Notices
RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

Thrust to weight or drag

Reply

Old 11-02-2019, 01:46 PM
  #1  
mikes68charger
Thread Starter
My Feedback: (33)
 
Join Date: Oct 2010
Location: , OH
Posts: 1,808
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Thrust to weight or drag

So I'm thinking around my newest winter project, it's my Byron F15, I actually sold it 4 years back because my buddy told me to stick with real jets. Well after 2 different owners it now back at my house.

So I have seen Surlocks YouTube clips of this bad boy flying with a single VT80 barley, then with K140.

So as this Byron is the exact same size as the Fabio 1/7 which typically has 2 K140. Why dose the Byron Fly with 1?

Should I go with a K140 and add ducts and gear doors to decrease drag, or would going to a K210 better.

So what's the rule? 32 pound F15 with K140 will not go any faster unless you decrease drag (ie gear doors and ducts) or if you don't decrease drag it would take 42 pounds of thrust to overcome drag?
mikes68charger is offline  
Reply With Quote
Old 11-02-2019, 05:48 PM
  #2  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,346
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Drag goes up as a square law. You need 4 times the thrust to go twice as fast.

So all else being equal (very important point), the 42 pounder will only be 15% faster.

I can't guess what ducting would do for drag, but I would never run anything open with one of these giant rectangular cross section fuselages. I myself might make a single duct/bypass, discretely block the other inlet and run a single turbine out one is the outlets.
mr_matt is offline  
Reply With Quote
Old 11-02-2019, 08:00 PM
  #3  
mikes68charger
Thread Starter
My Feedback: (33)
 
Join Date: Oct 2010
Location: , OH
Posts: 1,808
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks That's what I need to know,

Its amazing that this big F15 flew with 2 Nitro Ducted fans at 10-12 pounds of thrust x 2 vs the 40-60 pounds the Fabio uses
mikes68charger is offline  
Reply With Quote
Old 11-03-2019, 03:19 AM
  #4  
Ceeray
 
Join Date: Dec 2006
Location: Kuopio Finland , EU
Posts: 278
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I had twin vt80 in my FB su27. And once got into a tight spot after a failed approach. Not enough power to accelerate fast enough from a nose high stall position.

now upgrading to twin 100xbl, just because of experiences. Fighter type jets are ok when speed up or excess power but when bottom first high alpha occurs power is needed..
Ceeray is offline  
Reply With Quote
Old 11-03-2019, 01:45 PM
  #5  
erh7771
My Feedback: (30)
 
Join Date: Jul 2005
Location: Independence, MO
Posts: 402
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by mr_matt View Post
Drag goes up as a square law. You need 4 times the thrust to go twice as fast.

So all else being equal (very important point), the 42 pounder will only be 15% faster.

I can't guess what ducting would do for drag, but I would never run anything open with one of these giant rectangular cross section fuselages. I myself might make a single duct/bypass, discretely block the other inlet and run a single turbine out one is the outlets.
+1

The extra static thrust would help most with verticals vs straight speed.

With full ducting the EDF Byron F-15 Lock has now goes into the 140s 150s iinm, not sure it can get up there without the ducting.

Last edited by erh7771; 11-03-2019 at 01:56 PM.
erh7771 is online now  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service