I understand the width to length ratio, the reasoning in centering and moving the weight far back as possible, with in reason and why it is important to align the pivot center to to the front of the front tire patch, but I don't know how to determine where to put the mast step
. Can anyone please tell me without being to technical how to do this
. I don't have a degree in rocket science, but I do have an associates degree in applied science which doesn't say much 
. I surely would appreciate it very much 
. Please! . If I missed it in a thread please let me know where .
Don't know what size yacht you are building but if you look at the Pacific Magic Plans, (go news top of this page and click articles to find them) or have a look at Paul Day's thread on Build a Lake Lefroy Mini (the thread at the top of this page)you will get an idea of the ratio between yacht length and mast position. Both these yachts are very successful so if you use them as a yard stick you should get a good result.Cheers Cisco
All sailcraft water or land use this as a basic principle.
The effort generated by the sail could in theory be focused as one point on the sail, this is called the centre of effort (CE)
On the other side, is the centre of resistance (CR) and in a land yacht it would be that point that if pushed would move the yacht sideways.
As landyachts have 3 wheels and most of the weight is on the rear wheels / axle becomes the CR.
I have always tried to keep approx 5kg down force on the front wheel ( in soft stuff like mud you might need more and on hard surface like salt you might get away with less and also how fast and tight you might need to turn)
If the CE is well infront of CR the yacht will try and turn down wind and the opposite is true if CE is well behind CR the yacht will try and go up into the wind.
This is infact the way sailboards turn, its by moving the CE forward or back.
So infact the CE will move if the mast is raked forward or back and it constanly changes with sail sheeting as well.
I hope this has answered your question of where to put the mast step..but in a round about way.
I have tried to show this on a picture. where the orange lines cross is the CE these lines are the diagonal points of the sail.
The pic was the best i could find as it was not exactly side on.
Here is a pic of a Lefroy mini as you can see the CE is directly over CR and this result in a very directionally stable yacht. (well done Paul)
Excellent explanation there Brian.
I confess, I did take the lazy and simplistic way out to answer the question.
I promise I will download the free CAD program and learn how to use it.
Some years ago I owned a Peterson 42 which was an IOR 2 tonner called "ENVY II". Her mast position was well aft in comparison to most yachts, being directly in line with the forefoot of the keel. The result was that when going to windward the yacht derived most of it's power from the fore sail and the high aspect ratio mainsail served mainly to balance the yacht. With the mainsail only hoisted the yacht was almost dead in the water.
The effect was so much so that in light to medium airs I would sail with the No.2 genoa only with the boom tent erected and the yacht was well balanced and the crew were in the shade. Cheers Cisco
Thanks Cisco and Gizmo. That answers my question. The mini spects are pretty much set and under stood, however with the PM I wasen't quite sure how the C bar compared in length to the fork of another class 5. I guess what a person could do is make a sliding mast step via a clamp system and experimenting before permanently welding the mast step. What do you think?
Oh! One thing I forgot to ask was what is the diamater and wall thickness of a C5 fork tube I fell in love with the promo LY made for his wife. That is one beeeeautiful machine. While drooling over it got me to wondering about this and the question I opened the thred with.
Pipe fo front forks is galvanized water pipe , 1"ID . 4mm wall
Suggested mast step psition is 1085mm from centre of front axle. this was the measurement from the fastest promo in Argentina.
. dont let your weight get too far back. when rigged and sheeted , with plot in yacht youll want about 7+ kg over the front wheel (clay ) or 11kg + on sand
Thanks LY your right on top. In reading my private message you'll understand why I asked that question.
While doing the CE-CR line drawings i thought to have a look at the "Sandpiper" yacht.
It was very twitchy sailing under main sail only but was a lot more stable when a jib was added. (but did cause turning problems)
So infact moving the CE approx 250mm forward in this case made a huge difference.
If any one knows of a good side on pic of a blowkart please post it, (im happy to do the line stuff) it would be good to see how that compares also.
Or even any other yacht you would like checked.
Brian, what is your method for determining the CE?
If you are taking it as the two dimensional centre of the sail area, I must suggest it is a reasonable guesstimate only.
