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-   -   Aileron hinging (http://www.Wattflyer.com/forums/showthread.php?t=73241)

thepiper92 02-24-2014 04:04 AM

Aileron hinging
 
I am hoping this is the correct section, my reasoning that the answer to this question can deal with aerodynamics. With this build I am doing, the p47, the plans show fibre hinges for the ailerons. Now in my P51, the elevator and rudder edges were rounded or triangled to allow them clearance to pivot if that makes any sense. For ailerons, they were angled at the pivoting edge, and then hinged at the bottom. This leaves, when the ailerons are even with the wing, as notch at the top, but a smooth bottom. I am having difficult coming up with this description, so sorry ahead of time, but which is better for ailerons, a smooth hinge along the bottom made from covering or decal, or hinging like the elevator and rudder?

fhhuber 02-24-2014 04:25 AM

For least drag, if you are going to have a V notch for the aileron hinge line its better to have that at the bottom (and it looks better when the plane is on the ground)

Best is to use the centered hinge behind the front of the control surface, round the surface and carry the wing's top and bottom back to meet it.

https://www.robart.com/sites/default...w_To_Hinge.pdf

See step 5.. carry the hinge point back into the surface a bit extra.
Use thin (1/64) aircraft ply or aluminum to carry the top and bottom wing surfaces back to brush the control surface, closing the gap..

*********

The difference in drag vs the hinge at the bottom is not large... especially at our size and airspeed of most sport-scale models.

thepiper92 02-24-2014 05:29 AM

So on a warbird, any hinge is good really? A Frise hinge would be the best, but probably the hardest to make, especially on a smaller model, I presume. A a bottom or top hinge, I gather the aileron actually increases in size as it moves away from the v notch, so a v notch on the top would cause the aileron that moves down to have a stronger effect on upwards push on the wing. The opposite for a notch on the bottom. The notch itself will act like a constant small elevator, would it not? With a centered hinge, the drag on the top and bottom would be equal it seems, and thus not have an effect on the pitch of the plane, just purely drag. Which is the strongest form of hinge though, assuming I will be using small hinges on a centered hinge, and a strip of material binding the aileron to the wing on a notched hinge? Also, are these Robart hinges better than using flat fibre slotted into the balsa?

fhhuber 02-24-2014 05:41 AM

Really doesn't matter what type airplane. The cleaner the hinge line the better. As expected airspeed goes up making the hinge line gapless and smooth becomes more important.

Our 2 main concerns are appearance and flutter. The drag issue is very small.

Minimal play in the hige and linkages and preventing airflow through the hinge line between top and bottom of the wing will aid in flutter prevention.

The Robart hinges generally are used on larger models.

thepiper92 02-24-2014 06:01 AM

So would not a notched hinge seal any airflow though hinge line?

hayofstacks 02-24-2014 07:38 AM

I personally really like nylon pinned hinges. miles above the ca crap.

fhhuber 02-24-2014 07:55 AM

We've been using clear/transparent tapes to seal the hinge lines. "Blenderm" is popular, but even common "scotch" tape will do the job for most e-power models.

If you can see light through the hinge line and haven't taped it.... air can get through. Many times not enough to really care, but sometimes just taping the hinge line will cure a flutter issue.

Be sure the surface still moves freely after taping. Sometimes you can do it in one piece of tape, sometimes use tape segments between hinges.

thepiper92 02-24-2014 12:30 PM

Quote:

Originally Posted by hayofstacks (Post 940835)
I personally really like nylon pinned hinges. miles above the ca crap.

Are the fibre or plastic hinges weak?

Turner 02-24-2014 02:36 PM

With the hinge at bottom or top it tends to introduce some differential. All else being equal you get effectively more deflection towards the hinge side. In practice this means with the hinge on the bottom you get more deflection downward which will induce adverse yaw. With the hinge on top you get yaw in the desired direction.

thepiper92 02-24-2014 02:47 PM

How much adverse yaw will there actually be though. The p51 has a bottom hinge, and was designed as such. With the p47, the parts are thick so I am open for centered or bottom hinging, or top of course. It seems with bottom or top, I can make used of a solid strip of material for the hinge, which would seal any air going through the hinge. With a centered I can add something to seal the space, just have to make sure I don't limit movement. If I go centered I don't know the best style of hinge. The p51 uses a clear plastic that I cut into strips. Is that a good option?

Turner 02-24-2014 04:05 PM

Quote:

Originally Posted by thepiper92 (Post 940841)
How much adverse yaw will there actually be though...

It will depend on the particular model.

thepiper92 02-24-2014 05:20 PM

Quote:

Originally Posted by Turner (Post 940843)
It will depend on the particular model.

Lol I figured as much, guess it would depend on size of aileron surface as wells as thickness of the trailing edge up to the start of the aileron leading edge, determining the loss or gain of aileron surface, taking into account of a The P47 aileron surface isn't huge. Unfortunately, I am not at home right now, so guessing at an aileron of 3x6, equalling a surface area of 18 square inches, and about a max of a 1/3 inch in aileron thickness at leading edge of aileron, that would equal 2 square inches loss in aileron surface area. For a plane of 40 inch wing span, around 20-23 oz, around 5 degrees dihedral (dihedral is not listed, just judging by the angling tool provided in the plans). This isn't too accurate likely, but maybe enough to ballpark it. Would that be a major difference to cause much adverse yaw?

