Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Best Airframe - Conventional airframe or Delta?

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Old 01-15-2003, 07:07 PM
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Blue Skyy
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Default Best Airframe - Conventional airframe or Delta?

Which airframe is the best for Extreme Speed Prop planes? A standard conventional model design with fuse, horizontal and vertical stabs or a Delta design.

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Old 01-15-2003, 09:42 PM
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banktoturn
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Default Best Airframe - Conventional airframe or Delta?

This is a tough call. I make the assumption, perhaps mistakenly, that the 'best' Extreme Speed Prop plane would be the one that can make the biggest number on the radar gun, and still be able to turn around before it is out of radio range. Drag is the main issue here. The delta is tempting, simply because it seems to be easy to make it as a flying wing, which is generally good for reducing drag. The two worst things about the deltas that are popular right now are the exposed engines, pipes, linkages, etc., and the huge amount of wetted area ( total surface area ). Neither of these problems is inherent to a delta flying wing. The engine can be cowled, and everything else can be faired. The total wing area could be reduced dramatically. This reduction in wing area would make taking off and landing a bit trickier, and would require larger radius turns. The more conventional layout, if you are after the same kind of performance, might end up looking like a sailplane with tiny wings. It would also be a bear to take off and land, and would not turn as tight as, say, a Q500 plane, which has a lot of wing area. In turns, the delta is kind of appealing, because it really resists stall. The 'conventional' plane would be a little dicier, but, if we assume that it would have higher aspect ratio than the delta, would actually be able to turn tighter than the delta, since the maximum CL for a very low aspect ratio wing is a little lower than that of a higher aspect ratio wing.

I don't know which way to vote for all-out speed, but I personally would prefer the more conventional layout. You can do some things to enhance lift for takeoffs & landings, and probably don't need as much wing area for a given max. lift. One thing that is pretty clear to me is that there is a lot of room to beat the current generation, because none of them is truly designed for maximum speed. The pylon planes are beautiful, clean, and fast, but they are carrying too much wing area for maximum speed. This is because the pylon task is different from the Extreme Speed task, because they need to minimize time for a closed course. The deltas are fast and very maneuverable, but suffer from the problems I mentioned above. If I were going to categorize them by task, I would be tempted to call them combat planes.

I'll stick my neck out and say conventional.

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Old 01-15-2003, 09:51 PM
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Default airframes

There are many great reasons for both type of designs. I personally prefer a 'conventional' airframe, with the tail feathers a'wigglin' out back... But that's me... It's a personal thing...


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Old 01-15-2003, 11:11 PM
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Default Airframe

Blue,

Gosh, I figured if there was anyone who knew it would be you!

Seriously, you've been at this a long time. What do you think?

Personally, I believe it is the airframe with the lowest total drag. In the case of a delta you have a lot of induced drag coupled with a tremendous amount of "wetted" area or total surface in contact with air.

There are other factors. If turning the airplane is necessary, as in pylon racing, a conventional airframe probably turns better and bleeds off less airspeed. I am just guessing the drag on a delta goes way up in the turns.

For absolute top speed in a straight line? Geez, I don't know. I think it will take some kind of extreme speed competition to bring out the optimum airframe.
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Old 01-15-2003, 11:52 PM
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ChuckAuger
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I just ordered 6 sets of custom CNC cut wing cores. I got a Dust (again), I got a 'Lash...I'm gonna try a totally different approach.

And it's not a delta.
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Old 01-16-2003, 01:16 AM
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Blue Skyy
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Default Best Airframe - Conventional airframe or Delta?

Actually I have only been flying R/C 6 years this June. I flew my first .46FX Patriot with pipe in August the same year. Crashed my first plane (the Patriot) on December, Friday the 13th of that same year. (bounced landing to 4ft in the air, stalled and crash!) I didn't really try to fly anything what I would call fast fast until about 1 year later. I've tried something more conventional with the Patriot and Jett .90, but it wasn't even up to 200mph. It took radical dives to get up to a relatively high speed with 12" pitch props and 300' long scary takeoffs. (running out of runway and still just getting the plane off the deck)

I've also tried other types of self designed models with high wing loading and lots of HP, but still "Drag" is the overwhelming factor. Two years ago I went into building the foam core Deltas. I've had one Shrike, no Diamond Dusts. Last year I worked on 2 larger foam core deltas in the .91 size, one with a Jett .90 another with a ducted fan engine in attempt to break into this 200+ speed barrier in a serious way. I like to also fly things no one else flys. I'm not a follow the pack kind of guy. I also like to design, build and see if it will fly. Like my pusher "SST" which lasted one flight, but It sure was a sweet rush!

The pet project I'm working on now is a Jett .50 Delta with a 32" WS and it will contain a GPS for taking speed and hence drag measurements with each successive modification to see how in real flight a progressive approach to drag reduction translates to the Delta design. I've incorporated removable winglets to test out the drag reduction theories on model aircraft. I also plan to test the drag of using a fiberglass cowl, control rod fairings on the Elevons and things like that. This plane is currently weighing in at 2.75 lbs without the 5.5 oz GPS unit.

