3D Printed Landsail with Rigid Wing

This post outlines the design, printing and assembly of a 3D printed landsail with a rigid wing as a sail. Landsailing is a sport that applies the principles of sailing to land vehicles for propulsion. A lightweight wheeled vehicle is fitted with a mast and sail which uses wind-induced lift to provide thrust to the vehicle.

A landsail
A landsail

Landsails are quite fascinating vehicles that can move at several times the wind speed if properly designed. As an example, below is a video from a recent landsail speed record:

Instead of a fabric sail some designs use a rigid wing, which functions much like an airplane wing and is generally said to have greater efficiency. Such a vehicle is shown in the video above.

The RC landsail whose build is outlined in this post
The RC landsail whose build is outlined in this post

Landsails are also popular in the RC vehicles world. In the case of RC two servos connected to the receiver provide steering and sail control. With the widespread use of 3D printing it is easy to design and manufacture the components needed to realize an RC landsail. In the sections below I will outline such a build that anyone can realize using 3D printed parts and off-the-shelf structural components and electronics. Excluding some linear elements such as beams and the sail mast, as well as the tires, the rest of the vehicle is completely 3D printed.

Materials List

First things first, here are the materials that I have used in this build:

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  • 2x Rectangular Carbon Fiber beams, 60mm and 40mm (aluminum are also fine)
  • 2x Micro Servo (MG90S or similar)
  • 8x bearings (4mm inner, 8mm outer dimension)
  • 4x Makeblock Threaded Shaft 4x39mm
  • Around 20 10mm M3 machine bolts
  • Around 10 M3 nuts

The bearings and threaded shafts are optional and one can use whatever mount lets a wheel spin really. In addition, even though lightweight the MG90S servos seem to be at the edge of their performance when pulling against the wing and steering. Larger servos could provide more control and lead a longer life!

Landsail Frame

The Landsail frame is a typical T-planform with three wheels, one on each corner of the triangle formed by the frame. The beams are rectangular carbon fiber beams that are connected to each other with 3D printed joints. The carbon fiber beams also serve to mount components such as electronics, mast, wheels and steering. All 3D printed components are printed in PLA. They either press fit onto the beams or fix by means of machine bolts. Usually it is enough for the friction between the plastic parts and the bolts to hold them together. However, on critical components such as the mast nuts are added for additional safety and better fit.

Landsail showing the frame geometry
Landsail showing the frame geometry

Landsail Wing

The wing form results from a sweep of an airfoil profile over two curved rails, aligned at the front and the rear of the foil. An objective in designing the wing geometry is to reduce the weight of the wing as much as possible. This is so that the center of gravity of the vehicle can be kept low. Thus I designed and printed the wing with a single 0.4mm perimeter and two 0.4mm lateral reinforcements. In addition to that, there is a tube for the mast to go through and secure the wing, which has 0.8mm thickness for increased durability.

Read also:  Quadruped Robot Part II: Assembly, Electronics
Landsail detail showing the wing sail profile
Landsail detail showing the wing sail profile

As with the other 3D printed parts, the wing is printed in PLA. To accommodate for my printer’s small bed size, the wing prints in four parts. The print speed is set to quite low value (7.5mm/sec), to accommodate for the very thin sections. This setting results in a precise and well-finished print.

Gluing the parts of the wing together has been the most challenging part of the wing construction. Due to the minimal area available I had to resort to a trick to achieve good adhesion and part alignment. I left part of the brim that I used to secure the parts on the print bed while printing, and aligned it with the top edge of the part below, using the mast as a guide. Thus the contact area grew at least on one side, and the parts remained aligned as they were supported by the mast. I used 5 min epoxy glue to fix the wing parts together.

Landsail Control Mechanism

Control of the rigid wing is performed by means of constraining it so that it meets the wind at an angle. If left unconstrained, the wing will follow the wind to whatever angle it comes from. The pilot needs to adjust the constrain amount so that the angle is neither too narrow nor too wide. This is where the best thrust can be achieved. When cruising downwind, it is also possible to let the wing move on one side, so that it provides drag thrust instead of lift thrust. A servo controls the length of a control line made of nylon thread, which is fastened on the frame on one side and on the wing on the other.

Rigid wing control line, connected to servo
Rigid wing control line, connected to servo

Steering is simple and uses a bicycle-style mechanism, with a servo controlling the steering angle through an adjustable rod.

Landsail steering arrangement
Landsail steering arrangement

Landsail Electronics

The elctronics is probably the simplest part of the landsail construction. All you need is two servos and a 2-channel capable receiver. All pistol style or aircraft style tx/rx combos should work fine. I’ve used a Radiolink R9D receiver paired with a Radiolink AT9 9-channel transmitter, which is overkill for this simple machine, but that’s what I have. Power requirements are also minimal since the battery needs only operate the receiver and occasionally the servos. I went for a small 350mah LiPo, which gives a run time of well over an hour when fully charged, and with the vehicle idling most of the time..

Control electronics: Two servos connected to an RC receiver
Control electronics: Two servos connected to an RC receiver

Testing

Unfortunately testing is postponed until we’re able to catch some good winds in my area, as the weather has been alternating between totally calm and hurricane-like for the past few weeks! I hope that within the next couple weeks I’ll have a chance to visit a nice flat area where to test the landsail. Stay tuned!

Conclusion

This post went over the design, 3D printing and assembly of a RC controlled landsail with a rigid wing. Overall it is a very simple vehicle that can give quite the excitement. Hopefully the weather around here will soon get a bit breezy so that this beast can be seen in action eventually!

Have you built or piloted a landsail? Share your experience in the comments below!

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