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  #46  
Old 09-14-2016, 11:23 AM
Skyak Skyak is offline
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Originally Posted by Doug Halsey View Post
I'm also skeptical because it's another example of an overly-broad statement. You can't just say that one foil has more drag than another; you have to specify the conditions.

A foil with a flap may have higher drag than one without in low-lift conditions, but lower drag in high-lift situations.

Here's an example to illustrate that point, from a Moth foil-design study that I worked on earlier this year.
You are absolutely right. Please understand that sometimes the overly broad statement I make is not my own, and sometimes I do it just to get educated and respected sources to step in and correct me -often bringing terrific supporting information. It's a "shaker" tactic from "movers and shakers". On the aero/hydro forum about everything I post that isn't a question fits the categories above. I am proposing measuring boundary layer thickness and sail shape for closed loop analysis. Miko called me out on it and Mark D. filled in some blanks. I'm not here for ego, I am here to learn.

If you are afraid that someone will take one of my overly broad statements and run with it as gospel, well there is absolutely no evidence of that.

Thanks for the study.
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  #47  
Old 09-14-2016, 02:57 PM
waynemarlow waynemarlow is offline
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Doug no chance of an apology as you are very much a theoretical man, but I still admire you in some ways for your tenacity despite the Internet kickings you take at times. Just if only you would take those ideas beyond theory and put them to the real test, getting them into full size boats on the water, just simply stop moving onto the next idea that catches your interest and build a full size boat for a change.

Skyak, you definitely do come across as a student in the process of learning and good for you, but you really must get your head out of the classroom and onto a boat or two, spend time in a sailing club really understanding what makes things tick, you will be unpleasantly surprised that real life situations often don't conform to theory and statistics. Certainly when I was doing my time at Uni studying electronics it was very clear to me as the oldest student in class, just how far out of touch the tutors and most students were in how one must grind out an income to support ones way of life.

Getting back to foils, certainly on the time I spent on the S9 foiler, it was pretty apparent that one could use ones body weight to really dictate the AOA of the foil, such that if I had more time to play with the boat, the first thing I would do is actually lock the elevator off at a set position and just see if all that elevator control gear was actually worth the weight and the foil losses from the hinge line that a split foil created, I suspect on the short length boats such as the S9 and UFO a pure slightly larger more wide speed foil may well achieve the early lift off with the loss of just a few knots of speed top end.

One thing to throw into the discussion, both the A and S9 are operated from the trapeze wire where you can move easily back and forward, the sitters such as the UFO and Moth, the skipper is pretty much sitting statically, locked on ones bottom or legs fixed under straps, certainly ones movements are going to be far far more slowly than if you can walk back and forward, I wonder how much effect this is having on the end design ?
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  #48  
Old 09-14-2016, 03:34 PM
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Doug Lord Doug Lord is offline
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Originally Posted by waynemarlow View Post
Doug no chance of an apology as you are very much a theoretical man,
==========
You know, wayne, you really don't know what you're talking about.
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  #49  
Old 09-14-2016, 05:20 PM
CT249 CT249 is offline
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Originally Posted by waynemarlow View Post
One thing to throw into the discussion, both the A and S9 are operated from the trapeze wire where you can move easily back and forward, the sitters such as the UFO and Moth, the skipper is pretty much sitting statically, locked on ones bottom or legs fixed under straps, certainly ones movements are going to be far far more slowly than if you can walk back and forward, I wonder how much effect this is having on the end design ?
From the very short runs I've had on sit-down foilers, it has a minor impact on the Moth (which is very, very short and very, very light) and a major impact on a longer and heavier boat.
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  #50  
Old 09-15-2016, 02:31 AM
waynemarlow waynemarlow is offline
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Originally Posted by Doug Lord View Post
==========
You know, wayne, you really don't know what you're talking about.
You wouldn't be the first to say that but I tend to get things right more often than not.
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  #51  
Old 09-15-2016, 09:08 AM
Skyak Skyak is offline
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Originally Posted by waynemarlow View Post
Doug no chance of an apology as you are very much a theoretical man, but I still admire you in some ways for your tenacity despite the Internet kickings you take at times. Just if only you would take those ideas beyond theory and put them to the real test, getting them into full size boats on the water, just simply stop moving onto the next idea that catches your interest and build a full size boat for a change.

Skyak, you definitely do come across as a student in the process of learning and good for you, but you really must get your head out of the classroom and onto a boat or two, spend time in a sailing club really understanding what makes things tick, you will be unpleasantly surprised that real life situations often don't conform to theory and statistics. Certainly when I was doing my time at Uni studying electronics it was very clear to me as the oldest student in class, just how far out of touch the tutors and most students were in how one must grind out an income to support ones way of life.

