base drag visualization

[aerohead]

Originally Posted by freebeard

That's why they have classes.

Accepting the limitation is what makes it art. What I'm thinking of is a belly tank with the VW boxer cylinders and heads sticking out of the nose like a light-plane with no propellor, front wheel drive like the XR-3, long axles with tall, narrow, rock-hard front tires for traction, a reclining cockpit like an F1 car, and the two rear wheels in tandem, (like the Speed Demon has in front). If you could get any traction, it would go real good.

If the rear wheels need to be open, it could be done similar to the Junker G.38 landing gear.

Hoerner has some data on fuselage drag as a function of various perturbing structures petruding out,or openings cut in.I'll look at that.
The lakester would be a fun ride! Fast too.

on.

[freebeard]

Darn it. I edited the previous post because I didn't notice aerohead had replied on the 2nd page (and I don't like to reply to myself). So, see above.

Plus which, it's a Lakester not a belly-tank.

[Jasen]

Originally Posted by freebeard

and the two rear wheels in tandem, (like the Speed Demon has in front).

I don't understand why tandem rear wheels. Is it for pour weather traction while making turns.

[freebeard]

It's to make it a 4-wheel vehicle. Else it would be a reverse trike and run in an motorcycle class. Most Lakesters have half of the increase in drag coming from the rear wheels.

The front wheels have spokes so they don't act like rudders on the wrong end.

[Jasen]

Originally Posted by freebeard

It's to make it a 4-wheel vehicle. Else it would be a reverse trike and run in an motorcycle class. Most Lakesters have half of the increase in drag coming from the rear wheels.

The front wheels have spokes so they don't act like rudders on the wrong end.

Got it

[aerohead]

Originally Posted by aerohead

Hoerner has some data on fuselage drag as a function of various perturbing structures petruding out,or openings cut in.I'll look at that.
The lakester would be a fun ride! Fast too.

on.

I finally have Hoerner's data and I'll present it as he presented it:
*bare fuselage.......................................... ............ Cd 0.08
*with opening and pilot........................................... Cd 0.15
*with windshield........................................ ............ Cd 0.20
*with cockpit and engine (radial).............................. Cd 0.37
The VW heads won't disturb like a radial ( more like a J-3 Cub ) but will degrade the Cd.Not much to go on.

[sendler]

It's hard to know why the windshield make drag worse without a picture.

[freebeard]

The VW heads won't disturb like a radial ( more like a J-3 Cub ) but will degrade the Cd.

That's quite a jump in Cd. Assume 5-7 cylinders, that's 2 1/2 to 3 1/2 times the frontal area of 2 tandem cylinders, twice. So 0.22 becomes 0.07 increase?

That's not so bad and where the Cub has a narrow cabin. the eco-lakester would have the cylinders at the stagnation point of a bluff body with 10:1 blister recesses to capture, channel and reattach the turbulence.

I'm going out to the country to work on the VLVW but I'm starting to think that everything it needs—powertrain, wheels/tires and roll cage would get better results in a purpose-built body.

[aerohead]

Originally Posted by freebeard

That's quite a jump in Cd. Assume 5-7 cylinders, that's 2 1/2 to 3 1/2 times the frontal area of 2 tandem cylinders, twice. So 0.22 becomes 0.07 increase?

That's not so bad and where the Cub has a narrow cabin. the eco-lakester would have the cylinders at the stagnation point of a bluff body with 10:1 blister recesses to capture, channel and reattach the turbulence.

I'm going out to the country to work on the VLVW but I'm starting to think that everything it needs—powertrain, wheels/tires and roll cage would get better results in a purpose-built body.

I wouldn't know how to proceed without doing the same logic.Just taking a percentage of the disruption.
If a streamlined forced-air duct covered the heads,fed from a ram-air inlet the 'blisters' could have as low as Cd 0.10 according to one of Hoerner's armament turret data.
Adding the ideal canopy to the fuselage adds 0.007 to the overall drag of a L/D= 8.5 Cd 0.082 fuselage.It looks like the heads could have a very minor impact.
You'd have two very small 'canopies'.

[aerohead]

Originally Posted by sendler

It's hard to know why the windshield make drag worse without a picture.

Imagine scooping out a hole to create the cockpit,then attaching a flat screen angled up very steeply,with no curvature or radii at all.And no turtledeck head fairing behind the pilots head to assist in cleaning up the disturbance.
Like a 1950s British convertible sports car with Cd 0.70-75.
I'll try an get an image scanned Saturday when I come in.