hi, what boat ist NZL 32
i have plan from NZL 60 (Ac) or Luna Rossa.
i can mail it, if you want.
cu andreas
Andreas S
My friend:-) Nzl 32 was black majic. the boat that won the americas cup in 95. I like building the superboats. I have learn much since building australia II that i feel comfortable going up to black majic. who do you know to get those plans. and yes I am intrested in those plans i was wondering has anybody ever thought about turning those desing into a class all by them selves? we race the victor boat up here in canada. sort of a cheap mans americas cup
greg the IOM has many more items that must be considered before you race. the rig size how much twist you want on the sails. now I admit I am not realy up on the us I meter. Because where i sail. the us i meter is dying. everybody up here races IOM or marblehead. the IOm has different sails, all handling different wind ranges. I have seen a IOM almost become a submarine just bescause the sailor chose the wrong sail rig. ie rig 1 and too much power
i hope this helps but check out the IOm website for more information
cu on the water
cougar
Don,
My take on why the US1M is relatively sensitive compared to the IOM is the high roach mainsail. The high roach main will have a higher tendancy to twist under wind pressure loads than the more traditional low roach main that the IOMs use. Because of this, the twist is much harder to control. If you set up the twist for lower wind speeds, then at higher wind speeds, the sail will be overtwisted and wil loose a lot of power. If you setup the twist for higher wind speeds, then it will choke off at lower wind speeds.
Mast stiffness becomes much more critical for the US1M, especially the lower mast section. If the lower mast stiffness is too weak, then the vang will not be able to do its job correctly to control the twist. As the sail tries to twist under the wind loads, it pulls up on the boom. The vang resists this by pulling against the base of the mast. This also causes the boom to be thrust forward by the vang. This will cause the mast to bend down near the gooseneck if it is not stiff enough. Ths in turn results in reduced stiffness of the vang and reduced ability to control the leach tension.
It is my impression that many IOMs use keel stepped masts with raised partners to help increase the lower mast stiffness. Of course the low roach main is not as dependent on the vang to control twist, so the combination of the stiffer mast support and the lower roach main makes the mainsail shape much more stable over a high range of wind speeds.
Those are my thoughts on the matter. Not definitive, but I believe they are a plausible theory… What do other guys think?
- Will
Will Gorgen
First I want to address Cougar?s thoughts. The US1M has all of the same adjustments on it that the IOM does, minus the shrouds in many cases, as many US1Ms are shroudless. Is there something else that you might think of? You would certainly consider all things that you have mentioned about the IOM with ANY boat. The IOM has a choice of three rigs, as does the US1M, but the US1M does not loose as much, if any in some cases, sail aria from rig to rig.
I feel that the main reason for the US1M being a more ?fickle? boat is due to its lightweight. Will is also correct that the higher aspect sails of the US1M do make it quite a bit more sensitive to wind variations. I would, though, say to Will that the US1M rig is way more stiff then the IOM. Both classes uses either keel stepped or deck stepped mast, but in either case there is no comparison to rig stiffness, as the aluminum IOM mast is like spaghetti compared to the carbon mast of the US1M.
My first and foremost reason for my conclusion is just plane experience. I don?t know that I could sit here and correctly defend just why the US1M has a narrower ?forgiveness? range, but I think someone who really cares to know can easily figure it out. It took me a lot longer to make my US1M a very fast boat as compared to my IOM. When we race these two classes together, the US1Ms really suffer if they are not tuned just right. When they are, the difference is huge as compared to the IOM.
i have seen IOM s with the mast step on the deck and keel stepped mast. All of my IOM are keel stepped. Is that wrong ? i dont know. but i like it that way. the 2 us i meters I have are deckstepped. all i was saying is that with the extra sail area. you have to watch . that you dont overpower your hull. I dont seem to recall that ever happening to me with us i meters. I have switched my mast in the IOM to 3/8 " just to allow the rig to spill if the wind does become to strong. i could be wrong but that is what i come up with over my experiences. and I am not an expert by anymeens
Hi Andreas!
You said you have plans for NZL 60? Would appreciate it if you can mail it to me at dyopp@yahoo.com
by the way, if I plan to build an IOM basing on plans? where can I get the parts? Would appreciate all the help I can get.
Thanks!
