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General control line discussion => Open Forum => Topic started by: Casey on December 24, 2018, 02:29:19 AM

Title: Number of Hinges to attach Flaps
Post by: Casey on December 24, 2018, 02:29:19 AM
My inboard flap is 23.6 inches. What is the minimum number of hinges I should use to attach it to the wing trailing edge?
Title: Re: Number of Hinges to attach Flaps
Post by: Perry Rose on December 24, 2018, 05:56:23 AM
3 minimum. 4 is better.
Title: Re: Number of Hinges to attach Flaps
Post by: peabody on December 24, 2018, 07:17:23 AM
Windy recommended four....two close to the outboard end.....

Title: Re: Number of Hinges to attach Flaps
Post by: john e. holliday on December 24, 2018, 08:54:59 AM
What plane.   But me I do cloth hinges all along the edges.  Seals hinge line and easy to do. D>K
Title: Re: Number of Hinges to attach Flaps
Post by: Mike Griffin on December 24, 2018, 10:38:15 AM
I do what Doc does.

Mike
Title: Re: Number of Hinges to attach Flaps
Post by: Dave Hull on December 24, 2018, 12:07:26 PM
I never understood the logic of a pair of plastic hinges at the tip of the flap. Anyone heard a reason that they believe?

Dave
Title: Re: Number of Hinges to attach Flaps
Post by: Randy Cuberly on December 24, 2018, 12:08:07 PM
I Believe in using a hinge about every 4 inches apart and two hinges close together at the tip near the end of the flap.

My reasoning for this is that under load when maneuvering, especially in hard corners,  the flap can flex a small amount between the hinges and actually slightly stiffen the movement at the hinge and cause slight stiffening of the controls at a critical time.  It's only a theory of course but a sound one, I believe.  Also with less load on each hinge there will be less chance of any hinge failure.

Two are used together at the tip because that is the most likely place for destructive flutter to develop if the flap is not very secure!

Randy Cuberly
Title: Re: Number of Hinges to attach Flaps
Post by: EddyR on December 24, 2018, 03:34:07 PM
The reason is simple . Many of us who have flown for many years have seen single hinges fail at the flap end. Many years ago most went to putting two hinges at the tip to stop failure.  There must be a lot more loads at the tip than one would think.
Ed
Title: Re: Number of Hinges to attach Flaps
Post by: Casey on December 25, 2018, 06:38:48 AM
I am building a Genesis 46 Mark III. Powerplant is an ABC Super Tigre 51
Title: Re: Number of Hinges to attach Flaps
Post by: Dan McEntee on December 25, 2018, 10:20:49 AM
I never understood the logic of a pair of plastic hinges at the tip of the flap. Anyone heard a reason that they believe?

Dave

   If you have ever witnessed a flap flutter and fall off, thus causing a crash, the you would understand why.  You probably would never see the flutter, but you may hear it.  Not very common but it does happen. Sparky lost one of his really nice Thunderbolts to this happening, and is the reason why he came up with the hinge that he uses now. I'm sure he has a video on it that you could find.
   MERRY CHRISTMAS and HAPPY NEW YEAR!
   Dan McEntee
Title: Re: Number of Hinges to attach Flaps
Post by: john e. holliday on December 25, 2018, 06:59:30 PM
Does Sparky still make his hinges? D>K
Title: Re: Number of Hinges to attach Flaps
Post by: Target on December 26, 2018, 05:30:54 AM
Does Sparky still make his hinges? D>K
He said no when i asked him about a year ago. He makes them for his planes but no longer to sell.
Title: Re: Number of Hinges to attach Flaps
Post by: Steve Fitton on December 26, 2018, 10:40:28 AM
I used 5 hinges on my SV sized planes and just went to six hinges on the latest one.
Title: Re: Number of Hinges to attach Flaps
Post by: kevin king on December 27, 2018, 06:39:31 AM
I've never seen a flap or anything else let go in the middle. If any two parts separate it usually starts at the ends. Not the centers.
Title: Re: Number of Hinges to attach Flaps
Post by: Shug Emery on December 27, 2018, 08:31:42 AM
You may like watching Windy's hinging video. It changed the way I do it now.
Skip around in the video but some hinging at 1:38 in.
Shug

https://youtu.be/iHLHY-Fuii0 (https://youtu.be/iHLHY-Fuii0)