# Torpedos with Wings - race plane

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Starman, Mar 14, 2014.

1. Apr 9, 2014

### delta

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I have been interested in motor gliders for quite awhile, but these days I'm a little more into speed and utility which includes something you can take off and land just about anywhere, camp in when you get there, and drive through weather. This is about the highest aspect ration one I've dinked with, and it'd have a front engine. The symmetrical airfoil that a delta requires precludes building anything that will have a 60 to 1 glide ratio. I'd make me happy to be able to scoot around on 25hp though.

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2. Apr 9, 2014

### Starman

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Those are nice shapes, and fast looking too, could you make one with a more indented trailing edge, like a Vulcan has, with the prop on the tailcone? onder:

3. Apr 9, 2014

### delta

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What is it going to take to make a race winner? Build your propulsion system, send me the spects, and I'll help you design an airframe around it. It may or may not have to look like a vulcan.

4. Apr 9, 2014

### Starman

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Sorry, I can't build anything like that cuz I spent all my money building a Taoist hermitage (like a Buddhist monastery only more casual, a lot more casual) in the high mountain wilderness of Ecuador and it's not finished yet.

A monster V8 without blowers cost $100,000 and I couldn't find out how much a Keith Black race hemi costs without blowers. I'm just lending my special 'talents' to whoever has the vision to see what it is that I'm seeing. Nor do I have the engineering training to crunch numbers like you guys, I can't figure out the ideal diameter for a direct drive prop fan, etc. Since I'm borderline Aspergers/normal, which is borderline autistic, after sixty years of studying aerodynamics and drawing the results I have a tendency to 'feel' the right answer. I can hit targets in the dark or with my eyes closed, zen master style, and a lot of times, if I spend some quality time feeling out a design it frequently happens to be right on the numbers when someone checks the numbers. So if anyone with money is inspired by these ideas then I'll be happy to lend some more detailed free advice =) As it says in the classics, the master stays on the straight path but most people love to get sidetracked by detours. We have to wait till I get my computer charger shipped and then I'll draw you all a picture of that Vulcan bomber model sized plane with a V8 in it and a two seat sailplane cockpit in front, all balanced and showing the parts locations and ... Last edited: Apr 9, 2014 5. Apr 9, 2014 ### Starman ### Starman #### Well-Known Member Joined: May 17, 2009 Messages: 2,011 Likes Received: 61 Location: High in the Andes Mountains Just want to add here that Xanadrone's tri motor racer has already been well designed, by Jay Kempf. It's also a torpedo with wings, designed for speed. Just put the V8 behind the cockpit instead of the outboard motor, and put the two Hayabusas at the front of the booms to balance it out, another possible winner ~ disclaimer: may need some added stiffness. 6. Apr 9, 2014 ### delta ### delta #### Well-Known Member Joined: May 27, 2011 Messages: 1,954 Likes Received: 197 Location: Brookside Utah Why not blowers grasshopper!!! Chevy Twin 541's Some of us like to speed faster from where we've always been, knowing there's no where we are not already... 7. Apr 9, 2014 ### markgrue ### markgrue #### Member Joined: Jan 25, 2014 Messages: 21 Likes Received: 6 Location: Valmeyer, il I like the design with a pair of small block 431s putting out about 900 or 1000 hp each like any top of the line dirt late model stock car. weigh less then 400 lbs each and run a good ducted fan from each one. The ducted fan is not a shrouded propeller like a lot of them I have seen. It must have a good diverging duct to the fan with at least 90% solidity and then a choked duct behind it with at least a pressure ratio of 2.2. It should be able to produce about 1400 lbs of thrust per side at 400 kts if designed properly. I don't have references in front of me since I am in Germany right now but I will look for them. With a good low drag airframe it should be capable of winning times. Of course this is just my opinion but I think it is sound Mark 8. Apr 9, 2014 ### Jay Kempf ### Jay Kempf #### Well-Known MemberLifetime Supporter Joined: Apr 13, 2009 Messages: 3,702 Likes Received: 962 Location: Warren, VT USA At what RPM? Both the motor at that HP and the shaft RPM of the ducted fan? I assume it would be loud but in a different way than say an unlimited Reno Racer. Seems like it wouldnn't be able to accelerate at the rate of a large CV prop but the idea of a high velocity or variable exit velocity might be interesting in terms of speed runs. 9. Apr 9, 2014 ### Starman ### Starman #### Well-Known Member Joined: May 17, 2009 Messages: 2,011 Likes Received: 61 Location: High in the Andes Mountains One thing about a ducted fan on a pusher torpedo is that you need surface area at the back anyway, so the duct may not produce any drag penalty, but ducts are mainlhy good for slower speeds, arent' they, so why bother? Nice, is that$25K for each engine or for both. No matter, even if it's for one I bet if you stuck one of those in that model Vulcan it would also beat the unlimiteds, and you might just be able to run it direct drive, and it would be affordable ... for some people. You could no doubt run it direct drive if you put two of those together on one shaft. Ah, the sweet sound of a supercharged V8. A supercharger would be a lot easier to set up than most turbos, unless you know the special turbo secret.

