Wing Data

[Robert Lees]

I should be able to dig this info out from somewhere, but I'm struggling to find it; can anyone help?

Wing chord
CL max for the 23012 airfoil

Thanks

[Mark Julicher]

Re: Wing Data

Rob,

Three dimensional airfoil data shows a coefficient of 1.5 @ 16 degrees AOA, with incipient stall occurring and this is with a clean airfoil.
Real world is more like a Cl of 1.35 to 1.4 at 15 degrees AOA and standard roughness on the wing.

Another text indicates that a 2D 23012 airfoil yields Cl of 1.32 at 10 degrees AOA and airfoil is not stalled.

These should be good numbers for a back of envelope calculation or to settle a bar bet.

[VictorBravo]

Re: Wing Data

I should be able to dig this info out from somewhere, but I'm struggling to find it; can anyone help?

Wing chord
CL max for the 23012 airfoil

Thanks

63 inches wing chord if I recall correctly.

[Robert Lees]

Re: Wing Data

Thanks, both...

Can I assume, Mark, that the CL Max (meaning the maximum) is therefore 1.5 ?
Surely the "maximum CL" is just that...or am I just being un-edumicated?

[Mark Julicher]

Re: Wing Data

You have it correct Rob. Cl Max about 1.5 or how about calculating it for the whole airplane?

L = CL * .5 * (.00237) * (velocity squared) * wing area

For CL max assume max weight and minimum speed or 1200 lbs weight and a stall speed or 60 feet per second which is about 40 mph.

1200 = CLmax * .5 (.00237) * 60 * 60 * 180

1.56 = CL

Discrepancy from wind tunnel data can be attributed to the lift contribution of the fuselage, additional down force from the horizontal stabilizer, and up force from the thrust vector.

[Robert Lees]

Re: Wing Data

Thanks for your help Mark...some of the information I am trying to work with assumes a known CL Max. The attached spreadsheet shows a calculation for loads, where the yellow boxes are for the input data, one of which is the CL max. You can play with the input data.

I am trying to go for an increased gross of 1280 (along similar lines to the Harer STC) but with an O-200 instead. (try putting in 1200lb gross...it results in a stall speed of 39.18mph, which sounds about right for a 122lb BC12D).

Reference to BCAR is the British Civil Aircraft Rules, but they do not differ significantly from the pertinent American CAR's & FAR's.

Any input you are willing to offer would be very much appreciated.

Regards,
Rob

http://www.taylorcraft.org.uk/G-BREY_FTILMANE.XLS (22kB)

[VictorBravo]

Re: Wing Data

Rob, you can also simply document the various years and models of T-craft, a long with their weights, horsepower, and stall speeds. Then you can point to what you want to do on that graph and say "There! That's what I want to do, come in just between the BC-12D-85 and the Sportsman 100" or something like that. Showing that there are certified aircraft on both sides of your proposed configuration means you are "interpolating, not experimenting".

It's fairly well known (and discussed here recently) that the C-90 will perform better than the O-200 in many cases, particularly with a Taylorcraft propeller and at Taylorcraft speeds. So you could make it sound like only a small horsepower upgrade of 5 HP, and have the CAA buy off on it more easily, but you can fail to mention to them that the C-90 gives you more oomph where you need it than the O-200.

My good friend 'L-2 Gary' once told me that there is one combination of (85, 90, and O-200) certified crankshaft, camshaft and pistons that yields a 94 horsepower output and higher torque at lower RPM that makes a Taylorcraft into a rocket. You get almost all the HP, but more torque and at lower RPM, and significantly less fuel consumption. Might be worth lookng into if you are going through the approvalp rocess anyway. The parts all look identical to the average government inspector

[Mark Julicher]

Re: Wing Data

Rob,
I had fun doing what-ifs on your spreadsheet.

So if I understand all this, you need to show by analysis or demonstration that your 1280 lb Taylorcraft can withstand the manoeuvring, cruise, and dive speeds in the desired category. I like Bill's interpolation approach - it should keep any bureaucrat within their comfort zone.

I can't recall ever seeing in writing a manoeuvring speed for the T-craft, but obviously the CAA spells out the regulatory minimum.... hmmm I guess I have never had the 'nads to try full control deflections up around 79mph.

