early in the morning and almost no wind so all that was possible finally to see. I was flying on the previous day with the wind 5-6 knots and there was no way for anybody to see this.

Ken,
After the flaps angular adjustment, I started flying selected maneuvers. Specifically: squares, triangles, horizontal eights, and my favorite - the hourglass. In some of the 120 and 90-degrees corners, I have noticed a very slight tendency to hinge. Like you pointed out, this is the main reason I raised the question about the tab on the TE of the outboard flap.

I have already added such a tab but I made only three flights with it and the wind was 8 knots and a bit gusty so...I have to wait for ideal conditions to see the difference, if any.

Howard,
It may be also too subtle for me. If I cannot see and feel the difference in windless weather, I will keep changing the tab's position and size until I find improvement.

Thank you for your thoughts and comments.

P.S: good luck to those who will compete in Muncie. I was planning to fly in the advanced group but Canadians are still stuck on the north of the border, probably until June 21.

Online PJ Rowland

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Re: Tab on the outside flap
« Reply #7 on: June 27, 2021, 03:40:47 PM »
This is "easy" to understand...

Inboard wing is 1" longer than the outboard wing.
Flaps have the same shape and length.

(Which automatically gives you the lift asymmetry, inboard wing produced more lift than the outboard seen as a roll with some yaw)



Do I need the tab on the outside flap TE to avoid flight dynamics disturbances in certain maneuvers?

THE main thing you need to consider, is the stunt airframe weights ALOT more during a turn. You need to balance that lift requirement with a more effective solution.

If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them. - Bruce Lee.

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 I Yearn for a world where chickens can cross the road without having their motives questioned.

Offline Ted Fancher

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Re: Tab on the outside flap
« Reply #8 on: June 27, 2021, 06:13:41 PM »
Afraid I probably have to take credit/blame for the "warts" on outboard wings/flaps.  Most of my flapped ships of my own design have ended up with them...albeit added as part of initial flight trim...not from original design/construction.  The only flapped ship hanging around the house "without" a wart is the Veco Chief I built for a long ago VSC...a ship that flew beautifully from the get go. I suspect, in part because the Chief had the then common two or so inch asymmetry  rather than the now nearly ubiquitous 1" or even equal span.

The ships that sport the warts were built with then modern wing asymmetry...i.e. less inboard/outboard span difference than common in the designs of the "50s and 60s".  To the best of my recollection the "warts" were added to those ships (four of which won Walker Trophy possession for a year each) due to adding more than anticipated tip weight to get wings level in level flight and yet add a little lift when deflected as the ships would roll slightly but noticeably in hard corners. There was likely a better solution but since this one seemed to do the job I stuck with it.  The bad news only that they looked dopey stuck out there as only once did I take the effort to make the wart appear part of the original production so it didn't look "added so as to confuse the competition"!

In response to Matt's query in his original post I would only add "possibly".  The asymmetry on my "warted" ships (all ~60" spans) was about an inch as well.

I must add, however...and it's a bit embarrassing...that none of my close compatriots and few if any of the dreaded East of the Pacific Ocean shore opposition ever seemed to find it necessary to do so.

If Matt should decide it is worth doing "just in case" here's a brief TLAR I appear to have used on the ships still on the wall/ceiling at Chez Fancher, the 1982 Nats winning Intimidation and the 1995 Champion Great Expectation were both ~2.5" X 5/8" or so (the Great Expectation had a recessed slot in the flap to allow the wart to be slid in or out of the trailing edge as necessary/wagged during trim flights (Alas, this ship was later refinished in the Pond Scum Purple colors and the tab then affixed permanently (perhaps of interest this ship was renamed the Final Edition and won the Nats in (IIRC) 2000.  IOW, the wart didn't seem to do any harm to the ships but I can't declare positively that it is any sort of "must" for any predictable trim problem.

Matt., although I don't think adding a wart to your new ship will cause it to disintegrate or anything, neither do I believe it will substantially enhance your competitive outcomes.  If you're getting a little roll action in corners you can tape a temporary wart to the outboard flap and decide for yourself.  the only harm it can cause is if you're in the running for the Concours and you've glommed the thing on "ugly"--like most of mine are--you probably won't win the big prop.

Ted 

Offline Matt Colan

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Re: Tab on the outside flap
« Reply #9 on: June 27, 2021, 07:24:47 PM »
Hi Ted, if your plane was rolling before the wart, would it roll in at the top of an outside square just a little bit? Or roll elsewhere?
Matt Colan

Offline Ken Culbertson

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Re: Tab on the outside flap
« Reply #10 on: June 27, 2021, 08:30:15 PM »
Afraid I probably have to take credit/blame for the "warts" on outboard wings/flaps.  Most of my flapped ships of my own design have ended up with them...albeit added as part of initial flight trim...not from original design/construction.  The only flapped ship hanging around the house "without" a wart is the Veco Chief I built for a long ago VSC...a ship that flew beautifully from the get go. I suspect, in part because the Chief had the then common two or so inch asymmetry  rather than the now nearly ubiquitous 1" or even equal span.

