Over the last 8-9 months I've been playing with foam wing sails for small trimarans, cats and monohulls. To be honest, they aren't aren't carefully engineered, finely made structures, but they are quite easy and quick to make, and quite light. I thought that I would start a thread to describe the wing I am currently working on and the methods I am using.
To begin with I should admit that I'm not an expert on sails or aerodynamics, so I am generally copying shapes and profiles. My real focus has been on trying to develop a wing that works reliably and is light, but reasonably robust. As I get closer to achieving this I'm starting to focus more attention on the actual performance. The wing that I am currently working on is for a 700 mm trimaran. Two aspects of this wing are somewhat different to my previous efforts. The wings I have made to date have been quite thin airfoils, as these are easy to make with Depron foam. With this wing I have basically tried to copy the ENTZ wing, so the front element airfoil is quite thick. Watching the AC72s, I've been impressed by the amount of twist in the front element. In an attempt to introduce similar twist in this wing the front element is divided into several sections that can rotate relative to one another.
The photo below shows the bottom front element:
The airfoil shapes (3 in each section of the front element) and centre structure are made from 6 mm Depron foam, while the outer shell is 2 mm foam. The flaps are a single piece of 3 mm foam (this is actually also different to my previous wings which have had airfoils shaped flaps). The whole structure is stuck together with tape. Double sided sail making tape for the internal joins, and heavy duty single sided tape on the outside.
In order to make the foam follow the desired profile a blade was used to cut lines part way through the foam, each a few mm apart. All sections that had been cut were then taped. The finish wasn't perfectly smooth, but wasn't too bad. This technique isn't necessary for thinner airfoils.
Below are some photos of different aspects of the construction.
Control of the angle of the flaps is achieved using a servo mounted in the base of the wing:
The front elements and flaps are joined using thin aluminium tubes connected to each edge with carbon rod joining them:
A line passed through the rear of each front element section, that could be used to control the extent of twist:
Twist was also controlled by cords of adjustable length connecting the flaps:
The amount of slack in the cord running through the rear of the front elements (and hence twist in the wing) could be adjusted at the top of the wing.
The height of the wing is 1100 mm, and the weight 210 g.
The following photos attempt to show the twist in the wing, and how the twist resets on tacking:
The boat on the water:
To begin with I should admit that I'm not an expert on sails or aerodynamics, so I am generally copying shapes and profiles. My real focus has been on trying to develop a wing that works reliably and is light, but reasonably robust. As I get closer to achieving this I'm starting to focus more attention on the actual performance. The wing that I am currently working on is for a 700 mm trimaran. Two aspects of this wing are somewhat different to my previous efforts. The wings I have made to date have been quite thin airfoils, as these are easy to make with Depron foam. With this wing I have basically tried to copy the ENTZ wing, so the front element airfoil is quite thick. Watching the AC72s, I've been impressed by the amount of twist in the front element. In an attempt to introduce similar twist in this wing the front element is divided into several sections that can rotate relative to one another.
The photo below shows the bottom front element:
The airfoil shapes (3 in each section of the front element) and centre structure are made from 6 mm Depron foam, while the outer shell is 2 mm foam. The flaps are a single piece of 3 mm foam (this is actually also different to my previous wings which have had airfoils shaped flaps). The whole structure is stuck together with tape. Double sided sail making tape for the internal joins, and heavy duty single sided tape on the outside.
In order to make the foam follow the desired profile a blade was used to cut lines part way through the foam, each a few mm apart. All sections that had been cut were then taped. The finish wasn't perfectly smooth, but wasn't too bad. This technique isn't necessary for thinner airfoils.
Below are some photos of different aspects of the construction.
Control of the angle of the flaps is achieved using a servo mounted in the base of the wing:
The front elements and flaps are joined using thin aluminium tubes connected to each edge with carbon rod joining them:
A line passed through the rear of each front element section, that could be used to control the extent of twist:
Twist was also controlled by cords of adjustable length connecting the flaps:
The amount of slack in the cord running through the rear of the front elements (and hence twist in the wing) could be adjusted at the top of the wing.
The height of the wing is 1100 mm, and the weight 210 g.
The following photos attempt to show the twist in the wing, and how the twist resets on tacking:
The boat on the water:
