Hi all, I'm new here, and totally new to land yachting.

I'm a Mech Engineering student and a team of us have recently been tasked with designing and building a land yacht. I've been trying to do some research, but I'm finding information is scattered.

I've been browsing this forum and gleaned some useful information, but I'm wondering if anyone would be able to help me out and give a big picture overview of land yacht design. Particularly highlighting important things that could easily go missed during design.

Or just pointing in the direction of any useful sites or books would be appreciated too.

Any advice much appreciated.

At the top of the construction page is a link to "build a landyacht- lake lefroy mini landyacht"- this has the basic design for one of the most successful home- built landyachts you will find.(More likely THE most successful)

There are a few variations and improvements- but the basic design cant be beaten.

-keep your centre of gravity low,
-keep to the 5.6m rope rule,
-if possible- 4.00 x 8 wheelbarrow type wheels with sealed bearings.
-follow the geometry and dimensions of the chassis, steering and mast step and it will pretty much work.

Quality wheels are worth buying as they will be taking a lot of side stress.

These landyachts are capable of scary speed performance- with a good pilot and the right conditions, it is possible to break the 100km barrier!

You do need a decent venue to sail in- something like a disused airstrip, or a dry lake bed- or if you are currently frozen like much of Europe- how about ski's for snow or skates for ice- or easily convertable for all 3.

We have a regular stream of students arriving on this website looking for assistance with thier projects- many expecting us to provide all the answers for them.
We dont mind helping with genuine enquiries- but we expect you to do your legwork and research- after all- you are expected by your examiners to do this project under your own steam.

All the best- and if you need some assistance- please ask!

stephen.

Maybe the lecturer bases the assignments on this site

Nikrum said...


Gees! I was going to suggest that you look for a book, "Landsailing from RC to the Big Ones". Bloody Hell the owners of these are now taking advantage of the sports growing popularity as the best I could find was $87 on Amazon.com..

The book is a good one for an insight into the sport and craft. Paul Day Alias Landyacht has a book out on Land Yachts at $60 which I intend to purchase next pay.. Ask him about its contents.. The only other thing I will add to what has already been said is "The KISS Principle" and Apply Occam's Razor (lex parsimoniae). to all designs. Strength, Lightness, Efficiency.
Ron

thats susan day alias promogirl, I just cooked while she worked, its more historical , less technical

tomjp said...

Thanks for help :)

I was just hoping people with experience of actually driving these things would maybe highlight any issues in design that were commonly missed. I still have to actually 'engineer' the thing - it's just easy to miss practicalities when you've got no experience of driving one.

I think you need to drive/ride/sail one of these things before you go any further Tom. The experience will most likely alter your brain chemistry.
Let us know where you are and I am sure we could find someone with "one of these things" who would be happy top accomodate you.

For H&S reasons the design constraints put a major damper on speed, (based on class 5 but with a minimum weight + shortened mast).

Why would you do that!!?? The only reason we build these things is to get our Speed Jollys!!

And H&S, why would any of us build a thing that would only give one dose of fatal Speed Jollys. H&S is our most important consideration because we want to just keep coming back to the playa to have FUN.

We always promote use of correct PPE (clothing, eye wear, foot wear, helmets and gloves) as well as safe practice in proximity to other land sailors and in particular the general public.

Budget is also very low, so it won't be as polished as those on this site.

Polished efforts achieved on low budgets is a major ethic here. Like I said, dredge through the posts and you will get the picture.

Speaking of pictures, start here and work your way forward. There are 4700 odd pictures on 150 odd pages (a picture is worth a thousand words).




When it's all done I'll post some pictures of the 3D models, the built yacht, and hopefully some of it being sailed too. Wish me luck!

You don't need LUCK. The harder you work the LUCKIER you get.

good modeling but.......dimensions are wrong, rear wheel width x at least 2

for chassi lenght otherwise one would never retain/master directional control

Looks good. Like the rear wheel triangulation and fork combo. Would look at front and triangulate to mast step support possibly to stiffen up front end. Think it will go if it gets built.

Tom,
To be painfully Frank, Your design , though it is a start is not what I would be sticking with. The essence of a good land yacht is the KISS principle..

These things have been around for a very long time in many formations and so the modern Land Yacht such as those that landyacht, aus230 and TP1 are building are really a distillation of their predecessors. My suggestion to you is look closely at any of the known Plans, preferably the most efficient ones and tinker from their but do not go too far outside known parameters. I am lucky in that I can look at some of the units around and see the balance and ideas that I need to use. Sure I do get things wrong here and there but trial and error is my style but my yachts are fairly efficient. You can redesign as much as you wish but when will Aesthetics conflict with efficiency. For instance:
When I decided to build a Carbon Fiber unit (The original Schrodinger's Cat) The only Steel in the frame was the "Rear "T" part of the Chassis and Steering Head.
I went to a lot of trouble setting up the Mast Step. Yep It did look good, least ways to my eye. Picture Upload Failed??

The Cat was launched and performed really well until one fine day I took it to Pegg's Beach and stronger winds and again it performed great until I made a sudden turn in a strong gust and Crunch I finished up with the mast and step laying across my legs with no harm to me,,,,,except maybe my pride. What I learned from that exercise is that much CF could be used but at least the Chassis "T" to just in front of the Mast Step should be built of steel to take the torsion loads from the mast and sail. Those are a few pointers and no doubt the guys could add a lot more to those experiences and thoughts..