The ships that sport the warts were built with then modern wing asymmetry...i.e. less inboard/outboard span difference than common in the designs of the "50s and 60s".  To the best of my recollection the "warts" were added to those ships (four of which won Walker Trophy possession for a year each) due to adding more than anticipated tip weight to get wings level in level flight and yet add a little lift when deflected as the ships would roll slightly but noticeably in hard corners. There was likely a better solution but since this one seemed to do the job I stuck with it.  The bad news only that they looked dopey stuck out there as only once did I take the effort to make the wart appear part of the original production so it didn't look "added so as to confuse the competition"!

In response to Matt's query in his original post I would only add "possibly".  The asymmetry on my "warted" ships (all ~60" spans) was about an inch as well.

I must add, however...and it's a bit embarrassing...that none of my close compatriots and few if any of the dreaded East of the Pacific Ocean shore opposition ever seemed to find it necessary to do so.

If Matt should decide it is worth doing "just in case" here's a brief TLAR I appear to have used on the ships still on the wall/ceiling at Chez Fancher, the 1982 Nats winning Intimidation and the 1995 Champion Great Expectation were both ~2.5" X 5/8" or so (the Great Expectation had a recessed slot in the flap to allow the wart to be slid in or out of the trailing edge as necessary/wagged during trim flights (Alas, this ship was later refinished in the Pond Scum Purple colors and the tab then affixed permanently (perhaps of interest this ship was renamed the Final Edition and won the Nats in (IIRC) 2000.  IOW, the wart didn't seem to do any harm to the ships but I can't declare positively that it is any sort of "must" for any predictable trim problem.

Matt., although I don't think adding a wart to your new ship will cause it to disintegrate or anything, neither do I believe it will substantially enhance your competitive outcomes.  If you're getting a little roll action in corners you can tape a temporary wart to the outboard flap and decide for yourself.  the only harm it can cause is if you're in the running for the Concours and you've glommed the thing on "ugly"--like most of mine are--you probably won't win the big prop.

Ted
https://www.bing.com/images/search?view=detailV2&ccid=1tAmT2LA&id=96AF74103CCD504B1793982A10FCA133EA9BDF51&thid=OIP.1tAmT2LAY1HFnMhQX6MOagHaHa&mediaurl=https%3a%2f%2fimages-na.ssl-images-amazon.com%2fimages%2fI%2f610U5zc6uOL.jpg&cdnurl=https%3a%2f%2fth.bing.com%2fth%2fid%2fRd6d0264f62c06351c59cc8505fa30e6a%3frik%3dUd%252bb6jOh%252fBAqmA%26pid%3dImgRaw&exph=1500&expw=1500&q=wart+remover&simid=608008416784417860&ck=F646A930F9585CDBB949CAF7A2F6C480&selectedIndex=50&FORM=IRPRST&ajaxhist=0&ajaxserp=0

Have you tries this?

Ken
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Offline Ted Fancher

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Re: Tab on the outside flap
« Reply #11 on: June 27, 2021, 10:22:20 PM »
Hi Ted, if your plane was rolling before the wart, would it roll in at the top of an outside square just a little bit? Or roll elsewhere?

Not to the best of my memory, Matt.  Remember, outside squares require down elevator and "up" flaps which, if anything, you would expect to roll the ship away on those outside corners.  No, my intention in utilizing them was to keep the wing "in line with" the lines.

Again, the most I'm able/willing to say about them is that they seemed to resolve what I felt was a comparatively minor trim issue, enough so that I utilized them on several ultimately competitively successful stunt ships.  I'm unwilling to say that everyone should have a wart on the outboard flap...but that if they have some roll issues in corners it is worth experimenting with...a long with tip weight, leadout location with respect to the CG, etc.

Ted


Offline Dave_Trible

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Re: Tab on the outside flap
« Reply #13 on: June 28, 2021, 04:52:50 AM »
In years past I usually found myself adding the wart.  Then I began making the outboard wing flap 3/32" wider in chord as standard practice when building and eliminated the tab. 

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Offline Ken Culbertson

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Re: Tab on the outside flap
« Reply #14 on: June 28, 2021, 06:39:00 AM »
In years past I usually found myself adding the wart.  Then I began making the outboard wing flap 3/32" wider in chord as standard practice when building and eliminated the tab. 

Dave
That equates to about a 5/8 x 4" tab.  I used 1/8" but found the extra chord less effective than the tab.  I have also tried making the inboard flap shorter in span which didn't do much at all.  I can only speculate but I think it has something to do with the tab's proximity to the tip weight or delaying tip stall.  The "why" some ships need them and some don't is above my pay grade but I do know that they work when all else fails.  For instance, both of the ships I have equipped with a CAM rudder did not need the tab but that could have been for other reasons.

Ken
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Offline Ken Culbertson

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Re: Tab on the outside flap
« Reply #15 on: June 28, 2021, 06:40:06 AM »
That equates to about a 5/8 x 4" tab.  I used 1/8" but found the extra chord less effective than the tab.  I have also tried making the inboard flap shorter in span which didn't do much at all.  I can only speculate but I think it has something to do with the tab's proximity to the tip weight or delaying tip stall.  The "why" some ships need them and some don't is above my pay grade but I do know that they work when all else fails.  For instance, both of the ships I equipped with a CAM rudder did not need the tab but that could have been for other reasons.

Ken
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USAF 1968-1974 TAC


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