looking at the various builds ,between classes there is obvious large variance in the length /widths .I understand that the mast step position in relation to the centre of effort and lateral resistance needs to be calculated. or experimented with .But what benefit is a longer wheel base. For instance if I extended the length of a mini(forget about conforming to a class,) would that allow vastly larger sails,and how much would the mast step position need to be changed.As an example I looked at two potties side by side the other day one being the extended model it looked to me that the mast step positions were not much different in relation to the front wheel. Is there a recognized ratio between mast step and length as a starting point in a build. Just curious ,been thinking about extending/altering my mini(Windbob)

Hope someone with some maths helps you. Mine has been trial and error to balance the yacht over time.

I have slowly worked the mast forward on different chassis to take the bigger sails and go on the handling when sailing.
My current mini is 120mm narrower than long to meet the 5.6 rule. But I do know Greg's is wider than long, when we sail on the softer surfaces locally.
My mast base is 280mm to the centre from the rear edge of the front tyre and I can use up to 9m2 sails. I move the mast back 120mm again from this, to go down to my 5.7 storm cambered sail for up to 40 knots of wind. (All cambered windsurfer sails with -2 degrees of forward mast rake). I weigh 110kg and my belly button sits over the top of my rear axle when sailing.

Look forward to a more detailed response from other builders/designers.

A table with all variances would be great, but trying to collate would a headache, of which i have too many already

Bring on the 4D plotting software...

....actually, more like 40D

Oh so many variables!

Lucky its fun testing though

This thread may be of interest.....

www.seabreeze.com.au/forums/Land-Yacht-Sailing/General/axle-width

thanks for reply chook,I take it you are running with an adjustable mast base as in other threads. My mini has m base set to chassis with adjustable front from chassis to wheel,so although I can move front wheel in or out .The mast base stays same in relation to rear axle.Could I bother you for the length from mast base to rear axle,for your 5.7 or near enough,I intend trying to use a 6 metre twin cam ,although I have windsurf sails from 4m to9.5 with masts to suite , and standard yacht sails 3m and 4m, I'm trying to compete(just fun racing not classes) with a few who run 5.5 land yacht sail,and find 4m just not powerful enough in the 15knt winds we generally get. Not bothered about going bigger than the 6m. thanks in advance.

Hi yes I'm still running replaceable mast stalks of different angles to suit my needs. You can change them over in about 2 minutes.

My newest yacht is 1120mm from the rear mast base (for my 5.7 sail) to the center of the rear axle.

Since December 2014 I have built 2 more LLM 5.6 minis as they wear out/fatigue at the T junction.
Its metal fatigue that gets them in the end. This is good as it gives me an excuse to alter/build a new design.

Last weekend I replaced the 32x3mm doublers on each side of my current ride, (pic below) extending them right to the outside edge with 32x5mm Flat bar to stop them bending again. Should have done it originally but the hole is for a button stopper clip and there is a jam nut on the front bottom edge pushing up at 45 degrees on the corner of the axle to keep it firmly in place. See the gaps between the clamped on bits before the repair) They cop a flogging and do lots of hours along with my kite buggy as well. (I just completed 10,000kms last weekend for this current year, on "wind powered wheels" for the second year in a row.)
These bends were from a crash on Lake Lefroy at high speed. Danced from wheel to wheel in a double pirouette bending all 3 axles.

This pic is my December 2014 build when new (Cant find my current #26 mini build pics on my new computer) and the only real changes to my new one is to the rear T junction being beefed up even more, with gussets to spread the load at the pipe to square intersection. Length and front ends are all done in my jigs, so the last 3 have now remained the same mast base and chassis dimensions. It has 25mm less than the 5.6mtr rope rule.


Good luck with your mods and hope this helps.
Chook

International Mini 5.6 rules have evolved into two classes now
Sport and Spirit The spirit class is more restrictive to keep the original
low cost concept. One of the rules for this class is the mast step position. The mast must be no closer than 200mm from the back of the front tyre One of my minis falls foul of this rule so it is classed as a Sport
The other has the mast in the same position as Chooks latest one
which is 1120 mm from centre of rear axle to rear of mast and is 280 mm from rear of front tyre so it comes in as a Spirit or Sport
They both comply in all other respects
All of this only applies to those who want to seriously race of course

thanks for info,will be doing a bit of cutting and welding soon,can use blowkart in the meantime.
Always curious regarding class rules,what advantage ,if any,is there, with the mast being closer to the front wheel on one chassis and not on a competitors when racing within the classes.
,The organizers must think,or know there is to set these rules. Can understand the overall size rules ,and sail and mast types.but why restrict the forwards limit of base bearing in mind you could move it backwards as far as you want, or is there a rear limit as well. All good fun , I remember when I used to be involved in windsurf racing ,where our club had a 7.5m upper sail limit ,I was 14 stone and most of the rest of the club were about 11 to 12stone ,guess who used to be last,in lightish airs,different when it was windy

