Airfoil selection for an aircraft out there?

[Riggerrob]

We are thinking of adding a ballistic recovery for that reason. Also, a redesign could incorporate a seat that accommodates a softie parachute and is slightly adjustable.

The simplest way to accommodate a pilot emergency parachute is to delete the seat back. Install the seat bottom as per the plans, but extend it all the way back to the cockpit's rear bulkhead. This will leave a large, wedge-shaped space to install a PEP. A side benefit is increased leg room. All the major manufacturers (Butler, Para-Phernalia, Strong, etc.) make wedge versions of their PEPs. When not wearing your PEP, just Velcro in a wedge-shaped cushion.

 

[PiperCruisin]

So, who is flying the S8036 and how does it perform in the real world?

No idea. Just an example. Although it seems pretty good. I think it was made for an R/C airplane. As far as in the real world, Ribblet's stuff was not real world until someone tried it.

One thing I was showing was the graph that shows cl/cd vs cl so one can check L/D for a target cl. 3V152 made that addition to his bigfoil.com website. I thought it useful. I especially like the Bezier curve fitting of the airfoils which could also be super useful.

 

[WARPilot]

The simplest way to accommodate a pilot emergency parachute is to delete the seat back. Install the seat bottom as per the plans, but extend it all the way back to the cockpit's rear bulkhead. This will leave a large, wedge-shaped space to install a PEP. A side benefit is increased leg room. All the major manufacturers (Butler, Para-Phernalia, Strong, etc.) make wedge versions of their PEPs. When not wearing your PEP, just Velcro in a wedge-shaped cushion.

The ballistic chute adds costs and weight, 15#, aft which is not good. You are correct about the ease of adding a wedge to accommodate the PEP. The PEP weighs about 15# also.

 

[GeorgeG]

Check out airfoiltools.com.

FWIW -- I used airfoiltools to print my USA-35b airfoil. I had to set my printer at 112% to get the actual printed on paper airfoil dimensions to be correct, even though my chord was entered correctly in the plotter.
I s'pose I could have altered the chord dimension in the plotter, it just seemed easier at the time to adjust the print scale.

 

[WARPilot]

I would suggest you'd need more wing area and Span and a lot of Flap area to get those performance numbers. The Actual shape of the Aircraft doesn't inspire low drag and maybe good for landing speed but not good for high speed which would require a Laminar Airfoil, I would accept Billski's suggestion of a Riblett Airfoil which are very similar to the NASA 6 series Airfoils and look to reducing Drag wherever you can.
For low weight I would consider using Carbon composite.
George

It would be a carbon fiber build from a mold. Probably a 2 core 2 with four or five bulkheads, the seat being one of them. Carbon fiber spar, 9G ult. We think the weight will be less than 350# with the gear retract system. FWF will weigh approx 200#.

 

[rv7charlie]

Keeping fuselage walls parallel - to the trailing edge - will also improve shoulder room in the cockpit.

It'll reduce drag, too.

 

[rv7charlie]

FWF will weigh approx 200#

Seems unrealistically optimistic. According to Verner, the bare engine weighs ~183 lbs. It will need a *lot* of elaborate baffling help to keep cooling drag low enough to go fast. And an exhaust system. And a low drag induction system. And I'm guessing, and oil cooler, with plumbing. Fitting all that in a 17 pound box will be really impressive.

Or are you talking about a different engine?

 

[WARPilot]

True, It would be a kit. The mold is the hard part but my friend does it all the time. He also analyzes the stresses and builds the laminate schedule. We would use carbon fiber, he is a dealer of this material, engines I’m considering are Rotax, Verner, D-Motor. All these are under 180# less prop. There is also a Higgs engine that may work. Probably just design for a MGL or GRT all in one flight instruments for simplicity and light weight.

There are several engine choices that are in the 165-180# category. Verner 7s is 183#,

Seems unrealistically optimistic. According to Verner, the bare engine weighs ~183 lbs. It will need a *lot* of elaborate baffling help to keep cooling drag low enough to go fast. And an exhaust system. And a low drag induction system. And I'm guessing, and oil cooler, with plumbing. Fitting all that in a 17 pound box will be really impressive.

