Go Back  RCU Forums > RC Airplanes > Extreme Speed Prop Planes
Reload this Page >

To Delta or not to Delta that is the question!

Notices
Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)
View Poll Results: A poll
Delta
54.84%
Conventional
45.16%
Voters: 31. You may not vote on this poll

To Delta or not to Delta that is the question!

Old 05-16-2010, 12:27 PM
  #1  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default To Delta or not to Delta that is the question!

I'm thinking of building a speed plane for my incoming OPS 67.

I have no doubt that a delta plane (something along the lines of a SD with a full length cowl) would be easier to build than a conventional plane. The real question is this: given a similar power source (say - tractor OPS 67) what would be faster, a delta or a conventional?

I'm thinking that the induced drag plays almost no role at top speed. The parasite drag seems much more important. If this is the case a conventional shouldn't have any advantage over a delta. But still, I have a feeling that a conventional plane would be faster.

Would the longer chords of the delta cause more drag since more of the wetted area experiences turbulent flow? (assuming good surface finish) Or would the lighter weight of the delta allow a smaller wing? Questions questions questions...


Appreciate your thoughts.
Old 05-16-2010, 02:16 PM
  #2  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

I think it's been proven already that a Screamin' Demon will go at least 98% as fast as the most sophisticated pylon racers using the same engine. The SD is obviously much less time and effort.
So, the choice also boils down to your own personal capabilities, resources, etc. The SD type plane makes a great "gateway" project into the world of speed. I'm satisfied with the results of going the delta route, but also curious about other approaches.
Old 05-16-2010, 10:17 PM
  #3  
soarrich
My Feedback: (98)
 
soarrich's Avatar
 
Join Date: Feb 2002
Location: Middletown, NJ
Posts: 4,676
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

Like CP said the delta is 98% as fast, so the fastest is the conventional layout.
Old 05-17-2010, 08:59 AM
  #4  
evan-RCU
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,913
Likes: 0
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

I don't agree with the 98% number. A delta is quite a bit more draggy. But in the real world most of us live in a delta is more practical to build and fly.
Old 05-17-2010, 09:06 AM
  #5  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

Evan, what's the highest speed you ever heard of a Nelson powered FAI plane hitting?

The number that I recall hearing from Henry himself is 207 mph.
Old 05-17-2010, 09:58 AM
  #6  
evan-RCU
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,913
Likes: 0
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

F3D? I recall 230...

But that was for a legal racer.
Old 05-17-2010, 10:34 AM
  #7  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

The MB .40 powered racers just made big news at last years World Champs for hitting 210-211.....but that's with a MB .40, not a Nelson .40.

I got a SD up to 202 which is .975xxxx of the number Henry told me back in 2006, when I asked him at the time if he thought one of his engines could get a Diamond Dust past 200.

I've also taken a K&B 6.5 Formula One engine and did 177 mph with a scratch build DD. This speed is "right there" with what the most advanced racers were hitting back in the day.
Old 05-17-2010, 01:47 PM
  #8  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

I think I like CP's advice.

Reminds me of an old joke. A mathematician and an engineer are shown to a room where there's a beautiful girl at the other end. They're told they can do whatever they want as long as they advance only half the distance to the girl with each step. The engineer starts jumping like a madman. While the mathematician stays put. He calls out to the engineer: "Hey, you know you'll never reach the end of the room don't ya?" The engineer answers back: "Yeah, but I'll get close enough!".

Looks like close enough it is for me too
Look at what I just got from the mail!
Old 05-17-2010, 02:00 PM
  #9  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

Looks like enough power.......[:-]!

The .60s in the Screamin' Demons haven't had a lot of action just yet. If you can wait just a little bit longer, some flight reports should be coming in.

If you've got the money, or the ambition to build your own, a purpose built conventional plane obviously gets the job done. ILJ presented a nice thread here [and at RCG] a couple years ago that showed several options.

Old 05-17-2010, 02:45 PM
  #10  
evan-RCU
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,913
Likes: 0
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

How do you convert a RIFE marine motor to an airplane motor?


CP, though I don't agree with the 98% number I did vote delta and think it is a more real world answer.
Old 05-17-2010, 02:57 PM
  #11  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

Ha!

I'm still waiting for MJD to fly his 65 SD. Somehow doing 200 with a turbine powered plane seems less scary [X(]


Evan, with the OPS's it's really easy. You swap the front and back parts and either turn or buy a thrust washer.
Old 05-17-2010, 03:20 PM
  #12  
evan-RCU
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,913
Likes: 0
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

Is the porting the same both ways? I thought there was a rotary valve in the OPS so it only went one way.
Old 05-17-2010, 03:54 PM
  #13  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

When you switch between front and back the porting stays the same. It can also be altered for reverse operation. The cylinder and piston themselves do not change.
Old 05-17-2010, 11:09 PM
  #14  
freakingfast
Senior Member
My Feedback: (3)
 
Join Date: Jan 2005
Location: Mather, CA
Posts: 2,222
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

Deltas/flying wings are very efficient.....in a strait line. They do scrub off a lot of speed in a tight turn, such as a race course. But if you can come out of a dive to kick in some extra speed to make a speed pass more impressive than just about anything, go with a delta.
Old 05-17-2010, 11:45 PM
  #15  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

Well, the Germans found the delta's limitations as far as setting speed records goes. ILJ showed photos of a couple pretty slick deltas that they ran way back when.