This mast position thing is a bit of a mystery to me also
As I don't very often sail with other yachts it is very hard to judge if any changes are improvements or not
After seeing the mast positions right forward on race winners in Europe I thought I would try that too and it SEEMED
to be an improvement but only when I went to a full sized wheel on the front (sailing on beaches)
The fact that the rule makers have introduced a restriction on mast position in the new Spirit class seems to suggest that there is some advantage in moving the mast forward

I built a "Hiko" mast over the steering head (Thanks for your input into the design) but I found it had too much weight over the front wheel on our softer surfaces. Worked really well on rock hard salt at Lake Lefroy. The steering was absolutely "point and shoot" direct, which was fantastic, but suffered from front wheel drag from the increased down pressure when the yacht was fully fired up.

I study my wheel tracks to see what the balance of the yacht is like. One slight rooster tail on the rear and 2 other tyre marks is what I aim for on a broad reach. This is on the softer gypsum surfaced lake we use.

Like you Chook I found the front wheel dragged with the mast right forward but by laying the mast right back in my oval mast step and fitting a fallshaw 400 x8
wheel to the front I really like the way it sails now on the beach

I have repositioned my second mini ,s. mast from standard to the same as your
1120 mm from back axle measurement and hope to try that out in the not too distant future I am thinking that it might be a little more versatile with the smaller size sails than mini number one Not that I use much less than 5.5 myself as I am not a lightweight but might be better for others to sail.

very interesting,Just had a though It would be relatively easy to make an adjustable base for a blowkart. The top is held permanently but the bottom of the tube could be rigged so that it slid forwards and back(Could be made to work on the fly) there's 3 inches of space to the front and unrestricted to the rear. It would have the effect of moving the centre of effort back and down with it right forwards and the reverse right back.It would give weather helm right forwards increasing the upwind pointing,And lee helm right back for downwind.
We were constantly sliding the mast back and forwards when windsurf racing with longboards and they had a simple foot pedal to facilitate this. . another thing to keep me awake at night
.Is there any restriction,just out of curiosity ,regarding the blowkart rules,regarding this,can't be the first to think of it. Probably a totally stupid idea,not the first one in my 72 years.

would need to rig up uj on steering arm since the angle would alter through the base,or alter to foot steering so may be a stupid idea,still thinking about it

I don't consider foot steering a stupid idea

Bryan "fastest blokart on earth" pilot, has foot steering on one of his karts and it works well in my opinion, as you have both hands to sheet with.

It was originally built for an Esperance, West Australian pilot called Shane, that only had one arm.

I also have a hand steering setup for a LLMini. I made it up for a mate that had a leg in plaster while he was here on holidays and he stuck to the really smooth areas to sail on. It got him out of the house!!!

Here is my two minis the one in the rear has had the mast moved right forward
With the mast raked right back and a windsurf 6m sail coupled with a full 400x8 wheel it is great on the beach
The one in the front has mast moved forward to 1120 mm from back axle and has yet to be sailed
Both have Ski rear axles which I have found great

Great photo Hiko!!!!

So my chassis is 120mm longer than yours, due to my twin mast mountings.
I'm 280mm from the rear of the tyre to the centre of the front mast mount and then another 120mm back to the centre of the rear mounting for the smaller sails. Then 1120 to centre of rear axle.

Hi Chook and all
It gets a bit confusing due to the different mast steps
My mast step is a squashed 75 mm tube so it is 90mm front to back
From the rear of the front tyre to the centre of the mast step is 275mm and from there to the centre of the rear axle is 1160mm making a total
of 1435mm Yours seems to be 280+ 120+1120 = 1520 making it 85mm longer I think.
The rear one in the photo comes out at 1460 mm
I hope to try it out in the not too distant future. I want to get both ready for the school holidays so the grandies can have some fun.
I dont have to worry about the foot pedal positions any more as they are all taller than me now.. even the girls and I am not short!

like the look of your blue seated mini hiko also looks to put your weight right over the rear axle. Would think that takes the weight off the front wheel which has to prevent a bit of drag .....increase speed.
I'm logging all these measurements and keep looking at my sand bob,which I got mainly for my grandchildren ,with me using the blokart.
I can see the grinder,cutting discs,new tubing and welder coming out soon

Thought I would throw in my 2 cents worth. If you look in my profile pics there is the boat/yacht in there that I cut the parts, put it in the jig, my welder buddy glue it together. If you look at my mast step which is rather tall, it's fully adjustable from 0 deg to 10 deg. I found by setting it at 0 deg. I tend to fly a wheel more and at 10 deg. I get steering slide in a turn. It is set at 7 deg. roughly has been that way since. I think the adjustable mast set is a good idea but a waste of time when you come right down to it. 7 deg. out of the box works for me. That's my 2 cents.

