Hans Meij

Hi group,

Does the location (top or bottom of fuselage) of the stabilo play any aerodynamic role?
In general with low-wing planes the stabilo is place high in the fuselage.
With high wing models the stabilo tends to be placed at a lower position.

Thanks,
Hans

Al Stein

Changing the stab location should not matter unless it is moving into or out of the wing downwash.

If the stab does move into or out of the downwash, then more downwash on it will make the plane want to climb more as speed increases (and the opposite will happen it it gets less downwash in its new location). Keeping the stab out of the wing's downwash helps if you want a plane that does not need to be retrimmed for chnages in air speed.

Hans Meij

In relation to the answer of Al, where is then the ideal position with a shoulderwing aerobatic trainer?
In other words is the top or the bottom of the rear part of the fuselage in the downwash location.

Hans

Al Stein

Hi Hans,

I would say that the top would be best.
Are you making a new design? How big is the plane?

Hans Meij

Hi Al,

Yes I'm thinking about an allround aerobatic trainer for a TT PRO 120 and it wil have a span of approx. 190cm.

A bit like the Ikarus trainer:

Hal deBolt

Hi Hans,
Perhaps I can add some confusion or otherwise to your thinking!
Experience suggests that vertical horizontal tail location has
little effect on performance Except on something with a unusual
abnormal configuration.
A safeguard with any normal configuration is a sufficently long
tail moment arm, using such is like taking vitimins whom they say
forestalls as sorts of potentials
Investigation has indicated that an extra long moment arm has no ill aerodynamic effect while it might create a balance problem
Proven with useage on many, many designs a tail moment (From 25% of the wing chord to 25% of the horizontal tail chrord) of 42% of the wing span assures excellent tail action.
Condidering "down wash" is like shooting in the dark for us modelers and for full scale unless they have a wind tunnel to observe how much and how great it is.
For your design consider this: there have been a number of fine performing designs which feature the "in Line" philosophy where both wing and tail are on the thrust line and hopefully the center of drag also is.
Coming up soon in Model Aviation magazine is my aerobatic "Shoestring" which was done to evaluate the "in line" principle, The Shoe is an excellent performing craft.
Hope this may be of some help , your design looks neat!
Good luck!

Hal deBolt

Al Stein

I'll be looking foward to that. I think it's great that people suddenly seem to be remembering the "midget racers" that we hadn't seen modeled much for a long time... and I always thought that Shoestring was the best looking of the lot. (Well, maybe alomg with some newer planes like the Pushy Cats.

What size will the Shoesting be?

Lightfoot

My Feedback: (1)

I read an article on this subject several years ago. The point of the article was exactly has you stated. The reason given was that the wing wash moves toward the low pressure side of the wing, i.e. downward in normal flight. Except in unusual configurations, the wing wash is far away from the horizontal control surfaces. In an aerobatic model, the ideal position is in line with the wing. This results in the wing wash being the same distance from the control surface whether upright or inverted.

I have always liked the looks of the Falck Rivets. I have plans for one but I intend to modify the plans to make a sport plane sometimes in the future.

Mike James

Among the discussions we've had here on this subject, there's one where I did an experiment myself, with an Ultra Sport .40 that had a pitch coupling problem. Moving the stab down to the thrust line had a MAJOR effect, reducing this problem. The thread is at:
http://www.rcuniverse.com/showthread...294&forumid=19]

Hal deBolt

Hi Al,
Quick reply for you about Shoestring ;
Basically a 40 size: span 60" weight 4 3/4 lbs fully aerobatic
Origional liked the Enya 46 4 cycle very well'
Bob Hunt at Model Aviation would know publication date
Address: [email protected]
Lotsa luck!

Hal deBolt