View Single Post
Old 01-28-2009, 01:41 AM
  #37  
Dereck
Super Contributor
 
Join Date: Oct 2005
Posts: 1,071
Default

[quote=d&mrc;553422]I have been doing my best to absord everything you guys have told me, and everything I have read in online articles (some that you linked to, and some you did not) so far, I have learned this:
1. How to scale the plane, and, subsequently, I have my dimensions

>>>That's often the easy part. Some of us work on that balsa comes in 36" lengths!

2. There is a mysterious mathematical force that causes even the most precisely designed and built scale models to fly COMPLETELY differently than their full-scale counterparts when their weight is to scale.

>>> I used to live just off the approach path to a major USAF base in England. To watch a C5 freighter - the biggest flying thing in the USAF at the time - left one with the impression that nothing could fly going so slow. It's all a question of scale - what a surprise! BUT - look at models by the best scale designers, at any scale or discipline, and their models 'look the part'. One of the best examples I've seen in the US is Dave Grife's Mosquito from England's Brian Taylor design. It isn't that big, by modern RC scale standards and when I saw it, it was staggering under the weight of a lot of nicads and big brushes motors. But - and I've seen the real one fly - it looked just like the 'real thing'. Math can do a lot, but sheer talent, practice and dedication to what is more art than science can do more.

3. This force is beyond the understanding of mere mortals such as myself.

>>>And a lot more of us

4. The only way to combat said force is by making your model as light as possible, and hoping for the best.

>>>YES!!! You've got it spot on!

5. How to calculate my watts-per-pound requirement.

>>>Mostly, I use someone else's and build my model a little lighter

6. For some reason, I seem incapable of calculating wing areas.

Length x width = area. Span x average chord (easy with most WW1 bipes and even trips). Eyeball the wingtips. Don't lose sleep over it unless the 6 o'clock news starts reporting a wobble in the earth's rotation before the first commercial break.

Now, I am left with these questions:
1. Is there any risk of making my model too light?

>>> If you think you have, write an article describing how you did it and sell it to a model aircraft mag. The right mag would be handsomely. Or you can give it away on the internet

2. If I do not maintain a scale weight, should I still maintain the same power to weight ratio as the full scale?

?

3. What the heck am I doing wrong in regards to my wing area calculations? Did this problem carry over into my other area calculations?

>>> Got me there, sorry

4. Does motocalc know what its' talking about?
>>>GIGO, in old data entry speak. I admire the folk who do these programs, but whoinell is testing all the cheap Chinese ripoff motors for these selection programs?

5. When adding up my watts per pound to give me my total watts needed, should I use my target AUW, the kit weight, or kit weight with motor?
>>> The only one that's valid is the weight as it rolls down the runway. See previous on lighter weight being a cheap upgrade. Remember that it is far, far better to have too much grunt up front and have to throttle back than to be over the far end of the runway desperately wishing you had more power to haul months of work away from the ground and the stall speed.


Regards

Dereck
Who's published around three dozen sports and scale plans in various mags on both sides of the pond...

Without a lot of math causing cranial overstrain either
Dereck is offline  
 
Page generated in 0.06264 seconds with 7 queries