Fus Dimensions

[Mounty]

I have been designing a couple of my own but have pinched the fuselage dimensions from similar size models, how do I work this out, I can figure out the length etc from Peter Millers book but not the height and depth how do I get these measurements. Help, Thanks, Joe

[Craig Spence]

Hi Joe,

 

Im just venturing into this sort of thing myself, although your post is a little vauge to me.

What are you designing, I take it its based around a Peter Miller design and if its a wing from that sort of design that your matching to a fuz than you might have the potential to do so.

 

More deatils please Joe.

 

There are lots of people on here who are very good at this sort of thing, im just breaking into building and designing. Working out wing loading and other things is going to be my next lessons to learn.

 

Cheers Joe.

 

[Erfolg]

Joe

 

The fact is that most models are either scale and the proportions are pretty much as full size. Or are the result of application of experience from building, flying and copying the general proportions of other designs.

 

I have never read the Peter Miller articles on the design of models, but would suggest it is a good starting point.

 

My own approach is as follows

 

a) what do I want the model to do? this will decide the section, say E205 or the current fashionable section MH32? for a glider, for an acrobatic model NACA 0014 for an electric and so on. what i am trying to do is provide a suitable section forits  purpose, glider needs good LD characteristics over a wide speed range, aerobatic require a section which works anyway up, highish drag to stop acceleration when  going downhill.

 

a+) Wing span and chord.

 

b) moment arm

c) tailplane size

all a, b &c are very much related by area of wing to tailplane, moment arm, there are a few mathematical relationships which enable the static margin to be established, dependant on the ratio, the sensitivity and damping characteristics. Most people eye ball it, drawing on previous experience and other models. It is a hobby for most.

 

d) The nose length is essentially a need to get the model to balance about the CG,  the longer the nose generally, the greater will be inertia effects. Yet stay within normally seen chord ratios, with RC models less of an issue.

 

d) The Cg is often just set at about  max 30% chord. But is calculated by some from the other info calculated, relating Neutral point, static margin tail plane volume. But the vast majority of hobbyist would not dream of the approach. Yet if inclined, use an online CG calculator.

 

In essence models are generally not rocket science, but built from the experience of others, and applied to your design, by observation, FOR FUN! 

 

Erfolg

[Mounty]

Thanks for the answers guys, Craig to answer your question, I have already designed and built several models one a biplane called Tthe Phoenix which can be seen on youtube (joemountford1) and which flys very well, the general dimensions I pinched from a written off World models Ultimate 40s (as was the tail feathers) another a 25 driven 40" span the dimensions again pinched from a plan somewhere or other, the information from Erflog is great and without wanting to seem thankless, I already had from the Peter Miller book, but I just wandered how I come to the general fuz sizes when drawing up my own plans?

Wish I could figure out how to upload photos, I would show you a couple of my own designs.

 

Thanks again Craig and Erflog.