Mast Aft Wing Sails???

[Skyak]

To get the 3D effects, you need to analyze the planform with at least a vortex lattice code, as lifting line theory doesn't handle sweep. Sweep will load the downstream end compared to the upstream end, because the downstream end experiences an increased angle of attack due to the trailing wake.

Vortex lattice theory looks complicated enough that I could not trust my results and simple enough that it might not be valid for the cases I am interested in (angle of attack and angle of side slip must be small for it to be valid). It looks like a good theory for understanding plan form but I better start with prototypes. Is there anything simple I can do to estimate or bound the induced drag? Am I ok assuming symmetry at the water plane if air is not free to leak under?

Sweep loading the downstream end, increased angle of attack -now that's gold! Can you direct me to literature that would help me understand and quantify this effect? This sounds like what I experienced and am looking to understand/exploit.

You can do vector addition to resolve the apparent wind into the wing coordinate system and then calculate the effective angle of attack and sweep. Canting forward and sweeping aft can be the same as having an unswept rig. It is basically an upright rig that is rotated about the apparent wind vector.

I can do the vector work. Once I know the angle of attack and sweep, what do I do with the component along the span? If it is flowing toward the free end I would expect it adds to induced drag and if it flows toward the the closed end I would expect it adds to loading. Is there any simple way to quantify?

 

[brian eiland]

I must have been asleep at the wheel, or off doing something else. I missed all of these discussions, and only found it when I was reviewing old emails this morning.

I'm going to have to look thru some of these numerous video references when i get a little bit more time,....it looks to be interesting experimentation,....and some nice RC model control work.

BTW , mij did you pursue this further??

 

[mij]

BTW , mij did you pursue this further??

Brian,

I've built a couple more MAWS, but got a bit distracted trying to make rc boats foil. I tried variety of different wings on rc boats of various descriptions, and it was really only the MAWS that matched the performance of normal sails. I'm not sure why this was, perhaps the difficulty making a conventional wing work on a small scale. I put together a video that covers most of the wing sails I worked on:

https://www.youtube.com/watch?v=5hDNLyRLsMk



Jim.

 

[brian eiland]

Just looked back thru this subject thread, and it appears as though there were no 'soft-cloth' sails utilized,...is that correct??

All models basically utilized a two-part plastic foil to develop their airfoil shape?

Are there some model sailboats that use 'cloth' or cloth like materials in building their sails? ...sort of a miniature of big boats?? (I do not know much about model sailboats)

 

[mij]

Brian,

Virtually all rc sail boats use conventional non-rigid sails.

Jim.

 

[brian eiland]

...and these are constructed by assembling panels of material to get different contour shapes and draft locations?

 

[mij]

correct