Shifted overlap stay adjuster.

Here you have the design of a "shifted overlap stay adjuster".

It is cheaper, lighter and smaller then any staymaster or threaded turnbuckle. It also allows you to quickly adjust the stay lengths and rig tension without any tools or measuring. You can always find back your old setting as each setting is unique.

The minimal adjustment incrediment of this adjuster is 5 mm in the given implementation, however every amount is possible by modifying the design in the placing of the holes. I chose 5 mm for the given implementation as I believe this to be a good balance between small incrediments and a total range of adjustment. In addition, this setup is easy to use in the drawings and explanation because it has only a few holes. Systems with smaller adjustment incrediments require more holes to be placed in the strip.

I have had a 4 hole strip system on my own boat the whole 2005 season now and the system held up very well. Season 2005 was pretty windy overhere, halve my races were in 15 knots and over with heavy seaway. This makes the test dependable in my opinion. However I will not accept responsibility for any failings of the given design. A bad choice in materials can significantly cut down on the load baring qualities of the setup.

Is 5 mm a too large minimal adjustement ?

In my experience about 50 kg's on the trapeze wire can put a sidestay 1 hole down (= 15 mm) when it was under some tension orginally. This means a 5 mm adjustment is equal to about 16 kg's difference in tension. When taking everything into account a 5 mm adjustment on both side stays will alter your rig tension by about 30 kg. Typically sidestay tension range from 30 kg to 90 kg on modern catamarans, depending on the conditions. The 5 mm adjustments allow you to cover this range with 30 kg, 60 kg and 90 kg. I think this to be a rather practical range of adjustment. With a similar shifted overlap adjuster of 5 mm steps on the forestay the rig tension can then be adjusted by halve of 30 kg so : 15 kg, 30 kg, 45 kg, 60 kg, 75 kg, 90 kg. This I think to be the maximum number of adjustment (6) you would ever want anyway. More are just to many to use effectively.

I always found 15 mm to be too large an adjustment to find the proper mast rake. Rougly speaking, on a F16, a 15 mm adjustment on the sidestays moves the mast top 180 mm (= 7 inches). With the 5 mm incrediments of the new adjuster this is modified to only 60 mm (just over 2 inches) per incrediment. This in my opinion is pretty close to what you want in the way of mast rake adjustment. In my experience any adjustment under 3 mm (= 36 mm on mast top = 1.5 inch) is useless; you won't be able to tell the difference. These 5 mm incrediments allow a full range adjustment of 65 mm which is 780 mm (= 2 feet 7 inches) of movement of the mast tip. This should be wholly sufficient to rerake your mast from sloop sailing to cat-rigged sailing with some margin to get the right rig tension.


The most simple system is just 3 strips of stainless steel with one strip having the holes at slightly difference interspacing. The best is however a flattened tube with a strip sliding inside it. This way you can also add another 75 mm adjustment by having the eye terminal on the stay go directly inside the tube without a strip. Stuff like that amd the fact that a flattened tube looks better as well adn doesn't have any sharp sides.

In the strip there can be slot in which the pin going through hole E can slide. This pin stays engaged and thus locks up the system so you can adjust it on the water (without any tools) without losing your mast overboard. This feature is also handy when reraking your mast singlehandedly, when adjusting the forestay length and when dropping the mast to trailer the boat. All these activities require you to temporarily slacken the rig tension.

However hole E can also be used to get a slightly bigger adjustement range. The system will work either way, the slot and locking pin is not needed for proper operation of the system. It is adviced to tape it somewhat up so it doesn't act as a pair of clippers, when you are not using the locking pin setup.

Take note : hole spacing is the distance between the centreline of one hole to the centreline of the one above it. It is NOT the distance between the top egde of one to the bottom egde of the other !


I think this covers all.

See the pictures to understand how it works.









In my next post some discussion on how to build them and how to use them most effectively.