Or are you talking about a different engine?

Seems unrealistically optimistic. According to Verner, the bare engine weighs ~183 lbs. It will need a *lot* of elaborate baffling help to keep cooling drag low enough to go fast. And an exhaust system. And a low drag induction system. And I'm guessing, and oil cooler, with plumbing. Fitting all that in a 17 pound box will be really impressive.

Or are you talking about a different engine?

Seems unrealistically optimistic. According to Verner, the bare engine weighs ~183 lbs. It will need a *lot* of elaborate baffling help to keep cooling drag low enough to go fast. And an exhaust system. And a low drag induction system. And I'm guessing, and oil cooler, with plumbing. Fitting all that in a 17 pound box will be really impressive.

Or are you talking about a different engine?

I was on the phone with Brett Hahn, Verner Dealer in Las Cruces , NM today regarding the engine. His numbers indicated we would be in that ballpark. Obviously the goal is to stay as light as possible. While a radial would be nice it does add problems due to requirement to enlarge the cowl by 1.5".

 

[rv7charlie]

For an objective opinion, I'd start with (not)a dealer, or better yet, a calibrated scale.
;-)
For perspective, a bare 4 cyl Lyc gains from 30 to 50 lbs to make it usable for powering an airplane.

 

[BJC]

It would be a carbon fiber build from a mold.

That means that it would be an all new design.

While a radial would be nice it does add problems due to requirement to enlarge the cowl by 1.5".

Since it will be an all new design, why not scale it to the chosen engine?


BJC

 

[Marc W]

Since it will be an all new design, why not scale it to the chosen engine?

Yes, the airplane really needs to be bigger to meet your goals and to have any appeal to today's larger pilots. Your stall speed will be closer to 70 mph than it will be to 50 mph. With your small wing and the resulting low Reynolds number, there isn't enough flap in the world to stall at 50 mph.

 

[Map]

WARpilot, have you seen my airplane design videos? This one is on airfoil selection:

and I recently added two on drag reduction:

(first one)

 

[Vigilant1]

Yes, the airplane really needs to be bigger to meet your goals and to have any appeal to today's larger pilots. Your stall speed will be closer to 70 mph than it will be to 50 mph. With your small wing and the resulting low Reynolds number, there isn't enough flap in the world to stall at 50 mph.

Given the info in the OP (900 lbs, 77 sq ft wing), it requires a total wing CL of about 1.8 to achieve a stall speed of about 50 mph. That doesn't sound outlandish, though it may be a tad "optimistic." Achieving the 900 lb goal will take some doing.

 

[Pops]

Not an easy choice. I was 2 years trying to decide on what airfoil to use on the JMR. Finally went with the 2414 but Bob Barrows kept trying to talk me into using the Riblett . Everything is a trade off.

 

[WARPilot]

The videos are excellent

 

[Marc W]

Given the info in the OP (900 lbs, 77 sq ft wing), it requires a total wing CL of about 1.8 to achieve a stall speed of about 50 mph. That doesn't sound outlandish, though it may be a tad "optimistic." Achieving the 900 lb goal will take some doing.

"a tad" is understating the case. I think a real world wing lift coefficient for an unflapped wing in the size he is using is somewhere around 1.1 to 1.2 at the Reynolds numbers he will see at stall. It's a long way to 1.8 with any kind of simple flapped wing.

But, if he builds it, he will find out.

 

[WARPilot]

"a tad" is understating the case. I think a real world wing lift coefficient for an unflapped wing in the size he is using is somewhere around 1.1 to 1.2 at the Reynolds numbers he will see at stall. It's a long way to 1.8 with any kind of simple flapped wing.

But, if he builds it, he will find out.

Currently, the WAR FW weighs approx 1050# for Take Off. Stall occurs at 65-66mph. Current top speed is 165mph.

 

[TFF]

I think 1200 is where they usually end up. Lots end up going overboard with finishing and glassing.

 

[Marc W]

Stall occurs at 65-66mph

Just curious. Is that indicated or calibrated airspeed?

 

[WARPilot]

Just curious. Is that indicated or calibrated airspeed?

Indicated