Turner 02-24-2014 06:03 PM

I'm sure there are many more variables involved as well. Some designs are more effected by adverse yaw than others. I don't have any more to add. Experimentation is the best way to answer all questions.

thepiper92 02-24-2014 06:32 PM

Quote:

Originally Posted by Turner (Post 940847)
I'm sure there are many more variables involved as well. Some designs are more effected by adverse yaw than others. I don't have any more to add. Experimentation is the best way to answer all questions.

I suppose that is the best way. Probably safest with centered hinging.

Turner 02-24-2014 07:38 PM

I think so for the two planes you mentioned. I believe that high lift flat bottom wings are more prone to adverse yaw than other types.

hayofstacks 02-24-2014 08:29 PM

Quote:

Originally Posted by thepiper92 (Post 940838)
Are the fibre or plastic hinges weak?

In just not fond of them. my dad always built his nitros with nylon pinned hinges. there is no slop and very little effort to move them compared to even a properly done ca hinge.

solentlife 02-24-2014 09:37 PM

Quote:

Originally Posted by thepiper92 (Post 940828)
I am hoping this is the correct section, my reasoning that the answer to this question can deal with aerodynamics. With this build I am doing, the p47, the plans show fibre hinges for the ailerons. Now in my P51, the elevator and rudder edges were rounded or triangled to allow them clearance to pivot if that makes any sense. For ailerons, they were angled at the pivoting edge, and then hinged at the bottom. This leaves, when the ailerons are even with the wing, as notch at the top, but a smooth bottom. I am having difficult coming up with this description, so sorry ahead of time, but which is better for ailerons, a smooth hinge along the bottom made from covering or decal, or hinging like the elevator and rudder?

KISS .....

I would set my hinges slightly down from top of aileron / wing TE with a 'notched' lower section. This way - you get a nice clean top surface with ample scope to allow movement up and down of ailerons. With aileron deflected UP - apply clear tape inside the underside V notch to close any air passage / gap. This is same method as used for slab flaps. My Royal P51 had this both flaps and ailerons - worked well.

I like mylar strip hinges ... or pin type .... CA hinges have no place in my box.

Final word ... a previous post mentions flutter and taping up to stop it ... ?? Flutter is due to poor hingeing where surface is not secured properly and can flex the hinges ... it can happen with or without gap. The only other reason for flutter is extreme high speed - a fact that very few models will experience !

Nigel

thepiper92 02-24-2014 09:53 PM

So you just use the hinges that are actually hinges, rather than a piece of bendable material, like this, for example? https://www.slecuk.com/catalogue/Model-Hinges.html. Do you slot them into the wing and aileron, referring to what you say of slightly down from the TE and aileron? I gather this is more for cosmetic reasons rather than functional, eliminating a white hinge on a silver, black, blue, etc covering surface by putting it into the wood, rather than securing it on top of it.

hayofstacks 02-25-2014 02:38 AM

https://www.slecuk.com/catalogue/sl889-230.jpg

like these. no play, easy to setup and pin if you desire, and nearly frictionless. More like a hinge rather then stiff slightly flexible material. of done properly, there will be no play whatsoever and surface can only move up and down.

thepiper92 02-25-2014 03:36 AM

So these should be easy to embed into the balsa. It seems if doing a top hinge it will be weak to embed near the edge of the balsa, so perhaps a centered hinge is the best bet with these hinges.

solentlife 02-25-2014 08:08 AM

My preferred hinges are with Mylar strips.

You buy sheets about 4" x 3" and cut strips ~3/4" long by 1/3" wide. These then glue into slots made by model knife. The advantage is no gap left by pins etc.

On general models I centre the hinge but for better cosmetics on warbirds etc. I prefer the hinge about 1/4 way down from top to keep top visually nice.

Nigel

thepiper92 02-25-2014 12:57 PM

You have any pics? I can't quite visualize it.

solentlife 02-25-2014 06:48 PM

1 Attachment(s)
Quote:

Originally Posted by thepiper92 (Post 940882)
You have any pics? I can't quite visualize it.

All very simple really ... see below attached.

Here's Mylar sheet ...

http://www.ebay.co.uk/itm/MYLAR-HING...item4165e14da9

or in strip :

http://www.ebay.co.uk/itm/Mylar-Hing...item233626437c

Nigel

thepiper92 02-25-2014 11:49 PM

Okay so there is a small notch on top. Are Mylar hinges not CA hinges, they are glued into the wing and aileron with CA. Mylar is what came with the p51. It seems to work fine, but I had the impression an actual hinge is what I should get.

solentlife 02-26-2014 06:39 AM

CA hinges are development of the mylar style. A tissue like surface is applied to the plastic to absorb CA when glueing in. Personally I have had CA hinges pull out of my Ultimate bipe.
I don't like them.

I prefer traditional hinges or mylar strip. And only use Epoxy to glue them in. A trick is to make a hole in each half of strip,then when it's glued into surface... the epoxy firms a 'pin' through it. On less powerful models - saves pinning through.

I have 60 glow and 15cc gasoline engine models with Mylar as well as traditional pin hinges.

Nigel


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