Wouter

Stop rooting around and trying to re-invent the wheel, just buy a Sta-Master and be done with it. you have infinite and repeatable adjustment.

Sta Master

Wouter,

Thanks very much for taking your time to share this info, I appreciate the simplicity and elegance of the design.

Jerry

Stay master = in NOT an infinite adjustment to locking mechanism makes it incremental. The increments are pretty small that is true ; about 0.5 to 1 mm. Anyway this can easily be calculated by measuring the thread height and dividing by the number of side that the nut has. Also it has a max load of 700 kg and it is cumbsersome to slacken the stays temporarily or readjust mast rake from sloop to catrigged sailing; at least I think so. I personally started looking for an alternative after when I found the stay master unsatisfactory, but that is my personal opinion. I would be happy to have it on any production boat, but since I build my own I could try to get it better.

Jerry, if you are interested and want a different range of adjustment or different size minimal adjustement then I can run the numbers for you. Just e-mail me.

I must say everybody that at first these shifted-overlap adjuster look REALLY small when fitted to your boat. At least I thought they did I expected them to break any second, but after running the numbers I found them to be pretty strong anyway, that is with proper quality of stainless steel. But if you have to use lower quality then just increase the width of the strip and get the same load bearing quality.

Here is the real thing :





Now tell me if that ain't small. The two strips (I have a slightly different setup, but I would have prefered the 3 strip setup) are combined only 4 mm thick. It is a really flat adjuster and weights next to nothing. Staymaster etc are 4 times as heavy. And on our lightweight boats all weight savings count. On this you safe about 250 grams.

Wouter

There is actually a trick behind these adjuster and their use on the boat.

In order to allow for a quick reraking of the mast you both need to adjust the forestay length as well as side stay lengths.

Typically the forestay has an angle to the mast that is twice the angle that the sidestay make, that is when only looking at the fore-aft plane. This means that in order to rerake your mast without altering the rig tension you need to lengthen the forestay twice as much as the sides !

So the forestay adjuster needs to be twice as long as the ones on the sides. Typically about 200 mm or less. Take note that the forestay is most heavily loaded and the adjuster needs to be beafed to to handle that. Increasing the strip width from 2 mm to 3 mm or 4 mm should be sufficient. The outer strips can remain at 15 x 1 mm. If unsure add a single mm to both and get a 4 mm stick inner strip.

If this forestay adjuster is implemented with 5 mm incrediments then that effectively means that instead of 15 kg, 30 kg, 45 kg, 60 kg , 75 kg and 90 kg adjustments in tension you can fine tune rig tension by steps of 7.5 kg's; simply bye adjusting the forestay adjuster one position up or down. This is because a 5 mm adjustment on the forestay equals 2.5 mm adjustment on the side stay. I already wrote earlier that anything under 3 mm adjustment (on the sidestay) is useless.

Anyway with this the full range of rig tensions becomes :

7.5 kg, 15 kg, 22.5 kg, 30 kg, 37.5 kg, 45 kg, 52.5 kg, 60 kg, 67.5 g, 75 kg, 82.5 kg, 90 kg

= 12 adjustments over the full range of commonly encoutered rig tensions.

So you set the right average level by fine tuning the forestay without adjusting the side stays. from this setting you can adjust only the sidestays to alter rig tension for the conditions, without having to turn a nut through an infinite amount of subpositions to get there. For reraking the mast you just move the forestay up by twice the amount you move the sidestays down.

I found that using the spi pole and halyard are very handy in adjusting the forestay length. Just tie the spi halyards to one another and pull the halyards tight and cleat them. You're mast will be pulled forward and the forestay will start to hang slack. Adjust it. Release the spi halyard from its cleat and move to the side. The first side stay can be adjusted straight away. The second will need someone hanging on the trap line or you have to hook the trap line to your mainsheet system and pull it tight. Now the other one is adjusted. This whole sequence takes less then 30 seconds to complete. Try THAT with a staymaster or turnbuckle. Often you'll need many times more then this just to get the locking nuts to come loose. Note that with the shifted overlap adjuster you can do without any tools in some some cases you can even do it on the water.

