spreaders

[viago]

does anyone here have any experience of making their own spreaders?
mine need replacing and it seems the originals are simply aluminium tubing with a slot sawn at one end and capped with a nylon stopper. shouldn't the shroud pass through a nylon grommet in the spreader to allow for free running? they dont seem to be very specialist but i guess have done the job for a number of years.
the originals had welded themselves into the stainless root brackets and i cut them off. the brackets seem to be at at around 85 degrees from the upper section of the mast and square to it, is that ok?
the mast is surface mounted and 30' long.

 

[rob2]

Haven't actually done it, but thought I would have to until they freed off with a kettle of boiling water! Just make sure you get the same wall thickness of extruded, anodised tube (not seam welded). If you're like me and start checking for offcuts in the skip, you can't usually see the seam on the outside, but it will show up inside. The ones we were working on didn't have a clamp, but the shrouds had ferrules crimped on below the shrouds to stop them drooping below their correct position (bisecting the angle). It will help prevent future corrosion if you coat inside the socket with insulating paste (damned if I can think of the name at this time of night).

Rob
Waiting for the cat to come home...

 

[VicS]

It will help prevent future corrosion if you coat inside the socket with insulating paste (damned if I can think of the name at this time of night)

"Duralac" the rather messy yellow barium chromate paste or "Tef-Gel" a teflon based paste

 

[William_H]

Spreaders

It does seem like your spreader system simply takes end forces into the mast. Not to be confused with a fractional rig or where the spreaders are angled backwards to provide forward push from the cap shrouds to the middle of the mast.
If Ali tube has been OK in the past then replace with Ali tubing of suitable wall thickness.
Yes the spreader will hopefully be angled slightly up ward to bisect the angle of direction change that the cap shrouds make.This to ensure that the only loading on the tube is truly in column. As said on bigger rigs this is ensured by clamping the cap shroud into the spreader cap so the tip can not slide up or down.
On smaller boats this seems unnecessary and by having the cap shroud free it means you can easily tighten the cap shrouds with out concern about relocating the spreader tip on the wire.
Again on a smaller boat the spreader end can be just slotted for the wire to sit in.Fit a stainless steel bolt through the spreader outboard of the bottom of the slot so the wire will not be able to cut the Ali. Fit a small ss tube over the bolt would to enlarge and smooth the pressure surface.
Fit either another ss bolt at the outside of the slot or use ss locking wire and small holes in the Ali tube to lock the shroud in.
Cap the whole thing with tape or a plastic stool leg cap suitably cut. Or buy a purpose made spreader cap. good luck olewill

 

[merlin3688]

The thickness is very important along with them being anodised. At Sailspar we used to use 10g tube. Plenty of people on Ebay selling just the tube but could not see any anodised, I guess painting is an option? The outer ends were a nylon bung with a slot in the top, the wire was held by wire. The bottom end went in a s/s socket but we fitted rubber tubing to prevent corrosion.

 

[viago]

thanks guys seems pretty hopeful. more to spreaders than i realised. i did try the boiling water trick but to no avail so i used an angle grinder but still have the matter of the remaining welded tube to deal with.

Yes the spreader will hopefully be angled slightly up ward to bisect the angle of direction change that the cap shrouds make.

when people say bisect im hoping you dont mean dividing the stay into 2 equal parts? do you mean that the spreader is at right angles to the stay rather than the mast? would that then naturally "bisect" the angle of directional change needed?
i have been unable to locate a couple of meters of 5000series aluminium which, from what rob and merlin were saying, seems to be the stuff i need. nor standard aluminium anodised. any suggestions?
why is nothing straight forward?

 

[Slycat]

Whatever you do be careful googling for 'spreader bars' like I did !!!

 

[Quandary]

thanks guys seems pretty hopeful. more to spreaders than i realised. i did try the boiling water trick but to no avail so i used an angle grinder but still have the matter of the remaining welded tube to deal with.

when people say bisect im hoping you dont mean dividing the stay into 2 equal parts? do you mean that the spreader is at right angles to the stay rather than the mast? would that then naturally "bisect" the angle of directional change needed?
i have been unable to locate a couple of meters of 5000series aluminium which, from what rob and merlin were saying, seems to be the stuff i need. nor standard aluminium anodised. any suggestions?
why is nothing straight forward?

