If you were going to design a Q-40 with an inverted engine, what would you do about potential engine damage on nose down landings?

Or do you just design the plane so that the engine is rotated down and let the muffler take the punishment?

Accept the fact that you'll have a scuffed head. That's what I'd do.

What's the difference--head or muffler, take your pick.

John,

I would be concerned that rubbing the head would cause minute changes in the head seal.

Now you know I'm thinking about how to do the Firecracker.

SMOOTHIE! SMOOTHIE!

Think about it ... nose-overs wouldn't hurt anything. Open venturi on top, where it belongs. Startup would be just like on the bench. You could mount the tank high in the fuselage, behind the engine cylinder -- no starving out in the turns.

Muffler hangs out on the starboard side, nothing to cut away, no interference with the wing or landing gear.

Fairing behind the engine cylinder is a no-brainer. Just look at the 3-view.

Use wire struts for your landing gear if you want -- it's scale. No pants -- that's scale too.

That slab-sided fuselage could be made out of wood, just like a Quickie. Plenty of side area to secure the firewall. It's clean without fillets. The launching handle (excuse me, vertical fin) is short & stout. Need I go on?

Dang it, if you don't build one, I will.

Major Woody

Major Woody,

Wouldn't the spinner then be subject to damage on nose overs? I guess you could design the bottom of the nose so that it protects the spinner, and put a 1/16" wire skid on the surface of the bottom. I'll start drawing and see where the damage zone would be.

So far I haven't found good info on the Mr. Smoothie, but I did find a free flight model of it. Scan the 3 view if you can, and email it to me.

I'm going to start with the Hughes Racer with a reduced size cowl. But I'm up to trying some other stuff, especially if the foam plug technique works out. I'm going to start working on drawing up a Firecracker, and see what that yields. It's too bad that the 5" height requirement has to be met in the wing saddle area. You have to stretch the cockpit forward on most of the Thompson Trophy racers.

The Swee' Pea wing has some dihedral in it. Would that cause a problem on the Mr. Smoothie?

For the last F3D World Chamionships we all rushed out and purchased Henry's latest F3D engine. It was a front intake, rear exhaust. all of our engine installations were inverted. We could not always practice on paved runways. We soon realised that this engine with the huge venturi was a very efficient vacuum cleaner. For sucking up dirt it had hoover beaten by miles.

Don, do not do it.

Ed S

I agree with Ed.

Unless you landed it in the middle of the paved runway, you would be constantly sucking dirt and dust through the venturi. Much worse, than if the engine was upright. You can't close the Barrel on Q40 engines like a quickee on landing. You would be replacing pistons and sleeves all to often. In my opinion, a bad idea.

Don,

Before they eliminated the replica rule in F3D, I used "Mr. Smoothie" as a prototype and it worked out great. (This was 1993, I believe.) Keith Shaw sent me a bunch of good documentation; I'll dig it up and send it to you FWIW.

Dihdral on a midwing is generally not good -- it makes the rudder extremely sensitive & you may get into some nasty Dutch roll action. But the Swee'Pea wing looks pretty flat to me; it may be fine. Just start with less rudder throw rather than more.

Ed,

You guys all laughed at my funky airplane down there at Phoenix, but it ran like a clock & didn't eat any gravel. As a result, while you may have had to replace pistons & sleeves, I still have two pristine Nelson F.I.R.E. .40s sitting at home, with a combined value of at least $30. So nyah!

The Boy of Donna Summer

Hey Prima Donna,

I've started on the Hughes Racer. Whadda ya think about it so far?

Go ahead and send me the info when you get a chance. I found a FF model, and on the page that links to that model, there is a side view that looks like it is from the 3 view.

From that side view a couple of things come up. By the time the wing is moved forward enough, the tank will be well below the venturi, because you won't be able to get a tank between the firewall and the wing. Also, the spinner will be in harms way on nose overs, and I can't see any way of making that not a problem. It looks like you would need to have a nose skid wire.