Windnut

Yeh, horses for courses "Windcrazy" your dead right.
What ever works for the sail/mast combo that's being used.

Ours mast bases are very upright or even negative rake due to the enormous down haul used on uncut windsurfer sails. The mast bend is well over 1000mm when sheeted in.

Traditional landyacht sails will tend to lift the centre of effort and move the draft back as you sheet out. Unlike current windsurfing sails that use the high downhaul pressure to control sail twist off instead.

Most pilots that comment about the newer designs of windsurfing rigs have never used them in a land yacht and are very quick to point out why they wont work.
This is really unfortunate, as they can be picked up so cheaply and easily out perform traditional sails, both up and and down wind.

Wind is only 18knots from the South East here, so it's off to Pink Lake for some 8m2 sailing.

yes ,indeed chook. Being a life long windsurfer, now mainly kite surfing. And having several windsurf rigs to play with,a friend and myself have been playing with uncut rigs on our land yachts,He uses a windsurf boom, I use a single pole boom under the rig.By swapping about between W/S rigs and conventional......
What we have found is ..... So long as there is enough wind to just start to power the W/S rig,as soon as you get going the apparent wind kicks in and we leave the conventional sails behind
.
In light winds conventional sails go earlier

in moderate winds if sail sizes match each other conventional sails go earlier, just, ,we believe due to them being fuller when sheeted out,the downhauled W/S rig is by design flatter in the foil.

in gusty conditions,its a no brainer W/S rigs outhandle conventional.No flogging on the sail,and simply sheet out to gain full control.

W/S rigs point several degrees higher,due again to the flatter foil being held without excessive sheeting in.

If you need to run downwind conventional beats W/S by a long way (But who wants to do that that to often)

We can use W/S rig at least 1 meter bigger in a given wind.

The W/S boomed rig puts too much weight higher up the mast,increasing the swing weight on turning,mainly felt in gybing,you get a sudden whack as the boom swings round,which is on a couple of times has tipped the yacht . So better to use lower under the sail boom.

We played with not downhauling fully and rigging so that the sheet/under boom downhauled the sail as well as sheeting in.With pulleys it does work, to the extent that the sail tensions and looks properly downhauled,but sheet out and everything goes to the dogs,boom lifts ,and rig flogs about uncontrollably.

not tried cammed sails yet although we have several up to 9 meters.Next time may be.


So now looking at some sort of on the fly adjustable downhaul system,cleats and pully probably.

We are doing this since we both have several W/S rigs,and are too tight to buy other conventional sails but I do think its the way forwards. Still on learning curve.... Fair winds to all,

Interesting your analysis of the difference between uncut rigs and conventional sails.I have found that my uncut rigs outsailed my cut sails but against the best Frog sails the have a smaller sweet spot and I still cannot point as high. You mention about adjustable down haul, I haven't gone down that route as I can only see it adjusting from being in tune to being defined, what I have found useful is adjustable outhaul, to get going, turning down wind and even up wind finding the best shape for the sail. Here are some pics of my rig. Question? When you are using your straight boom have you extended the corner of the sail or are you just taking it to the original outhaul, using a straight boom are you able to pull the battens off the mast and get as good a set as with a wishbone?

Thanks for that input guys. It's fantastic to see the experimenting that's happening elsewhere.

I only wish I windsurfed when younger, but farmed 76kms from the coast. My first love now is kite buggying and I have a quiver of Ozone "R1" race kites, which I LOVE to bits and travel to Queensland and South Australia every year to catch up with the gang buggying.

Yes the adjustable "on the fly downhaul" solves the issues of not being able to belly out the sail with a windsurfer rig and completely eliminates the need for adjustable outhaul.
Here is my setup although its not a good photo.

