martno1fan

multiman dont worry mate i was just joking with you,tri keep trying lol!! what foam did you make the outriggers from on your tri? it seems a good idea for a quick way of trying out a multi.especially for guys who dont have much money and have a spare hull lying around.i presume you just removed the keel and made a fin without the bulb.multiman what boats did you make comercially?.by the way welcome to the forum mate .

Multihull Fan

I have been a follower for some weeks now just as a guest, and it seems to me that our dear friend Martno1fan has a habit of upsetting or 'shooting down' other people on here!!
If Multiman is who I think he is, he is one of the most experienced Model Multihull builders and sailors in the UK, particularly in Catamarans. He has also built fullsized sailing Multihulls up to 13m, and built F1 Catamarans! It was through him and his entusiam for MINI40s and the MIM, that I bought a second hand Machete and used to sail it, and are now trying a MIM.
The whole point of ANY FORUM in my opinion, is to exchange ideas and experiences, from which any other interested persons can either take in what they say, or leave it.
It also seems to me, that so far on this FORUM that there are two DIFFERENT Ghost Trains! One a 1M, the other a MINI40 Class! Maybe that is why Martno1fan is not able to understand, and why yet again he is making such flippant remarks! 'HE' may find some things repetitive, but whatever Multiman has said, he, nor anybody else for that matter, deserves this form of comment when he is trying to put his point across!
Or does Martno1fan think this is his website and his FORUM to make cryptic and needless comments?
I have as I say been a keen 'Guest' on here. I have joined to just point out to you lot on here that everybody has some experience or point of view! It is the very point of a FORUM!! Maybe Martno1fan should get down off his pompus step ladder, and give everybody a chance without him 'shooting them down in flames'! If he feels that he is so experienced and above all others, then maybe he would like to tell us his untold expert opinions once and for all!!!
Until then, I hope all you others continue in 'your help and opinions', and can do so without the seemingly endless 'hassle' and needless 'quips' from Martno1fan!
Multihull Fan

martno1fan

lol whats that ? when did i shoot anyone down?i think multiman took offence to a joke i made to tri about my dog which was not meant as a put down to anyone.he also made the yawn comment himself during his lengthy post to which i replied with a yawn(joke)also i pointed out that it had been mentioned previously about the ghost trains problems not becauase i didnt want to read his comments but wanted him to know others agreed with him.and all that stuff about if he is who you think he is stuff makes me think your one and the same person?and took offence for some reason?.either way i did not shoot anyone down at all i made a joke to tri and mutiman took it the wrong way,he then maybe took my yawn comments the wrong way too but i was merely picking up on what he did himself.all that said i also welcomed him to the forum and asked him who he is and what boats he produced and hopefully he will reply theres no reason to hide were all here for the same reasons.

Thumper24

Hi Guys,

Ever heard of turn the other cheek. I look at this board and a few others for info and pics not people angry at each other, I'm kinda sick of it. Her are some good ideas when posting. 1. If you don't like martno1fan's comments ignore them, it's not as if he is standing infront of you, respond to the constructive points. 2. Martno1fan if you don't think someone took your coments as a joke, just post a one word repy "sorry", it makes you look better, and it ends the hostility. Then move on. 3. All of you provide a different perspective on RC boats due to your background and experience, and I'd like to hear it, so quit whinging and lets hear the good stuff. I need to build a new boat before the thaw.

P.S. Took me a few tries to remember how to spell whinging, I've been out of Australia for a while.

keninoz
Freezing in the Great White North

martno1fan

good point mate but if you read back a couple of posts i did let multiman know i was joking ,it was just he popped in during a bit of banter between me and tri.also some things i said were taken totally the wrong way like the thing about my dog and mentioning the ghost train which wasnt meant as a put down ,far from it.hopefully thats cleared up we can get back to talking about multis and having some fun?.Ken i was gonna say something about ausies and cricket[:@] but i dont wanna offend you welcome to the madness mate.