When you look at the cross sectional shape of the sail under load, the point of effort is located at or just behind the most curved part of the sail. Therefore, particularly for a land yacht sail the CE will be located closer to the luff or leading edge of the sail.
Your method for determining the CR (Centre of Lateral Resistance) is questionable too. When a land yacht is sailing, the windward rear wheel is doing little or nothing in contributing to lateral resistance. Therefore the CR is somewhere along the line between the leeward rear wheel and the front wheel.
In the case of a yacht that has three identical wheels, eg Lefroy Mini, the location of CR is a product of weight distribution between the leeward rear wheel and the front wheel. Therefore the CR is further forward than the centre of the rear wheels.
However their relative postitions on a vertical plane is the important factor here.
If Lake Lefroy was absolutely horizontal and smooth, wind conditions were absolutely constant and a Lefroy Mini's CE and CR were absolutely coincidental on a vertical plane, theoretically, Paul could put an 80kg bag of rice in a Mini, lock it's steering and sheeting and send it across the other side of the lake to the Chinamen at the gold mine over there.
They could then substitute the rice with an equivalent weight bag of gold, turn the Mini 180 degrees and send it back to Paul, who I am sure would be most chuffed about it.
Cheers Cisco
Yes you are right, the CE and CR points are theoretical positions, as land yachts are dynamic objects rather than static ones, the positions DO move.
For example the CE will change with the direction of the wind hitting the sail as well as the sheeting position, vang, outhaul, down haul adjustment will also change the position.
It should also be noted in most of the pics the sails are not even sheeted in as mast flex will also change the results.
I have adopted a simplistic way of determining the CE it is
1. From the head of the sail to half way along the sail foot.
2. From the clew to half way point in the luff.
3. From the tack to half way point on the leech.
Where these points intersect I have called CE.
The CR I have also assumed that if a yacht weighs a VERY approx 40kg and if there is an 80kg pilot total weight (yacht +pilot) is 120kg, and if there is 10kg on the front wheel the remaining 110kg is on the back wheels (55kg each).This puts the CR on or very close to the axle line.
This CR point will also change when sailing due to sailing conditions, angle of heeling as well as additional down forces caused by the sail and rig.
What I have tried to show is the comparisons between different yachts and how the rigs relate to real life and not scientific calculations.
I have also have assumed that maybe 60% of the people reading this subject didn’t even know that CE + CR existed before the thread was posted and I hope those people now have just a little more knowledge on the subject. If so my job is done!!
Now Cisco I can’t accept that ANYONE would willingly swap 80kg of gold for 80kg of rice let alone astute Asian business people.
Oh!!
Well at least we all seem to be having FUN!!
Sorry Brian, after you wouldn't let me get away with MY rule of thumb, ie "copy someone elses successful formula", I couldn't let you get away with YOURS.
As you say, when a landyacht gets going, it becomes dynamic like nothing else.
The only water yacht that comes near is "Hydroptere". Type that or "the fastest yacht on the planet" into the search bar on YouTube and see something spectacular. Like a gnats whisker under 50 knots.
Back to "Rules of Thumb", herein after called ROT, I think yours is very good and sets up a starting point with the construction of a yacht that will give a good platform upon which to build fine tuning.
If we were to load up a landyacht with all the sensors to record all of the dynamics that come into play, it would probably be so heavy that it would not sail. If through minitureisation it did sail, we would run out of reasons to experiment in our varied workshops.
I take note of splitpins comment. Over time I think he has given enough away to reveal that he may be a sailmaker. Come on split, fess up a bit. We might all learn something from you. Apart from cutting remarks are you also good at cutting sail cloth?
Pity about them Chinamen bein' replaced by Seth Efricens. You can always get a good cheap feed from a Chinaman, even if it is "slow cat". Given their Dutch heritage, you're lucky to get a fart from them other beggers.
Adios Amigos and a Happy New Years from mes toos. Cisco
Cisco, if you must know here is the formula for testing most things in a critical way.
It will apply to most situations and devices.
The second formula is one you might need in life!
