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Hi fellow sailors. i have built a class 5 YOTT and have been using a used land yacht sail i was lucky enough to find on the internet that I was told is a 5 meter sail. The sail is not labeled anywhere like a windsurf sail with the square meter size or luff size so im taking the sellers word that it is a 5 meter. i have compared it to some BLO KART 4 meter sails and it is slightly larger and seems about right to be a 5 meter. So here is my question, We have had several very light wind days sailing here and with the wieght of my YOTT and my wieght i need a larger sail for days like this. I know class 5 rules restict the sail size to 5.5 m2 for racing but this is for recreation sailing on light wind days. HOW BIG A SAIL DO MANY OF YOU USE ON YOUR CLASS 5 YACHTS? i WAS THINKING OF MAKING A SAIL AROUND 7.0 -7.5 METERS. Do any of you use sails that big
If you cant get going with that sail in 3 to 5 knts on that concrete surface there is something seriously wrong somewhere.
My first thought is the mast looks like a standard windsurfer mast. Way too soft for a landyacht. Also once you fix that you will also need a stronger boom.
That sail is a New Zealand made Fed5 sail by Highwind sails . Nothing wrong with that. There is a plan to build an aluminium Class5 mast in my photos on here. They are bloody heavy but they work. A fibreglass equivalent would need to be at least 8mm wall thickness, for half its length, a carbon one maybe 6mm.
Next you could look at the batten shape. Also a photo on here of Fed5 battens compressed to show there shape.
These battens are from a Fed 5 sail exactly like yours. The figures along the bottom are in pounds.
Get some kitchen scales and compress each batten down on to the scales and you will find you get to a point where the poundage dose not increase anymore.
You also want the widest point of the bend to be approximately 25% back from the leading edge. That's the mark you can see along the top of the bend on each batten line. These ones are not perfect but it does not matter too much. Give it a try before you spend money on a bigger sail.
John HS
Yes that sounds like what you would need. So what does the wall thickness end up at the base?
I would love to have a carbon mast if the Class5 rules were to change. My ally mast weighs over 10kg and is 10mm thick at the base with all the internal stiffeners. About time for a rule change if you ask me.
Couldn't tell you the wall thickness.
Overall weight is a 3-4kg including reinforcement.
Internal reinforcing consists of inserting the top section of a second carbon mast into the base of the main mast and gluing it in place with urethane.
External reinforcing is 2 wraps of 50mm glass tape overlapped 50% I.e. 4 layers of glass up to 2x the height of the mast step.
Re the sail size , perhaps you could tell us more about the wieght your sailing with the we can work from thier.
other things to consider are what you are doing to get going. on a man made surface you often get frustrated trying to get going because you are trying to follow a road opr runway. BUT you need to sail relative to the wind . Runways are usually placed in relation to prevailing winds!!!!!!! to get a head /tail situation.
re windsurfer masts. . for a class 5 you will need to start with a 5.6m IMCS 35 or 36 thats a big stiff mast,
then you need to add carbon or glass to the lower meter/half meter. we also addd an internal stiffener. as john said another mast top is perfect. fix that in with a tiny bit of epoxy or uerathane. john usedway too much which bumped the weight way up. the mast you start with will be about 2-2.5kg
I think maybe I wasnt clear but im not having a problem getting going on days that the wind is blowing above 10mph or more, the 5.0meter sail seems adequate. but i want a sail for very light days, which we have alot of lately (5 - 10mph). for my other land yacht and ice boat I have a quiver of several different size unmodifyed windsurf sails to use depeneding on the wind conditions, but for my class 5 it uses a specialized sail and i only have one the 5 meter. i was just wonering what size some of you have as your biggest sail for these kind of days. I plan to loft a sail from scratch and was planning to make one around a 7.0 meter. even the blo- karts have had a tough time getting moving lately and they almost never are slowed down. I just was curious if 7.0 meter thats sounds extreme. im currently using a 5.5m carbon/epoxy mast with a 28 IMCS. and a aluminum stiffiner at the base and a boom made from a carbon mast with a top section stuck inside as a stiffiner. I agree with Land yacht and Clemco I should start with a stiffer aluminum mast. Clem i have seem your YOTT posted with many different sails over time one which seems to be a light air sail and not as high and skinny as others
That US15 sail was actually better for stronger winds above 20knts. The new Frog sail I have is great up to 20knts but above 15knts I use a shorter softer stiffener in the mast so the mast will bend more and give me a flatter sail.
