Flap hinges

[Juan Valentin]

  I have noticed that new stunt model designs and kits show a lot of flap hinges and at least two close to the flap tip. What is the purpose keep flaps aligned or to avoid some type of faiulure?
                                                                                                                               Juan

[James Mills]

I'm sure it helps with alignment but I think the main purpose is to prevent the flap from bending/bowing when under load.

James

[EddyR]

It is very common for hinges to break at the flap ends. Noblers are not a problem but 60 ounce planes will do it all the time so people started to double hinge at the tips and the problem went away.
Ed

[Ted Fancher]

It is very common for hinges to break at the flap ends. Noblers are not a problem but 60 ounce planes will do it all the time so people started to double hinge at the tips and the problem went away.
Ed

Ed,
I actually picked it up from Bob Gieseke on his Gieseke Nobler.

Ted

[EddyR]

Hi Ted    Speaking of Bob here is his Nobler at the 84 Nats. I though that someone would catch that example I used but I wanted to keep it simple. Back in the 50's I don't remember ever having any flap hinges break on my Noblers,but then I was using cloth hinges. Dave Merithew until his death two years ago was still flying my 1957 Nobler  with its old cloth hinges. Every time I saw it fly I though they would disintegrate as they were very rotted with age.What ever I used it sure was good material. It is interesting that you mention the Gieseke Nobler as that is were I first started having problems with hinges breaking at the tip. In the early 80's  I started started to fly the G Nobler with ST/46 motor and did a lot of practice and was using mechanical hinges and they were breaking at the tip. I suspect that many of my stunt planes back in the 50-60's didn't get old enough to wear out the tip hinge.
Ed

[Tom Niebuhr]

The only place that I ever had a hinge fail was at the outboard flap tip. As a result I have been using double hinges at both flap tips for at least 30 years. This was before I saw others with double hinges. I guess there are a lot of great minds out there.

[Juan Valentin]

  Thanks for the answers. I  thought that at the speed I have seen some of the planes fly that flutter was not a problem but I was wrong. I will save the information and use it to avoid problems.Thanks again to all replys.
                                                                                                                         Juan

[Tom Niebuhr]

Juan,
I have not observed flutter as a problem. It is just high loading at the flap tips.

[frank williams]

I've always thought the flap tip problem was a structural resonance problem.  Just running on the ground I've seen some flap tips become a blurr.  Just my two cents.

[TDM]

Juan,
I have not observed flutter as a problem. It is just high loading at the flap tips.

When i put my hinges far from the tip of the flaps it was fluttering. I do not see it necessary to put twohinges on the tip of the flaps however i do see it necessary to put the hinge as close to the outer edge of the flaps as is reasonable achievable. More over the flaps should be made of a C grain wood. I highly suspect the the broken flaps tips are from a bad quality wood combined with a hinge that was far from the edge.

Dorin

[RandySmith]

I have been using two hinges at the tip of the flaps since 1972, after I had the end hinge break on 2 models and saw them break on several others, if you look at the flap end when a plane is running on the ground the ends of the flaps are vibrating most, Never had a problem since I started using 2 hinges out at the tips

Randy