Dick,
I’m not sure if measuring the tendancy of a mast to bend the way you have described is going to tell you very much. It is much more crucial that you measure the mast bend for the installed mast. As you note, many masts use diamond stays or rumpers to help stiffen the mast. On my fairwind, I use my lower sidestays as checkstays to help limit the mast bend. So measuring the bend of the mast sitting on a bench is not going to tell you much about how it will function…
When I bought my new sails from Rod Carr, he indicated (as part of his sail design data) how much mast bend allowance he had cut into the luff of the sail. When I tune my mast settings, one of the things I measure is the mast bend. This can be done by passing a fairly taut string down the back side of the mast from the step to the crane and then measure the gap between that string and the mast at some predetermined location (I use my spreaders). If you wanted to measure mast bend, this would be the way to do it.
Getting back to the differences between the US1M and the IOM. I think Greg has hit on something with the weight issue. A low displacement boat is going to heel a lot more in reacting to a puff. That heeling is going to cause the boat to try and head up which the skipper will then have to fight with rudder control. That is obvoiusly slow. The balance of the boat can be adjusted with rake or mast step position, but at the end of the day, that balance is only going to be correct for a given amount of heel. If the heel of the boat is changing dramatically, the boat will fall out of balance.
The US1Ms at our pond are all “Mistral” hulls. They were all purchased at the same time and built together to try to create a relatively one design club fleet. anyway, the mistral is a fairly heavy US1M design. As such, it tends not to overheel as readily as some of the lighter desings out there. A couple of guys in our club have raced outside our club against some of these lighter boats. They report mixed impressions of those lighter boats. The lighter boat will respond very readily to light zepher winds, but as soon as the wind picks up or gets puffy, the heavier boats do quite well. So I think there is definitely something about the righting moment stability that leads to tenderness in the performance.
On the sail twist issue, I have been using sail photos to measure my sail twist. One experiment I did this summer was measure my sail twist on a very puffy day. I tok pictures both in the lulls and in the puffs to compare the twist. I also took a picture in my garage with no wind for comparison. I would guess that the wind was 5 mph in the extreme lulls and 20 mph in the extreme puffs. I found that my sail twist increased by about 8 degrees between those two extremes. My sail is a low roach, traditional looking mainsail (similar to the IOM)
I would be interested to see what a US1M high roach sail would do under similar conditions. I bet the twist difference would be a lot higher. Maybe the mast stiffness does not come into play as much as I have been theorizing. But if the final result is a large amount of twist variation, then I think that helps explain the fickleness…
- Will
Will Gorgen
A good amount of twist is vital to good US1M performance I feel. Being that these lightweights do heal with ease, you really want your mainsail to twist off a good amount in puffs. This is where the ?THUMBS? come in. Sail trim on the US1M must be very quick . My boom vang is not a compression vang, so I am able to haul in the sheets at the very end of their travel to close up the twist. In puffs, just a fraction of a bit of ?sheeting out? permits the main to twist out to the limit of my adjusted vang.
On another note, just remember that weight adds momentum. This is where we see the IOM and US1M battle it out. The US1M will accelerate a bit quicker in puffs and velocity increases, but when that puff has passed the US1M will rapidly de-accelerate whereas the IOM?s weight will carry it?s momentum right past the dead in the water US1M.
Cougar, No, having a keel stepped mast is not a bad thing. It?s far better then a deck stepped mast, IF you have it set up correctly. And?. 3/8? mast??? Are you sure you don?t mead 5/8? or ?? ??? I have to look this up, but I?m not sure that 3?8? is even class legal.
If you all want to see some decent photos of these two classes, then explore our website at http://ghmyc.org/
hi, the NZL60 ist not the right topic, but ab shot information: in germany thex are a few guy , who are building the nzl60 in 1:18 (about 1,40cm long). the plan are from the internet. there are nor very well to build. but a little they are.
not to mail this plan to to many people, i will put them on my website. (give me on day)
the link would be on the Linkesite at the right under Plans to download.
http://modellsegeln.net/links.htm
sorry the website ist in german.
cu andreas
ps: a very interesting discusion about the IOM an 1us.
But Dick, ?.. I believe you just let you big boat sail makers tell you what you will need, did they not? I did not see them asking in what form your mast bent. They just took the info on what you were using and made the sails fit the characteristics for that combination based on their expert knowledge of what works best. Did I misunderstand?
