Here is another Newbee Question

[Wyatt]

Hi,
New to RC but plant to be around for along time.I own my on bikeshop and RC studio that I`m just got going good.My studio remineds me of a 1929 hobby shop.I like it.
But anyway.Not the smartest when it comes to y x t x 2 plus 3=
something that I still wouldn`t know.
But I`m building a few kits that all are the same.I would like to make one alittle wider,longer and add a 49 to 61 engine.The
plane is a soild balasa wood fuse.semi.opened wing.The wigs are 4 ft, 9" with 1.5 ailerons.The fuse 37" and is 3" wider.Simple design.
I like to make the it 3" longer and 1" wider and add 1.5 to 3"
to the wigth of the wing.Also do some work on the tail.Enlarge the rudder and elevator.
What is the general rule her for this?What will it do to the CG
of my wing?Should I spilt the distance that I `m going from CG?
How do you make up for to mush weight on a plane.I have one that is getting to heavy and it just a .40 engine and I`m aload
4.5 lbs Its getting close to that now.What if I went to a .46 or a little bigger?

So many questions.Got any ideals that will help?

Wyatt

[Wyatt]

I build planes better than I spell

Wyatt

[Ollie]

The main idea in selecting an engine size is to base the engine size on the weight of the model. This is called power loading. The less the model weighs for a given size engine, the livelier the vertical performance (climb) will be. A good rule of thumb for sports models is up to one pound of weight is allowed for each 0.08 cubic inches of engine displacement. So a .40 cubic inch engine should be able to handle up to about 5 pounds of weight ready to fly and a .46 cubic inch displacement engine should be able to handle almost 6 pounds of airplane. If you want livlier performance, then use 0.10 cubic inches of displacement for each pound of airplane.

A good rule of thumb is to size the wing area to the weight of the plane. That is called wing loading. A wing loading of abour 1.25 pounds (20 ounces) per square foot of wing area is a typical wing loading for sports type models. Trainer models should have a lower wing loading of around one pound per square foot or less. Jets can sometimes have wing loadings in the neighborhood of two pounds per square foot of wing area. So the size of the wing depends on the purpose of the model. The lower the wing loading, the slower the model will take off and land and the higher the wing loading, the faster it must go to take off and the faster it must fly to prevent a stall.

BTW, wing area is the wing span times the average wing chord. If you measure the span in inches and the chord in inches when you multiply them together you get square inches. To convert square inches into square feet, divide by 144.

[Wyatt]

Thanks that helps,
I understand what you are saying.On the enlarging .If I make it longer what should I expect?Added to the cord a inch or so?

Wyatt

[Ollie]

Which "it?" The wing span? The fuselage? The landing gear? Length by itself can refer to almost anything. If you want answers you have to be completely specific.

My advise is to have the plans enlarged by a zerox machine at a service like Kikos so that everything on the new plan is proportionately bigger and the shape of the model doesn't change, just the size. If you want to redraw the plans yourself then get a pair of proportional dividers and set them for the scale you want in order to change all the lengths on the small drawing to bigger lengths on the larger drawing. You can get a pair of proportional dividers from a drafting tool supplier. The dividers will eliminate almost all the arithmatic.

[Ollie]

The least expensive proportional dividers that I have been able to find go for $40. See:
http://www.xkms.org/Sovietski-Collection-1/Proportional-divider.htm

[Wyatt]

Hi,
So the easest way would be to enlarge the hole plane.
So if I wanted to make the plane 3" longer.I would have the planes enlarged to where I got the lenth that I wanted.This will make a big difference.I don`t really want it bigger every where.
Just like to make to fuse 3" longer and add 1" to the wigth.This I can do quite easly.But don`t know what to do with the wing and
tail section.I guess I would have to do some math on my square in. and weight of the plane to see what the span and down load weight should be?
Wyatt