tricat

Hi multihull fan,Nice to hear from you,I think I may have confused things by my arrival on the scene.It was when the Ghost Train was being discussed re stabilityof the pitchpole type.I made a comment re the three centres of bouyancy needed to form a reasonable triangle for good stability.
I can only refer to my testbed 1metre which has the outriggers set forward to give more stability.
The method I used to find how much forward to set them is nicked from a tip of tow hooks on 100S gliders and hoe to find where they need to go.It was as follows.Take the centreof gravity of the glider,drop a vertical line down from it,drop two more lines down from the same point,one at 30degrees,the other at 35degrees,both angles are measured from the dropped verticalsloping towards the front.Where they cut the bottom of the fuselageis the point the hook should go.Either side of it and you will most likely rip the wings off the glider.I applied this method to a plan of my
tri.using the centre of effort of the total sail area as the [centre of gravity]took out a line at 90deg.
to the centrehull centre line at this point,then drew the two other angles in.Where they cross the centre line of the outrigger is a rough guide to where the centre of bouyancy should be or just a tiny bit forward.It stopped most of my turnovers and it has not toppled over forward since.Most capsizes
are, being picked of the top of a wave by the wind.The trouble with this is that most multis are ruled by the box rule.Why I ask,a monohull needs the hull length rule to govern displacement hull speeds
due to length.A multi as long as each hull fits the class length[whatever it is]the overall length does not make it go faster,only by the fact that it does not capsize as much.I do not know whether this applies to full size multis,I only know model multihulls.Unless of course it's harbour fees which govern the full size multis.Any thoughts on this??! cheers all Scotty

MultiFAST

Multiman -

I would be interested in knowing how those 1 Meters sail that were a monohull conversion. Was there good/bad points to the conversion, and what were the findings? I am particularly interested in how a wide, displacment type of main hull works once the lead is removed. Do you see any negative issues in doing this conversion as compared with a multihull designed to be a trimaran or catamaran from the ground up?

Obviously there is a cost and time savings for those who want - but don't want to build - two or three hulls. I see the conversion as positive - but wonder about the hull beam versus the narrow, skinny hulls usually associated with a modern multihull design. The fellows in Australia that were experimenting with converted Marbleheads seem to bear out the fact that while fast among themselves, they are often soundly beaten by a true, multihull design - not a conversion.

Your observations ?

Guiri

I don't know whether it's on topic or not, especially as I'm having a hard job of convincing the rules inventor of the proposed M505 class that a tunnel hull is a mono. However, I was intrigued by the possibilities of the full size Laser Vortex scaled down to 505 mm. So, I carved a hull out of foam and am now waiting for the epoxy to cure.
http://www.rcgroups.com/forums/showp...4&postcount=35
As hamsters cannot be trained as crewmen, I'll hang a 25 cm ballasted keel from the tunnel centre to replace the original dagger boards.

Multiman

Hi MultiFAST,

You need to talk to Tricat about the sails part as he is the one with 'MrX' that have been developing them more than me. I am more to do with the hull designs and are more experienced with MINI40 Cats and Tris.
As for the Mablehead conversions out-sailed by the MINI40 equivelent, it is probably because of the way the hulls are put together, ie all three hulls should NOT be in the water at the same time, and yes, the narrow hulls will be slightly better.
However, as I stated above, it really is more to do with what sails you have, how you trim them and how good a sailor you are! The overall weight need not be another cause, although at that size (48" or 1220mm) the lighter the 'arrangement' the better. I think the Marblehead Hull will not be better than a MINI40 (or F48 as they are know in the States) because it has been designed and built heavier because of carrying a lead ballast of up to easily 21 lbs! A MINI40 (orF48) will generally be around 5-7lbs on the water, and therefore I suggest be better than a Marblehead conversion.
However, any means to get a Multihull up and running is far more exciting than a Monohull, and I suggest would easily outsail a Marblehead in moderate to high winds! In the M1M Class, there is none as yet that has produced as light a set of mouldings as the 1M hull and two 'Foamy' floats. The weight difference is much smaller to smaller you go in scale and the use of these developed LOW ASPECT RATIO sails are by far the reason why the 1M conversions sail so well. I have come up with a 'SQUARE' rig, but it has not been tested or compared to Tricat's rigs as yet. This will hopefully be rectified when I go up and sail against Tricat and the phantom 'Mr X' !!
In response to Guiri, I too agree that a tunnel hulled mono, is not a Multihull, and adding any ballast to a Multihull in particular, is completely defeating the object of being a Multihull !!