What is your opinion on the two issues above.

If I did one, I would do it with a new wing. A flat wing is pretty easy to do, and I would use a NACA 66 wing.

Mr Pylon World

Don,

It looks great with the smaller cowl. I would make the corners just as smooth and round and gentle as possible (think Rare Bear). It might still be a losing battle with the frontal area, but at least you're putting up a valiant fight. Perhaps in this case a larger spinner wouldn't be so bad (think Rare Bear). The goal would be to make the front end as spherical as possible, with the air diverted around the sides instead of whamming into the front.

Propeller design may play a role. It's no secret that some props work better on some designs than on others. The old Denight Special F1 model was known as a dog because of its large, bulbous cheeks, until a few unusually smart Denight owners started making props with a little more diameter, more pitch and blade area out at the tip, and a lot less in near the hub. Since the air near the fuselage was going to hit those cheeks and stall anyway, there was no point wasting the energy to accelerate it.

On the Smoothie, if you want to make the nose extremely short, you may have to cut a notch out of the front of the wing to accommodate the tank. That means make sure you have a good spar. Or, if Ed Smith is to be believed (never a foregone conclusion), a Jett or Tettra tank on the bottom of the fuselage could work out just fine.

I wouldn't worry too much about nose-overs. If you get the landing gear position right, it won't bounce that much. Or, use an APC prop and have it stop straight up and down, so you can use it as a skid.

Vincent da Chinscoop

Mr Chinscoop,

I was already thinking about being able to run a Q-500 timed engine with a Q-500 prop like an 8.75 x 9.25 ... but I don't think that would be legal ... I haven't seen the composite prop rule yet. But for Q-40 Sport with a TT Pro 40 and a 9 x 6, it should do well.

Even though I'm setting it up for a 1.5" spinner, a 1.75" could be used. The front edge of the cowl will be very rounded, but I plan to leave enough of the rear edge to get approval. If they come back and say I can change the cowl shape, it will be easy to do.

I've got to make a Swee' Pea wing for somebody this week, so I'll have one to fit it to. I should be making the H-1 mold by next week at the latest.

Mr Speedy

The Golden Age Racers page has this side view of the Mr Smoothie. Is it about right?

Don,

That looks just right to me ... the tiny canopy bump makes it pretty obvious why nobody built one before, when all Q40s had to be 6 inches high at the cockpit -- not just the Mustang-ish ones with belly scoops.

Note also, there's a little curvature underneath the engine. Play your cards right and you might never actually touch the spinner to the runway.

DHG

Don,

I wouldn't worry about the spinner. THE AIRPLANE SHOULDN'T BE ON IT'S NOSE!

Big kudos for the "prima Donna". I just got it! Sometimes Duane is too smart for his own good.

With the bubbless tanks I don't think tank location is as critical as it was before. The Jett CG tank should be perfect. It is flat and compact. You shouldn't have to notch anything.

I agree that the 5" rule has opened the door to different choices in airplane design. There are several out there.

I honestly, don't know how you do it. How much sleep do you get? It sounds like you don't need another project. Duane you have an abundance of time you do the Smoothie.

Dan

Don,

The way I read the rules, using a Quickie motor spinning a bigger prop is perfectly legal for 422. You'd have to use a wooden prop though. Like you, I haven't seen the full text of the new CF prop rule so I don't know how that would apply but I'm pretty sure the rule states that it is just that one prop, in just that one size. It'd be too small for the 428 motor.

I've thought about this too and I wonder what kind of reaction I'd get if I went to a big contest like one of the Gold Cup races with a quickie motor hanging on the front of my Q40.

Turning a bigger prop would be a good way to limit the top end speed some.

As for the Thunder Tiger, as long as the muffler meets the dimensions specified in the rules (I'm pretty sure it does) and you use a wooden prop, this would be legal too. What kind of reaction would THAT get you?