You may well be a student but I bet your Instructors didn't expound the IMPORTANCE of discussion and experience. It may well be that you don't have a lot of the latter BUT you can always draw on the experience of others. From discussion comes ideas which can be cast about until you Distill the very best you can and put that down on your PC Program.
Like one or two members are inclined to say, Chew on it , Suck on it, toss it about and spit out the rubbish.
Ron

PS; Most likely your design will work but will it be efficient?? Will it stand up to the rigors of use etc? But most importantly "Will it be as safe as possible?"

If I'm looking at it correctly, it looks like you'll only be able to steer it a few degrees in either direction. If you mount the foot rests to the sides of the forks instead of the top of the stem, the long drop bars won't hit the fore/aft frame bars, and will allow a sharp turn

tomjp said...

Not sure whether you're talking about the actual wheel width, or chassis width.

If it's wheel width, then yes, the wheel modelling isn't accurate because there are no tyres on those rims, and I gave the rims an arbitrary width because I didn't have any real dimensions to base them on. Their diameter is correct, but not width.

If you're referring to chassis width, the wheelbase is 1.8m wide and 2m long, and I don't know why you'd think that width should be doubled!

I'd also add that the centre of gravity looks to be very forward (due to the seat position). This would make the steering heav and the yacht less efficient (if speed is the goal). This may not be the case and is only an illusion due to the angle the drawings at.

What wheels are you planning to use, looks to be large dia. bike wheels. These whould have to be pretty beefy to deal with the stresses involved. Just a couple of my thoughts...

I see tom is starting to get into a bit of a predicament. Although I agree the design is not as efficient as other yachts, his requirement is actually to prove to his lecturers that he can apply his knowledge. The best design may well come from modification of the standard LLF mini, but will that get him the marks he needs, or land him in a plagerism storm?

One of the hardest things to do in the design process is dicvorcing all "prior knowledge" and trying to move in a new direction. A successull design however is usually the result of several failed concepts.

Tom, my 2 cents, your starting point should be identifying the specific problems you need to address. (define the problem) Think, application, weight, materials, price, portability. Dosn't have to be the best of all of these. Could well be a heavy, cheap, fit into a handbag, play in the weekend sun, or a record breaking, titanium, screw the expense, weapon that needs a covered trailer to move. (please make the weapon)

...........Then again.......Engineering is a "different" approach to design.

Re: Steering. Is that the way the Class V steering works? It would seem to me that the pedal that you push should be on the outside of the turn. With this set up, the pedal you push will be on the inside of the turn. Which is correct?

Wow, quite a few replies, I'll do my best to cover the points that have been raised here. It's important to note that we are not building a land yacht for our our satisfaction, there is a design brief outlining specific design requirements. One of the notable ones is that is must weigh at least 50kg, so while a nicely designed lightweight chassis would be the way to go as a hobbyist, it's not much good for this particular situation.

It's just like grlynch said. I readily admit this design is not what I would do if I was building a landyacht for my own sake, but given the requirements for price, size, weight etc, we were never going to end up with something like the ones on this site.

Most of all, thanks for the encouragement!

That said, onto the technical observations...

Steering linkage:

Yes it's push right to go right. The reason being that from a side view, the pedals are quite close to the wheel, and when the right pedal is pushed forward, if the wheel turned left, the driver would likely kick the wheel.
Desertyank - Yes it has a very limited turning angle. +/- 30deg to be precise - this was one of the requirements of the design brief. I think the university goes a bit overboard with safety because they don't want any students to get injured. If the wheel could turn nice and tight, there would be a greater chance of the driver causing the yacht to flip by turning too tightly too suddenly. Having said that I don't think you're looking at the drawing right, the pedals move forward and backward, not side to side.
The rather complicated linkage was unfortunately the only reasonable solution we could come up with, given the length of the yacht, the position of the drivers feet, and the position of the steering head. We spent a few hours scratching our heads over the steering actually, we considered a lot of different concepts.
Test Pilot 1 - if I'm understanding you, I think you need to look a bit more closely.

CoG:

Yes, I would've liked it a bit further back, but given the 2m max length (from design brief), it was very difficult to place the seat in any other position. If we make the seat more upright perhaps, but I don't think it's worth losing sail height to move CoG back an inch or so.

Wheels:

Yes, I'm beginning to have doubts about the wheels myself :/ I took the advice of some British landyacht clubs who said plastic bmx wheels have been used successfully in the past. The ones on this model are 20" dia and cambered at 15 deg. Given the weight of this yacht, I'm getting cold feet about that decision as I think they might snap! Will have to have a think about that, but difficult to think of alternatives that are both affordable and fit into the design, and final fabrication drawings are to be submitted on Friday.

Chassis:

Nikrum - I'm with you in spirit, but we have to design this in a way which will get decent grades. Sadly, while you might like to think so, it's often not the most elegant designs that do, but the ones that are properly 'engineered' and designed.
Having said that, I think you're jumping to slightly the wrong conclusion about the chassis, it's a very simple design. Just a T shape with two struts for lateral strength. The "complicated bits" aren't really that complicated, they are just simple and very robust mounting points for rear wheels and mast.

Yeah, it's kind of an ongoing thing, but the timescale is a bit tight. I think that's intentional though.

I have noticed you have drawn a "bicycle" style of steering, most land yachts use a layover steering this is because when a bicycle turns its not just the steering that does the work the actual bike frame also leans over (landyachts don't).
With the steering you intend to use, the front end will jump or skip when the yacht turns.

is this where we should be