HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 01, 2012, 07:07 AM
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
Quote:
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.

Quote:
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
Sign up now
to remove ads between posts
Old Nov 01, 2012, 10:25 AM
More jets than a carburetor
skydve76's Avatar
United States, NE, Omaha
Joined Sep 2008
2,809 Posts
Another good candidate is that HET Me-163. Batteries are tricky but its a clean airframe.
skydve76 is offline Find More Posts by skydve76
Reply With Quote
Old Nov 01, 2012, 04:11 PM
Registered User
Jacques.Eloff's Avatar
United Kingdom, England, Cobham
Joined Oct 2007
541 Posts
Quote:
Originally Posted by gundamnitpete View Post
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
An alternative wing join method for the Sniper, which worked well for me, can be found in post 54:
http://www.rcgroups.com/forums/showt...1233172&page=4
Mine's still going strong. I'm on the second fuse, but the original wing is still good!

Jacques
Jacques.Eloff is online now Find More Posts by Jacques.Eloff
Last edited by Jacques.Eloff; Nov 01, 2012 at 04:59 PM.
Reply With Quote
Old Nov 01, 2012, 04:58 PM
Registered User
Jacques.Eloff's Avatar
United Kingdom, England, Cobham
Joined Oct 2007
541 Posts
Quote:
Originally Posted by capt soap View Post
Would a het f-104 make a good high speed airframe. That's what it was in real life, short distance sprinter!
I have one of these, running 9S (1800mAh) on 3W-25/Wemo Combo. Pretty quick on 1300W, and sounds great, but remember that is has long ducting which robs efficiency:
EMC 08-Sep-12: Jacques HET F-104 (4 min 1 sec)

Also, the intake shape is not great - the mock shock cones are probably causing some turbulence and further loss of efficiency.

IMO, one needs to consider nacelle-type setup or very short ducting. Erik van Schaik has some good concepts - check out his works.

Jacques
Jacques.Eloff is online now Find More Posts by Jacques.Eloff
Reply With Quote
Old Nov 01, 2012, 05:27 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,039 Posts
I beg the differ. Long smooth ducting done properly can smooth out the airflow to the fan, creating a cleaner bite. As for the nacelle goes, sometimes in a speed, not thrust, application approximately +/- 90% FSA on the INTAKE can produce a lower pressure inside the ducting actually increasing the efflux speed on the exhaust.

Just for a very "loose" comparison it is like an f15 or Sr71, or inlet cones on the F105 etc, keeping the sonic boom pressure zone, or reducing inlet air pressure on a real turbine. It has been proven it works SIMILARLY in EDF's.

Similar to a power system going faster on a 5x5" prop than a 5x5.25" prop.
Jwmflying14 is online now Find More Posts by Jwmflying14
Reply With Quote
Old Nov 01, 2012, 06:52 PM
Registered User
capt soap's Avatar
dallas tx
Joined Jun 2003
2,864 Posts
Nice 104 flight, need's 3000 watts...
capt soap is offline Find More Posts by capt soap
Reply With Quote
Old Nov 01, 2012, 07:56 PM
Current project: Electrolyte
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
5,482 Posts
Quote:
Originally Posted by Jacques.Eloff View Post

IMO, one needs to consider nacelle-type setup or very short ducting.

Jacques
The Blowdart is still the fastest 30mm edf @ 90 mph....2x as fast as the UMX Mig. Very efficient aerodynamically!
pdawg is online now Find More Posts by pdawg
Reply With Quote
Old Nov 01, 2012, 08:19 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,039 Posts
+1 on a design like that!

a V-tail would be slightly less drag as well.
Jwmflying14 is online now Find More Posts by Jwmflying14
Reply With Quote
Old Nov 01, 2012, 09:44 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,039 Posts
You might wanna tram up with someone like pdawg too. I have checked out his attachments multiple times (sorry if that's creepy?) And he has made some freakin awesome stuff.
Jwmflying14 is online now Find More Posts by Jwmflying14
Reply With Quote
Old Nov 01, 2012, 10:13 PM
Registered User
Joined Oct 2009
1,038 Posts
Quote:
Originally Posted by Jacques.Eloff View Post
I have one of these, running 9S (1800mAh) on 3W-25/Wemo Combo. Pretty quick on 1300W, and sounds great, but remember that is has long ducting which robs efficiency:
http://www.youtube.com/watch?v=-J5iB...&feature=g-upl
Also, the intake shape is not great - the mock shock cones are probably causing some turbulence and further loss of efficiency.

