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spoilers and all moving tailplane

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Keith Evans 320/11/2019 19:07:48
374 forum posts
81 photos

For a winter project I'm trying out some thing different , for me that is .

I'm looking to design and build a moderately aerobatic I.C. model with STOL capabilities utilising spoilers for roll control and an all moving tail plane in a Tee configuration .

The wing will have full span flaps and possibly fixed leading edge slats

I have information regarding the spoiler requirements i.e size and positioning but not the angular deflection they are required to operate at . Can anybody help?

Again , for the tail plane , what angular movement up and down would you recommend ?

Simon Chaddock20/11/2019 20:56:14
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5484 forum posts
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Keith

I fear your questions fall into the category of "how long is a piece of string?"

As far a spoilers go I can only suggests you look at some video of full size planes using control spoilers and I think the answer is quite a lot (80 degrees?)

A moving tail plane places great emphasis is the rigidity of the pivot bearings and even more so when the pivot is in the confined space at the top of the fin.

All moving tail planes tend to be very sensitive around the neutral position, much more so than a conventional elevator. You are of course altering the tail plane incidence where just a couple of degrees can dramatically change a planes flight characteristics.

I have one all flying tail (though not a T) and the deflection is small compared to an elevator no more than 15 degrees up & 10 down but by far the trickiest operations were positioning its pivot axis, ensuring an absolute minimum of control slop and 'guessing' a suitable tail plane neutral position for the maiden flight. wink 2

Edited By Simon Chaddock on 20/11/2019 20:57:53

eflightray20/11/2019 21:33:16
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590 forum posts
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I would suggest going to Youtube and doing a search on - STOL

They show some record breaking STOLs, - how about landing in 9ft 5in, and that's full size, not a model.

.

Peter Jenkins20/11/2019 23:45:55
1295 forum posts
132 photos
Posted by Keith Evans 3 on 20/11/2019 19:07:48:

For a winter project I'm trying out some thing different , for me that is .

I'm looking to design and build a moderately aerobatic I.C. model with STOL capabilities utilising spoilers for roll control and an all moving tail plane in a Tee configuration .

The wing will have full span flaps and possibly fixed leading edge slats

I fear you are setting yourself a very difficult, if not impossible,task as the conjunction of a moderately aerobatic model with the design features you intend to use will mean that there will be huge compromises to the achievement of "moderately aerobatic". Fixed slats will result in a very asymmetric capability between upright and inverted flight. You will be hard put to find any moderately aerobatic aircraft with the features you describe. However, I'm sure that you will have great fun in producing a STOL model that will be aerobatic but it will be a camel compared with a race horse in the aerobatic stakes. Just saying!

Keith Evans 323/11/2019 13:43:25
374 forum posts
81 photos

Thanks for the information and advice . I shall plod on and let you know the end results later next year sometime .

Keith

Steven Shaw23/11/2019 17:49:51
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333 forum posts
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Here is some info on flaps and leading edge slats that may be of use.

Martin Harris23/11/2019 21:25:29
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Posted by Simon Chaddock on 20/11/2019 20:56:14:
but by far the trickiest operations were positioning its pivot axis, ensuring an absolute minimum of control slop and 'guessing' a suitable tail plane neutral position for the maiden flight.

Neutral position hasn't presented much of a problem on the limited number of all flying tails I've set up - although the first flights have tended to have a few more digits crossed - thankfully without justification.

I simply set the wings at about 1 degree positive incidence and with my smartphone inclinometer app, set the tailplane level - although a small spirit level would do a similar job... All have been pretty close to the correct position when test flown.

Jesus Cardin25/11/2019 07:35:29
19 forum posts
4 photos

Keith, your control configuration is just that of the Jim Bede BD-5 which used spoilers combined with ailerons and an all moving tailplane (albeit not on "T" position)

As far as I know no one model of the BD-5 made use of the spoilers as originally intended.

Regarding the "T" all moving tailplane I will add to other members comments that a high position tail -and it is widely known on airline jets- is very affected by the wing since a certain angle of attack, becoming shadowed by the wing airstream preventing increasing the AoA, so a very undesirable feature for an intended aerobatic model.

Best Regards.

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