Inflatable Wing Sail

Hello to all.

I introduce myself; I am fond of windsurfing, kite, gliders and sailboats. Since I was young I was fascinated from aerodynamics and, thanks to my university studies at the Polytechnic of Torino, I had the opportunity to develop the project of the Inflatable Wing Sail.

To explain the idea I enclose my website, currently we are looking for some temerarious men disposed to test this new technology on their boat.

Thank you for your attention and Good Wind to Everybody!

Filo

www.velacore.it

 

Hi,

Uber-novice comment perhaps, but wouldn't you like to incorporate the mast itself into the design, to maximize efficiency? From your site:

velacore.it/VelaCore/Technology_2_files/droppedImage.jpg

 

for sure! This is not difficult and we planned to do in different ways

 

I am not sure I see any advantage. Thin foils have better L/d ratio and high stall angles, thickness is only useful to reduce weight when the foil itself is a part of the structure. fat foils always have high drag. In this case it is neither structure nor provides for a thin foil.

Para sails use the thickness to provide some structure to the shape that is created by the ram air.

There would be some advantage if you change your design: use a less costly round mast that is inside the sail envelope at the LE of the foil, and use the inflated chambers to create a favorable foil shape behind the mast. I have tinkered with a similar idea but use battens to hold the shape rather than air chambers, the battens are still necessary to maintain a good shape on the aft third of the foil for favorable pressure recovery.

 

Some years back Alinghi was testing inflatable battens

 

Inflatable battens are now common on big sails.

 

The sketch shows a nice perimeter curve outside the bladders. I don't really see how this shape is maintained, particularly on the high pressure side.
I also suspect that the oblong like bladder shapes you have drawn will more closeley resemble circles when you inflate them, requiring more circles to fill the gap you seem keen to fill.

Unless I've missed something this looks like a solution looking for a problem to solve.

 

CFD modelling

Have you done some 3D CFD/FSI modeling with your inflatable wing sail, which clearly show that this sail works better than a conventional sail?

Seems to me that the recirculation areas shown on your picture below, are really huge and do not reflect reality.

The mast is not a drag device.
.

 

Inflatable battens work well, but are rather horizontal. What is the advantage of the vertical bladders compared to a double mainsail. I can't remember the name, but there is a sail on each side of the mast. Downwind they can run wing on wing.

 

dont like it but attached a pic of a vertical blow-up mast/sail
with horizontal blow-up port and starbord battens you may influence the camber
posted planty blowup sails with pics in the past that were try'd and worked well, just finding them back
even drew my own blow-up and strikable wingmast ladybird fantasy
the link there got broken in time but there were more good possibility's

 

I thought the thick sail was to get some "Bernoulli's principle".

Some guy from a college sailing team was telling me it isn't that the air "pushes" the boat, it is that the vacuum created behind the sails "pulls" the boat.

 

you get a force or thrust out of a fluid when you accelerate, or curve it. A thick foil does not curve or accelerate as much fluid as a thin one. do not confuse thickness with camber (or curvature). the mean camber line is what determines the amount of fluid acceleration not the thickness.

 

You need to add energy to a system to accelerate it. In an airplane wing, that is accomplished with the thrust of the engines. A sailboat is not operating in that mode. It takes energy from the system which is a mass of air moving in relation with the water. A sail diverts and disturbs airflow and takes some energy from it.

 

looking at these cfd's was thinking that too
as drag on a van (pic attached) seems to be mostly on the rear as well
was checking if drag went up or down with bike rack
with you like to hear from the experts or re-read some books

here the inflatable bi-sail i imagined on strikable masts
vertical blow-up wing shown in post above
comes from a nasa site that took much info down

a question: as sails become more efficient with speed, how much would that be on a motosaling cat, say at 20knt