DaySailer.org Forum

Took the boat out for my first sail in it. I noticed that whoever installed the spreader brackets did not instal them correctly. The port side spreader is further forward than the starboard side. The port side bracket trailing edge is position 1.75" from the sail track while the starboard side is only 1.0" from the track. Which one is correct, if either?

The general idea with spreaders is to have them positioned so that they push squarely at the mast (and do not have an offset so that there's a sideways load on the fitting). The next idea is that whatever you do, you'd want them symmetric, so that they push evenly and do not try to twist the mast.

If your mast isn't twisted (sail track is straight) then perhaps the difference isn't enough to worry about, or for some reason the curious setup evens out a twist that was in the mast already (well, I think that's a fanciful suggestion myself, but it can't hurt to check the mast both with and without spreaders).

Generally, I'd tend to think that the position should be parallel to a line you draw from the chainplate to the center of the mast. You could work that out with a straightedge on deck, and then you would know where on the mast profile the center of the spreader fitting should be.

Something like that.

Looks like I need to relocate a bracket. Will aluminum rivets suffice or should I use stainless steel?

The brackets will be SS, so if you use aluminum rivets the rivets will be the anode (thing rotting from galvanic corrosion). If you use SS rivets the mast will be the anode. I would think you would go longer without need for maintenance using SS rivets in this scenario.

I used aluminum rivets where SS is not present in other scnarios where I knew the tensile strength did not need to be so strong. If I remember correctly you have roughly around 500lbs resistance/pull with an aluminum rivet.

For instance, my halyards use a plastic pivot block. And the mast and boom castings are aluminumized steel. I used aluminum rivets.

Mast tangs, eye straps, brackets, etc are all stainless steel, so I used SS rivets there. Also, the tangs the shrouds and forestay attach too take on a lot of pressure, so SS rivets were an easy choice there for strength.

In your situation the tension is shifted down on the bracket vs a pull out away from the mast, so your not worried about the strength of the rivet. You just have to pick whether you want the rivet or the mast to be the anode.

If you use the aluminum rivet in that position you would probably be fine for many years though.

I use an insulating compound, TefGel, when joining dissimilar metals.

As Greenlake mentions, in that particular location you should coat the rivet whether you use SS or aluminum. You have dissimilar metals touching either route you go.

Moved my bracket back. But now I'm concerned the spreaders are 'raked' back too far. Looks like they're swept back ar approximately 37 degrees. I have not taken the boat out since the change and I am worried that I won't be able to let the sail out on a broad reach without hitting the spreaders. Can someone confirm the angle that your spreaders are swept?

The spreaders should float horizontally in the swivel bracket attached to the mast. Thus the side stays will auto-magically position the spreaders in the arc around the mast that they should be. On a broad reach, the sail is going to hit the stays (which are attached to the spreaders). I often seem to be hitting the spreaders with the sail on a lesser beam reach, with the tell tails flying back like they should, and I have brand new crisp sails.

Here is a picture that I have... But the one with the sail is the older original sails that came with the boat, not the new ones.

Actually my speaker brackets are not perfectly symmetrical. I can see that one of the spreaders looks a little more cocked forward than the other (starboard side), but that is because the bracket is slightly placed a little more aft on the mast (maybe millimeters). Again at the end of the day, the angle the spreaders sit at is not determined by the bracket but the side stays, so the angles are auto corrected.

Digitalmechanic,

Thanks for the pics. That second one really tells the story. The front edge of my port side bracket was aligned on the center line of the mast. I wasn't really sure if my starboard side bracket should move forward so that it touched the port side bracket; or if the port side bracket should be moved aft. I slid the port side aft and now it looks similar to yours. I will need to raise my mast and check for the 'auto correction' that you mentioned.

I see now. It must have really been off? I would take the mast and draw a line though the middle of it fore and aft, and then starboard and port. Then move to the brackets to the edges of the mast starboard and port from the center point you would have drawn. This should be where your brackets attach. A less technical explanation would be make it the brackets mount as far starboard and port on the mast as possible, the stays will do the rest to align the spreaders. How about this for a 80's computer schematic...

Front of boat
................... _
................. /...\
Bracket-->|....|<-- Bracket
................ \ _ /

Back of boat

As pointed out, the spreaders pivot. They need to be swept back to do part of their job which is to bow the mast forward when there is either vang tention or mainsheet tension. Because dinghies don't have back stays, this is the most practical way to put bow into the mast.

Not just for mast bending. The spreaders are swept back, originally, because they are in line with the shrouds, which are attached aft of the mast. If the shrouds didn't pull back, the mast would bend/fall forward when sailing downwind. The spreaders are used to amplify the sideways pull (as they change the angle of pull where shroud is attached to mast). But, being backswept, the pressure on the spreaders pushes the mast forward a bit (unlike the sideways direction where the two sides oppose and cancel). Together with the pull back at the top that does produce a bit of bending moment (but the backwards pull itself is counteracted rather directly by the forestay.

Luckily, I almost want to write, the net bending from the spreaders turns out to be beneficial.