Thread: Discussion 200mph with 70mm
View Single Post
Old Nov 01, 2012, 07:07 AM
gundamnitpete is offline
Find More Posts by gundamnitpete
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
Originally Posted by murdnunoc View Post
Pete, where'd the composite wing 70mm Sniper come from?
That's one airframe I've been looking at, but I've also heard about the intakes being too large, and I saw one last week at the LHS and they do look pretty "parachutey".

If I got a composite wing version, I'd like to try pinching the intakes down. Think it'd be better to extend the intake forward and fair it in to a smaller hole? Or cut it back and take chunks out of the glass to tighten it up?

75K RPM on that DS-30 fan is ridiculous! That's why I'm looking to use a higher draw fan, to keep the watts up but RPM down.
They've been out of production since like, 2007. Your best bet is to either glass the stock foamcore wing, or reinforce it with alot of carbon rod. I saw a mod where a guy glued a drill bit on a peice of carbon and twisted it into the foam, giving a nice channel. Then he glued it in, obviously.

I would cut a "pizza slice" out of the intakes, reducing their area, and also reducing the frontal area of the sniper. If you just sweep them forward, the frontal area will stay the same, no bueno. Once you marry the fuse back together and fiberglass/fill/sand/primer it, you'll need to make new ducting. That it itself is no small feat, you will need the ducts to be as smooth as possible.

Personally I don't see the stock intakes stopping anyone from 200mph, assuming the rest of the aircraft is clean (linkages, intake lip, canopy, etc.etc.) and you've got the power.

Hey man, takes power to make power.

Originally Posted by murdnunoc View Post
There are some great minds here. You're not the only one who has understanding of power systems and airframes.

The EDF hotliner is a good idea. It may even be the best as far as the least watts for the most speed.
That's not what everyone goes for, though. Some may want a 200mph F-16, and are willing to do what it takes to get it.

If 177mph can happen on, say, 2500W, then 200mph will undoubtedly happen on 3607W. Just a matter of getting the motor and fan that can handle the power, with no other airframe changes other than strengthening required.

If it were down to efficiency alone, no one would even be running an EDF. But here we are..
Drag is an exponential increase, we can simulate it with a little math.

200mph/177mph= 1.1299435

1.1299435^3= 1.44

2500W * 1.44= 3606.

so, if the airframe stays exactly the same, around 3600w should net you close to 200mph.
gundamnitpete is offline Find More Posts by gundamnitpete
Reply With Quote