Greg's is a better shot of the setup. The sails original downhaul point is connected to the boom and then our adjustable downhaul system through 6 to one, 30mm triple blocks, the bottom one with a becket and cam-cleat. The loose end of the rope goes through a bit of 25mm dowel 125mm long as a "T handle" fitted with a race cleat (so it's easy to adjust rather than pulling on a 5mm cord). The excess cord from the initial downhaul setting is just tucked back under the seat cushion when sailing. This keeps the handle close at hand for any adjustments.
When rigging up, the outhaul is always pulled out really tight.
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Bynorthsea said.. Question? When you are using your straight boom have you extended the corner of the sail or are you just taking it to the original outhaul, using a straight boom are you able to pull the battens off the mast and get as good a set as with a wishbone?
------------------------------------------------
Yes we started off just tying them to the end of our "lower" boom, but found the extra length/distance from the clew to boom on some sails, allowed for some freeplay or room for movement, so have added corners/triangular sections, to get some of our sails eyelets closer to the boom if required.

Here is a photo of my yacht fully sheeted and down hauled with a 7.2 m2 sail (7mtr + rear "white cloth" clew addition of 0.2m2). Please ignore the 4 1/4" wide x 26" Fatbike tyres, as we only use them on our softer lake for fun sailing.
I have tried to line up the rear axle in the pic. The dynamic centre of effort is slightly behind the rear axle to lighten the front wheel at speed and as the sheet is eased it moves forward about 200mm as the carbon mast unloads and puts more authority into the front end. The 4800mm mast is curved back 1720mm at its tip (with a straight edge up the front of the base of the mast) when fully sheeted.
It has 2 degrees of negative rake/forward on the mast step/stalk.

Under the seat on the ground is the doweling "T handle", for on the run downhaul adjustment, to trim the sail for whatever is required for that leg or conditions.

Cheers Chook

By the N sea ...Modern W'S sails are set only with Downhaul,for the given conditions,early race sails,eg Neil Pryde were set with negative outhaul.You were advised to controlled the power with adjustable downhaul .You can use outhaul but that distorts the foil shape , so better downhaul within the stated instructions on the sail and use the boom to just hold on to.
Chook that's an interesting adaption for fixing the lower boom,will have to have a look at that.And I like the idea of using the front of the boom fixed to the tack for downhauling again another look at that.
.Is the 7m a reasonable balance, my wheel base is about the same at yours,whats your wind range with the 7m.
I've got a 6.2, 6.9,7.4 and,7.7m,with several below and a couple above that size. the 6.9 m might be a good one to try.

Negative outhaul, now there is something I haven't even heard of.
That's interesting. I've sailed without a boom, just to see what would happen using a 4 cambered sail. It worked well, but sheet pressure wasn't up to scratch due to the blocks tangling.

We just feed the front strap that's fitted to the sails over the fork on the front of the boom and it positions everything perfectly. By adjusting this strap you can remove every wrinkle in the bottom panel with all downhaul pressures. (it sorts out the diagonal tensions in the front of the sail below the bottom batten). Once it's set, it is forgotten about.
The fork is made from 10mm round bar and covered with clear plastic pipe to protect the mast when downhauling. The mast, boom and sail rotate as one due to a bit of mast curve.

The 7.2 and 8.2 sail balance perfectly, as the larger 8.2 sail has a very similar boom length. The mast is made longer with a tip extension of another 215mm to cater for the longer luff. This is done by inserting a 215mm bit of dowel into the aluminum tip extension that is slipped over the mast tip to increase the length and retained on the mast by a few wraps of electrical tape to make de-rigging easier. The wooden dowel pushes down onto the original mast tip. By using different combinations of dowel lengths (I have 6 bits of dowel from 25mm to 200mm) the sail can be set up at the height required and when I'm happy, then I make a one piece bit and it stays with the sail in it's bag. Saves trying to think what's required after a lay off period. Its all written on the foot of the sail and mast bag in felt marker. Sail, mast, tip extension, mast rake required and mast position on the chassis. It's all in front of me, so it's a no brainer for my old head to remember when getting it sorted to rig.

We sail in pretty gusty conditions as our local lake "Pink Lake" is inland. Depending on the wind direction, from 3.5 to 6.5kms from the coast with the wind tumbling in over 52mtr high limestone ridges. By the time it gets to the lake the wind has smoothed out somewhat. A Northerly is perfect for sailing and really smooth too. We do this early in the day to avoid the heat of Summer.

I use the big sails 9.0m2 in very light winds, "a crabs fart" to around 6 to 8 knots is pleasant, but very rarely now days, as we pick our days to sail more. We are out sailing 2 to 3 times a week subject to the lakes dampness. My 9.0m2 is a Severne, 2 cam sail and to be completely honest, is too long in the boom for perfect balance. The front of my mini does lack steering when the wind gets above 6 knots. I just have to slide forward under my seat belt in the turns. MUCH better than sitting around waiting for wind though.

