Scaling Up Plans?

I want to scale up a plan. Take for instance the wing span. eg 32 inches. I want to make it at 48 inches. If I can work out the ratio of scaling up then I can apply the ratio to all dimensions. I have tried to solve it using some maths but the latter not my best subject. I have tried online formulas but these ask for scale ratio in first instance. ie; 1/32 to 1/24. Not what I want.

Help much appreciated.

Hi Phil, divide 48 by 32, this gives 1.5. Multiply all dimensions on the 32" plan by 1.5. If using a calculator, key in 1.5 as a constant. All you need to do then is key in the dimensions of the 32" plan the conversion to the dimensions needed for the 48" version will be automatically displayed.

Phil.

Having faced the same problem when I built my 5ft span Frog Janus using the original 44" span plans (a 136% increase) I know you have a scanner so just set it to 150% and scan the plan in sections which you can then print out. Finally taking a large roll of sellotape, assemble your plan for the larger version. Job Done. Alternatively take the plan to photocopying centre like Hobbs 178 Old Christchurch Road, Bournemouth, Dorset, BH1 1NU and get them to do it for you.

Happy building!

Sheet Balsa should turn up tomorrow from SLEC but not sure when to start on the next weird n wonderful. When the snow arrives maybe.

Is there not anywhere else than can scan and print large plans from the original other than David's suggestion?

Any copy shop will be able to do it. XeroCAD in Ferndown. Office Outlet (Staples) in Bournemouth...the list is going to be endless.

A few things to watch out for:
When you scale up a plan like this all of your wood dimensions will be increased but you don't necessarily need to use larger stock. For example, a 32" model might use 1/8 sheet fuselage sides and 1/16 wing skins. A 48" model would probably use exactly the same sheet sizes but your photocopied formers and ribs will not take this into account.
Notches in formers and ribs for stringers and spar caps will be bigger than a standard size and you will have to fettle a bit to make it fit.
A scaled up model will tend to look out of proportion. A small model needs a larger tailplane (as a percentage of wing area) and whilst these large tailplanes look right on smaller models it does tend to look out of place on a larger one.

Good point Mike. As a rough guide to scaling spars and longerons, take the cross sectional area, multiply it by the scaling factor, then get the square root of the result. For example, a longeron that is 1/4" square, becomes 5/16" square at a scale of 1.5 . You can prove this by drawing the section on squared paper, it isn't quite perfect but its near enough.

OK Chaps,

Here is another one for you all. Anyone got any experience with CAD?

I want to take the small three views & cutaways I have for the Somers Kendal SK1 get them scanned onto CAD somehow, cleaned up, then printed out at 1/4 scale and 1/3rd scale so that I can start designing the construction methods (the old fashion way with pencil and ruler etc.) to then get everything transferred onto CAD so that I can get formers/ribs etc laser cut in both scales.

Have been doing a little online research but having never used CAD in anything other than basic levels (usually just print out of existing files from Solidworks files) in the past (and not having any CAD software of my own currently) I would appreciate any advice anyone has with knowledge or experience in this area? In my limited experience once the outline is within the CAD and scaled to full size the printouts at any scale is relatively easy (CAD Plotter and paper sizes allowing etc).

It would appear that there is no easy way to scan a three view and convert to CAD vector graphics, it would appear that one has to scan in the three view as a bitmap then draw over the top of it on a different layer. I would have thought in this day and age there was some sort of software that could do a straight conversion!!!

Anyway, must be someone in the club who has extensive CAD knowledge?

Peter

Hi Peter, you've taken on quite a challenge. Don't know if this will be of any help, I've used a program called Profili for model design and all the fiddly bits such as ribs for tapered wings and formers for fuselages. That was a long time ago when I was an enthusiastic builder and flyer of free flight models. Have a look at the Profili website, I think there's a trial version. Well worth a look.

Peter
I make my frames on a cnc machine and use a free drawing program called Inkscapehttps://inkscape.org/en/ to do my
drawings.I presume you have paper drawings which could be scanned which can then be traced in inkscape which you can then clean up and scale. I just use a camera and trace photos which works well for copying existing broken parts.
I could cut parts out for you.
John