This is exactly why I didn't want the staymasters; I'm tired of turning through 20 mm of threading each time I change from sloop to cat rigged and back.

There is another trick.

You can use both quick locking rings (ronstan RF413) or better still toggle pins (ronstan RF115). In these cases you won't be spending much time at all trying to remove the locking ring from the pin. With the locking setup on the adjuster you can safely risk the pin becoming undone so you even can use various "fast pins". No need to argue how much you can speed up the adjustment proces with these. Also on the water adjustment becomes really easy with these. Just have you skipper drive the boat and adjust the stay on the leeward side, tack and do the other side.

It is adviced to use a flattened tube in the forestay adjuster as the jib will be rotating around this when tacking. This cuts down on wear. See an example of a setup like this on a Blade F16 in the picture :





This bring us to the next advantage. This adjuster is very easy to incorporate into the bridle strut setup as used on the F16's.

In addition it is very easy to modify the existing systems as used on Taipans and Blades. These boats have these tube like adjusters already but without the strip that slides inside it. Shortening the stay by 100 mm and adding the strip with the 4 holes is enough to upgrade your existing boats. How many people can not drill 4 holes in a piece of stainless steel ? Or have that done around the corner ?

Cheap, simple, quick, lightweight and effective. And able to be homemade !

What more can you wish for ?


How to make them ? Oh yes.

Well the strip itself should be pretty straight forward. Just don't drill fast in stainless steel. The metal will harden when you drill to fast and you dril bit will go blunt.

The flattened tube can best be made by hammering a round tube of stainless into the required oval shape. This sound a bit crude but it is actually the best way to do it. The tube won't even show many markings. The tube in the following pictures (and the one above) was made in the same way. How does it look ? You can also see the (quick release) toggle pin in this picture






One of the reasons why I like this system. Is that is allows pretty accurate fine tuning of the mast rake and rig tension by adjusting the sidestays and forestay independently from eachother. But once a good average is found then the system allows very rapid adjustment (reraking) over significant incrediments with any need to tools like spanners. In several cases even on the water after conditions have changed. This is something that just can not be had with any staymaster or turnbuckle. Salt and dirt will have no negative effect either on this new system. And personally I dislike using the staymaster where the jib is rubbing against it.

I'm very satisfied with it.

Wouter

Wouter,

Another great post, thanks for sharing the info. This system is very nice!

I'm curious how often you do re-rake? Do you do it for higher vs lower winds or for uni vs sloop, or both? I had heard most people say they generally settle on a single average mast rake and leave it at that for most wind conditions and even uni vs sloop. But I would have to think that re-raking can make a difference. Maybe most people don't do it becuase it's a pain.

By the way, on my dinghy I use the lever shroud adjusters. I'm sure you are familiar with them. They are actually pretty nice. You pop a pin to release the lever and the shroud de-tensions by lengthening slightly so the mast can't fall down. Make a quick adjustment and the lever gives some leverage so you can re-tension without hanging on the trap (unless you want it really tight). Have you ever used these?

Jerry

I don't adjust to conditions often. When in really serious racing I will consider it.

I do readjust when going from sloop to cat rigged and back. About 20 mm, but I'm still experimenting with it. From recreational sailing and recreational racing you can stay with a good average. But when you want to race in an optimal sense then you must rerake your mast when changing from sloop rig to cat-rig. There are gains to be made there. I'm convinced of that.

Wouter

Is that 20 mm measured at the mast head or on the hulls using the trap lines? Or on the chainplates?

20 mm adjustment on my chainplates. My chainplates are 700 mm back from the pivot point of the mast step. If yours are as well on the Blade then these 20 mm on the chainplates will be good starting point for you. However since she is a different design then my Taipan you may end up on a different adjustment eventually.

Wouter