MultiFAST

MultiMan -

a purpose-built 1 Meter tri that began life designed from ground-up. Intention was to be able to use 36/600 - or 1 Meter sails/rigs, as shown in photo, but I also have a purpose built sail set well above the normal 1 Meter sail areas but probably good only for extremely light winds. Hope to get this one out with some more on-water photos and video to see how well it handles the heavy stuff. As it was originally designed for 1 Meter, I would hate to have a 1 Meter conversion suffer if sailed against this one. Then again, the other way around and it could be embarrassing to me.

Thanks for your response - will look forward to anything that TriCat posts regarding conversion performance.

Multiman

Hi MultiFAST,

Nice looking Tri there, what's it's total weight? It needs to be around 4lbs on the water(sorry not that metric!) to even come near to a 1M conversion as used by Tricat and 'Mr X'. Your centre hull is how your floats need to be (in my opinion), as the greatest need for buoyancy on these smaller types is diagonally forwards.
Your centre hull does not need as much buoyancy as it is the floats that takes the loading. The centre hull does not need as much as you have. The other way to get around where you have the floats, is to mount them further forward from six to ten inches as Tricat and 'Mr X' do, which is perfectly acceptable in MIM (Multihull 1 Mtre). If you look back at Tricat's boat, you will see what I mean about how they are staggered forward. What you are looking for is maximum stability, and if you can't do it with buoyancy, then use leverage by moving the floats forward.
You should have between 10 and 15 pounds displacement in your floats at this scale to give you an idea of what to aim at in your floats, but you can end up with less if you move the floats forward obviously. Beams can be from 6mm Carbon tube, although a shorter lenght of 8mm strengthening has been used to stiffen things up on the forward one. The swing rig masts to can be 8mm and 6mm booms, and the use of a drilled carved wooden block to join all at the bottom as per Tricat's yacht.
I make GRP hulls which are light and strong, but the floats can never be as light as the 'FOAMY' floats they use, and my GRP laminate is lighter than a Balsa build up!!!

tricat

Hi multiFAST,You can see photos of my 1M multi on page 5 of this forum,but we have moved on a bit since 2005.If you click on my profile you will see some shots of the rigs.the small dumpy rig is around the same area as the 1M top rig.It is designed to flex with the gusts in a manner that allows the main to be set at a better angle to the wind thereby getting more drive.I would say a well designed multi[designed to be a multi]will always see off a well put together bits of other boats multi,as you can but more go faster principles in them.My sailing mate did not just put bits together and call it a multi.He knew what he needed in designing a multihull,but he wanted something that he could alter, reshape or have more than one without spending loads of money.EG :-take one outrigger float,If you need a little more bouyancy.or more rocker and then find out it was the wrong thing to do,you need more floats[MONEY]We don't,we can pack out to the shape required,and if required,put more rocker in where we want it all at the water side taking all of 6or 7 minutes.If any one of the ideas is not acceptable we remove it in about 2 minutes.Our floats cost at the moment,about £5.5 for 3.Although I shape mine at the bows,my mate does not.He has sailed in a lot stronger winds than me,and does not appear to suffer from the waves to much.My top rig is in the region of 1100 sq ins.and as yet not had any hairy moments[That's done it !]If you look at the videos posted you will see it really gets a move on.It will see off a 1M mono in any direction most times[Not all]If the 1M can use its weight[stored energy from a gust]and the wind is pulsing at the right frequency it can be very hard work to better the mono[But you only need one gust that is a little longer than the average and it's bye bye monohull.]Reasons why a multi put together from bits may be slower could be the centre hull is designed to carry alot more weight and is designed for that weight so the shape will be not the optimum shape,for one thing its waterline length would be too short among many other problems.No you cannot add weight to bring it down to the
waterline.Multis work by more sail power to weight ratio plus a better sail platform.the floats we use
are 2.5inch dia 1 metre long closed cell insulation foam for .5inch pipes yes they are stiff enough at all times but do sag a little when the temp is above 24C but come to no harm as you jusy bend them straight in about 3 seconds.They last about 2yrs before they need to be replaced.
Hope that helps for now,more info if required.Regards all Scotty

