GordMay's linked post covers a lot of it. But there are some other things which you can try too.
But regarding your question, if your spreaders are attached to the mast via a single
, vertical bolt, though them, then yes, a small bit of play is normal. And in spreaders which are more firmly affixed to the mast, to a small degree, they flex & bend, as the mast tune changes. And or when the boat passes through each wave, etc.
They pretty much have to have some range of motion, regardless of their design, or material, as both the rest of the rig, as well as the boat flexes, when any outside force acts upon it, or the rig is tuned. Such as when a racer
cranks on 18" of bend in a mast that's the same length as yours, via a hydraulic backstay. In order to de-power the main.
As to some simple things to try:
- Add some tension to your lowers, so that their tension is on par with the uppers. As 15% in any stay isn't a high load.
- Add another 5% to your backstay too, if you like.
- Lead your topping lift
forward to a strong foredeck fitting, a good bit aft of the stem, & crank on a few hundred pounds of tension.
- Make sure that your furling
line is strong, and, well cleated off. And then crank some tension onto you jib sheets
Or if you don't have a headsail up, have a sailmaker
make you a very strong, flag sized "sail" (normally used to stop racer's headstay foils from fluttering/sailing - tell them this part, & about your problem, when they're taking the order to make it).
Then run it up the headstay, with a halyard
, a stout downhaul, & a "sheet" attached to it. And tension things as you would on a furling
headsail as delineated above.
Also, I don't know if you have a baby stay or not. But most of them are detachable at the deck
level. So if you have one, & yours is, then lead it forward, & tension it a bit.
There are other, more complex "fixes", but really, it's a non-problem. As every mast has it's own particular harmonic frequency. And when the wind
manages to hit it right, then it gets the rig moving, due to this.
But it's not a danger
to your rig, assuming that you have all of your cotter & ring pins properly in place.
Worst case, it might throw your rig a tiny bit out of tune from where it currently is. But even that's unlikely.