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fokker dri wing incedence

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bert baker07/11/2018 21:04:04
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1226 forum posts
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Has any one got a plan for the Flair 1/4 scale Fokker DR!.

I could do with the wing angle set up

Simon Chaddock07/11/2018 21:35:00
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No plans but this period drawing does suggest all the wings, and even the undercarriage wing, were all set at the same angle of incidence.

Due to the relatively close spaced wings the slot effect on the lower wings ensures the top one stalls well before the others resulting in a gentle but positive nose drop.

Note also the 'incidence' of the tail plane! My own much smaller Triplane with true scale wing sections confirmed it really needs to be like that.

bert baker07/11/2018 23:46:31
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Many thanks,

I overlooked the obvious,,, the bottom and middle wings are set as they seat on to the fuz.

The top wing at moment is floating until I fix it’s angle..

Ikura08/11/2018 10:59:44
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226 forum posts

Here is a quote from a guy who has built and flown 3 Fokker Dr.1 Triplanes. He seems to have it worked out very well.

" On my 3 DRI's, two 1/4 scale and one 1/3 scale, top wing is set at -1, mid wing at 0, and bottom at +1. This causes the bottom wing to stall first, and then the mid and last the wing that really does the lifting, the top. Stalls are slight and straight forward. If the top wing is set at +1 or so, it will stall first."

Simon Chaddock08/11/2018 14:07:46
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I am not sure stalling the bottom wing first is a sound idea.

I may be wrong but due to the wing stagger the bottom wing is behind the mean CofP of the 3 wings so when it stalls and looses lift the mean CofP of the still un stalled mid and upper wings will be further forward so creating a nose up pitch. This would not be desirable.

Ikura08/11/2018 14:12:46
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226 forum posts

I only posted the above to help the guy, but if you know better and have experience of flying Fokker Dr.1 Triplanes then I bow to your wisdom.

Denis Watkins08/11/2018 14:17:38
3133 forum posts
144 photos
Posted by Ikura on 08/11/2018 14:12:46:

I only posted the above to help the guy, but if you know better and have experience of flying Fokker Dr.1 Triplanes then I bow to your wisdom.

 

All comment help Ikura

There are those that offset one wing, so both do not stall at the same time

My view has always been zero/zero, as bipes are difficult enough flying straight without building in assists

Edited By Denis Watkins on 08/11/2018 14:18:08

Ikura08/11/2018 14:23:25
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226 forum posts

Flying Biplanes is very different to flying Triplanes. You also have to figure in the Fokker Triplane's axle cover which is also a flying surface.

bert baker08/11/2018 20:41:39
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1226 forum posts
263 photos

Many thanks for all info,

I will have to second guess the size and shape of the undercart wing as the one on mine has been left off

Don Fry08/11/2018 21:10:21
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I have a Flair Triplane . I no longer have the plans. Donated .

But, my undercarriage wing is parallel to the bottom wing. Fact, measured.

If you try to stall it, flying in a straight line. Straight line mind. It nods, and settles in a 40 degree decent , at full up, motor at tickover, at moderate flying straight line speed, and it's stable. It answers to aileron. Rolls.

Now bottom wing and middle wing are locked onto the fuselage,.

I think the top wing is not stalled. It has the aileron what still works.

Therefore I reckon the top wind has a small negative incidence to the rest of the wings.

I will try to establish to whom I donated the plans.

bert baker09/11/2018 09:04:36
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1226 forum posts
263 photos

If I set the flat area where the middle wing seats to 0 degrees,

The middle wing when measured with a Robart gauge is at +2, the tail is at +3

Ikura09/11/2018 09:17:12
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226 forum posts

Bert, try the following for the Fokker Triplane to fly without it being a nightmare:

Top wing: -1 degree

Middle wing: 0 degree

Bottom wing: +1 degree

Stabiliser: 0 degree

Axle fairing: 0 degree

Jon - Laser Engines09/11/2018 11:26:28
4110 forum posts
155 photos
Posted by Ikura on 09/11/2018 09:17:12:

Bert, try the following for the Fokker Triplane to fly without it being a nightmare:

Top wing: -1 degree

Middle wing: 0 degree

Bottom wing: +1 degree

Stabiliser: 0 degree

Axle fairing: 0 degree

The tail needs a significant incidence so 0 wont work. I have the smaller flair triplane and it, along with my flair nieuport, have the tail at a pretty serious angle. I really dont think 0 is a good idea. 

For the main wings, i would stick them all at 0 and just forget it. 

Edited By Jon - Laser Engines on 09/11/2018 11:27:07

Alan Gorham_09/11/2018 12:33:23
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621 forum posts
84 photos

About +3 degrees on the tailplane is required as it avoids the need for downthrust on the motor. I wouldn't agree with setting the tailplane to 0 degrees.

I have a Flair Dr1 and I'm fairly sure that all wings are at the same incidence, which is set by the fuselage for the lower and mid wings. It's also nearly impossible to stall from level flight, so that must say something for the setup.

13923577_10208175398715058_9114253461997369865_o.jpg

bert baker09/11/2018 13:12:46
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1226 forum posts
263 photos

Many thanks,as this is a repair rather than a new build, I and stuck with the layout,

I could do with a picture or the undercarriage wing., fairy straight forward to make.

Alan Gorham_09/11/2018 13:22:57
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621 forum posts
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The Flair model isn't scale, so you can make the axle wing by eye. Some of it's dimensions are set by the distance between the wheels. i made a replacement one for mine a few years ago without a plan.

If you google for Fokker Dr1 plans there are plenty of other model Dr1 plans that are free to download to get ideas, but honestly it's simple to do on a "that looks ok" basis.

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