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Author Topic: Flap Constrution  (Read 2503 times)

Offline Larry Fernandez

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Flap Constrution
« on: February 09, 2019, 06:10:33 PM »
When cutting flaps, would one prefer to have the grain parallel  to the trailing edge of the flap or the leading edge? Or does it make any difference at all?


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Offline Tim Wescott

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Re: Flap Constrution
« Reply #1 on: February 09, 2019, 07:08:16 PM »
I believe it'll be stronger with the grain running along the leading edge.  Way more important is to make sure it's C-grain balsa.
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Offline Brett Buck

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Re: Flap Constrution
« Reply #2 on: February 09, 2019, 07:16:08 PM »
When cutting flaps, would one prefer to have the grain parallel  to the trailing edge of the flap or the leading edge? Or does it make any difference at all?

  I always make it parallel to the trailing edge, but it doesn't make much if any difference.

    Brett

Offline Howard Rush

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Re: Flap Constrution
« Reply #3 on: February 09, 2019, 07:38:14 PM »
My guess would be that grain parallel to the hinge would be least likely to warp, but I would consult with the stress man before acting on that assumption.  Surely having C grain flaps would minimize unwanted flap camber. I wonder whether a skew in the grain direction would affect torsional stiffness symmetry. Of course critical to this application is the stiffness contribution of Mono Kote.
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Offline Dan McEntee

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Re: Flap Constrution
« Reply #4 on: February 09, 2019, 08:10:03 PM »
    It took me ten minutes to stop laughing enough to type this!! LL~ LL~ LL~ LL~

    If I have any doubts or questions if a piece of sheet balsa, such as a flap or all balsa flying surface, will be stiff enough to resist warping, I use a method I picked up out of old books and British designs, and that is I inlay a piece of harder balsa across the grain 90 degrees to the direction of the piece in question. If I'm tapering a flap, I get the flap almost finished, then do the cut out for the stiffener, install it, then trim it down and finish sand. One thing I have not tried is this method done is a sort of truss, geodetic or angular pattern with smaller strips to see if that makes any difference.. And I generally make the grain run parallel with the leading edge because I just never thought about doing it any other way, and use C-grain if I got it.
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Offline Mike Haverly

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Re: Flap Constrution
« Reply #5 on: February 09, 2019, 08:44:54 PM »
.  Surely having C grain flaps would minimize unwanted flap camber. I wonder whether a skew in the grain direction would affect torsional stiffness symmetry. Of course critical to this application is the stiffness contribution of Mono Kote.

Yuk,yuk,

Mike

Offline FLOYD CARTER

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Re: Flap Constrution
« Reply #6 on: February 09, 2019, 09:01:01 PM »
No matter how you cut it, it will probably not be stiff enough.  I make flaps from two sheets of medium 1/16" sheet, built up with a hard balsa L,.E.  and geodetic strips in the middle.  Finally, covered with light fiberglass, or else two layers of heavy silkspan.  Torsion resistance is in the outside layer, or monocoque outside.

Disclaimer:  I am not an aerodynamic engineer, so the real rocket scientists may disagree, and that's OK by me.
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Offline Paul Walker

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Re: Flap Constrution
« Reply #7 on: February 09, 2019, 09:49:15 PM »
 If one tapers the flap (and I know you do) you need the strength where it is the thinnest..as in the trailing edge.

I don't. 

My last 5 planes have no taper in thickness on the flaps.  Maybe it doesn't work because only 2 of those planes won the Nat's.

Stiffness wise there is almost no difference.

A good piece of wood is the key. It is amazing how stiff even a light piece if wood can be if its grain is good. The plane I am currently building has the stiffest flaps of any plane I have, yet at best is "B" grain and a 4.5 lb piece of 1/4 inch. Good wood is the key.

I also put 3 layers if carbon veil on it. That did help also, but was not as important as the wood selection.

But, if you cover with $coat, well, you are on your own.

Offline Larry Fernandez

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Re: Flap Constrution
« Reply #8 on: February 10, 2019, 02:16:23 AM »
Yuk,yuk,

Yuk yuk indeed.
Even though the the MonoKote gag has been run into the ground, one has to appreciate Howard’s back handed dig into the matter. Very subtle and very Brett like. Howard has elevated himself into the number two slot as the “Biggest Smartass in Stunt”  Brett should be thinking about elevating his game. Brett and Howard are in a league of their own. David, Paul, Eric and Antone are “Junior Varsity” and are a far cry from Brett and Howard’s skills.
Congratulations Howard, you smartass. With all due respect.

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Offline Larry Fernandez

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Re: Flap Constrution
« Reply #9 on: February 10, 2019, 02:27:50 AM »


But, if you cover with $coat, well, you are on your own.
[/quote]

Nice try Paul (I love you man) but the MonoKoke digs are so yesterday. If you want to break away from the “Junior Varsity” and run with the big dogs like Brett and Howard, your gonna have to up your game.

