This is a question I have been meaning to ask as well and also when scaling down, does the airfoil scale down directly or does it need to be modified.  There are some truely beautiful ships that are just too large for me.  I like them in the 48' and under range.

There are at least 2 ways to scale a drawing.

The first is to scale by linear dimension. As an example, lets use wingspan for our measurement.

Divide the measurement you want, by the measurment you have.  A design that has a 60 inch wingspan, and you want a 48 inch wingspan. Your scale factotr is 80%, 48 diveded by 60 = 0.80.

The second method is to use the sq. inches as your scale factor. A design that has 650 sq inches, and you want 500 for your .20 power, as an example.

500 divided by 650 = .77, but since these are sqared numbers, you must take the sq root of .77 which would . about .88 rounded off. As you can see, it's important to get the square root when dealing with wing areas. Please don't ask me how I know this....

Hmmm,

Scaling down a large plane to an FP 20 size?  How do most do it?  Take the original plans to a commercial copier and scale them down so it looks about right for an FP .20?

Oh, what do I want to scale "down"  Well, the Skyscraper to FP .20 size....

Jim Pollock  

Hi Jim,

Did you ever get it sized down?  And will you use the dihedral?

Thanks!
Bill

Hi Lou,

I had been wondering if Jim had done anything with the mini Skyscraper.  As to wing area of a model for the OS 20FP, I think it could be a bit larger than 360sq in ( I know that was just a hypothetical number) when using a built up fuselage, etc..  I know John Miller has a plane for the OS 15FP/LA that has *variable* wing area, going from 380 to 400 to 420 and that is .15 FP size, so the .20FP *should* be able to pull a bit more.  A Dolphin would be a good candidate I think.  It is closer to 500 sq. in. I think.    Anyway, I have always heard that people in WAM would use them, and similar planes to fly in "A" Stunt.  A Veco Lil' T-Bird would be good, but smaller, I think.

I *believe* the 20FP could handle a 450 sq. in.-475 sq, in. stunter if built light, using appropriate size lumber for a .20 plane.

I would like to see the numbers for a Skyscraper reduced to 48" WS from the original 60".  I am not well versed in figuring stuff like that.   There are several planes I would be interested in seeing that are reduced for the 20 FP.  Including a USA-1!

Bill

Hi Randy,

yep, Pat does scale down plans!  I have two sets of plans for his F-4 Wildcat he designed for the ST 60 (Bill Hummel).  He did ".51" and ".40 size" plans for me.  He also cut me ribs for he .40 size.

Pat is so busy with the BOTR members doing projects, he has a *time* problem!   But, that's ok!

A friend just scaled down a set of I-Beam Classic design plans for me.  I hope to have them soon!   A fun project, especially since I have never even seen the original built in person (or even in the last 45 years!)

I still need to build my RM 207 (which Pat originally designed on my prodding), and RM 576 (water jet cut short kit!)!

Like some one here says, "Too many planes, not enough time!"

Bill

Hi Bill,

When I used to fly class "A" Stunt back in 1961 I used a 622 Sq in Pegasus that weighed 31 Ounces.
Only trouble is, WAM hadn't changed to the Aldrich AMA pattern yet, they just used the older in-between
pattern.  I think the Dolphin build lightly would be about right for an FP .20 these days.

Jim Pollock

Hey, Jim!

Any work on downsizing the Skyscraper?  It would be killer looking.

Bill