IMO, one needs to consider nacelle-type setup or very short ducting. Erik van Schaik has some good concepts - check out his works.

Jacques
Thats a nice flying plane, any idea on speed? Looked to be doing around 95-100mph.
nighthawk0077 is offline Find More Posts by nighthawk0077
Reply With Quote
Old Nov 01, 2012, 10:16 PM
Registered User
Joined Oct 2009
1,038 Posts
Quote:
Originally Posted by capt soap View Post
Nice 104 flight, need's 3000 watts...
lol, no it just needs a changesun fan upgrade
nighthawk0077 is offline Find More Posts by nighthawk0077
Last edited by nighthawk0077; Nov 01, 2012 at 10:32 PM.
Reply With Quote
Old Nov 01, 2012, 10:34 PM
Victim of C.D.O.
murdnunoc's Avatar
United States, TX, Lubbock
Joined Oct 2007
4,081 Posts
I haven't seen any data on a 70mm Change Sun pushing anything to 200
murdnunoc is offline Find More Posts by murdnunoc
Reply With Quote
Old Nov 01, 2012, 10:38 PM
Victim of C.D.O.
murdnunoc's Avatar
United States, TX, Lubbock
Joined Oct 2007
4,081 Posts
Quote:
Originally Posted by skydve76 View Post
Another good candidate is that HET Me-163. Batteries are tricky but its a clean airframe.
Very cool jet.
But isn't the fuselage on the bubbly side? Looks like a lot of drag, even if the wings are very slippery.
murdnunoc is offline Find More Posts by murdnunoc
Reply With Quote
Old Nov 01, 2012, 10:58 PM
Flirtin With Disaster !!
D.B. Hooper's Avatar
United States, OR, Mt Angel
Joined Jan 2008
1,430 Posts
Quote:
Originally Posted by murdnunoc View Post
Very cool jet.
But isn't the fuselage on the bubbly side? Looks like a lot of drag, even if the wings are very slippery.
Hi Murd
With one of your Mega motors and a prop the ME 163 will hit 200mph. My EDF ME 163 on 4s with the MB-1 Sapac fan unit was fun to fly but no where near 200mph. My next 163 will be the prop version using the Rocket motor off my ritewing Demon.
HET ME 162 Komit (4 min 18 sec)
D.B. Hooper is offline Find More Posts by D.B. Hooper
Reply With Quote
Old Nov 01, 2012, 11:01 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,039 Posts
murdnunoc. As far as I know CS fans aren't good for much besides thrust, and their awesome noise... The definitely are NOT a speed fan. The number one reason people have them is they sound good, number two, the 10 blades looks cool. You can produce a hell of a lot more speed with other fans, even a properly balanced Wemo.
Jwmflying14 is online now Find More Posts by Jwmflying14
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion $99 200MPH radar gun. Koo Hot Online Deals 3 Sep 21, 2012 10:19 PM
Build Log Quest for 200mph EDF carbon dart kingkyle Scratchbuilt EDFs 23 Jul 07, 2012 06:30 AM
Cool HD Video: 200mph DS Acro with Wizard at Weldon Daemon Slope 71 Feb 22, 2011 12:13 PM
Discussion My first 200mph FPV plane with video! gundamnitpete FPV Aircraft 29 Oct 14, 2009 08:44 PM
Discussion 200MPH with 200W possible? 1atlas Pusher Prop Jet Models 15 Aug 16, 2007 12:21 PM