Multiman

As Tricat has pointed out, these 'FOAMY' floats are light and 'bendable' and thus why they are at the moment unbeatable as far as making a GRP or rigid profile float! If you have light winds, these floats can be bent to any desired shape, so for instance in light winds, an enlarged rocker can be put in and keep drag down! When it blows up, this can be straightened out to whatever you desire, or works for your craft. Try doing that with a GRP or rigid float!! They also only weigh 5ozs, so you would need to equal that and then have a number of different shaped ones to be as good!
The other thing that maybe I nor Tricat have pointed out, that the weight of your rig is also very important. I did say about the use of Carbon tubes as per the photos provided by Tricat earlier. It should be pointed out that hese rigs weigh only 7 - 11 ounces, and therefore your critical Top Weight is also lower than a normal 1M rig. It is this overall look at weight saving that MUST be observed with any Multihull, either full sized or in model form!! If you cannot accelerate with the wind, then it will bowl you over, 'pitch-pole', 'trip', 'capsize', ...whatever you want to call it!!
As I said in a previous submission, hull shapes are not as critical as your sail shape and trim and then the way you personally sail it! Whilst Tricat is correct in saying that a pupose built Multi should be better than one made up one, it is the weight factor and where the bouyancy is that is critical here at this small scale, and you MUST have decent shaped and trimmed sails!! If you can't get the weight down to these present made up M1Ms as per Tricat and others, then don't waste time trying to build hulls that are heavier and have their buoyancy in the wrong place! Throw one of these quick and easy made up M1Ms, and get out there seeing for yourself what fun they already are, and then you will see how to improve the design of your own design!
Trial and error is by far the best way to improve any design, so get out there and have a go yourself before making elaborate time consuming models!! The other thing is always sail against another person if possible, and by doing so you can alter and improve one boat, and then the other. 1M hulls do have to carry a weight where in Multis do not, and rightly pointed out do have either more rocker of beam than neccessary for a Multi. However, as an easy and relatively quick way to get a useable centre hull, they already have a rudder and fin location if you buy second hand. This makes it an easy task to make different Fins and Rudders to suit any wind condition. Making a purpose built Multi at this size becomes difficult to get to the weight, and have the same adaptation as these 'FOAMY' floats. The fun you will have with them is impossible to put into words, and you will wonder why you did not try it before!
If you can, get to sail with Tricat and his friend, and you will get help and see how to improve your own design.(Sorry Tricat if that is imposing on you!) They have far more experience than me in M1Ms, as I can only go on my experience in the larger MINI40 Class, full sized Cats and my own M1M designs, which have not been compared to Tricat's as yet!

MultiFAST

Regarding your sails - are either of you doing anything special with battens? The green main in photo has 7 battens and only two near the foot are approaching full length. We seem to have found "wrinkle" problems when the entire batten is adhered, and are considering just attaching at front and rear of batten leaving the remainder free to bend however it wants. Have tried a pocket, but this extra material and reinforcing seems to add unwanted additional weight above the waterline, so have discarded it. Battens that seem to work well are about 1/4 inch - 4mm wide of styrene.

The upper rig that was designed/built specifically for this application is approximately 1250 sq. inches (about .81 sq. meters) with a square top main. It is a bit too powerful for this size as I previously noted - except in really light winds.

Note that the main hull was originally intended to allow two of them to make up a catamaran - thus the large forward buoyancy.

martno1fan

hi guys ive been reading your posts with great interest and all of what you said is very interesting indeed.can i ask about this foam you have used for the floats what is it and where do you buy it? .i have a small sail boat LUNA ROSA scaled down to 34 inches long and 4 ft high i might have a go at making this into a multi for a bit of fun.i will still be also building a mini 40 multi NIGHTMARE from plans too but while im building that it would be good to get a taste for how these boats handle.any help you can give me on where to buy the foam from to make the floats would be great thanks.