The same goes for the sailmakers of our small boats. Unless you are using someone new to the market, I think that our RC sailmakers are doing the same as your big boat guys. Only one time during all my purchases on new sail did a sailmaker ask me my mast bend amount. I measure this by installing the mast in the boat, keel stepped, and tensioning my mast to what I felt I would have to do in upper wind conditions. I pulled a line taught from mast tip to where the gooseneck would be an the aft side of the mast. I then measured the distance the string was from the mast at about every four inches. It was very accurate.
To me, this was a needless task. I have always been able to set up any mast I?ve had, to sail perfectly straight or with mast bend. With shrouds and stays I form my mast so that the sail form fit?s my sailing needs for what particular conditions I?m about to sail in. I rely quite a bit on my sailmakers knowledge, as I would not think that I would know more then him. When I ask Alec from Blackmagick Sails to make me a suit for my IOM, I know that he is going to give me what works best for IOMs. When I ask Bob Sterne for a suit for my US1M, I know that he will give me the best design for US1Ms. Same with each class of boat I use.
By the way, the mainsail I got from the maker who had me do all of the measuring? in the trash after the first week of trying to make them work.
I think Greg hits the point pretty much on the nose. The US1M was a United States response to the original proposed International One Meter rule so the boats are in many ways more similar than different. The important choice is to sail the boat that has the best fleet in your local area.
One of the biggest differences between the two classes today is that the IOM is the most popular racing class in the world while the US1M is in a bit of a lull. There is almost constant new design work in the IOM class while new US1Ms are few. Currently the regional and national IOM races are attracting the fastest most competitive sailors in the r/c world while the US1M group is centered a little more around local racing. Of course, all of this can change over time as classes seem to ebb and flow. (I can recall a time not so long ago when the 36/600 was the dominant “small” racing class in the US.)
As to the importance of tune, the IOM rig is a little simpler and easier to set up than the US1M. Also the weight of the IOM and the somewhat greater sailarea makes it a less finincky platform.
… OUCH, Dick, 10lbs and only 1/4" bend? That’s not a mast section, that’s a leaf spring! (laugh).
I guess the way I see it is that I don’t think I’ve ever seen a mismatch between a well cut sail by one of our top RC sailmakers and any mast that I’ve seen supplied by anyone supplying mast. There is someone in MMYC that bought up a bunch of carbon rods and uses them as mast that are way to soft, but he is not a supplier. Even my Soling 1M mast, which is made out of laminated balsa wood, can be tuned to very little bend in moderate to high winds.
A mast that would only bend ?? (I know this was just an example) would be a very bad choice to use in the first place. The sail would at this point have to be made with less luff curve, but this gives you a sail with VERY limited tuning ability. This is one reason I DO like Bob Sterne sails. Many look at his sails and are taken back by the amount of power built into them with the big amount of luff curve and draft. My experience with his sails is that they flatten out beautifully when you need them to. I can use his A rig on my US1M from 1 to 17 knots of wind and win races. They are VERY tunable.
I understand, I think, why you ask if I only use specific sailmaker for a specific class boat. Yes, these sails are always a bit different from each sailmaker, but they all go on the same rig. The rig just gets tuned differently to accommodate the sail cut. Just to say, Bob does make a very fast sail for the IOM, but for my boat, I like a flatter sail.
Roy, don?t look back, but the US1Ms are on a role! (G). I see a resurgence of new designs, new builders, and quite a few new owners coming over the horizon. This year our club will be running a separate regatta series for the US1M rather then combining them with the IOM. We have at least three new hulls coming to the lake for the 2004 season.
Dick,
I don?t really know much at all about swing rigs, but I was under the impression that the had a type of adjustable backstay on them. If you look a this photo from Bob Sterns web page you will see a backstay up close to the leach of the main. No?
http://www.myrc.org/bobsboatyard/viper.gif
updated: [:-banghead] Ooopss, I see what you are saying now. Typical multihull rig, like running backstays. I would think that there is a way to have a backstay, NO?
On the US-1M site then were just discussing mast. Steve Andre put his mast supports 26-1/2" apart and with a 5# weight and got 3mm bend for his Sails etc. 10mm O.D. There are others.
i kinda like the us imeter. it was a class that was put into place so that the skipper would be the decideding factor. I think we have gotten away from that thinking . and that is why we have the one design classes springing up everywhere. if anybody got the idea that i was against the us imeter. i am sorry . I like the class I have 2 of them. but around here (ontario) no body sails them. so I went to the IOms and everybody sails them. this si what i meen my saying to the ppl that first come to sailing. see what ppl are sailing and build to them. after all we all like to talk and we all like to help
p.s. andreas s great web site . I speak a litlle german and could get around no trouble at all. I hope you didnot mind
Dick,
Yes, Rod Carr and I had lengthy back and forth consultations about my mast bend before he built my sails. His specifications that he included with the sails were merely reflecting what we came up with. As Greg pointed out, I can tune my mast for a lot or a little bend, vbut knowing where to start is a big help.