Ideally the angle between the wire and the spreaders should be equal above and below. (the spreaders will angle upwards) I use a template made with a bit of thin plywood to check them at rig set up each spring, but then my rig is discontinuous which makes it more critical. In any event the angles must be equal and the both ends must be fixed if you are to achieve mechanical efficiency, ie. strength.
Some people have unfixed spreader ends which can slide along the wire, this still contributes some strength to the rig but not much. Triangulation is only really effective when all the sides are of fixed length.
I have a pair of aerofoil section alloy spreader in my garage, from a Sigma 33 that I would be happy to give away but the relatively complex root casting are still on the old mast which when I last saw it was on a spreaderless rig on a catamaran.

 

[viago]

Ideally the angle between the wire and the spreaders should be equal above and below. (the spreaders will angle upwards) I use a template made with a bit of thin plywood to check them at rig set up each spring, but then my rig is discontinuous which makes it more critical. In any event the angles must be equal and the both ends must be fixed if you are to achieve mechanical efficiency, ie. strength.
Some people have unfixed spreader ends which can slide along the wire, this still contributes some strength to the rig but not much. Triangulation is only really effective when all the sides are of fixed length.
I have a pair of aerofoil section alloy spreader in my garage, from a Sigma 33 that I would be happy to give away but the relatively complex root casting are still on the old mast which when I last saw it was on a spreaderless rig on a catamaran.

thanks for the clarification. now the question comes to my mind that the spreaders from a 33ft boat are likely to be longer than those on a 27ft boat, so, is there an optimal length for any given beam of boat and height of mast?
am i right in thinking that the spreader acts to transfer vertical forces to horizontal forces?
just a thought, but would it be bad practice to insert a smaller 10g tube into the existing spreader and root casting? it would save a lot of hassle.

 

[Quandary]

If the spreader is correctly positioned it should be acting purely in compression, however it is hard to avoid some lateral loads particularly in the horizontal plane, for instance when running the mainsail will be leaning on it. What the spreader is doing is turning the rig from a simple pole in to something like a vertical truss. Imagine a plank across a stream, if you put a spreader under it in the middle with a tight wire to each end it no longer bends when you walk across it, your rig is like a vertical version of that. For length the convention now is that the lower part of the shroud is vertical or close to it. The further the wire is from the mast the greater the lateral stiffness of the rig, but you have to consider the sail position so need some compactness. However the longer your spreaders are the stronger and stiffer the tube needs to be. Adding metal to the core is not as effective as a sleeve to the outside, tube stiffness is a condition of diameter provided the wall is not too thin.

 

[Quandary]

Another tuppenceworth,
The root (where the spreader meets the mast) can be a flexible joint, provided that the outer end is securely clamped in position to bisect the angle to the wire, Some movement at the root is desirable in avoiding failure through torsion. The spreader root load should be transferred to the opposite side of the mast, (usually a tube built in) you do not want to put big compression loads on the mast wall alone and the lee spreader root will resist that compression. The length of single spreaders should be something like between 75% and 100% of the horizontal distance of the chainplates from the mast. The wire should be tightened (really tight) before the spreader angle is checked and the ends clamped to the wire.
After I set up my rig I go out in about force 4, put the boat hard on the wind and wind up the bottle screws on the lee side to just take up any slack, tack, do the same, Check tension and straightness and repeat before wiring off the bottle screws.
Many older boats have stiffer and shorter masts so are less dependent on rig tension to maintain straightness. There is lots of advice on tensioning a rig (try Seldens handbook on their website) but the simplest thing is to sight up the mast on a beat and check that it is straight and the top is not curving to leeward.
Try, if possible, to avoid adding too much weight up the mast, it does nothing for performance or motion in a chop.