I would like to try the same approach on a Conventional wing and tail type plane someday unless someone else is looking at this concept and already knows something. If someone else has experimented with the two designs and has hard facts about the two designs, I would really be interested in the findings they have made as would others I'm sure.

I'm interested in Straight line Prop Speed planes. Pylon is a refined science. Everyone already knows what works there. How about Extreme Prop Planes? No turns, just like a drag car, go staight line as fast as you can.

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Old 01-16-2003, 01:39 AM
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Default Best Airframe - Conventional airframe or Delta?

Here is my attempt at a speed plane. The photo was taken before it was finished. It does about 140 (estimated) with a piped TT40 pro. Weight is between 4 and 4.5 lbs. Its the fastest plane I have ever flown and the fastest in my club.

The unfortunate thing about R/C extreme prop planes is you need to turn them fairly often. I can only fly my plane for about 4 seconds in straight and level flight before I need to turn it around.
I don't turn it tight and it doesn't lose to much speed in the turns.
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Old 01-16-2003, 01:56 AM
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Default Perceptions...

Originally posted by Blue Skyy
.

I would like to try the same approach on a Conventional wing and tail type plane someday unless someone else is looking at this concept and already knows something.
Well that's what I'm going for, but I know nothing about speed, don't have a radar gun, so that's where that will end...I'm sure any design I come up with won't be worth copying..., I'm Team Nobody, Nobody's Hall of Fame.


I'm interested in Straight line Prop Speed planes. Pylon is a refined science. Everyone already knows what works there. How about Extreme Prop Planes? No turns, just like a drag car, go staight line as fast as you can.
Me too.

Blue Skyy
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Old 01-16-2003, 04:42 AM
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Default Best Airframe - Conventional airframe or Delta?

Blue Skyy,

Good approach. Forget the winglets. The only way they will reduce drag is if they reduce induced drag. Induced drag is negligible at high speed, so you will only add wetted area with winglets, which is pure loss.

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Old 01-16-2003, 05:24 AM
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Default hmmmmmmm

Designed my first Dedicated RC speed plane (not a pylon racer) in the late 80's. Too many designs since then to count, but my personal experience has shown me again and again (from my own delta and conventional designs and the same designs of others) that the conventional design has more potential for ultimate speed.

The other thing I picked up is that getting the most of an airplane when your goal is speed is made of two parts- good airframe design and attention to details. If you want to go fast, you have to conceal or streamline every linkage, engine part, switch, etc.

If you don't address the airframe and the details, all the power/rpms in the world won't get you there.
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Old 01-16-2003, 01:27 PM
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Default Re: hmmmmmmm

Originally posted by matchlessaero
[B

If you don't address the airframe and the details, all the power/rpms in the world won't get you there. [/B]
You've got it all in a nutshell there man...
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Old 01-16-2003, 05:38 PM
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Default Best Airframe - Conventional airframe or Delta?

The jets always look better than a Delta, becides, they are easier to see too.
I've got a brain plan, its its like nothing else out there. low drag is the answer, tho it will increase my weight, hope that helps on dives
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Old 08-23-2004, 10:29 PM
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Default RE: Best Airframe - Conventional airframe or Delta?

I have found that it is easyer to build a light weight / high strength airframes with a delta configuration.
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Old 08-23-2004, 11:00 PM
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Default RE: Best Airframe - Conventional airframe or Delta?

Can't you just take an FAI pylon plane and clip the wings a little? Maybe a slighly thinner airfoil?

Obviously I have no idea what I am talking about (see my other 2K posts [X(]) but wouldn't you start with a known 200 MPH plane and remove the characteristics that make it turn well?

The fastest propplane I have flown is a Scatcat/Jett-50 or my WHip but nowhere near y'all speeds---
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Old 08-24-2004, 01:51 AM
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Default RE: Best Airframe - Conventional airframe or Delta?


Can't you just take an FAI pylon plane and clip the wings a little?
Yes Razor, but a good FAI F3D kit costs at least 500 bucks.

Maybe a slighly thinner airfoil?
No, not mandatory. Better choose a different

Here's a true 220 mph + speed plane:
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Old 08-24-2004, 06:48 AM
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Default RE: Best Airframe - Conventional airframe or Delta?

der_steuermann,
I've seen that design in this forum before and there was mention that it was going to be kitted in 2 different sizes.
Can you give me more information?

Thanks,
Pat
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Old 08-24-2004, 10:11 AM
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Default RE: Perceptions...

ORIGINAL: ChuckAuger

..... I'm Team Nobody, Nobody's Hall of Fame.
I think I still have ya in there Chuck http://www.jettengineering.com/hall/index.html
Just to make sure ya still aren't forgotten !
(although I REALLLLLLY have to finish the new version of the HoF SOON!!!!)


Bob
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