Just to clarify a few basic engineering principles.
Engineering strain is dimensionless. So multiply by length to calculate actual stretch to achieve a certain preload.
Strain is for the elastic range of the material. Cross sectional area or wire diameter is not a factor.
Preload by strain is the most accurate and repeatable method of tensioning (preloading). We also use it for bolts, pin joints etc.
The whole purpose of preload is to avoid unloading the rigging under any conditions. You want the minimum preload your rig can accept. Any more is just compression loading the mast and lowers the buckling stability of the mast.
Ideally you want to know how much your rig will move under all conditions. This is impractical to do on an actual vessel. So rules of thumb apply with caution.
09-02-2011 10:32 PM
07-03-2011 08:52 PM
OK, I have done some homework. I have read and then skimmed these posts, learned a couple of new words and will be able to impress my big boat friends. I just bought, however, a sweet little 10' dinghy in an auction. It is not a Minto. It is fiberglas with teak trim. When I unwrapped the wood mast and sail I found a gaff rig. I then noticed a number of brass (bronze) rings, jam cleats and holes scattered throughout. I have found a drawing of a gaff rigged larger dinghy on the internet, but I cannot tell some of the drawn lines are edges or lines (for attaching things). Does anyone know of a source of a rigging diagram for one or more of these boats?
I shall send a photo of the boat when I have cleaned it, oiled it, etc. I would also like to know who built it and its name if any. I heard a rumor during the auction that it was built in England.
10-10-2010 08:15 AM
#1 thing for EVERY tool box is a roll of duct tape. There are few things that this stuff can't fix or help fix. Just wish I had invented it!!!
10-30-2009 10:58 AM
Hey everyone. I'm new here (as I'm sure you can tell). As we are talking gear, what tools do you think makeup the perfect small toolbox? What tools do you rely on more than others?
I have several tool boxes for sailing, packed full of random things, so i thought it would be good to see what is absolutley essential.
06-07-2009 10:41 AM
What a great Sticky.
Just wanted to add a tool that I recently picked up from Lowes. I havent tested it yet but as per the original post stating the importance of a level boat to start with I think this might help and actually picked it up prior to reading this.
It is a Ball level. If you are not on level ground you can figure and mark the level horizontaly then compensate for vertical and even check the degree of angle on the rigging from port to starboard and make certain they are equal .
06-06-2009 02:35 AM
How to Center your Rig
Here is a link to UK-Halsey's video on centering the mast. it makes good, simple sense to me.
i race in one design keel boats some of the time. rig tune is paramount to sucess. so i thought i would chime in a few fine points for those looking for them (like the comment on how to tune your rig for 20 knots).
sailboats have generally two modes upwind. seeking more power, and seeking less power, with a small happy medium in there. there are of course things we do with strings to help with this, however, mast tune is more significant, that is like a coarse adjustment, the strings we pull the fine adjustments.
i would also side with the disclaimers that have been mentioned, but you may want to consider going too much with an adjustment. that is go too far, far enough that you will know it is too far (performance will suffer). then you will know it is somewhere between those values (of too little/too much).
all of this is for uphill travel...
mast position in the boat (fore and aft) is critical. every boat is different in this regard. talk to other people with your boat and see what they have found out. with the butt, partners and forestay length you can control mast rake. if you have too much weather helm with mast rake right, the mast needs to move forward. not enough, mast needs to move aft. this is assuming your are trimming everything right. highier winds we use less rake, that is we shorten the forestay for the same butt position. other boats move the butt around. both work, but forestay length changes other things as well, and i think is generally easier. i don't know the math on degrees, as we measure the forestay length for the adjustment, but i would suspect we vary the rake by several degrees.
optimizing for light air. forstay sag is good in light air as you are trying for max power. you can try the same on the luff of your main by letting it sag off. how much, well you can try too much and then tighten up from there. too much sag will break/bend your mast. don't send me the bill. i would think somewhere around one to one and half mast diameters would be ok. this is what we use. as the wind builds and the boat is not needing as much power you can bring the mast in line. you do this by adjusting the lower/intermediate shrouds.
for high winds, the opposite is true. you will want no forestay sag (impossible), shorter forestay, less rake (butt aft, wedge partners forward). you will want your mast straight side to side, with more prebend. ideally, you will want the top of the mast to fall off some. fractional rigs do this better.
you can adjust some of this with a backstay adjuster, but really you need to get up there and adjust your forestay length/butt/parnter position to optimize your boat for any particular windspeed. most people in crusing, even racing boats will not play with there upper/intermediates/lowers at all. they have a set it and forget it attitude, especially with discontinous rigs. there is nothing wrong with that, in fact a lot of sense. tune for midrange and use other adjustments to keep the boat on its feet/use the engine if there is not enough wind.
downhill is different of course and mast tune is not as critical. you will want to undo as much rake and prebend as possible with your set up. having the mast tilt forward is best. you cannot do this with spartite, but you can with removable fore and aft wedges.
best of luck...
05-24-2009 08:12 PM
Ok...I just said to my wife, "You know, I think I can fix this rigging myself..." We had an after shroud break on the delivery along with a fore stay. The release in the tension caused the mast to shift now it leaks at the deck into the head.
The boat is a gaff rigged ketch and I am calling a rigger...HA Thank you for the info, I am not a moron, but this is beyond my current skill level.
03-28-2009 02:56 PM
Along this line but different. The tang fitting, the fitting that accepts the
marina fork at the mast, how much movement should it have?
Bob SV Journey
This thread has more than 10 replies.
Click here to review the whole thread.