Fun thread.

[Robert Lees]

Re: Wing Data

Bill:

The UK authorities here are proving a little difficult in accepting what you suggest, without further structural data on the fuselage, etc. They have "almost" accepted that a redesigned mount will prove satisfactory, and I won't mention the fuselage structure if you won't! Of course, we cannot prove (without drawings) that the "approved data" of any design interpolation over the years is the same design of my 1946 model. My mount is going to be slightly shorter anyway, to squeeze the O-200 into the short cowl.

I know where you are coming from on the C-85 / C90 / O-200 side of things...I'm pretty much stuck with an O-200 now, because I bought a brand new O-200 very cheaply!

Mark:

That is what I am ultimately going to have to do. I have already incorporated several fairly major structural changes to the machine, and I need to demonstrate that the new mount will absorb the additional horsepower / thrust / torque & vibration.

I have a lot of very valuable but subjective information on the design changes between the B and the F models (after all, I am fundamentally going to end up with a hybrid between a BC12D, the Model 19 and an F19...or to put it another way, a short mount, non-electric F19), but this information is not adequate in terms of "approved data" to satisfy our ever-increasingly-burdensome authorities over here.

Lastly, I always did think the manoeuvering speed was about 80 mph, but like you I can't recall where I first came across this.

Thanks for everyones' help...I'll keep you posted.

Rob

[VictorBravo]

Re: Wing Data

My mount is going to be slightly shorter anyway, to squeeze the O-200 into the short cowl.

Godspeed to you on that. I'm having enough trouble getting the cowl mounted over the same A-65 with the "new and improved" cooling baffles I built recently.

I strongly suspect that a "repaired" nosebowl is worth looking into. By repaired I mean that the nose bowl has an intense love affair with a mallet and shotbag or an "English wheel", so that the Dzus fasteners still attach to the lower cowl in the same place but the triangular air inlets are further forward.

Another three or four inches of depth (or draw or relief or whatever it's called by the tin bashers) would be a big improvement. A short certified prop extension is a known quantity on more than one certified aircraft so you should be able to get that through... or better yet just don't mention it.

Not only would this allow you to have a mount that fits easily, able to remove the mags, etc. but there are probably aerodynamic benefits as a bonus. It will certainly be easier to make a cooling system that ducts the air downward through the #4 cylinder fins properly.

Seriously, consider this if you would. Have a tin basher anneal the nose bowl and then stretch it a few more inches forward in the corners. Those big triangular openings are way too big anyway (it's the outlet on the bottom that chokes the T-craft cooling) so if they get shrunk a little in the process it's no problem. You'll need to add a flare or a lip on the bottom cowl anyway to pull some more air out.

Get a receipt from the tin basher that says "repaired and reworked original nose cowl". If the CAA even spots the 3" prop extension, you can say "Well, the repairs on the nose bowl stretched it a bit, so I had to add a spacer to prevent the propeller from rubbing... I used a spacer very similar to Cessna part number XYZ and Piper part number ABC"

[Robert Lees]

Re: Wing Data

My nosebowl is also "repaired". I found a drawing showing an extra 1/4" in the front and at the sides...and my chin cowl & my new top cowls were made to fit. And they are all made of a slightly thicker gauge aluminium.

Did I mention that my Grandmother dressed as a wolf, and I'm really Little Red Riding Hood?

The whole lot can be proven to fit the Univair intake grilles, and I have a Certificate of Airworthiness now, so it must all be legal, right?

[Acroeric]

Re: Wing Data

Rob- I have some data that indicates the stock engine mount will hold an O-200 in place during multiple snap rolls entered at 90 mph ;-)

They sure seem to be more stringent than the USA with regard to older aircraft and equivilancy.

[Robert Lees]

Re: Wing Data

That would be very nice to have, Eric, thanks. Do you need my mailing address, or is it email-able?

I don't think they're more stringent; they are perhaps being cautious in that no approvals have been requested here for these things.
American 337's, STC's and US "Approved Data" , and even "anecdotal information" are all very much appreciated here as a justification for approving design changes here.

What did the tail look like afterwards...or was that modified?