Getting back to foils, certainly on the time I spent on the S9 foiler, it was pretty apparent that one could use ones body weight to really dictate the AOA of the foil, such that if I had more time to play with the boat, the first thing I would do is actually lock the elevator off at a set position and just see if all that elevator control gear was actually worth the weight and the foil losses from the hinge line that a split foil created, I suspect on the short length boats such as the S9 and UFO a pure slightly larger more wide speed foil may well achieve the early lift off with the loss of just a few knots of speed top end.

One thing to throw into the discussion, both the A and S9 are operated from the trapeze wire where you can move easily back and forward, the sitters such as the UFO and Moth, the skipper is pretty much sitting statically, locked on ones bottom or legs fixed under straps, certainly ones movements are going to be far far more slowly than if you can walk back and forward, I wonder how much effect this is having on the end design ?
Those that say it can't be done should not delay those that say they will try.

On traps you will have very good control of your body weight in two degrees of freedom. Rudder is a sloppy control of the same axis. I still say you at least need another degree of freedom in sail control.

On the plus side, locking out the wand will certainly give you incite on how you should be moving to minimized flap drag.
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  #52  
Old 09-15-2016, 09:30 AM
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Originally Posted by waynemarlow View Post
You wouldn't be the first to say that but I tend to get things right more often than not.
===============
Not about me or my boats you don't! And not about foiling technology........
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  #53  
Old 09-15-2016, 09:40 AM
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Ufo

Pictures from Fulcrum Speedworks: https://www.facebook.com/fulcrumspee...47674918814884

UFO and some veal heel:



UFO-getting started:

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  #54  
Old 09-15-2016, 10:19 AM
Skyak Skyak is offline
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Originally Posted by Doug Halsey View Post
I'm also skeptical because it's another example of an overly-broad statement. You can't just say that one foil has more drag than another; you have to specify the conditions.

A foil with a flap may have higher drag than one without in low-lift conditions, but lower drag in high-lift situations.

Here's an example to illustrate that point, from a Moth foil-design study that I worked on earlier this year.
Doug,
thanks again. I see what you mean. Looking at that graph I see that the flap can provide low drag control over a range of lift, but I also see it can be screwed up. It looks sensitive to settings and loads. The UFO and Waszp are eliminating adjustment of wand/flap...

Of course it is more complicated than just a 2D profile. Have you ever pieced together multiple spanwise profiles and tried to estimate the full 3D lift and drag?
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  #55  
Old 09-15-2016, 10:22 AM
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UFO /Waszp

Skyak, just curious: what do you mean by "the UFO and Waszp are eliminating controls..."?
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  #56  
Old 09-15-2016, 10:40 AM
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Tom.151 Tom.151 is offline
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Originally Posted by waynemarlow View Post
You wouldn't be the first to say that but I tend to get things right more often than not.
That's a poor track record for most things technical Just saying.
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  #57  
Old 09-15-2016, 12:03 PM
Doug Halsey Doug Halsey is offline
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Originally Posted by Skyak View Post
Doug,
thanks again. I see what you mean. Looking at that graph I see that the flap can provide low drag control over a range of lift, but I also see it can be screwed up. It looks sensitive to settings and loads. The UFO and Waszp are eliminating controls...
That's right. The low-drag region gets progressively smaller as the flap deflection is increased, making it much more difficult to obtain the optimum flap settings at the higher CL's. However, such high values are only needed for a brief period during takeoff, so I don't think this is a critical problem (especially for the Waszp or UFO).

Quote:
Originally Posted by Skyak View Post
Of course it is more complicated than just a 2D profile. Have you ever pieced together multiple spanwise profiles and tried to estimate the full 3D lift and drag?
Yes, I have a code for estimating drag-versus-speed curves for 3-D foils, accounting for the variation in local lift coefficient & Reynolds number across the span (in a 2-D strip-theory manner) and for the CL required at each particular speed. I can't say much more about it at this point though. Also, that would be serious thread drift.
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  #58  
Old 09-15-2016, 12:05 PM
waynemarlow waynemarlow is offline
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"That's a poor track record for most things technical Just saying."

Yes agree that statement but if any one tells you that they get things right 100% of the time then they probably have spent a lifetime on one successful project or they are being slightly economical with the truth and you need to walk away
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  #59  
Old 09-15-2016, 12:28 PM
Skyak Skyak is offline
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Skyak, just curious: what do you mean by "the UFO and Waszp are eliminating controls..."?
They are removing the adjustment of the wand/flap based on what I have read. I will go back and replace "controls" with "adjustment of wand/flap".
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  #60  
Old 09-15-2016, 12:37 PM
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I'm not positive but I think both have the facility to adjust altitude by adjusting wand length. But I don't think gearing is adjustable.
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