Stuart t Posted February 28 Share Posted February 28 Hi Scaling up a wing , i increase the wing span and wing chord , do scale up the section thick by the same amount as the span / chord ? Many thanks Stuart Quote Link to comment Share on other sites More sharing options...
Jim Hearnden 1 Posted February 28 Share Posted February 28 In theory whatever the section if you scale up the chord then the thickness increases by the same %. It depends if its a catalogued section or not. If its a sport model then to use Dave Boddingtons comment, it'll be whatever French curve I had to hand! If is a defined section such as a NACA 4 or 5 digit one then you should replot it for the new chord. Having said that with the accuracy we build at & the speeds we fly at it will make little difference in the real world! Quote Link to comment Share on other sites More sharing options...
kc Posted February 28 Share Posted February 28 Welcome to the forum, Yes, just printing the same airfoil section at a larger size will do that. Try to find a similar section in Profili free version and print at the required chord size. You might find the p[an on Outerzone etc to save the trouble - lots of free plans that can be printed or resized in Adobe Acrobat then loaded onto a memory stick to take to a Copy Shop for printing at 100 percent or whatever you want. 1 Quote Link to comment Share on other sites More sharing options...
kc Posted February 28 Share Posted February 28 You could scan the airfoil on your plan and save as a PDF and open that PDF in Acrobat then print using " Custom Size" to 120 percent or whatever you need. Same for any formers or other parts. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted February 28 Share Posted February 28 Short version, yes, when it comes to outlines and profiles, just scale everything equally in all the dimensions. Material thickness is a different question. Quote Link to comment Share on other sites More sharing options...
Stuart t Posted February 28 Author Share Posted February 28 Many thanks for your speedy reply's , certainly makes it easier , it just looks a little fat ! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 28 Share Posted February 28 Looks a little fat? It shouldn’t have changed its shape at all! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 28 Share Posted February 28 Just remember the match stick scaling law. A match stick as a beam can support many times it own weight. A 50 ft long scale match stick beam is likely to collapse under it own weight. If everything is scaled up in proportion the resulting wing will heavier but will actually be just a bit weaker. Looks fat? You certainly don't want to make it any "thinner" unless you seriously change the way it is made and/or the material it is made from. Quote Link to comment Share on other sites More sharing options...
kc Posted February 29 Share Posted February 29 If scaling up a design then the size of material needed for wing spars etc could be guided by models of a similar size and type. Outerzone is full of plans of every type that can be studied free of charge - there must be something similar. Somtimes if the change in scale is not too much then maybe just a change of material instead of increasing size would work - e.g 1/4 sq balsa spars might be changed to 1/4 spruce if increasing span from, perhaps, 48 inch to 53 inch. If you advise us the design you are scaling up then maybe someone will know of a similar type of successful model which can be used as a guide. 1 Quote Link to comment Share on other sites More sharing options...
Phil Green Posted February 29 Share Posted February 29 Ahem. "AerOfoil" - it matters! :) 2 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 29 Share Posted February 29 Perhaps we shouldn’t be too hasty in making a judgement. The OP might hail from a land where such aberrations are not only tolerated but actively encouraged! Quote Link to comment Share on other sites More sharing options...
Robin Colbourne Posted February 29 Share Posted February 29 18 hours ago, Nigel R said: Short version, yes, when it comes to outlines and profiles, just scale everything equally in all the dimensions. Material thickness is a different question. Material thickness and choice are very definitely very important. A friend is building the Valueplanes 1/4 scale Miles Hawk. It is 2.48M (97") wingspan, yet seems to use materials of the size and weight, or even thicker, than a full-size wooden glider. Where the wing roots abut the fuselage, the fuselage has four laminations of liteply, making it about 10mm thick. My concern is that the thing has massive strength in places, yet potential weak points where, for instance, the longerons are cracked to go from parallel to tapering in towards the tail. When scaling up, always remember, dimensions goe up linearly, areas are squared and volumes are cubed. Twice the size is eight times the volume. Quote Link to comment Share on other sites More sharing options...
Stuart t Posted March 4 Author Share Posted March 4 I have carried a little research and from a reliable source ( the original designer ) i have the aerOfile ! X/Y coordinates i will use these to expand the section, naca3412 for ref. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 4 Share Posted March 4 One factor that hasn’t been mentioned is that aerofoils work differently at different scales so simply scaling one may not give best efficiency. However, at our normal sizes and build accuracies, I’ve never felt that aerofoil choice (within reason) will make very much difference to performance unless it’s for a specialised competition model. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted March 4 Share Posted March 4 On 28/02/2024 at 19:09, Stuart t said: Many thanks for your speedy reply's , certainly makes it easier , it just looks a little fat ! Arrrr, you get to carry eight times more weigh in the material. Ie your basic wing weight has grown by eight times. That’s eight times the power needed. Airfoils don’t scale, but for practical purposes for small changes like this, they still work. For the structures you are looking at, twice the span, twice the chord, 4 times area, 4 times the power needed, 4 times the weight. So spar size old, changes to new is 1.4, square root of two So the new dimensions are the old dimensions times multiplied by 1.4, wot provides an airframe weight IRO 4 times original. All to get something with the same(ish) wing loading. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.