How do I scale up a 1/2A plan to an .09 sized plan?

I downloaded it. I guess you define the dimensions on your original and generate the output based on that. I'll need to read up on what it actually does. I just don't know what size I need to expand it to to make it an .09 sized plane plan. For instance, what is the typical weight of an .09 model plane?

I might could help if it was CL, but R/C planes can have large spans for smaller engines. What is the 1/2A span?

Look up similar plans for airplanes that take an 09. Base on wing area or wing length determine a scale difference and use this percentage to change your print size.

Double check the airfoil shape and spar dimensions for suitability so you don't end up with an overly draggy airfoil or extra over heavy spars.

That's about the best suggestion I can give. I have considered re-scaling plans before but haven't. If you consult "Das Ugly Stick" iterations they have those scaled for quite a few engine power plants so this might simplify the process.

Phil

Those are helpful suggestions, Phil. Thanks.
I have posted a question at RCG in the Builders Workshop. I may as well toss it out here for our members to read. Here is my RCG post:

I want to take plans for a 1/2A (.049ci) stick and tissue Kadet, and build it large enough to fly with a Tee Dee .09. I know there are many scaling threads, which I will read to try and learn how to make the actual changes to the plans. But what I need to know first is how to figure the actual percentage of plan expansion.

Is it completely based on engine power? For instance, a Tee Dee .049 puts out about 80 watts at peak rpm. A Tee Dee .09 puts out about 180 watts at peak rpm. That's a 125% increase in power. But I know that horsepower and and the increase in a plane's speed are not a linear proportion, so I wouldn't make the model 125% larger, that would be too much. So maybe there is a formula? And possibly other considerations?

looking at the 1/2a Kadet, and my own Kadet Sr. and Mk. I built years ago, as well as other 'scale type' planes with short noses, that end up tail heavy, i might just go with the plans 'as-is' you can always throttle back. With lighter electronics the extra weight of engine is a non issue.
If you wanted to just build a larger plane no more then 20% or maybe just extent the wing 4-6 inches, it really depends on what you want the plane to do.

I would go 150% ie 50% larger.

Btw to scale up and down plans I usually get in PDF format, I just scale them when I print them and print out on a A1 plotter. The PDF reader I use ( PDF xchange viewer) has that option. Once printed you can eyeball it and check measurements and maybe print again if scale is too much or too little.

...if its a 40" wing, then 60" for a .09?

It looks very light, sure, why not?

I'm assuming its a slow flyer?

a kadet jr. is 48" its also a little heavier, 60" would be a floater and kinda cool, like i said it would really depend on what you want the plans to do.

Yes we'll 20% is probably fine then, maybe even 15% is you build it heavy.

Engine size and weight will change as (length)^3

So if you change the engine by a factor of 1.5 then you should scale the length by (1.5)^1/3 = 15%

(this will ensure that the cubic wing loading stays the same while scaling up or down)

Surfer_kris wrote:Engine size and weight will change as (length)^3

So if you change the engine by a factor of 1.5 then you should scale the length by (1.5)^1/3 = 15%

(this will ensure that the cubic wing loading stays the same while scaling up or down)

Interesting. Does drag scale like that too?

pkrankow wrote:Look up similar plans for airplanes that take an 09. Base on wing area or wing length determine a scale difference and use this percentage to change your print size.

I think that'll guarantee something that'll work, since there's examples.

I think Kris is right on the money
For smaller models.
My YS range goes
63 Extreme flight Extra 58in W/S
110 QQ Yak 54. 69in W/S
160 Weston Capiche 140 78in W/S

These are similar hotshot 2+ power to
Weight ratio aircraft.

I'd decide the size aircraft you'd like
And if it falls say between 1.25 and 1.4
Go for it.

Excellent info, thanks. I was overestimating the difficulty of getting it right. Not nearly so critical as if I were scaling up a control line stunter. I just want a gentle floater. Once I get my two main current projects out of the way, I'll look into cutting Kadet parts. And I'd forgotten I need a throttle carb for my Tee Dee .09, so I'll have to look into that. I hope that's not something hard to get.

There is an old "rule of thumb" form the 50-ties regarding how to design airplanes, it works on a principle that the "regular" weight/wing area does not scale properly. So instead one should look at the "cubic" wing loading;

weight/(wing area)^3/2

i.e. the weight is compare to the length-scale in cube (a volume) rather than an area. Further more, the cubic wingloading will give you a "guide number" for how your airplane will fly. With the weight in grams and the area in dm^2 you get the following rule of thumb (approximate only, but it does work);

Floater; 5-8
Sport; 8-12
Warbird/pylon; >12
Flying brick; >18

If you prefer to use non SI units, the formula can instead be expressed as;

1728 x weight (oz)/ wing area (inch2) ^3/2

So in order to preserve the cubic wing loading number you scale your plane up or down by (change in weight)^1/3. This then means that your total plane weight can go up by the same factor as the engines size is changed with (i.e. 1.5 in your case)

Copied and pasted. I can work with that. Thanks Kris.

RknRusty wrote:Excellent info, thanks. I was overestimating the difficulty of getting it right. Not nearly so critical as if I were scaling up a control line stunter. I just want a gentle floater. Once I get my two main current projects out of the way, I'll look into cutting Kadet parts. And I'd forgotten I need a throttle carb for my Tee Dee .09, so I'll have to look into that. I hope that's not something hard to get.

A throttle ring would be easier to find than an .09 carb.

RknRusty wrote:As I've mentioned(couldn't find my thread), I want to build a Kadet. Rolla gave me plans for a 1/2A size, but I'd rather build it for my Tee Dee .09. How do I multiply the percentages to get the right size plans. I don't know exactly how big an .09 sized plane is.

you don`t have to go to all that trouble, just slap the 09 on her and get your thumbs limbered up for action;such as my TD049 pwered ACE littlest stick.................

just kidding , I believe the ratio was 25-40% increased from 049 to 09, as its nearly a 50% increase in displacement so depending on the wing loading etc you desire. Some folks would merely stretch the wingspan to increase drag and lighten th wing loading all at once.