Dear Gentlemen,
I am engineering student and at University we have a task to design and build a land yacht / Blokart.
The problem is - the sail design. Can you give me please any links or advices how to design it?
mast height should be about 4.5m.
Available materials:
Steel hollow bars - 25,40,50 mm
Steel solid bars - 3,6,10 mm
Please help me out with any resource or advice.
Thank you very much for your time.
Best regards...
Right Artz,
Before designing your sail I would suggest that you looked carefully at several things i.e Chassis design, Wheel size you are to use, Surface to be sailed on, your intent for the Land Yacht etc. All things in design affect the other. Looking at the surface to be sailed on for instance If you are to sail Car Parks you do not require a Flat Speed sail as your speeds will not be all that fast but a sail with a fuller Belly will give adequate speed and lots of power to pick up lost speed in turns, the same sail will be good on grass or other soft surfaces. A Flatter sail is more for higher speeds and good to run on Large Tarmac Areas, an Airfield perhaps this sail would also be great for sailing on Hard Packed Sand. I would also suggest that you get all your parameters together and discuss sails with a local Sail Maker, ensuring he applies principles based in extreme sailing. Also study these pages and note designs in all aspects. I would also suggest that you go for a simple design Like a Lake LeFroy Mini
As they are about the simplest type of Land Yacht. My Schrödinger's Cat is based around that Class. Masts are best made from Aluminum Tube or a secondhand/used Sail Board Mast.
As you come to each part you should discuss it with members of this forum to ensure the best you can build.
It seems that everyone will help everyone else..
Ron
Arts,
The whole thing in my opinion is about average Rolling Resistance, the lower the resistance the faster you are able to travel. I believe a sail should be designed about this fact. As I have already said Lower resistance allows for more speed, higher resistance is the reverse then by adding the other factors you can come up with a design suited to your requirements. Start talking to us in these terms and we should be able to steer you in the right direction. You can learn the terms as we go.
Ron
Artz- we have had a lot of students contact us in the past, with similar requests.
Can you tell us exactly what your university is asking you to build?
We gave a lot of advice to one student - which should have ended up with a fantastic landyacht, but we didnt find out until it was too late that the university had restrictions on materials, many dimensions, and speed.
Are you only allowed to use the steel of the sizes you listed?
What about seating and bodywork?
Or the mast? 4.5m of what? steel, aluminium, bamboo, recycled fibreglass or carbon fibre windsurfing masts?
Sails- are they allowing recycled windsufing sails, or do you have to make them yourself from either cloth, ripstop nylon, poly tarp, tyvek, or whatever.
Does your landyacht have to meet performance goals?
Will it be required to complete a circuit of some type, or reach certain speeds- or just beat the opposition?
Which university do you attend? We might have someone nearby who can give you some sailing time so you can get a feel of what you are getting into.
If we had known all this in advance- we would have given much different advice to the previous students.
We dont mind helping with advice- but, remember that you are expected to do the hard bits.
We (and your university) want you to learn by doing- not just picking up a set of plans from someone.
Get back to us as soon as you can with more details- as many of these projects seem to run short of time and do not get completed properly.
All the best,
Stephen.
Gday artz, could you tell us more about the hollow bar your using. if you intend using it for a mast we need to know( as do you what kind of steel it is . for us Hollow Bar is a really heavy walled mild steel,annealed for bending
Thanks a lot for your response!
I will be happy to hear any advices or directions where possible to find information.
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Brief Design Specifications:
The school of Engineering allocates a budget of £200 per group.
Maximum dimensions: width - 1.8m, length - 2.0m and height is 4.5m to the tip of the mast.
The boom and mast must be made of round section, straight metal tube, maximum boom length is 2.5m.
An effective brake must be applicable to at least one wheel (Calculations Required).
Steering linkages to be solid rod or tensioned cables, all spindles/couplings in the linkage to be min 3mm dia. acting through appropriate bearings, bushes or couplings.
All parts to be bolted, riveted or welded together and high stress areas to be supported by gussets (Calculations Required).
Steering can be foot or hand operated.
Wheel spindles (If not already with the wheel) to be minimum 10mm dia. if supported at both sides, or 15mm dia otherwise.
Axle and wheel alignment to +/- 5mm or better (Dimensions Required).
The lowest point of the boom or sail must not be below 500mm or pilot head height whichever is the higher.
Brief materials specifications:
Note the maximum sizes allowable:
Maximum diameter of steel round bar = 20mm
Maximum diameter of Aluminium or steel tube = 2”
Rectangular hollow section maximum 2” x 2”
Got design specifications at 2x A4, wrote down the most important ones (in my view).
TEST & RACE
SITE: Aberdeen Beach
Race Track length: 100m
Number of race runs : 3
Main criteria: BEST TIME WINS. (Get fast as you can!)
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So far:
For wheels decided to go for Wheelbarrow wheels.
However:
Still thinking about Rolling Resistance, due sand on the beach.
At this moment I am completing frame design in Solidworks, doing something similar to Blowkart. I will show it up as soon as possible, I will appreciate any feedback.
Sail - still ;( not good, no idea how to shape it and build it, to get good aerodynamics.
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Dear landyacht,
We can use aluminium or steel materials. Thinking about aluminium.
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Dear Stephen,
I wrote specifications, I hope it is enough to get idea what we going for, if I miss something please ask.
I am from UK, Scotland, The Robert Gordon University.
Goal is to get best time for straight 100m.
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Thank you a lot for your time.
Regards, Art
Brake:- Front wheel would be best. You could adapt a bicycle disc brake to fit, depending on fork configuration.
Rear wheel brakes are problematic depending on wind directions and so would require one on each wheel. 2 brakes 2 hands? Rear brakes though are good as an assist to turning when racing
Speed:- Depending on wind direction and strength for sail shape/size.
Wheel:- Soft sand - wide tire. Hard sand - narrower tyre faster(less rolling resistance)
given it only has to sail 100m races , go as simple and light as possible,with as big a sail as you can fit on.
the brake need only be a simple stick digging in the sand,cos your only going 100m.
light ,light ,light
Can you suggest please any material for reading, about designing and building a sail? 
Here is a link of how to modify a sailboard sail to suit land yachts....
www.seabreeze.com.au/forums/Land-Yacht-Sailing/Sail-making/How-I-recut-sailboard-sails-to-suit-landyachts/
If you want to get a bit more serious in reading about aerodynamics....
cdn2.hubspot.net/hub/209338/news/Ad_aerodynamics/index.htm