 

[AngusMcDoon]

EdBeynon just replaced his spreaders on his Hurley 22. I'm sure he'll be along in a bit.

 

[AngusMcDoon]

Whatever you do be careful googling for 'spreader bars' like I did !!!

I couldn't resist that

 

[BruceDanforth]

As Angus says I replaced mine earlier this season and as yet the mast hasn't fallen down. I got the tubing from http://www.tridentuk.com/ in Gateshead, cut it to length with a pipe cutter and re used the old nylon ends from the old spreaders. A drill press helps but these are cheap enough on ebay. I also re used the old stainless brackets for the pennant halyards etc, rivetting them back on with monel rivets. On my 69 hurley 22 the mast sockets were a bit home made so it needed care to mark a spreader for each bracket before drilling the holes. I faffed around for ages until I'd persuaded myself everything was lined up and the shrouds weren't going to be twisted and bought enough pipe to allow myself a second go if I messed up.

 

[William_H]

thanks for the clarification. now the question comes to my mind that the spreaders from a 33ft boat are likely to be longer than those on a 27ft boat, so, is there an optimal length for any given beam of boat and height of mast?
am i right in thinking that the spreader acts to transfer vertical forces to horizontal forces?
just a thought, but would it be bad practice to insert a smaller 10g tube into the existing spreader and root casting? it would save a lot of hassle.

Note that the poster who has those spreaders in his garage said they were airfoil shaped. That is not round and typical of swept back spreaders. The foil shape is larger dimension fore and aft to give stiffness as is necessary. I think you want round tube to match the bases you have.
The spreader is there primarily to improve the angle of the cap shroud to the top of the mast. Without a spreader the wire would arrive at a fairly small angle so give less lateral support to the top. The spreader gives a greater angle to the wire. Of course the spreader does provide some support to the middle of the mast but that point is also supported (located) by your intermediate shrouds and inner forestay.
The decision as to how strong the spreader tube must be is hard to make. Length wall thickness and diameter all contribute to strength. Presumably the 10g tube you have is smaller diameter but this may be made up with thicker walls. It might be safest to assume the original design was minimum strength so don't go for less strength. good luck olewill

 

[viago]

As Angus says I replaced mine earlier this season and as yet the mast hasn't fallen down. I got the tubing from http://www.tridentuk.com/ in Gateshead, cut it to length with a pipe cutter and re used the old nylon ends from the old spreaders. A drill press helps but these are cheap enough on ebay. I also re used the old stainless brackets for the pennant halyards etc, rivetting them back on with monel rivets. On my 69 hurley 22 the mast sockets were a bit home made so it needed care to mark a spreader for each bracket before drilling the holes. I faffed around for ages until I'd persuaded myself everything was lined up and the shrouds weren't going to be twisted and bought enough pipe to allow myself a second go if I messed up.

thanks ed, mine too are home made and i guess at the lower end of the necessary strength range. however the 3.25mm thick metal was much harder to cut than my 5mm aluminium scaffold poles so im guessing its some kind of alloy. it is 1 1/4" in diameter with an internal diameter of 15mm. i could use a couple of 10" x 15mm aluminium bars to bridge the cut. do you remember what the spreader bar dimensions are on your 22?

quandry thanks, how do you get up the stay to fix the wire either side of the spreader with the mast up? seems like a death defying feat to me.
i think that i may need to lengthen the spreader to achieve a near vertical travel from chain plate to spreader. that should be no problem if i fix the spreader further down the bridging bar.
as a matter of interest, if, having achieved the angle of bisection one lengthened the spreader, assuming that the spreader meets the stay around centre of its length, would the angle remain bisected?
(geometry still a mystery to me)

 

[Quandary]

quandry thanks, how do you get up the stay to fix the wire either side of the spreader with the mast up? seems like a death defying feat to me.
i think that i may need to lengthen the spreader to achieve a near vertical travel from chain plate to spreader. that should be no problem if i fix the spreader further down the bridging bar.
as a matter of interest, if, having achieved the angle of bisection one lengthened the spreader, assuming that the spreader meets the stay around centre of its length, would the angle remain bisected?
(geometry still a mystery to me)

