# WantedJC Propeller Design Software

### Help Support HomeBuiltAirplanes.com:

#### alfredo montalvo

##### New Member
I am interested in Jan Carlsson's JC Propeller Design software too.

Regards

#### davidjgall

##### Well-Known Member
I am interested in Jan Carlsson's JC Propeller Design software too.
I’m working on a functional replacement

#### Lendo

##### Well-Known Member
Well this is timely, I just finished reverse engineering Jan Carlsson's Program, but it may not be exactly as his program processes it. I have the answers, but they can be found in a number of ways and I'm unsure which is the most logical steps. I thought it should be as straight forward as the 75% Pitch (being Aircraft speed divided by the RPM), however values are interwoven in so may ways, it must have been a 'Maths Master' to sort through it all. My way required a Look- up set of simple tables. Believe me when I say I say I look at every conceivable way of using the basic numbers to get the answers in a step by step process, but a smarter person may see a more direct process. I'm hoping there's someone here that can do this.
If you want me to kick-off the process, let me know and I will start with how I did it.
George

#### TFF

##### Well-Known Member
How does the program handle different airfoils and blade tapers.

#### Lendo

##### Well-Known Member
TFF, Good question, I have gotten to the Chord lengths yet it was hard enough to get the Basics of Pitch and Angle (B) at every 15% station.
Remember this is just his basic program, I was going to apply Paul Lipps approach of Elliptical Lift distribution for the Chord Lengths and also look to Jack Norris's approach to compare - but all that is a long slow process. It took me a week of spare time to get this far - like others I had been putting this research off for some considerable time. I had two copies on different computers and when one was corrupted I figured it was about time to understand the basic processes.
JC doesn't use modern airfoils, he used a combination of Clark Y and RAF 4, he did offer up that information. From research, others consider that using Laminar Flow Airfoils to be a waste of time, probably considering bugs and damage to the leading edge.

It is a very interesting exercise and an education in itself for those interested in the how and why. My experience is that most people just want something off the shelf, or professionally made. The local Prop maker (now retired), made a beautiful wooden prop, with an indestructible leading edge and brilliantly copied proven propeller designs, but had absolutely no idea of how to calculate and design one.

Personally I think everyone should know the basics, so I will offer up as much as I lean, when it's available - to those who are interested.
George.

#### TFF

##### Well-Known Member
I believe Hercules props used his program.

#### Lendo

##### Well-Known Member
TFF, if you mean Jan Carlsson, I believe he had a dedicated maker, but would provide the necessary data for a consultancy fee and that for the new program. I believe it was about \$100 US, not all that much considering what's involved. Me I just love the process, it's a bit of a struggle, but I'm determined to get there.
George

#### TFF

##### Well-Known Member
He had two programs, the newer one was consulting only. The other was for sale and I’m pretty sure Hercules was one of the purchasers. I think both talked about it on HBA. He use to post some screen shots sometimes.

#### davidjgall

##### Well-Known Member
He had two programs, the newer one was consulting only. The other was for sale and I’m pretty sure Hercules was one of the purchasers. I think both talked about it on HBA. He use to post some screen shots sometimes.
That is correct. I spoke with Rupert Wasey of Hercules Propellers some years ago and can confirm.

#### davidjgall

##### Well-Known Member
TFF, Good question, I have gotten to the Chord lengths yet it was hard enough to get the Basics of Pitch and Angle (B) at every 15% station.
Remember this is just his basic program, I was going to apply Paul Lipps approach of Elliptical Lift distribution for the Chord Lengths and also look to Jack Norris's approach to compare - but all that is a long slow process. It took me a week of spare time to get this far - like others I had been putting this research off for some considerable time. I had two copies on different computers and when one was corrupted I figured it was about time to understand the basic processes.
JC doesn't use modern airfoils, he used a combination of Clark Y and RAF 4, he did offer up that information. From research, others consider that using Laminar Flow Airfoils to be a waste of time, probably considering bugs and damage to the leading edge.

It is a very interesting exercise and an education in itself for those interested in the how and why. My experience is that most people just want something off the shelf, or professionally made. The local Prop maker (now retired), made a beautiful wooden prop, with an indestructible leading edge and brilliantly copied proven propeller designs, but had absolutely no idea of how to calculate and design one.

Personally I think everyone should know the basics, so I will offer up as much as I lean, when it's available - to those who are interested.
George.
There's no magic in Carlson's program; he just never told us what book he used to derive his method, but he did not hide the fact that it was a method he found in a book. So a survey of the literature might help instead of trying to reverse engineer it. (P.S. It's RAF-6, not RAF-4.)