On the mast tuning front, I have several adjustments at my disposal. I want to get a certain amount of jibstay tension (to control sag) and a certain amount of jib boom topping lift tension (to prevent snagging on my spreaders). To do this I need to pull aft on my mast. I can do this with either my backstay or my lower sidestays (which are attached far enough aft of the mast step to be used as checkstays). If I add a lot of backstay tension, the mast will bend. If I add a lot of lower sidestay tension, the mast will straighten or even reverse bend if I overdo it. So i add the appropriate combination of these two to get to the mast bend that I want.
For higher winds, I want to add a little more bend (especially up top) to flatten (depower)the sail and add a bit of twist. In lighter winds, I want less bend to keep the camber full. It really does not matter how stiff or sft my mast is as long as I have the right controls to tune it.
For example - I currently use a 9.7mm groovy aluminum section from Sails Etc. This section is quite flexible. So I have incorporated the lower sidestays that I talked about above in order to keep this section straight. If i switched to a much stifer carbon mast (as some in our class have) I could probably delete the lowers which would simplify my tuning a bit. It would also give me less variables to play with… The main reason I like the groovy mast is that I think the hank attachment for my mainsail give a nicer entry than mast ties would. Personal preference, I guess…
now Dick, for your boat with no backstay, you need to think about how you are going to tune your mast. If you are going to induce bend with sheet or vang tension, you would need to design your sails very differently than if you were to use, say, swept spreaders. You would also, I think, want a very different stiffness characteristic in your mast. Look at the full sized laser mast. That mast is bent with mainsheet tension (to the point where you two-block the main in moderate to high winds) That mast is quite flexible which allows you to do this without over tensioning the leach of the sail. Other boats, such as the 470, have very flexible spars to allow the mast to bend with vang tension. Talk to any of the top guys in the 470 class and you will get an earfull about which mast supplier produces the right amount of flexibility to their masts.
If you use a very stiff mast, then you would need to adjust the sail shape to be compatible with this lack of bend.
By the way, Greg, you should look at some of the wind dunnel test results that Lester Gilbert posted on his site a while back. Lateral mast bend is not such a great thing. I used to run with my uppers quite loose to promore some lateral mast bend, but based on his findings, I have tightened them up. The boat performs much better now. I am pretty convinced that you need to control lateral mast bend and don’t really want that much…
- Will
Will Gorgen
A death roll into a rock pile would certainly bend a laser mast.
To avoid death rolls in the future - shorten your mainsheet knot about 3 feet and never ease your vang downwind in a blow…
But getting back to your original question about mast stiffness - You will need to be very careful to select a mast section that is going to work for your multihulls. If you do not use a backstay to induce bend, you may wnt to think about a fairly flexible spar and then using other rigging to take out the bend such as diamond stays or jumpers. That way, when you want some bend, you can put it in.
If you had a completely rigid mast (no bend at all), then you would really have no way of changing the camber of your sails for different wind conditions. Flattening the foot of the sil with outhaul will not have much affect on the middle or top of the sail. Pulling your draft forward with cunningham/downhaul will only cause you to loose pointing ability and will really not help to flatten your sails either. Now, maybe you can get away with a rigid mast if you depower with twist instead of flattening the sail. but this can cause you to loose performance on the run where the sail will be over twisted.
Another thing you might want to consider (as I mentioned before) is swept spreaders. Many full sized classes that do not have backstays have adjustable sweep to their spreaders that allow them to control their mast bend with sidestay tension rather than leach tension.
- Will
Will Gorgen
To me the Wing Tip Rig™ maybe the best rig for multihulls due to the fact that it has superior planform, doesn’t require full length battens, is adjustable in many ways including an adjustable UPPER outhaul on bent back tip or gaff versions. The gaff version also allows a squaretop jib with adjustable outhaul as well as a backstay…
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
But the IOM class rules don’t allow so called “square tip sails”
Rob