tricat

Hi martno1fan,Yes for english readers try B&Q and similar type super markets,look in the plumbing depts.for pipe insulation.It is sold as a silver grey 1 metre length
packs of three.There are two types one for 1cm pipes and one for 3.5cm pipes,get the one with the smallest dia. hole.there is a smaller pipe insulator but it is of no use for multihulls at the moment.All these pipe insulators are pre cut lengthwise so you can slot them over the pipes in situ.this is always the top of the float and like the pipes you just slot your attachment for the float into them.If you make the attachments triangular with the single point at the top for your crossbeam you then
tape the precut top with waterproof tape and that is it.if you look at my profile photos and zoom in you will see the basic idea.Hey we do not use any screws,clamps or other engineered methods to put the floats together we only use
electricians tape and waterproof tape,even to fasten the crossbeams to the main hull see also the photos.The crossbeam mounts are 20cm long with a 'V' shaped groove to grip the crossbeam.These are also taped together.Do they work?Two years
of sailing in all weathers,and only one mishap.Always make sure you make two complete turns around the crossbeams.After long while ,water and sun allow the tape to slip,any less turns and they may come unstuck.For other countries the floats are closed cell plastic type foam insulation pipes.they cannot soak up water,they cannot sink,they are quite bendable,they do not suffer much from flexing in heavy weather.ideal for plumbers,and multihull enthusiast,????!they do not cause much damage if they collide with other boats or jetties !More info if required regards all
Scotty

tricat

Hi multifast,Because of the Dumpy rigs requirements and its looks,I ventured down the Chinese junk rigs.It has led my mate and I into an area where he understood
thing and I did not at first understand.As an ex dingy racing type this annoyed me as I could not do what seemed the right thing.If anybody said camber in sails is the last thing you need,I would have argued till I was too old to talk any more,but my mate slowly got me to except it.The junk sail relies on twist rather than camber in the amount that is excepted today.What would you do if one day you thrash the heavily cambered yachts into the distance in light winds with dead flat mainsail,a jib with only 8% camber set at 15 degrees out plus the fact it was around only 1 metre high.We checked this out.The high aspect sails needed camber,our large area mains did not need much,if any ?!We now use big mains made flat and allow the wind to give it a little camber say 3 degrees.Since then we have started to look at vortex
inducing rigs.Thanks to Frank Bethwaites brilliant book on the Sydney harbour 18ft
skiffs and fast sailing.The crab claw sail also draws my attention for that very reason.It mentions that the vortex drive gives large amounts of drive,but if camber is applied it kills off this drive by unacceptable amounts,as the sail is small compared to the bermudan rigs for a similar size boat.Occasionally our multis
are flying along quite fast when a gust strikes,they act as though a turbocharger has kicked in,they just take off,if you luff very slightly you find that the lee hull actually lifts up a little.This is where I want to know how can I get more of this power for longer.I am sure this is where the model multis of the smaller sizes
like the m1m need to be looking at for good performance.More info if required
Scotty

martno1fan

thanks scotty would it be possible to get some close up pics of your cross beam connectors and attachment points on the main hull so i can see what your talking about in more detail.sorry to be such a pain but im very interested in trying it.the boat im planning to use for this is the one in the pic.the sails on this one are flat sails any tips on anything i can try to make them better for this project.or should i just try these and see.

tricat

Hi multifast,I have posted two videos on www.rcuvideos.com,bring it up and type in klingon 5.this should bring up the two short runs of my multi with its top rig on in variable winds 3 to 8knts.As matno1fan says did I hit a duck 'cos it stops rather quickly at the end.No I was testing how flat I could go on the rocker of the outriggers,and found it awkward tacking at times.So I just bent the rocker back in[30 seconds job]see my profile gallery for still shots.Regards tricat

Multiman

Hi MultiFAST,

Your present Centre hull as a Catamaran is absolutely great, so where is the Cat? Think it would be a great Cat, and think you should have a go with it as that. I may be a little biased there, because I have concentrated more on Cats as no-one else likes them much!!!

I find that the best beam is around 85 percent of the lenght of hull, and you can use 8mm Carbon Tube for the beams. You can use a vertically mounted anodised Aluminuum Shower rail as the Centre Spar, after it has been lightened and kept as short as possible. The beam holes are best reinforced with a short piece of 10mm Carbon Tube, say two inches eiother side. The Fin, Rudder and Mast Step tube can be fixed to this Centre Spar, and the Winch and Rudder servos made waterproof and bolted to the Spar too. I did have all the Radio gear and winch distributed amongst the Hulls in the CHEETAH Mk I, but it was difficult to get the weight distrubution just right. Also the sheet lead was long and when wet got tangled easily. The RX and Battery can be made waterproof by the use of Cling Film, and attached to the Centre Spar too.