Larry,  Buttafucco Stunt Team.

Offline Peter in Fairfax, VA

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Re: Flap Constrution
« Reply #10 on: February 10, 2019, 04:55:37 AM »
I'm curious about what the effect of warped flaps will be, and this season is when I'm going to find out.

The stunter I have has built-up flaps that are warped.  By built-up, I mean that there is an outer frame work about 1/4" x 3/8", then "ribs" in a "geodetic" pattern.  They are covered with silkspan. By warped, I mean that if you lay a straight edge over the top of one of them, you can insert a drill bit in the daylight between the flap and the straight edge.  The size of the drill bit is somewhere about 1/16" to 3/32".  The other flap has the same degree of warp, but in the opposite direction, so that the straight edge is placed along the bottom to see the daylight.

This stunter is new to me.  My plan is as follows:

1.  See how it flies.
2.  Trim it for same wingtip to line angle right side up and inverted, if needed, by bending the flap horn.
3.  If unhappy, purchase some C-grain wood to make solid flaps. Probably grain along TE, though interested in this debate.

Being new to the forum, I do not get the MonoKote jokes.  So maybe I should use something like Super Coverite.

Peter

Offline John Lindberg

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Re: Flap Constrution
« Reply #11 on: February 10, 2019, 07:09:59 AM »
Sig sells C-grain balsa, medium weight, I guess. The widest they sell is 3 inch. Not bad stuff, I believe!  H^^

Offline Paul Walker

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Re: Flap Constrution
« Reply #12 on: February 10, 2019, 09:06:49 AM »
Sig sells C-grain balsa, medium weight, I guess. The widest they sell is 3 inch. Not bad stuff, I believe!  H^^

Unfortunately they don't sell light stuff anymore.

Good luck.

Offline Paul Walker

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Re: Flap Constrution
« Reply #13 on: February 10, 2019, 09:17:52 AM »

Being new to the forum, I do not get the MonoKote jokes.  So maybe I should use something like Coverite.

Peter
[/quote]


Peter, Larry F builds beautiful planes with Monokoat, but refuses to use traditional silkspan and dope. If you ever see a picture of his PT-19, you will see beautiful Monokoat work.






OK, just kidding. Larry really does nice work with silkspan and dope, so much so that it looks like Monokoat when done, it is so nice. This has been an ongoing poke for years now, but Larry being the KING of smart a**es, deserves our "admiration".


P.S.  your issue with flaps is part of the reason that I make mine removable. I would try to get them straight before you flew it.  They will at best make it much harder to get the plane trimmed properly.

Good luck on your new plane.

Offline Mike Haverly

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Re: Flap Constrution
« Reply #14 on: February 10, 2019, 10:29:36 AM »
My friend and I have been working on trimming his new airplane.  His had the same issue, warped flaps.  They are not removable but still can be straightened.  Boiling hot water, a few bath towels and some patience is all it takes.  You might be surprised how much of a twist you can put in them.   Paul is right, usually is, straighten them before you put a lot time in trimming and risking a crash.
Mike

Offline Guy Markham

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Re: Flap Constrution
« Reply #15 on: February 10, 2019, 12:22:26 PM »
My guess would be that grain parallel to the hinge would be least likely to warp, but I would consult with the stress man before acting on that assumption.  Surely having C grain flaps would minimize unwanted flap camber. I wonder whether a skew in the grain direction would affect torsional stiffness symmetry. Of course critical to this application is the stiffness contribution of Mono Kote.
 
Yesterday and today Howard just goes outside and freezes his flaps to the correct shape  LL~ LL~ LL~
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Offline Brett Buck

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Re: Flap Constrution
« Reply #16 on: February 10, 2019, 12:23:19 PM »
Yuk yuk indeed.
Even though the the MonoKote gag has been run into the ground, one has to appreciate Howard’s back handed dig into the matter. Very subtle and very Brett like. Howard has elevated himself into the number two slot as the “Biggest Smartass in Stunt”  Brett should be thinking about elevating his game. Brett and Howard are in a league of their own. David, Paul, Eric and Antone are “Junior Varsity” and are a far cry from Brett and Howard’s skills.
Congratulations Howard, you smartass. With all due respect.

     I would agree with your assessments, right down the line. Howard is the only real contender as far as I am concerned. Controls people are always the smartest people in any room and they towards being "on the spectrum", which seems to help. Paul calls Howard "Sheldon", which is cruel, raising his stock considerably, in my opinion. Some people, as far off the spectrum as you can get, like Ted, consider "smart-ass" a perjorative or negative characteristic.