10. Apr 9, 2014

### Starman

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The special turbo secret is this. You don't need to mess around with a dirty old heavy old stinky old unreliable waste gates. All you need to do is put a restrictor upstream of the compressor. That will absolutely limit the top boost available and it is also automatically altitude compensating. Not good for cars because it's slower to spool up, it's no problem for aircraft. So instead of all the plumbing and junk all you need is a little metal disc with the right sized hole in it in the intake upstream of the compressor.

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11. Apr 9, 2014

### Starman

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Delta, those wings you have look really fast and give nothing away in the top speed department. Maybe good for flying cars, but they would have a hell of a 'backside of the power curve' problem, particularly with a small diameter prop. I think it should have a little more span in order to provide passable lift at slower speeds and make it safer and more practical.

The Vulcan bomber has a similar span loading to the B52, but it gives nothing away in induced drag due to low AR and much bigger wing it has because the wing is flying at such a low lift coefficient.

Those kinds of wing curves you have are ideal for the way the vortexes would progress smoothly and predictably forward as the AOA increased, but to increase the aspect ration you can still use the same style of flat wrap curves you like but make the wing into a heart shape so the top view is like a valentine's heart. That will get the prop in closer to the cg and make rotation easier.

12. Apr 10, 2014

### delta

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Race planes are going to take a special breed of pilot to keep 'em safe. The one I'm building will have a high enough wing loading, but nothing like the one I'd build for racing. They fly 104's don't they... I've got some wild and crazy ideas, but when push comes to shove I'll have something under me that I think I can handle, and whether or not I can is another chapter. Here's a few no go ideas...

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13. Apr 10, 2014

### markgrue

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They make max horsepower about 8 or 9k. Use a direct drive to the fan. You are correct in that static thrust would not be good. Since the races are from a running start the inlet would be designed for that speed range. A variable area nozzle would help a lot in that regard.

Mark

14. Apr 10, 2014

### markgrue

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The shrouded propeller is low speed system. It does not have a choked exit duct. It also does not have the long inlet duct to recover the pressure in the free stream to the inlet. A ducted fan is a high pressure system where a shrouded prop is a low pressure system. At the speeds the unlimited racers are running a prop has about reached its limit. The tips are running in the transonic range and the tip losses are getting very high. A ducted fan does not suffer from such problems.

The problem with superchargers is they are heavy and suck up a lot of power. Hence the big wide belt to drive them. They are designed for instant response. The turbo is a much better fit for aircraft. Don't need the instant response and they are much lighter.

Mark

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15. Apr 10, 2014

### Jay Kempf

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8-9k seems like a lot. Let's say 3-4' diameter duct that's means that most of the blade will be significantly compressed not to mention the radial forces. Not sure that it could be made to flow in any stable manner or achieve a high enough compression ratio to support a constriction for higher exit velocity. So multi-stage might be necessary. I have never seen one of those.

Check out the ducted fan aircraft thread. That is two ducts off of one V8.

16. Apr 10, 2014

### Starman

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A proper ducted fan with a long intake duct for pressure recovery could be arranged pretty easily on one of those deltas if you use a long enough shaft to get the engine completely out of the duct which is also easy. An adjustable outlet nozzle wouldn't be too hard if you went from round to square on a longish outlet (more tail area), then it could be a Mustang style cooling outlet door.

Afterburners are against the rules.

I think what would happen, if a plane like this was built, is that if you put just about any big racing V8 in just about any of these torpedoes with wings that it will beat the unlimiteds.

It's only later, when they start racing each other that things like Hemis, monster motors, or ducts on the fans will be needed to up the power; so ... might as well keep it simple in the beginning with a direct drive to a propfan with any old off the shelf racing V8 to blow the doors off the unlimiteds, just to help poke a sharp stick in their eye, and then worry about refinements later.

As brought up on other threads, a Learjet fan takes 2000 hp @ 15000 rpm, and puts out 70% of the thrust of the engine, forty blades at \$1000 each.

Last edited: Apr 10, 2014
17. Apr 10, 2014

### Starman

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A nice ducted fan on a delta offers the racer a chance to run at transonic speeds, maybe even supersonic in a dive :gig:

I can envision that in the future some of these racers will look a lot like F-16s (single duct) or even twin duct as in F whatever

Last edited: Apr 10, 2014
18. Apr 10, 2014

### delta

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I made a 5 pointed RC once that worked quite well. It had a front engine, but a counter rotating ducted system should work...

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19. Apr 10, 2014

### Doggzilla

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This makes me want to release some four letter words. Freaking outstanding! Really.

Can you do me a big favor and remodel this with long, thin, swept rutan landing gear on the wingtips? The kind that the Quickie uses...just longer to clear that rear prop.

It would be absolutely outstanding with rutan gear and a pair of briggs and stratton 15hp engines like the DA-11 uses:

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20. Apr 10, 2014

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