The other thing with all Multihulls full sized and Model apart from keeping the weight right down, is the rig wants to be as far back as possible! The Centre Of Effort(COE) being moved back should also be complimented by the Centre Of Lateral Resistance (COLR)moved back correspondingly! The use of the shower rail groove at the bottom, easily allows for you to move the Fin back and forth! I use a Clamp arrangement for the Rudder Stock Tube mounted at the end of the Spar. I have some pics of that on my MINI40 CHEETAH, if I can get the blasted things on here if you want some. Certainly the Cat will be quite easy to get up and running, and will be hopefully down to the weight too. I have already done one, but have not yet tried it against Tricat and 'Mr X' yet!

By the way, Tricat and his friend also started out in Multihulls by using two 'Foamy Floats' as Catamarans!! These boats cost less than £20 to make with your own radio gear, and are another easy way to get on the water. Tricat has some pics of those too! The main problem was the Beams caught any rough water and stopped them dead, but they progressed on up to the Tris using the 1M hulls they bothe had and find it more rewarding and of course have developed all these fancy sails.
I have also come up with the 'Square rig', which is obvioulsy a square mainsail, and a rectangular Jib on a Swing Rig. There is a Top Boom arrangement mirroring the bottom(similar to Tricats sail arrangement), and the sails are suspended in each corner of the main, and on two more swinging jib booms hung from the forward booms, which are adjustable for the 'Slot'. Again, because I do not live in an area that I can easily use these boats, the trip up to Tricat and friend is going to be needing a van for all the boats and rigs I have to compare with theirs! M1M Multihulls are very much all about getting anything together and getting out there to see what works and what doesn't, without any silly rules to say you can't! That's what makes it more interesting and fun, and why you all have a go!

I did say before I would put some pics on here of my MINI40 Cheetah, Mk I & II. However, I am not finding that easy to do so far, and this is the third time of writing this all out again!!

Multiman

Hopefully these pics (if they are attached) show a MINI40 Mk II CHEETAH, and show an early Mk I CHEETAH overtaking a MACHETE Tri!! The Cats out accelerate Tri intially, and when the wind is just right! In the one shot you will see the CHEETAH Cat having just got one small gust that took it from being five hull lenghts behind, to five hull lenghts ahead, and on one Hull !!!! In moderate winds these are quite normal and the Cat will do very well indeed!! It is in the lighter winds and heavier ones that you have to concentrate!! The rigs I use are usually the same as the Tris, but I have to change down earlier than them.

You may also remeber me saying about Tailfoils on the rudders before too. In the heavier stuff they are overall needed more for the Cat as it it lighter and tends to tak off!!! The Foils help keep the thing literally slapped down on the water, and it shoots off in a cloud of spray like it's on rails!!! All very heart stopping, but such great fun!!

Multiman

For general information, you can also ADD buoyancy to the front part of your Hulls and Floats quite easily. You will see by (hopefully) the attached pic how I have added some carved and sanded Polystryreen foam to the front Floats of my MINI40 MACHETTE Mk II. This only takes a few minutes to do, and when needed is held in position by again the use of Cling Film!!! They will get damaged if you start running into things such as pontoons, but it is an easy method to gain that extra buoyancy if you want to sail upright in a gale or two, or if it is very rough!! It is light and easily worked, and in fact you only really need a solid bottom half to a hull, as the top part can be the use of this Foam and keep the weight down! It also adds quite a bit of stiffness too, if you are using a cheap and easy GRP mould, where you do not need a 'Split Mould'! You can sand and shape the polystyrene to the shape of the hull, so the Foam is the Hull and the GRP laminate is the hard outer protective shell. It is a much easier way to make a hull, make it unsinkable, and repairable!

