Richard98

Legal rig ??? Just been re visiting the 6M rules after looking at some older posts on the subject of rigs. I know that the rule allows only one mast and my carbon un stayed mast is legal. However it appears that a pocket luff mainsail is not prohibited. 5.3.2 states that "double luff mainsails are prohibited" Why are no 6M's being rigged with un stayed masts and pocket luff mains ? Richard

Hi Robin, my two, old, well used Star yachts just straddle the models you have. SY4 and Endeavour 1V. Not sailed either for a very long time. I have re rigged though and stuck with the white string and dowel spars. Looks nicer and works with the original bowsies. Endeavour's sails are a little "mothy" now but still look ok. There are loads of pics of all the boats on the internet. Widget is still a handy IOM and I remember the Cockatoo, which was popular in New Zealand; most of the fleet at Glenfield I remember. Richard

Hi Guzzilazz, there is no need for the complexity of metallurgical analysis here; it is simply a question of mechanics. The pre bend requires backstay to just to bring it straightish and this is the starting point. The forestay tension to get to this point alone is the bonus that pre bend gives and the reason it is so important. More pre bend = more forestay tension for a given luff shape plotted down to less tension for less. We are stuck with a very flexible alloy tube and it is very important to match the pre bend to the sailmakers luff profile and this is not easy. Get it in the wrong place and you will have problems. That is a good reason to ask the sailmaker, or get them to do it, what the mast bend position and amount should be. Like so many settings, there are no empiric values and settings provided by experienced sailors will not necessarily suit all; but are invaluable as starting points. Personally I prefer side shrouds , but have yet to win the World Championship of course. Experimentation is great fun and the best way to understand the value of any adjustments. Richard

Quite right to look at updating rig; as the engine but I have found that the quality sails made by current suppliers rarely "stretch" and the loosening leach is quite likely to be a relaxation of the mast pre bend which is being compensated by extra backstay to maintain the jib luff. I have conducted strain gauge tests on the bendy aluminium masts that we are stuck with and they will relax fairly soon. There is a lot going on at the forestay intersection and it is constantly working. Also tried to find any differences between available masts. All are equally poor on bend analysis, some do seem to have a harder anodising though and this makes bending slightly more interesting. The relaxation at this point does not necessarily manifest as a dimensional change; rather an increase in bendiness. Here I can touch on the effect of rolling a pre bend. Get it right first time with absolute minimum passes or it will degrade the stiffness; actually measurable on the strain gauge. The harder coating does seem to require more working and I found it quite easy to warm up the test pieces with the two roller devices that I have tested. The amount of pre bend and where it is set is one reason for for experimenting. It must match the sail luff to be effective and not introduce creases. The need for pre bend is well covered elsewhere as is the reason for the fractional rig of the One Metre. Anyone who has tried to make sails and has found that the superb camber shapes from our current suppliers just cannot be re produced, will appreciate the correct positioning of the pre bend. We spend most of our setting up time at the water side fiddling with the mast settings to obtain a good sail shape; possibly the single most complicated tuning aspect of the class. Mast pre bend is as much of a "black art" as sail making and seriously overlooked. I note that sail makers offer this service and, just like trying to make your own, it must be worth paying for a mast to match the sails. The One Metre is an expensive boat to race competitively; some may say that this is due to peer pressure to use the absolute best equipment. Sadly fewer seem to take up the comments from the likes of Brad Gibson to "pimp" older designs. Now for the controversial bit: Carbon masts. I have rigged up an unstayed, 3 section carbon mast. A delight to assemble and cheap. No long pieces needed and perfectly adequate uni directional tube is no dearer than alloy tubing and no horrendous delivery cost. No pre bend is necessary, the only technical bit is positioning the telescoped joints in the tubes to achieve the correct bend when the backstay is set. My boat sails really well and the rig is sooo stiff. Maybe I will write more about this later. The main point of this missive was to add to the bending discussion. Richard

