I didn’t attempt to produce a specific aerofoil for my current wing (so I’d suggest it may not be the best one to follow), but I am looking into this more carefully for the next one. The following page suggests a number of aerofoils for Land Yachts:
Another piece of advice I came across on a Boat Design.net - Doug Lord thread, apparently from Steve Clark:
http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/understanding-wing-technology-34697.html: “I’m going to say some stuff that is going to shock some people.I think it is easy to overthink some of this stuff, The small detail of section shaping and selection probably maters less than getting the weight down and making the controls simple and reliable. I mean you are never going to be able to tell the difference between a Eppler or a NACA section if the flap sags and the wing is inside out half way up it’s span. As a result, I encourage you to make nice conservative choices for your sections and then spend most of your effort on the structural and mechanical engineering side of the problem.”
I’m planning to keep working with the foam method, but try to modify it somewhat to: get more control over the aerosol shape; improve the shape of the leading edge; cover it with a film of some sort (there seem to be lots of options developed for model planes). I will also simplify the design to a single large flap, more like the wings sails you see on a Moth.
Hi Jim,
my understanding is that the front profile and the flap should act as a unique profile. Some one was telling 'think one" also for soft sails.
To achieve that condition, the flap pivot is sitting inside the front profile. Mechanical devices should then be developed to allow this condition.
The other point very important is the width of the gap. Probably testing on various distance adjustments should establish the best condition.
This sketch to explain my thinking :
…
My competence in this respect is equal to zero, therefore better to avoid adding anything else.
Hi Marc,
I’m told that the profiles should be symmetric and not as you draw !
The asymmetry is created as I drawn in previous post by using two symmetric profiles !
Cheers
Claudio
yes Know, it should be symmetrical. I don’t have the nice drawing program at work. I did a cut/copy paste from another website…just to show the “nested” flap
With the “nested” flap, the full profile is “cornered” and probably producing earlier flux detachment and the rotation angle is very limited. It may be god on airplane wing where the flaps are turning only in one direction !
I’m basing my “experience” on"what I see, and the wing building from my glider days…
I thought the gap would also result in less than ideal air flow… gives the air potentially different options to travel… too wide of a gap and you have two foils the idea is to trick the air into think you have one big foil and not “separate”
which makes me wonder if the mixed breed of a soft aft section migh be a better option… of course the key is to have a material that is strong enough to not “crease” at the interface between solid/soft, but still be soft enough to “flop over” on the change in tack in lighter air…
Marc,
the important thing is to avoid turbulent flux.
It may be possible that the two parts are producing separate lift and the gap is there to accelerate the flux on the second profile to delay the turbulent flux on this second profile.
In other words, as I understand, the first profile flux is getting already turbulent just before the second profile begin.
In this case the overall lift is reduced.
With the gap instead the flux is accelerated again for the benefit of the second profile.
Cheers
ClaudioD
Interesting discussion. I take your point regarding the hinge point Claudio. It should be possible to achieve with the foam approach that I am using.
I have a question regarding experimenting with the gap. I’m wondering how to set up a test system, what I should be measuring, and what I should try to optimise? Also, given that I only have a simple household fan, will the experimental error be larger than the effects that I am trying to measure?
As noted by Claudio - the gap between flap and leading edge acts to increase flow and attachment to the flap. If nested and an extreme angle to flap, wind on leeward side would easily become detached and there would be a stall along most of the trailing flap.
On the info I posted, note that the lower example allows the leading edge of the front of the sail to flop from side to side which helps with angle of attack and also the camber moving to leeward side of the sail. You can use a soft (relatively) sail with only the leading edge needing to be firm.
Great K.I.S.S project … looking at basic wing profiles maybe you can use little inspiration from AC 72’s, this sketch clearly shows the difference in wing profiles of ETNZ and Artemis … I know which one I would use
my plan is to print out my sail full size on my plotter and then add in the naca profile to the proper size. and then start building.
I figure if I go withthe current size main as long as I can keep the weight down, its a start. I do need to modify the boat so the mast is free standing… if I can get the shrouds out of the mix will make life a bit easier…
my flap is going to be simple.
my hobby shop sells premade balsa ailerons similar to what is pictured on the right…
looks like the flap is about 50% of the sail… should I start there, or shoot for like 25% of total area…
the foot of my main is 21cm, and the premade balsa ailerons are 4cm… so by the time it gets to the top of the sail the flap is the same width as the sail…
using the premade ailerons would cut down on the build time. Ie not having to build 2 wings…
of course if I choose wrong. I still end up having to build 2 wings…
Marc - as many as I could find quickly. Didn’t access my 2 TB hard drive yet - but that is more for backup - so probably contains similar or duplicates. Some are big boats, some are r/c boats - you should be able to identify.
Dick
PS - can’t remember all of them - but perhaps others will chime in. Photos include the 18 Sq. Meter Class, “C” Class (Little America’s Cup), and some r/c stuff. The one photo of a wing build framework was provided by Magnus Clark who was the wing babysitter on the first Oracle wing boat.
I saw many of those when I was googling…some half, som eless than half, some none… so all over the place…
did some cutting and taping…have not printed out the naca profiles yet.
so even though the mast is taped on the leading edge of the wing. I’m not sure of what I’m gonig to do yet…
a keel stepped stay less rig will be nice, but then no real option for a jib. and the need for some sort of ball raced pivot. since the wing will be heavy on the aft side… I doubt it would swing very easily…plus th eneed to drill out the deck and fit some sort of tube for the mast…
if I go with a deck step, then I need ot make sure the wing and can pivot through about 160* which means slots cut in to allow for shrouds to exit… and channels cut for rotation… of the wing, but it will allow for a jib…