Let me save you much effort and time:

Instead of trying to reinvent Lipps' work or wade through Norris' swamp of language, just read the papers written by Adkins & Liebeck and by Larrabee, posted as references 10 and 11 on Martin Hepperle's JavaProp bibliography page (Bibliography) and start coding (or just use JavaProp, but you'll have to fudge the transition to the hub, an important detail that JavaProp inconveniently ignores). If you write your own code using this method you will obtain a skeleton into which you can plug Lipps' elliptical load distribution (if you must ) or onto which you can impose Norris' canoe-waterline blade planform ( ) but in any case you'll be well on your way to duplicating the most successful propeller design computer algorithm of the 20th century.

Otherwise, get Fred Weick's 1960(?) Sport Aviation article in which he expands on his N.A.C.A. Technical Note 212 from 1925. It's as good as any thing else, especially when you consider the state of the art as exemplified by your "local prop maker." You can get the important design information for a good prop in about 20 minutes this way.

If you have the stomach for Theodorsen's method, find the 2004 paper by Quentin Wald and the four NACA reports (924 et. seq.?) that tell how to do it (as opposed to Theodorsen's book that's mostly just a big nose-thumbing in the direction of those "lesser folk" who aren't actually Theodorsen). You can exercise your skills at curve fitting and code those polynomials....

Another reference, ANC-9, has a different design approach and also contains lots of good info, but you also must absolutely have the huge errata supplement before trying to use it to design a propeller.

Finally, Henry Borst and Associates did a series of NACA reports (10 parts) in the 1960s(?) that are available from NASA's technical report server and will help you design everything right up to and including your own personal homebuilt V-22 Osprey if you have a spare weekend or two, but it might be overkill.

For ordinary airplanes on ordinary days, Weick's method will get you to a serviceable product faster than anything else. Unless you already have a computer program....

For those awaiting my "functional replacement" of Carlson's JCPropellerDesignX please standby and continue sending me copious amounts of money and caffeine. Thank you.

#### rivilee

##### Well-Known Member
HBA Supporter
your own personal homebuilt V-22 Osprey
Sorry, no money but I've got popcorn at the ready!

#### Lendo

##### Well-Known Member
Referebce : davidJgall, now that's a man who has done his research, I take my hat off to you. Having said that, I'm now done this path, and I need to finish - if I can.
George

#### Lendo

##### Well-Known Member
davidgall, I spoke to Paul Lipps by e-mail, pity he's no longer with us. I agree about Jack Norris's book, it's a hard read. I actually developed my own method of elliptical Lift approach, to apply to Wing Loading, it's not so difficult when you know how. Everyone's approach is basically pulling back the load from the Tip, where lift goes to nothing anyway. I notice when I do the Maths Jan Carlsson modifies the Twist angles on the blade and I don't as yet know why. It could be that he uses two different Airfoils. I think one is thicker than the other and makes for a stronger tip, (from discussions with him) that could be due to difference in lift between the two profiles, yet to be confirmed. The difference goes from almost nothing to over a degree at the tip the numbers seem to signify a linear variation along the blade, still working on that.
I'm sure I did a spread sheet on Welch, but can't now find that book, it was fairly involved and in the end I wasn't quite sure of what I had. The beauty of Carlson's program it confirms the figures of my own work- apart from the slight difference in angles. However when I reversed the maths for my angles, the Pitch was accurate, and I used all 9 decimal places to assure accuracy. That's why I know he did some modification on the angles.
George

#### blane.c

##### Well-Known Member
HBA Supporter
Might some of Carlsons be from empirecal?

#### Lendo

##### Well-Known Member
blanecc, could be who knows, but all his maths is based on basic parameters right up until the angles, so it seems deliberate for some reason. I guess I will have to nut it out, but that all takes time. From the 15% of blade, the numbers are so close as seen to be rounded-up. however as one gets to 60% and 75% it becomes obvious, there is a variation factor involved. Knowing he combines the Clark Y and the RAF 4, seems to me to indicate some difference between the two. Certainly that would/ could be because of Tip thickness needed or preferred in a timber Prop. Had I worked on this sooner I might has answers to some of these questions.
George

#### Lendo

##### Well-Known Member
As I put this up in the wrong discussion, I thought I'd repeat it here for those interested.
JC's calculations the Angle (B) at 15% is 48.42 - My answer was 48.41832095, one would initially think a simple rounding-up of the number. I did.
However at 100%, my angle (B) is 25.01533069 where JC's is 23.83 - more than 1° difference, down.
George

#### davidjgall

##### Well-Known Member
JC's calculations the Angle (B) at 15% is 48.42 - My answer was 48.41832095, one would initially think a simple rounding-up of the number. I did.
However at 100%, my angle (B) is 25.01533069 where JC's is 23.83 - more than 1° difference, down.
George
George, are you working from the same reference sources as he was? Can you be more specific about where this discrepancy is showing up?