    Too far into the spectrum, and you get the late Bob Baron - generally humorless, and I bet he spent a lot of time memorizing train schedules. 

     The monokote thing has been completely run into the ground, and using that smacks of having nothing else to use. When you are stealing material from Antone and Eric, you undermine your candidacy (like Paul does above). And then he commits the cardinal sin of indirectly apologizing for it.

   Of the likely other contenders, David certainly wins on volume, although the crudity and lack of sophistication works against him. Paul is somewhat better at it, with a hint of occasional brilliance, but likely restricted by his profession. Mechanical/structures engineers (essentially, blacksmiths with computers (and not even real computers, they use Excel a lot , for God's sake...) ) tend to descend from the same place as orthopedic surgeons, where any subtle debates are ultimately solved by either heating something, cutting something, or hitting something with a big hammer. In high school, controls engineers and brain surgeons were in the chess club,  mechanical engineers were on the football team. Paul is not nearly as affected by this as many others, but lack of smart-ass challenges in his professional life have not given him the opportunities to develop the true "smart-ass"/"maladjusted and just trying to cope" attitude that people like Howard and I use as a survival skill.

   David was apparently nearly insufferable when he was a kid, so the fact that he is barely tolerable now is hardly a surprise. What works against him is his ancestry and his mentoring. Bill (David Senior) and (Ted). Ted considers being a smart-ass a negative thing, so does Shareen. You have no idea how far I dial it back.  Bill didn't even grasp the concept of being a wise-guy. David tries extra-hard, and has developed some superficial nerd characteristics (don't ask him about Star Wars OR Star Trek, or you will be very sorry). But on close examination, he belies this superficial nerdiness by getting the details wrong. No true nerd would forget the name of William Shatner's stunt double Fred Lubbins, for example. I don't even care, and I remember it, because I can't stop. He was surprised when I guessed the end of Star Wars Rogue One after about 15 minutes in, how could you not, and I was half-asleep. Every smart-ass comment David makes is like a brick through a plate-glass window. Crude.
 
   Paul probably outranks David, just for subtlety and quality, although clearly not in the rank with Howard and I.

    Some of the others on your list deserve consideration above Paul and David. Uncle Jimby is a contender, too. One not on your list (since you haven't met him) and an acknowledged master is one Mr. Billy Werwage. As far as quality and subtlety, I think Howard has him beat, but you can't deny a lifetime of achievement. Larry Renger would be a contender, being firmly planted on The Spectrum, perhaps about one step too far, because I suspect he doesn't even realize it.

   A lot of the other guys, just don't belong in the discussion. Anyone might have their one "moment", like Eric and Antone, but that's far from using being a smart-ass as a substitute for an otherwise-absent real personality like Howard and I.

    Brett

   


Offline Paul Walker

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Re: Flap Constrution
« Reply #17 on: February 10, 2019, 03:41:27 PM »
Me thinks I have doled out the special knick name prematurely.

Offline Target

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Re: Flap Constrution
« Reply #18 on: February 11, 2019, 11:23:13 AM »
If one tapers the flap (and I know you do) you need the strength where it is the thinnest..as in the trailing edge.

I don't. 

My last 5 planes have no taper in thickness on the flaps.  Maybe it doesn't work because only 2 of those planes won the Nat's.


What shape is on the rear end of the flap? Is it completely squared off??
Thanks.

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Target
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Offline Paul Walker

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Re: Flap Constrution
« Reply #19 on: February 11, 2019, 12:23:14 PM »
What shape is on the rear end of the flap? Is it completely squared off??
Thanks.

R,
Target


Yes, just squared off. The rectangular cross section adds torsional stiffness compared to a tapered section. I have seen no downside to this configuration. No change in stick force, no change in effectivity and much easier to build! Mine are 1/4" thick, thus I can't comment on 3/8 or thicker configurations.

Offline Target

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Re: Flap Constrution
« Reply #20 on: February 11, 2019, 03:13:24 PM »
Thanks. We newbies like it when something is easy AND good.

R,
Target
Regards,
Chris
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Offline Howard Rush

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Re: Flap Constrution
« Reply #21 on: February 11, 2019, 03:37:12 PM »
Mine are 1/4" thick, thus I can't comment on 3/8 or thicker configurations.

I can.

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Offline Paul Walker

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Offline Target

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Re: Flap Constrution
« Reply #23 on: February 11, 2019, 04:29:53 PM »
Mostly comical!
Regards,
Chris
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Offline Brett Buck

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Re: Flap Constrution
« Reply #24 on: February 11, 2019, 08:45:54 PM »
Me thinks I have doled out the special knick name prematurely.

   Oh, I think you were mostly right on that one, although I will admit that it's a debatable point.

     Brett


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