It'll be interesting to see what pans out with the big block deltas that are due any day now.
Old 05-18-2010, 12:19 AM
  #16  
HighPlains
My Feedback: (1)
 
Join Date: Mar 2003
Location: Over da rainbow, KS
Posts: 5,087
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

Deltas/flying wings are very efficient.....in a strait line. They do scrub off a lot of speed in a tight turn, such as a race course. But if you can come out of a dive to kick in some extra speed to make a speed pass more impressive than just about anything, go with a delta.
Pulling out of a dive they lose speed too, nothing straight about it.

There have been a number of reports of F3d planes hitting around 220 with a slight dive.
Old 05-18-2010, 09:44 AM
  #17  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,657
Likes: 0
Received 1 Like on 1 Post
Default RE: To Delta or not to Delta that is the question!

RVman's OS .77 Demon has flown once, no startling news other than it flies fine, is really fast even with the sawed off Zinger wood prop, and torques hard on launch. I launched his Picco .45 DF Demon and it was a rocket, and he commented the .77 was noticably quicker onjust that one test flight. So the news is promising.

I think the point of the project is that while it may not be as efficient as a conventional layout, it's a $70 kit with a $150 eBay DF engine plus accoutrements, and it has >200 potential. That formula works for me. If I vaporize it with a dumb thumb moment, I haven't broken the bank.

MJD
Old 05-18-2010, 10:35 AM
  #18  
mk1spitfire
Senior Member
 
mk1spitfire's Avatar
 
Join Date: Oct 2007
Location: south, UNITED KINGDOM
Posts: 1,208
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

The bigger wing area on the delta is easier to see, Bit more tricky for launches, if can't grab the Fuz. Still a wow factor seeing the trangle shape hall ass.
They don't stall like convential, kind of mush up when you go slow but who wants to go slow but hey you got to unfortuantlely land at some point.
If you don't have a delta, then try one, I'm sure it will stay in your speed collection of planes, it may dominate the others.

I wish Evan would bring his twin bandito delta out more for all to see and hear in video.
Old 05-18-2010, 11:01 AM
  #19  
evan-RCU
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,913
Likes: 0
Received 2 Likes on 2 Posts
Default RE: To Delta or not to Delta that is the question!

I need to sell the Banditos to someone that would fly it more often....
Old 05-18-2010, 12:29 PM
  #20  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

Just for the heck of it I ran some numbers through Profili... Both NACA 0006 and MH 5X (speed profiles) come into their own at a Re of 1,600,000. This translates to wing chords of 30cm (12") or more at 200mph. So even a conventional planform would have a short stubby wing. A longer wing would actually have more friction drag.


Delta it is!
Old 05-18-2010, 12:54 PM
  #21  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!

It would be cool to see a delta finished with the Israeli AirForce markings and desert camoflage....but it might be a challenge to see?
Attached Thumbnails Click image for larger version

Name:	Wu60722.jpg
Views:	10
Size:	79.7 KB
ID:	1438404  
Old 05-18-2010, 05:30 PM
  #22  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,657
Likes: 0
Received 1 Like on 1 Post
Default RE: To Delta or not to Delta that is the question!


ORIGINAL: erazz

Just for the heck of it I ran some numbers through Profili... Both NACA 0006 and MH 5X (speed profiles) come into their own at a Re of 1,600,000. This translates to wing chords of 30cm (12'') or more at 200mph. So even a conventional planform would have a short stubby wing. A longer wing would actually have more friction drag.


Delta it is!
You'll see lower aspect ratio wings than you might expect on some European speed models. I generated a table of wing chord, airspeed, and Reynolds number for each of the MH5x series as a guide when designing a couple of speed models.

MJD
Old 05-18-2010, 09:07 PM
  #23  
iflyg450
 
Join Date: Jul 2006
Location: townsend, GA
Posts: 927
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!

Yup a delta my not be the fastest but they always get respect at the field. Who doesn't love a wedgiee screaming around the field.
Old 05-18-2010, 10:17 PM
  #24  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default RE: To Delta or not to Delta that is the question!


ORIGINAL: iflyg450
Who doesn't love a wedgiee screaming around the field.
Well for starters, how 'bout the guys who dive under the picnic tables?

I'd like to show up at the local club field with one, but they've got a strict noise standard.

The real truth is.....stuff like this scares the piss out of them.


Old 05-19-2010, 01:09 AM
  #25  
erazz
Senior Member
Thread Starter
 
Join Date: May 2003
Location: NA, NJ
Posts: 398
Likes: 0
Received 0 Likes on 0 Posts
Default RE: To Delta or not to Delta that is the question!


ORIGINAL: combatpigg

The real truth is.....stuff like this scares the piss out of them.
Scares it outta me too [:-]

I think I like the scheme you suggested. I've actually had a DF Nesher (predecessor of the Kfir) with that scheme and it was very visible.

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.