Hello again Jorge, Had a look through my Paradox notes and remembered that Brad Gibson updated one fairly recently, with some success. One area was the fin and its location. The leading edge of the fin was moved aft to 627mm from the transom, measured along the hull. The fin rake is taken from a datum point 500mm down the L/E edge of the fin, from the hull. Then from the lower tip of the bow it is 855mm to this point. This would apply to Dave Creeds fin I believe. I do not have a Marblehead any more and I am sure that if you asked BG he would give further advice. Richard

Unfortunately Tiggy Cat is right. The hull material does not allow reliable bonding; even when thorough prep is carried out. However one of the many great things about the DF boats is their price and I have seen new hulls for sale very reasonably after owners have "traded up" to coloured ones. By far the best solution. PS don't even consider silicone; that will ensure that a permanent repair can never be done. Richard

Hello Jorge, I used to build the Paradox under licence to Graham Bantock. If you go the his Sails etc web site - downloadable documents you will find a drawing for Paradox. The drawing is annoyingly split, but still useable. The Centre of gravity of the fin is marked and corresponds to the C/E of the fin. Dave Creeds fin is not the same shape, I know but if you measure the C/E of his fun and use that as a datum on the drawing, the correct hull position will be obtained. Grahams drawings have all the info and measurements you will need, then. I have done this very exercise on a Red Wine IOM with complete success. The two hulls are very similar. Both are still great boats ! Hope that helps, Richard

I was really impressed by the DF95 after looking at the design process it went through and the great value for money. So I bought one and remained impressed. Only niggle was the rudder tube play; practically auxilliary steering ! I had proposed adoption of the class by our club; Loughborough Radio Yacht Club. I took the boat to Charnworth Lake one Sunday morning to allow members to play with it. Now Charnworh is renowned for it's fickle/absent wind and here is the point of this missive. The IOM's simply left the DF95 for dead in the light wind. Embarrassingly so in fact. There was the little chap bobbing about not even reaching the windward mark as it was lapped. Sadly the experience was repeated several months later when another member bought one and brought it along. Thanks Andy. The boat is great and has rigs down to D, for heavens sake. I know it is a delight to sail in windy conditions and I know that top rig size was determined by "postability" but it desperately needs a decent top rig for light conditions. I toyed with doing that because I like "developing" but decided to sell the boat on instead. Richard

Sailing !!! Second outing, after a few tweaks. Sails very pleasantly, perfectly balanced and very responsive. The trim tab works but would need to sail in company with a similar boat to gauge efficacy. Possibly not enough wind to detect any improvement beyond that of a biased imagination. The un-stayed carbon mast makes rigging really quick and the boat much easier to carry, with less to snag. I would not like to carry and launch anything in excess of this weight ( just under 10 Kg all up) though. Can manage to carry to the waters edge in One Metre fashion; one hand on L/E of fin and other hand carrying the stand. Next project ???

I have used both of these, Dave lent me his (some time ago of course) and also Eric's one. Dave's was a Rolls Royce piece of engineering and easy to use. I had to prevent the centre wheel of Eric's from swinging; which was causing un repeatable bends. Both have to be extremely carefully used to avoid rotation whilst bending. Also care to avoid working the soft alloy and making it more bendy. Despite what some may say; this does take a lot of practise and a supply of old masts to do it with. The need for mast pre bend and the requirement for special tools only adds to the complexity of sailing the One Metre class. The pre bent rig must me stored straight to relieve the sail luff, so a box becomes essential. There is no escaping this though and we all have them. To sum up, I still prefer the "round the waist" method. Graham Bantock describes another method on his One Metre rigging plan (RP16D), that also works. Richard