Now I am able to add pics now, here are some more of the MINI40 Mk I and Mk II CHEETAH Cats of mine.

tricat

Hi martno1fan,I would for the time being use the present rig as it is.I do prefer a swing rig,because you need a big roach to make the flexy side of things work.It is the top half of the sail that does all the work,the bermudan style would not have enough power in this area.For your cross beams you will need,1 of 8mm carbon fibre tube and 2 of 6mm tubes.cut the 8mm in half,as this is the part fastened to the main hull about 200mm from the bows.Make sure that the wood beam that has the groove in it is really well secured as it takes far more punishment than the back one.I use 1cm square hard wood block glassed in and shaped so it locks under the gunnel.Make sure this is waterproofed as well.I had one first pull loose,then the wood got wet and went soft.The screws pulled straight out,it was quite a laugh trying to steer with wayward outriggers and not much stability.The 6mm tubes must slide through the 8mm tubes,some 8mm tubes are thicker and are less than 6mm inside diameter.Multiman has given the optimum beam of 85% to 87%which
also fits our thoughts on this.It allows the yacht a little less stiffness and so assists the centre hull to lift out a bit earlier.We tried this out with one float at full 1/2 metre and the other at 87% of this,one one each side.there was little difference that we could see.If it allows the multi to heel easier it must lift the centre hull thus less drag/wetted area ?!!Once the centre hull is clear of the water it's full weight kicks in which is what is wanted.Hope this helps,Scotty

tricat

hi Multifast,in reply to your battens item.At model level even the top sailmakers have difficulty making full length battens pop over when tacking,there is not enough length of batten to let it pop over.I've tried attaching the leech end only,and then tapering the other end but found that it worked the wrong way round.When it was calm it held the sail flat,when it was windy it was not strong enough and being so gave you more camber etc..I have tried,thin piano wire,woven fibre packaging
strips, carbon fibre rod,fibreglass rods.On high aspect ratio sails there was very little difference,the best was the woven fibre.It was easy to cut with scissors and shape into tapered ends,it did not break.To describe it,it is used to secure the cardboard packaging of washing machines etc..Some times it is a solid strapping other times it is woven and about 1cm wide.I used this on spinnaker ripstop lightweight cloth,using the overlap of sailcloth batten pocket[built in when making the sail] for a fully battened mainsail.the cloth was unsuitable for this as it did have slight stretch in it.Too much for a model yacht if used in moderate winds for long.It did allow the sail have a fair set to it.Now as you see I use film sails and c/f battens with 48cm length for twothirds of the sails,the rest are 23cm or so long.because we are trying different methods in order to get better sails we just stick our battens on the sail with waterproof tape,so that we can move them easily if required.
The final thing is that as said before we want flat cut sails by the very nature of trying to encourage vortex drive if possible,that means about 3% or less of cambre[how do you measure that!!!]
we don't we let the wind force it into sail which is easy with the large roached mainsails.Hope this helps,has anybody else ideas on this problem?Scotty

MultiFAST

Tricat -

thanks for the response. You are pretty much confirming my thoughts regarding sails and camber. In big multihull boats, the need for paneled sails is called for because of the size limitations of sail cloth, but even there they build them flat when compared to a monohull sails of the same general size. For the 1 Meter, I have found that "Flat is Fast" for everything except real heavy chop or waves when the power from a bit of camber seems to help the "drive" of the sails. Other than that - in both heavy and light winds, flat seems to work fine - and since there is no limit to the size of available cloth, why go through the bother of building a paneled sail only to cut seams so drastically flat and straight to get back to your optimum 3 degrees of camber. If you need more camber/power - simply inhauling the clew a bit will give the added camber desired.

A suggestion you might try - which seems to serve me well. Try finding/purchasing 1.5 oz. nylon ripstop that has been coated. It seems to be a bit stiffer and not as soft at the 3/4 oz. stuff we see in our general fabric stores. That stiffness relates well to a static shape in most winds. If you can't find or buy through your fabric stores, consider a purchase of several yards from a kite-shop. I have tried lightweight dacron and it is OK for large r/c multihulls but a bit too stiff for the 1 Meter sizes.

As for battens - I guess I will follow your lead and use them only for leech control - not sail shape. Makes sense and is a heck of a lot easier.

Thanks for the reply. Here is a US kite shop that does a nice job of providing heavier weight material for sails.

[link=http://ecom.citystar.com/hang-em-high/ushop/index.cgi?ID=0893SM]US Kite shop[/link]