The more New Years drinks you have the clearer it becomes.
Just let me know how you go with it...easy as
The only water yacht that comes near is "Hydroptere". Type that or "the fastest yacht on the planet" into the search bar on YouTube and see something spectacular. Like a gnats whisker under 50 knots., I think yours is very good and sets up a starting point with the construction of a yacht that will give a good platform upon which to build fine tuning.. Given their Dutch heritage, you're lucky to get a fart from them other beggers.
Given the length of your posts, Gizmo and Cisco. I will assume the following
NO wind
TOO much wind
TOO hot
Tides all wrong
Stuck on minor tech hitch
NO money
TOO busy working
In-laws visiting
Inlaws moving in
All of the above and more except for the outlaws, but in particular too hot. In fact hot enough to motivate me to finally hang the inside cooling head, run the pipes to the compressor unit, bleed the air, hook up the wiring and run the a/c unit that I have owned for the last 4 years.
Did all that before hooking up with Bernard and Judy (daisygirl on Seabreeze), from the Brisbane Blokart Club at Burnett Heads around 2.30pm who have been holidaying up here and rang me to find where a good sail could be had.
The locale I suggested we should meet at consists of a concrete path, slightly windey, that is about 3-400mm wider than the track of a blokart, about 4-500m long and is well exposed to a norhterly of which there was one blowing at 10-15 knots. Some fun to be had here!!!
They had been having a fat old time by the time we arrived. Had a chat with them while I assembled the blowie and got onto the track.
The eastern end of the track requires that speed is washed off in order to negotiate the 90 degree turn before passing between two posts preventing cars entering the park, or, conversely blokart riders that have'nt got their act together, entering the car park.
Upon entering the carpark there is fun to be had as well, usually to the amazement of on lookers and panic of 4wd owners that never go off road, thinking that you will crash into their shiny new $70,000 piece of egotistical bull dust.
As readers will no doubt realise the main purpose of the carpark is for practice of land sailing in tight areas and for lining up before re-entering the track through the "GATE". Don't forget we are hooting here.
So, on the track, good run, west to east, wash off, 90 degrees, through the gate, into carpark, wave to spectator, avoid old couple with old dog, line up and go back through gate, too fast, turn 90 deg, outside wheel falls off path and rim clips concrete, BANG, wheel explodes. Cisco says "Oh no not again." Yeah, last time I had a sail was same location and the same thing hapened but at the other end of the track.
What better way to spend New Year's Day than making new friends and busting your blokart??
Cheers Cisco
Judging by the weight of material I have bought, I believe an LLF Mini would be quite capable of demolishing Nissans and Mitsubishis as well.
As for Hyun Days and Day Woos (you wouldn't own one of those even though they have your name on them would you?) an LLF Mini rider would experience a minor speed bump while cutting one in half n'est pas.
Trouble and strife and the billy lids are heading to to Brisso for a few sleeps (in my beautiful 84 XE Fairmont, worry, worry,worry, while I am left with the Corolla) and my only responsibilies will be to keep Naa'laa the ridge back/boxer cross and myself fed.
Imagine that!!! No wobbly conversations, no back chat and a companion that is pleased to see you no matter what time you come home. Is it like that in Heaven??
Given this opportunity of some peace and quiet, I will create as much noise as the neighbours will stand while an LLF Mini is being constructed..
Adios Amigos, Cisco.
Woohoo, Hills gets out the deck chair and popcorn... This is going to be good! [}:)]
It's not a Faacun. It's a Fairmont.
Because successive Labor governmets in Queensland have put the state so far into the red (worse than the federal debt I hear), and revenue is sorely needed, there is a special rule for cars.
"If it is possible to break the law in it, you can drive it in Queensland." How backward is THAT??? Cisco
One day it will finally die and you can pull the tailshaft off and use it for the main chassis tube on a mini or CL 5!!!!!!!!!!.
Id forgotten that little source of building material. thats what we were using bfore we discovered NQ core tube
always look on the bright side of life, da dum , da dum, da dum de dum de dum
How backward is THAT??? Cisco
Walked into that one didnya both.