Thanks Mike, for you comments, that have been a great help and your question here. I love the overall impression of the 6M, but wanted a boat that made real use of the size and provide an exciting alternative to my One Metre. I ploughed through the 6M rating formula and ended up with a sail plan comparable to a "Star yacht". The crippler was the draft penalty. I saw no point in building a boat of this size with such a tiny righting moment. Increasing the fin depth seems easy to do; so I did it ! Actually more than doubling the righting moment for what is still a modest draft of 340mm. I also selected a ballast weight of 6Kg to make the whole thing more manageable at the waters edge. Part of the problem with the "classic" shape is the poor ballast ratio and sail area penalties . The boat has a respectable 1.0 sq m of sail on a shroudless carbon mast ( for simplicity) and should do justice to a lovely hull. This sort of explains my thinking and the reason why the excellent 6M class is not for me. One amazing plus though; The boat sits on its own. Can't do that with the One Metre !

Progress: Rigged up and just awaiting the ballast casting. This is a planform type intended to improve the efficiency of the keel in association with the trim tab. Have reduced trim tab area after further calcs.

My lockdown project boat is progressing well, thanks to a fair amount of input from members. Bought as a planked, scaled down, Moby Dick design and being hacked about by me to make a sort of "what if" 6Metre yacht. What could a 6M be if not quite so constrained by sail area, keel depth and hull contorting measurement rules. NOT intended as any criticism of the 6M, which is a lovely class to look at, just an exercise in what could be done. I have removed 0.5Kg of internal structures /deck. The original fin, rudder & skeg and 7Kg internal ballast also lopped off. A new c/f keel and rim tab plus an old One Metre rudder are the new external appendages. The new deck has ended up looking like a Swiss cheese as I thought of additional areas that may require access as things progress. A pattern has been made for a 7Kg ballast, which is intended to interact with the trim tab and, hopefully, the hull to increase effectiveness. For this reason the main fin section is just a simple aerofoil . Thinking of sail plan now and aiming for 0.8-0.9 sq M. Maintaining the same ratios as typical 6M, also One Metre; which is interesting. Really want to go high aspect, but aware of keeping a sensible mast height. Substantial roach in order here, like the Merlin Rocket main. Here is the main point of this missive. Does any one have any ideas on the project that they would like to see ? Any comments on rig that could give me a steer on configuration. Thinking carbon mast, maybe in two parts. No spreaders. Fractional rig with aforementioned main. I like sleeved, fully battened mains though. All comments / suggestions welcome and thanks to all who have already guided me. Richard

Just waiting for my Flysky FS i6, which is the same as the Turnigy (thanks Tiggy Cat) just a different label. I assume the 3 position switch is easily assigned. The only reason I ask is that the manual does not specifically mention that switch (c) on the assignment instructions. I had one of these when I bought a DF95 last year: really impressed by the boat and the Flysky and only sold on because our club showed no interest in adopting the class. Interestingly, the rig is quite useful and I may put one together for the trimaran. Boat progressing well and looking forward to floating for final trim. The fin and trim tab turned out ok, I did find that the trim tab internals got in the way of any sheet post ideas and have reverted to a bridle. Richard

Thanks Tiggy Cat, that TX/RX looks just the job. Off to buy one now (metaphorically in current circumstances of course) Richard

Thanks Bill, I know Peter quite well and, as you say, Always helpful. Poole is a bit far away now though. Thanks Mike, looks like I may need to buy a new TX then, one with a 3 position switch. Info on tab settings very useful indeed. Richard

I remember sailing an International Canoe, Mike, the sliding seat was fun. May need to start a new thread: Servo control for trim tab. We used an analogue system on Transpac's but I assume radio sailing will be a digital switch Left/off/right. What sort of servo is necessary ? My Futaba TX only has two position switches so how is trim controlled ? Richard

From what I have seen of them and perusing the rules, the A class is a great class. I like the huge difference possible in hull, ballast weights and rig area. Biggest problem is that I have never seen one in the flesh; apart from those in the Poole clubhouse. Also a bit large. My boat of choice for most of my sailing time has been the Merlin Rocket. So much to play about with and experiment. Unfortunately due to crew considerations I realise that I have owned more Lasers than Merlins. I have one now sitting on the front garden, with sailing/swimming on hold. Hence the timely appearance of a boat to play with. I must try to read John Lewis's book

