Those links are great now can someone put it into perspective as relates to a tricycle undercariage of a land yacht and we would be a little wiser as to what is going on when things go pear shaped perhaps
This is the thing i find the most interesting in the sport of landsailing. It's far from an exact science.
With race cars over time things are perfected and refined, as with land sailing things are also getting more advanced, but its a case of trial and error and with every error is a little more to learn.
The internet and forums are a wonderful place to exchange ideas, learn, and try your own thoughts (how people did it years ago is beyond me).
In other words i have no exact answer to why it works or doesn't on landyachts.
but im eager to learn 
Yes me too
Last weekend I crippled the bead on a 26x2.5 downhill tyre about 30
minutes after I got to the beach and I have spent most of today making slicks out of another pair and I have no idea why it happened so it could well happen again
The tube had a puncture but I dont know which happened first or why
There is a lot to learn as you say
Have you tried "thorn proof "tubes?
In South Australia we have a weed called a "3 corner jack" some people call them a "bindi eye" and they are bad news on bike tyres.
On the yacht "Richshaw" with 20 inch bike wheels i replaced the normal tubes to thorn proof it stoped the punctures but it slowed the yachts acceleration a huge amount.
The added weight in the tyre/tube made a very big difference, i noticed a similar effect between 8 ply, 4 ply and 2 ply tyres on wheel barrow wheels on class 5 yachts.
I do some casual work for a tyre importer and have noticed that many of the high performance / race tyres are VERY light compared to standard road tyres of the same size. Maybe for the very same reason ..Acceleration !!!!
Rotating mass is doubly as important as static mass for the reasons below:
1) Firstly you have to expend energy to get it spinning.
2) Secondly you have to accelerate it up to the speed of the landyacht (just like every other bit hanging off the frame).
So you effectively have to accelerate it twice. We found this out when building a Formula SAE car.
Taking 500 grams off the weight of a tyre is about equal to taking a kilo off the frame 
Taking 500 grams off both rear tyres is about equal to taking two kilos off the frame 
I thought is might be something like that,
BUT i did find the heavier tyres/tubes worked better in good or gusty winds and a big course. (perhaps they were working like "fly wheels")
The lighter tyres/tubes worked better with a small course and or light winds.
Vic had his weight way back, we measured 2-300mm. that would put his CR further back , hence the too light front end. with a large weight added to the front to counteractit would theoretically sort the problem BUT the added weight made the steering too slow to react. . when vic slid out he slid back in the seat( you can see him way back in the photo)which made it worse.
on this surface your reactions need to be instantaneous,and exactly right. iePractice.
Often when i go out for a sail,when every body else is just sailing I will set up a mark and just practice going around and around, always pushing the yacht o see what will happen. with rebalancing and tuning and practice Vic and his new yachtwill be a force to be reckoned with[}:)]
I didnt christen it " The Beast of Bemingham " for nothing
Don't get the cr (centre of resistance) mixed up with a factor that hasn't been discussed which is cg (center of gravity).
The cr of a land yacht will never be behind the back wheels but on the other hand if cg is behind the back wheels the front will come up like a seesaw.
Mind you please keep in mind these variables as well...
CF Centre of Focus this may swap between the wife and the esky filled with ice cold beer.
CPr Centre of Pride again this may change from the kids on board to the boat itself.
CA Centre of Attention this will often change between the wife, kids, boat, and the beer.
CPa Centre of Passion this will vary between water and landsailing (and the wife)
CR Centre of Resistance this can often refer to what stops the yacht going side ways or the wife stopping you spending more money on sailing stuff.
CE Centre of Effort this the amount of effort to go sailing, get the beer or the wife and often associated with CPa
yes vics beast is surely a hot yott in the making IMHO
Good info on the tyres Gizmo
I just had a thought [sometimes it happens]if a yacht is moving forward at say 60kms/hr the axles will be doing the same but the top of the tyre will be doing double that and the bottom will be stationary or it will be skidding on the ground
therefore each part of the tyre is travelling at different speeds Whaa???
I am getting a headache time for a cup of tea and a liedown I think
Thanks for the import guys,I am back at work in Kambalda at the moment so I have not been able to do much work on the yacht (800km away)but will be home again in two weeks and I will sail it again with the changes made and will post the effects. I may be that it is not suited to the surface at Safety Bay and I may have to revert to a yacht with smaller wheels for that surface but I dont want to give up yet as I see it as part of the experience
Cheers
AUS230
Note:
I did not bring the yacht to Kambalda for testing on Lefroy as the lake is currently flooded.
The changes to AUS230 where positive (changing the wheels back to 12% and moving the steering foward 10") the results where that it is now a competive yacht and at no time did it feel that it was going to flip for no reasion. Still some work to do.
Shorten the seat by 12" as I am now sliding back and having trouble keeping contact with the stearing.
Look at modifing the stearing syetem(currently using cables,thinking of changing to a rod.)
Raising the pully block position in the seat as it is bashing the hell out of my legs.
Modify my next set of wheels ,as a couple of wheels have split when I have put 50psi in them(plus expanding in the heat) no problems when inflated to 38psi.)I think I will have to live with spinerfex punchers,only one this time.