8.2m2 up to around 20 to knots, and drop to 7.2 up to around 25.
My storm sail is now 5.7m2. Had that up to a measured 37 knots so far and topped out at 92.4kmh on Lake Lefroy. It was my first time out with it. I have fine tuned it more since then, as it was set too high up on the mast and I had miss measured a batten length and when it seated properly into the camber it was too short.

My quiver is 2 x Neil Pryde Evo2 and an Evo3. These are old school 2010-2011 windsurfer sails that I picked up for an absolute song. On closer inspection all 3 sails had a cracked camber and 2 battens had ends cracked on them and required repairing. A very simple, but time consuming fix due to being fiddly. I love this kind of therapy though.
When they cost next to nothing, I can afford to play around with them. I can only imagine how good the current crop of windsurfing race sails must be nowadays.

What great info. Still not clear when you are using the adjustable downhaul, are you easing it to flatten the sail more going up wind or tightening it to bag it out more?

Select to expand quote

Bynorthsea said..
What great info. Still not clear when you are using the adjustable downhaul, are you easing it to flatten the sail more going up wind or tightening it to bag it out more?

Back off the downhaul tension to "Bag it out" to build up speed and as it increases ease it up tighter to flatten the sail. If the wind is fairly steady/consistent, not many adjustments are needed. The sheet rope will alter the shape enough as it's sheeted hard.
Tightening up the downhaul flattens the sail more. Ease it out and the aerofoil plumps right out. We are only talking about 75mm of downhaul rope adjustment through the cam cleat, to make use of the full range of the sail. From "tight as" to max thickness/draft of the foil is altered with this small amount of movement. All the time this is happening the completes sail is drum tight without a single wrinkle.
Almost all of the reshaping happens in the front 1/4 to 1/3 of the sail and is completely independent to the sheeting.

Next time I have my GoPro camera with me I'll take a video of this downhaul/draft adjustment without any sheet rope or out-haul connections on the sail. The sail will remain drum tight throughout the range.

Thanks for that, it almost seems counterintuitive to what I thought I have been experimenting to get the best out of my sails understanding that I needed approx two thirds floppy leach, more and the sail depowers, less and the power is too high because the top does not twist off. Looks like I will have to mod my down haul and have a go. Look forward to the video.

hi By the N sea. I take it you are not a windsurfer, so perhaps I can explain a little ,may clarify your query.If you have a look at U tube there are many clips on how to rig and tune a W/S rig. But only the downhauling is of much relevance to land yachting .With W/S remember that we are holding all of the force through the rig and locked against the board via foot straps and hooked onto the rig via a harness,Its impossible to hang on is strong planning conditions without. So rigging is essential. its the upper third of the sail that we watch, In high winds the upper third needs to be loose, sometimes down to the boom in very stong winds.I
In Light winds it need to be relatively tight all the way up.
This is achieved via the downhaul,crank it down to loosen and let it off to tighten. The aim to get the top of the sail to twist off in gusts and act like an automatic depower.
If you rig your W/Sail with boom, get someone to stand on the base with the boom laid on the ground and then push down on the tip of the mast and outer tip of the sail, to simulate wind driving the sail, If you have plenty of down haul on you will see the loose leech at the top tighten up and twist off.the more downhaul the more the tip will need to be pushed down towards the ground to see this.This may give you an insight into the basic principal. play about with the downhaul and repeat above you will see what I mean.You will see the leech of the sail tighten up all the way down to the boom.

Watch the battons and the aim is to downhaul.initially to get the upper batton ends in the sleeve to pull away from the mast,and point at its centre,with the lower two of three batton ends laid on the downwind side of the mast,they just slip past the mast when gybing or tacking.
The boom outhaul is used with slight outhaul,and left there ,without it or with negative outhaul,the sails centre of effort flows back and the sail becomes ,heavy on the hands,refered to as being too backhanded.Because in a land yacht you are not directly holding the sail the outhaul becomes a bit redundant,still can be used but has little effect on the yachts performance ,more for holding the sheet rope.
I'm assuming you have non camber induced race sail,but the principal is similar ,the only difference is that you need to sometimes force the inducers onto the mast sometimes before ,sometimes after downhauling and some times need to excessively outhaul to do the same but then let the outhaul off before final tuning with downhaul

Take our word for it ,get rid of the wishbone boom and make up a straight one fixed under the sail from the base to the clew. It. matter not that it crosses the lower bit of the sail, W/S boom can still be used of course my friend still does, but I find that it adds too much swing weight high up the rig,not what you really want.
.On one of my small wave sails it just brushes the bottom of the sail,on the bigger ones it just lays about three inches on it .Don't even notice it. Hope this helps and please don't take offence if you already know this ,no intention to do so.
Fair winds about 5 Bf would do.
cheers ken/