My wife winds me up on the main halyard in a bosuns chair, on my rig I have bottle screws to adjust up there too. (I used to have a fear of heights until we had a spinnaker jamb aloft one stormy night and it was either go up there or write some big cheques, after that I usually quite enjoy it) Do not make the spreaders longer than the old ones, keep them the same or you will need longer stays. The angle to the wire above and below does not have to be absolutely the same though in an ideal world it would be, however if the two spreaders are not at the same angle it will be very obvious and every yachtie you meet will be telling you about it. Similarly if your spreaders were not fixed to the wire before you will get away with a similar arrangement as long as the root arrangement is stiff. If you do need to secure the outer end a machine screw with a nice smooth head through a hole across the slot will allow you to clamp it but wind some tape over the nut at the back to combat chafe on sails. I suspect your mast has more strength in reserve than some so you should get away with less efficient triangulation. I do not entirely agree with the proposition that the spreaders are just there to widen the angle of the shroud to the masthead, though it is perhaps a bit more true on single spreader rigs with heavy mast sections. On two or three spreader rigs the tension and compression in every component contributes to stiffness and lightness.

 

[BruceDanforth]

thanks ed, mine too are home made and i guess at the lower end of the necessary strength range. however the 3.25mm thick metal was much harder to cut than my 5mm aluminium scaffold poles so im guessing its some kind of alloy. it is 1 1/4" in diameter with an internal diameter of 15mm. i could use a couple of 10" x 15mm aluminium bars to bridge the cut. do you remember what the spreader bar dimensions are on your 22?

quandry thanks, how do you get up the stay to fix the wire either side of the spreader with the mast up? seems like a death defying feat to me.
i think that i may need to lengthen the spreader to achieve a near vertical travel from chain plate to spreader. that should be no problem if i fix the spreader further down the bridging bar.
as a matter of interest, if, having achieved the angle of bisection one lengthened the spreader, assuming that the spreader meets the stay around centre of its length, would the angle remain bisected?
(geometry still a mystery to me)

The tubing was 1 inch and seemed pretty tough to cut. I'm not sure of the length I just measured them up to the old ones. The wall thickness looked to be the same as the old stuff but then it was bought from a chandlery, sold for making spars.

 

[William_H]

Spreaders

thanks ed, mine too are home made and i guess at the lower end of the necessary strength range. however the 3.25mm thick metal was much harder to cut than my 5mm aluminium scaffold poles so im guessing its some kind of alloy. it is 1 1/4" in diameter with an internal diameter of 15mm. i could use a couple of 10" x 15mm aluminium bars to bridge the cut. do you remember what the spreader bar dimensions are on your 22?

quandry thanks, how do you get up the stay to fix the wire either side of the spreader with the mast up? seems like a death defying feat to me.
i think that i may need to lengthen the spreader to achieve a near vertical travel from chain plate to spreader. that should be no problem if i fix the spreader further down the bridging bar.
as a matter of interest, if, having achieved the angle of bisection one lengthened the spreader, assuming that the spreader meets the stay around centre of its length, would the angle remain bisected?
(geometry still a mystery to me)

My guess is that your boat is relatively small and the mast is quite robust for the boat size. This is hugely different to the huge masts on big boats engineered to best standards for lightest mast.
So I don't think it of great concern about setting the spreader angle upwards to bisect the wire angle. Just use the spreader sockets and the angle that they provide unless you have to have new sockets.
Similarly the spacer or spreader bar inside the mast is not necessary on smaller masts as the walls are quite robust for the boat size. Again be lead by the original set up.
Likewise if the wire was not clamped to the spreader tip in any way then that is not necessary either. Certainly mine on a 27ft mast on fractional rig is free to slide to its natural position. I would not want to be getting up to the spreader tip on a small boat just to clamp the shroud. Do make sure it can not escape from the slot and cover it with padding or insulation tape. (All assuming it is a small boat) olewill