Cheers
AUS230
the changes that were made to aus230 where all possitave with the yacht preforming very well. Widing the front steering attachment points to 5"each side of the center point improved the steering (stayed with cables)
Shorting the seat allowed me to have a firmer control over the steering.
All in all I am very happy with the progress so far. Still some small things to change to improve the preformance as with all yachts(got to fiddle)
Cheers
AUS230
I just noticed that under the FISLY rules a class 5 no longer has to have an aliminum mast it can be constructed out of any metal. Promos still require that it is constructed out of aliminum. Question ? what type of metal would they be refering to(just out of interest, I like my aly mast)
Cheers
AUS230
MAST
M1. The mast must be made of round section metal tube, the outer diameter of which must not exceed 60 MM. At rest, the mast must be straight.
M2. The mast may be made from a maximum of four different diameter tubes, each tube must have a constant outer diameter and wall thickness over its full length. At each change of diameter, 3 CM are free to allow for chamfering or for protection of the mast pocket.
M3. The mast must be rigidly supported by an arrangement of metal tubes, all not higher than 1.20 M above ground level.
M4. The position of the mast must not be modifiable with the yacht in motion.
M5. The length of the mast shall be such that the distance from the top of the mast to its foot plus the distance from the mast foot to the ground shall not exceed 5.50 M.
Titanium alloy of course, its only money!!!!!!!!
I believe in Argentina they were allowed to run up to 1m of steel as part of the mast.( basal stiffener)?. Crazy trav has made some coretube masts in the past. they were heavy, but very good. LPI has a steel mast and its brilliant!. I reckon a BQ core tube base and ally from 1/3 up would be a good mat , and not be too heavy.
ALSA class 5 specs
C. MAST
1.MATERIALS, The mast shall be made of one piece of round section tube (or a maximum of 4 different tubes, each having constant outer diameter and wall thickness), with the outer diameter not exceeding 60 mm.
The mast may have any kind of fixed internal stiffeners.
2. LENGTH, The total length of the mast, plus the distance from the mast foot to the ground, shall not exceed 5.15 metres.
3. When not in use the mast must be straight.
EDIT in the pacrim 2006 and FISLY 2007 they say "metal " tube not ally, the ALSA specs say"round section " tube............ no mention of metal.
I shall dig out the hardcopy and check this,
I believe you could use steel inside he mast as long as it was only as a stiffener!!!!!
When I contacted D.R he assured that ALSA followed the current FISLY specs.
Which States
Any metal for class5 mast
Aly for promo mast.
Not sure what the advantage would be or why the change. maybe that good aly is hard to find, Just making folks aware that there are other options , why have they not used carbon masts. they can be picked up cheaper then some aly masts ?
just intrested.
Cheers
AUS230
Do you think those three windsurfer masts I got at the dump for $6.66 each will be good enough if I fill them with a mix of coal dust and epoxy resin?
just dont breath the stuff, keep it away from your canary,and well ventilated , boyo!
Class 5 FISLY rules NEVER said alloy tube! I know cos I was one of the 4 person committee who wrote them.
Reason was that at the time we were trying to be inclusive of any yacht which was out there, and a number had masts which included steel sections. The reason for the 4 outer diameters was that John Glen had recently had great success with a yacht built for Mark White and couple of others (me included) which had 17 outer diameters. The tip was about the size of your little finger. To have replicated these, for the average guy was very expensive. The rule relating to 30mm tapering etc is to give an "engineeringly sound" change, ie eliminate, within reason the stress riser.
Most of the rules, are/were actually to keep a lid on the cost. Also the rules were formulated to have as little interpretation as possible, ie it was clear what was meant. They must be OK as they have changed very little in over 20 years!
Quite often what is decided at meetings are not actually what ends up on paper
Where is "The rule relating to 30mm tapering"?..
Here is what is said on the FISLY site for promo 5 specs.http://www.fisly.org/index.php?id=2
It clearly says "Aluminium"
The original or International Class5 specs don't mention aluminium but does say maxium of 4 sections, with a constant diameter.....
had the same dilemna when the promo rules were introduced.
We were asked to comment on each of the propsed rules, and most of the material specs were not available in Australia. none of the question we had were answered , then the rules were passed.
when talking later to the Guys from "Airtrack" a french manufacturer, they explained that All the french manufacturers get together once a year and put in an order to the mill for the Aluminium. no one manufacturer was big enough to get a load for themselves. On the whole , the promo idea is great, if 20 years too late, but the specs count out all the other countries that wanted to get involved.
The South american fleet got to exist mainly because FISLY helped them get a big batch of Ally and wheels to South America. The insistence of a full length chassis means it doesnt pull down for transport.
all in all , a good idea , poorly executed
Damn the detailitis of the rules I say. Turn up at a race meet with two yachts. One that conforms to the outdated rules and one that has the latest technical innovations.
After the formal racing have informal racing to have a preview of the direction the sport NEEDS to go.
INNOVATION is the predicted growth industry of the future.
OOOOOOOOOOPS