Bill and MIke; very useful and relevant comments and I agree that I would have a preference for a finbox arrangement. Possibly I am being driven by economics here and want to try lots of ideas out on this hull. Fins and finboxes are expensive. The best, I know, are engineering works of art and certainly worth the loot. My fin will be removable though and I will be trying different fin shapes (eventually) I intend using the trim tab for any CLR correction as a simple expedient. Also the rudder. Intend floating the modified hull tomorrow to determine the sort of ballast weight required to come down on the WL minus estimated rig and radio gear weights of course. This is a fun project and the aim is to get a really nice sailing boat and try out some ideas. Richard

I know the A class is a formula rating for sail area, but could I ask if anyone has sail areas for a typical modern A. Just an idea of area, luff and foot measurements. I know the rule states that luff must be greater than 1390. I know this is a bit vague, but trying to get a picture of max rig plan to aim for. Richard

Like Dolphin, I have to accept that I cannot get a useful 6M from this hull, hence just using the rule as a sort of guide and possibly learning a bit about 6Ms along the way. Damian, I have already looked at your Drisky, which certainly looks the business. I had not seen those pictures which are very informative. For example the trim tab is much bigger than I expected, usual problem with scaling for me there. As you say, the fin area is interesting. I am re thinking the chord length as we speak, not sure what thickness to use 14mm has been suggested, but seems a tad excessive. Not asking for any trade secrets here, you understand, just a steer in the right direction. Going to build a fixed fin around a carbon tube and skin it with carbon sheet; thanks Dave for advising me against a removable fin and a finbox. Do you make those ballasts ? That is the one item I'm searching for.

Thanks Tiggy Cat Thanks MIke for the measurements really useful and give me a sort of benchmark of area to suit resulting forces from approx 0.7 sqm SA. I assume that you have Grahams inverted triangular fin. I think I will go for vertical leading and trailing edges though: offset the wetted area for maximising the end plate effect of the ballast, especially for such a short fin. Using experience from large boats here and very happy to be proved wrong. I have acquired a scaled down (X0.66) Moby Dick ( J Lewis) hull, nicely planked and substantial enough to withstand surgery. I would guess a similar block coefficient to a Dolphin. to give you some idea where I am. I will not be able to turn it into a legal 6M but will make a sort of "super 6" for fun sailing. Any comments on trim tabs ? This project is an un planned diversion from current efforts at foiling with a very different sailing experience ( 15% foiling, 35% getting into position for a foiling run and 50% rescuing capsized tri) A spin off is my rescue boat which has proved very successful, is very compact and uses ultra simple bits. Richard

Modifying a planked hull around the 6M rule. 1510mm LOA I would appreciate and dimensions or sketch of a typical 6m fin and planform ballast. I know the variation depending on the measurement formula. Have cut off existing lead filled fin and will make a fixed fin around a fixed 14mm carbon tube so need a rough idea for fin depth, chord and length as a starting point. Also looking for a ballast casting. What is a typical ballast weight ? Lastly: Rule 3.3.7 appears to allow trimtabs. I am keen to incorporate one into the fin . I have not seen any evidence of them being used in the class however. Sorry but only ever seen one 6M in the flesh ! But I did once own a beautiful Dolphin hull obtained in exchange for a One Metre. Richard

Have been looking into 6m for a while now, but totally frustrated by lack of mouldings / plans or anything to encourage someone to put one together This looks really interesting and I would certainly like to see some more info. Richard

The trimaran shown in pride of place on page 6 of the yearbook is one of Ian Holt's Box designs. Shorter than the Mini40 rule maximum, at One metre. Note the outboard foils. Much smarter than my own foiling trimaran; I must say. Richard