Stiff mast for light winds, soft mast for strong winds, means you can get more wind range from the same sail.
Opposite goes for battens. stiff battens for strong wind, soft battens for light.
This is just a mock up on the Mini Mini but 9m2 is what I use on my 5.6 mini in light winds to 3 or 5 Knots.
Above that wind strength, I go down to 8.5, but my favourite go to sail is 6.7 up to 25 knots. That's what I sailed at the Lake Walyungup State titles.
I weight 108kgs, 238 pounds.
Now there is a light wind sail!!! 
I wondered when you were going to chime in chook!
Thanks Chook Thats the kind of info i was hoping for. im about the same weight as you and my YOTT is on the heavy side. so a sail larger than 5.5 meter is not unheard of. I will post my sail on sail making when finished. im just waiting for sail cloth to be delivered. Land Yacht and others have some great info on there sail building and its spot on compared to the sail I own now when i checked against it.
Landyacht is a "master" in the sail design area (well all things land sailing really) and has helped me out no end.
Cheers Paul.
I have been using cammed sails since I first got into land sailing mini's. (as I knew no different at the time)
My first sail was a cammed 5.7m2 recut at the luff.
When I first got to Lake Lefroy in 2011, Paul jumped into my yacht and was astounded that a cammed sail actually would work that well.
I have 5 cammed sails now. From 4.5m2 up. All have 3 or 4 camms and 6 to 8 battens.
Greg has been really pushing me hard locally, to improve the performance of my cammed sails and we have been having a ball.
The windsurfer market is HUGE compared to ours and if the competition is beating you in a ocean race then your sail needs to be faster.
Its big racing and promoting their sail sales. Lots of dollars involved.
Also a graphic change for each model sail is needed, so your not seen to be flying last weeks design.
Our thought process is that windsurfers carry a LOT of sail area at VERY high speed, (up to 7m2 in 25knots and achieving speeds of 40 knots plus, in these winds) so why reinvent the wheel. Lets just go with modern sail design and do the same on land.
This is proving to be the case. The cammed sails point very high up wind and down wind they really fly.
Cross wind the sail twists off above the 3 batten so they are very user friendly. 2 wheels are the norm on a broad reach. (lot less drag than 3)
The mast is the tricky bit, getting it to match the sail both in it's IMCS and still be stiff enough for base mounting. (still sorting this out)
On my latest mini (I won the state titles with at Lake Wallyungup with 6.7m2 of sail) my mast was supported internally at the base and the step was mounted at negative 3 degrees. That's right, forward 3 degrees from upright. This gets the luff curve set correctly and the centre of effort exactly where it needs to be to balance the yacht when fully sheeted in. The steering was "point and shoot" it tracked like it was on rails.
Back to the shed now, I have lots to improve on.
Hope this helps.
Cheers Paul. )
Did the 30 kg weight test again just to be sure. This time put the support at where mast comes out at the mast step. The length is now 4800.
The offset was only 80mm with the 30 kg weight at mid span. (measured it wrong last time) That gives me a IMCS stiffness of 65.
As I said I would love to have a carbon mast but it would have to be at least 5 to 6mm wall thickness and would probably weigh 5kg.
Still heaps better than my 10+Kg mast.
Just did the same deflection test with the "soft" stiffener I use in my mast. The net deflection was 90mm.
Not much different from the stiff mast but I can tell you it makes a lot of difference to the depth of camber I get. i.e. flatter sail.
I'd love a cammed 5 sail though.
I'll have a measure to compare.
Google is your friend..... www.google.com.au/search?sourceid=navclient&aq=hts&oq=&ie=UTF-8&rlz=1T4SKPB_enAU381AU381&q=how+to+calculate+your+IMCS
