488 posts
Cameron, I have been thinking overnight.
I am not sure what your project is really about, but if it's to learn some design, and fabricate it, then a bit of re-invention won't hurt. It may not be as good as the Lake Lefroy Mini (probably not cos Paul and others have learned what I am about to suggest and moved on) but you will learn a lot of basics.
In the "good old days" I built well over 100 yachts before I gave up. In the end I had a "recipe" in mind which I had learned from a lot of mistakes and adventures beyond the square. I could give you that recipe, but you won't have learned anything, except to take other peoples ideas, and the success of the Blokart is because Paul Beckett ALWAYS thinks outside the square. If you are looking at the cost as a factor of the BK, remember it is a COMMERCIAL success, it has margins for retailers, margins for advertising, marketing etc etc. The raw cost when it is on the factory floor would be substantially lower, but look how many have been sold all over the world, he has done a great deal of stuff well.
Now to learn a bit about design. Make something really basic with wheels on, this does NOT have to sail, just a 3 wheel platform of the size you are contemplating. I used bits of 4x2 in the first trial, does not have to steer or anything.
Put a seat of some sort where you think it should be. Now get a few mates and a bit of rope. Put your "thing" on a patch of loose gravel, or wet grass, tie the rope on to the centre line, sit in the seat, and have your mates try to pull it sideways. move the rope backwards and forwards till it goes EXACTLY sideways, not front or back first. This is the "centre of lateral resistance" While you are at it, try to balance the whole thing with you on it on a pivot. This shows the "centre of gravity". Now playing with tyre pressures may make some changes try anything you can think of to change either of these positions. RECORD everything. When both positions co-incide you will have the sweetest yacht (almost impossible to be exact, but you can get very close)
The next exercise is to find the "theoretical centre of pressure" of the rig. With the strange shape of sails this is not too easy. You will see some very clever stuff about this on the forum. I am not that clever to calculate the different effect of mast curve etc, so I make a cardboard model of the shape, then hang each corner from a pin with a plumb line, pencil mark where the plumb line runs across the "sail", move to the next corner, etc, and you should wind up with a 3 part cross. This the initial "centre of pressure". According to the scientists the real one is somewhat forward of this due to aerodynamics, sail shape etc, but it's good enough.
Now you transpose this onto your plan. If you have your cardboard sail at the same scale as your drawings it's much easier! Landyachts seem to work best when the 3 bits above, Cof G, CLR, CoP, all co-incide.
TOO much science, but all the top designers of anything have to throw science in somewhere, even the arse kicking machine on this forum has some of that!
Good luck, you could be the next Paul Day!, Don't be afraid to innovate, copying slavishly will have you at the same level, innovating may well have you well behind, may also be the next quantum leap!
NSW
78 posts
thanks guys i just need 3 more surveys?
SA
2865 posts
Cameron, here is my reply for you.....
1.What do you think of my design which involves steering with your feet , very comfortable seat and skis to hydroplane and go on un-even sand?
While foot steering is regarded as the standard i actually prefer hand steering "tiller style" as this enables you to steer the yacht as well as push it out of a soft sand bog if needed. I also feel you need to more research on how much force you will need to use skis on soft sand before you build the yacht
2.How do home made land yachts compare to the commercial Blo Kart?
Blokarts are a nice commercial package but while they have many good points like one design and close racing it does stifle some development within the sport.
3.How popular / well known are land yachts? Do you think many people know about them?
The sport has a very small public image but most people have thought of the idea at some time in their life.
4.Would you like to see a surge of home made land yachts that perform as well as Blo Karts but are a fraction of the price?
Producing your own yacht will most times be of less cost as there is no labour costs, But some people will never make their own due to limited knowledge of tool, welding, etc and there are others that "just want it now" and will buy a yacht.
5. If someone produced a cheaper land yacht that performed well would you consider purchasing one?
No i wouldn't as im into building and experimenting with things
488 posts
Hi All, sorry if my previous was deemed to have "too much information". The other half in this household is a teacher of year 13 (amongst other) technology Our year 13 = your year 12.
Students here to get a reasonable mark are expected to have researched, and show their research, why existing designs of a "parallel product" are designed the way they are.
I will shut up now.
Good luck Cameron, again, don't be scared to go outside the square.
488 posts
Cisco, I think this may be a questionaire that Cameron formulated, not his teacher?
Paul, kite buggy wheel, how do they cope with side loads, soft sand they work well as the kite gives substantial lift when needed.
Kids finished school, wait till they hit Uni, the fees are even higher!
NSW
78 posts
another thing i was thinking 4 wheels instead of 3? would this work? why dont any of them have 4 wheels
SA
2865 posts
4 wheel landyachts have been discussed on previous threads on seabreeze, the problem is the increased drag of the wheels / bearings which slows the yacht down, with little or no benefits.
The only use of a 4 wheel yacht would be to sail on tracks like in a padock, but this would be very uncommon.
488 posts
Cameron, I had totally forgotten about a yacht (actually a fleet of them certainly more than 6) which Jean Philippe Krischer (Mr Seagull) built in the late 1980's. These looked just like a go kart, 8" wheels, fibreglass kart seat etc. The mast was just a little in front of the steering wheel. Sail area, my guess around 3.5 sq metre. The flatform was around the size of a go kart. Of course the rear wheels were not on a common axle.
From memory they were for a hire /school operation.
My job was to test sail them on the roads around Tours in France where they then lived. The reason I had to do it, was that if (or when ) the police caught me I could say that i was just a Kiwi who knew no better, Pardonnez moi monsieur!
If JP had done it, there would have been big fines etc. Actually I did not get caught. They were huge fun.
Nord Embroden had a 4 wheeler, called "The Door", cos that what it was like. Again apparently lots of fun, but not a serious yacht.
488 posts
Cameron, we could tell you, but it's time you tried a bit to learn for yourself. You need some maths for what you are doing. Your maths teacher will explain what area is.(and how to calculate it).
How about you trot along to him/her and ask for help? This is an incredibly basic question.
NSW
78 posts
yeah i know that triangles are 1/2 bh but i thought it must not of been that simple so if i want a sail 4.8 x 1.8 it will be 8.64/2 = 4.32 sqm?
will any wind surfer sail work or it it any certain one? where do i get a mast and boom from?
488 posts
Hilsy, I was trying to encourage this young lad to learn for himself!
life , love, education, cars, dress, and land yacht building 
....cheers Joe 
